he ne LE Am ah he nn A alana, Huhn end en al ni eh RCIP CIC ER PET EC PCT EN HR ER EN, at ne eis ana EUR OPA RS CA 1s Be wip tare CON An Th A Para Det vo REN SI re u tue an 4 CES) APCE PL TEE CET En CCC CPP nr ame = heme ae AAO EN eee Are Sow EEE LU à ER ba = ~ An, : FAA PAS à 8 laa DS Paleontological Research ISSN 1342-8144 Formerly Transactions and Proceedings of the Palaeontological Society of Japan Vol. 5 No.1 April 2001 The Palaeontological Society of Japan + : Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Jan Bergström (Swedish Museum of Natural History, Stockholm, Sweden), Alan G. Beu (Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato (Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto University, Kyoto, Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain), Roger D.K. Thomas (Franklin and Marshall College, Lancaster, USA), Katsumi Ueno (Fukuoka University, Fukuoka, Japan), Wang Hongzhen (China University of Geosciences, Beijing, China), Yang Seong Young (Kyungpook National University, Taegu, Korea) Officers for 1999-2000 President: Kei Mori Councillors: Kiyotaka Chinzei, Takashi Hamada, Yoshikazu Hasegawa, Itaru Hayami, Hiromichi Hirano, Noriyuki Ikeya, Junji Itoigawa, Tomoki Kase, Hiroshi Kitazato, Itaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Hiroshi Noda, Ikuwo Obata, Kenshiro Ogasawara, Terufumi Ohno, Tatsuo Oji, Tomowo Ozawa, Yukimitsu Tomida, Tsunemasa Saito, Takeshi Setoguchi, Kazushige Tanabe, Akira Yao Members of Standing Committee: Hiroshi Kitazato (General Affairs), Tatsuo Oji (Liaison Officer), Makoto Manabe (Finance), Kazushige Tanabe (Editor in Chief, PR), Tomoki Kase (Co-Editor, PR), Ryuichi Majima (Planning), Hiromichi Hirano (Membership), Kenshiro Ogasawara (Foreign Affairs), Haruyoshi Maeda (Publicity Officer), Noriyuki Ikeya (Editor, "Fossils"), Yukimitsu Tomida (Editor in Chief, Special Papers), Tamiko Ohana (Representative, Union of Natural History Societies). Secretaries: Masanori Shimamoto, Takao Ubukata (General Affairs), Hajime Taru (Planning), Tokuji Mitsugi (Membership), Shuko Adachi (Foreign Affairs), Kazuyoshi Endo, Yasunari Shigeta, Takenori Sasaki (Editors of PR), Akira Tsukagoshi (Editor of "Fossils"), Naoki Kohno (Editor of Special Papers), Hidenori Tanaka (Publicity officer) Auditor: Nobuhiro Kotake Notice about photocopying: !n order to photocopy any work from this publication, you or your organization must obtain permission from the following organization which has been delegated for copyright for clearance by the copyright owner of this publication. Except in the USA, Japan Academic Association for Copyright Clearance (JAACC), 41-6 Akasaka 9- chome, Minato-ku, Tokyo 107-0052, Japan. Phone: 81-3-3475-5618, Fax: 81-3-3475-5619, E-mail: kammori@msh.biglobe.ac.jp In the USA, Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. Phone: (978)750-8400, Fax: (978)750-4744, www.copyright.com Cover: Idealized sketch of Nipponites mirabilis Yabe, a Late Cretaceous (Turonian) nostoceratid ammonite. Various reconstructions of the mode of life of this species have been proposed, because of its curiously meandering shell form (after T. Okamoto, 1988). All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16-9, Bunkyo-ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp/palaeont/ Paleontological Research, vol. 5, no. 1, pp. 1, April 30, 2001 © by the Palaeontological Society of Japan Morphological approaches in paleobiology This special issue is partly based on the workshop of the Palaeontological Society of Japan on “Fossils and Mor- phology” held at the Misaki Marine Biological Station, University of Tokyo, in Miura City, Japan, from April 21 to 24, 2000. The workshop particularly focused on morphological approaches to paleobiological studies, from both fundamen- tal and practical points of view. Most of the 34 participants of the workshop were young paleontologists interested in morphology. Research on organic evolution over the Earth’s history necessarily depends on the morphology of hard tissues pre- served as fossils. Many paleontologists have developed and refined various methodologies for handling the raw mor- phological data presented by fossils and related extant or- ganisms. However, there has been little reciprocal interaction or feedback in this process. For instance, the skills of an expert in comparative anatomy and the compli- cated methods handled by a specialist in mathematical mor- phology are still too far apart from each other. It would seem to be an important goal to make a wide variety of mor- phological methods accessible to all paleontologists, particu- larly younger ones. The workshop setting made it possible to examine the morphological aspects of fossils from a number of view- points and provided an opportunity for young paleontologists to learn various methods in morphology. Most major topics concerning morphology, such as functional morphology, constructional morphology, morphometrics, biometry, theo- retical morphology, developmental constraints, developmen- tal genetics, heterochrony, cladistics, comparative anatomy, histology, biomineralization, etc., were covered. Topics in- cluded current research on various zoophyla, such as molluscs, arthropods, echinoderms and vertebrates, but there were also abstract discussions of methodology or prin- ciple that did not deal with particular groups of organisms. We did not attempt to construct a synthesis of those diverse topics. However, the workshop seems to have succeeded in addressing why so many morphological methods are valu- able for paleobiology. In consequence, the workshop was also a good occasion on which to plan a special issue of Paleontological Research on the use of morphology in paleobiology. The present issue partly reflects the activities at the workshop but does not aspire to represent the complete proceedings. The six contributions offered herein cover only a part of the topics presented at Miura. Among the senior authors of this issue, Enrico Savazzi, Takenori Sasaki and Takao Ubukata pre- sented their papers in the workshop, and Richard Reyment and Kazushige Tanabe were welcome additions to the con- tributors to this special issue. All contributions in this issue underwent the regular review and editing process of the (JUL 12 2001 > LIBRARIES _ journal. In addition, several papers:which were prepared for this special issue but did not complete the review process in time will be treated as regular submissions. This collection is diverse, to the extent that perhaps there is no coherent theme. It covers specialized topics such as the morphometrics of ammonites, morphodynamics of an endolithic gastropod, macrosymbiosis in bivalves, early shell morphology of ammonoids, comparative anatomy of gastro- pods, and the theoretical morphology of bivalve shell struc- ture. Although the papers contained in this issue differ in scope, each touches on the phylogenetic, functional and/or morphogenetic aspects of an organic form. These three as- pects may be conceived of as the parameters of a Seilacher's triangle of constructional morphology, in which organic form is postulated to result from the interplay of the three factors. An integrated approach focusing on several aspects of organic form is becoming more and more impor- tant as paleobiological researches broaden out to include subjects of evolutionary biology. This issue will serve as a benchmark of the present state of this field and indicate lines of inquiry for future research to follow. It should be noted that most of the approaches in the pa- pers contained in this special issue were based on handy, “low-tech” methods such as observation or mathematical analysis, and required neither cutting-edge high technology nor the supporting framework of a large project. This col- lection indicates that morphology based on simple and eco- nomical techniques remains an exciting and creative field of science. This fact should encourage the young paleontolo- gist who might feel that his or her work is mere handicraft in comparison to what colleagues who participate in large- scale projects in fashionable high-tech fields are doing. | hope that the topics presented here will be of interest to all paleontologists, and that this special issue will awaken the interest of many students in the field of morphology. | be- lieve that new approaches to morphological studies will play a key role in paleontology in the 21st century. | thank Tomoki Kase and Kazushige Tanabe, co-editors of Paleontological Research, for their help in the course of the editorial process of this issue. Thanks are also due to Rihito Morita for his cooperation in organizing the workshop, to the staff of Misaki Marine Biological Station for their kind hospitality during the workshop, to all participants in the workshop for their active and valuable discussions, and to all of the authors for their thoughtful contributions to this special issue. Although this is only the first time that Paleontological Research has collected papers on a specialized theme, | hope it will not be an isolated instance but the first of many to come. —TAKAO UBUKATA JANUARY 15, 2001 LT oe éd . en : en Loney oo, 2 y. > = > + cut = Mi ay |e L | u 7 13 F 46 Ù née ve (AY. gal DEL Hat head MR ze aaa ee Pr. aide. NON tu orbite cf em: 7 . #10 a er a ae) avoit dot Stews Tye sliaeglt vs N ue! 4 +e) ich! f er) Ni EN PE 4 rar | u > UE. Met Meg j “ei À “sh - 4 ? we hrs Fab ren a “« Bere "oy a. = ee ell ak Tie 18 an QO Omi ; - Vy Te OMT SUET RE 5 5 SA Che bel A ES à Paleontological Research, vol. 5, no. 1, pp. 3-11, April 30, 2001 © by the Palaeontological Society of Japan Morphodynamics of an endolithic vermetid gastropod Enrico Savazzi Hagelgränd 8, S-75646 Uppsala, Sweden. (e-mail: enrico.savazzi@usa.net) Received 29 May 2999; Revised manuscript accepted 15 November 2000 Abstract. In coiled mollusc shells, the apex typically is located near the centre of a whorl spiral and the aperture at its outer perimeter (exceptions do occur in molluscs with determinate or peri- odic growth, but they do not invalidate this general principle). This geometry satisfies simple growth and functional requirements. The Recent vermetid Dendropomasp. defies these require- ments with its inside-out shell geometry, in which the aperture is located along the axis of the spiral and earlier whorls coil around it. In addition, this species is unique among the Vermetidae in being fully endolithic in the adult, and is one of very few endolithic molluscs with the shell cemented to the substrate during growth. While Dendropoma is typically semi-endolithic, several species ap- pear to have secondarily returned to epifaunal coiling as a response to crowding of the substrate. In D. sp., this was prevented by the immediate environment, subjected to a high rate of erosion. This is likely the factor that triggered the onset of endolithic coiling into the substrate. The change from a semi-endolithic to a fully endolithic life habit in this form was probably sudden, since the preadaptations of Dendropoma prevent a functioning intermediate stage. Key words: endolithic, evolution, functional morphology, Gastropoda, Mollusca, Vermetidae. Introduction In the adult stage, almost all vermetid gastropods are ce- mented by the shell to a solid substrate (Morton, 1955, 1965; Keen and Morton, 1960; Keen, 1961; Savazzi, 1996, 1999a, and references therein). As a consequence of this habit, vermetid shells are irregularly coiled or lose all traces of coil- ing in the adult stage (above references, and below). Most vermetids remove a small amount of material from calcare- ous substrates before cementing the growing shell margin to it (Savazzi, 1996, and therein). This has the apparent adaptive value of removing superficial layers weakened by encrusting organisms and microborers, and of improving the adhesion between shell and substrate. Observation on free-living gastropods with regularly coiled shells shows that a comparable phenomenon, consisting of a secondary re- moval of periostracum and a thin outermost layer of shell material, is common at the junction between adjacent whorls. In the latter case, this phenomenon likely enhances adhesion between successive shell whorls. It is reasonable to suppose that removal of the superficial layer of substrate in vermetids may have evolved from the latter, widespread feature (Savazzi, 1996). It is not known in detail how this process is carried out by vermetids, but, as in most in- stances of secondary shell resorption in molluscs, the proc- ess is likely of a chemical, rather than mechanical nature. A few vermetids remove a larger amount of substrate, and excavate a trench sunk into the surface of the substrate, into which subsequently they secrete their shells. This trait is particularly developed in the genus Dendropoma, which can be characterised as semi-endolithic because a substantial portion of the shell lies below the original surface of the sub- strate (Keen and Morton, 1960; Keen, 1961; Savazzi, 1996, 1999a; references therein, and below). In several species of this genus, the shell cavity is covered by a thickened “roof’ of shell material, level with or slightly projecting from the surface of the substrate (Figures 1A, 2, and below). This paper discusses the adaptations and evolution of a Recent species -or ecomorph -of Dendropoma with a unique combination of morphologic and ontogenetic characters. The taxonomic position of this form, and whether or not its adaptations and morphology warrant the introduction of a new supraspecific taxon, are discussed summarily, but a de- cision on these matters is not taken. This organism is hereby referred to as Dendropoma sp. because its closest affinities are clearly with this genus. This form differs from typical species of Dendropoma in that its adult shell is com- pletely embedded in the substrate, except for the shell open- ing (see below). This habit can be characterised as fully endolithic, as opposed to the semi-endolithic habit typical of this genus (see above, and below). It is unique among vermetids. In order to appreciate the unique character of the shell ge- ometry in Dendropoma sp., it is useful to review the principal geometric properties of shells that grow by marginal accre- tion. Coiled mollusc shells typically have the apex located on the axis of a planispiral or helicospiral formed by later whorls. The aperture, on the other hand, is located at the Enrico Savazzi Figure 1. Exterior view of substrate (B-D) and view of aperture and internal shell cavity seen from below the surface of the substrate (E-G). C,E:x4;D, G: x 6. outer periphery of the spiral. This geometry satisfies simple functional and ontogenetic requirements: it allows continued growth, since earlier shell portions are not in the way of fur- ther growth, and yields a relatively compact shell geometry (compatibly with accretionary shell growth). Exceptions to this rule are known, but they do not invalidate the general principle. These exceptions are typically associated with a A. Dendropoma annulatum, Harrington Sound, Bermuda, x 2. B-G. Dendropoma sp., Hilotongan Island, the Philippines. B: x 2; “count-down” growth process (Seilacher and Gunji, 1993), in which further shell growth is impossible. This growth proc- ess is characterised by “preparatory” morphological changes that precede the attainment of the adult size and the cessa- tion of further growth. For instance, several land snails bring the adult aperture close to the coiling axis in the adult stage, and a few bend the aperture back toward the apex, or Morphodynamics of vermetid gastropod direction of secretion direction of etching latest growth increment substrate to be etched next Figure 2. Schematic section through apertural region of typi- cal semi-endolithic Dendropoma. The surface of the substrate is at the top. The shell cavity has been cut longitudinally through a plane perpendicular to the surface of the substrate and bisecting the shell aperture (the original outline of the aperture is indicated by a dashed line). Note the growth lines on the surface of the shell “roof’ and within its structure. Arrows indicate the direction of migration of the aperture along the surface of the substrate during growth, caused by the twin processes of substrate etching (stippled area) and shell secretion (cross-hatched area). away from it (e.g., Paul, 1999, and references therein). The same principle applies to several heteromorphic ammonoids with count-down shell geometries. A few gastropods (e.g., Distorsio), avoid this problem by returning periodically to a more conventional geometry of the last shell whorl, thus al- lowing the repetition of the count-down process. Dendropoma sp., instead, seems to defy the laws of shell geometry and growth by keeping the apertural region of the shell located at the centre of the whorl spiral, and earlier whorls coiled around it (see below) throughout its adult stage, while at the same time extending the length of its shell and increasing its depth within the substrate. Material and methods The species described in this paper is abundant (Figure 1B) in a band extending from high water mark to about 1 m below it on a rocky shore on the east coast of Hilotongan Island, the Philippines (123° 59° 10”E, 10° 12° 50°°N, as measured on Philippine government maps). Population density exceeds 30,000 adult individuals per m” in the dens- est patches. The surface of the substrate is inclined to the vertical and relatively even. The substrate is a Quaternary, coarse-grained, poorly sorted and somewhat recrystallised biogenic calcirudite, containing occasional large bioclasts (mostly fossil scleractinians). Other areas of this island, as well as most of the nearby islands, were visited repeatedly by the writer, but this species was not observed elsewhere. Samples of the substrate containing the endolithic vermetid were fixed in dilute buffered formaldehyde and sub- sequently kept in 5% ethanol. The substrate was bathed in dilute chlorine and mechanically scrubbed to remove adher- ent algae prior to drying for observation and photography. Morphology and development of Dendropoma In order to appreciate the affinities of Dendropoma sp. with other representatives of this genus, as well as the unique characters of this form, it is necessary to discuss the life habits and morphology of typical Dendropoma species. Sexes are separate. Female individuals of Dendropoma house a small number of large embryos within the mantle cavity (Keen, 1960; Hughes, 1978). A veliger stage is absent, and the juvenile passes through a crawling stage be- fore cementing to the substrate. Dispersion of juveniles may be facilitated by wave or current action, aided by the se- cretion of a mucus thread that retards sinking. However, the sinking rate of juveniles is too high to regard passively transported juveniles as planktonic (Hughes, 1978). Typically, the unattached juvenile shell is trochospiral, brown in colour, and consists of about two whorls. As in other vermetids (above references), the juvenile shell initially becomes cemented to the substrate by its outer lip. Subsequent shell growth continues along a regular helicospiral trajectory, and lifts the aperture away from the substrate. At this point, the aperture bends toward the apex and reattaches to the substrate by its dorsal region. Shortly afterwards, the mollusc starts partially to sink the shell within the substrate, by eroding the substrate in the region adjacent to the aperture (Savazzi, 1996, 1999a, and references therein). In adult Dendropoma (except for the form in question), two shell geometries and modes of growth are represented. In the first, which is exclusive to this genus, the shell follows an irregular path on the substrate, partly sunk within its surface (Figure 1A; Keen and Morton, 1960; Keen, 1961; Hadfield et. al., 1972; Savazzi, 1996). Because of the recessed po- sition of the shell within the substrate, the body whorl is bent outward at an angle of roughly 90° in the region near the ap- erture, so the plane of the aperture is parallel to the surface of the substrate and perpendicular to the growth direction of the shell (Figures 1A, 2). As a consequence, the aperture moves sideways during growth. Shell secretion takes place along half of the perimeter of the aperture, while erosion of the substrate takes place simultaneously along the other half (Figure 2). The exposed portion of the shell constitutes a “roof’ flush with or slightly projecting from the surrounding substrate. Earlier positions of the aperture remain visible as coarse, falcate growth rugae on this roof (Figures 1A, 1C, 3A). The morphology of this relief-pattern is used as a taxo- 6 Enrico Savazzi Figure 3. Juvenile shell showing initial cementation scar (A) and adult operculum in interior view (B) and schematic cross-section (C-D) of Dendropoma sp. Scale bars represent .5 mm. nomic character at the species level. This mode of growth is common among immature individuals of most species of Dendropoma, and in the adult stage of solitary species and morphs. The second mode of growth in this genus consists of piling successive whorls on top of each other, forming an irregu- larly coiled helicospiral shell. This mode of growth is well represented in other vermetid genera, such as Serpulorbis, Tripsycha and Petaloconchus (e.g., Keen, 1961; Savazzi, 1996, 1999a). In Dendropoma, this morphology is frequent in gregarious species and on crowded substrates. In the adult stage, vermetids exhibit dextral coiling, or no coiling at all (above references). Since the adult shell por- tion is cemented to the substrate, or to earlier whorls, by its dorsal surface (see above), the whorls coil in the counter- clockwise direction when viewed from above. Sharp bends of the shell in a sinistral (i.e., clockwise) direction are uncom- mon, and vermetids generally do not exhibit the meandering in alternate directions which is frequently seen in cemented serpulid polychaetes. As discussed by Savazzi (1996), sinistral bending in the Vermetidae is probably prevented by the laterally asymmetrical placement of the columellar mus- cle. Dendropoma possesses a corneous operculum, the mor- phology of which is used as a species-level taxonomic char- acter (Keen and Morton, 1960; Keen, 1961; Morton, 1965; Hadfield et al., 1972). Common to all species of Dendro- poma is a secondarily thickened central portion of the operculum, forming an inward projecting boss or elongated “handle” (above references, and below). Several species of Dendropoma, as other vermetids, are gregarious and form exclusive or olygotypic associations in the intertidal and shallow subtidal zones, sometimes building small reefs (Keen and Morton, 1960; Keen, 1961; Kempf and Laborel, 1968; Hadfield et al., 1972; Hughes, 1978, and personal observations). Morphology and growth of Dendropoma sp. Larval and juvenile development Females incubate few (from 6 to 12) large eggs within the mantle cavity. Mature embryos contain a well developed protoconch consisting of approximately 2 whorls. This shell is translucent, smooth when observed under a dissection mi- croscope, and brown-coloured. Samples of the substrate inhabited by adults of this spe- cies were found to harbour numerous juvenile specimens, usually nested in small crevices. As typical of vermetids (above references), juveniles first cement to the substrate by the outer shell lip. Immediately afterwards, the shell bends in the apical direction, usually lifting free of the substrate, and subsequently reattaches to the substrate by the (homologically) adapical surface of the whorl. The size of the shell in the smallest attached juveniles is comparable to that of the largest larval shells. Therefore, a veliger stage is apparently lacking. This agrees with obser- vations on other species of Dendropoma (see above refer- ences). Immature shell At this stage, the shell is light brown to white with occa- sional brown patches (especially on its interior surface), car- ries coarse falcate ridges on its exposed surface, and is slightly sunk within the substrate. Except for the rather small size of D. sp., young specimens (central portion of Figure 1B) are essentially identical, in general appearance, to the adult stages of several other species of Dendropoma (e.g., Figure 1A). Some of the individuals of D. sp. afterwards continue to wander in an apparently random fashion during growth, per- haps as a response to a crowded or irregular substrate. Most of the individuals, however, after an irregular early stage build an evenly curved, counterclockwise arch (Sur- rounding the adult shell aperture of several individuals in Figure 1D). The radius of this arch, which gradually ex- tends to one full whorl, is rather constant in length among different individuals, and the free space enclosed within the arch has a diameter comparable to that of the adult shell ap- erture. While building this arch, the apertural region of the shell becomes gradually embedded deeper within the sub- strate, thanks to a gradual increase in etching activity. Earlier portions of the body whorl do not change their posi- tion relative to the substrate. Adult shell Upon reaching one whole, broadly umbilicate whorl, the apertural portion of the shell, instead of rising onto and over- lapping the earlier portion of the whorl as in other vermetids Morphodynamics of vermetid gastropod 7 (see above), dips beneath it and into the substrate. At the same time, the shell aperture bends toward the umbilicus, thus avoiding the erosion of earlier portions of the arch. It is convenient to characterise these events as the beginning of the adult growth stage of the shell, although they may have no connection with reproductive maturity. From this moment onward, the shell aperture opens within the umbilicus (Figure 1D-G). Further growth continues in the same fashion, with subsequent whorls becoming embed- ded deeper within the substrate, and the aperture located at the bottom of an umbilical well surrounded by earlier whorls (Figures 1C-G, 5). As a result, the shell is coiled in an ap- parently sinistral fashion. However, since the shell initially attaches to the substrate by the adapical side of the whorl, this coiling geometry is not sinistral, but hyperstrophic dex- tral. Substrate-etching continues to take place within the aper- ture, which revolves around its axis and moves deeper within the umbilical well. This results in the formation of a pattern of spiralling ridges on the walls of the umbilical well (Figure 1D, bottom of Figure 1C, centre of Figure 5A). These ridges are homologous to the falcate ridges on the exposed surface of the shell in semi-endolithic species of Dendropoma. The largest individuals of D. sp. display an internal shell cavity consisting of about two whorls. The earliest, most superficial of the preserved shell whorls are commonly eroded (Figure 1C), with the shell cavity exposed and closed off by internal septa (rightmost portion of Figure 1D). Thus, this portion of the shell is gradually vacated and sealed off by the mollusc. In some specimens, judging from the diameter of the shell cavity, at least one or two additional whorls were originally present, and were destroyed by rapid erosion of the substrate. This is further supported by the frequent occurrence of radular scratch marks on the surface of the substrate (probably caused by chitons and archaeogastropods, which are both frequent in crevices and sheltered areas), and by a general lack of cemented epifauna. Operculum The operculum (Figure 3B-D) is corneous, white with red- dish-brown periphery and nucleus. It is variable in general shape, with the outer surface slightly concave to highly domed (Figure 3C-D), carrying irregular concentric ridges but no visible spiral ornamentation. The perimeter consists of a thin lamina surrounding a thickened and bulging ring (Figure 3B-D), which, unlike the rest of the outer surface, is smooth and shiny. The inner surface of the operculum is smoother and carries an elongated axial “handle” (Figure 3C-D) and a semicircular or horseshoe-shaped dark patch near the basis of the handle (Figure 3B). Soft parts The general appearance of the body (Figure 4) is consis- tent with that of other species of Dendropoma (above refer- ences). The body is rather short, with a well developed columellar muscle. The mantle is slitted in the female, whole in the male. The pedal and cephalic tentacles ap- pear to be rather short. A detailed anatomical investigation was not carried out. operculum cephalic tentacles pedal Lash tentacles foot mantle columellar muscle Figure 4. in lateral view. Soft parts and operculum of male Dendropoma sp., Scale bar represents 5 mm. Affinities The anatomy of the soft parts, morphology of the operculum and general shell characteristics (above, and Figures 1, 3-5) show this species to be a member of the vermetid genus Dendropoma Morch, 1861 (see also Keen, 1961). The gregarious habits and morphology of the operculum are consistent with placement in the subgenus Novastoa Finlay, 1927. However, as noted by Keen (1961) this subgenus may be artificial. Furthermore, D. sp. is con- spicuously different from all other Dendropoma in its shell geometry, mode of growth and endolithic habit. These dif- ferences are at least as important as those on which the ex- isting subgenera of Dendropoma (i.e., Dendropoma s.s., Novastoa and Elliptovermetus Cossmann and Peyrot, 1922) are based. If future observations show that the shell mor- phology and life habits of D. sp. as described in this paper are a constant feature of this species, rather than an ecotypic response to a particular environment, it might be justified to erect a new subgenus to accommodate its unique character. However, a review of Dendropoma from the Philippines would be necessary to settle the problems con- nected with the specific and subgeneric placement of this genus, and such a study lies outside the scope of the pre- sent paper. Evolution The evolution of the endolithic habit in D. sp. cannot be explained as a process characterised by a gradual increase 8 Enrico Savazzi B Figure 5. Internal mould of shell cavity (A) and cross-section through the deepest portion of the shell cavity (B), cut through a plane parallel to the surface of the substrate, in Dendropoma sp. In A, the early portion of the shell cavity is closed off by septa. A sculpture of coarse oblique rugae is visible on the walls of the apertural well (vertical portion of shell cavity located at the centre of the spiral). The shell aperture proper is located at the bottom of the apertural well. in depth of the trench excavated by Dendropoma. This sim- ple mechanism would produce an external roof above the whorls, which is absent in D. sp. As an alternative, one could envision a growth process in which earlier portions of the shell gradually migrate deeper within the substrate during growth, by eroding substrate along one side of the shell cavity and secondarily depositing shell material on the opposite side (i.e., in a manner analo- gous to the sideways ontogenetic migration of the aperture). However, this process would leave telltale growth lines in the shell structure indicating earlier positions of the whorls within the substrate. This situation can be compared with the backwards and/or sideways boring process displayed by endolithic lithophaginid bivalves when they move away from their original position within the substrate. This process leaves meniscus-shaped layers of calcareous material filling the vacated region of the borehole (e.g., see Savazzi, 1999b, fig. 17.2B). Such structures, instead, are absent in D. sp., thus ruling out the above process and showing that the position of earlier shell portions within the substrate does not change. A more unconventional growth mechanism (Figures 5B, 6) explains the observed features. The apertural portion of the shell, which is located at the bottom of the apertural well, grows in the manner typical of Dendropoma, i.e., by etching substrate along half of its circumference, and depositing shell material along the opposite half. However, in D. sp. the shell aperture, instead of migrating along a path parallel to the surface of the substrate, revolves around the bottom of the apertural well. As a result, the aperture rotates and progressively deepens within the substrate, leaving on the walls of the apertural well a set of spiralling, curved ridges homologous to those on the roof of semi-endolithic species (albeit arranged in a different geometric pattern because of the different trajectory of the aperture). At the same time, the rest of the shell cavity becomes coiled around the A B Figure 6. Schematic section through the bottom portion of the shell cavity of Dendropoma sp. along a plane parallel to the surface of the substrate (which is located above the plane of the figure), showing the shell growth process. Substrate erosion takes place along a por- tion of shell cavity in proximity with the apertural well (A). The direction of growth follows a circular trajectory (arrow in B) around the apertural well, gradually moving deeper within the substrate at the same time. This process is recorded by growth lines in the shell wall that surrounds the apertural well (B). Note that, with the exception of the gradual deepening of the apertural well, neither the apertural well nor earlier coiled portions of the shell cavity change their position relative to the substrate during growth. Morphodynamics of vermetid gastropod 9 apertural region because it is connected to the revolving ap- erture by a short bent portion (Figures 5A, 6). As a result, successive whorls are located progressively deeper within the substrate, trailing behind the aperture like a spiral stair- case. Instead of coiling outwards from the surface of the substrate, like regular vermetids, D. sp. coils into the sub- strate. The direction of coiling, however, remains dextral as in epifaunal vermetids. Since in all vermetids the adapical shell surface is cemented to the substrate, the different di- rection of translation of the whorls along the coiling axis in D. sp. results in an inverted direction of translation of the helicospiral. Therefore, the coiling of D. sp. is not sinistral as could appear from a superficial observation, but hyperstrophic dextral (see above). Early portions of the shell cavity are vacated and closed off by septa, and thus the soft parts effectively migrate deeper within the substrate, in spite of the shell being cemented to it. This growth process achieves the combined results of deepening the apertural portion of the shell (which is the only growing shell portion, since earlier shell portions remain immobile with respect to the surrounding substrate) without moving it laterally along the surface of the substrate. In ad- dition, it makes a fully endolithic habit possible without in- creasing substantially the volume of substrate that must be eroded, compared to a semi-endolithic habit. Finally, it achieves these results without requiring substantial changes in the nature of the mechanisms involved in the shell con- struction and growth of Dendropoma. Morphodynamics The evolutionary process that led to this peculiar morphol- ogy and ontogeny remains to be explained. Biological morphodynamics (Seilacher, 1991) is a _ conceptual framework stating that the morphology and evolution of an organism can be understood as the interplay of four factors: function (i.e., all aspects of morphology with a direct adap- tive significance), construction (including morphogenesis, structural materials and building principles), phylogenetic tradition (the evolutionary history, preadaptations and Bauplan; see below) and immediate environment (the char- acteristics of the environment in close proximity with the or- ganism). The Bauplan is a set of constructional “building blocks” and morphologic characters that constitute the shared features of a lineage or taxonomic group (although they may not be expressed in all its members). Morphodynamics is a recent extension of constructional morphology (sensu Seilacher, 1970; an alternative definition of the latter exists, but is not discussed here), which includes only the first three of the above factors. Both morpho- dynamics and constructional morphology were meant as practical frameworks to guide and summarise one’s reason- ing while carrying out an analysis of morphology, not as ab- stract philosophical generalisations. Therefore, the merits of these frameworks should be judged in the context of spe- cific instances of functional analysis, like the present one. In both conceptual frameworks, lateral migration of the shell aperture in typical Dendropoma is the preadaptation that allowed the evolution of the unique ontogenetic mecha- nism of D. sp. The spiral coiling of this species likewise origi- nates from the generic gastropod Bauplan. While adult Dendropoma is facultatively not coiled, its larval shell is obli- gatorily coiled, just as the adult shell in noncemented ances- tors of the Vermetidae was regularly coiled. Spiral shell coiling is still visible in the facultative or obligatory (albeit somewhat irregular) adult coiling of several vermetid genera (Keen, 1961; Savazzi, 1996, 1999a, and therein). Dextral shell coiling is also related to the laterally asymmetric place- ment of the columellar muscle in the Vermetidae (including those that are noncoiled in the adult stage). Thus, it is le- gitimate to state that spiral coiling is part of the vermetid Bauplan. In the present case, morphodynamics may display a prac- tical advantage over constructional morphology. The latter provides an explanation for the morphology of D. sp. in an adaptive context, but does not explain clearly the cause of its evolution. Morphodynamics, instead, offers a better framework for explaining both. The rock substrate inhab- ited by D. sp. is characterised by a high rate of erosion (as evidenced by grazing tracks and by the fact that early por- tions of the shell of this species are often eroded away; Figure 1E-F). Significantly, the only other sessile inverte- brate common in the same substrate is a rock-boring foraminiferan that lives in a shallow pit (dark grey patches in Figure 1F) and continuously deepens it in order to remain protected against erosion (J. Whittaker and E. Savazzi, un- published). It can be noticed also that the substrate is crowded (Figure 1B, E-F). These are the key environ- mental factors to explain the evolution of D. sp. Fast erosion of the substrate encouraged a switch from a semi-endolithic to an endolithic habit, because the latter offers a better protection against erosion, and thereby an en- hanced probability of survival. Most endolithic gastropods and bivalves fight erosion of the substrate by boring deeper within the substrate during growth (e.g., Savazzi, 1999a, 1999b, and references therein). This requires mainly behavioural modifications, rather than morphologic ones, since these molluscs are not cemented to the substrate, can move within their boreholes, and already bore deeper into the substrate during growth, in order to accommodate their ontogenetic increase in size. Dendropoma, instead, is con- strained by shell cementation to the substrate in its possible evolutionary “choices”. Excavation of a deeper trench with a thicker roof (cf. Figure 2) would seem to be a straightforward route into the endolithic habit. However, this solution is not feasible be- cause it involves a substantial increase in the volume of sub- strate that must be removed, and of shell material that must be secreted (i.e., the “roof” of shell material covering the trench). Alternatively, faster horizontal growth along the surface of the substrate, resulting in an increased length of the shell, would also help to fight off erosion by continually moving the organism to fresh areas of the substrate, but like- wise involves an increase in the energy spent boring and se- creting shell material, besides being unfeasible in crowded substrates. In D. sp., a secondary return to coiling avoided these problems, and provided a working solution to seem- ingly contrasting necessities: cementing the organism to the substrate, allowing it to move deeper into the substrate dur- ing growth, not increasing the used surface area of sub- 10 Enrico Savazzi strate, and not increasing the volume of removed substrate substantially, compared with a semi-endolithic habit. The secondary return to coiling in D. sp. confronted this species with a “choice” between two mutually exclusive life habits: epifaunal coiling above the surface of the substrate, or endolithic coiling beneath its surface. No working inter- mediate choices are possible (short of abandoning coiling and reverting to an uncoiled semi-endolithic habit), because this would cause the mollusc to bore into earlier portions of its own shell, still occupied by the soft parts. Thus, the onset of coiling and of fully endolithic habits must have been a sudden evolutionary event, made possible by the facts that coiling was already available in the vermetid Bauplan, and that the accompanying coadaptations did not require the evolution of substantially new morphological or behavioural traits. Alternatively, an intermediate paedomorphic stage, adap- tive in lessening the negative effects of erosion by reducing the life span, may have been involved. Such a stage likely had a life habit comparable to that of juvenile vermetids, and therefore displayed no substantial morphologic innovation. The subsequent return to a larger size forced a switch from epifaunal to endolithic habits and hyperstrophic coiling. Thus, also this alternative process involves a sudden evolu- tionary change. The facts that several species of Dendropoma display fac- ultative or obligatory epifaunal coiling (see above), while all Dendropoma are capable of semi-endolithic boring, suggest an evolutionary scenario in which epifaunal coiling was ini- tially lost in Dendropoma, and subsequently reappeared secondarily multiple times during the evolution of this genus, rather than representing the uninterrupted maintenance of this character from epifaunal ancestors. The factor that “tipped the scales” in favour of endolithic boring in D. sp., in- stead of resulting in yet another instance of parallel evolution of epifaunal coiling, is likely the substrate being subjected to a high rate of wave erosion and/or bioerosion, which makes epifaunally coiled individuals excessively vulnerable. Thus, the immediate environment appears to be the trigger of the evolutionary processes that led to the unique shell morphol- ogy and growth mechanism in D. sp. In turn, the presence of a solid substrate surrounding the organism, which characte- rises the endolithic environment, allowed the evolution of a growth mechanism that would be impossible in an epifaunal organism. To the knowledge of the writer, the clavagellid bivalve Bryopa is the only other boring mollusc that permanently ce- ments the shell (in particular, the left valve) to the substrate without losing the capability of migrating deeper within the substrate during growth (Savazzi, 2000). Bryopa does so by continuously elongating the shell and shifting the position of the soft parts within the left valve, abandoning its early portions. Thus, its adaptations are partly convergent with those of D. sp. Conclusions Dendropoma sp. is unique among vermetids in being fully endolithic in the adult stage. During the juvenile, semi- endolithic stage, it builds a broadly umbilicated whorl partly embedded in the substrate. Subsequently, instead of build- ing successive whorls upward and elevating its shell above the substrate, as in several epifaunal vermetids, it places new whorls deeper within the substrate and underneath ear- lier ones, like a descending spiral staircase. The aperture moves into the shell umbilicus and does not migrate further along the surface of the substrate during growth. Instead, it gradually deepens within an umbilical apertural well. This process results in the formation of a characteristic spiralling pattern of ridges on the walls of the well. While the shell morphology of D. sp., at first sight, appears to violate the fundamental laws of gastropod shell geometry, the adaptiveness and evolution of this morphology can be successfully explained within the framework of biological morphodynamics. The demands posed by a substrate sub- jected to rapid erosion appear to be the factor that triggered the evolution of this form. Its growth mechanism and most of its unique adaptations are related to the sudden change in immediate environment caused by an evolutionary switch from a semi-endolithic to a fully endolithic life habit. This switch was a sudden event, because the preadaptations of Dendropoma allow no feasible intermediate stage between a semi-endolithic and a fully endolithic life habit. Acknowledgments | wish to thank the Japan Society for the Promotion of Science and Prof. Kazushige Tanabe, my host at the University of Tokyo, for a grant that allowed me to write the present paper and to carry out additional research in Japan in April-May, 2000. References Hadfield, M. G., Kay, E. A., Gillette, M. U. and Lloyd, M. C., 1972: The Vermetidae (Mollusca: Gastropoda) of the Hawaiian Islands. Marine Biology, vol. 12, p. 81-98. Hughes, R. N., 1978: Notes on the reproductive strategies of the South African vermetid gastropods Dendropoma corallinaceum and Serpulorbis natalensis. The Veliger, vol. 21, p. 423-427. Keen, A. M., 1960: Vermetid gastropods and marine intertidal zonation. The Veliger, vol. 3, p. 1-2. Keen, M., 1961: A proposed reclassification of the gastropod family Vermetidae. Bulletins of the British Museum (Natural History) Zoology, vol. 7, p. 183-213. Keen, A. M. and Morton, J. E., 1960: Some new African spe- cies of Dendropoma (Vermetidae: Mesogastropoda). Proceedings of the Malacological Society of London, vol. 34, p. 36-51. Kempf, M. and Laborel, J., 1968: Formations de vermets et d’algues calcaires sur les côtes du Brésil. Recueil des Travaux de la Station Marine d’Endoume, vol. 43, p. 9-23. Morton, J. E., 1955: The evolution of vermetid gastro- pods. Pacific Science, vol. 9, p. 3-15. Morton, J. E., 1965: Form and function in the evolution of the Vermetidae. Bulletins of the British Museum (Natural History) Zoology, vol. 11, p. 585-630. Paul, C. R. C., 1999: Terrestrial gastropods. In, Savazzi, E. ed., Functional Morphology of the Invertebrate Skeleton, p. 149-167. Wiley and Sons, Chichester. Savazzi, E., 1996: Adaptations of vermetid and siliquariid gas- tropods. Palaeontology, vol. 39, p. 157-177. Savazzi, E., 1999a: Cemented and embedded gastropods. In, Savazzi, E. ed. Functional Morphology of the Invertebrate Skeleton, p. 183-195. Wiley and Sons, Chichester. Savazzi, E., 1999b: Boring, nestling and tube-dwelling bi- valves. In, Savazzi, E. ed., Functional Morphology of the Invertebrate Skeleton, p. 205-237. Wiley and Sons, Chichester. Savazzi, E., 2000: Morphodynamics of Bryopa and the evolu- tion of clavagellids. Geological Society Special Morphodynamics of vermetid gastropod Publications, no. 177, p. 313-327. Seilacher, A., 1970: Arbeitskonzept zur Konstruktions- Morphologie. Lethaia, vol. 3, p. 393-396. Seilacher, A., 1991: Self-organizing mechanisms in morpho- genesis and evolution. /n, Schmidt-Kittler, N. and Vogel, K. eds, Constructional Morphology and Evolution, p. 251-271. Springer-Verlag, Berlin. Seilacher, A. and Gunji, Y. P., 1993: Morphogenetic count- downs in heteromorph shells. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, vol. 190, p. 237-265. 102 0 er; in ii ee A A eee sperren eb ei, À» sul vii ae CN Drag. À elle. u Ey he NE Par xt { “ fl Ip | em, A ales © eek ptet) ( tbe fg. . Ko Growling Ms sta ate hat ro i ’ BEE ee ET sur, ever hance: A ieee 0 4) ha sthe sel ee je ‘i cubed: vw a wo | jé hi iris (eT) Re & N | ; “2 > Cover ml Lu x \ ; ET N LT. idole 0 et 7 in uchs Mure au LE ih inten ie MI ’ Free vive hues WO d à on b W if LU à at rat PEL cé Mie: ba 7 Paleontological Research, vol. 5, no. 1, pp. 13-19, April 30, 2001 © by the Palaeontological Society of Japan External features of embryonic and early postembryonic shells of a Carboniferous goniatite Vidrioceras from Kansas KAZUSHIGE TANABE’, CYPRIAN KULICKI’, NEIL H. LANDMAN’ and ROYAL H. MAPES* ‘Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Tokyo 113-0033, Japan (e-mail:tanabe @eps.s.u-tokyo.ac.jp) ®Institute of Paleobiology, Polish Academy of Sciences, ul. Twarda 51/55, 00-818 Warsawa, Poland (e-mail: kulicki @ twarda.pan.pl) “Division of Paleontology (Invertebrates), American Museum of Natural History, Central Park West at 79” Street, New York, New York 10024-5192, U.S.A. (e-mail: landman @amnh.org) ‘Department of Geological Sciences, Ohio University, Athens, Ohio 45701, U.S.A. (e-mail: mapes @oak.cats.ohiou.edu) Received 7 August 2000; Revised manuscript accepted 4 December 2000 Abstract. The ornamentation and dorsal wall structure of Vidrioceras (Cycloloboidea, Goniatitina) in the early ontogenetic stage are described on the basis of specimens from the Upper Pennsylvanian in Kansas, USA. The exposed surface of the embryonic shell is smooth, without any trace of ornamentation or growth lines. Regularly spaced lirae abruptly appear on the early postembryonic shell just adoral of the primary constriction. The inner surface of the dorsal wall in the embryonic and early postembryonic stages exhibits a distinct ornament consisting of evenly spaced, longitudinal ridges, which are replaced adorally by the typical wrinkled ornament in the subsequent stage. Our observations are in accord with those of goniatites from the Upper Carboniferous Buckhorn Asphalt of Oklahoma, suggesting that in the Goniatitina, the outer surface of the embryonic shell is smooth. Comparison with the embryonic shell formation of extant Nautilus suggests that in the Goniatitina, the embryonic shell was uniformly secreted by the shell gland on the posterior side of the embryo. Key words: Ammonoidea, Carboniferous, development, embryonic shell, Goniatitina, Kansas, Vidrioceras Introduction The embryonic shell of ammonoids (termed the ammonitella by Druschits and Khiami, 1970) consists of a spherical initial chamber and approximately one subsequent whorl with a thick nacreous swelling (primary varix) at the aperture (for references see Landman et al., 1996). The boundary between embryonic and postembryonic stages is marked by the primary constriction. Most previous studies on the external morphology and microstructure of embryonic shells of the Ammonoidea have been based on Mesozoic material with aragonitic preservation (Druschits and Doguzhaeva, 1981; Bandel, 1982, 1986; Bandel et al., 1982; Landman, 1982, 1985, 1987; Landman and Bandel, 1985; Tanabe, 1989; Kulicki and Doguzhaeva, 1994; Landman et al., in press, among others). In Paleozoic ammonoids, the microstructure of the embryonic shell is rarely preserved in most fossils due to diagenesis, except for aragonitic goniatites studied by Kulicki et al. (in press) from the Carboniferous Buckhorn Asphalt in Oklahoma, USA. Previous authors have indicated that the embryonic shells of Paleozoic ammonoids display ornamentation and features of several internal shell characters different from those of Mesozoic ammonoids (Beecher, 1890; Miller, 1938; House, 1965; Mapes, 1979; Tanabe et al, 1993, 1994; Doguzhaeva, 1996; Landman et al., 1996; Landman et al., 1999; Klofak et al., 1999; Kulicki et al., in press). These studies have revealed a variety in the embryonic shell fea- tures in the Ammonoidea that can be used for higher-level phylogenetic analysis. In this paper, we describe the ornamentation and the dor- sal wall structure of goniatites at the embryonic and early postembryonic stages based on specimens from the Upper Pennsylvanian of Kansas, USA. Furthermore, the result of our observations is compared with data on other ammonoids and extant Nautilus and discussed for its implications for 14 Kazushige Tanabe et al. systematics and embryonic shell formation. Some of the specimens utilized have been studied by Tanabe et al. (1993), but those observations are partly reevaluated in this paper. Material and methods Tanabe et al. (1993) discovered an embryonic ammonoid assemblage in a carbonate concretion recovered from the Virgilian (Upper Pennsylvanian) offshore shale in Pomona, Kansas, USA. These authors classified the embryonic ammonoids into two morphotypes by the difference in the size and shape of their initial chambers, namely into a large and globular and a small and ellipsoidal one. They further assigned these large and small morphotypes to Vidrioceras (Vidrioceratidae, Cycloloboidea) and Aristoceras (Thalassoceratidae, Thalassoceratoidea) respectively, on the basis of comparison with their initial chambers with those of larger specimens of these two genera from the same con- cretion. About one hundred well preserved specimens of the two genera at embryonic and early postembryonic stages were removed without etching from the weathered portion of the concretion by the wet-sieving method. They were coated with platinum and observed by scanning electron micros- copy. Although the embryonic shells of Aristoceras occur more abundantly than those of Vidrioceras, we did not ob- serve early shell features of the former genus because of poor preservation of the dorsal wall sculpture in the available specimens. As already pointed out by Tanabe et al. (1993), the goniatite specimens from Pomona preserve calcified shell material, and the recrystalized condition of their shell wall prevents study of the shell ultrastructure. Our observa- tions are, therefore, mainly restricted to the external features of these specimens. All of the specimens utilized are housed in the University Museum, the University of Tokyo (UMUT). Observations Embryonic shells General morphology and ornamentation. The embry- onic shells of Vidrioceras examined are all globular in overall shape and consist of a spindle-shaped initial chamber and approximately one subsequent planispiral whorl (Figure 1). In median section, a thick nacreous swelling (primary varix) appears on the inner side of the prismatic layer in the apertural region (see Tanabe et al., 1995, figure 2A). The first whorl is much broader than high, covering the greater portion ot the initial chamber (Figures 1, 2). The spiral length of the embryonic shell (=ammonitella angle of Landman et al., 1996) is relatively long, measuring about 360° in median section. The embryonic shell diameter in the specimens examined ranges from approximately 720 um (UMUT PM19872-1; Figure 1.1) to 780 um (UMUT PM19872-3; Figure 1.3a). The exposed surface of the shell at the embryonic stage is smooth without any trace of ornamentation or growth lines (Figure 1). Dorsal wall of the first whorl.— In several embryonic and early postembryonic specimens, part of the first whorl has been lost due to mechanical destruction during the taphonomic process or due to the wet-sieving procedure. In those specimens, evenly spaced longitudinal ridges are visi- ble on the dorsal side of the missing whorl portion (Figures 2.1-2.3, 3.1, 3.2). They never occur on the lateral flanks of the initial chamber that are free from the first whorl. This fact indicates that the longitudinal ridges represent the sculpture on the inside surface of the dorsal wall of the first whorl. A weaker ridge is occasionally intercalated between the longitudinal ridges (Figure 2.3b). Remarks.— Tanabe et al. (1993, fig. 3A) described evenly spaced longitudinal ridges on the ventrolateral side of sev- eral embryonic shells of Vidrioceras from the same locality and interpreted them as the surface ornamentation. However, our reexamination of these and additional speci- mens reveals that the longitudinal ridges are not the surface ornamentation but the microornamentation on the inner side of the dorsal wall, and that the exposed surface of the em- bryonic shell of Vidrioceras is in fact smooth. Early postembryonic shells The embryonic shell margin is easily visible from outside by the presence of the slightly depressed primary constric- tion followed by the sharp apertural edge (see arrows, Figure 1.1, 1.3a). Fine transverse lirae abruptly appear on the adoral side of the primary constriction. They are initially rectiradiate in the early postembryonic stage (Figure 1.1, 1.3a, b), but become prorsiradiate and gently convex at the venter in a later stage. Each lira is asymmetric in cross sec- tion with a steep edge on the adoral side and is gently in- clined adapically (Figure 1.3b). The change of the inner surface sculpture of the dorsal wall is visible in several early postembryonic shells whose body whorl is partly lost secondarily (Figure 2.1-2.3). In one of these specimens, shown in Figure 2.2, the longitudi- nally ridged ornament disappears on the dorsal side of the embryonic shell aperture and a wrinkled ornament similar to a human fingerprint pattern begins to appear on the adoral side of the primary constriction. In the embryonic or early embryonic specimen shown in Figure 2.4, the wrinkled orna- ment already exists on the dorsal side near the shell margin. In another two specimens, shown in Figure 2.1 and 2.3, the longitudinally ridged ornament extends for a half whorl be- yond the primary constriction. These observations clearly indicate that Vidrioceras exhibits some variation in the ontogenetic change of the dorsal wall ornament. Comparison with other ammonoids On the basis of observations on excellently preserved ma- terial from the Pennsylvanian (Desmoinesean) Buckhorn Asphalt in Oklahoma, Kulicki ef a/. (in press) reported that the outer surface of the embryonic shells of goniatites is smooth without any trace of ornamentation or growth lines, as is the case of Vidrioceras described herein. These ob- servations strongly suggest that in the Goniatitina the em- bryonic shell is smooth. Ornamentation on embryonic shells of the Goniatitina dif- fers from those of other ammonoid suborders. In the Devonian Agoniatitina, Anarcestina and Tornoceratina, the Goniatite early shell features 15 Figure 1. Vidriocerassp. 1. Oblique view of early postembryonic specimen showing slightly depressed primary constriction and ad- jacent embryonic shell edge (pointed by an arrow). The embryonic shell is smooth, while the postembryonic shell is sculptured by fine trans- verse lirae. UMUT PM19872-1. 2. Lateral view of embryonic shell with smooth surface. UMUT PM19872-2. 3a, b. UMUT PM19872-3. Lateral view of early postemebryonic shell showing abrupt appearance of fine transverse lirae after primary constriction (pointed out by an arrow) (3a) and close-up of lirae (3b). Scale bars: 100 pm (1, 2, 3a) and 10 um (3b) embryonic shells are characterized by fine transverse lirae parallel to the aperture (Beecher, 1890; Miller, 1938; House, 1965; Landman et al., 1996; Klofak et a/., 1999). In the un- coiled Late Silurian and Devonian Bactritina and partly coiled Devonian ammonoids, the straight whorl after the ini- tial chamber is also covered with transverse lirae (Erben, 1964). Mapes (1979) reported both smooth and longitudi- nal ornament on the initial subspherical chamber and early shaft of “bactritids” from the Carboniferous, and Mapes (1979) and Doguzhaeva (1996) reported a reticulate orna- mentation on the earlier embryonic shaft portion of “bactritids” from the Carboniferous and Permian, respec- tively. However, Doguzhaeva et al. (1999) suggested that some of these specimens may eventually be reassigned to the Coleoidea. In the Ceratitina, Phylloceratina, Lyto- ceratina, Ammonitina, and Ancyloceratina, the embryonic shell lacks lirae and instead is covered with minute tubercles (Kulicki, 1974, 1979; Bandel, 1982, 1986; Bandel et al, 1982; Landman and Waage, 1982; Landman, 1985, 1987; Tanabe, 1989; Kulicki and Doguzhaeva, 1994; Landman et al., in press). To sum up these previous descriptions, at least three kinds of embryonic shell ornamentation have been recognized in the Ammonoidea excluding Upper Paleozoic “bactritids’. Each ammonoid suborder, excluding the doubtful taxon Bactritina, appears to have its own chara- cteristic pattern of ornamentation. ow — © ® © © = F ® D = [2] 2 N © ST Goniatite early shell features 17 Figure 3. gitudinal ridges. walls is discernible in this specimen. UMUT MM19872-8. Discussion Observations of the early embryonic shells of extant Nautilus provide a reference point for discussions about the embryonic development of ammonoids. According to Arnold and Landman (1993) and Tanabe and Uchiyama (1997), the early embryonic shell development of Nautilus can be divided into two stages with different shell microstruc- ture and ornamentation. In the first stage (=early organogenetic stage), a low cap-shaped shell with a distinct median depression (called cicatrix) is secreted in the se- quence of outer conchiolin and inner prismatic layers. The cicatrix lacks growth lines, indicating uniform shell secretion by the mantle primordium (shell gland) on the posterior side of the embryonic body (see Tanabe and Uchiyama, 1997, fig. 1A). In the second stage (=middle organogenetic stage), a new shell consisting of outermost conchiolin, outer prismatic, middle nacreous, and inner prismatic layers ap- pears at the outer margin of the cicatrix, leaving a disconti- nuity in the shell structure at the boundary. It is sculptured by transverse growth lines and radial undulations. At this stage of development, the anterior mantle margin is well dif- ferentiated and possesses three folds, where shell secretion Vidrioceras sp. 3a. Oblique view of embryonic shell with preserving interior dorsal wall sculpture of the first whorl with lon- 3b. Close-up of longitudinal ridges on interior side of dorsal wall. Note that the boundary between ventral and dorsal shell occurs (Tanabe et al., 1991). The absence of transverse lirae on the embryonic shells of the Goniatitina strongly suggests that the walls of the initial chamber and the first whorl were secreted synchronously by the undifferentiated shell gland. Bandel (1982) and Kulicki and Doguzhaeva (1994) hypothesized this kind of embryonic shell development in Mesozoic ammonoids, relying upon ob- servations about the biomineralization of embryonic shells of modern “archaeogastropods”. The longitudinal dorsal layer was probably secreted at a late stage of embryogenesis and occasionally at an early postembryonic stage. The appear- ance of transverse lirae on the postembryonic shell indicates an accretionary mode of growth. This event does not occur synchronously with the development of the dorsal wall with wrinkled ornamentation (Figure 2.1-2.4; Kulicki et al., in press, pl. 2, fig. 3). Such a wrinkled dorsal wall has been extensively recognized in Paleozoic ammonoids in the postembryonic stage (House, 1971; Walliser, 1970). Kulicki (1979, 1996) and Kulicki et al. (2001) have pointed out that the dorsal wall of ammonoids consists of two components, namely, the outer component consisting of organo-prismatic material, sometimes with a wrinkled texture on the outside, and the inner prismatic component that covers the outer @ Figure 2. second whorls exhibits longitudinally ridged ornament on the inner side. Vidrioceras sp. 1. Lateral view of incomplete postembryonic shell, part of whose body whorl is lost. Dorsal wall of the first- UMUT MM19872-4. 2. Ventral view of early postembryonic shell showing change of interior dorsal wall sculpture from longitudinally ridged pattern to wrinkled pattern at embryonic shell/postembryonic shell boundary. UMUT MM19872-5. 3a,b. UMUT MM19872-6. 3a. Oblique view of incomplete postemebryonic shell, showing change of in- terior dorsal wall sculpture from longitudinally ridged pattern in embryonic stage to wrinkled pattern in postembryonic stage. 3b. Close-up of longitudinally ridged dorsal wall structure in early postembryonic stage of same specimen. 4a, b. UMUT MM19872-7. 4a. Ventral view of embryonic (or early postembryonic) shell showing interior feature of dorsal wall with wrinkled ornamentation. 4b. Close-up of wrinkled or- namentation in same specimen. Scale bars: 100 um (1-4a) and 40 um (4b). Arrows in 1, 2, 3a, and 4a point to the approximate position of primary constriction. 18 Kazushige Tanabe et al. component on the adapical side of the body chamber. Our observations indicate that the inner dorsal wall component is absent in the embryonic shells of Vidrioceras. It presuma- bly begins to appear in the postembryonic stage. In view of the absence of transverse lirae, the mode of embryonic shell formation in the Ceratitina, Phylloceratina, Lytoceratina, Ammonitina, and Ancyloceratina may also be explained by the “archaeogastropod model” of Bandel (1982) and Kulicki and Doguzhaeva (1994). The presence of fine transverse lirae on the relatively large embryonic shells of the Devonian suborders Agoniatitina, Anarcestina and Tornoceratina and on their postembryonic shells (see Landman et al., 1996, appendix |!) is, however, problematic. One possibility is that in the embryonic stage the mantle al- ready was differentiated in the embryonic stage to secrete a shell with growth lines at its anterior margin. This type of embryonic shell development would be described as accretionary growth. A second possibility is that the embry- onic shell was rapidly mineralised and an accretionary mode of growth characterized only the postembryonic shell (Klofak et al., 1999). Future research utilizing well preserved mate- rial will resolve this problem. Acknowledgements We thank John Arnold, Klaus Bandel and Larisa Doguzhaeva, Sigard von Boletzky and Yasunari Shigeta for critical discussion, and Curtis Faulkner and Susan Klofak for help in collecting and preparing the specimens utilized. This work was supported by a Grant-in-Aid for Scientific Research from the Japan Society for Promotion of Science (no. 12440141 for 2000). References Arnold, J. M. and Landman, N. H., 1993: Embryology of Nautilus: Evidence for two modes of shell ontogeny. Journal of Cephalopod Biology, vol. 2, p. abst. 1. Bandel, K., 1982: Morphologie und Bildung der frühontogene tischen Gehäuse bei conchiferen Mollusken. Facies, vol. 7, p. 1-198, pls. 1-22. Bandel, K., 1986: The ammonitella: a model of formation with the aid of the embryonic shell of archaeogastropods. Lethaia, vol. 19, no. 2, p. 171-180. Bandel, K., Landman, N. H. and Waage, K. M., 1982: Microornamentation on early whorls of Mesozoic ammonoids: Implications for early ontogeny. Journal of Paleontology, vol. 56, no. 2, p. 386-391. Beecher, C. E., 1890: On the development of the shell in the genus Tornoceras Hyatt. American Journal of Science, vol. 40, p. 71-75. Doguzhaeva, L. A., 1996: Shell ultrastructure of the Early Permian Bactritella and Ammonitella, and its phylogenetic implication. Jost Wiedmann Symposium on Cretaceous Stratigraphy, Paleobiology and Paleobiogeography, Abstract Volume, Report of Geologisch- Paläontologisches Institut der Universitat Kiel, no. 76, p. 19-24. Doguzhaeva, R. A., Mapes, R. H. and Mutvei, H., 1999: A Late Carboniferous spirulid coleoid from the southern Mid- Continent (USA). In, Olöriz, F. and Rodriguez-Tover, F. J. eds., Advancing Research on Living and Fossil Cephalopods, p. 47-57. Kluwer Academic/Plenum, New York. Druschits, V. V. and Doguzhaeva, L. A., 1981: Ammonity pod Elektronym Mikroskopom [Ammonites under the Electron Microscope]. 238 p., 43 pls. Moscow University Press, Moscow. (in Russian) Druschits, V. V. and Khiami, N., 1970: Stroyeniye sept, stenki protokonkha i nachal’nykh oborotov rakoviny nekotorykh rannemelovykh ammonitov [Structure of the septa, protoconch walls and initial whorls in Early Cretaceous ammonites]. Paleontologicheskii Zhurnal, 1970, no. 1, p. 35. (in Russian) Erben, H. K., 1964: Die Evolution der altesten Ammonoidea. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, vol. 120, no. 2, p. 107-212. House, M. R., 1965: A study in the Tornoceratidae: The suc- cession of Tornoceras and related genera in the North American Devonian. Philosophical Transactions of the Royal Society of London, Series B, vol. 250, no. 763, p. 79-130, pls. 1-11. House, M. R., 1971: The goniatite wrinkle-layer. Smithsonian Contribution to Paleobiology, vol. 3, p. 23-32, pls. 1-3. Klofak, S. M., Landman, N. H. and Mapes, R. H., 1999: Embryonic development of primitive ammonoids and the monophyly of the Ammonoidea. In, Oloriz, F. and Rodriguez-Tovar, F. J. eds., Advancing Research on Living and Fossil Cephalopods, p. 23-45. Kluwer Academic/Plenum, New York. Kulicki, C., 1974: Remarks on the embryogeny and postembryonal development of ammonites. Acta Palaeontologia Polonica, vol. 19, p. 201-224. Kulicki, C., 1979: The ammonite shell: its structure, develop- ment and biological significance. Palaeontologia Polonica, no. 39, p. 97-142, pls. 24-48. Kulicki, C., 1996: Ammonoid shell microstucture. /n, Landman, N. H., Tanabe, K. and Davis, R. A. eds., Ammonoid Paleobiology, p. 65-101. Plenum Press, New York. Kulicki, C. and Doguzhaeva, L. A. 1994: Development and cal- cification of the ammonitella shell. Acta Palaeontologia Polonica, vol. 39, no. 1, p. 17-44. Kulicki, C., Tanabe, K., Landman, N. H. and Mapes, R. H., 2001: Dorsal shell wall in ammonoids. Acta Palaeon- tologia Polonica, vol. 46, no. 1, p. 23-42. Kulicki, C., Landman, N. H., Mapes, R., Tanabe, K. and Haney, M., in press: Buckhorn Asphalt goniatites ammonitellae, the oldest, preserved with primary mineral composition. Abhandlungen der Geologischen Bundesanstalt, Special Volume (Proceedings of the 5th International Symposium, Cephalopods-Present and Past, Vienna, 1999). Landman, N. H., 1982: Embryonic shells of Baculites. Journal of Paleontology, vol. 56, no. 5, p. 1235-1241. Landman, N. H., 1985: Preserved ammonitellas of Scaphites (Ammonoidea, Ancylocerataceae). American Museum Novitates, no. 2815, p. 1-10. Landman, N. H., 1987: Ontogeny of Upper Cretaceous (Turonian-Santonian) scaphitid ammonites from the Western Interior of North America: Systematics, develop- mental patterns, and life history. Bulletin ofthe American Museum of Natural History, vol. 185, no. 2, p. 118-241. Landman, N. H. and Bandel, K., 1985: Internal structures in the early whorls of Mesozoic ammonites. American Museum Novitates, no. 2823, p. 1-21. Goniatite early shell features Landman, N. H. and Waage, K. M., 1982: Terminology of structures in embryonic shells of Mesozoic ammonites. Journal of Paleontology, vol. 56, no. 5, p. 1293-1295. Landman, N. H., Tanabe, K. and Shigeta, Y., 1996: Ammonoid embryonic development. /n, Landman, N. H., Tanabe, K. and Davis, R. A. eds., Ammonoid Paleobiology, p. 343- 405. Plenum Press, New York. Landman, N. H., Mapes, R. H. and Tanabe, K., 1999: Internal features of the embryonic shells of Late Carboniferous Goniatitina. /n, Oloriz, F. and Rodriguez-Tovar, F. J. eds., Advancing Research on Living and Fossil Cephalopods, p. 243-254. Kluwer Academic/Plenum Publishers, New York. Landman, N. H., Bizzarini, F., Tanabe, K. and Mapes, R. H., in press: Microornamentation on the embryonic and postembryonic shells of Triassic ceratites (Ammonoidea). American Malacological Bulletin. Mapes, R. H., 1979: Carboniferous and Permian Bactritoidea (Cephalopoda) in North America. University of Kansas, Paleontological Contribution, Article 64, p. 1-75, pls. 1- 41. Miller, A. K., 1938: Devonian ammonoids of America. Geological Society of America, Special Papers, no. 14, p. 1-262. Tanabe, K., 1989: Endocochliate embryo model in the Mesozoic Ammonitida. 183-196. Tanabe, K. and Uchiyama, K., 1997: Development of the em- bryonic shell structure in Nautilus. The Veliger, vol. 40, no. 3, p. 203-215. Tanabe, K., Tsukahara, J., Fukuda, Y. and Taya, Y., 1991: Histology of a living Nautilus embryo: Preliminary obser- vations. Journal of Cephalopod Biology, vol. 2, no. 1, p. 13-22. Tanabe, K., Landman, N. H., Mapes, R. H. and Faulkner, C. J., 1993: Analysis of a Carboniferous embryonic ammonoid assemblage from Kansas, U.S.A.-Implications for ammonoid embryology. Lethaia, vol. 26, p. 215-224. Tanabe, K., Landman, N. H. and Mapes, R. H., 1994: Early shell features of some Late Paleozoic ammonoids and their systematic implications. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 173, p. 384-400. Tanabe, K., Shigeta, Y. and Mapes, R. H., 1995: Early life his- tory of Carboniferous ammonoids inferred from analysis of shell hydrostatics and fossil assemblages. Palaios, vol. 10, p. 80-86. Walliser, ©. H. 1970. Über die Runzelschicht bei Ammonoidea. Goettinger Arbeiten zur Geologie und Paläontologie, vol. 5, p. 115-126, pls. 1-4. Historical Biology, vol. 2, p. + eg, An EM e ® » à d 2 FRE 4 x > +1 un le nigh ay ol! aA N mpm} leu $y wun “a tom = 4 Ve tam’ ars ’ é à i mi 25 f = en PAR A A E | wi AD - am? pans er, b LL 6 arr ü a aie k oe m a N — Ss - u À mi CU | st sh Liha, CE - | h wean = i CTA PER hee a ene Br N o Bi ’ e z; ip PAL ù | ai \ Paleontological Research, vol. 5, no. 1, pp. 21-31, April 30, 2001 © by the Palaeontological Society of Japan Macro- and microstructure of shell and operculum in two Recent gastropod species, Nerita (Theliostyla) albicillaand Cinnalepeta pulchella (Neritopsina: Neritoidea) TAKENORI SASAKI The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan (sasaki@um.u-tokyo.ac.jp) Received 3 October 2000; Revised manuscript accepted 26 December 2000 Abstract. The shell and opercular structures of Nerita (Theliostyla) albicilla and Cinnalepeta pulchella were described and compared with those of other extant members of Neritopsina. The shell of N. (T.) albicilla is composed of four layers: the outermost prismatic layer, followed by the simple crossed-lamellar layer, the myostracum, and the inner complex crossed-lamellar layers. The operculum consists of three prismatic layers deposited on both sides of an organic layer. C. pulchella also has a four-layered shell, but lacks an operculum. The outer layer is a homologous structure. The shells of Recent neritopsine families can be categorized into a four-layered group (Neritiliidae, Neritidae, and Phenacolepadidae) and a three-layered group (other families). In con- trast, opercular structure is markedly variable in the Neritopsina, and little correlation can be estab- lished in the light of phylogenetic evolution or adaptation. Key words: Neritidae, Neritopsina, operculum, Phenacolepadidae, shell structure Introduction Neritopsina is a phylogenetically distinct gastropod clade which originated in the Ordovician (Bandel and Fryda, 1999). The Recent members share characteristic apomorphies of odontophoral cartilages and muscles, ante- rior digestive tract, reproductive organs, and nervous system (Haszprunar, 1988; Ponder and Lindberg, 1997; Sasaki, 1998) and exhibit successful adaptive radiation in a wide range of habitats in deep-sea hydrothermal vent or hydro- carbon seep, submarine cave, intertidal rocky shore, and nonmarine aquatic and terrestrial environments (Ponder, 1998; Sasaki, 1988). It is also particularly interesting that neritopsines have rich fossil records since the early Paleozoic (Bandel, 1992; Bandel and Fryda, 1999), and that ancient taxa like Neritopsis have survived as relics in cryptic habitats (Kase and Hayami, 1992). Among hard-part characters, shell structure, along with larval shell morphology, is of primarily taxonomic importance for studies uniting fossil and Recent taxa of Gastropoda (Bandel, 1982; 1988; 1991; Bandel and Geldmacher, 1996). In Gastropoda, Patellogastropoda are known to exhibit re- markable diversification of the shell microstructure (MacClintock, 1967; Lindberg, 1988, 1998). Grouping by shell structure corresponds well to the anatomical division of supraspecific taxa, and therefore enables paleontologists to allocate fossilized taxa within an anatomy-based systematic scheme (Kase, 1994; Kase and Shigeta, 1996; Lindberg and Hedegaard, 1996; Hedegaard et al., 1997). As for other gastropod higher taxa, Vetigastropoda are typically charac- terized by the apomorphic occurrence of columnar nacreous structure, although some taxa have supposedly lost it secon- darily (Hedegaard, 1997). In the Apogastropoda, which is a huge clade including Caenogastropoda and Hetero- branchia, the shells are composed primarily of several layers of crossed-lamellar structure and differences between dis- tantly related subclades within it are in general minor (Bog- gild, 1930; Bandel, 1979; Togo and Suzuki, 1988). At rela- tively lower rank, however, some striking differences can be revealed by detailed comparison, as was shown in littorinid genera by Taylor and Reid (1990). Despite its unique phylogenetic status among gastropods, little discussion has been devoted to exoskeletal evolution of Neritopsina as compared to other major taxa of molluscs. The current Knowledge of neritopsine hard-part structures is derived from only a limited amount of literature, and in addi- tion, most data have been documented in simple format with a few or no illustrations. To increase data quality and 22 Takenori Sasaki quantity on neritopsine hard parts, this study aims to de- scribe the shell and opercular structures of two Recent spe- cies in detail from the macro- to microscopic level. The results of the observations were compared with the pub- lished data of other neritopsines in the literature, and their similarities and dissimilarities were discussed from phylogenetic and adaptational viewpoints. Material and methods The shells of Nerita (Theliostyla) albicilla were collected alive from an intertidal zone at Banda, Tateyama, Chiba Prefecture, central Japan, and living specimens of Cinnalepeta pulchella from Tosashimizu, Kochi Prefecture, southwest Japan were provided by Dr. Shigeo Hori. In the laboratory, the macroscopic morphology and the distribution of shell layers based on texture were first observed under a binocular microscope. Then, the shell was crushed with a hammer, and the original position of fragments was labeled before cleansing in bleach for 12 hours and later in running water for 30 minutes. The fresh fracture of shell fragments was observed with a scanning electron microscope (SEM). The description of microstructure was made on layer dis- tribution, boundary between layers, form of crystal aggrega- tion, and orientation and morphology of first- to third-order units (major to minor structural arrangement). The descrip- tive terminology of microstructure follows Carter and Clark (1985) and Kano and Kase (2000b). The two terms, “cros- Outer Layer 1018]S0d Inductura sed lamellar” and “complex crossed lamellar,” are abbrevi- ated as “CL” and “CCL.” Terms for orientation were based on the following criteria: (1) “anterior-posterior” direction was determined by body axis of the animal, and (2) “adaxial-abaxial” distinction rela- tive to coiling axis of whorls was used to indicate relative po- sition along inner-outer lips of the aperture. The samples used in this study are preserved in the University Museum, the University of Tokyo (UMUT). Description Order Neritopsina Cox and Knight, 1960 Superfamily Neritoidea Rafinesque, 1815 Family Neritidae Rafinesque, 1815 Nerita (Theliostyla) albicilla Linnaeus, 1758 Figures 1-5 Shell.—The shell is elongate along the anterior-posterior axis of the animal. The spire is completely depressed as a part of rounded whorls, and the external part of the shell is mostly occupied by a large body whorl and an extended ap- erture. The outer lip of the aperture is thickened and indented with elongate denticles, being arranged parallel to the apertural margin. The inner lip spreads widely over the body whorl to form a robust inductura. The shell wall near the outer lip consists of three layers; Inner Layer DS AS uch —. De ù rn © 2) y A . N % ie AU / N ae I, RA iy) Denticle 5mm Figure 1. Apertural view of the shell of Nerita (Theliostyla) albicilla, The sculpture and texture of the surface are depicted slightly sche- matically. The dark outer layer is distinguished by fine-grained smooth surface, the middle layer exhibits dense linear pattern of CL structure, and most of the inner layer is visible as irregularly oriented lines. i.e. outer and middle layers and a distinct denticular zone (Figure 1). The outer layer contains black pigments, encir- cles the apertural margin, and makes a clear contrast with the pale inner layer. Microstructurally this layer is formed of a thick aggregate of short prisms (Figure 3A), which can be identified as blocky prismatic structure. The prisms attain less than 4 um in length and 1 um in width. The middle layer is composed of comarginal simple CL structure (Figure 3B-E). The linear lines of the first-order units are clearly visible on the inside of the aperture even at low magnifica- tion (Figures 1, 2). The denticular zone is built up of a thin layer of irregularly crossed fine crystals (CCL structure). The denticles do not continue spirally toward the inside of the aperture but remain in the identical position due to resorption. The inner lip margin is shallowly curved with two to four small nodules (Figure 1). The surface of the inductura is roughened with nodules of various size, and their number and distribution are considerably variable intraspecifically. The inductura, especially near the inner lip, shows an irregu- lar texture reflecting the first-order arrangement (Figure 1). There is no sharp boundary between the CL structure of the middle layer and the CCL structure of the inductura. The linear patterns of the middle layer gradually merge into the irregular patterns of the inductura (Figure 1). Shell muscle scars are separated into a disjunct pair cor- responding to right and left shell muscles (see Sasaki, 1998: Septum Prismatic Sublayer Inner Lip Middle Layer Figure 2. Schematic representation of inner part of whorls of Nerita (Theliostyla) albicilla, seen from the outer lip of the aperture. Left Muscle Scar Shell structure of neritopsine gastropods 23 fig. 73a). The left scar is located on the basal side near the inner lip (Figure 2), while the right one lies on the opposite, apical side. The scars are deeply impressed on the interior shell surface and reflect the form of muscles which are di- vided into bundles (Figure 2). The myostracum from the left scar is formed as a vertical stack of irregular prisms (Figure 3F), and its thickness exceeds 80 ym in an adult shell. The myostracum from the right scar is immediately resorbed and not traceable in most sections. The inside of the visceral part of the shell is extensively resorbed and reorganized as a hollow space without a true columella. A platy septum connecting the inner lip and api- cal wall of the shell is secreted and inserted into the narrow space between head-foot and uncoiled visceral mass of the animal (Figure 2; see also Sasaki, 1998: fig. 73a). The sep- tum, inner lip, inductura, and the interior of whorls are all constructed as a continuity of the inner layer (Figure 2). The layer has CCL structure: lathy third-order units are set radially to form fan-shaped second-order units, which in turn are vertically stacked to form wedgelike first-order units which are irregularly oriented and interdigitate with one an- other (Figure 3G, H). The structure appears as spinous crossing prisms at the initial stage of formation near its growth front. Several very thin prismatic sublayers are in- serted in a thick CCL layer of the inductura (Figure 2). Operculum.—The operculum is heavily calcified with a distinct apophysis (Figure 4A, B). The exterior surface is Inductura Outer Layer S RE WLM OR ere > A ee BG VAGUE = 29 z » Middle Layer 57 52 KA N Inner Layer ESS Myostracum 3 mm Outer Layer Shell layers on cut planes are illustrated based on the results of observations with SEM. RZ & 2] is) ao = o c ® = © bE Se N Shell structure of neritopsine gastropods Apophysis Nucleus Organic Layer Outer Layer Outer Layer Organic Layer 25 Right Opercular Muscle Scar Apophysis Left Opercular Middle Muscle Scar Layer 3mm Figure 4. Operculum of Nerita (Theliostyla) albicilla. A. Exterior view. B. Interior view. C. Vertical section showing the growth direc- tion of prisms in three calcified layers. covered with small nodules which tend to be arranged spi- rally (Figure 4A). The nucleus lies on the adaxial basal side at the origin of the spiral growth line. The calcified part of the operculum can be divided into three layers (Figure 4C). The outer and inner layers are both composed of slightly inclined, nearly vertically ordered prisms (Figure 5B, D). In the middle layer, prismatic crys- tals are arranged in a spherulitic form (Figure 5C). A very thin organic layer, the homologue of the noncalcified operculum of other gastropods, is mostly concealed be- tween the outer and middle layers and appears only along the abaxial margin (Figure 4A, B). The adaxial side of the operculum is partially embedded in the pedal musculature of the animal and marks clear depres- sions of muscle scars (Figure 4B). The left scar is small and very irregular with nearly concentric lines (Figure 5A). The right scar is elongated along the abaxial margin and smoothened. Cut position is shown in Figure B with solid lines. Family Phenacolepadidae Rafinesque, 1815 Cinnalepeta pulchella (Lischke, 1871) Figures 6, 7 Shell.—The shell is completely limpet-shaped and elon- gated along the anterior-posterior axis (Figure 6). The apex is situated at the posterior end of the shell. The larval shell in the original position of the apex is involved between whorls and inner lip during growth and no longer visible in a fully matured adult shell. The inside of the apex is slightly remoulded by resorption, but a septumlike structure is not constructed in this species. The shell consists of four layers, including the myostracum. The outer layer is composed of fine homoge- neous crystals (homogeneous structure) (Figure 7A, B). The middle layer is of commarginal simple CL structure. It is somewhat transparent, and clearly demarcated from the ae a a ee a eh oh ey nn æ Figure 3. SEM micrographs of shell microstructure of Nerita (Theliostyla) albicilla (UMUT RM27950). A. Blocky prismatic structure of outer layer. Scale =5 m. B. Outcrop pattern of simple CL structure near outer lip of aperture. Scale = 20 um. C. Oblique view of the frac- ture of simple CL structure in the middle layer. Scale = 20 um. D. Horizontal view of the fracture of the same layer. Scale=20 um. E. Enlarged view of the same layer, showing the arrangement of the third-order units of CL structure. Scale=5 um. F. Vertical fracture of the myostracum inserted between inner (above) and middle (below) layers. M = myostracum. Scale = 40 um. G. Outcrop pattern of CCL struc- ture on interior surface of the whorls. Scale = 20 um. H. Vertical fracture of the same structure in inner layer. Scale = 20 um. 26 Takenori Sasaki Figure 5. SEM micrographs of opercular microstructure of Nerita (Theliostyla) albicilla(UMUT RM27951). A. Surface of left opercular muscle scar with irregularly concentric lines. Scale = 250 um. B. Vertical fracture of outer prismatic layer. Scale = 10 um. C. Vertical fracture of the middle layer, showing spherulitic arrangement of prisms. Scale = 10 um. D. Oblique view of a section of inner prismatic layer. Scale = 5 um. brown outer layer. Linear patterns of the first-order units of the middle layer are parallel near the shell margin and in- crease in irregularity toward the center (Figure 6). In the typical regular simple CL structure near the apertural mar- gin, the crossing angle of the second-order lamellae is ap- proximately 125 degrees. The inner layer consists of a CCL structure with fan-shaped second-order and lath-type third- order units (Figure 7D, E). The inner lip projects inside along the posterior apertural margin and is formed as an extension of the CL structure of the middle layer (Figure 6). It lies between the ventral pos- terior of the visceral mass and the dorsal posterior of the foot of the animal. The muscles scars are distributed in an elliptical form, keeping an almost constant distance from shell margin (Figure 6). They are inserted by two kinds of muscles of the animal: the thicker horseshoe-shaped part is the attachment of pedal retractor muscles (including head retractors in part), and the thinner anterior part is that of pallial muscle hanging the mantle onto the interior of the shell. The myostracum from these muscle scars is a thin layer of vertically oriented columnar prisms (Figure 7C). The surface of the pedal muscle scar is deeply impressed and exhibits a ridgelike rough sculpture (Figure 7F). Operculum.—The operculum is completely absent and was not found in any section of pedal musculature as al- ready described by Sasaki (1998: 120). Discussion Recent forms of neritopsine gastropods comprise nearly 120 genera and subgenera (Vought, 1989). Although differ- ent opinions exist regarding suprageneric systematics, the Recent forms can be grouped into at least seven families, namely Neritopsidae, Hydrocenidae, Helicinidae [this family may be divided into Ceresidae, Proserpinidae, and Helicinidae (Thompson, 1980)], Titiscaniidae, Neritiliidae, Neritidae, and Phenacolepadidae [“Shinkailepadidae” is probably included here] (Ponder, 1998; Sasaki, 1998; Bandel and Fryda, 1999; Kano and Kase, 2000a, b; see also Sasaki, 1998 for their anatomical basis). Information on their shell and opercular structure can be summarized as fol- lows. Shell structure of Recent Neritopsina Shells of only ten genera belonging to six families have Anterior Outer Layer Pallial Muscle Scar Middle Layer Inner Layer Apex Posterior 2 mm Figure 6. Apertural view of Cinnalepeta pulchella. The sculpture texture of the surface is illustrated slightly schematically. The outer layer is separated from other parts by deep brown color, the middle layer is represented by concentric lines of CL structure, and the inner layer is visible as fine irregular lines of CCL structure. been investigated at the microstructural level (Table 1). Major differences among suprageneric taxa are found mainly in the number of shell layers, the microstructure of each layer, and the crystal forms of carbonate calcium (aragonite-calcite). (1) Neritopsidae: This family is characterized by intact inner upper whorls in contrast to other families with resorbed, hollow whorls inside (Bandel and Fryda, 1999). The shell wall of Neritopsis radula was described as “having two crossed-lamellar layers” by Batten (1979), but according to Suzuki et al. (1991), it is composed of an aragonitic outer layer of CL structure and an aragonitic inner layer of “proto- crossed lamellar, irregular prismatic, homogeneous, and complex crossed lamellar structures.” The mixture of four microstructures in the inner layer of N. radula is, therefore, a unique feature among Neritopsina. (2) Hydrocenidae: The shell of Georissa japonica has three layers including the myostracum: the thicker aragonitic outer layer is of CL structure, and the thinner inner aragonitic Shell structure of neritopsine gastropods layer is primarily of irregular prismatic structure and subsidiarily of “protocrossed-lamellar’ structure (Suzuki et al., 1991). (3) Helicinidae: The shell of Waldemaria japonica (Helicininae) has almost the same structural design as that of Georissa japonica, but the inner layer is mainly occupied by “protocrossed-lamellar” structure (Suzuki et a/., 1991). Microstructural data have not been provided for any other member of these families. (4) Titiscanidae: This family totally lacks the shell at least at the adult stage (Bergh, 1890; Taki, 1955). (5) Neritilidae: This group had been extremely poorly known taxonomically but was redefined by Kano and Kase (2000a, b) as small neritiform gastropods with (i) spiral ridges on the protoconch, (ii) the inclination of the protoconch against the teleoconch, and (iii) perpendicular, not inclined, prisms in the outer shell layer. The shell of Pisulina species consists of four layers: an outer layer of simple irregular prisms, middle layer of simple CL structure, myostracum, and inner layer of CCL structure with prismatic sublayers (Kano and Kase, 2000b; figs. 6, 7). (6) Neritidae: All neritid taxa so far investigated share a four-layered shell consisting of an outer layer of calcitic pris- matic structure, middle layer of aragonitic CL structure, myostracum, and inner layer of aragonitic CCL structure (Table 1). Their shells can be further classified into two types based on relative thickness of shell layers: marine species have a thicker outer layer with a_ thinner periostracum, while nonmarine species have a reduced outer layer with a well developed periostracum (Suzuki et al. 1991). This difference is, however, considered to be in- duced by environmental factors, because thin shells pro- tected by a thick periostracum occur in various distantly related brackish and freshwater mollusks. (7) Phenacolepadidae: The only description for this family was given for Cinnalepeta pulchella in this study, and the dif- ference from other families lies in the homogeneous struc- ture of the outer layer. Operculum of Recent Neritopsina Neritopsine operculum exhibits a great diversification in the number of calcified layers, the coverage of the organic layer, the position of calcareous layer(s) on one or both sides of the organic layer, the presence or absence of apophysis, and the morphology of muscle scars. (1) Neritopsidae: The exterior surface of the operculum of Neritopsis radula is covered with a thick callus without a nu- cleus and spiral lines; the interior is divided into a smooth semilunar zone at the abaxial side and a large projection with a radial striation at the adaxial side (Thiele, 1929: fig. 55; Wenz, 1938: fig. 1001; Knight et al., 1960: fig. 182; Ponder, 1998: fig. 15.71C, D). This projection may be the hypertrophied homologue of the apophysis of other neritopsines, with its origin shifted toward the center. The absence of a spiral line on both surfaces and a large projec- tion from the interior center is quite unique among Gastropoda. However, no microstructural data for this fam- ily have been published to date. (2) Hydrocenidae: The operculum of Georissa japonica is calcified with an apophysis and three-layered: the organic 28 Takenori Sasaki Figure 7. SEM micrographs of shell microstructure of Cinnalepeta pulchella (UMUT RM27952). A. Vertical fracture of the outer layer. Scale = 20 um. B. Enlarged view of homogeneous structure. Scale = 5 um. C. Vertical fracture of pedal muscle scar showing the myostracum overlying the middle layer. M= myostracum. Scale= 10 um. D. Vertical fracture of CCL structure near the center of the shell. Scale = 10 um. E. Oblique fracture (below) and outcrop surface (above) of CCL structure. Scale=50 um. F. Oblique view of pedal muscle scar near inner lip, showing irregular rough surface. layer on the outermost surface is underlain by two aragonitic layers of irregular prismatic structure (Suzuki, et al., 1991: fig. 5). (3) Helicinidae: This family is highly specialized for Neritopsina in that Ceresinae and Proserpininae completely lack an operculum, while Helinicinae have a calcified operculum without an apophysis (Thompson, 1980). The Scale = 200 pm. operculum of Waldemaria japonica has a single layer of calcitic blocky structure on an organic layer (Suzuki, et al, 1991). Helicinids are strikingly different form other neritopsines in that calcification occurs only on the exterior surface, not interior of the organic layer. (4) Titiscanidae: This shell-less taxon also lacks an operculum and is completely sluglike (Bergh, 1890; Taki, Table 1. Published data on shell microstructure of the Recent Neritopsina. crossed lamellar, HO = homogeneous, IPR = irregular prismatic, PCL = protocrossed lamellar, PR = prismatic. Shell structure of neritopsine gastropods 29 BL = blocky, CCL = complex crossed lamellar, CL = simple Shell microstructu re Family Genus Outer layer(s) Inner layer Reference Neritopsidae Neritopsis CL CL Batten (1979) Neritopsis CL PCL, IPR, HO, CCL Suzuki et al. (1991) Hydrocenidae Georissa CL PCL, IPR Suzuki et al. (1991) Helicinidae Waldemaria CL PCL, IPR Suzuki et al. (1991) Neritiliidae Pisulina PR CL CCL Kano and Kase (2000b) Neritidae Nerita PR CL CCL Boggild (1930); Gainey and Wise (1980);This study Nerita BL CL PCL Suzuki et al. (1991) Neritina PR CL CCL Boggild (1930) Neritina BL CL PCL Suzuki et al. (1991) Clithon BL CL PCL Suzuki et al. (1991) Neripteron BL CL PCL Suzuki et al. (1991) Septaria BL CL PCL Suzuki et al. (1991) Phenacolepadidae Cinnalepeta HO CL CCL This study 1955). (5) Neritiliidae: In the species of Pisulina, the operculum is secreted with exterior corneous and interior calcareous lay- ers (Kano and Kase, 2000b: figs. 8, 9, 11). The small initial part containing the nucleus on the corneous layer is demar- cated from the remaining part. The muscle scars are di- vided into three areas: two elongate zones along the adaxial and basal margins, and a central one extending between the nuclear zone and apophysis. The inner calcareous layers are formed of spherulitic prisms (Kano and Kase, 2000b: fig. 6F). (6) Neritidae: The gross morphology of the neritid operculum is classified into two distinct types (see e.g. Starmühlner, 1993; Komatsu, 1986): (i) The operculum of Septaria (subfamily Septariinae) is embedded in the dorsal part of the foot. The anterior left corner has a sharp projec- tion which is supposedly homologous to the apophysis of other neritopsines on the left side. (ii) The rest of the neritids (subfamilies Neritinae and Smaragdiinae) have a semilunar external operculum with a prominent apophysis. The opercular microstructure of neritids is known to be variable, depending on habitats. The marine neritids have a common opercular plan with a single exterior aragonitic prismatic layer, an organic layer, and two interior aragonitic prismatic layers (Suzuki et a/., 1991: fig. 5; this study: Figs. 4,5). The opercula of nonmarine species (Neritina and Clithon) have only two aragonitic prismatic layers covered by a well developed organic layer (Suzuki et al., 1991). The operculum of Bathynerita naticoidea (tentatively treated as a neritid here) dwelling exclusively in deep-sea hydrocarbon seeps is “partly calcified with a thicker calcare- ous layer where it is attached to the foot’ (Warén and Bouchet, 1993), and the apophysis is absent. Its operculum with only partial calcification is greatly different from those of shallow-water neritids. (7) Phenacolepadidae: The opercular morphology of phenacolepadids can be divided into three distinct states. (i) The presence of a vestigial internal operculum with inte- rior calcification and rudimentary apophysis was docu- mented by Fretter (1984) in Phenacolepas omanensis and observed with SEM for the first time by Kimura and Kimura (1999: fig. 7C, D) in Phenacolepas sp. (ii) The opercula of so-called “Shinkailepedidae” has double structure of calci- fied anterior and noncalcified posterior parts as described in Shinkailepas by Okutani et al. (1989: fig. 12) and Beck (1992: pl. 1, fig. 4) and in Olgasolaris by Beck (1992: pl. 5, fig. 4). Double-layered nail-shaped operculum is strikingly convergent with that of the neritid genus Septaria. (iii) The operculum is absent in Cinnalepeta, as described above. Implication of neritopsine hard-part microstructures It has been generally accepted that microstructural char- acters of the shells are useful for the understanding of molluscan higher taxonomy. It is, however, necessary to check the correlation between taxonomic distribution of structural morphotype and phylogenetic relationships in the Recent taxa before comparing extant and extinct forms directly. (1) Shell structure: As reviewed above, the patterns of shell structure of the Recent Neritopsina can be categorized into two major types: (i) Genera of three families, Neritidae, Phenacolepadidae, and Neritiliidae, all have four-layered shells in which inner CCL and middle CL layers are overlaid by a prismatic (in Neritidae and Neritiliidae) or homogeneous (in Phenacolepadidae) shell layer. (ii) By contrast, other families such as Neritopsidae, Helicinidae, and Hydro- cenidae secrete three-layered shells which consist mostly of CL/CCL structures and lack an additional outer layer. This apparent difference between the two groups may be viewed as expressing the distinctness of their relationship, but it is still premature to present phylogenetic implication because of the lack of a reliable phylogenetic hypothesis. The phylogenetic analysis has been conducted only in a part of Neritopsina by Holthuis (1995) and Sasaki (1998), and the phylogenetic status of Neritopsidae, Helicinidae, and Hydrocenidae is totally unknown. The scarceness of struc- 30 Takenori Sasaki tural data relative to the number of existing genera is also problematic so far as testing the stability of character states within each family. Another unresolved problem is whether all of the taxa with a four-layered shell share a calcitic outer layer or not. Suzuki et al. (1991) revealed that at least the shell of neritids is constructed from a calcitic outer layer and otherwise aragonitic layers in contract to the entirely aragonitic shell of other families. They argued that this bimineralic composi- tion is attributable to adaptation to a shallow aquatic environ- ment, probably as a means of reinforcing the mechanical strength of the shell. Thus, it should be tested as a next step whether non-neritid four-layered shells are also made of two crystal forms of calcium carbonate. Concerning the outermost shell layer, Taylor and Reid (1990) revealed the parallel homoplastic addition of a calcitic outer layer in some genera within littorinid gastropods. This means that the convergence in conchological characters should necessarily be considered also at the microstructural level in other groups of molluscs. (2) Opercular structure: The opercular structure can be di- vided into several types as a result of the above comparison: (i) three (single exterior and two interior) aragonitic layers in marine neritids, (ii) two interior aragonitic layers in Hydrocenidae and nonmarine neritids, (iii) single calcitic ex- terior layer without interior calcification in Helicininae, (iv) interiorly calcified operculum with unknown layer distribution in Neritiliidae and a part of Phenacolepadidae, and (v) ab- sence of an operculum in Titiscaniidae and in part in the Phenacolepadidae and Helicinidae. Thus, a single similar state often occurs across several different families, and also several different states can coexist within the same family. At the family level the similarity and dissimilarity in opercular structure are very difficult to explain in the phylogenetic con- text. In connection with nonphylogenetic factors, the less calci- fied opercula in nonmarine neritids as compare with marine confamilial members may be explained as a consequence of adaptation to low-salinity environments (Suzuki et al., 1991). However, in other taxa, there is no Clear correlation between opercular structure and habitat selection. The marked dif- ferences in neritopsine opercular structure is difficult to un- derstand also in terms of adaptation. The possession of apophysis is presumably under phylogenetic control within Neritopsina, and at the same time, it is a convergent state also found in caenogastropod rissoideans. The peglike structure has possibly arisen to increase the area of muscu- lar attachment in this case. Because of the insufficient resolution of neritopsine phylogeny and the lack of mineralogical data in part, the evolutionary scenario of neritopsine hard parts remains largely speculative at present. For further studies, exoskeletal structure including mineralogical characters should be investigated more comprehensively in whole ex- tant and extinct neritopsines together with the comparative anatomy and molecular phylogeny of the Recent species. Acknowledgments | deeply thank Kazushige Tanabe (Department of Earth and Planetary Science, University of Tokyo), Yasunori Kano (Department of Biological Sciences, University of Tokyo) and two anonymous reviewers for their constructive com- ments and suggestions. The samples of Cinnalepeta pulchella were kindly provided by Shigeo Hori (Kuroda Chiromorphology Project, Japan Science and Technology Corporation). This work was partly supported by the Grant- in-Aid from the Japan Society for Promotion of Science (No. 12440141). Reference Bandel, K., 1979: Übergänge von einfacheren Strukturtypen zur Kreuslamellenstruktur bei Gastropodenschalen. Bio- mineralization, vol. 10, p. 9--38. 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G ebrüder Borntraeger, Berlin. tank nf Un Ni Ana . jan «ay ioe wur A I Ira toe hr | , u à PCT 2 "dite N Fr ar : À = re Bert MR? : x u eur q En ey TEN 6. a EN ur * Var tri inet htt i Pen te eit | PCA TT Pr) 4) ‘nie? Ds uy) ot: DOME vey VOR Be eit MU Du gi Ri uly et We jit dnt Nas AN x. à a aes fh ety bal ‘4 jae NIEREN rs ahi w ke ty TE te ER : i pa ‘ Wi LE OT Or Meas REN , et ee ds pes Seay wet Soy a : yer wart Wick LS à : CVS { oy fi Ke PS aM L gt PAT nes Er wee ORE NA NER re wer‘ c PA és à“ Sov te 4. she fd CRT LS ah! ane f i où qu: ls hier” CH yO M = MAS DE k A SE a one Ceara) A Lge 9 i ees | oe Se A: ef PL CIE Fe} SL A. dt Tann, cp « . sv ‘Lew a L è n Paleontological Research, vol. 5, no. 1, pp. 33-44, April 30, 2001 © by the Palaeontological Society of Japan Geometric pattern and growth rate of prismatic shell structures in Bivalvia TAKAO UBUKATA Institute of Geosciences, Shizuoka University, Oya 836, Shizuoka, 422-8529, Japan (sbtubuk @ipc.shizuoka.ac.jp) Received 11 October 2000; Revised manuscript accepted 27 November 2000 Abstract. The distribution patterns, sizes and nucleation sites of aggregated prisms on the outer shell surface were examined in 16 species of Bivalvia and modeled theoretically. Biometric analy- sis shows a negative correlation between the median size and variation of sizes of calcitic simple prisms. In species with aragonitic vertical composite prisms, instead, the density of prisms tends to decrease when their nucleation sites are randomly distributed. Comparison of the results of computer simulations with those of biometric analyses reveals the following: 1) a positive correla- tion between growth rate of prisms and the probability of nucleation for simple prisms, and 2) a limit of the number of nucleations per unit time in vertical composite prisms. Prism size correlates with the growth rate of the entire shell or prisms, and increases as the shell grows faster or prisms grow slower. Key words: biomineralization, bivalves, prismatic structure, shell growth rate, theoretical morpho- logy Introduction The microscopic features of a molluscan shell record cer- tain physiological conditions of the organism at the time the shell is formed. Carbonate minerals within a molluscan shell crystallize and grow under physicochemical conditions controlled by the physiology of the organism. Wada (1972, 1985) reported a seasonal change of shape and size of aragonite crystals in the nacreous layer of such bivalves as Pinctada fucata, Pinna attenuata and Hyriopsis schlegeli. He suggested that the topography of growing crystals may reflect the rate of crystal growth or the degree of supersaturation of the extrapallial fluid. Quantitative analy- sis of the relationship between size and/or shape of crystals and the rate of crystal growth within a shell provides a reli- able basis to understand the ‘paleophysiology’ of fossil or- ganisms. The goal of this study is to clarify the relationship between the geometry of bivalve shell microstructure and the relative growth rate of crystals or of the entire shell. For this pur- pose, the present study focuses on the geometry of the outer shell surface of a simple or vertical composite pris- matic shell layer. Although they differ in the ultrastructure of prisms, those two prismatic structures both consist of many parallel-arrayed columnar units (Carter and Clark, 1985; Carter et al, 1990). Each prism is surrounded and bounded by an organic matrix showing a honeycomb-like appearance on the outer shell surface. For understanding the rule or algorithm forming the geo- metric pattern of shell microstructure, theoretical morphol- ogy is particularly useful (Ubukata, 1997a, b, 2000). Inthe present study, a biometric analysis of size and nucleation sites of prisms in actual shells was carried out in 16 species. Furthermore, a theoretical morphological modeling of growth kinematics of aggregated prisms was attempted, and the computer simulations of that model were compared with the results of the biometric analyses. Biometric analyses Material and methods The outer shell surface of a simple prismatic or vertical composite prismatic outer shell layer was examined in 16 extant species of Bivalvia (Table 1). Each species was rep- resented by a single specimen, except Anodonta woodiana. Most of them were collected at various localities around the Japanese Islands and the Philippines. All the specimens examined are stored at Shizuoka University (SUM). In order to remove the periostracum from the shell com- pletely, the shells examined were bleached for one day. Pieces of them were washed, dried in air, coated with gold using a JEOL JFC-1500 ion coater, and examined with a JEOL JSM-5800LV scanning electron microscope operated at 15kV and interfaced to a computer (Dell Optiplex Gxa EM). In order to analyze size-frequency distribution of prisms, 34 Takao Ubukata Table 1. List of material examined. All specimens have the prefix SUM. 2 Family species locality specimens Pteriidae Pteria penguin (Roding) San Luice, Bathangas, Philippines HM-B-0014 Pinctada maculata (Gould) Iriomote Is., Okinawa, southwest Japan HM-B-0015 Isognomonidae /sognomon perna (Linnaeus) Iriomote Is., Okinawa, southwest Japan HM-B-0016 I. ephippium (Linnaeus) San Luice, Bathangas, Philippines HM-B-0017 Malleidae Malleus regula (Forskäl) Iriomote Is., Okinawa, southwest Japan HM-B-0018 Pinnidae Atrina pectinata (Linnaeus) Ariake, Saga, western Japan HM-B-0019 A. vexillum (Born) Honda Bay, Palawan, Philippines HM-B-0020 Ostreidae Crassostrea gigas (Thunberg) Misaki, Kanagawa, Central Japan HM-B-0021 Margaritiferidae Margaritifera laevis (Haas) Nakagawa, Hokkaido, northern Japan HM-B-0022 Unionidae Inversidens reiniana (Kobelt) Lake Biwa, Shiga, Central Japan HM-B-0023 Unio biwae Kobelt Lake Biwa, Shiga, Central Japan HM-B-0024 Lanceolaria oxyrhyncha (Martens) Lake Biwa, Shiga, Central Japan HM-B-0025 Anodonta woodiana (Lea) Lake Biwa, Shiga, Central Japan HM-B-0026, -0027 A. calypygos Kobelt Lake Biwa, Shiga, Central Japan HM-B-0028 Cristaria plicata (Leach) Lake Biwa, Shiga, Central Japan HM-B-0029 Trigoniidae Neotrigonia margaritacea (Lamarck) French Is., Australia HM-B-0030 EF IE OY. = GE ar TED areas of prisms on the outer shell surface were measured at 6-12 positions along a growth increment on the shell sur- face. An SEM image of the measured portion was saved as a computer bitmap file (Figure 1A). Next, the boundaries between prisms were traced on a NEC PC-9821 V166 per- sonal computer using Microsoft PowerPoint 7.0, and then each prism was colored differently using Justsystem Hanako PhotoRetouch (Figure 1B). Subsequently, the area of each prism was measured by counting pixels. For this counting, a program written in VISUAL BASIC was used on a personal comouter. Since the size-frequency distribution of the areas of prisms is generally right-skewed, the mean and standard de- viation are not suitable for representing the distribution of the areas of prisms. Therefore, the “average” area of prisms on a shell is represented by the median of the areas (5), and the variation of the areas is expressed as a standardized hinge spread (Q.), which is defined as follows: _~G=Q Q, = a (1) where Q, and Q, are the first and third quartiles of the areas of prisms, respectively (Hoel, 1976). S and Q, were both estimated in all shell portions examined. On the outer surface of a vertical composite prismatic shell layer, microgrowth increments are clearly visible within a bleached prism (Figure 2A). In a simple prismatic shell layer, growth increments within a prism are faintly observed on the bleached shell surface (Figure 2B). In either case, Figure 1. A. SEM photograph of the outer shell surface of the vertical composite prismatic layer in Anodonta woodiana (SUM- HM-B0027), scale: 50 um. B. Trace of the outlines of prisms on the SEM image of A. Geometry of bivalve prismatic shell 35 GR TOURS | LIE fet tae aS Dim 22 Wala ir | Y L Figure 2. A. SEM photograph of the outer shell surface of the vertical composite prismatic shell layer in A. woodiana (SUM-HM-B0027) showing clear growth increments within individual prisms, scale: 20 um. B. The simple prismatic layer in Pinctada maculata (SUM-HM- B0015). Arrows indicate nucleation sites, scale: 20 um. C. The SEM image of A. woodiana subdivided into squares, scale: 50 um. D. Distribution of nucleation sites of prisms in C. the center of the circular growth increments is regarded as the nucleation site of the prism. The distribution of nucleation sites of prisms was analyzed in all shell portions in which the areas of prisms were meas- ured. An SEM image was divided into a squared grid of ap- propriate size for each square to include an average of two nucleation sites (Figure 2C). Next, the number of nuclea- tion sites was counted in each square (Figure 2D). The numbers of squares and nucleation sites in each square both define the /; index of Morisita (1959), which represents the nonuniformity of a distribution independent of the size of the quadrates. The /; index is defined as: FT (2) where n is the number of squares, x, is the number of sites in the square i. The value of /; is zero when the distribution is perfectly uniform (Figure 3A). /; increases as the distribu- tion becomes nonuniform (Figure 3B), and it is expected to be one when sites are distributed randomly (Figure 3C). When the distribution of sites is biased considerably, /; has a large value (Figure 3D). The value of /; was estimated in every shell position examined, and the nonuniformity of the distribution of nucleation sites was represented by Js. Results The biometric analyses revealed a negative correlation between $ and Q, in a single specimen of /sognomon perna, and a positive correlation in a single specimen of Malleus regula (Figure 4B). In another species, no correla- tion was observed, though the number of measured portions 36 Takao Ubukata Figure 3. Effect of the spatial distribution pattern on the value of Js. A. Perfectly uniform distribution. including a number of or no dots. Considerably concentrated distribution. within a single valve was not large enough to be significant. On the other hand, when the data from all species are com- bined, Q. is negatively correlated with S at the 0.01 level of significance, both for simple prismatic and vertical composite prismatic shells (Figure 4A-B). This shows that variation in the size of prisms tends to decrease as prism size in- creases. The negative correlation between Q, and S is clear especially in species with a simple prisms (Figure 4B), while the correlation is more or less obscure in species with vertical composite prisms (Figure 4A). A positive correlation between Js and ©, is found only in each specimen of Unio biwae, Anodonta woodiana and Malleus regula (Figure 4C, D). However, when all the data are combined, a positive correlation clearly emerges be- tween /; and ©, in species with vertical composite prisms (Figure 4C). In the case of species with simple prisms, Q. is positively correlated with 7; at the 0.05 level of signifi- cance, though the correlation is graphically unclear (Figure 4D). The positive relationship between /; and ©, indicates that variation of the size of prisms tends to increase with in- creasing randomness of the distribution of nucleation sites. Theoretical morphology Growing circles model To better understand the relationships between geometric features of prisms and the growth rate of each prism and/or of the net growth rate of the entire shell, the growth of aggre- gated prisms was modeled theoretically. C(,=1.07) In this figure, the area is divided into 16 contiguous squares each B. Nearly uniform distribution. C. Random distribution. D. For modeling the process of microscopic growth, observ- ing the initial growth stage of prisms helps understand the nature of crystal growth. Formerly, | reported that many small hemispherical incipient prisms occur on the inner sur- face of the periostracum at the growing margin in species possessing simple and vertical composite prisms (Ubukata, 1994, pl. 2, figs. 1-3). Consequently, a growing-circles model, which represents the growth of aggregated prisms, is introduced here. Growth of a prismatic shell layer consists of three ele- ments, namely, nucleation of prisms, growth of prisms, and accretionary growth of the entire shell. During a single short growth step, the mantle secretes calcium carbonate and nucleation of prisms occurs within the nucleation zone on the inner surface of a periostracum (Figure 5A). The periostracum subsequently secreted by the mantle edge pushes the earlier produced periostracum and its incipient prisms into a more proximal part of the shell (Saleuddin and Petit, 1983). After the prisms pass through the nucleation zone, prisms gradually grow and elongate, forming a colum- nar structure. Let us consider hypothetical shell growth (Figure 5B). The accretionary growth of the entire shell during a short pe- riod of time is reflected in a shift of the nucleation zone. Growth of a prism is represented by the kinematics of an en- larging circle. Potential nucleation sites are distributed uni- formly within a nucleation zone of width h. The distance between the potential nucleation sites can be expressed by d, which represents the size of a unit cell. Growth compo- Geometry of bivalve prismatic shell 37 + M. laevis x I. reiniana o U. biwae x L. grayana + À. woodiana a A. calypygos AC. plicata = N. margaritacea 0 500 1000 + M. laevis x L reiniana o U. biwae x L. grayana + À. woodiana m À. calypygos AC. plicata 0.5 0.7 0.9 I; Figure 4. A-B. Relationship between $ and Q. in actual shells. species with simple prisms. nents are expressed as functions of growth stage s, rather than as functions of time, since the time scale of the growth process is difficult to ascertain in many cases. Over a pe- riod of one growth step, the mantle secretes a periostracum at the shell margin, giving rise to the stippled area in Figure 5B. If the growing margin of the shell shifts downward by d A. Data from species with vertical composite prisms. C-D. Relationship between /; and Q. for species with vertical composite prisms (C) and simple prisms (D). = P. penguin + P. maculata Al. perna + I. ephippium o M. regula m À. pectinata x A. vexillum x C. gigas 0 500 = P. penguin + P. maculata AI. perna + I. ephippium o M. regula m À. pectinata x A. vexillum x C. gigas 0.7 0.9 B. Data from during the step, the growth step is regarded to be a unit in- terval of the growth. Then, the growth step As is generally defined as: AS (3) 38 REES RIRE TETE AR RETIRE PE EE REA B Takao Ubukata Figure 5. A. Schematic diagram of the radial section of the shell and mantle margin of a bivalve showing the position where nucleation of prisms occurs. B. The growing circles model. Black bold points indicate initiation sites of produced prisms, and gray ones potential nu- cleation sites of unborn prisms. During a given growth step As, the shell margin shifts by A/ (stippled area) and the radius of prisms increases by AR (shaded area). where the growing margin of the shell shifts by Al during the growth step. Meanwhile, nucleation of a prism occurs at a potential nu- cleation site within the nucleation zone with a probability of q. Each prism is approximated by a circle which enlarges at a steady rate. During a growth step As, calcium carbonate precipitates along the circumference of each prism giving rise to a new additional rim shown by the shaded portion in Figure 5B, and the radius of each circle increases by AR. As the prisms grow, neighboring prisms come closer and fi- nally in contact with one another, as a result forming a boundary between two prisms. Nucleation of prisms occurs randomly during each growth step, as a result of irregularity of the settling time among prisms. Consequently, a growing circle often occupies the space of nucleation and/or growth of a neighboring ‘unborn’ prism. A newborn prism some- times loses in competition for space between neighboring prisms, and is geometrically terminated (Grigor’ev, 1965). In the growing-circles model, growth of a shell and prisms is generally expressed by the following three parameters: C The dotted line indicates the dorsal limit of the nucleation zone. : the standardized growth rate of prisms, defined as the in- crease of the radius of a prism per growth step, normalized by size of a unit cell (d), P: probability of nucleation per growth step in each potential site, and L: the extent of the nucleation zone standardized by d. Probability of ‘failure’ of nucleation at each site per growth step is expressed as 1- P, and the probability of failure of nucleation during a growth step As (=1-g) is obtained by raising 1-P to As" power. Then, three growth parameters C, P and L are given by: cer Al Now, we can generally define a growth increment during an arbitrary growth step if three parameters C, P and Z are given. (er), L= (4) Computer simulation In order to evaluate the effects of parameters C, P and L on the geometric pattern of prismatic structure, computer simulations were performed for growth of prisms based on Geometry of bivalve prismatic shell 39 | Figure 6. Color display of the growing circles model. Each prism is identified by its color. As C increases, size variation of the prisms also increases. As P or L increases, the median size of prisms tends to decrease. Takao Ubukata 40 © er tT TELL ts 3 S a S 1 = a Co > Figure 7. Three-dimensional block diagrams showing the relationships among growth parameters (C, P, L) and statistics $ (A-C), Q. (D-F) or I; (G-1) on a C-P diagram at L values of 1.2, 3.6 and 7.2. The coordinates of a nucleation site were recorded on each hypothetical prism for The dimension of d is ex- calculating the value of J; in a model. Computer simulations where À is the median of A. pressed as pixels on the computer. In the theoretical model, the area of a hypothetical prism was measured as the number of pixels (4) on the display surface, and both the standardized hinge spread (Q,) and the median of a standardized area of the growing-circles model. hypothetical prisms (S,,) defined beiow were estimated in each model: n VISUAL BASIC by means of a 64-bit workstation computer (Visual Technology owing circles model. iyama A702h). Figure 6 shows a spectrum of geometric patterns of hypo- =" x were carried out with a program written VT-Alpha 600) interfaced with a CRT (I thetical prisms that were made by the g ) 5 ( Geometry of bivalve prismatic shell 41 SOUdIOJUI biometry OUSJOJUI Figure 8. Summary of the biometric analyses and computer simulation. definition of parameters shell growth rate biometry simulation From coupling their results with the consequences from defi- nition of the parameters, a relationship between growth parameters is inferred either in simple prisms (A) or composite prisms (B). Each prism is identified by its color in a theoretical prismatic structure. If Cis large, each prism grows considerably while it passes through the nucleation zone, as a result of the great irregularity of the birth time among prisms. Then, as C increases, the variation of prism size also increases. As P or L increases, the number of prisms increases while their size decreases. Three-dimensional scatter diagrams illustrating the values of $, in relation to C and P, at L=1.2, 3.6 and 7.2 are given in Figure 7A-C, respectively. S.., which means an ‘average’ prism size, seems to be inversely proportional to P, which represents the probability of nucleation. In addition, at the same combination of C and P, 5, tends to increase as L de- creases. This fact indicates that the size of hypothetical prisms increases as the nucleation zone becomes narrow. Figure 7D-F is a series of diagrams showing the relation- ship among four parameters C, P, Q. and L. When Lis large enough, ©. is positively correlated with C (Figure 7E, F). This fact suggests that variation of prism size tends to in- crease with increasing growth rate of prisms (AR in Eq.1) or with decreasing the accretion rate of the entire shell (A/ in Eq.1). When L is small, no clear relationship exists be- tween pairs of C, P and 9. (Figure 7D). In a high C condi- tion, Q. at a given P also tends to increase with increasing L (Figure 7D-F). Figure 7G-I shows the variation of J; in relation to C, P and L. When L is large, /; gradually decreases with increasing P. Since /; represents the degree of nonuniformity, this re- sult indicates that the nucleation sites tend to be distributed uniformly as the probability of nucleation increases. In the high P region, /; at a given C decreases as L increases. This fact indicates that nucleation sites tend to be distributed randomly as the nucleation zone becomes narrower, when the probability of nucleation is high enough. Geometric pattern and growth rate of prismatic shell As mentioned above, the biometric analyses indicated a negative correlation between $ and Q. especially in the species with simple prisms (Figure 4B), and the computer simulation predicted an inverse relationship between P and S,, (Figure 7A-C) and also a positive correlation between C and ©, (Figure 7E, F). To sum up these results, it can be predicted that P increases as C increases for those species with simple prisms (Figure 8A). That is also inferred from the definition of parameters. Since both P and C are in- versely proportional to the growth rate of the entire shell, a positive correlation between C and P is quite reasonable (Figure 8A) if the size-frequency distribution of prisms is con- trolled mainly by the growth rate of the entire shell. Furthermore, even if both the growth rate of prisms and the probability of nucleation reflect the activity of mantle secre- tion, and if the size of prisms is controlled mainly by the ac- tivity of mantle secretion, the positive correlation between C and P is also expected. Coupling of the biometrics and the simulation also sug- gests to us a relationship between the parameters P and L. The biometric analyses demonstrated a positive correlation between /; and Q., especially for species with vertical com- posite prisms as shown in Figure 4C. In addition, the com- puter simulation predicted a positive relationship between L and Q,, and a negative correlation between P and /; as shown in Figure 7G-I. These two results suggest that P possibly decreases as L increases in species with vertical composite prisms (Figure 8B). Actually, an inverse relation- ship between L and P is expected if we assume that the fre- quency of nucleation per unit time interval is fixed. To ascertain this prediction, relationships among simu- lated values of $,, /; and ©, were analyzed for each combina- 42 Takao Ubukata Ss 0.8 0.9 1 1.1 1.2 Figure 9. Relationships between $, and Q, and between 7; and Q, when three parameters satisfy equations as follows: C=aP, P=bIL, where a and b are coefficients. N represents the total number of samples examined, r exhibits the correlation coefficient, and p is the signifi- cance level of the correlation. tion of C, P and L, when a positive correlation between C and P and an inverse relationship between L and P are assumed, as in the following relations: C=@P, jP==, (6) where a and b are coefficients. Computer simulations were performed under the following conditions: 1) a is fixed to 3, and b varies between 0.05 and 0.175, 2) a varies between 1 and 3, and bis fixed to 0.05. Figure 9 is a diagram showing the relationships between S,, and Q, and between Land O.. The results of the simulations under a fixed value of a (=3) and various values of b show a negative correlation between A-B. a=3, 0.05 Say 1 in | ; Pr) ’ nr x roi oe - ni EAN i a, tye dort 1 segeln i | RATER EL DL 0 (GTO ‘SRE Wa Sete Q Er ; ie sadly Aunts ALN Me TROLL IN, À MEN und) y | ae er PT ca toa Se | | u Bun ' nh il ma cee, aa M ‘oh BE i APE M : le Erratum Inthe Contents on the back cover of Vol. 4, No. 2 and the Contents (p. 314, line 14 from bottom) of Vol. 4, No. 4, the name of the first author of the paper by Hasegawa and Hatsugai was misspelled. Read Takashi Hasegawa for Takeshi Hasegawa. 76 A GUIDE FOR PREPARING MANUSCRIPTS PALEONTOLOGICAL RESEARCH is decicated to serving the inter- national community through the dissemination of knowledge in all areas of paleontological research. The journal publishes original and unpublished articles, normally not exceeding 24 pages, and short notes, normally less than 4 pages, without abstract. 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Printing Office, Washington, D. C. Burckle, L. H., 1978: Marine diatoms. /n, Hag, B. U. and Boersma, A. eds., Introduction to Marine Micropaleon- tology, p. 245-266. Elsevier, New York. Fenner, J. and Mikkelsen, N., 1990: Eccene-Oligocene diatoms in the westem Indian Ocean: Taxonomy, stratigraphy, and paleoecology. In, Duncan, R. A., Backman, J., Peterson, L. C., et al, Proceedings of the Ocean Drilling Program, Scientific Results, vol. 115, p. 433-463. College Station, TX (Ocean Drilling Program). Kuramoto, S., 1996: Geophysical investigation for methane hy- drates and the significance of BSR. The Journal of the Geological Soclety of Japan, vol. 11, p. 951-958. (in Japanese with English abstract) Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey (A new find of an ammonoid jaw ap- paratus). Paleontologicheskii Zhurnal 1974, p. 127-129. 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T 240-0067 EIRE 7 AK RRATI-2 BER VASARABNSES ERRESR SX TEL 045-339-3349 (E:8) FAX 045-339-3264 (FREE) E-mail majima@ edhs.ynu.ac.jp EilS&— (TER) BHAI, THAD PacOTSRSE CHA FEU, F 250-0031 / HET A4H499 FEAR) | RA a OH + HERES RE TEL 0465-21-1515 FAX 0465-23-8846 E-mail taru@pat-net.ne.jp fll (TPS) BIYITENTUEF, HEOBHSE lS FILOEN TT, AVYEFAYT ORAS FAIEVÆGOE Hm ALUN ie BA BE AAR BADeSHe TRA HRA Se RAV Ac BAO a’ 7 AN -IRHREREME (7 1 % z AIX) OXÉPEFÉÉDAR DIE HAKRAREER) 1 k 2, a ae ae ee 2001Æ4H23H OH 7113-8622 HAMXAXAHIiA5-16-9 2001 Æ4 A 27H FE 47 BArFTLZEHRHeL » 7 - BW EEE 03-5814-5801 M Æ À M #4 — k MEERE ÉD EE MM. EHER Ee KEE Al fl GF SWNESNRHRLH EM PR 2,500 7176-0012 Brahe RK SEIL201301 Me 03-3991-375 4 ISSN 1342-8144 Paleontological Research BS, #15 ARSDOATIRZIZÄHN, SROSRUA, KARERFIARHN ER SUCENZAMSozH | WNL | Paleontological Research Vol. 5, No. 1 April 30, 2001 THEME ISSUE Morphological Approaches in Paleobiology CONTENTS Takao Ubukata: Morphological approaches in paleobiology :::::::::::::::-:::-::.::...:.......:. 1 Enrico Savazzi: Morphodynamics of an endolithic vermetid gastropod :::::::::::::::-::::::..::.... 3 Kazushige Tanabe, Cyprian Kulicki, Neil H. Landman and Royal H. Mapes: External features of embryonic and early postembryonic shells of a Carboniferous goniatite Vidrioceras from Kansas::-- 13 Takenori Sasaki: Macro-and microstructure of shell and operculum in two Recent gastropod spe- cies, Nerita (Theliostyla) albicilla and Cinnalepeta pulchella (Neritopsina: Neritoidea) ---:----------- 21 Takao Ubukata: Geometric pattern and growth rate of prismatic shell structures in Bivalvia :::::::-:- 33 Richard A. Reyment and W. James Kennedy: Evolution in morphometric traits in North American Collignoniceratinae (Ammonoidea, Cephalopoda)::--:::::----------........................... 45 Enrico Savazzi: A review of symbiosis in the Bivalvia, with special attention to macrosymbiosis ---:-- 55 Erratum: Article by Takashi Hasegawa and Takayuki Hatsugai in Vol. 4, Nos. 2 and 4 rer. 75 IAN INSTITUTION LIBRARIES II 3 9088 01429 0126 | C > | # Paleontological Research ISSN 1342-8144 Formerly Transactions and Proceedings of the Palaeontological Society of Japan Vol. 5 No.2 | June 2001 The Palaeontological Society of Japan Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Jan Bergström (Swedish Museum of Natural History, Stockholm, Sweden), Alan G. Beu (Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato (Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto University, Kyoto, Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain), Roger D.K. 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Phone: (978)750-8400, Fax: (978)750-4744, www.copyright.com Cover: Idealized sketch of Nipponites mirabilis Yabe, a Late Cretaceous (Turonian) nostoceratid ammonite. Various reconstructions of the mode of life of this species have been proposed, because of its curiously meandering shell form (after T. Okamoto, 1988). All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16-9, Bunkyo-ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp/palaeont/ Paleontological Research, vol. 5, no. 2, pp. 77-86, June 29, 2001 © by the Palaeontological Society of Japan Hyotissocameleo, a new Cretaceous oyster subgenus and its shell microstructure, from Wadi Tarfa, Eastern Desert of Egypt MOHAMED ZAKHERA', AHMED KASSAB?’ and KIYOTAKA CHINZEI’ "Department of Geology, Aswan Faculty of Science, South Valley University, Aswan, 81528 Egypt (e-mail: zakhera @ mailcity.com) *Department of Geology, Faculty of Science, Assiut University, Egypt (e-mail: Kassab @ aun.eun "Faculty of Informatics, Osaka Gakuin University, Suita, 564-8511, Japan (e-mail: chinzei @ utc.osaka-gu.ac.jp) Received 1 August 2000; Revised manuscript accepted 1 February 2001 Abstract. On the basis of rib morphology and other characters, Ostrea tissoti Peron and Thomas found in Egyptian Campanian sediments is placed in the genus Cameleolopha Vyalov, 1936 and the subgenus Hyotissocameleo n. subgen. This new subgenus is distinguished from Cameleolopha s.s. in having dichotomous to trichotomous round-crested radial ribs, chomata, a long triangular resilifer and a reniform to comma-shaped adductor muscle scar. The main part of the shell shows regularly foliated and in part cross-foliated structure. Silicification of the original calcitic structure is recognized. recorded. Neither chalky deposits nor chambers are Recrystallization and dolomitization resulting from diagenetic processes are observed. Key words: Cretaceous, Egypt, oyster, shell microstructure, systematics Introduction Intraspecific and interspecific variations in shell morphol- ogy are both very wide in oysters. This results in the occur- rence of confusing homeomorphs at all taxonomic levels in the superfamily and enhances the difficulty of oyster taxon- omy. It is essential to study populations rather than indi- viduals for the reliable and accurate identification of oysters (Kassab and Zakhera, 1994, 2000). Dhondt (1985) noted that Lopha (Actinostreon) Bayle, 1878, Cameleolopha Vyalov, 1936, Nicaisolopha Vyalov, 1936 and Acutostrea Vyalov, 1936, all tend to have homeomorphic shells. Specimens of “Ostrea” tissoti Peron and Thomas treated in this paper, were collected from Upper Cretaceous sedi- ments in the northern part of the Eastern Desert of Egypt (Figure 1). This species has been attributed to the genus Nicaisolopha Vyalov, 1936 (Kuss and Malchus, 1989; Malchus, 1990). We analyzed its morphology and shell mi- crostructure and reached the conclusion that it belongs to the genus Cameleolopha Vyalov, 1936 of the subfamily Lophinae Vyalov, 1936. A new subgenus Hyotissocameleo is proposed to accommodate the morphological differences of the species. Sample preparation To facilitate SEM observations of “Ostrea” tissoti, shells of this species were sectioned in radial, transverse and oblique directions, and parallel to the long axis of the shell. The sectioned surface of each specimen was polished and etched with 0.1 N hydrochloric acid for 20 seconds and then coated with gold for scanning electron microscopy (SEM). Silicified parts and their surroundings have been subjected to microprobe analysis for mineralogical determination. Mode of occurrence and taphonomy A large number of specimens of “Ostrea” tissoti were col- lected from yellowish brown, marly mudstone that appears at several Campanian horizons in the Duwi Formation. The oysters occur as articulated and disarticulated valves, ar- ranged parallel to the bedding plane. No preferred orienta- tion of the valves, convex up or down, was observed. The subequal size and thickness of valves may serve to exhibit the differential effect of storms. Several xenomorphs show the oysters lived on a shelly or hard bottom. Spatulate forms with a small attachment area represent a phenotype that lived on a relatively soft bottom. 78 Mohamed Zakhera et al. St. Paul Z “ % -Dakhl y EI-Da Figure 1. Index map of Wadi Tarfa area, Eastern Desert of Egypt, showing the sampling locality of the Cretaceous oys- ter. The presence of few juvenile shells besides those of adults in the same assemblage is indicative of limited or short episodic storm events that caused the shells to form shell-banks. It is very rare to find other bivalves or macro- scopic fossils. A low rate of accumulation of muddy clastics allowed the valves to be close to each other, sometimes with the right valves adhering to each other, due to later diagenetic processes. Silicification and dolomitization during diagenesis are rec- ognized. Silicification affected the calcium carbonate skele- tal material, as will be mentioned later, as well as the matrix in which the shells were enclosed. Dolomitization affected only the matrix. The limited dolomitization is indicated by the presence of dolomitic rhombs in the cement between the valves or in sediments filling holes in the shell. The holes are thought to have been formed by dissolution of shell ma- terial during the animal's life or shortly after death, but before attachment area relict chomata | dorsal plications (Dp) growth phase furcated peripheral plications (Pp) (i.e. branched out) consolidation of the enclosing sediments. Biometrical remarks A biometric analysis has been made for individuals of shell height more than 23 mm. Smaller specimens are rare in oc- currence. This is probably related to low mortality of the ju- veniles or presence of some kind of post-mortem sorting and fragmentation of smaller shells. Overall morphology and measurements and the internal architecture of the shell of “Ostrea” tissoti are diagrammatically shown in Figures 2, 3 respectively. Although the bivariate scatter diagrams (Figure 4) show weak correlation between pairs of height, length and width, it suggests a large constraint of environmental conditions on shell morphology. For some individuals the dimensions of the adductor mus- cle of their right valve are sometimes larger than those of their left valve (Table 1). This is probably related to left valve convexity, which leads to contraction of the size of the muscle pad. When the difference between length of the ad- ductor muscle pad (Al) and the maximum diameter of the ad- ductor muscle pad (Ad) (Table 1) is small, the muscle (by its long diameter) becomes close to perpendicular to the shell long axis, while a greater difference is reflected in a steeper dip to the point that the muscle becomes obliquely vertical (maximum difference). This difference is proportional to the ratio of shell height and length. Shell microstructure Shell microstructure is important in bivalve systematics (Douvillé, 1936; Newell, 1965; Taylor et al. 1969; Stenzel, 1971; Waller, 1978; Torigoe, 1981; Freneix, 1982; Dhondt, 1985; Carter 1990; Malchus, 1990, Aqrabawi, 1993, Zakhera 1999). The terminology used here follows the descriptive nomenclature outlined by Carter (1990) and Malchus (1990). Stenzel (1971) erected the new genus Hyotissa and called it pycnodonteine on the basis of the presence of a vesicular broad and deep resilifer catachomata 1 cm Figure 2. Measured characters and some morphologic features of Cameleolopha (Hyotissocameleo) tissoti (Peron and Thomas). New oyster subgenus from Egyptian Cretaceous 79 Regularly foliated sheets oriented in accordance with shell architecture Silicified foliated structure Outer regularly foliated layer Regularly foliated layers Adductor myostracum Figure 3. Microstructural framework and distribution of diagenetic effects (silicification and dolomitization) in Cameleolopha (Hyotissocameleo) tissoti (Peron and Thomas) as seen in radial section. Figure 4. Bivariate scatter diagram of Cameleolopha (H.) tissoti (Peron and Thomas) for height (H) against length (L) and height against width (W). a, b for left valves; c, d for right valves. n = number of valves. H, L and W are in mm. wall structure. Malchus (1990) proposed a new family ing method. The shell wall is composed of the following lay- Paleolophidae on the basis of the presence of a strongly ers with different microstructures. lenticular, simply foliated microstructure. The carbonate skeleton of “Ostrea” tissoti in its current state of preservation Prismatic layer is entirely made of calcite, as ascertained by Miegen’s stain- This is the outermost layer of both valves (Figure 5A). It 80 Mohamed Zakhera et al. Table 1. W = Width (valve concavity). of the adductor muscle pad. Dp = No. of dorsal plications (ribs directly connected to the smoothly concentric neanic disc). ripheral plications (ribs at the shell margin which originated as Dp and extended bifurcationally toward the shell margins). and right valves are not of the same individuals. en HL) nr ed Du. En Left valve 1 Ass aa G8 i 2 © 2B 2 39 P35 7 & = i 19 3 wi OF Klo @ 8 2 4 A Ee Be 7 ONE RS 5 66 05 8 © WH 2 0 i 6 7 OG 7 O88 7 8 st) 7 (ep 8 WS O8 KH 19 © 4% 8 O64 3) W © 1 G. 27 9 GB © 5 ® 7 2 8 dE 10 a @ 6 7 8 © © u 11 Mm WF PP B® TH 12 Oo 8 O88 & GS © 2 ie 13 a 7 8 29 105 8S 1, Wo 65° 8 47 7 © © 0 8 15 30 022 G6 8 © WW « 16 oes skh 7S 10S TW 2 17 i 34 0 TT @ 128 9 dE 18 ey SA oe 2 io ay 19 6 GB @ - 2 en ad 20 i 9 A « > 1 21 HD HR © 28 6 6 4 22 36 oo 3 © @ H ı2 23 G 8 © 6 F 8 6 11 24 62 86°) 8 to 1 Measurements (in mm) of Cameleolopha (Hyotissocameleo) tissoti (Peron and Thomas). Abbreviations: H = Height. L = Length. Ah = Height of the adductor muscle pad. Al = Length of the adductor muscle pad. Ad = Maximum diameter Pp = No. of pe- Nos. 1-15 on left ee H OL WI Ane Jal Ad ID RES Right valve 1 ee = eee 4 = GONE 2 cee Vile Are - BE 3 41 431 006 | 290 72 OR 4 298 a7 1 TiS 12 ie 5 35 " 30 #85 65 ih 10 i 6 327 336 78 8 11 Se 7 34 29 6. 85 10 OS 8 28 246 6 86 OMC. dE 9 296 266 8 6 8 oe. 10 28.3 246 06 80% 9 ONE i1 2441494 45 EN 12 . 252.288 658 4 00 CCE 13 31 274 7 11 ee 14 48 305 7 85 11. om: 15 275 247 7. SE RON is composed of prisms, about 9 um long and up to 4.5 um in diameter. The prisms are arranged slightly oblique to the outer surface of the valve. The prismatic layer has been en- countered only in places where the valves are attached to each other and protected from erosion. The preservation of the prismatic layer in this species might be due to burial of the shell in the soft substrate and could not be referred to burial during life as observed in the dorsoventrally elongate oyster Konbostrea (Chinzei, 1986). Foliated layers There are two types of foliated structures. One is the regular type and the other is the crossed-foliated structure, in which the foliated sheets cross each other at a low angle. Regularly foliated structure.—This structure is synony- mous with the simply foliated structure of Malchus (1990). It is built up of long, thin calcitic laths with pointed ends, ar- ranged parallel to one another to form a foliated sheet. The sheets are, in turn, arranged nearly parallel to one another. The orientation of sheets parallels the general trend of shell architecture (Figure 3). The shell architecture is influenced by shell morphology. The regularly foliated structure is pre- dominant in this species, as it constitutes the structural framework of the shell, between the outer prismatic layer => Figure 5. Microstructure of Cameleolopha (Hyotissocameleo) tissoti (Peron and Thomas). of the lower individual (a) below the dark groove (cementing zone of the upper oyster), radial section. C. Herringbone cross-foliated structure, radial section. the umbonal area, radial section. A. The outer prismatic layer (arrow) B. Regularly foliated sheets in D. Differential response of the calcitic struc- ture (low relief, shown as c) and the more resistant secondary silica (high relief, shown as s) to the etching acid; the adductor myostracum is indicated by arrow. E. Spherical unit (s), as a secondary product of recrystallization, with its smooth rounded boundary embedded in a foliated layer (f), parallel section. F. Higher magnification of E, showing the fine homogeneous filling of the spheres. G. Silicified sheets (lower right) normal to the adjacent unit of foliated sheets (upper left) with corroded contact, the circled spots indicate the locations of the microprobe investigations, transverse section. H. Silicified foliated structure with cavities of various shapes, radial section. New oyster subgenus from Egyptian Cretaceous 81 82 Mohamed Zakhera et al. and the innermost regularly foliated layer (Figures 3 and 5B). Herringbone cross-foliated structure. — At low magnifica- tion we observed some layers, each consisting of two sublayers, in the middle part of the shell cross-section (Figure 3). The second-order elements of each sublayer are parallel to one another, inclined at an acute angle to the opposite sublayer. As a result, the sublayers show a regu- lar alternating pattern (Figure 5C). This arrangement of fo- liated sheets was called “herringbone cross-foliated struc- ture” by Malchus (1990). Adductor myostracum The relict of adductor myostracum, ranging from 0.3 to 0.35 mm in thickness, is easily traceable in the specimens examined although it does not retain its original, probably aragonitic, microstructure (Figure 5D). It is composed of coarse-grained calcite. The calcite layer filling the space of the myostracum was fractured and partly replaced by silica mineral (Figures 3 and 5D). Preservation of relicts of origi- nal aragonitic crystallites have been reported, even in Paleozoic fossils (Rollins, 1966; Carter and Tevesz, 1978). In these cases, the aragonite is often preserved within the silicified part of the shell, but we could not find aragonite in this Cretaceous oyster. This suggests that silicification occurred after alteration of the myostracal aragonite to sta- ble calcite. The microstructure of this species does not show any sign of chalky deposits or chambers within its shell. The ab- sence of chalky deposits in oyster of the Lophinae was men- tioned by Torigoe (1981) as one of the characteristic differences between them and members of the Ostreinae, besides the obvious chomata and other characters of the soft parts. Chinzei and Seilacher (1993) reported acciden- tal chambering in the shell of a Recent Lopha, the chambers being filled with dendritic calcite crystals characterized as a “Christmas tree”. Agrabawi (1993) has broadened the char- acteristic morphological range of Nicaisolopha Vyalov, 1936, to include the presence of some empty and chalky lenses within its simply foliated structure. So, the absence of empty lenses and chalky deposits in the species examined here is worth noting. This supports its affinity to the Lophinae as well as its exclusion from genus Nicaisolopha. Diagenetic alteration in shell microstructure Diagenetic alterations in the shell microstructure are ex- pressed by silicified foliated structure and recrystallized spheroidal units. Silicified foliated structure.—A quasihomogeneous struc- ture occupies the inner part of the shell near the umbo. This area tapers toward the anterior, posterior and ventral margins (Figure 3). We can observe the original sheets of foliated structure only in some well-prepared sections (Figure 5H). The homogeneous material is made up of large crystals of a silica mineral detected by microprobe analysis (Figure 6) and SEM observations (Figures 5G, H). The silicification is seen mainly in the inner part of the shell. This is consistent with the view that silicification tends to start in the internal parts of the shell and spread outward (Suzuki et al., 1993). Suzuki et al. (1993) observed that Foliated part Z=20 Ca LK Ca present=150 secs Elapsed=150 secs Vert=5000 counts Disp=1 Range= 10.230 kev Altered part Present=150 secs Elapsed=150 secs Vert=5000 counts Disp=1 AOS 6 3 Range= 10.230 kev Figure 6. Microprobe chart for a spot of foliated structure, showing a predominance of Ca (above) and the altered part showing predominance of Si (below). silicification has been recorded in such bivalves with origi- nally aragonitic shells as glycymerids and venerids, and that it plays a significant role in preserving the original aragonitic structures. This study reveals that silicification can also occur in originally calcitic shells, leading to disordering of the original fabrics of shell microstructure. Spheroidal units. —Many spheroidal units, each 150 to 200 um diameter (Figure 5E), are observed as sporadic spheres in the mid-ventral part of the shell. These spheres are composed of fine (1.1 to 5.5 um) aggregates of calcite that are irregularly shaped and have no preferred orienta- tion. These aggregates have the appearance of a homoge- neous structure (Figure 5F). Figure 5F also shows the sudden change in lath size and arrangement of the calcitic aggregates of this spherical units and its surrounding foli- ated structure. This arrangement with its false homogene- ous appearance is considered to be a secondary product of recrystallization processes. Systematic description (by M. Zakhera) New oyster subgenus from Egyptian Cretaceous 83 Family Ostreidae Rafinesque, 1815 Subfamily Lophinae Vyalov, 1936 Discussion.—As the species seems to be a lophine oys- ter, relevant systematic views are briefly reviewed. Vyalov (1936) established the subfamily Lophinae in the family Ostreidae for the oysters having radially sculptured valves and a plicated or undulating commissure. At the same time, he described the sculpture of Nicaisolopha as vague folds. According to Stenzel (1971), the subfamily Lophinae includes the genus Lopha Roding, 1798 with sub- genera Abruptolopha Vyalov, 1936 and Actinostreon Bayle, 1878; the genera Alectryonella Sacco, 1897, Cameleolopha Vyalov, 1936, Nicaisolopha Vyalov, 1936 and Rastellum Faujas de Saint-Fond, 1799, with subgenus Arctostrea Pe rvinquiere, 1910. Recently, Arctostrea has been treated as a discrete genus (Carter, 1968; Zakhera and Kassab, 1999). In light of Thomson’s (1954) work, Stenzel (1971) consid- ered Alectryonia Fischer de Waldheim, 1808, Dendostrea Swainson, 1835 and Pretostrea Iredale, 1939, as synony- mous of Lopha Röding. Meanwhile Torigoe (1981) mor- phologically discriminated Dendostrea Swainson, 1835 as a separate genus not equivalent to Lopha. Malchus (1990) emphasized the importance of shell microstructure rather than shell morphology in his classification of Mesozoic oys- ters. Consequently, he referred the Cretaceous Nicaisolo- pha, which has a typical lophine form and was formerly assigned to the Lophinae, to his new ostreid subfamily Liostreinae Malchus, 1990. At the same time he erected, on the basis of a characteristic microstructure, another new family, Palaeolophidae, for some other Mesozoic lophine oysters, including Rastellum Faujas de Saint-Fond, 1799, Palaeolopha Malchus, 1990, and Oscillopha Malchus, 1990. He also pointed out that Cameleolopha Vyalov, 1936 could be synonymous with Nicaisolopha Vyalov, 1936. A large sample of the present species, in a very good state of preservation, enables us to examine its morphologi- cal and microstructural characters precisely, to take the ef- fects of homeomorphy into account and determine its proper systematic position. The species has recently been placed in the genus Nicaisolopha Vyalov, 1936. According to Stenzel (1971), Nicaisolopha Vyalov, 1936 is mainly charac- terized by 4-7 radial folds that are not dichotomous; the folds are undulatory, round-crested, and separated by equal, rounded interspaces, on both valves. The genus has no chomata; the adductor muscle imprint is reniform, deeply concave at its dorsal margin; the ligamental area is low and long; the left valve resilifer is shallowly excavated and slightly longer than the bourrelets; and the right valve resilifer is flat, with growth squamae slightly raised in the later growth stage. On the other hand, “Ostrea” tissoti Peron and Thomas has 10-27 clearly dichotomous (sometimes trichotomous) radial ribs, rather than broad radial folds as in Nicaisolopha. This species is smaller in size and it has distinct chomata, which are absent in Nicaisolopha and Cameleolophas.s. Ithas a reniform to comma-shaped adductor muscle imprint and a resilifer deeply excavated in the left valve that is about two times longer than the bourrelets. Compact, closely spaced growth lines, rather than growth squamae, tend to be promi- nent at the end of growth phases. Based on these charac- teristics, | transferred this species from Nicaisolopha to Cameleolopha. Genus Cameloelopha Vyalov, 1936 Type species.—Ostrea cameleo Coquand, 1869. Subgenus Hyotissocameleo Zakhera subgen. nov. Derivation of name.—From a combination of Hyotisso, in reference to its general hyotissinine form and Cameleo, in reference to the genus name Cameleolopha Vyalov, 1936. Type species.—Ostrea tissoti Peron and Thomas, 1891. Diagnosis.—Shell having numerous fine chomata and rel- ict chomata. Resilifer long. Radial ribs narrow with rounded crests tending to start from the umbonal area, and branching dichotomously or trichotomously. Comparison.—Hyotissa Stenzel, 1971 has only a superfi- cial resemblance to Hyotissocameleo in its general shell form. They differ in shell microstructure, shape of adductor scar and the style of ornamentation. Hyotissocameleo dif- fers from Cameleolopha s. s. in the following points: 1. Possession of distinct chomata and relict chomata (not mentioned in the designation of Cameleolopha s.s. in Stenzel, 1971, probably they were very weak and over- looked). 2. Existence of wider range in the number of radial ribs (10 to 27 as peripheral ones), while the number ranges from 12 to 20 in Cameleolopha s.s. 3. In Hyotissocameleo, the radial ribs are straight or weakly undulating in their crest direction, continuous from near the umbo to the commissure as a general trend, and dichotomously or trichotomously branching. In Cameleolo- pha s.s. the radial ribs are, by contrast, curved and diverge outward as the animal grows. 4. The radial ribs in Hyotissocameleo have rounded crests, while these are angular in Cameleolopha s.s. The Cenomanian species Ostrea cameleo Coquand, 1869, the type species of the genus Cameleolopha, can be distinguished from Ostrea tissoti Peron and Thomas by the characters noted above. The material identified as Hyotissa armata (Goldfuss) by Pugaczewska (1977, p.194, pl. 12, figs. 4-5) from Poland, has bifurcated radial ribs, compact and closely spaced growth lines and a high ligamental area with deep resilifer. So it might be included in Hyotissocameleo. Cameleolopha bellaplicata (Conrad) could be attributed to the subgenus Hyotissocameleo as it has the same shell form and style of ornamentation. Cameleolopha pauciplicata Kassab and Mohamed, 1996 has weak chomata and differs from Cameleolopha (Hyotissocameleo) tissoti in having a triangular shell form that is tapering dorsally, has fewer number of angular, curved dichotomous radials and no relict chomata. On the basis of the presence of weak chomata in some species of Cameleolopha s.s., the shape and position of the adductor muscle and the ribbing ornamentation, Cameleolopha s.s. and Hyotissocameleo came from the same ancestor, which was probably “Ostrea” loriolis Coquand and/or “Ostrea” cornuelis Coquand in the Mohamed Zakhera et al. 84 New oyster subgenus from Egyptian Cretaceous 85 Neocomian passing by “Ostrea” complicata Mahmoud in the Albian and Lopha syphax Coquand in the Cenomanian. Cameleolopha (Hyotissocameleo) tissoti (Peron and Thomas, 1891) Figure 7 Ostrea forgemolli Coquand. 1869, p. 25, pl. 2, figs. 9-11 (non figs. 1-8). Ostrea tissoti Peron and Thomas. 1891, p. 196, pl. 24, figs. 1-7. Alectryonia tissoti (Peron and Thomas). Dacqué, 1903, p. 365, pl. 34, figs. 11-12. Lopha tissoti (Peron and Thomas). Fourtau, 1917, p. 54, pl. 5, figs. 1-5; Bandel et al., 1987, pl. 2, figs. 5a, b. Nicaisolopha tissoti (Peron and Thomas). Kuss and Malchus, 1989, p. 902; Malchus, 1990, p. 174, pl. 19, figs. 7-16, 18. Material. —One hundred and twenty-seven specimens, as separated left and right valves, conjoined valves and a few fragments, have been collected from yellowish-brown, marly mudstone of Campanian sediments (Duwi Formation) in Wadi Tarfa of the northern part of Eastern Desert of Egypt. They are housed in the Geological Museum of Aswan University, bearing the prefix KZASW with serial numbers. Measurements— Measurements on complete specimens are listed in Table 1. Description—Shell small in size (up to 5 cm), not strongly inflated, subequivalve. Outline suborbicular to spatulate. No auricles. Left valve (LV) more capacious than right valve (RV). Maximum convexity of valve occurs ventrally, corresponding to position of adductor muscle. Umbo termi- nal, pointed. No umbonal cavities in most individuals while some left valves have a small and very shallow one beneath hinge plate. Chomata well developed both anterodorsally and posterodorsally in vicinity of hinge. Anachomata on right valve long (up to 2 mm), thin, closely arranged, straight and sometimes tilted in same valve. Corresponding catachomata on left valves less pronounced and easily over- looked in some valves. Relict chomata also present. Ligament triangular, high in left valve, low in right valve; straight or posteriorly or anteriorly curved. Ligament area tripartite with a resilifer twice as broad as both bourrelets, or slightly more. Anterior bourrelet longer than posterior one. Adductor muscle imprint comma-shaped in elongated indi- viduals, kidney like in suborbicular ones, and situated posteroventrally. Quenstedt muscle insertions very small, located below resilifer. Attachment area small to medium on left valves with corresponding xenomorphic areas on right valves. Medium-sized attachment area might distort shell shape and sculpture. Neanic part of shell smooth. Both valves have narrow round-crested radial ribs, always at least dichotomous, sometimes trichotomous, especially on shell periphery. They are usually 10-18 in number and may attain 27 in number along shell margin. These radials are crossed by tight nonappressed growth lamellae which are in- termittently prominent. Commissure plicate, interlocking at valve margin. Plication impressed on internal valve surface only for thin-shelled valves. Occurrence.—It seems likely that Cameleolopha (Hyotis- socameleo) tissoti (Peron and Thomas) is a well repre- sented Tethyan species in North Africa. The species was recorded from the same age interval from Tunisia by Peron and Thomas, 1891. It was also recorded from Tripoli by Krumbeck (1906) under the name of Ostrea cfr. forgemoli Coquand. Acknowledgements We would like to express our cordial thanks to T. Setoguchi, H. Maeda, M. Kitamura (all of Kyoto University) and K. Yamaguchi (Shimane University) for their help in many ways during preparation of this paper. Thanks are also extended to N. Malchus (Barcelona University) for sending his articles. Deep appreciation is also due to R. D. K. Thomas (Franklin Marshall College), I. Hayami (Kanagawa University) and K. Tanabe (the University of Tokyo) for their critical reading of the manuscript. References Aqrabawi, M., 1993: Oyster (Bivalvia- Pteriomorphia) of Upper Cretaceous rocks of Jordan. Palaeontology, stratigraphy and comparison with the Upper Cretaceous oyster of Northwest Europe. Mitteilungen aus dem Geologisch- Paläontologischen Institut der Universitat Hamburg, vol. 75, p. 1-135. Bandel, K., Kuss, J. and Malchus, N., 1987: The sediments of Wadi Qena. Journal of African Earth Science, vol. 6, no. 4, p. 427-455. Bayle, E., 1878: Fossiles principaux des terrains: Explication carte geologique France. France Service Carte Geol- ogique, vol. 4, pt. 1, pl. 1-158. Carter, R. 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Paleontological Research, vol. 5, no. 2, pp. 87-100, June 29, 2001 © by the Palaeontological Society of Japan Molecular phylogeny and morphological evolution of laqueoid brachiopods MICHIKO SAITO' and KAZUYOSHI ENDO’ "JSPS Research Fellow in the Department of Earth and Planetary Science, University of Tokyo, Tokyo, 113-0033, Japan (e-mail: michiko@gbs.eps.s.u-tokyo.ac.jp) “Department of Earth and Planetary Science, University of Tokyo, Tokyo, 113-0033, Japan (e-mail: endo @eps.s.u-tokyo.ac.jp) Received 4 September 2000; Revised manuscript accepted 10 March 2001 Abstract. One of the virtues of molecular phylogeny for paleontology is that it can provide inde- pendent and often reliable sets of data from living relatives to test various evolutionary hypotheses inferred from fossil forms. In this study, we present results of a molecular phylogenetic analysis of 12 species of 7 genera belonging to the Laqueoidea, which is the most prolific of the brachiopod superfamilies in the seas around Japan. Onto a phylogenetic tree based on partial sequences (1218 bp) of the mitochondrial cox? gene, we superimposed various external and internal morphologic characters of both juveniles and adults for the taxa examined. The resulting patterns indicated that several lineages experienced paedomorphic evolution in terms of the brachidial (loop) morphology, and that, contrary to some traditional views, certain adult features, such as the bilateral loop, pos- session of a cardinal process, and a rectimarginate commissure, had homoplasious distributions. Examination of the character distributions also revealed, however, that anterior nonbifurcation of the septal pillar at the axial phase is a synapomorphy for a major clade recognized in the molecular analysis. Those results suggest that early loop ontogeny, information about which is still fragmen- tary, would be useful in assessing relationships among laqueoid brachiopods, including certain Mesozoic genera. Key words: Brachiopoda, cytochrome c oxidase | (cox?) gene, Laqueoidea, loop ontogeny, mitochondrial DNA, molecular phylogeny, Recent Introduction The Laqueoidea is one of the larger terebratulide brachio- pod superfamilies, being well represented in both present- day waters and Cenozoic strata of Japan. The members of this superfamily, as well as other superfamilies within the order Terebratulida, are characterized by the possession of calcareous internal skeleton known as the loop which con- tinually undergoes considerable morphological change dur- ing growth before attaining the full adult stage. Due to its complexity and diversity, loop morphology has been the prime tool for the inference of phylogenetic relationships among laqueoid brachiopods and for the classification of long-looped brachiopods generally at various taxonomic levels (Hatai, 1936, 1940; Muir-Wood et al, 1965: MacKinnon, 1993). However, the assumption that loop mor- phology reflects phylogeny has not been fully tested, nor has it been possible to discuss loop evolution without the risk of circular arguments. Ideally phylogenies should be based on characters that are completely independent of the loop. One such would be molecular characteristics. Although molecular trees are only working hypotheses of the true evolutionary relationships of living species, they are useful in providing a basis for discussion of the likely history of a character of interest. In studies of morphological char- acter states, predictions can be made about the probable di- rection of morphological character state transformations and combinations of characters in basal versus derived species, and therefore we can reassess the morphological characters that support the relationships. Because only morphological characters can be used to establish the phylogenetic affini- ties of ancient fossil taxa, the success of a morphological ap- proach for fossils can be increased greatly if patterns of character state evolution are considered in the light of an in- dependently estimated phylogeny. Previous brachiopod molecular systematics have been based on immunological comparisons of shell macromole- cules (Collins et al., 1988; Curry et al., 1991; Endo et al. 1994) and on nucleotide sequence comparisons of nuclear 18S ribosomal ribonucleic acids (rRNA) and mitochondrial 12S rRNA (Cohen and Gawthrop, 1996, 1997; Cohen et al. 1998a, 1998b). The novel overall patterns of loop evolution 88 Michiko Saito and Kazuyoshi Endo that the immunological data indicated were largely unsup- ported by the results of 18S rRNA sequence comparisons (Cohen and Gawthrop, 1997; Cohen et al., 1998b). Besides, it was difficult using the immunological data to resolve rela- tionships among closely related genera. Even with the 18S rRNA data, which offered direct measurements of molecular similarity and thus are more reliable, detailed relationships among the long-looped terebratulide brachiopods remained unclear because the tempo of the 18S rRNA sequence evo- lution was considered too slow to provide adequate varia- tions among these forms (Cohen et al., 1997). Both the nucleotide and amino acid sequences of the mitochondrial cytochrome c oxidase subunit | (cox?) gene turned out to provide a potentially useful framework for shal- lower phylogenies, especially of the relationships among the long-looped laquéoid brachiopods (Saito et al., 2000). In this paper, we report the phylogenetic relationships of laqueoid brachiopods inferred from the cox? sequences and discuss evolutionary processes of the loop and of other mor- phologic characters in laqueoid brachiopods, including some possibly basal Mesozoic fossils. Material and methods Brachiopod samples and molecular phylogenetic analy- sis.— Twenty-seven specimens representing a total of 16 species of terebratulide brachiopods including 11 laqueoid species were available for this study (Table 1). Full details of DNA extraction, amplification and sequenc- ing methods are described in Saito et al. (2000). In brief, cox1 sequences (1218 bp or 406 amino acids in length) were obtained by the direct sequencing of DNA amplification products synthesized by PCR. Amino acid sequences were deduced by reference to the genetic code of brachiopod mitochondrial DNA (Saito et al., 2000). Phylogenetic analy- sis by maximum-parsimony (MP) was performed with PAUP version 3.1 (Swofford, 1993), using the exhaustive search algorithm and equal weighting for all substitutions. To evalu- ate the robustness of the internal branches, 500 bootstrap replications were executed. Analysis by neighbor-joining (NJ; Saitou and Nei, 1997) and maximum-likelihood (ML) were performed with Molphy version 2.3 (Adachi and Hasegawa, 1996a) using the mtREV24-F model (Adachi and Hasegawa, 1996b) for amino acid data and HKY85 model for nucleotide data (Hasegawa et al., 1985), using the “Local Rearrangement Search” option. For each internal branch, a local bootstrap probability (LBP) was estimated by the RELL method (Kishino et al., 1990) with 1000 replica- tions. TreeView version 1.4 (Page, 1996) was used to draw trees. Because of the low intraspecific nucleotide sequence variations in the examined individuals (less than 2%), and the lack of any amino acid difference within each species, one individual was selected to represent the species in the phylogenetic analysis. These representative nucleotide se- quences will appear in the DDBJ nucleotide sequence data- base with the Accession Numbers AB026501 -AB026516 shown in Table 1. For analysis of deeper relationships within the Laqueoidea, both the amino acid and the 1st and 2nd codon Table 1. Specimens used in this study and their sampling locali- ties. Accession numbers refer to the DDBJ nucleotide sequence database. : , Accession Species Locality number Ingroup (Laqueoidea) Laqueus rubellus 1 Sagami Bay AB026501 L. rubellus 2 Sagami Bay L. rubellus 3 Sagami Bay L. blanfordi Otsuchi, Tohoku AB026502 L. quadratus 1 SW of Oshima AB026505 L. quadratus 2 SW of Oshima L. californicus Monterey Bay, AB026503 California, USA L. c. vancouveriensis Monterey Bay, AB026504 California, USA Pictothyris picta 1 off Mishima AB026506 Pictothyris picta 2 Sagami Bay Jolonica nipponica Izu Islands, AB026509 W of Takase Frenulina sanguinolenta 1 Vava'u, Tonga AB026510 F. sanguinolenta 2 Vava’u, Tonga Shimodaia pterygiota 1 Off Shimoda AB026511 S. pterygiota 2 Off Shimoda Terebratalia coreanica 1 Otsuchi, Tohoku AB026508 T. coreanica 2 Wakkanai, Hokkaido Coptothyris grayi 1 Otsuchi, Tohoku AB026507 C. grayi 2 Wakkanai, Hokkaido Outgroup (long-looped forms) Ecnomiosa sp. 1 Izu Islands AB026512 Ecnomiosa sp. 2 Izu Islands Campages sp. SW of Yonejima AB026513 Outgroup (short-looped forms) Terebratulina crossei Otsuchi, Tohoku AB026514 Terebratulina pacifica off Oshima AB026515 Gryphus davidsoni S of Oshima AB026516 position nucleotide sequences were used as data sets. Because little variation was detected in the amino acid se- quences and the 1st and 2nd codon positions of nucleotide sequences, analyses of five Laqueus species were per- formed separately with full lengths of the nucleotide data. Morphological observations. — Observation of juvenile loop morphologies of two laqueoid species, Jolonica nipponica and Terebratalia coreanica, was carried out on a Hitachi S-2400S Scanning Electron Microscope using the methods described by Saito (1996). Molecular phylogeny of laqueoid brachiopods 89 Results Laqueoid relationships Of the terebratulides analyzed, Ecnomiosa sp. and Campages sp. clustered basal to the laqueoids and monophyly of laqueiods were strongly supported (100% LBP, Figure 1). Therefore, we used Ecnomiosa sp. and Campages sp. as the outgroups for the analyses of all laqueoids sampled and within the species of Laqueus. Analyses were also made for an ingroup comprising the 6 genera of Laqueoidea using Laqueus rubellus as outgroup. Analyses based on different tree-building methods (NJ, ML, and MP) and different data sets converged to indicate four possible topologies for the relationships among laqueoid genera (Trees 1 to 4; Figure 2). The results of the molecular phylogenetic analysis are summarized in Figure 3. All resulting trees clearly indicated the basal placement of Laqueus in the Laqueoidea. The local bootstrap support of this node is high in all analysis (99-100%). Among the re- maining six genera (Terebratalia, Coptothyris, Shimodaia, Frenulina, Pictothyris and Jolonica), the close relationship between Jolonica and Pictothyris is consistently supported by high bootstrap values (82-99%). Three of the four trees (Trees 1 to 3) show very similar topologies: the close asso- ciation of Shimodaia-Frenulina-Pictothyris-Jolonica, with Terebratalia and Coptothyris left outside. The positions of Terebratalia and Coptothyris differ slightly in each tree but % = n Oo er z= ey CA ST SS S ao IN ® > à er ® op 2s C = Be La Q > = o © eo, > LER, onic? LEA ca" C3 % Sy. 4 ZAC Ava nee qua d ratus Terebr. € pk Slang, full; 3,4 Org, Pac na III hea a Er LPS SL M T. crosse! \S PIN . on os % cca Nas‘ = d? \& —. % \S Ecnomiosa sp. Campages sp. 0.1 substitutions/site Figure 1. NJ tree based on amino acid sequences. The number at each internal node of the tree indicates the percent- age of node occurrence in 500 bootstrap replicates. they are generally positioned close to one another in the four cladograms. Tree 4 shows early branching of Shimodaia within the 6 genera. The NJ analysis consistently supported Tree 1 (Figure 2). The ML analysis supported Tree 1 or Tree 2, however, the log-likelihood differences among Trees 1 to 3 are very small when amino acid sequences are used. The LBP support for the branch including Terebratalia or Coptothyris is low (19- Tree 1 Laqueus Shimodaia Frenulina Pictothyris Jolonica Terebratalia A Coptothyris Tree 2 Laqueus Terebratalia Coptothyris Shimodaia Frenulina Pictothyris il Jolonica Tree 3 Laqueus Coptothyris Terebratalia Shimodaia Frenulina Pictothyris il Jolonica Tree 4 Laqueus Shimodaia Terebratalia Coptothyris Frenulina Pictothyris i Jolonica Figure 2. Four possible topologies for the relationships among laqueoid genera. 90 Michiko Saito and Kazuyoshi Endo ae i S e A ist+2nd | aa | 1st+2nd ((Laq,((((Pic,Jol),Fre),Shi),(Tra,Cop))),Ecn,Cam) ((Laq,(((((Pic,Jol),Fre),Shi),Cop), Tra)),Ecn,Cam) ), ): a ((Laq,(((((Pic,Jol), Fre), Shi), Tra),Cop)),Ecn,Cam) ((Laq,((((Pic,Jol),Fre),(Tra,Cop)),Shi)),Ecn,Cam) | 226(MP) (Laq,((((Pic,Jol),Fre),Shi),(Tra,Cop) (Laq,(((((Pic,Jol),Fre),Shi),Cop),Tra (Laq,(((((Pic,Jol),Fre),Shi),Tra),Cop (Laq,((((Pic,Jol),Fre),(Tra,Cop)),Shi -2855.96+101.53(ML) | 0.4484 -2863.78+102.18(-7.8) -2859.35+101.83(-3.4) | 0.2996 -2860.59+101.85(-4.6) | 0.2151 [BP nn TE -2183.02+75.88(-3.9) -2179.14+75.71(ML) -2182.64+75.92(-3.5) -2182.97+76.15(-3.8) -1852.65+77.85(-5.5) -1847.14+77.19(ML) -1852.30+78.06(-5.2) Figure 3. Summary of phylogenetic analysis showing the total maximum parsimony tree length, the log-likelihood (+ stan- dard errors) and the bootstrap probabilities for each of the plausible trees. Species name abbreviations: Laq = Laqueus rubellus, Pic = Pictothyris picta, Jol = Jolonica nipponica, Fre = Frenulina sanguinolenta, Shi = Shimodaia pterygiota, Tra = Terebratalia coreanica, Cop = Coptothyris grayi, Ecn = Ecnomiosa sp., Cam = Campages sp. Upper Box: relationships of 7 laqueoid genera with Ecnomiosa sp. and Campages sp. as outgroup. Lower Box: relationships of 6 laqueoid genera (Shimodaia, Frenulina, Jolonica, Pictothyris, Coptothyris, Terebratalia) with Laqueus rubellus as outgroup. aa: amino acid data. 1st + 2nd: nucleotide data of 1st and 2nd codon positions. 66%) in all analyses. The node of the Shimodaia-Frenulina- Pictothyris-Jolonica clade is supported by moderate to high LBPs (70-100%). The MP analysis consistently supported Tree 4 (Figure 2). However, the tree length differences amongst the four trees are only one or two steps (Figure 3). Besides, the Retention Index (RI) for all four topologies was also relatively low (RI = 0.446-0.663), indicating that support for Tree 4 in MP analysis is not strong. When 500 bootstrap replicates were performed, the resulting consensus trees showed either un- resolved trichotomy or the clustering of Shimodaia- Frenulina-Pictothyris-Jolonica with a low BP value (51 - 56%). It is known that the MP analysis is more susceptible to ‘unequal rate effects’ than the NJ or ML analysis, and can lead to a wrong tree when the nucleotide substitution rates greatly vary among different branches (Saitou and Imanishi, 1989). The observed branch length variation among the ingroup taxa (Figure 1) suggests that the tree indicated by the MP analysis may not be reliable. These results lead to the conclusion that any one of Tree 1, 2, or 3 represents the best estimate of the true phylogeny, but the available cox? data being inadequate to make a final determination from among them. More data are needed to resolve the positions of Terebratalia and Coptothyris. Thus, the strict consensus tree of Trees 1 to 3 is proposed as a basis for reconstruction of laqueoid evolution. Figure 4 gives the ML tree of 5 species of the genus Laqueus. Two coherent groups were assessed; (1) the Japanese group (L. rubellus, L. blanfordi, L. quadratus) and (2) the North American group (L. californicus, L. c. vancouveriensis). Each cluster was supported by a high LBP value (100%). The NJ and MP analyses yielded the Ecnomiosa sp. Campages sp. Laqueus rubellus zu L. blanfordi — L. quadratus Er californicus .C.vancouveriensis Figure 4. NJ tree of cox1 nucleotide sequences for the re- lationships within the genus Laqueus. The same topology was obtained by other methods of analysis (MP and ML). The num- bers in the tree represent LBP values. same tree topology. Character state distributions among laqueoid brachio- pods Molecular analyses of cox? sequences, as described above, provide a preliminary framework for the elucidation of phylogenetic relationships among some laqueoid brachio- pods. Onto this molecular framework, we superimposed some morphological characters of those brachiopods, such as shell traits (outline, commissure shape and coloration), adult loop morphology, cardinalia at the annular phase of loop ontogeny, and type of the septal pillar at the axial phase (Figure 5). Details of the selected morphological characters for each species are summarized in Table 2. Loop ontogenetic series of laqueoid species are shown in Figure 6. Figure 7 illustrates hitherto undescribed early loop stages of Terebratalia coreanica and Jolonica nipponica. Molecular phylogeny of laqueoid brachiopods 91 Table 2. Comparisons of selected morphological characters of 7 species of the Laqueoidea. Speci maximum adult loop axial/annular cardinalia cardinal deltidial omament pees size (cm) pattem septal pillar process plates in adult and coloration Laqueus 3.5 bilateral bifurcate inner and outer hinge plates, inner rest- absent conjunct yellowish red with stripes rubellus ing on the median septum Pictothyris picta 3.5 latero- nonbifurcate no inner hinge plates, the cardinalia are present conjunct irregular divaricating stripes of vertical divergent white upon red background Jolonica 2.5 bilacunar nonbifurcate divided hinge plates, with high crural- present conjunct rose-red; some have interven- nipponica bases, hinge-sockets deep ingbands of light yellow mottling. Frenulina 1.5 bilateral nonbifurcate the cardinalia bear disjunct, inner hinge- present disjunct in yellowish brown with short ir- sanguinolenta plates elevated well above the valve small conjunct regular red stripes marginally floor in large Shimodaia 0.7 incomplete nonbifurcate steeply dipping inner hinge plates which absent disjunct red-mottled, with intervening pterygiota annular converge on a low median septum bands of white mottling. Terebratalia 5.9 trabecular bifurcate callus between the socket-ridges joined present conjunct red with layers of white, coreanica to septum rather dull Coptothyris 5.0 teloform bifurcate callus deposit between the socket-ridges present disjunct dull red with radial ribs grayi with which septum unites Shell shape and coloration.— Externally, laqueoid species exhibit great variability in shell size and shape. In this study, it became apparent that the only external shell character that supported phylogenetic relationships was the pattern of shell coloration (Figure 5; top and second row). All the species in the clade of Shimodaia-Frenulina-Pictothyris-Jolonica ex- hibit irregular red stripes or mottling patterns, while shells of others are radially striped (in L. rubellus and T. coreanica) or have uniform coloration (in C. grayi, L. blanfordi, L. quadratus, L. californicus and L. c. vancouveriensis). Other external characters, such as the type of the commissure and completeness of deltidial plates, did not show any system- atic distribution on the molecular phylogenetic tree. Adult loop morphology.—The adult loop pattern is often thought to represent phylogenetic affinity among laqueoid genera, and has been used as a key character to divide the superfamily into families and subfamilies. For example, Laqueus and Frenulina have often been included in the same subfamily (Kingeninae in Richardson, 1975; Laqueinae in Smirnova, 1984) based on their possession of a bilateral adult loop. A close relationship between Pictothyris and Laqueus has also been maintained based on similarity of external characters, as well as adult loop pat- terns; the adult laterovertical loop of Pictothyris has been considered to be at a stage one step more advanced than that of Laqueus (see Thomson, 1927; Hatai, 1940; Smirnova, 1984). However, the results of the molecular study suggest that these interpretations, based on adult loop morphology, are not reliable. The three genera possessing a bilateral, or laterovertical, adult loop (Figure 5; third row; boxed) did not form a clade, supporting the conclusion that a bilateral loop appeared independently in the lineage leading to Laqueus and Frenulina. Cardinalia.— The cardinal process is prominent in most laqueoids; however, species belonging to the genera Laqueus and Shimodaia lack it. The molecular phylogenetic tree indicates that the cardinal process may have been lost at least twice independently (Figure 5; fourth row). S. pterygiota possesses steeply dipping inner hinge plates which converge on a low median septum to form a sessile septalium, comparable to that occurring in young L. rubellus and Laqueus sp. (Saito, 1996; MacKinnon et al., 1997). This resemblance may also have resulted from parallel evolution. Juvenile loop morphology.—At the axial phase of early loop development, when the median septum has a pair of flanges on its posterior part, the anterior part of the median septum bifurcates only in the basal species in the molecular phylogenetic tree, namely, L. rubellus, C. grayi and T. coreanica (Figure 5; fifth row). In all other species that form a Clade, i.e., F. sanguinolenta, P. picta, J. nipponica and S. pterygiota, the septal pillar remain nonbifurcate until the an- nular phase (Figure 5; fifth row; boxed; Saito, 1996; MacKinnon et al., 1997). Although the adult loop patterns may be misleading, early bifurcation of the septal pillar may be a useful character in assessing relationships among laqueoid genera. Discussion Laqueoid classification Taxonomic assignments of the seven laqueoid genera in- vestigated in this paper (Laqueus, Terebratalia, Coptothyris, Shimodaia, Frenulina, Jolonica and Pictothyris) have been controversial for a long time. Opinions as to which genera should be included in the family Laqueidae varied depending on the features that each author conjectured important. For example, Richardson (1973, 1975) considered the families Kingenidae, Macandreviidae and Laqueidae as synony- mous, and proposed uniting them in the family Laqueidae, based on resorption patterns in loop development and the presence of dental plates. In this view, the seven ingroup genera compared in our molecular study are included in the family Laqueidae. Smirnova (1984) defined the Laqueidae as those with a loop of the late frenuliniform stage (i.e. bilacunar loop) or of more advanced stages, in which the connections between the ascending and descending branches remain joined to the septum at all stage. In so doing, she included a number of lower Cretaceous genera in the Laqueidae (Zittellina, Zeuschneria, Tulipina, Waconella), 92 Michiko Saito and Kazuyoshi Endo Laqueus Shimodaia Frenulina Pictothyris Jolonica Coptothyris Terebratalia Figure 5. Morphological characters of laqueoid species superimposed on the molecular phylogenetic tree. The tree topology rep- resents the consensus of the Trees 1, 2, and 3 (cf. Figure 3). Vertical lengths of the branches are arbitrary. Morphological characters (from top to bottom): anterior view of the shells; dorsal view of the shells; adult loop pattern; cardinalia in the annular phase; septal pillar at the axial phase. The drawings are not strictly to scale. The rectimarginate commisure of Laqueus and Pictothyris (top row; boxed) which was previously considered to be evidence uniting these genera, appeared separately in the molecular phylogenetic tree. In the shell external features, the red-white dot coloration (second row; boxed) supports a close relationship between Shimodaia, Frenulina, Pictothyris and Jolonica. Characters such as the adult bilateral or latero-vertical loop pattern (third row; boxed), and the absence of car- dinal process (fourth row; boxed), do not reflect phylogeny. The non-bifurcation of the septal pillar in the axial phase (bottom row; boxed) supports the Shimodaia-Frenulina-Jolonica-Pictothyris clade. Molecular phylogeny of laqueoid brachiopods 93 but excluded certain genera such as Terebratalia and Coptothyris, which exhibited a trabecular or teloform adult loop pattern. Zezina (1984) elevated the subfamily Terebrataliinae (Richardson, 1975) to family status, and dis- tinguished it from the Laqueidae that accommodated such genera as Laqueus, Frenulina, Aldingia, Jolonica, Pictothy- ris, Compsoria and Ecnomiosa. More recently, in summariz- ing the biogeography of articulated brachiopods, Richardson (1997) included 13 living genera in the family Laqueidae (Coptothyris, Jolonica, Pictothyris, Terebratalia, Laqueus, Tythothyris, Simplicithyris, Frenulina, Ecnomiosa, Compso- ria, Aldingia, and two other undiscussed genera), but she did not provide explicit criteria for this classification. Concerning the familial groupings of the seven Recent genera, the following two points can be drawn from the re- sults of our cox? study. Firstly, in the rooted monophyletic cluster of laqueoids that included Terebratalia and Coptothyris, Laqueus branched off first, followed by a trichotomous cluster comprised of Terebratalia , Coptothyris and the subcluster of Shimodaia, Frenulina, Jolonica, and Pictothyris (Figure 5). Therefore, if Terebratalia and Copthothyris are excluded from the Laqueidae and included in the Terebrataliidae, then Laqueus and the remaining four genera (Shimodaia, Frenulina, Jolonica, and Pictothyris) should be accommodated in at least two separate families. A grouping including Laqueus, Shimodaia, Frenulina, Jolonica, and Pictothyris to the exclusion of Terebratalia and Copthothyris would be paraphyletic at best. Secondly, in analyses of all the available terebratulide forms including other than laqueoids, Ecnomiosa branched off outside not only of the laqueoids, but also of the terebratelloids of the Southern Hemisphere (Saito et al., in press). Thus, on molecular grounds, the view of including Ecnomiosa in the family Laqueidae (Richardson, 1997) is not supported. MacKinnon and Gaspard (1996) reported that the descending branches of Ecnomiosa grow only from the crura unlike other long-looped brachiopods, justifying our conclusion based on loop ontogeny. Inclusion of Terebratalia and Coptothyris and exclusion of Ecnomiosa imply that the adult loop morphology alone can- not be used as the prime character to define the Laqueoidea. Instead, presence of a pair of flanges on the septal pillar at the axial stage of loop ontogeny (Figure 8; Saito, 1996) and also the presence of dental plates in the ventral valve appear to be more explicit and better-suited character states to define this superfamily, and are to be in- corporated as such in the diagnosis of the Laqueoidea in the forthcoming revised Treatise (MacKinnon, pers. comm., 2000). Processes of loop evolution Paedomorphosis.— It is evident from comparison of the ontogenetic sequences of the loop morphology (Figure 6) with phylogenetic relationships (Figure 5), that paedomorphic loop evolution occurred at least twice among laqueoids, in the lineages that produced Shimodaia and Jolonica. As discussed in MacKinnon et al. (1997), adult in- dividuals of Shimodaia have an incomplete annular loop, the brachidial ring being incomplete due to resorption of the very narrow transverse band. Adult individuals of Jolonica dis- play a bilacunar loop, a loop with two pairs of connecting bands (lateral and mediovertical), although the width of the bands are different from that in the bilateral loop such as that found in Laqueus. The adult loop phases of both Shimodaia and Jolonica are comparable with juvenile loop phases in other laqueid members, and based on the molecular cladograms (Figure 5), it is more parsimonious to consider the abbreviated ontogenies of Shimodaia and Jolonica as in- dependent synapomorphies. Williams and Hurst (1977) pointed out that the most sig- nificant trend within the post-Paleozoic long-looped terebratulides is the neotenous elimination of later stages of loop ontogeny and a simultaneous simplification of the lophophore. Our results indicate that such complex evolu- tionary processes have indeed been at work in laqueoids. Bifurcation.— As reported by Richardson (1975) and Saito (1996), the loop ontogenies of laqueoid species appear to be roughly the same until the bilacunar phase. However, at the earlier axial phase, characterized by the development of septal flanges, two types of septal pillar can be recognized; in one form of septal pillar the anterior edge becomes bifur- cate whereas in the other form of septal pillar the anterior edge is nonbifurcate (Saito, 1996; Figure 6). In Laqueus sp. (Figures. 8.1, 8.2), T. coreanica (Figure 8.3) and C. grayi (Figure 8.4), the septal pillar is anteriorly bifurcate. On the other hand, Pictothyris sp. (Figure 8.5), Jolonica nipponica (Figure 8.6), F. sanguinolenta (Figure 8.7) and Shimodaia pterygiota (Figure 8.8) all exhibit a nonbifurcate septal pillar and retain remains of projections until the annular phase (Figure. 9.5-9.8). The results of molecular phylogeny indicate paraphyly for those with the bifurcate septal pillar (Figure 5). Thus, bifur- cation is considered as the ancestral state and nonbifurcation a synapomorphy. Two Mesozoic laqueoid genera (Gemmarcula and Trigonosemus) show the anterior bifurcation of the septal pillar at the annular phase (Elliott 1947; Cooper 1955; Steinich 1965). This observation ac- cords well with our contention that anterior bifurcation of the septal pillar is an ancestral character (Figure 5). Evolution of Bilateral Loop.— As discussed earlier, the cox1 results indicated that species with a bilateral adult loop did not form a monophyletic cluster (Figure 5). Two interpre- tations are possible for the evolution of the bilateral loop; one is that parallel evolution occurred, i.e., the bilateral loop evolved twice independently, and the other is that the bilat- eral loop is a plesiomorphic character. The former interpretation tends to be supported by the fact that the two Cretaceous laqueoid genera, Gemmarcula and Trigonosemus, possess a trabecular loop. But the latter in- terpretation becomes equally possible if another genus such as Waconella from the Lower Cretaceous that has a bilateral loop in the adult phase is taken into consideration. Waconella has been considered as one of the members of the ancestral group from which Laqueus is derived, because of the possession of the same type of adult loop, cardinalia and shell shape, as well as the close geographical distribu- tion with other laqueoid genera (Owen, 1970; Smirnova, 1984). Since a deep diversification between Laqueus and other laqueoid genera is inferred from the cox? analysis, this connection between Waconella and Laqueus seems quite 94 Michiko Saito and Kazuyoshi Endo anterior bifurcation of the septum GPPEEEILESEN RT Jolonica * RS S + a = © = = 6 Terebr aa J à ri x bilatera Pe ULLI “trabecular Figure 6. o D © Q 2 ic O © — a) ie) © ® 2 © & — © > = ® D 2 > fe a. Molecular Michiko Saito and Kazuyoshi Endo Molecular phylogeny of laqueoid brachiopods 98 Michiko Saito and Kazuyoshi Endo probable, although the oldest fossil record of Laqueus is middle Miocene (Hatai, 1938). However, the early loop ontogeny of this genus is not reported, and it is not known whether Waconella has the laqueoid character of the flanges at the axial phase. The ancestral state of the laqueoid loop, therefore, cannot be established at present based on the morphology of fossil forms. The relationships of Mesozoic genera to the Cenozoic ones should become clearer when the early loop ontogenies, especially at the axial and annular phases of Mesozoic genera, are further examined. Conclusions Molecular phylogenetic analysis using the coxT gene sug- gests that only a few morphological characters, such as col- oration of the shell and bifurcation of the septal pillar, may be of use in deciphering the phylogenetic relationships of laqueoids. Other characters like cardinalia, external mor- phologies of the shell, notably, adult loop patterns, all of which have previously been considered as taxonomically im- portant, are likely to have undergone a complex evolutionary history, and thus have to be treated with caution when used in taxonomic studies. Reconstruction of the relationships of fossil and Recent terebratulide brachiopods is reliant mainly on the morphol- ogy of hard parts such as the shell, the loop and occasion- ally spicules, i.e., characters that can relatively easily be early loop development, especially of the fossil taxa, would be useful in filling existing gaps in the fossil record of the Laqueoidea and other superfamilies, and in resolving evolu- tionary relationships among fossil and Recent species. In any event, it appears important to evaluate the taxonomic value of each character, by means of molecular phylogeny of living species, to help clarify the phylogenetic history of terebratulide brachiopods and of other organisms in general. Acknowledgements We thank. K. Tanabe, T. Oji (University of Tokyo), and D. |. MacKinnon (University of Canterbury) for their helpful ad- vice. Thanks are due to T. Miyauchi (Wakkanai City), S. Ohta, and late E. Tsuchida (Ocean Research Institute, University of Tokyo), J. Timothy Pennington, and James P. Barry (Monterey Bay Aquarium Research Institute) for kindly providing us with brachiopod samples for this study. Thanks are also due to the staff members of the Misaki Marine Biological Station and the Otsuchi Marine Research Center (University of Tokyo), the Shimoda Marine Research Center (Tsukuba University) and R/V Tansei (Ocean Research Institute, University of Tokyo) for their help in collecting brachiopod samples. This work was partly supported by the grant from the Ministry of Education, Science and Culture of Japan (nos. 08041162 and 11691196), JSPS Research Fellow (no. 3713 in 1998), Fujiwara Natural History Foundation and the Sasakawa Scientific Research Grant preserved in fossils. In addition, careful observations of Figure 6. Loop ontogeny of the living laqueoid genera studied. Drawings are not to scale. The Laqueoidea is characterized by the presence of a pair of flanges (fl) on the septal pillar at the axial phase, and the patterns of ring resorption to produce the bilacunar loop pattern. The route to the bilacunar phase is two-fold; one with (left) and one without (right) anterior bifurcation of the median septum. The common bilacunar pattern for two types and adult patterns are boxed. Note that ontogenetic sequences to the adult patterns do not necessarily correspond with the phylogenetic relationships revealed by the molecular data. Figure 7. Scanning electron microscopic images of early loop morphologies for Terebratalia and Jolonica. 1-4. Terebratalia coreanica. 1. Dorsal view, specimen UMUT RB28050 (L = 0.6 mm: L is the length of the dorsal valve), displays no loop-supporting struc- ture (Prebrachidial phase), x77. 2. A specimen 1.5 mm in length shows septal flanges (Axial phase; oblique view), specimen UMUT RB28051, x63. The anterior part of the septal pillar is bifurcate. Cardinal process begins to develop during this stage. 3. Specimen UMUT RB28052 (L = 2.2 mm) displays a small hood with rudiments of the flanges, x48. Crura extend from areas at the base of the inner socket ridges. 4. Oblique view of the specimen UMUT RB28053 (L = 4.0 mm), showing the ring which retains the rudiments of the flanges (Annular phase), x32. The anterior part of the median septum is bifurcate. The descending branches extend further toward one another, albeit still unconnected. Further development of Terebratalia coreanica as those figured in Saito (1996). 5-8. Jolonica nipponica. 5. Lateral view of the smallest specimen UMUT RB28054 (L = 2.7 mm) displaying flanges (Axial phase), x37. Note that the ventral edge of the septal pillar is non-bifurcate. Crura project out from near the base of each inner socket ridge. 6. Posterodorsal view of the second smallest specimen UMUT RB28055 (L = 3.2 mm), showing a small hood, and small plates (future descending branches) on the septal pillar (Cucullate phase), x30. The crura and the descending branches extend further toward one another. 7-8. Annular phase. 7. Dorsal view of a larger specimen UMUT RB28056, (L = 3.8 mm) showing the annular phase loop and well developed cardinal process, x15. 8. Oblique view of the annular phase loop of the same specimen as in Fig. 8.6, showing the anteriorly spinose septal pillar and the ring with rudiments of the flanges. The septal pillar is spinous, but remains non-bifurcate, x31. Figure 8. Comparison of the median septum morphology at the axial phase among laqueoid species. 1. Laqueus sp. (L = 1.9 mm), specimen UMUT RB28057, x155. 2. Laqueus sp. (L = 1.9 mm), specimen UMUT RB19819, x114. 3: Terebratalia coreanica (L = 2.2 mm), specimen UMUT RB28052, x73. 4. Coptothyris grayi (L = 1.3 mm), specimen 28498 in the collection of Tohoku University, x228. 5. Pictothyris sp. (L = 1.5 mm), specimen UMUT RB19830, x113. 6. Jolonica nipponica (L = 2.7 mm), specimen UMUT RB28054, x63. 7. Frenulina sanguinolenta (L = 2.0 mm), specimen UMUT RB28058, x77. 8. Shimodaia pterygiota (L = 1.54 mm), specimen UMUT RB28059, x120. Figure 9. Comparative views of cardinalia at the annular phase in eight laqueoid species. 1. Laqueus sp. (L = 2.7 mm), specimen UMUT RB19821, x39. 2. Laqueus blanfordi (L = 3.7 mm), specimen UMUT RB28060, x30. 3. Terebratalia coreanica (L = 4.0 mm), specimen UMUT RB28053, x30. 4. Coptothyris grayi (L = 2.3 mm), specimen UMUT RB28061, x31. 5. Pictothyris sp. 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Paleontological Research, vol. 5, no. 2, pp. 101-109, June 29, 2001 © by the Palaeontological Society of Japan The genus Hourcquia (Ammonoidea, Pseudotissotiidae) from the Upper Cretaceous of Hokkaido, Japan: biostratigraphic and biogeographic implications FUMIHISA KAWABE' and YASUNARI SHIGETA’ "Department of Earth Sciences, School of Education, Waseda University, 1-6-1, Nishiwaseda, Shinjuku-ku, Tokyo, 169-8050, Japan (e-mail: fkawabe@mn.waseda.ac.jp) “Department of Geology and Paleontology, National Science Museum, 3-23-1 Hyakunincho, Shinjuku-ku, Tokyo, 169-0073, Japan (e-mail: shigeta@kahaku.go.jp) Received 14 December 2000; Revised manuscript accepted 29 March 2001 Abstract. Stratigraphic and ontogenetic descriptions of three species of Hourcquia from the Cretaceous Yezo Supergroup of Hokkaido, Japan are given for the first time. H. ingens, H. hataii and H. kawashitai occur in the Inoceramus teshioensis Zone of the upper Turonian. Hourcquia evolved and radiated in not only the Tethyan and adjacent areas but also the Northwest Pacific re- gion for a short period in the late Turonian. Key words: Ammonoid, Hokkaido, Hourcquia, late Turonian, Yezo Supergroup Introduction The genus Hourcquia Collignon, 1965 of the family Pseudotissotiidae is characterized by having trapezoidal whorl sections with a rounded keel, coarse ribs, and umbili- cal and ventrolateral tubercles. Species of the genus are Known to occur from the upper Turonian of Madagascar (Collignon, 1965), Venezuela (Renz, 1982), New Mexico, and Texas (Anonymous, 1981). These areas belong to the Tethyan and surrounding realms. Distribution of the present genus extends also to the northwest Pacific region. Five species of Hourcquia are known from the Cretaceous Yezo Supergroup of Hokkaido, Japan (Hashimoto, 1973; Matsumoto and Obata, 1982; Matsumoto and Toshimitsu, 1984; Toshimitsu and Maiya, 1986) and Sakhalin, Russia (Matsumoto, 1970). However, no detailed analysis has been undertaken of their exact Stratigraphic occurrences and variations of shell growth. Further work based on better material is desirable for eluci- dating the ontogeny, biostratigraphy and biogeography of the genus. Recently, we collected several well-preserved specimens referable to Hourcquia from the Cretaceous Yezo Supergroup in the Ikushumbetsu, Miruto and Haboro areas, Hokkaido (Figure 1). In this paper, we describe three spe- cies of the genus and discuss their biostratigraphic and biogeographic implications. Note on stratigraphy The Cretaceous Yezo Supergroup consists of clastic de- posits in a forearc basin. The supergroup is widely distrib- uted in the median zone of Hokkaido (Figure 1) and is divided into four groups, the Lower Yezo, Middle Yezo, Upper Yezo and Hakobuchi groups in ascending order (Okada, 1983). Ikushumbetsu and Miruto areas The Middle and Upper Yezo groups, ranging from the Albian to Santonian stages, are exposed along the Ikushumbetsu and Horomui rivers and their tributaries. The Middle Yezo Group is subdivided into the lower-lying ‘Main Part’ (Matsuno et al, 1964) and the Mikasa Formation (Matsumoto, 1951). The former consists of well-bedded sandstone or laminated mudstone with sandstone intercalations. The latter consists mainly of sandstone ex- hibiting hummocky cross-stratification; it is subdivided into four units, Ta of sandstone, Tb of sandstone to muddy sand- stone, Tc of mudstone, and Td of sandstone to muddy sand- stone, in ascending order (Matsuno et al, 1964). The Upper Yezo Group consists mainly of sandy mudstone in the lower part and homogenous fine-grained mudstone in the 102 Fumihisa Kawabe and Yasunari Shigeta Haboro area Shirochiune-sawaR. I Karasemi-zawa R. Nakafutamata River Sakasa River Haboro River Ganseki-zawa R. Ikushumbetsu and Miruto areas Ikushumbetsu Ikushumbetsu River 140°E 142°E 144°E M Yezo Supergroup Figure 1. Maps of the Haboro and Ikushumbetsu-Miruto areas showing the localities of the Hourcquia species examined. upper part. The group conformably overlies the Mikasa Formation, although the lithologic boundaries are diachronous (Ando, 1990). The specimen assigned to Hourcquia ingens was ob- tained from the lower part of the Upper Yezo Group along the Ganseki-zawa, a stream of the Ikushumbetsu River (Figure 1). This part consists mainly of intensively bioturbated sandy mudstone with intercalations of discon- tinuous sandstone beds, interpreted as distal storm-sheets on the outer shelf. That specimen is associated with Subprionocyclus minimus and Inoceramus teshioensis (Figure 2), which are diagnostic fossils of the upper part of the upper Turonian (see Toshimitsu et al., 1995). The specimen assigned to Hourcquia kawashitai was found in the unit Td of the Mikasa Formation, composed of muddy bioturbated sandstone of inner-shelf type, near the Horomui-gawa Dam of the Miruto area. Ando (1990) refers the stratigraphic level of the locality to the upper Turonian. Haboro area The Middle and Upper Yezo groups, ranging from the mid- dle Turonian to lower Campanian stages, are exposed in the upper reaches of the Haboro River. The Shirochi Formation of the Middle Yezo Group consists of mudstone with intercalations of thin turbidite-sandstone beds (Toshimitsu, 1985). The Upper Yezo Group conformably overlies the Shirochi Formation and consists mainly of mudstone in the lower part and mudstone with intercalations of thin sand- stone in the middle part, while the upper part coarsens up- ward, beginning with mudstone and ending with cross- bedded sandstone (Toshimitsu, 1985). The specimens determined as Hourcquia hataii were ex- tracted from calcareous concretions in float along the Shirochiune-sawa and Karasemi-zawa valleys. The Shirochi Formation of offshore mudstone is distributed in this area and correlated with the Inoceramus teshioensis Zone of the upper Turonian (Toshimitsu and Maiya, 1986). Those specimens were found associated with Subprionocyclus neptuni and Inoceramus teshioensis in the concretions. Repository of specimens.—The specimens described and figured herein are reposited in the National Science Museum, Tokyo with prefix of NSM PM and in the Institute of Geoscience, University of Tsukuba (formerly the Institute of Geology and Mineralogy, Tokyo University of Education) with prefix of TKU. Abbreviations.—D = shell diameter; NSM PCL = National Science Museum, Paleontological Collection Locality. Systematic descriptions Superfamily Acanthoceratoidea Grossouvre, 1894 Family Pseudotissotiidae Hyatt, 1903 Subfamily Hourcquiinae Renz, 1982 Genus Hourcquia Collignon, 1965 Type species.— Hourcquia mirabilis Collignon, 1965. Hourcquia ingens Collignon, 1965 Figures 3a-d, 4, 5 Hourcquia ingens Collignon, 1965, p. 80, pl. 412, figs. 1704-1706, pl. 413, fig. 1708; Matsumoto and Obata, 1982, p. 79, pl. 4, fig. 2a-C. Hourcquia ingens var. antsakoazatensis Collignon, 1965, p. 82, pl. 413, figs. 1707, 1710. Type.—Holotype is the original of Collignon (1965, p. 80, pl. 412, fig. 1704), from the Masiaposa area, Madagascar. Material.—One specimen, NSM PM16159. Shell moder- ately large, 110 mm in D at preserved last septum, and con- sists of only phragmocone. Locality. —NSM PCL 4-15-3 [= Loc. 319 in Futakami (1986)]: a cliff along Ganseki-zawa, a tributary of the Kami- ichino-sawa River in the Ikushumbetsu area, Hokkaido (Figure 1). Description.—Coiling moderately involute, with fairly nar- row and deep umbilicus, rounded umbilical shoulder, and gently convex to nearly vertical umbilical wall. Shell surface ornamented, more distinctively on inner whorls, with prorsiradiate ribs tuberculated at umbilical and ventrolateral shoulders, springing in pairs from umbilical tubercles and in- tercalated shorter ones. Whorl cross-section subtrapezoidal on inner whorls and subtriangular on outer preserved whorl, with maximum breadth at umbilical tuber- cles; rounded keel on fastigate venter, obtuse ventrolateral shoulder. Lateral lobe of suture line asymmetrically divided and deeply incised (Figure 5). Comparison. — The immature shell described as Hourcquia ingens by Matsumoto and Obata (1982, pl. 4, fig. 2a-c) from Hokkaido is more involute than our specimen Ammonoid genus Hourcquia ESS SC ee a She... = oT EEE Oo; _ © : | © a nenenen een eur nen nenn ann ann Fame ne wann nunane nn ne > > =) 2 = > = = FD SS ees e--@-- d : 7) 2| et 3a co Eg. Le ee ne ©. e 58 228 ae o > 2,8 Td: 385 ~ © 8 à © c Ss SS 3 sas Q Q (e) Sie = 010 Y = follies oO 9/2 = £ — +... © |= SEEN — BESITZ TD Se = us ots oo © = = SS ou S248 = © 9 © 2538 Si a8 Ss G © a à 103 ne D à c © ee N NE en ö IE EEE EEE , D ® © .Q 3 7) fe) > = O ® ® -@--------- 4---@-------- LE sms. e an nam © menmsnennensmnusune Er lie ä x & Spas St. aS u N Dane: e © © a o BEN a o = oc Le 8. SEE Se 2... 3 25 ü © © oo = So Go 4 5 © Q 0 > OMS & RS =) E ° SS [2] à = € G £ F 1 Sn DNS DI SS ee En Seer an se 0 ES = 58 eo © We 600 20 SS N DE SoauSs“o DE SSSR Se SS Sek Soe Giese 00 oS s5 à SLT ifs = oO à F CS a, g ® Sorta a 246 ® = S © 3 a SO nS) swe 7) CHÈRE S ca 7) 0” Q D © oO SI OS S Te 5 E 8 = RQ 8 5 2 > 8 c à £ © re) ‘ce Q O a £ O Cc ® O : 2 à ? Bioturbation Bioturbated ms Planar stratification Bedded sandy ms |[____ ? Hummocky cross-strat. Sandy mudstone Zi: ky Sandstone layer Muddy sandstone y — Thick ss bed (>50cm) Sandstone Figure 2. Columnar section and stratigraphic distribution of ammonoids and inoceramids along the Ganseki-zawa Valley, Ikushumbetsu. Hourcquia ingens Collignon occurs from the lower part of the Upper Yezo Group, in association with Subprionocyclus minimus (Hayasaka and Fukada), an index ammonite of the uppermost part of the upper Turonian in Japan. NSM PM16159. The specimens from Madagascar display wide variation in the width of the umbilicus during the imma- ture growth-stage (Collignon, 1965, figs. 1705, 1706, 1708, 1710). Both specimens from Japan are included in the range of variation for the species. Hourcgia ingens closely resembles Hourcquia moralesi Renz (1982, p. 104, pl. 34, fig. 2) from the upper Turonian of Venezuela in having a subtriangular whorl section and bifur- cated, intercalated and projected ribs. The latter is, how- ever, distinguished from the former in retaining the omamentation until a late growth-stage. Occurrence. — Upper Turonian, Coilopoceras requieni- Romaniceras deveriai Zone in Madagascar. Upper part of the upper Turonian, Subprionocyclus minimus Subzone of Inoceramus teshioensis Zone in Hokkaido, Japan. Hourcquia hataii Hashimoto, 1973 Figure 6a-j, 7, 8 Hourquia hataii Hashimoto, 1973, p. 316, pl. 35, text-fig. 2. Type.—Holotype (TKU30492), by monotypy, is the speci- men figured by Hashimoto (1973, pl. 35) from the Nigorikawa River (Loc. 6373114p) in the Teshio area, north- ern Hokkaido. Material.—Two specimens extracted from calcareous con- cretions in float along the Shirochiune-sawa Valley and its small tributary, the Karasemi-zawa Valley, in the Haboro area, Hokkaido are used in the following description: NSM PM16161, from the same place as Loc. RH2096 in Toshimitsu (1985), consists mainly of phragmocone of 70 mm in D at depressed apertual part; NSM PM16162, from the lower course of the Karasemi-zawa Valley, 30 mm in D at compressed apertual part. Description.—Shell displays large ontogenetic variation (Figures 6a-j). In initial growth-stage (D < 5 mm), shells involute with depressed whorl section. Immature (5 < D < 50 mm), shells evolute with, firstly, compressed whorl sec- tion and less ornamentation on shell surface, and, later, subtrapezoidal whorl section, rounded keel, bifurcated and intercalated ribs, and ventral and umbilical bullae. At later growth-stage (D > 50 mm), shell involute with steep umbili- cal wall; whorl cross-section then subtrapezoidal with strong ventrolateral and umbilical tubercles and rounded broad keel. Initial chamber elliptical in median section (Figure 7), 104 Fumihisa Kawabe and Yasunari Shigeta d Figure 3. a-d. Hourcquia ingens Collignon, NSM PM16159, from NSM PCL 4-15-3 [= the locality 319 in Futakami (1986)], Ikushumbetsu, x1.0. c, d. Inner whorls of a and b. Note the change of shell shape and ornamentation through growth. Dimensions for each growth-stage observed at the solid arrows. b; D (shell-diameter) = 104.0 mm, U (umbilical-diameter) = 25.1 mm, B (whorl-breadth) = 53.6 mm, H (whorl-height) = 47.5 mm; d; D = 65.5mm, U = 16.8 mm, H = 27.0 mm. e. Subprinocyclus minimus (Hayasaka and Fukada), NSM PM16163, from NSM PCL 4-15-3, Ikushumbetsu, x1.2. Ammonoid genus Hourcquia 105 iL U 10 mm b Figure 4. Median cross sections of Hourcquia ingens Figure 5. Suture line of Hourcquia ingens Collignon, NSM Collignon, NSM PM16159 showing the ontogenetic change of PM16159. a. Whorl-height = 24.4 mm. b. Whorl-height = 21.3 whorl-shape (right to left). The dashed line shows the inter- mm. Scale bars = 5.0 mm. L; lateral lobe, U; umbilical lobe. costal whorl cross-section. Figure 6. a-j. Hourcquia hataii Hashimoto. a, b. NSM PM16161, from the Shirochiune-sawa River, x1.0. c, d. Inner whorls of a and b (NSM PM16161], x1.0. e, f. NSM PM16162, from the Karasemi-zawa River, x1.0. g, h. Inner whorls of a and b [NSM PM16161], x1.0. i, j. Inner whorls of a and b [NSM PM16161], x1.2. Note the change of shell-shape and ornamentation throughout growth. Dimensions for each growth-stage observed at the solid arrows. c; D = 43.0 mm, U = 8.5 mm, B = 20.2 mm, H = 20.2 mm: g; D = 23.4 mm, U = 5.7 mm, B = 9.2 mm, H = 10.6 mm: j; D = 12.7 mm, U = 2.7 mm, B=5.8 mm, H=6.0 mm. k. Subprionocyclus neptuni (Geinitz), NSM PM16164, associated with NSM PM16162, x1.2. I. Inoceramus teshioensis Nagao and Matsumoto, NSM PM16165, associated with NSM PM16161, x1.2. 106 Fumihisa Kawabe and Yasunari Shigeta 10 mm 10 mm Figure 7. a. Median cross sections of Hourcquia hataii Hashimoto, NSM PM16161 showing the ontogenetic change in whorl-shape (right to left). The dashed line shows the inter- costal whorl cross-section. Angles for whorl-diameter are measured from the base of the caecum (see b). ic; initial cham- ber. b. Early internal shell structure of Hourcquia hataii, NSM PM16161 showing measurements of initial chamber size, ammonitella size, and ammnonitella angle (AA). The ammonitella angle is defined as the angle from the base of the caecum to the primary constriction (pc). measuring 0.46 mm in diameter. Siphuncular tube occupy- ing subcentral position in first whorl and subsequently mov- ing towards ventral side in second whorl. Ammonitella size and angle in median section 0.78 mm and 303° respectively. Lateral lobe of suture line asymmetrically divided and deeply incised (Figure 8). Comparison. — Hourcquia hataii closely resembles Hourcquia mirabilis from Madagascar (Collignon 1965, p. 77, fig. 1703) and H. krausei, monotypic, from Venezuela (Renz 1982, p. 104, pl. 34, fig. 1) in respect of the strong U L E À U L E 9) br CU ML E Ce U HL TE d — EUR G & Qc Figure 8. Suture line of Hourcquia hataii Hashimoto, NSM PM16161. a. Whorl-height = 20.5 mm. b. Whorl-height = 14.1 mm. c. Whorl-height = 10.3 mm. d. Whorl-height = 5.7 mm. e. Whorl-height = 4.0 mm. Scale bars for a-c = 5.0 mm, for d, e= 1.0 mm. E; external lobe, L; lateral lobe, U; umbilical lobe. ventrolateral and umbilical tubercles on the subtrapezoidal whorl in the later growth-stage. The latter two are distin- guished from the former in having a concavely impressed spiral band on the flank. Discussion.—The monotypic holotype of Hourcquia hataii was extracted from a calcareous concretion in float without any age-diagnostic information; Hashimoto (1973) inter- preted the horizon as being Coniacian. We found two specimens referable to H. hataii together with Inoceramus teshioensis and Subprionocyclus neptuni (Figure 6k, I) in the same concretions. Since the latter is diagnostic of the Upper Turonian, we revise the stratigraphic occurrence of the present species to within the Upper Turonian. Occurrence.— Upper Turonian, /noceramus teshioensis Zone, Hokkaido, Japan. Hourcquia kawashitai Matsumoto and Toshimitsu, 1984 Figures 9-12 Hourquia kawashitai Matsumoto and Toshimitsu, 1984, p. 233, pl. 32, figs. 1, 2; pl. 33, figs. 1-3; pl. 34, fig. 2, text-figs. 2, 3. Type. — Holotype, YKC.57-6-20-E, Y. Kawashita’s Collection, is the original of Matsumoto and Toshimitsu (1984, pl. 32, fig. 1), from the Karasemi-zawa Valley in the Haboro area, northwestern Hokkaido (Figure 1). Material.—One specimen, NSM PM16160. Immature Ammonoid genus Hourcquia 107 Figure 9. Hourcquia kawashitai Matsumoto and Toshimitsu, NSM PM16160, from NSM PCL 4-14-15, Miruto, x1.0. c-f. Inner whorls of a and b. Dimensions for each growth stage observed at the solid arrows. a; D = 81.3 mm, U = 9.2 mm, B = 28.5 mm, H = 40.5 mm: c; D = 49.7 mm, U = 4.9 mm, B = 19.0 mm, H = 25.0 mm: e; D = 25.1 mm, U = 2.9 mm, B= 9.8 mm, H= 13.1 mm. The white arrow shows the location of the last suture-line. shell, 82 mm in D, and consists of phragmocone and long body chamber occupying about 270° in spiral length, without complete aperture. Locality—NSM PCL 4-14-15: a cliff about 2 km north of the Horomui-gawa Dam in the Miruto area, Hokkaido (Figure 1). Description.—Coiling very involute, with narrow and deep umbilicus, rounded umbilical shoulder and nearly vertical umbilical wall. Shell surface ornamented with prorsiradiate ribs tuberculated at umbilical and ventrolateral shoulders, springing in pairs from umbilical tubercles and with interca- lated shorter ones. Ribs weaker on flank. Whorl cross- section high subtrigonal with maximum breadth at umbilical tubercles, rounded keel on roof-shaped venter, obtuse ventrolateral shoulder. Initial chamber elliptical in median section, measuring 0.42 mm in diameter. Caecum subelliptical in lateral view (Figure 11). Prosiphon not preserved. Siphuncular tube occupies subcentral position in first whorl and gradually moves toward ventral side in second whorl. Ammonitella size and angle in median section, 0.89 mm and 310°, re- spectively. Lateral lobe of suture line asymmetrically di- vided and deeply incised (Figure 12). Comparison.—Although the specimen NSM PM16159 is an immature shell, the shape and ornament are essentially the same as those of the inner whorl of Hourcquia kawashitai (Matsumoto and Toshimitsu, 1984; pl.32, fig.2). Occurrence.— Upper Turonian, Inoceramus teshioensis 108 Fumihisa Kawabe and Yasunari Shigeta Figure 10. Median cross sections of Hourcquia kawashitai Matsumoto and Toshimitsu, NSM PM16160 showing the ontogenetic change in whorl-shape (right to left). The dashed line shows the intercostal whorl cross-section. Figure 11. SEM micrograph of the early internal shell structure of Hourcquia kawashitai Matsumoto and Toshimitsu, NSM PM16160, in median section. The arrow shows the pri- mary constriction. Scale bar=0.5 mm. See Figure 7-B for measurements of initial chamber size, ammonitella size, and ammnonitella angle. Zone in Hokkaido, Japan. Discussion Five species of Hourcuia, H. mirabilis, H. ingens, H. Pacifica, H. hatai and H. kawashitai, have been described up to now from the Cretaceous of Hokkaido and Sakhalin. Almost all species were not collected in situ but from cal- cargous concretions in float without specific stratigraphic evi- dence. Previous authors thought that the biostratigraphic horizon of H. hataii was the Coniacian, that of H. pacifica was the upper Turonian to Coniacian, and that of the other Figure 12. Suture line of Hourcquia kawashitai Matsumoto and Toshimitsu, NSM PM16160. a. Whorl height = 28.6 mm. b. Whorl height = 14.0 mm. c. Whorl height = 9.3 mm. Scale bars for a, b = 5.0 mm, forc=1.0 mm. E; external lobe, L; lat- eral lobe, U; umbilical lobe. three species was the upper Turonian. In this paper, we have determined the precise biostratigraphic horizons of the following three species. H. ingens occurred in the upper part of the upper Turonian associated with Subprionocyclus minimus, H. hataii occurred in the Upper Turonian with S. neptuni, and H. kawashitai was also obtained from the upper Turonian. In the Tethyan and adjacent regions, Hourcquia radiated only during the late Turonian; H. mirabilis and H. ingens in Madagascar (Collignon, 1965), H. krausi and H. moralesi in Venezuela (Renz, 1982), H. cf. mirabilis in New Mexico and Trans-Pecos Texas (Anonymous, 1981). In consequence the genus Hourcquia seems to be useful for inter-regional biostratigraphic correlation. In Hokkaido and Sakhalin, it is generally considered that the ammonoid fauna is characteristic of the North Pacific bio-province, different from both the Tethyan and Boreal provinces, during the post-Albian. However, the occurrence of Hourcquia species in the Yezo Supergroup, including two pandemic ones, H. mirabilis and H. ingens and three en- demic ones, H. pacifica, H. hataii, and H. kawashitai, dem- onstrates that this genus evolved and radiated in not only the Tethyan and adjacent regions but also possibly in the northwest Pacific region for a short period in the late Turonian. In a similar manner, the Tethyan vascoceratids entered into the Yezo forearc basin for a short period in the early Turonian (Matsumoto, 1973; Matsumoto, 1978; Matsumoto and Muramoto, 1978). The oxygen isotope evi- dence suggests two cycles of rapid warming during earliest Turonian and middle to late Turonian time (Jenkyns et al, 1994; Clarke and Jenkyns, 1999). The extended distribu- tions of Hourcquia and vascoceratids seem to have been in- fluenced by episodic global climatic optimums. Ammonoid genus Hourcquia Acknowledgments We express our sincere gratitude to R. A. Reyment (Swedish Museum of Natural History, Stockholm) and J. W. Haggart (Geological Survey of Canada, Vancouver) for criti- cal reading of the manuscript. H. Hirano (Waseda University, Tokyo), S. Toshimitsu (Geological Survey of Japan, Tsukuba) and anonymous reviewers provided helpful suggestions and information. We are much indebted to K. Hasegawa (Mikasa) for providing the specimen, NSM PM16160. This study was financially supported by the Grant-in-Aid for JSPS Research Fellow (No. 6583 in 1998- 1999) from the Ministry of Education, Science, Sports and Culture, Japan to F. Kawabe and by a grant from the Fujiwara Natural History Foundation (1999) to F. Kawabe and Y. Shigeta. References Ando, H., 1990: Stratigraphy and shallow marine sedimentary facies of the Mikasa Formation, Middle Yezo Group (Upper Cretaceous). The Journal of the Geological Society of Japan, vol. 96, p. 279-295, pls. 1-4. 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Memoirs of the Faculty of Science, Kyushu University, Series D, Geology, vol. 20, p. 305-317, pls. 48-49. Matsumoto, T., 1973: Vascoceratid ammonites from the Turonian of Hokkaido. Transactions and Proceedings of the Palaeontological Society of Japan, New series, no. 89, p. 27-41, pl. 8. Matsumoto, T., 1978: A record of Neoptychites from the Cretaceous of Hokkaido. Recent Researches in Geolo- gy, Delhi, vol.4, p. 196-207. Matsumoto, T. and Muramoto, K., 1978: Further notes on vascoceratid ammonites from Hokkaido. Transactions and Proceedings of the Palaeontological Society of Japan , New series, no. 109, p. 280-292, pl. 39. Matsumoto T. and Obata, I., 1982: Some interesting acanthocerataceans from Hokkaido. Bulletin of the National Science Museum, Tokyo, Series C, vol. 8, p. 67-92. Matsumoto, T. and Toshimitsu, S., 1984: On the systematic positions of the two ammonite genera Hourcquia Collignon, 1965 and Pseudobarroisiceras Shimizu, 1932. Memoirs of the Faculty of Science, Kyushu University, Series D, Geology, vol. 25, p. 229-246. Matsuno, H., Tanaka, K., Mizuno, A. and Ishida, M., 1964: Geological sheet map “lwamizawa”, scale 1:50,000, and its explanatory text. Hokkaido Development Agency, 168 p. (in Japanese with English abstract) Okada, H., 1983. Collision orogenesis sedimentation in Hokkaido. /n, Hashimoto, T. and Ueda, S. eds. Accretion Tectonics in the Circum-Pacific Regions, p. 107-122. Terra Scientific Publishing Company, Tokyo. Renz, O., 1982: The Cretaceous ammonites of Venezuela, 132 p., 40 pls., Maraven, Caracas. Toshimitsu, S., 1985: Biostratigraphy and depositional facies of the Cretaceous in the upper reaches of the Haboro River, Hokkaido. The Journal of the Geological Society of Japan, vol. 91, p. 599-618. (in Japanese with English abstract) Toshimitsu, S. and Maiya, S., 1986: Integrated inoceramid- foraminiferal biostratigraphy of the Upper Cretaceous of northwestern Hokkaido, Japan. Cretaceous Research, vol. 7, p. 307-326. Toshimitsu, S., Matsumoto, T., Noda, M., Nishida, T. and Maiya, S., 1995: Towards an integrated mega-, micro- and magneto-stratigraphy of the Upper Cretaceous in Japan. The Journal of the Geological Society of Japan, vol. 101, p. 19-29. (in Japanese with English abstract) 109 Paleontological Research, vol. 5, no. 2, pp. 111-114, June 29, 2001 © by the Palaeontological Society of Japan Some additional Wuchiapingian (Late Permian) ammonoids from the Southern Kitakami Massif, Northeast Japan MASAYUKI EHIRO Institute of Geology and Paleontology, Graduate School of Sciences, Tohoku University, Sendai, 980-8578, Japan (e-mail: ehiro@mail.cc.tohoku.ac.jp) Received 28 December 2000; Revised manuscript accepted 29 March 2001 Abstract. Permian ammonoids, Dzhulfoceras cf. furnishi, D. sp. and Stacheoceras? sp., are de- scribed from the Southern Kitakami Massif, Northeast Japan. The first two and the last were col- lected from the Lower and Middle Toyoman Series, respectively. The occurrence of Dzhulfoceras supports the previous correlation of the Lower Toyoman Series with the Wuchiapingian (Dzhulfian). This occurrence of Dzhulfoceras is the first record of the genus outside the Middle East and sup- ports the conclusion that a close paleobiogeographic relationship existed between the Middle East and the Southern Kitakami in Late Permian time. Key words: Dzhulfoceras, Equatorial Tethyan Province, Southern Kitakami Massif, Stacheoceras, Upper Permian, Wuchiapingian Introduction Fossils including ammonoids are rare in the black shale of the Upper Permian Toyoman Series in the Southern Kitakami Massif, Northeast Japan. However, the few ammonoids that have been recovered are useful biostratigraphic tools for dating the Toyoman formations and for estimating the paleobiogeographic situation of the mas- sif. To date, sixteen species belonging to 11 genera of ammonoids have been described from the Toyoman Series (Bando, 1975; Ehiro, 1996; Ehiro and Bando, 1985; Ehiro et al., 1986; Murata and Bando, 1975). The genera are Pseudogastrioceras, Stacheoceras, Timorites, Cyclolobus, Eumedlicottia, Neogeoceras, Araxoceras, Vescotoceras, Eusanyangites, Xenodiscus and Paratirolites. Based on these ammonoids, especially those belonging to the Cyclolobidae, Araxoceratidae, Xenodiscidae and Dzhulfi- tidae, the Lower to Middle and Upper Toyoman Series have been correlated with the Wuchiapingian (Dzhulfian) and Changhsingian (Dorashamian), respectively (Ehiro and Bando, 1985; Ehiro et al, 1986; Ehiro, 1996). This ammonoid fauna is typical of the Equatorial Tethyan Province (Ehiro, 1997) and closely related to the Late Permian ammonoid faunas of South China and the Middle East. In this paper two new occurrences of Late Permian ammonoids are described. Two specimens were collected from the Suenosaki Formation in the Utatsu area, and one specimen came from the Toyoma Formation in the Motoyoshi area (Figure 1). Both occurrences indicate the Wuchiapingian horizon. Late Permian ammonoids from Utatsu and Motoyoshi In the Utatsu area, the uppermost Kanokuran (Middle Permian) to Middle Toyoman Suenosaki and Upper Toyoman Tanoura Formations are widely distributed (Ehiro and Bando, 1985). Two specimens of ammonoids de- scribed here as Dzhulfoceras cf. furnishi Ruzhencev and D. sp. were found in a calcareous nodule collected from a shale bed exposed along the Ishihama coast (see locality 3 of Ehiro and Bando, 1985). The fossil horizon belongs to the lower part of the Suenosaki Formation, which is correlated with the lower part of the Lower Toyoman Series. From this locality Ehiro and Bando (1985) and Ehiro et al. (1986) de- scribed some Wuchiapingian ammonoids, such as Pseudogastrioceras sp., Stacheoceras iwaizakiense Mabuti, Timorites intermedius (Wanner), Araxoceras cf. rotoides Ruzhencev, A. sp., Vescotoceras japonicum (Bando and Ehiro) and V. sp., and correlated the lower part of the Suenosaki Formation with the Wuchiapingian (Dzhulfian). Dzhulfoceras belongs to the family Araxoceratidae and is indicative of Wuchiapingian age, although the genus ranges up to the Changhsingian. To date, three species of Dzhulfoceras have been described from the Upper Dzhulfian (Vedioceras bed) in Transcaucasia (D. furnishi Ruzhencev, 112 Masayuki Ehiro N X Maehama & MOTOYOSHI | 141 | 5! . p 2 73 page 4 WEE | BA :Kitakami — Massif Figure 1. Map showing the fossil localities and geology of the southern part of the Southern Kitakami Massif. 1. Permian, 2. Triassic, 3. Jurassic, 4. Lower Cretaceous, 5. Early Cretaceous granitic rocks, 6. ammonoid localities. D. inflatum Ruzhencev and D. paulum Ruzhencev; Ruzhencev, 1962, 1963) and from the Dorashamian (Unit 7 of the Hambast Formation) in Abadeh, Central Iran (D. furnishf, Bando, 1979). The Ishihama specimens of Dzhulfoceras described herein are the first recovery of the genus outside the Middle East. The Dzhulfoceras speci- mens show a close faunal relationship, in association with the previously reported ammonoids, to those of the Dzhulfian. The presence of Dzhulfoceras in South Kitakami supports the conclusion that the lower Suenosaki Formation is correlatable with the Wuchiapingian (Dzhulfian) (Ehiro and Bando, 1985), and that the South Kitakami region belonged to the Equatorial Tethyan ammonoid province during Permian time (Ehiro, 1997). At the Maehama coast of the Motoyoshi area the Toyoma Formation consists mainly of massive black shale with a subordinate amount of lenticular thin sandstone beds. It is overlain unconformably by the Lower Triassic Hiraiso Formation. Murata and Bando (1975) reported an araxoceratid ammonoid, Araxoceras cf. kiangsiense Chao, from the black shale about 15 m below the boundary be- tween the Toyoma and Hiraiso Formations. They corre- lated this part of the stratigraphic succession, which belongs to the Middle Toyoman Series based on the associated molluscan fossils, with the Dzhulfian. Later Zakharov (1986) compared this species to Eusanyangites bandoi Zakharov and Pavlov, which was recovered from the Wuchiapingian bed of Primorye, Far East Russia (Zakharov and Pavlov, 1986). The present ammonoid specimen described here as Stacheoceras? sp. was collected from black shale exposed on the Maehama coast, at the same locality as Murata and Bando (1975). Stacheoceras is a long-ranging Permian genus and provides less precision in _ stratigraphic correlations. Systematic descriptions Superfamily Cycloloboidea Zittel, 1895 Family Vidrioceratidae Plummer and Scot, 1937 Genus Stacheoceras Gemmellaro, 1887 Type species.— Stacheoceras mediterraneum Gemmel- laro, 1887. Stacheoceras? sp. Figure 2.3a-d Material.—A relatively small incomplete specimen, IGPS coll. cat. no. 108551, collected from the Toyoma Formation exposed on the Maehama coast, Motoyoshi-cho, Motoyoshi- gun, Miyagi Prefecture. Remarks.—The specimen consists of about one half volution of the body chamber and fragments of phragmocone with an estimated diameter of 21 mm. The involute conch with a narrow umbilicus is subglobular (Figure 2.3a-c). At the maximum estimated diameter the height, width and umbilical diameter are about 12.0, 15.5 and 5.0 mm, respectively. The surface of the body cham- ber bears fine but prominent transverse ribs with intercalary ones, which start at 1/3 height of the whorl. The body chamber is also marked by rather prominent transverse con- strictions, which are nearly straight. The suture lines, only partly preserved and displaying parts of the lateral suture, consist of more than three pairs of rounded saddles and trifid lobes (Figure 2.3d). Their exact positions with respect to the venter are unknown, because they are on a fragmental phragmocone. Involute subglobular shells with transverse ribs are char- acteristic for some genera which belong to the families in- cluding and not limited to the Marathonitidae, Perrinitidae, Vidrioceratidae and Cyclolobidae. Judging from the shape of the trifid lateral lobe of the suture, it could belong to Waagenia or more likely Stacheoceras. The present speci- Permian ammonoids from Kitakami 113 Figure 2. 1. Dzhulfoceras cf. furnishi Ruzhencev, IGPS coll. cat. no. 108552, lateral (1a) and ventral (1b) views, x2.5, and suture line (1c), x7. 2. Dzhulfoceras sp., IGPS coll cat. no. 108553, lateral (2a) and ventral (2b) views, x2.5, and suture line (2c), x7. 3. Stacheoceras? sp., IGPS coll. cat. no. 108551, lateral (3a), ventral (3b) and dorsal (3c) views, x1.6, and a part of the lateral suture line, x8. Dotted lines show estimated conch outlines. men is, however, too poorly preserved to identify it with con- fidence at the generic level and therefore the specimen is placed in Stacheoceras with strong reservations. Superfamily Otoceratoidea Hyatt, 1900 Family Araxoceratidae Ruzhencev, 1959 Genus Dzhulfoceras Ruzhencev, 1962 Type species.—Dzhulfoceras furnishi Ruzhencev, 1962. Dzhulfoceras cf. furnishi Ruzhencev, 1962 Figure 2.1a-c Compare.— Dzhulfoceras furnishi Ruzhencev, 1962, p. 99, pl. 5, figs. 1a, b, text- fig. 8a; Bando, 1979, p. 128, pl. 6, figs. 8a-c, 9a, b, text-fig. 6A. Material.—A partly complete phragmocone, IGPS coll. cat. no. 108552, collected from the lower part of the Suenosaki Formation exposed along the Ishihama coast, Utatsu-cho, Motoyoshi-gun, Miyagi Prefecture. Descriptive remarks.—The specimen is a deformed phragmocone with an estimated diameter of 14 mm. The conch is involute and thinly discoidal, with a pinpoint umbili- cus (Figure 2.1a, b). The compressed shell has nearly par- allel, but slightly convex flanks. The venter and ventrolateral shoulders are rounded. No ornamentation is observed on the shell surface. The ceratitic suture consists of a moderately wide ventral lobe, large and high rounded ventrolateral saddle, large and deep first lateral lobe, moder- ately high second lateral saddle, relatively small and shallow second lateral lobe and four pairs of small rounded saddles and pointed lobes (Figure 2.1c). Only the first and second lateral lobes are denticulate. Based on the shell form, especially on the rounded shape of its ventrolateral part, and the form of the suture, the pre- sent specimen can be assigned with confidence to Dzhulfoceras. Among the species of the genus Dzhulfo- ceras it most closely resembles D. furnishi Ruzhencev in having nearly parallel sides of the shell. The present specimen is not sufficiently well preserved to allow a confi- dent species assignment. Dzhulfoceras sp. Figure 2.2a-c Material.—An incomplete phragmocone, IGPS coll. cat. no. 108553, collected from the lower part of the Suenosaki Formation exposed on the Ishihama coast, Utatsu-cho, Motoyoshi-gun, Miyagi Prefecture. Remarks. — The specimen is a small fragment of phragmocone of about one half volution with an estimated diameter of 14mm. The conch is compressed, involute and thinly discoidal. The slightly convex sides are subparallel, and the venter and the ventral shoulders are rounded (Figure 2.2a, b). No ornamentation is observed on the shell surface. The suture line is partly preserved on the lateral part of the conch. It consists of a large and high rounded ventrolateral saddle, large and deep serrated first lateral lobe, moderately high rounded second lateral saddle, rela- tively small and shallow serrated second lateral lobe and more than two pairs of small rounded saddles and pointed 114 lobes (Figure 2.2c). the shell shape and sutural outline. cause of the poor state of preservation. References Bando, Y., 1975: On some Permian Medlicottidae from the Toyoma Formation in the Kitakami Massif. Memoir of the Faculty of Education, Kagawa University, Series Il, vol. 25, p. 67-81. Bando, Y., 1979: Upper Permian and Lower Triassic ammonoids from Abadeh, central Iran. Memoir of the Faculty of Education, Kagawa University, Series Il, vol. 29, p. 103-138. Ehiro, M., 1996: Latest Permian ammonoid Paratirolites from the Ofunato district, Southern Kitakami Massif, Northeast Japan. Transactions and Proceedings of the Palaeon- tological Society of Japan, New Series, no. 184, p. 592- 596. Ehiro, M., 1997: Ammonoid palaeobiogeography of the South Kitakami Palaeoland and palaeogeography of eastern Asia during Permian to Triassic time. Proceedings of the 30th International Geological Congress, vol. 12, p. 18-28. Ehiro, M. and Bando, Y., 1985: Late Permian ammonoids from the Southern Kitakami Massif, Northeast Japan. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 137, p. 25-49. The ventral suture is not preserved. This specimen is assigned to Dzhulfoceras, judging from It is, however, impossi- ble to assign the specimen to a species with confidence be- Masayuki Ehiro Ehiro, M., Shimoyama, S. and Murata, M., 1986: Some Permian Cyclolobaceae from the Southern Kitakami Massif, Northeast Japan. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 142, p. 400-408. Gemmellaro, G. G., 1887: La fauna dei calcari con Fusulina della valle dei Fiume Sosio nella provincia di Palermo. Giornale di Scienze Naturali et Economiche, vol. 19, p. 1-106. Murata, M. and Bando, Y., 1975: Discovery of Late Permian Araxoceras from the Toyoma Formation in the Kitakami Massif, Northeast Japan. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 97, p. 22-31. Ruzhencev, V. E., 1962: Classification of the family Araxoceratidae. Paleontological Journal, no. 4, p. 88- 103. (in Russian) Ruzhencev, V. E., 1963: New data about the family Araxoceratidae. Paleontological Journal, no. 3, p. 56-64. (in Russian) Zakharov, Yu. D., 1986: Type and hypotype of the Permian- Triassic boundary. Memorie della Societa Geologica Italiana, vol. 34, p. 277-289. Zakharov, Yu. D. and Pavlov, A. M., 1986: The first find of araxoceratid ammonoids in the Permian of east USSR. In, Zakharov, Yu. D. and Onoprienko, Yu. I. eds., Permian-Triassic Events during Evolution of the North East Asia Biota, p.74-85, Academiya Nauk SSSR, Vladivostok. (in Russian) Paleontological Research, vol. 5, no. 2, pp. 115-120, June 29, 2001 © by the Palaeontological Society of Japan Middle Carboniferous orthoconic cephalopods from the Omi Limestone Group, Central Japan SHUJI NIKO Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, 739-8521, Japan (e-mail: niko@hiroshima-u.ac.jp) Received 13 November 2000; Revised manuscript accepted 9 April 2001 Abstract. A Middle Carboniferous (probable late Bashkirian) fauna of orthoconic cephalopods was collected from bioclastic rudstone/grainstone in the Omi Limestone Group, Central Japan. fauna belongs to the Taishaku-Akiyoshi-South China Faunal Province. This Recognized herein are the orthocerid nautiloid Bogoslovskya omiensis sp. nov., the bactritids Bactrites nagatoensis Niko, Nishida and Kyuma, 1991 and Bactrites sp., and an indeterminate body chamber. This is the first reliable documentation of orthoconic cephalopods from the Omi Limestone Group. Key words: Bactritida, Middle Carboniferous, Omi Limestone Group, Orthocerida Introduction Since the beginning of the Twentieth Century, some Carboniferous cephalopods have been occasionally re- ported by non-specialists of this group from the Omi Limestone Group, an accreted reefal buildup in Niigata Prefecture, Central Japan. The taxa cited include Gastrioceras sp. by Yabe (1904), Eoasianites cf. orientale (Yin) by Kato and Nakamura (1962), Eoasianites sp., Gastrioceras aff. reticulatus Yin, Paralegoceras sp. and Reticuloceras? sp. by Igo and Koike (1963, 1964), Pseudorthoceras sp. by Koizumi (1975), and Pseudoparalegoceras? sp. and Stroboceras sp. by Oyagi (2000). Unfortunately, these taxa were presented without detailed descriptions and/or illustrations, so an evaluation of their significance can not be made at this time. As the first attempt to give a reliable documentation of the Omi cephalo- pod fauna, the present report sheds light on the orthoconic nautiloids and bactritoids for taxonomic, biostratigraphic and paleobiogeographic purposes. The collecting site that yielded these cephalopods is situ- ated at the southern corner of Higashiyama Quarry, Latitude 36°59°27°°N and Longitude 137°47’8”E, where light gray, massive bioclastic rudstone/grainstone limestone is ex- posed. This cephalopod-bearing limestone is Middle Carboniferous (probable late Bashkirian) in age and may be part of the reef front facies (Niko and Hasegawa, 2000). The geologic setting of the Omi Limestone Group has been de- scribed in Hasegawa et al. (1969, 1982), Hasegawa and Goto (1990), and Nakazawa (1997), thus it will not be re- peated herein. During field work in 1997 to 1999, nearly thirty specimens identified as Bogoslovskya omiensis sp. nov., Bactrites nagatoensis Niko, Nishida and Kyuma, Bactrites sp., along with an indeterminate body chamber were collected in cooperation with Mr. Toshiaki Kamiya. This association of genera is characteristic of the Taishaku- Akiyoshi-South China Province (Niko, 2000). All specimens studied are reposited in the University Museum of the University of Tokyo (UMUT). Systematic paleontology Subclass Nautiloidea Agassiz, 1847 Order Orthocerida Kuhn, 1940 Superfamily Orthoceratoidea M’Coy, 1844 Family Orthoceratidae M’Coy, 1844 Subfamily Michelinoceratinae Flower, 1945 Genus Bogoslovskya Zhuravleva, 1978 Type species. — Bogoslovskya perspicua Zhuravleva, 1978. Bogoslovskya omiensis sp. nov. Figure 1.1-1.3, 1.5-1.9 Diagnosis.—Species of Bogoslovskya with 6°-7° angle of shell expansion, approximately 0.9 in form ratio of shell, transverse surface lirae; form ratio of camera 1.8-3.1; siphuncle strongly eccentric, its position ratio 0.13. Description.—Orthocones with 6°-7° angle of shell expan- sion and laterally compressed cross section yielding lateral/dorsoventral diameter ratio (form ratio of shell) of ap- proximately 0.9; largest specimen (paratype, UMUT PM 27892) of phragmocone reaches 16.5 mm in dorsoventral di- 116 Shuji Niko Figure 1. 1-3, 5-9. Bogoslovskya omiensis sp. nov. 1-3. Holotype, UMUT PM 27890; 1, dorsoventral thin section, x5; 2, details of apical siphuncle, x14; 3, details of surface ornamentation of apical shell, x10. 5, 8. Paratype, UMUT PM 27891; 5, side view of anti- siphuncular side, x2; 8, details of adoral siphuncle, thin longitudinal (but not dorsoventral) section, x 14. 6, 7, 9. Paratype, UMUT PM 27892; 6, side view, siphuncular side on right(?),x 2; 7, details of surface ornamentation of adoral shell, x10; 9, polished section near adoral end, siphuncular side down(?), slightly deformed, x 2. 4. Indeterminate body chamber, UMUT PM 27918, details of surface or- namentation, x5. ameter. Surface ornamentation of apical shell (represented lirae on adoral shell (ditto paratypes). Sutures not observed, by holotype, up to 7.9 mm in dorsoventral diameter) consists but obvious obliquity not observed in dorsoventral section. of subdued transverse lirae with somewhat unequal size and Septa moderately deep; cameral length relatively short for intervals, then it shifts to closely spaced, fine, transverse genus, 4.1 mm in length, with maximum dorsoventral diame- = Figure 2. 1-5. Bactrites nagatoensis Niko, Nishida and Kyuma, 1991. 1. UMUT PM 27897, dorsal view, x3. 2-4. UMUT PM 27895; 2, ventral view, x3; 3, dorsal view, x3; 4, apical view, venter down, x3. 5. UMUT PM 27896, dorsal view, x1.5. 6-12. Bactrites sp. 6-8, 10, 11. UMUT PM 27916; 6, apical view, venter down, x3; 7, dorsoventral thin section, venter on left, x14; 8, details of apical septal neck, venter on left, x14; 10, ventral view, x3; 11, dorsal view, x3. 9, 12. UMUT PM 27917; 9, longitudinal (near dorsoventral) polished section, venter on right, x2; 12, details of adoral septal neck, longitudinal (near dorsoventral) thin section, venter on right, x14. 13. Indeterminate body chamber, UMUT PM 27918, side view, x1.5. Carboniferous cephalopods from Omi Limestone Group 117 118 Shuji Niko ter/length ratio (form ratio of camera) 1.8 in apical shell; this ratio increases to 2.5-3.1 in adoral shell. Siphuncular posi- tion strongly eccentric and submarginal, minimum distance of central axis of siphuncle from shell surface per corre- sponding dorsoventral shell diameter (siphuncular position ratio) is 0.13 in holotype. Septal necks long for family; they are orthochoanitic and cylindrical in apical shell, then shifts gently tapering and funnel-shaped orthochoanitic forms in adoral shell; length of septal necks on anti-siphuncular (dor- sal?) side ranges from 1.03 mm to 1.28 mm; siphuncular di- ameters 0.42-0.70 mm at tips of septal neck, where septal foramen is 0.23-0.42 mm in diameter, giving a diameter of septal neck/corresponding dorsoventral shell diameter ratio of approximately 0.06. Annulus of weak auxiliary deposits recognized in septal foramina. Connecting ring not pre- served; no cameral deposits detected. Discussion.—Among the three previously known Upper Paleozoic species of this genus (see Niko et al., 1995, 1997, Niko and Ozawa, 1997), Bogoslovskya omiensis sp. nov. bears the greatest similarity to B. akiyoshiensis Niko, Nishida and Kyuma (1995, figs. 1.1-1.14) from the Middle Carboniferous (Moscovian) in the Akiyoshi Limestone, Southwest Japan. Although the gross shell shape and the surface ornamentation suggest the close phylogenetic rela- tionship of the both species, the main character of Bogoslovskya omiensis that separates it from B. akiyoshiensis is the more eccentric siphuncular position, with a siphuncular position ratio of 0.13 versus 0.19 for the corresponding shell diameter in B. akiyoshiensis. Etymology.—The specific name is derived from the Omi Limestone Group, in which this species occurs. Material examined.—The holotype, UMUT PM 27890, is an incomplete phragmocone 9.3 mm in length. The follow- ing two paratypes of the incomplete phragmocones are as- signed: UMUT PM 27891, 27.0 mm in length, and UMUT PM 27892, 12.8 mm in length. They represent more adoral shells than the holotype. In addition, two fragmentary speci- mens, UMUT PM 27893, 27895 are referred to this species with reservation. Subclass Bactritoidea Shimanskiy, 1951 Order Bactritida Shimanskiy, 1951 Family Bactritidae Hyatt, 1884 Genus Bactrites Sandberger, 1843 Type species.—Bactrites subconicus Sandberger, 1843. Bactrites nagatoensis Niko, Nishida and Kyuma, 1991 Figure 2.1-2.5 Bactrites nagatoensis Niko, Nishida and Kyuma, 1991, p. 715, figs. 2.1-2.10, 3.1-3.5. Bactrites cf. nagatoensis Niko, Nishida and Kyuma. Niko et al., 1997, p. 106, figs. 3.9, 4.8. Discussion. — Twenty-one bactritid specimens of the orthoconic phragmocones with an angle of adoral shell ex- pansion of approximately 5°-6° were collected from Higashiyama Quarry. The shell diameters range from 2.3 mm (UMUT PM 27907) to 25.1 mm (UMUT PM 27915). They have the shell morphology typical of the holotype, which is from the Moscovian (Middle Carboniferous) of the Akiyoshi Limestone, with rapid shell expansion for Bactrites and a single dorsal carina throughout the known phragmocone. A form possibly conspecific with this species also occurs in the Moscovian limestone of the Dala (Huanglong) Formation, Guizhou Province, South China (Niko et al., 1997). Comparisons of Bactrites nagatoensis to three Laurentian species (B. finisensis Mapes, 1979, pl. 23, figs. 4-6, B. mexicanus Miller, 1944, pl. 20, figs. 8, 9, pl. 21, figs. 4-6, and B. peytonensis Mapes, 1979, pl. 8, figs. 4-14, pl. 9, figs. 2, 3, 6-8, 12, 13, 15, 17-19, pl. 14, figs. 7, 8, 10) having a dorsal carina are referable in Niko et al. (1991, p. 715). Material examined.—UMUT PM 27895-27915. Bactrites sp. Figure 2.6-2.12 Description. —Orthocones with gradual shell expansion in- dicating near 2° in angle; cross section of shell circular; larg- est specimen (UMUT PM 27917) attains approximately 19 mm (slightly deformed) in diameter at adoral phragmocone. Surface ornamentation and carina absent, wrinkled layer not observed. Except for ventral lobe, sutures are nearly straight and slightly oblique at 6°-15° to rectangular direction of shell axis, toward aperture on dorsum. Septal curvature moderate; cameral length moderate with approximately 1.6 in diameter/length ratio. Siphuncular position ventral mar- gin; ventral septa attached to shell wall; septal necks orthochoanitic, relatively long for genus; dorsal septal necks 0.82-1.26 mm in length; diameter of septal foramen/corre- sponding shell diameter is approximately 0.07; connecting ring not preserved. No cameral and endosiphuncular de- posits detected. Discussion.—This species is known from the two frag- mentary phragmocones, but is easily separable from associ- ated Bactrites nagatoensis by the slenderer shell and the lacking a dorsal carina. The features approach those of Bactrites carbonarius Smith (1903, pl. 6, figs. 9-11), B. fayettevillensis Mapes (1979, pl. 9, figs. 9-11, pl. 10, figs. 6-8, pl. 13, figs. 1, 7, 8, 11, 12, 14-16, pl. 14, fig. 9, pl. 15, figs. 1, 2, 6, 7, 12-14), B. longocameratus Shimanskiy (1949, fig. 1), B. milleri Mapes (1979, pl. 10, fig. 10, pl. 12, figs. 4, 8-12), B. quadrilineatus Girty (1909, pl. 6, figs. 1, 1a, 1b, 2-4, 4a), B. smithianus Girty (1909, pl. 6, fig. 5, 67), and B. sp. (Niko et al., 1991, figs. 3.6-3.9). Due to the poor pres- ervation of the Omi specimens and the relatively simple mor- phology of this group for Bactrites, specific comparisons cannot be made at this time. Material examined.—UMUT PM 27916, 27917. Subclass, Order, Superfamily, Family, Genus, and Species uncertain body chamber Figures 1.4, 2.13 Discussion. — A fragmentary body chamber of an orthoconic shell, 67.5 mm in length and 39 mm+ (deformed) Carboniferous cephalopods from Omi Limestone Group in diameter, is available for this study. Although its surface ornamentation consisting of weak annulations and lirae shows an affinity to the mature modification of some bactritids including Bactrites peytonensis Mapes and Bactrites? sp. morphotype 13 (Mapes, 1979, pl. 2, figs. 14- 16), lack of knowledge of the siphuncular structure and posi- tion precludes a positive identification even to be subclass level. Similar ornamentation is also known to occur in the Carboniferous orthocerids, such as Brachycycloceras (Miller et al., 1933), Cryptocycloceras (Shimansky, 1968), Cyclo- ceras (M'Coy, 1844), and Reticycloceras (Gordon, 1960). Material examined.—UMUT PM 27918. Acknowledgments The present cephalopod specimens were collected with the field assistance of Toshiaki Kamiya. | also wish to thank the staff of the materials section, Omi Mine (Denki Kagaku Kogyo Co., Ltd.), who allowed access to the fossil locality in Higashiyama Quarry through the good offices of Yoshiyuki Hasegawa. References Agassiz, L., 1846-1847: Nomenclatoris Zoologici Index Universalis, 393 p. Jent and Gassmann, Soloduri. Flower, R. H., 1945: Classification of Devonian nautiloids. American Midland Naturalist, vol. 33, p. 675-724, pls. 1- =} Girty, G. H., 1909: The fauna of the Caney Shale of Oklahoma. United States Geological Survey Bulletin 377 , p. 1-106. Gordon, M., 1960: Some American Midcontinent Carboniferous cephalopods. Journal of Paleontology, vol. 34, p. 133-151, pls. 27, 28. Hasegawa, Y. and Goto, M., 1990: Paleozoic and Mesozoic of Omi region. In, Guidebook of Field Excursion at 97th Meeting of the Geological Society of Japan, p. 227-260. The Geological Society of Japan. (in Japanese) Hasegawa, Y., Hayakawa, T., Ozawa, K., Takano, O. and Ando, T., 1969: Paleozoic sediments of the Omi district, Niigata Prefecture. /n, Guidebook of Field Excursion at 76th Meeting of the Geological Society of Japan, p. 1-25. The Geological Society of Japan. (in Japanese) Hasegawa, Y., Tazawa, J. and Niikawa, I, 1982: Omi Limestone and adjoining older rocks. In, Guidebook of Field Excursion at 89th Meeting of the Geological Society of Japan, p. 1-23. The Geological Society of Japan. (in Japanese) Hyatt, A. 1883-1884: Genera of fossil cephalopods. Proceedings of the Boston Society of Natural History, vol. 22, p. 253-338. Igo, H. and Koike, T., 1963: Discovery of conodonts from the Omi Limestone. The Journal of the Geological Society of Japan, vol. 69, p. 519. (in Japanese) Igo, H. and Koike, T., 1964: Carboniferous conodonts from the Omi Limestone, Niigata Prefecture, Central Japan. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 53, p. 179-193, pls. 27, 28. Kato, M. and Nakamura, K., 1962: A goniatite from the Omi Limestone. Chikyukagaku (Earth Science), no. 63, p. 33, 34, pl. 6. (in Japanese with English abstract) Koizumi, H., 1975: Paleozoic Cephalopods of Japan, 149 p. Teiseki Bunko, Tokyo. (in Japanese) Kuhn, O., 1940: Paläozoologie in Tabellen, 50 p. Fischer, Jena. Mapes, R. H., 1979: Carboniferous and Permian Bactritoidea (Cephalopoda) in North America. The University of Kansas Paleontological Contributions, Article 64, p. 1-75, pls. 1-41. M'Coy, F., 1844: A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland, 274 p. Privately published. (reissued by Williams and Norgate, London, 1862) Miller, A.K., 1944: Geology and paleontology of the Permian area northwest of Las Delicias, southwestern Coahuila, Mexico. Part 4, Permian cephalopods. Geological Society of America, Special Papers Number 52, p. 71- 127, pls. 20-45. Miller, A.K., Dunber, C.O. and Condera, G.E., 1933: The nautiloid cephalopods of the Pennsylvanian System in the Mid-Continent region. Nebraska Geological Survey, Bulletin 9, Second Series, p. 1-240, pls. 1-24. Nakazawa, T., 1997: Sedimentary environments and reef- builders in the Carboniferous of the Limestone Group. The Journal of the Geological Society of Japan, vol. 103, p. 849-868. (in Japanese with English abstract) Niko, S., 2000: New cephalopod material from the Bashkirian (Middle Carboniferous) of the Ichinotani Formation, Central Japan. Paleontological Research, vol. 4, p. 255-260. Niko, S. and Hasegawa, Y., 2000: Two species of Middle Carboniferous tabulate corals from the Omi Limestone Group, Niigata Prefecture. Bulletin of the National Science Museum, Ser. C, vol. 26, p. 129-137. Niko, S., Nishida, T. and Kyuma, Y., 1991: Middle Carboniferous Bactritoidea (Mollusca: Cephalopoda) from the Akiyoshi Limestone Group, Yamaguchi Prefecture. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 161, p. 714-719. Niko, S., Nishida, T. and Kyuma, Y., 1995: A new Carboniferous cephalopod Bogoslovskya akiyoshiensis from Southwest Japan. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 179, p. 193-195. Niko, S., Nishida, T. and Kyuma, Y., 1997: Moscovian (Carboniferous) orthoconic cephalopods from Guizhou and Guangxi, South China. Paleontological Research, vol. 1, p. 100-109. Niko, S. and Ozawa, T., 1997: Late Gzhelian (Carboniferous) to early Asselian (Permian) non-ammonoid cephalopods from the Taishaku Limestone Group, Southwest Japan. Paleontological Research, vol. 1, p. 47-54. Oyagi, K., 2000: Selection of 800 Fossils in Japan with Locality Divisions, 298 p. Tukiji Shokan, Tokyo. (in Japanese) Sandberger, G., 1843: Schilderung der paläontologischen Verhältnisse der älteren Formationen Nassaus. Versammlung Deutsher Naturforscher und Aerzte Mainz, Bericht 20, p. 154-160. Shimanskiy, V. N., 1949: Verkhnekamennougolnye nautiloidei Yuzhnogo Urala (Upper Carboniferous nautiloids of the Southern Urals). Doklady Akademii Nauk SSSR, vol. 66, p. 929-932. (in Russian) 119 120 Shuji Niko Shimanskiy, V. N., 1951: K voprosu ob evolyutsii Smith, J. P., 1903: The Carboniferous ammonoids of America. verkhnepaleozoishikh pryamkh golovonogikh (On the Monographs of the United States Geological Survey, vol. evolution of the Upper Paleozoic straight cephalopods). 42, p. 1-211. Doklady Akademii Nauk SSSR, vol. 79, p. 867-870, pl. 1. Yabe, H., 1904: Palaeozoic ammonites of Japan. The Journal (in Russian) of the Geological Society of Tokyo, vol. 11, p. 26, 27. (in Shimanskiy, V. N., 1968: Kamennougolnye Orthoceratida, Japanese) Oncoceratida, Actinoceratida i Bactritida (Carboniferous Zhuravleva, F. A., 1978: Devonskiye ortoserody, nadotryad Orthoceratida, Oncoceratida, Actinoceratida and Orthoceratoidea (Devonian orthocerids, superorder Bactritida). Akademiia Nauk SSSR, Trudy Orthoceratoidea). Akademiia Nauk SSSR, Trudy Paleontologicheskogo Instituta, vol. 117, p. 1-151, pls. Paleontologicheskogo Instituta, vol. 168, p. 1-223. (in 1-20. (in Russian) Russian) Paleontological Research, vol. 5, no. 2, pp. 121-129, June 29, 2001 © by the Palaeontological Society of Japan Mode of occurrence and composition of bivalves of the Middle Jurassic Mitarai Formation, Tetori Group, Japan TOSHIFUMI KOMATSU’, RYO SAITO? and FRANZ T. FÜRSICH?’ "Department of Earth and Planetary Science, Graduate School of Science, Kyoto University, Kyoto, 606— 8502, Japan (e-mail: komatsu @bs.kueps.kyoto-u.ac.jp) *Institut für Paläontologie der Universität Würzburg, Pleicherwall 1, D-97070 Würzburg, Germany (franz.fuersich@mail.uni-wuerzburg.de) Received 1 August 2000; Revised manuscript accepted 12 April 2001 Abstract. The Middle Jurassic Mitarai Formation distributed in Shokawa Village, Gifu Prefecture, central Japan, is interpreted as deposits of wave-dominated shelf environments. The muddy shelf deposits yield abundant molluscs showing various modes of occurrence that can be divided into three fossil assemblages: (1) the autochthonous Modiolus maedae-Tetorimya carinata assemblage with commonly in-situ preserved semi-infauna and deep burrowers; (2) the Entolium inequivalve assemblage characterized by mixed autochthonous infauna and parautochthonous free-living ele- ments; and (3) the allochthonous /noceramus maedae assemblage. The Entolium inequivalve as- semblage contains the chemosymbiotic bivalve Solemya and is associated with a low-diversity ichnofauna suggestive of low oxygen conditions. Key words: bivalves, fossil assemblage, ichnofauna, Jurassic, low oxygen condition, Mitarai Formation, taphonomy Introduction The Middle Jurassic Mitarai Formation, Tetori Group, is exposed in the vicinity of Shokawa Village, Gifu Prefecture, central Japan (Figure 1) and is composed of shallow marine deposits. The formation yields abundant benthic macro- fossils and has been well studied by geologists and palaeontologists (Maeda, 1952, 1961; Hayami, 1959a, b, 1960; Masuda et a/., 1991; Matsukawa and Nakada, 1999). Maeda (1952) and Matsukawa and Nakada (1999) provided the geologic map and described the stratigraphy of the for- mation in this area. Masuda et al. (1991) broadly discussed the depositional environments and tectonic nature of the Tetori basin situated along the East Asian continental mar- gin. The benthic fauna of the Mitarai Formation mainly con- sists of bivalves. It has been described from a taxonomic point of view by Hayami (1959a, b, 1960). However, no palaeoecological or taphonomic studies of this fauna exist, although the bivalves show variable modes of occurrence ranging from an apparently allochthonous type to an autochthonous type preserving the life orientation. Moreover, the relationship between depositional environ- ments and benthic assemblages, faunal compositions and ichnofauna are hardly known in the Jurassic of East Asia. In this paper, the depositional environments of the Mitarai Formation are reconstructed based on facies analysis. The bivalves are grouped into three fossil assemblages, and their habitats and the nature of the assemblages are dis- cussed. Particular emphasis has been placed on the com- position of the benthic fauna and the modes of fossil occurrences which are described in detail. Geological framework The Jurassic to Cretaceous Tetori Group is composed of nonmarine and shallow-marine deposits, and is widely dis- tributed in the north-central part of Japan (Figure 1). The group is divided into three subgroups, the Kuzuryu, Itoshiro and Akaiwa in ascending order (Maeda, 1952, 1961). The Kuzuryu Subgroup is subdivided into the Ushimaru and Mitarai formations (Matsukawa and Nakada, 1999). These formations typically crop out in the study area of the Shokawa Village, Gifu Prefecture. The lower part of the Ushimaru Formation unconformably overlies basal granitic rocks, and consists of fluvial, coarse clastic deposits and estuarine (in a broad sense) deposits containing abundant brackish-water molluscs such as Crassostrea sp., Myrene tetoriensis and Tetoria yokoyamai. 122 Toshifumi Komatsu et al. Shokawa 2, Village: Nonomata N 1112 | 13° DA 7 806 1309 Y Be 802 1308 1109 1304 Mitarai 1307 = u > 1305 250m (+2 1306 — Figure 1. Map of Shokawa Village, showing the localities of molluscan fossil samples from the Mitarai Formation. The upper Ushimaru Formation is composed of alternating beds of sandstone and mudstone commonly yielding brack- ish-water and marine molluscs, and is interpreted as estuarine and shallow marine deposits, which are conforma- bly overlain by the marine Mitarai Formation (Kumon and Kano, 1991; Matsukawa and Nakada, 1999). The Mitarai Formation is about 45 m thick and consists of a basal con- glomerate, sandstone and dark grey mudstone with abun- dant marine fossils such as ammonites, crinoids, gastropods and bivalves (Figure 2). The ammonite, Lilloetia sp., sug- gests a Callovian (Middle Jurassic) age (Sato and Kanie, 1963). This formation is overlain by shallow marine sand- stone of the Otaniyama Formation, Itoshiro Subgroup (Maeda, 1952; Kumon and Kano, 1991; Matsukawa and Nakada, 1999). Lithostratigraphy and depositional environments of the Mitarai Formation Lithostratigraphy The succession ranging from the uppermost Ushimaru Formation to the Mitarai Formation yields abundant marine molluscan fossils and is characterized by a transgressive se- quence followed by regression (Matsukawa and Nakada, 1999). The uppermost Ushimaru Formation is composed of conglomerate and sandstone (Figure 2). The Mitarai Formation is mainly dominated by mudstone. The upper- most Ushimaru Formation of this paper is almost equivalent to the M1 member of the Mitarai Formation (Hayami, 1959). The uppermost part of the Ushimaru Formation is com- posed of about 16 m of thick fine-grained sandstone with an about 40-cm-thick basal conglomerate bed. This conglom- erate bed contains well rounded pebbles and cobbles, and exhibits a sharp erosional contact with the underlying sand- stone. The sandstone is characterized by hummocky cross-stratification and bioturbation. Maeda (1952) and Hayami (1960) reported the marine bivalve /noceramus maedae from this sandstone. The HCS sandstone is capped locally by a thin conglomerate, which marks the base of the Mitarai Formation. The lower part of the Mitarai Formation consists of mudstone interbedded with trough and hummocky cross-stratified and parallel-laminated sandstone beds. The alternating beds of mudstone and sandstone gradually change. upward into bioturbated massive mudstone. The upper part of this mudstone is intercalated with thin, parallel-laminated sandstone beds (1-4 cm thick) and a thick, very fine-grained sandstone bed (Loc.1112). It is finally overlain by fine- to medium-grained sandstone of the Otaniyama Formation. The sandstone of the basal Otaniyama Formation yields rare disarticulated valves and fragments of Inoceramus maedae. The upper Mitarai Formation and the basal Otaniyama Formation form a coars- ening-upward succession. Depositional environments The HCS sandstone of the upper Ushimaru Formation containing typical shallow marine bivalves is interpreted as wave-dominated nearshore sediments deposited above fair- weather wave base. HCS is a diagnostic sedimentary structure formed under waning storm and wave or com- bined-flow conditions (e.g. Duke et al., 1991; Cheel and Leckie, 1993). HCS sandstones without associating muddy sediments imply deposition shallower than fair-weather wave base (Walker and Plint, 1992). The conglomerate bed at the base of the HCS sandstone (Figure 3.1) is in erosional contact with estuarine deposits of the Ushimaru Formation. This erosional surface, probably a result of strong shoreface erosion during transgression, marks an in- crease in water depth. Thus, the conglomerate can be in- terpreted as a transgressive lag deposit. The Mitarai Formation is composed mainly of mudstone yielding marine fossils, which is interpreted to represent inner and outer shelf deposits below fair-weather wave base. In the lower part, the alternating beds of HCS sand- stone and bioturbated mudstone probably indicate deposi- tion during repetition of storm and fair-weather conditions in inner shelf environments. Parallel-laminated sandstone beds possibly represent tempestites generated by storm- induced flow (Walker and Plint, 1992). Bioturbated thick mudstone without sandstone intercalation overlying these al- ternating units may reflect an increase in water depth during transgression, and is interpreted as outer shelf deposits. The thick sandstone beds of the upper Mitarai Formation (Locs. 1308, 1112) and the basal sandstone of the Otaniyama Formation (Loc. 1309) contain /noceramus maedae, and probably represent nearshore environments. The coarsening- and shallowing-upward successions of the upper Mitarai and basal Otaniyama formations are inter- preted to indicate deltaic systems (Kumon and Kano, 1991; Matsukawa and Ito, 1995), suggesting a regressional phase, that is, relative sea-level fall. Jurassic bivalve taphonomy 123 Legend Individual number E3 Mudstone Otaniyama F. Estuary ‘a udstone Sandstone Conglomerate > 3 u — Current ripple + Nodule = Wave ripple U) Bioturbation <« 1309- SE «1112: DRE Love Eile 41009: 4806 - lien: ; 41308: eure 4302 | - [es 2 G = Shelf o . . = «1008: So! | = S = 41111- 41007: «1307 ee ae 41306 : 41110- : QE a UE .. 41305 ee > NS - Shelf: 41109. 41006-. ‘ 41304 1108- [wy] 41005: 1107 + 41004: ) =} == ® © D ©. w 2D D A & Bo Y FT Shoreface SS game seaue? — D d 6s ® 7 25 Sees 8 FSR eeS V =o Sake = Fand Gees same, NE TS RER) pee ye SR See ti 6 CROSS ER RS CR SOUS = Shoreface 2S Sis) G Se aaah = 1106 oS) = Ss à = ae = £ L £ wu Q oO I} = = > + 7ransgressive surface a © J au a Lai wo 5 Ar a Q E © = an at = ] e1~5 @:6~10 @:11~15 @:16~ Hummocky cross-stratification epibyssate) deep burrower ) (suspension —feeder) (suspension —feeder, shallow burrower) (suspension-feeder) -- (suspension —feeder, : shallow burrower) (suspension —feeder, (deposit—feeder, Semi-infauna Epifauna Infauna .. Epifauna Infauna Infauna Figure 2. Columnar sections of Mitarai and Otaniyama Formations, showing the horizons of the samples examined and stratigraphic occurrences of bivalve species. Mode of occurrence and composition of bivalves Methods Bivalve fossils are found very sporadically in muddy de- posits of the Mitarai Formation. These shells do not form shell beds, except for minor shell lenses in several horizons. Bivalves were counted on outcrop surfaces, and were col- lected bed by bed. Due to the limited material and marked differences in fossil preservation between samples, we did not carry out quantitative analysis of the fossil assemblages. Based on the faunal composition and modes of fossil occur- rences the samples from various localities were grouped in three assemblages, the Modiolus maedae-Tetorimya carinata, the Entolium inequivalve, and the /noceramus maedae assemblage. The /noceramus maedae assem- blage, which exceptionally forms minor shell lenses, was distinguished from the others by its mode of occurrence. Life habits of the bivalves were reconstructed based on analogy with closely related living taxa, and also by referring to previous studies (Scott, 1974; Wright 1974; Fürsich, 1977, 124 Toshifumi Komatsu et al. Figure 3. Photos showing sedimentary structures, trace fossils and modes of fossil occurrences. 1. Conglomerate and overlying hummocky cross-stratified sandstone (HCS) (Ushimaru Formation, loc. 1106). The conglomerate is interpreted to represent a transgressive lag deposit (T.L.). The hammer is 28 cm long. 2. Exposure of alternating beds of sandstone and mudstone (lower Mitarai Formation, loc. 2001). 3. Bedding plane of intensely bioturbated mudstone with large two-dimensional burrows (lower Mitarai Formation, loc. 1108). 4. Vertical section of mudstone containing articulated Tetorimya carinata Hayami (arrowed) (lower Mitarai Formation, loc. 1108). 5. Vertical section of mudstone containing articulated Modiolus maedae Hayami (arrowed) (lower Mitarai Formation, loc. 1108). 6. Plan view of mudstone containing articulated Modiolus maedae Hayami (arrowed) (lower Mitarai Formation, loc. 1005). Posterior parts of M. maedae are found. Jurassic bivalve taphonomy 125 1984; Aberhan, 1994). Modiolus maedae-Tetorimya carinata assemblage This assemblage contains the following bivalves: the deep-infaunal Tetorimya carinata, Thracia shokawensis, Pleuromya hidensis, and Goniomya sp.; the endobyssate Modiolus maedae and Pinna sp. aff. P. sandsfootensis; the shallow infaunal Palaeonucula makitoensis, ”Palaeoneilo” sp., and Protocardia sp.; and the epibyssate or free-living Entolium inequivalve, Limatula iwayae, Oxytoma tetoriense, Chlamys mitaraiensis and Camptonectes sp. (Figure 4). M. maedae and T. carinata are characteristic species of this assemblage. The M. maedae-T. carinata assemblage consists of abundant deep-burrowers, two semi-infaunal taxa, and several shallow infaunal and epifaunal elements. The deep-burrowing, semi-infaunal and shallow infaunal bi- Figure 4. Bivalves from the Mitarai Formation. Mitarai Formation, loc. 1108. 2. Tetorimya carinata Hayami. Hayami. All specimens x1.0. Left valve, lower Mitarai Formation, loc. 2001. Left external cast, lower Mitarai Formation, loc. 1108. 4. Protocardia sp. with gaping articulated valves (butterfly position), lower Mitarai Formation, loc. 1108. 5. Entolium inequivalve Hayami. Left external cast, lower Mitarai Formation, loc. 1108. 7. Limatula iwayae Hayami. Left external cast, lower 3. Pleuromya hidensis 1. Modiolus maedae Hayami. Right valve, upper Mitarai Formation, loc. 801. 6. Goniomya sp. Right external cast, upper Mitarai Formation, loc. 1008. 8. Oxytoma tetoriense Hayami. Left external cast, lower Mitarai Formation, loc. 1108. 9. Thracia shokawensis Hayami. Left external cast, lower Mitarai Formation, loc. 1108. 10. Solemya suprajurensis Hayami with gaping articulated valves (butterfly position), upper Mitarai Formation, loc. 801. 11. Fragment of Inoceramus maedae Hayami (external mould) and ammonite from shell lens, lower Mitarai Formation, loc. 1005. 126 Toshifumi Komatsu et al. valves occur usually dispersed and are almost invariably preserved as articulated valves. M. maedae, T. carinata and P. hidensis are arranged with their sagittal plane per- pendicular to the bedding plane with their posterodorsal or posterior margin pointing upward (Figures 3.4-6, 5) which is interpreted as keeping their life orientation. Especially all 50 individuals of M. maedae collected during the study are articulated and preserved in situ. Shells of Pinna sp. also preserve their life position with the umbones directed down- ward. Some of the shallow infaunal bivalves such as Palaeonucula makitoensis and Protocardia sp. are found ar- ticulated in butterfly position. Epifauna is usually disarticulated, only rarely articulated. Occasionally, disarticulated epifaunal bivalves, fine shell debris and crinoid fragments form small shell lenticles (about 1cm thick and 10 -30 cm wide) with plant fragments. This assemblage oc- curs in bioturbated mudstone with intercalated thin sand- stone beds in the lower part of the Mitarai Formation, which represents inner shelf deposits within the transgressive phase of the formation. Entolium inequivalve assemblage The assemblage consists of the shallow-burrowing Palaeonucula makitoensis and “Palaeoneilo” sp., the epifaunal Entolium inequivalve and Limatula iwayae, and the deep-infaunal Solemya suprajurensis. The E. inequivalve assemblage is characterized by a mix- ture of epifaunal and shallow infaunal bivalves. E. inequivalve and L. iwayae are common and occasionally preserved parallel to the bedding plane. Although the epifauna is usually disarticulated, the right and left valve of the same individual occasionally overlap. Shallow infaunal burrowers consist of the deposit-feeding bivalves P. makitoensis and “Palaeoneilo” sp., and are usually pre- served in articulated condition. The very rare S. suprajurensis is also preserved with their valves articulated. This assemblage is found in bioturbated mudstone of the upper Mitarai Formation, except in its lower part (Locs. 801, 806, 1008). Inoceramus maedae assemblage The assemblage is characterized by the co-occurrence of the epifaunal bivalves Inoceramus maedae, Entolium inequivalve, Limatula iwayae, and Oxytoma tetoriense, and the shallow-burrowing Palaeonucula makitoensis and Protocardia sp. Epifauna dominates, in particular disarticulated and frag- mented valves of |. maedae. E. inequivalve, L. iwayae, O. tetoriense, P. makitoensis and Protocardia sp. rarely occur in disarticulated and fragmented condition. These bivalves usually form small shell lenses (20-100 cm wide) associated with ammonites, crinoids, and abundant plant fragments. Some of the ammonites are fragmented and show selective dissolution of inner whorls. The shell lenses commonly over- lie HCS and parallel-laminated sandstone beds. This as- semblage is found throughout the Mitarai Formation (Locs. 1004, 1009). Trace fossils The lower part of Mitarai Formation (inner shelf deposits) n=32 Modiolus maedae 10 n=10 Tetorimya carinata 5 Figure 5. Modes of fossil occurrences of Modiolus maedae Hayami and Tetorimya carinata Hayami. Almost all specimens are arranged with their sagittal plane perpendicular to the bedding plane with the posterodorsal or posterior margin pointing upward. contains several kinds of trace fossils; Spirophycus isp., Phycosiphon isp., Skolithos isp., Palaeophycus isp., Teredolites isp., and a large two-dimensional burrow (Beaconites?; Figures 3.3, 6.1). Skolithos isp., Palaeo- phycus isp., the large two-dimensional burrows and intense obscure mottling are restricted to this horizon, whereas Spirophycus isp. and Phycosiphon isp. are very abundant throughout the Mitarai Formation. The upper part of the Mitarai Formation, which can be in- terpreted to represent an outer shelf environment, is charac- terized by low diversity of trace fossils consisting solely of Spirophycus isp. and Phycosiphon isp. (Figure 6.2). Beds full of Spirophycus (15-70 cm thick) are common in this part. Teredolites isp. is a boring in drift wood produced by wood-boring bivalves (Teredinidae). These wood pieces are commonly found within small shell lenses including Inoceramus maedae and ammonite fragments. Jurassic bivalve taphonomy 127 Figure 6. Vertical section of bioturbated mudstones of the lower Mitarai Formation: (1), loc. 1108, and the upper Mitarai Formation: (2), loc. 801. Scale bars are Icm. 1. Spirophycus isp., Skolithos isp. and obscure mottling are found. 2. Spirophy- cus isp. Note low diversity of trace fossils. Discussion Autochthonous and allochthonous occurrence of bi- valves The Modiolus maedae-Tetorimya carinata assemblage is composed mainly of autochthonous bivalves. Almost all deep infaunal and semi-infaunal bivalves are preserved with their sagittal plane perpendicular to the bedding, which is in- dicative of their life orientation (Figures 3.3-6, 5, 7). In par- ticular, the modes of occurrence of Modiolus and Pinna are very similar to that of present-day ones. Shallow infaunal bivalves, such as Palaeonucula and Protocardia, are articu- lated and do not retain their life position, indicating that these taxa were easily exhumed after death. The members of this assemblage probably occur more or less in situ, and are in- terpreted as the autochthonous fauna of inner shelf depos- its. By contrast, the Entolium inequivalve assemblage is domi- nated by the epifaunal recliners E. inequivalve and Limatula iwayae and occurs in outer shelf deposits. Most examples of the two taxa are preserved with their valves disarticulated; rarely, disarticulated valves of the same individual overlap each other. Therefore, most epifaunal species are inter- preted to represent parautochthonous occurrences. Articulated Palaeonucula makitoensis and Solemya suprajurensis probably indicate autochthonous occurrences. Epifaunal elements of the /noceramus maedae assem- blage are considered to be typically allochthonous. 1. maedae from muddy shelf deposits invariably is fragmented and disarticulated and occurs in shell lenses overlying storm sand sheets. /. maedae occurs in coastal sandstones of the basal Otaniyama Formation (Loc. 1309), as well as in the HCS sandstones of the Ushimaru Formation (Maeda,1952; Hayami, 1960). Probably /. maedae underwent transport from nearshore areas during storm events. Influence of low oxygen conditions on the infauna of the Entolium inequivalve assemblage The Entolium inequivalve assemblage, occurring in open shelf environments, is composed of an autochthonous infauna and a parautochthonous free-living epifauna. The infauna was probably influenced by low oxygen conditions. The assemblage is characterized by a low-diversity fauna and consists of autochthonous Palaeonucula makitoensis and Solemya suprajurensis in association with reworked in- dividuals of free-living Entolium inequivalve and byssate Limatula iwayae. These genera are typical of Jurassic mid- to outer-shelf and oxygen-controlled environments (Aberhan, 1994). Moreover, Recent representatives of Solemya live in muddy bays of stagnant water conditions and in deep-sea areas characterized by low oxygen levels, and are components of the chemosynthetic community (Reid and Bernard, 1980; Felbeck et al., 1981). Therefore, the low diversity of this assemblage probably is a result of lowered oxygen levels within the sediment. Furthermore, this assemblage is associated with the graz- ing traces (pascichnia) Spirophycus and Phycosiphon, whereas dwelling traces (domichnia) such as Skolithos and Palaeophycus are absent. These pascichnia exhibit a low- diversity, moderately high density and small size, suggestive of opportunistic producers (Bromley, 1996). Ekdale and Mason (1988) proposed that pascichnia-dominated trace fossil assemblages are formed under less oxygenated con- ditions than domichnia-dominated ones. Hence, the char- acter of the ichnofauna supports our interpretation of relatively low oxygen-conditions. Conclusions 1. Three bivalve assemblages are distinguished in the Jurassic Mitarai Formation, Tetori Group. The Modiolus maedae-Tetorimya carinata assemblage contains abundant semi-infaunal and deep-burrowing taxa in preserved life ori- entation and represents the undisturbed, autochthonous fauna of inner shelf environments. The Entolium inequivalve assemblage occurs in outer shelf deposits and is characterized by a mixture of autochthonous infaunal ele- 128 Toshifumi Komatsu et al. Palaeophycus isp. Skolithos isp. Ammonite Sp/rophycus isp. Inoceramus maedae Modiolus maedae Phycosiphon \sp. Limatula iwayae Inoceramus maedae Oxytoma tetoriense Entolium inequivalve | Phycosiphon isp. - Palaeonucula makitoensis Spirophycus isp. Pleuromya hidensis Tetorimya carinata Pinna sp. aff. P. sandsfootensis Figure 7. Ecological reconstruction of the bivalve fauna in shelf deposits of the Mitarai Formation. ments and parautochthonous byssate or free-living epifauna. The /noceramus maedae assemblage consists of fragments and disarticulated valves and represents typical allochthonous occurrences. In particular /noceramus maedae underwent transport from sandy nearshore areas. 2. The Entolium inequivalve assemblage contains the chemosymbiotic bivalve Solemya, and is associated with a low-diversity ichnofauna, which suggests lowered oxygen conditions. 3. Palaeoecological and taphonomic data allow a more re- fined reconstruction of palaeoenvironments and their changes through time than sedimentary features alone. Acknowledgments We would like to express our sincere thanks to Hiroshige Matsuoka of Kyoto University and Shizuo Shimojima of the Educational Department of Shokawa Village, for their coop- eration in collecting fossils, and to Fujio Masuda of Kyoto University for his help with sedimentological aspects. We are also grateful to the Educational Department of Shokawa Village for their kind assistance during field work. This work was partly supported by Grant-in-Aids from the Fukada Geological Institute. F.T.F. acknowledges, with thanks, a fel- lowship of the Japan Society for the Promotion of Science. Two anonymous reviewers provided critical comments and suggestions, to whom we express our gratitude. References Aberhan, M., 1994: Guild-structure and evolution of Mesozoic benthic shelf communities. Palaios, vol. 9, p. 516-545. Bromley, R. G., 1996: Trace Fossils. Biology, Taphonomy and Applications, 361 p. Chapman and Hall, London. Jurassic bivalve taphonomy Cheel, R. J. and Leckie. D. A., 1993: Hummocky cross- stratification. Sedimentology Review, vol. 1, p. 103-122. Duke, W., Arnott, R. W. C. and Cheel, R. J., 1991: Shelf sandstones and hummocky cross-stratification: insights on a storm debate. Geology, vol. 19, p. 625-628. Ekdale, A. A. and Mason, T. R., 1988: Characteristic trace- fossil associations in oxygen-poor sedimentary environ- ments. Geology, vol. 16, p. 720-723. Felbeck, H., Childress, J. J. and Somero, G. N., 1981: Cavin- Benson cycle and sulphide oxidation enzymes in animals from sulphide-rich habitats. Nature, vol. 293, p. 291- 293. Fursich, F. T., 1977: Corallian (Upper Jurassic) environments marine benthic associations from England and Normandy. Palaeontology, vol. 20, p. 337-385. Fursich, F. T., 1984: Palaeoecology of boreal invertebrate fau- nas from the Upper Jurassic of central eastern Green- land. Palaeogeography, Palaeoclimatology, Palaeo- ecology, vol. 48, p. 309-364. Hayami, |., 1959a: Late Jurassic hipodont, taxodont and dysodont pelecypods from Makito, Central Japan. Japanese Journal of Geology and Geography, vol. 31, p. 135-150. Hayami, |., 1959b: Late Jurassic isodont and myacid pelecypods from Makito, Central Japan. Japanese Journal of Geology and Geography, vol. 31, p. 151-167. Hayami, |., 1960: Jurassic inoceramids in Japan. Journal of the Faculty of Science, University of Tokyo, Sec. 2, vol. 12, p. 277-328. Kumon, F. and Kano, K., 1991: Tetori Group in the Shokawa district, Gifu Prefecture, central Japan. Report of Research Project, Grant-in-Aid for Scientific Research (C), No. 01540626, p. 2-37. (in Japanese) Maeda, S., 1952: A stratigraphical study on the Tetori Series in the upper Shiokawa district in Gifu Pref. The Journal of the Geological Society of Japan, vol. 58, p. 145-153. (in Japanese with English abstract Maeda, S., 1961: On the geological history of the Mesozoic Tetori Group in Japan. Journal of the College of Arts and Sciences, Chiba University, no. 3, p. 369-426. (in Japanese with English abstract) Masuda, F., Ito, M., Matsukawa, M., Yokokawa, M. and Makino, Y., 1991: Depositional environments. In, Matsukawa M. ed., Lower Cretaceous Nonmarine and Marine Deposits in Tetori and Sanchu, Honshu, IGCP- 245 Field Trip Guide of 1991, Fukuoka International Symposium, p. 11-17. Matsukawa, M. and Ito, M., 1995: Evaluation of nonmarine bi- valves as index fossils based on those from the Japanese Lower Cretaceous. The Journal of the Geological Society of Japan, vol. 101, p. 42-53. (in Japanese with English abstract) Matsukawa, M. and Nakada, K., 1999: Stratigraphy and sedi- mentary environment of the Tetori Group in its central dis- tribution based on nonmarine molluscan assemblages. The Journal of the Geological Society of Japan, vol. 105, p. 817-835. (in Japanese with English abstract) Reid, R. G. B. and Bernard, F. R., 1980: Gutless bivalves. Science, vol. 208, p. 609-610. Sato, T. and Kanie, Y., 1963: Lilloetia sp. (ammonite Callovienne) de Mitarasi au bassin de Tetori. Transaction and Proceedings of the Palaeontological Society of Japan, New Series, no, 49, p. 8. Scott, R. W., 1974: Bay and shoreface benthic communities in the Lower Cretaceous. Lethaia, vol. 7, p. 315-330. Walker, R. G. and Plint, A. G., 1992: Wave and storm- dominated shallow marine systems. In, Walker, R. G. and James, N. P. eds., Facies Models: Response to Sea Level Change. p. 219-238. Geological Association of Canada, Stittsville, Ontario. Wright, R. P., 1974: Jurassic bivalves from Wyoming and South Dakota: a study of feeding relations. Journal of Paleontology, vol. 48, p. 425-433. 129 Paleontological Research, vol. 5, no. 2, pp. 131-140, June 29, 2001 © by the Palaeontological Society of Japan Regular axopodial activity of Diplosphaera hexagonalis Haeckel (spheroidal spumellarian, Radiolaria) NORITOSHI SUZUKI" and KAZUHIRO SUGIYAMA?’ "Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Aramaki, Aoba, Aoba-ku, Sendai, 980-8587, Japan ‘Marine Geology Department, Geological Survey of Japan, Tsukuba, 305-8567, Japan. Received 17 July 2000; Revised manuscript accepted 12 April 2001 Abstract. The physiological ecology of a spherical polycystine species, Diplosphaera hexagonalis collected from the surface water of the Kuroshio Current in the East China Sea off Sesoko Island, Okinawa, was observed in a culture dish for three days. The observed specimen demonstrated cy- clic extension and contraction of axopodia by a regular interval of ca. 630 seconds. Each cycle was divided intro four phases based on the state of the axopodia and movement of axopodial vacu- oles. Vertical migration in response to axopodial motility was also observed. The specimen began to rise accompanied with the axopodial extension, floated in the seawater and often moved horizontally when its axopodia were radiated symmetrically, and began to sink in correspondence with the axopodial contraction. The effect of thermal currents on this behavior is easily neglected on the ground of the definite coincidence with the rhythmic extension and contraction of axopodia. The rhythm appears to play important roles in the physiological ecology of this species, including food capture and possibly buoyancy. The taxonomic section presents a nearly complete synonym list of D. hexagonalis and summarizes that the genus Diplosphaera is a senior synonym of Astrosphaera, Drymosphaera and Leptosphaera. Thus, Diplosphaera hexagonalis is the only valid name for this species, according to ICZN Article 55.3. Diplosphaera is considered herein to belong not to the family Actinommidae but to the Astrosphaeridae, unlike in most previous paleontological and biological studies. The family Macrosphaeridae Hollande and Enjumet, 1960, to which the genus Diplosphaera was assigned, is treated as an invalid name because the type genus Macrosphaera has not been established yet. Key words: axopodia, Diplosphaera hexagonalis, East China Sea, living radiolaria, Okinawa, physiological ecology Introduction Radiolaria is an informal taxonomic group of planktonic unicellular Protoctista generally possessing a plane, line or point skeletal symmetry of the test. This group includes the classes Polycystina possessing a siliceous test, Acantharia with a strontium sulfate test, and Phaeodaria having a sili- ceous test with incorporated organic substances (Margulis and Schwartz, 1988; The Committee on Systematics and Evolution of the Society of Protozoologists, 1980). Of these radiolarians, solitary spheroidal Polycystina ranges in age from the middie Cambrian to the present (Nazarov, 1988). Since the polycystine group is widely distributed in the open oceans, information on its physiological ecology will provide new insights both in analysis of paleoceanographic analyses and the establishment of a natural classification. Although previous studies have revealed detailed informa- tion on physiological and ecological information (living fea- tures, longevity, prey, and skeletal growth under culture conditions and some fine structures) of some discoidal spumellarians such as Dictyocoryne truncatum (Ehrenberg) and Spongaster tetras (Haeckel) (e.g. Anderson et al. 1989a, 1989b; Anderson and Matsuoka, 1992; Matsuoka, 1992; Matsuoka and Anderson, 1992; Sugiyama and Anderson, 1997), we know little about the physiological ecol- ogy of spheroidal spumellarians. Examination of the cytol- ogical structures of solitary spherical polycystines has provided some groundwork for these analyses (Anderson, 1976, 1981, 1983; Anderson et al., 1998; Cachon and Cachon, 1972a, 1972b, 1976, 1985; Haeckel, 1862; Haecker, 1907; Hertwig, 1879, 1932; Hollande and Enjumet, 1954, 1960; Hollande et a/., 1965; Swanberg et a/., 1990), 132 Noritoshi Suzuki and Kazuhiro Sugiyama Okinawa 130 E Islands 125° E Figure 1. adjacent islands. C. The sampling location (solid circle). but there have been only limited investigations of the nutri- tional role of symbionts (Anderson et al., 1983, 1985) and the possible reproductive role of swarm cells released by mature specimens during laboratory culture (Anderson, 1978, 1984 and others). In order to observe living features of radiolarians in the surface seawater of the Kuroshio Current, some Japanese radiolarian paleontologists have collaborated on observation tours of living organisms at the Sesoko Tropical Biosphere Research Center (STBRC), University of the Ryukyus, Sesoko Island, Okinawa Prefecture, Southwest Japan, since 1997 (Figure 1). During the 2nd tour held on October 5th to 14th, 1998, we made three samplings on October 7th, 8th and 12th, 1998, and encountered approximately 40 species in laboratory examinations. As a result, we obtained exten- sive information about their pseudopodial behavior using normal still and video photography. Among the observed radiolarians, we particularly traced continuous axopodial activity of one specimen of Diplosphaera hexagonalis Haeckel, a solitary spheroidal spumellarian representative of the observed radiolarian fauna, during four days from October 7th to 10th, 1998. Our interest was especially aroused since it systematically re- peated axopodial extension and contraction cycles at regular intervals. In this report, we present a detailed description of the features of the extension and contraction cycles and possible implication for the physiological ecology of D. hexagonalis in relation to this cyclical axopodial activity. A probable physiological function and an explanation of a mechanism of the cycles are also discussed. This paper also describes the taxonomic classification of D. hexagonalis in order to resolve the confusion surrounding its generic and family positions. Sampling location. A. A map showing the position of Okinawa Islands (open square). B. The Okinawa Islands and its Materials and methods Plankton samples containing the observed Diplosphaera hexagonalis were collected on October 7th, 1998, at a local- ity (Station 1; Figure 1) approximately 12 km west of Sesoko Island and more or less affected by the warm-water Kuroshio Current. Ambient seawater temperature and sa- linity at the sampling location were 28.5 °C and 34.0 %s, re- spectively. The sample was collected by 3 min. tow using a 36 um mesh net. On return to the laboratory at STBRC, small portions of the sample were placed into sorting dishes, examined with binocular microscopes, and each individual radiolarian was separated from other matter using a Pasteur pipette into a glass vial (ca. 25 mm diam. x50 mm tall), a glass culture dish (50 mm or 90 mm diam.) or a single well of a multiwell tissue culture plate (23 mm diam. x20 mm tall) (FALCON® 3043, Becton Dickinson Labware, Lincoln Park, N. J.) previously filled with ambient seawater from the sam- pling location. These culture containers with radiolarians were placed either in a temperature-controlled bath with fluorescent light units or in temperature-uncontrolled baths without fluorescent light units. The temperature of the for- mer bath was kept at 28 °C by a heater-chiller balance, whereas that of the latter was about 27 °C, the room tem- perature of the laboratory, throughout the culture work. Both types of baths were covered by metal foil during the night to produce a day/night cycle. The radiolarians were cultured without exchange of the seawater, no supply of food, nor removal of any filth. Continuous axopodial activity of one D. hexagonalis indi- vidual was observed from October 7th to 10th October, 1998, using Nikon Diaphot and Olympus CK2 inverted mi- croscopes, mainly following previously established protocols Axopodial activity of Spumellaria 133 (Anderson et al., 1989a). We used a video camera (SONY HANDYCAM DCR-TRV9), with a resolution of 0.76 million pixels, attached to the Nikon Diaphot microscope through a TV adapter and digital camera (FUJIFIX HC-300) in order to record vivid images of radiolarian activity. The observations were recorded on five 60-minute videotapes and more than 10 pictures. Only for one individual was the continuous axopodial activity described in this paper ascertained. Although six to ten other individuals were observed with two inverted microscopes for snapshots using normal cameras as well, we did not confirm whether other specimens show continuous axopodial behavior or not. Aust Observational results of living Diplosphaera hexago- nalis The skeleton of Diplosphaera hexagonalis (Figure 2.1) consists of one spherical primus exosphere, one polyhedral secondus exosphere with triangular frameworks, and a dozen triradiate auxiliary spines radiating from the primus exosphere (for skeletal terms see Suzuki, 1998). This spe- cies was assigned to the family Astrosphaeridae based on criteria published by Hollande and Enjumet (1960). Living D. hexagonalis possesses a dark, grayish red, spherical cell body within the secondus exosphere, and fine, transparent axopodia radiating from the surface of the cell body (Figure 2.2, 2.3). The spherical cell is composed of faye ae ‘ en Figure 2. General view of Diplosphaera hexagonalis Haeckel. 1. Light transmitted microscopic photograph. 2-4. Inverted micro- Scopic photographs, showing a bottom view. Scale bars are equal to 100 pm. 1. Skeleton structure of D. hexagonalis possessing a spherical primus exosphere (pri) and a polygonal frame of the secondus exosphere (sec). These two shells are connected with numer- ous auxiliary spines (aux). 2. Numerous yellow-brown axopodial vacuoles surround the endoplasm. Axopodia may begin to extend (Ell-subphase). 3. This specimen has a small amount of axopodial vacuoles. Both the fine axopodia and axopodial vacuoles near the endoplasm indicate that this specimen is in the El-subphase. 4. A copepod attached to D. hexagonalis is partially digested by the speci- men. Abbreviations: nuc, nucleus; end, endoplasm; cop, copepod; ect, ectoplasm; axo, axopodia; aux, auxiliary spine; axv, axopodium vacuole; pri, primus exosphere. 134 Noritoshi Suzuki and Kazuhiro Sugiyama two parts: (1) a more transparent light-colored, bubble-like outer part between the primus and secondus exospheres, corresponding to ectoplasm, and (2) amore opaque, spheri- cal inner part within the primus exosphere. The latter is fur- ther subdivided into a deeper-colored central part, and the surrounding endoplasm which is slightly lighter-colored. The inner part is referred to as a nucleus according to Hollande and Enjumet (1960). The length of the axopodia changes periodically from a minimum of 0.12-0.13 mm to longer than 2.0 mm. Vacuoles, dark amber or reddish gray in color, globular in shape and of a few to ten um in diameter are displayed on each axopodium. The total number of vacuoles varies among specimens but it typically is about 200. The distribu- tion of the vacuoles on the axopodia changes with the length ofthe axopodia. The biological function and physical com- position remains unknown. We observed the specimen with a copepod (ca. 400 um in length) attached to its axopodia outside the secondus exo- sphere at noon on the 7th (Figure 2.4). On the next day, the entrails of the copepod began to dissolve, and the entire co- pepod body completely disappeared on October 9th. After the digestion of the copepod, the ectoplasm of D. hexagonalis increased in volume to fill the secondus exo- sphere. During the observations, other organisms, proba- bly ciliates, moved around the halo of axopodia of D. hexagonalis, and became momentarily immobilized on the axopodia. However, all of these microorganisms were soon released by the shortening of the axopodia. This seems to indicate that these microorganisms were not captured but only snared accidentally. Some of the microorganisms es- caped from D. hexagonalis, but those which failed to escape from the specimen were again snared by the axopodia. Systematic repetition pattern of axopodial extension and contraction On October 9th, a series of 17 extension and contraction cycles of the axopodia was observed over a duration of 2 hrs. 44 min. 21 sec. (Figure 4). The cycles described herein have a reasonably regular interval; the longest interval was 677 sec, the shortest 550 sec and the mean 633 sec. Each cycle is divisible into four phases based on the state of the axopodia and movement of axopodial vacuoles. These phases are as follows: S-phase (short phase, Figures 3.1, 5), E-phase (extension phase, Figures 3.2-3.5, 5), L-phase (long phase, Figures 3.6-3.7, 5) and C-phase (contraction phase, Figres 3.8-3.12, 5). Among them, the E-phase is further subdivided into three subphases (El-subphase, Ell- subphase and Elll-subphase), and the C-phase into two subphases (Cl-subphase and Cll-subphase). Although each cycle has almost the same interval, as mentioned above, phase and subphase intervals in each cycle differ considerably as shown in Figure 4. We tried to interrupt the axopodial movement by vibrations produced by tapping the dish with sticks but the cyclicity was uninterrupted, and what is more, the regularity was maintained in spite of contact by ciliates and other small organisms. S-phase (Figure 3.1).—This phase is defined as an inter- val after C-phase, during which axopodial length is at a mini- mum. Axopodia in this phase are composed of two kinds; one is named H-index type and the other is L-index type. The former type of axopodia has relatively high refractive index against seawater under the microscope, whereas the refractive index of the latter type is lower. Usually, H-index type axopodia are shorter than the L-index type in this phase. The length of the H-index type axopodia is about half of the primus exosphere diameter, while that of the L- index type axopodia is approximately double that of the H- index type. In this phase, most vacuoles on both types of axopodia are rarely moved outside the ectoplasm. The shortest interval of this phase is 4 sec, the longest 18 sec and the mean 12 sec. E-phase.— This phase is defined as an interval after S- phase, during which most axopodia are extending. The shortest interval of this phase is 160 sec, the longest 474 sec and the mean 302 sec. The E-phase is subdivided into the following El-, Ell- and Elll-subphases. During the El-subphase, we still cannot see the outward movement of the axopodial vacuoles situated in the secondus exosphere (Figure 3.2). In contrast, vacuoles on the L-index type axopodia begin to move slowly inwards. H-index type axopodia begin to extend slowly and become more slender. The refractive index of both types of axopodia decreases with their extension. During this subphase, the difference between the L- and H- type axopodia becomes indistinct. The shortest interval of this subphase is 14 sec, the longest 86 sec and the mean 31 Sec. The Ell-subphase starts by the outward movement of axopodial vacuoles, and ends by the event that the distal parts of axopodia become invisible (Figure 3.3). Within this subphase the axopodia maintain a continuous and slow ex- tension. Most axopodial vacuoles continue to move out- ward, but a few return to the inside of the secondus exosphere. The shortest interval of this subphase is 2 sec, the longest 140 sec and the mean 85 sec. The end of the subsequent Elll-subphase is defined by unrecognizableness of the outward extension of axopodia (Figure 3.4, 3.5). During this subphase, the distal parts of axopodia are invisible but the outward extension can be dis- cerned by the movement of axopodial vacuoles. The short- est interval of this subphase is 46 sec, the longest 433 sec and the mean 217 sec. L-phase (Figure 3.6, 3.7).—This phase is defined as an in- terval during which the specimen keeps radiate, long axopodia with immobile vacuoles. Axopodia in this phase are finer than those in the S-phase, and the refractive differ- ence between the axopodia and seawater is negligible. Axopodial vacuoles are heterogeneously distributed around the halo of axopodia. The shortest interval of this phase is 29 sec, the longest 205 sec and the mean 100 sec. C-phase. —This phase subsequent to the L-phase is marked by an abrupt contraction of axopodia towards the endoplasm, and ends when most axopodia finish shrinking. The shortest interval of this phase is 59 sec, the longest 282 sec and the mean 168 sec. This phase is subdivided into Cl- and Cll-subphases as follows. In the Cl-subphase, axopodial vacuoles begin to be moved back to the ectoplasm although the axopodia are not Axopodial activity of Spumellaria 135 IE 0 © DE 08PA Figure 3. Four phases of extension and contraction of the axopodia. Scale bar is equal to 100 um. 1.S-phase. 2. El-subphase. 3. Ell-subphase. 4, 5. Elll-subphase. 6, 7. L-phase. 8, 9. Cl-subphase. 10-12. Cil-subphase. Arrows: a, the periphery of the dominant axopodial vacuoles; b, the distal part of H-index type axopodia; c, the distal part of L-index type axopodia; and d, the distal part of the contractile axopodia. Open circles with Greek symbols in Figure 3.4-3.9 represent axopodial vacuoles. The same Greek sym- bols in different figures imply the same axopodial vacuole. yet contracted (Figure 3.8, 3.9). During this subphase the refractive index of the axopodia increases gradually accom- panied by thickening of the axopodial diameter at the proxi- mal point where it attaches to the cell body. A few axopodial vacuoles are moved inward relatively quickly. These vacuoles pass the secondus exosphere and reach near the surface of endoplasm. The shortest interval of this subphase is 34 sec, the longest 227 sec and the mean 133 sec. The Cll-subphase is characterized by an abrupt contrac- tion of axopodia and followed by the S-phase after complete cessation of axopodial shrinking. At the beginning of this 136 Noritoshi Suzuki and Kazuhiro Sugiyama Time (seconds) | a 600 SA 2 550 sec = 5 re | | = 599 sec 4 659 sec 5 oo Eee [I 654 sec : x © 6 | = = co Ù ; > | 634 sec I" 646 sec 9 8 = 10 = uam > DAT de 4 EI | Ri Time (seconds) RR 617 sec ST Sl vo 2 MB EEK 631 see > 0 7 N RR SZ HN 927 sec 16 AU EHE TT BAT Average ll FA 633 sec Phase (lu Mr beginnig of video end of video end of record start rising start sinking reach to the bottom = move horizontally gradual change between phases Figure 4. Diagram illustrating the four phases of the axopodia on 9th, Oct, 1998. subphase, the periphery of the axopodia shrinks suddenly (arrow d in the Figure 3.10-3.12). The vacuoles on the distal part of the axopodia are moved inwards by this action, and the refractive index of the axopodia increases immedi- ately (Figure 3.10). Subsequently, the axopodia shorten in a stepwise fashion with a concomitant increase of the refrac- tive index at each step. The axopodial vacuoles are also moved inwards in the same stepwise fashion. The halo of axopodia in this subphase has a gelatinous spherical enve- lope with numerous pigmented dots (Figure 3.11). The shortest portion of this subphase is 25 sec, the longest 90 sec and the mean 64 sec. Vertical migration in connection to axopodial motility During the observation of Diplosphaera hexagonalis, we found that rising, floating and sinking motions in the culture vessel are always related to axopodial extension and con- traction. Vertical migration was confirmed with video re- cords and was counted 14 times at each expansion and contraction rhythm of the axopodia except for the last two rhythmic cycles which were not recorded on the video tape (Figure 4). It would be doubtful if this behavior depended on the effect of thermal currents in the observed dish, but the possibility of this effect is easily discarded: the relation of floating and sinking correlated with the changes in axopodial rhythm is so strict, and the radiolarian specimen did not show any other irregular rising and sinking movement in spite of particular careful observation as shown in Figure 4. The specimen begins to rise from the bottom of the vessel during the interval from the middle El-subphase to early Ell- subphase accompanied with the axopodial extension (the up-arrows in Figure 4). Cessation of this movement is quite gradual. The specimen floats in the seawater and often moves horizontally during the Ell-subphase through the mid- die Cll subphase (the open rectangles in Figure 4). When the specimen is floating, its axopodia are radiated symmetri- Axopodial activity of Spumellaria 137 Average Phase tt E Time (seconds) 0 Figure 5. Schematic illustration of the cycle of extension and contraction of the axopodia. Solid fine line: H-index type axopodia. Dark gray small dot: axopodium vacuole. LA NE Be En | Solid thick line: siliceous skeleton. Dark to light gray fine lines: L-index type axopodia. The darkness of lines indicates a refractive index between the axopodia and the seawater. cally from the cell body, which drifts in all directions very slowly. Around the late Cl-subphase to the early CII- subphase, the specimen begins to sink in correspondence with the axopodial contraction (the down-arrows in Figure 4). After a few to 60 seconds, the body of the specimen reaches the bottom of the culture vessel. Discussion Although a rhythmic extension and contraction of radiolar- ian axopodia has been reported by Anderson (1983), the ob- servation herein is the first evidence showing a regular rhythm of axopodial movement at approximately ten and a half-minute intervals. Our observation demonstrated that videotape recording is a fairly useful and advanced method by which to document the continuous activities of radiolarian axopodia. We accumulated a continuous record of D. hexagonalis with cyclic axopodial motions only from one specimen using videotapes, but other collected specimens (more than ten specimens) also appeared to have the same kind of rhythmical activity, judging from a series of still photo- graph images. Consequently, we can conclude that the above described cyclical motions are a common physical behavior of D. hexagonalis. Spherical symmetry is probably not a major predictive fac- tor in the occurrence of the regular, cyclical axopodial con- tractions observed in D. hexagonalis. Several spherical spumellarian species of genera with a double shell (e.g. Hexacontium spp. and Spongodrymus sp. indet.) also were observed during this experiment, but they never exhibited a similar rhythmic motion of the axopodial array. Likewise, other protista, including Acantharia and Heliozoa, have a symmetric distribution of axopodia around the cell body, but we have no information if they possess possible cyclical pat- terns as observed in D. hexagonalis. Currently, therefore, we can infer that the observed regular rhythm is peculiar to D. hexagonalis and its related taxa, and that a particular cy- tological apparatus of D. hexagonalis likely produces this rhythm. The cytology of D. hexagonalis is unusual. There is no axoplast and the nucleus is surrounded by large vacuoles (Hollande and Enjumet, 1960). However, as with other axopodial-bearing species, the axopodium contains an array of axially oriented internal microtubules (axoneme). An axoplast is absent also in other spherical polycystine genera including Rhizoplegma, Centrocubus, Octodendron and Haplosphaera (Cachon and Cachon, 1985). It is not known presently whether the absence of an axoplast is related to the regular rhythmic cycles of extension and contraction of the axopodia in D. hexagonalis. When the axoplast is pres- ent in other species, it is rich in tubulin monomers that po- lymerize to form microtubules and is usually located centrally where the microtubules of the axonemes converge. Hence, the axoplast may provide an organizing center for the axonemes. In the absence of an axoplast, the regular array of large vacuoles in D. hexagonalis could serve to sup- port the axonemes and in addition may contribute to the cytoplasmic volume as the periphery array of axopodia ex- pands. Ifthe expansion of the axopodial array indeed con- tributes to enhanced buoyancy, then there must be a source of additional cytoplasmic volume to supply the added low- density mass produced by the expansion of the peripheral corona of axopodia. Ifthe expanding axopodia were simply constructed at the expanse of existing cytoplasmic mass in the main cell body, without further expansion of internal vol- ume, there would be no net gain in buoyancy. If, however, the vacuoles increase in size as the axopodia expand, this could result in less mass per unit volume, and produce an in- creased buoyancy. Likewise, according to this model, as the axopodia contract, the vacuoles may decrease in vol- ume, thus accommodating the inward flow of cytoplasm to- ward the central body and producing a concomitant decrease in buoyancy. A dynamic adjustment in volume by the central vacuoles may provide a necessary mechanism for maintaining appropriate mass balance required to control buoyancy as the peripheral axopodial array expands and contracts. The rhythmic extension and contraction of the axopodia appear to play important roles in the physiological ecology and physical functioning of D. hexagonalis, includ- ing food capture and possibly the regulation of buoyancy as reported here. The extension of protozoan axopodia usually occurs by 138 Noritoshi Suzuki and Kazuhiro Sugiyama elongation of the microtubules when additional tubulin is po- Iymerized at one end and they are shortened by disassem- bly of the tubulin, all in response to biochemically regulated cycles (e.g., Tilney and Byers, 1969). To understand the mechanism of the observed rhythmic extension and contrac- tion of axopodia, it is essential to investigate more thor- oughly changes in cytological structures and correlated biochemical processes with the aim of creating a more com- plete model of the rhythmic activity of axopodia in D. hexagonalis. Systematic description Family Astrosphaeridae Haeckel 1882, sensu Hollande and Enjumet 1960 Genus Diplosphaera Haeckel 1860, emend. Hollande and Enjumet, 1960 Type species.—Astrosphaera gracilis Haeckel 1862, des- ignated by Campbell (1954). Diplosphaera Haeckel, 1860, p. 804; Haeckel 1887, p. 246; Campbell, 1954, D.62; Hollande and Enjumet, 1960, p. 116; Kozur and Mostler, 1979, p. 12. Astrosphaera Haeckel 1887, p. 250; Campbell, 1954, D61. Drymosphaera Haeckel 1882, p. 452; Haeckel 1887, p. 248; Campbell, 1954, D.62. Leptosphaera Haeckel, 1887, p. 243-244; Campbell, 1954, D.62. Remarks.— Diplosphaera is regarded as the senior syno- nym of three other genera, Astrosphaera, Drymosphaera and Leptosphaera, based on the ontogenetic growth change of their skeletal structures and similarity of their cytological structures (Hollande and Enjumet, 1960). According to them, the Leptosphaera-form, the youngest, possesses two exospheres without by-spines. Diplosphaera- and Drymosphaera- forms appear in the next ontogenetic growth stage through the development of by-spines on one of these. When both exospheres have by-spines, this form is referred as an Astrosphaera-form. Diplosphaera has been assigned to three different fami- lies: classical studies described it as a member of the Astrosphaeridae Haeckel 1882 (e.g. Haeckel, 1882, 1887; Campbell, 1954; Mast, 1910). Recent paleontologists and paleoceanographers prefer to assign it to the Actinommidae Haeckel 1862 (e.g. Kozur and Mostler, 1979; Takahashi, 1991). Finally, cytological researchers have regarded it as a member of “Macrosphaeridae” Hollande and Enjumet 1960 (e.g. Anderson, 1983; Cachon and Cachon, 1985; Hollande and Enjumet, 1960). However, since Macro- sphaera had not been proposed as a genus name, the fam- ily name “Macrosphaeridae” violates Art 29.1 of ICZN (1999), which states that a family-group name is formed by adding the termination -idae to the stem of the name of the type genus, or to the entire name of the type genus. Diplosphaera is cytologically closely similar to the genus Haplosphaera Hollande and Enjumet 1960, the type genus of the “Macrosphaeridae” (Hollande and Enjumet, 1960). The phylogenetically close relationship between Diplosphaera and Haplosphaera suggests that the family “Macrosphaeridae” is included in the Astrosphaeridae. Hollande and Enjumet (1960) revealed that the genus Actinomma Haeckel 1862, the type genus of the Actinommidae, is one of the centroaxoplastid spumellarians with the axoplast enclosed by the nuclear membranous en- velope, whereas the genus Diplosphaera of the Astrosphaeridae belongs to the anaxoplastid spumellarians without axoplast. This cytological difference between the Actinommidae and Astrosphaeridae suggests that Diplosphaera does not belong to the Actinommidae. Almost all species assigned to Diplosphaera have been recovered from surface sediment or plankton samples due to their fragile skeletons. Only one species, Drymosphaera ? pseudosagenoscena Sugiyama 1992, is known from the lower Miocene (Sugiyama, 1992). All assigned species other than D.? pseudosagenoscena lack a microsphere, so that the lower Miocene species appears to belong to another genus. Range.—Recent as far as known. Known occurrence.—Equatorial and North Pacific, equa- torial Atlantic and Mediterranean. Diplosphaera hexagonalis Haeckel, 1887 Diplosphaera hexagonalis Haeckel 1887, p. 246, pl. 19, fig. 3; Hollande and Enjumet, 1960, p. 116, pl. 12, fig. 6, pl. 15, fig. 11, pl. 23, fig. 2, pl. 26, fig. 2: Cachon and Cachon, 1972a, pl. 35, figs. b, c; Anderson, 1983, p. 66-67; Fujioka, 1990, p. 136, pl. 39, fig. 7. Astrosphaera hexagonalis Haeckel 1887, p. 250, pl. 19, fig. 4; Mast, 1910, p. 52; Popofsky, 1912, p. 105-106, text-fig. 16, pl. 8, fig. 2; Sugano, 1937, p. 64, figs. 21; Renz, 1976, p. 100-101, pl. 2, fig. 12; Tan and Tchang, 1976, p. 229, figs. 4a, b; Takahashi and Honjo, 1981, p. 147, pl. 2, fig. 12; Nishimura and Yamauchi, 1984, p. 24, pl. 14, figs. 1, 2; Boltovskoy and Jankilevich, 1985, pl. 1, fig. 17; Yamauchi, 1986, pl. 2, fig. 3; Fujioka, 1990, p. 136, pl. 38, fig. 7; Yeh and Cheng, 1990, pl. 3, fig. 2; Takahashi, 1991, p. 69, pl. 11, figs. 1-3; Boltovskoy, Alder and Abelmann, 1993, p. 1891; Tan, 1998, p. 164, figs. 152a, b (= the same figures of Tan and Tchang, 1976); Boltovskoy, 1998, p. 41, figs. 15-40. Leptosphaera hexagonalis Haeckel 1887, p. 244, pl. 19, fig. 2. [nomen oblitum] Remarks. — Most previous authors have identified D. hexagonalis as a species of Astrosphaera. As mentioned in the generic remarks, Astrosphaera is a junior synonym of the genus Diplosphaera (Hollande and Enjumet, 1960; Kozur and Mostler, 1979), which means that Astrosphaera hexagonalis is an unavailable name (Article 53.3 of ICZN, 1999). Thus, Diplosphaera hexagonalis is the valid name of this species. Skeletal residues are obtained from surface sediment in the eastern Pacific Ocean, China Sea, and the Mediterranean (Tan and Tchang, 1976; Nishimura and Yamauchi, 1984), whereas they are not found in the sedi- ment from the center of the equatorial Pacific (Renz, 1976; Takahashi, 1991). The skeleton of this species appears to dissolve easily at greater water depth as discussed by Takahashi (1991). Axopodial activity of Spumellaria Known Range.—Recent. Occurrences.—Equatorial Pacific, equatorial Atlantic, East China Sea, South China Sea, east off Okinawa, Shikoku and Taiwan, Mediterranean and west Patagonia. Habitat.—Warm seawater. Surface to 300 m depth (Hollande and Enjumet, 1960; Renz, 1976). Acknowledgements We wish to thank the personnel of the Sesoko Tropical Biosphere Research Center, University of the Ryukyus, for their kind hospitality and great help with sampling and cul- ture work. In particular, proficient steerage by Yoshikatsu Nakano was very helpful. This research is a result of the 2nd Observation Tour of Living Radiolarians at Sesoko Island presided over by Atsushi Matsuoka (Niigata Univ.). We express our hearty thanks to him for his direction and great help on the tour, critical reading of the manuscript and valuable advice through the study. We extend our appre- ciation to Rie S. Hori (Ehime Univ.), Sayoko Nakamura (Hiroshima Univ.), Kazuko Usami (Hokkaido Univ.) and all the other participants of the tour for their kind help with sam- ple collection and daily laboratory work. We are indebted to Isao Motoyama (University of Tsukuba) and his students for their kind assistance during the tour. Our thanks also go to Barry O'Connor (Utsunomiya Univ.) for his kind editing of the English in the first draft. Roger O. Anderson (Columbia Univ.) reviewed the manuscript and provided useful com- ments. This research was partly funded by a Grant-in-aid for JSPS Fellows from the Ministry of Education, Sciences and Culture of Japan for Suzuki (No. 5496) and by a Domestic Research Fellowship from the Japan Science and Technology Corporation for Sugiyama. References Anderson, O. R., 1976: A cytoplasmic fine-structure study of two spumellarian Radiolaria and their symbionts. Marine Micropaleontology, vol. 1, p. 81-99. Anderson, O. R., 1978: Light and electron microscopic obser- vations of feeding behavior, nutrition, and reproduction in laboratory cultures of Thalassicolla nucleata. Tissue and Cell, vol. 10, p. 401-412. Anderson, O. R., 1981: Radiolarian fine structure and silica deposition. In, Simpson, T. L. and Volcani, B. 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Factors controlling the organization of microtubules in the axonemal pattern in Euchinosphaerium (Actinosphaerium) nucleofilum. Journal of Cell Biology, vol. 43, p. 148-165. Yamauchi, M., 1986: The distribution of radiolarian assem- blages in surface sediments from the northwestern Pacific. News of Osaka Micropaleontologists, Special Volume, no, 7, p. 141-156. Yeh, K-Y. and Cheng, Y-N., 1990: Radiolaria in surface sedi- ments from marginal basin off southwest Taiwan. Bulletin of National Museum of Natural Science, no, 2, p. 65-87. 141 The Palaeontological Society of Japan has revitalized its journal. Now entitled Paleontological Research, and published in English, its scope and aims have entirely been redefined. The journal now ac- cepts and publishes any international manuscript meeting the Society's scientific and editorial standards. 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If a paper exceeds 24 printed pages, payment of page charges for ine extra pages is a prerequisite for acceptance. Illustrations in color can also be published at the authors’ expense. For either case, the editors will provide infomation about current page charges. Return of published figures. The manuscripts of the papers pub- lished will not be returned to the authors. However, figures will be returned upon request by the authors after the paper has been pub- lished. Ager, D. V., 1963: Principles of Paleoecology, 371p. McGraw- Hill Co., New York. Barron, J. A., 1983: Latest Oligocene through early Middle Miocene diatom biostratigraphy of the eastern tropical Pacific. Marine Micropaleontology, vol. 7, p. 487-515. Barron, J. A., 1989: Lower Miocene to Quatemary diatom biostratigraphy of Leg 57, off northeastern Japan, Deep Sea Drilling Project. /n, Scientific Party, Initial Reports of the Deep Sea Drilling Project, vols, 56 and 57, p. 641-685. U. S. Govt. Printing Office, Washington, D. C. Burckle, L. H., 1978: Marine diatoms. In, Haq, B. U. and Boersma, A. eds., Introduction to Marine Micropaleon- tology, p. 245-266. Elsevier, New York. Fenner, J. and Mikkelsen, N., 1990: Eccene-Oligocene diatoms in the westem Indian Ocean: Taxonomy, stratigraphy, and paleoecology. In, Duncan, R. A., Backman, J., Peterson, L. C., et al, Proceedings of the Ocean Drilling Program, Scientific Results, vol. 115, p. 433-463. College Station, TX (Ocean Drilling Program). Kuramoto, S., 1996: Geophysical investigation for methane hy- drates and the significance of BSR. The Journal of the Geological Soclety of Japan, vol. 11, p. 951-958. (in Japanese with English abstract) Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey (A new find of an ammonoid jaw ap- paratus). Paleontologicheskii Zhurnal 1974, p. 127-129. (in Russian) ÎT & ÿ EF O$151HFI2t4, 20024 1 A268 (+), 15278 (8) TÉREKÉEENTAEX NES. 1 H27H (A) FRIABSBRELT [21H RÉEDORRÉR -—HEME- 7 4 — 0 FFFÉDOORES— : tt A, À B- ABET!) ZRH LE FT. BRO LAS MWIIL11H308 (&) TE. ©2002 FS - BS (2002 7 A EAB TE) (CSFII RE TSI D D BAER LUE 0 & LH. SA, F132EAl& (20034 1A FABÉTE) CRB VASA ARE 2 BAH LIAA DS MO UT. OHÆMELTE, NAMCHHMENSZI-DPvav7FPVYa-—bIA-REERLTHEVEF. FEDS SRAESCEMATEICEMCREFOC, SHEERS OAITSRE CHHVGH FEU, (ABB - VY RVD LRBORLASAAE BABBO LASS PRBERB*zBETASRABKY FAW. e-mail ? 7 7 » 7 ACOMLUS IX, BRIE LCRUGHITHEV ERA, 7240-0067 ATRL T AKEHRATI-2 BEEVASASAMES SA ARE TEL 045-339-3349 (i838) FAX 045-339-3264 (FHEFZ) E-mail majima@edhs.ynu.ac.jp EUR (TSH) SHOAL, TERS PsacOTBHRBE CHA FEU. T 250-0031 /) HJR A4 499 HSE WHERGOR - HER MRE TEL 0465-21-1515 FAX 0465-23-8846 E-mail taru @pat-net.ne.jp % 8 (TER) IDEDEDTEDT DT DT DT DL DE DL DE DE DE DE DE DE DE GDC DE DE DE DE DE DE DE DE DL DE DE DE DL GT DE GDC DL DE DE DE DI DEE ASEORITICRG SHAS, BROLBVA, MSA RARES SULENZADSOSH BATSNCWET, HEOBWMSR Is Fac TF, AYFAVTAHRMR LH ASIIEVÆGOE - HERS IETUINA ARS Be HMARRMARAAH FAA MRA LH RERVALCABAOR MSE $a-Y7TLN-IRRBBREME (7 1 © z #IÉ) OXBERFHARAIE (DA APE) IK 2. aa DB BE BB EM S & 201F#6A2BE DM Mi 7113-8622 RACK ABIIAS-16-9 2001 65 298 FE 47 HAFABBRe » 4 - A GHG 03-5814-5801 feet M 4 — 1 - MEERE BR ÉÉÉE BRO MRM: exe KEE nas Al fl &F #HRENRIHRSH EM RB 2,5009 T176-0012 #RARBEKSEIL201301 BE 03-3991-3754 ISSN 1342-8144 Paleontological Research N LIBRARIES nina Paleontological Research Vol. 5, No. 2 June 29, 2001 CONTENTS Mohamed Zakhera, Ahmed Kassab and Kiyotaka Chinzei: Hyotissocameleo, a new Cretaceous oyster subgenus and its shell microstructure, from Wadi Tarfa, Eastern Desert of Egypt :::::::::- Wi Michiko Saito and Kazuyoshi Endo: Molecular phylogeny and morphological evolution of laqueoid brachiopods +++ +++ +++ +++ ttt teen eee eee 87 Fumihisa Kawabe and Yasunari Shigeta: The genus Hourcquia (Ammonoidea, Pseudotissotiidae) from the Upper Cretaceous of Hokkaido, Japan: biostratigraphic and biogeographic implications ---- 101 Masayuki Ehiro: Some additional Wuchiapingian (Late Permian) ammonoids from the Southern Kitakami Massif, Northeast Japan ---::---::---............................................. 111 Shuji Niko: Middle Carboniferous orthoconic cephalopods from the Omi Limestone Group, Central Toshifumi Komatsu, Ryo Saito and Franz T. Fursich: Mode of occurrence and composition of bi- valves of the Middle Jurassic Mitarai Formation, Tetori Group, Japan :-:-:::::-::--:::--:::::..:.. 1121 Noritoshi Suzuki and Kazuhiro Sugiyama: Regular axopodial activity of Diplosphaera hexagonalis Haeckel (spheroidal spumellarian, Radiolaria) 0000000000000000008000000600000008000000000009000 131 PROCEEDINGS: : - 4.444 141 aleontological Research ISSN 1342-8144 Formerly Transactions and Proceedings of the Palaeontological Society of Japan Vol. 5 No.3 September 2001 The Palaeontological Society of Japan Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Alan G. Beu (Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato (Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto University, Kyoto, Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain), Roger D. K. Thomas (Franklin and Marshall College, Lancaster, USA), Katsumi Ueno (Fukuoka University, Fukuoka, Japan), Wang Hongzhen (China University of Geosciences, Beijing, China), Yang Seong Young (Kyungpook National University, Taegu, Korea) Officers for 2001-2002 President: Hiromichi Hirano Councillors: Shuko Adachi, Kazutaka Amano, Yoshio Ando, Masatoshi Goto, Hiromichi Hirano, Yasuo Kondo, Noriyuki Ikeya, Tomoki Kase, Hiroshi Kitazato, Itaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Kei Mori, Hirotsugu Nishi, Hiroshi Noda, Kenshiro Ogasawara, Tatsuo Oji, Hisatake Okada, Tomowo Ozawa, Takeshi Setoguchi, Kazushige Tanabe, Yukimitsu Tomida, Kazuhiko Uemura, Akira Yao Members of Standing Committee: Makoto Manabe (General Affairs), Tatsuo Oji (Liaison Officer), Shuko Adachi (Finance), Kazushige Tanabe (Editor in Chief, PR), Tomoki Kase (Co-Editor, PR), Kenshiro Ogasawara (Planning), Yoshio Ando (Membership), Hiroshi Kitazato (Foreign Affairs), Haruyoshi Maeda (Publicity Officer), Ryuichi Majima (Editor, "Fossils"), Yukimitsu Tomida (Editor in Chief, Special Papers), Tamiko Ohana (Representative, Friends of Fossils). 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Phone: | (978)750-8400, Fax: (978)750-4744, www.copyright.com Cover: Idealized sketch of Nipponites mirabilis Yabe, a Late Cretaceous (Turonian) nostoceratid ammonite. Various reconstructions of the mode of life of this species have been proposed, because of its curiously meandering shell form (after T. Okamoto, 1988). All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16-9, Bunkyo-ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp/palaeont/ Paleontological Research, vol. 5, no. 3, pp. 143-162, September 28, 2001 © by the Palaeontological Society of Japan Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup in northern Kyushu, Japan KEIICHI HAYASHI Faculty of Science and Engineering, Konan University, Kobe, 658-8501, Japan (e-mail: Kihayasi@center.konan-u.ac.jp) Received 3 March 2000; Revised manuscript accepted 6 November 2000 Abstract. Nonmarine ostracodes from the Lower Cretaceous Wakino Subgroup in northern Kyushu were studied biostratigraphically. Analysis of abundant fossil ostracodes has led to rec- ognition of 11 assemblages and subassemblages. Vertical changes of these assemblages have made possible biostratigraphical zonation by ostracodes as follows: the Darwinula a. z. (assem- blage zone), the transitional a. z. and the large Cypridacean a. z. in ascending order. Using this zonation, the formations of the Wakino Subgroup in the eastern area are correlated with those in the western type area. Key words: Biostratigraphy, Lower Cretaceous, Northern Kyushu, ostracodes, southwest Japan, Wakino Subgroup Introduction The correlation of Lower Cretaceous nonmarine sedi- ments is controversial in Eastern Asia, because their rela- tions with marine sediments are known only in restricted regions (Matsukawa and Obata, 1992, 1994). The same is true in Japan. Molluscan fossils have been traditionally used in the correlation of Cretaceous strata of Japan by many investigators (Kobayashi and Suzuki, 1936; Ota, 1960; Hase, 1960; etc.). This approach is not reliable due to the fact that the same molluscan assemblages and characteris- tic species occur in several different horizons showing simi- lar depositional environments (Matsukawa and Ito, 1995). Thus, other methods have recently been introduced for the correlation of Cretaceous nonmarine sediments; for exam- ples by using other fossil groups such as fish (Yabumoto, 1994) and sedimentary facies suites (Sakai et al., 1992; Seo et al., 1992, 1994). One potential approach is to use the ostracode fossils that are abundantly found in Early Cretaceous nonmarine sediments. Cao (1996) described fossil ostracodes from the Cretaceous in Japan and com- pared them with those in China. However, her correlation is still insufficient because she discussed faunal assem- blages based on the samples from restricted localities. For estimating the stratigraphical significance of each species and genus, a more detailed study of ostracode biostratigraphy is necessary. Recently, Hayashi (1998) re- ported 74 ostracode species belonging to 17 or more genera from Cretaceous nonmarine sediments. This study aims to establish a biozonation by using fossil ostracodes from the Lower Cretaceous Wakino Subgroup in North Kyushu and to propose a correlation scheme. Geologic settings Geologic settings of the study area were already reported in Hayashi (1998). Only the outlines of the geology are de- scribed here to the extent necessary for later description and discussion in this paper. Early Cretaceous nonmarine sedi- ments are scattered in the Inner Zone of Southwest Japan. Especially in northern Kyushu and western Chugoku situ- ated in the western areas of the Zone, they are assigned as the Kanmon Group (Matsumoto, 1951). The group is com- posed of the Wakino Subgroup in the lower part and the Shimonoseki Subgroup in the upper part. The Shimonoseki Subgroup overlies disconformably the Wakino Subgroup and oversteps the older basement in places. In northern Kyushu, the group is distributed in two major areas (Figure 1). To the west of Nakama and Nogata cities, the upper part is generally observed sequecially from south to north, though it is discontinuously crop out into several isolated areas by some folding and faulting; to the east of Nakama and Nogata cities, obscure upper sequences are seen from south to north, but it is divided into many isolated blocks by much folding and faulting; hence the stratigraphic positioning of these delimited exposures is difficult. Among many areas occupied by the Wakino Subgroup in Figure 1, three areas, |. e. Wakino, Yurino and southern Kokura areas, were selected for this study, because ostracode fossils have been known to occur only in these areas. As the Wakino and Yurino areas are relatively close to each other, those two are described together. 144 Keiichi Hayashi Shimonosekio VA \ ZA S / ÈS RAS Kd] - | 3 „| Intrusive rocks E Shimonoseki Subgroup Wakino Subgroup Sangun Metamorphic rocks Figure 1. Geological map showing the distribution of the Kanmon Group in northern Kyushu (modified from Seo et al., 1992). A: Wakino area, B: Yurino area, C: southern Kokura area. Fa Wakino area Yurino area Kobayashi & |. Ota Ota (1953) Hase (1958, Ota Ota (1955, Ota et al (1936) 1960) (1960) 1957, 1960) (1979) Upper Upper Wakamiya Fm. | Wakamiya Fm. Uppermost Fm. Area Reference Miyata shale The Fourth Fm. Lower Lower Equivalent of the Lower insh Kinsho sandstone | wayamiya Fm. | Wakamiya Fm. Wakamiya Fm. Upper Fm. The Third Fm. Qa 3 oO 2 D) de) > WY Sengoku conglomerate Equivalent of the Nyoraida Fm. Wakino Fm. Sengoku Fm. | Sengoku Fm. ÉCMIVEIENE ae Sad Lower Fm. The First Fm. Figure 2. Comparison of stratigraphy of the Wakino Subgroup by previous studies. Nyoraida Fm. | Nyoraida Fm. Middle Fm. The Second Fm. Wakino Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup 145 Wakino-Yurino area In North Kyushu, the stratigraphical study of Mesozoic nonmarine strata was started by Kobayashi and Ota (1936) (Figure 2). They divided nonmarine strata of the Wakino area into the Wakino Formation and the unconformably overlying Sengoku conglomerate, Kinsho sandstone and Miyata shale in ascending order. Ota (1953), later, pro- posed the present stratigraphy consisting of the Sengoku, Nyoraida, Lower Wakamiya and Upper Wakamiya Formations in ascending order. This division in the Wakino area was supported by Hase (1958, 1960), and has been the standard stratigraphy of the Wakino Subgroup in north- ern Kyushu and western Chugoku. The Wakino area, the type area of the Wakino Subgroup, is situated in the southernmost part of the areas occupied by the Kanmon Group (Figure 1). Successions ranging from the Sengoku to Nyoraida Formations are observed from south to north (Figure 3). The Sengoku Formation begins with the basal conglomerate that clinounconformably over- lies the Sangun Metamorphic rocks (Figure 1). The basal facies are interpreted as a deposit dominated by debris flows by Okada et al. (1991). The middle and upper parts of the formation are made up of laminated or massive black mudstone, massive sandstone and pebble conglomerate, with intercalations of acidic tuff. They are considered to be a mixture of shallow-water, deltaic and lacustrine deposits. The Nyoraida Formation consists of rhythmic argillite inter- calated with sandstone and granule to pebble conglomerate. These sediments are tuffaceous, and many of them show graded bedding. The argillite sediments are considered to have been deposited in deep-water lacustrine environments. The coarse-grained sediments are referred to as turbidite or Nyoraida Mt. Kasagi debris flow deposits (Seo et a/.,1992). The Yurino area is situated 7 km northeast of the Wakino area. The geology of the area was mainly studied by Hase (1958, 1960). He considered that the equivalents of the Sengoku, Nyoraida and Lower Wakamiya Formations are distributed northeastward. These formations were as- signed to W1, W2 and Ws formations respectively by Ota (1960). The lowermost strata in the Yurino area are, how- ever, regarded as the Nyoraida Formation by Hayashi (1998). An upper sequence which is not found in the Wakino area is distributed in the Yurino area (Figure 4). The Lower Wakamiya Formation is composed of laminated or massive black mudstone intercalated with poorly sorted reddish sandstone and conglomerate. The Lower and Upper Wakamiya Formations are lithologically somewhat similar to each other. The former is, however, more fre- quently intercalated with discontinuous layers of pebble con- glomerate. The Lower Wakamiya Formation shows various sedimentary structures and yields fossils indicative of very shallow water and desicated terrestriai environments at some horizons. The occurrence of estherids indicates that the formation was deposited in very shallow water (Kusumi, 1979). The Upper Wakamiya Formation is composed of laminated or massive black mudstone intercalated with acidic tuff, sandstone and conglomerate. The formation shows various sedimentary structures and contains fossils indicative of shallow-water environments. The abundance of ostracodes indicates that the formation was deposited in a shallow-water environment. Southern Kokura area Previous stratigraphical studies in this area were reviewed =: N —, Wakino 7 <= ! 9 Intrusive rocks N 2?) = = Nyoraida Formation Figure 3. Geological sketch map and sampling localities of the Wakino Subgroup in the Wakino area (after Hayashi, 1998). 146 Keiichi Hayashi Tsuruta ANZ 5 Intrusive rocks NS \ I===J Upper Wakamiya eS Formation Lower Wakamiya Formation N 520 0 1km Figure 4. Geological sketch map and sampling localities of the Wakino Subgroup in the Yurino area (after Hayashi, 1998). by Hayashi (1998). Ota (1955) revealed that the Wakino Subgroup of the southernmost area.(Dobaru district) is com- posed of Lower, Middle and Upper formations in ascending order (Figure 2). Ota (1957) later added the Uppermost Formation to these three formations based on studies in the northern areas. Ota (1960) correlated these formations with the formations of other areas in the northern Kyushu and western Chugoku regions, and named them W1, W2, W3 and Wa formations. This division in the southern Kokura area was supported by Hase (1958, 1960), though he called them the equivalents of the Sengoku, Nyoraida, Lower Wakamiya and Upper Wakamiya formations, respec- tively. On the other hand, Ota et al. (1979) adopted the First, Second, Third and Fourth formations as the names of these formations, according to Matsushita (1968). This idiosyncratic nomenclature is presumably due to difficulties in lithological correlation over a wide area. The main rea- son for such variability of the stratigraphical units is that the lithology of the Wakino Subgroup is changeable laterally ex- cept for that of the Nyoraida Formation. In this paper, fol- lowing Matsumoto (1962), the Wı, W2, W3 and Wa formations of Ota (1960) are adopted for the subdivisions in the southern Kokura area. The southern Kokura area is subdivided into several dis- tricts. In the southernmost part of the southern Kokura area, Dobaru district, W1 and W2 formations are distributed with a northward dip of the strata (Figures 5, 8). In other districts, however, the strata of the Wakino Subgroup are there in many faulted blocks and have suffered deformation by folding on various scales. Hence, the stratigraphical po- sition of many blocks remains undetermined, though all of them are assigned to formations by previous studies (Ota, 1955, 1957, 1960; Hase,1958; Ota et al., 1979). In this study, the stratigraphical positions of five blocks, the Dobaru, Gamo, Washimine, East Kumagai and West Kumagai blocks, are reexamined and determined by using the ostracode zonation. With respect to the geological structure, this paper follows Hayashi (1998), who adopted the interpretations of Ota (1957) and Sakai et al. (1992) (Figure 5). Method of study All the forms of ostracode fossils in this paper were al- ready described briefly by Hayashi (1998). Systematic de- scriptions and discussions on each species should be looked for there. In this paper, first, ostracodes from each locality are re- ferred to as assemblages based on dominant, subdominant, common and characteristic species and genus and on species association. However, the exact recognition of as- semblages is difficult due to the small numbers of speci- mens, and some assemblages are gathered to establish one “assemblage zone” based on the similarity of their general 147 Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup W. Kumagai block | 5451h\ | 5451d E. Kumagai block 5221b 5221a rs Mr à 5452 5453 Washimine block } 4 # Localities of ostracode fossils \ Blocks studied biostratigraphically | Wakino Subgroup 0 Dobaru block 5261b 5261a 5261c - 5261d Figure 5. Geological sketch map and sampling localities of the Wakino Subgroup in the southern Kokura area (modified from Hayashi, 1998). 148 Keiichi Hayashi features. The reasoning of this method is that the fairly large variation in the ostracode faunas was presumably caused by a transportation mechanism of ostracode eggs in the Early Cretaceous which was different from that in the Recent. Krömmelbein (1962) pointed out that living non- marine ostracodes are occasionally transported a long dis- tance by birds in mud sticking to feet and feathers. With this method, an ostracode zonation has been suc- cessfully established in the Wakino Subgroup of the Wakino- Yurino area, northern Kyushu. Paleoenvironmenis of the ostracode assemblages are also discussed on the basis of other fossils and sedimentary structures. Based on the ostracode zonation, the Wakino Subgroup in several blocks of the southern Kokura area is correlated to the level of formation with the Wakino Subgroup in the Wakino-Yurino area. Analysis of fossil ostracode assemblages Occurrence Ostracodes occur in the Sengoku, Nyoraida, Lower Wakamiya and Upper Wakamiya Formations in the Wakino- Yurino area, where 11 localities lie. In the southern Kokura area, ostracodes are found at 13 localities in five blocks, each of which consists of one or two units of those W1 to W4 formations distinguished by Ota (1960). These locali- ties are shown in Figures 3-5, and their stratigraphic posi- tions are shown in Figure 8. Ostracode fossils occur almost always in mudstone or sandy mudstone. The mudstone of the Sengoku (W1) Formation, which is variable in lithology, contains poorly pre- served fossil ostracodes at many horizons. The mudstone of the Nyoraida (W2) Formation, however, scarcely yields fossil ostracodes. The scarcity is explained by the fact that the mudstone is interbedded with graded sandstone of turbidite origin. The mudstone of the Lower Wakamiya (W3) Formation, which is intercalated with poorly sorted dis- continuous sandstone layers, also yields few ostracodes in the Wakino-Yurino area, but does so abundantly in the southern Kokura area. Such a regional scarcity is presuma- bly due to the dominance of terrestrial fluvial plain environ- ments. In contrast, the mudstone of the Upper Wakamiya (W4) Formation, which is thinly well-stratified and interca- lated with sorted sandstone layers from horizon to horizon, contains abundant and varied fossil ostracodes. This may be related to widespread shallow-water environments during deposition of the formation. Ostracode assemblages Twelve ostracode assemblages have been identified in the Wakino Subgroup in the study area: five in the Wakino- Yurino area and seven in the southern Kokura area. Each of the ostracode assemblages is described below. Wakino-Yurino area One ostracode assemblage has been identified from the Sengoku Formation in the Wakino area, and five assem- blages from the Nyoraida, Lower Wakamiya and Upper Wakamiya Formations in the Yurino area (Figures 6, 8). 1. Darwinula assemblage In the Sengoku Formation of the Wakino area and the Nyoraida Formation of the Yurino area, the ostracode as- semblages at all the localities are commonly characterized by the abundant occurrence of species belonging to the genus Darwinula. This assemblage, named the Darwinula assemblage, is variable in generic composition. In the lower Sengoku and upper Nyoraida Formations, it contains the genus Damonella which is here represented by a single species, D. cf. obata. The species is especially abundant in the lower Sengoku Formation. The genus Clinocypris, comprising one or two species, is present in the assemblage at some localities. Damonella and Clinocypris are charac- teristic genera of the Darwinula assemblage, but they are not always common at all the localities. The genus Cypricercus, represented by a single species, seems to be another characteristic genus, but it is obtained from only one locality. It is noticeable that the assemblage is character- ized by the entire absence of the genus Cypridea, which is a dominant or common genus in all the other assemblages. The dominant genus Darwinula comprises different spe- cies at different localities. For example, this component is composed exclusively of D. incruva at Locs. TM1 and 5251, and D. submuricata in Loc. 5254, and D. cf. giganimpudica, D. postitruncata and D. sp.1 at Loc. 5Z275, and consists of D. cf. oblonga and other new species at Loc. 5241. The subordinate genus Clinocypris also comprises different spe- cies at different localities. Namely, it is represented by C. obliquetruncata at Loc. TM1, and C.? sp. 2 and C.? sp. 4 at Loc. 5251. Damonella cf. obatai occurs closely together in abundance, especially forming “ostracode layers” in the black mudstone at Loc. 52275. 2. Cypridea? cf. renalata subassemblage At Loc. 5Z261, where is exposed the middle part of the Lower Wakamiya Formation, only one assemblage from that formation is defined. In this paper, an assemblage which is found at only one locality is dealt with as a subassemblage (written as S.A.), because it may represent only one part of the indicated assemblage. The subassemblage is taxo- nomically monotonous with a small number of individuals. The dominant species is small-sized Cypridea? cf. renalata, which is also characteristic of the subassemblage. It makes up about 70% or more of the total ostracode speciemens of the subassemblage, in spite of sporadical occurrence. The subordinate species are Cypridea sp. 4, Mongolianella cf. zerussata longiuscula, M. aff. zerussata longiuscula and Rhinocypris? cf. jurassica, all of which are small in size and rare. 3. Mongolianella-Cypridea assemblage This assemblage is recognized in the lower and upper parts of the Upper Wakamiya Formation. At Locs. 5203D and 5203B of the Yurino area in the lower part of the Upper Wakamiya Formation, the ostracode as- semblage is characterized by many species of Mongolianella and Cypridea. Among them, Mongolianella zerussata longiuscula, M. cf. palmosa, M. sp. 1, Cypridea tera, C. (C.) cf. delnovi and C. (Cyamocypris) sp.1 possess a large-sized carapace, and are not found in the underlying formations (Figure 9). Medium-sized Cypridea such as C. kyushuensis and C. (Pseudocypridina) aff. jianchangensis Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup 149 Formation] Sengoku Fm. Nyoraida Fm. Lower Wakamiya Fm. Upper Wakamiya Fm. Species Loc.| TM1: 52275 : S254] |[s2s1 5241 | | 52261 52030: —B :5467:5247:5245 Cypricercus sp. Lycopterocypris cf. sinuolata ® Mongolianella aff. palmosa Mongolianella cf. palmosa e @ e M. zerussata longiuscula ® M. cf. zerussata longiuscula e M. aff. zerussata longiuscula ® Mongolianella sp.1 e Sinocypris cf. jinghongensis Candona praevara "Candona sp.1" PAIK ET AL. @ Damonella cf. ovata Rhinocypris ? cf. jurassica e "Rhinocypris sp.2" CAO e Cypridea (Cypridea ) cf. delnovi ® e C. (Cyamocypris ) sp.1 e C. (Pseudocypridina ) cf. globra ® C. (P. ) aff. jianchangensis e © Cypridea kyushuensis ® e Cypridea tera e © Cypridea ? cf. renalata ® "Cypridea sp.2" CAO e Cypridea sp.2 e Cypridea sp.4 e e e Mongolocypris sp.1 ® Eoparacypris cf. attenuata Eoparacypris macroselina ® Eoparacypris sp. 1 Genus indet. sp.2 Clinocypris obliquetruncata Clinocypris ? sp.2 Clinocypris ? sp.4 Darwinula contracta e e Darwinula cf. giganimpudica Darwinula incurva Darwinula cf. jonesi Darwinula cf. leguminella ® Darwinula cf. oblonga Darwinula postitruncata Darwinula submuricata Darwinula sp.1 Darwinula ? sp.2 > Cypridea ? cf. Assemblage & Subassemblage Darwinula A. Darwinula A. IR eh renalata S.A. Zonation (Assemblage Zone) Darwinula A.Z. Transitional A. Z. Large Cypridacean A. Z. @>10 @>3 e>ı ‘WS e192 eaplidA) v eaopudA) - ejjaueıoBuoyy Geen __zeneueloßuop __ ‘W'S sudA2e/edo3 Figure 6. Ostracode species, assemblages and biostratigraphical zonation in the Wakino-Yurino area. 150 Keiichi Hayashi are also common or abundant in the assemblage. Eoparacypris and Candona appear for the tirst time in this assemblage. Almost all the species of this assemblage have not been found in the underlying assemblages. Among them are “Rhinocypris sp. 2” of Cao (1996) with three very large laterally located nodules and Eoparacypris macroselina with a characteristic elongate-triangular cara- pace in lateral view. Consequently, this assemblage is quite different from the Darwinula assemblage and the Cypridea? renalata subassemblage. In the upper part of the Upper Wakamiya Formation at Loc. 5247 of the Yurino area, the ostracode assemblage is dominated by Cypridea (Pseudocypridina) globra and subdominated by Mongolocypris sp. 1. Other species, Cypridea (C.) cf. delnovi and Mongolianella cf. palmosa, are rare in occurrence; their number of specimens are less than 20% of the total number of individuals. It is almost the same as the above-mentioned assemblage in the lower part of the same formation, with little differences in species com- position. This assemblage shows a lower species diversity (A = EXi (Xi-1)/N(N-1) = 0.44) than the assemblage at Locs. 5203D (X = 0.15) and 5203B (X = 0.18). 4. Cypridea tera subassemblage In the middle part of the Upper Wakamiya Formation at Loc. 5467 of the Yurino area, a small number of fossil ostracodes occurs sporadically in mudstone. The ostracode assemblage is dominated by Cypridea tera and subdominated by Cypridea (Pseudocypridina) aff. jianchangensis. “Cypridea sp. 2” of Cao (1996) is also rarely associated in it. This species association is referred to as a subassemblage, because they come from a single locality. This subassemblage is here named after the most dominant C. tera. The subassemblage is thought to be closely related to the Mongolianella-Cypridea assemblage, because of the domi- nance of the characteristic species of the Mongolianella- Cypridea assemblage. 5. Eoparacypris subassemblage In the uppermost part of the Upper Wakamiya Formation at Loc. 5245 of the Yurino area, the ostracode assemblage is dominated by the genus Eoparacypris. This is also as- signed to a subassemblage, owing to the occurrence at a single locality. The genus Eoparacypris in this subassem- blage consists of E. cf. attenuata and E. macroselina. Other genera such as Cypridea and Darwinula are included in the assemblage, but they are less than 20% of the total number. Therefore, this assemblage is characterized by low species diversity (A = 0.41). The genus Eoparacypris is found only in the Mongolianella-Cypridea assemblage other than in this subassemblage. The subordinate species are Cypridea kyushuensis and Darwinula contracta, the former is also in- cluded in the Mongolianella-Cypridea assemblage at both Locs. 5203D and 52038, and the latter in the same assem- blage at Loc. 5203B. Therefore, the Eoparacypris subassemblage shows a close affinity to the Mongolianella- Cypridea assemblage. Southern Kokura area Seven ostracode assemblages have been identified in the Wakino Subgroup in five blocks of the southern Kokura area (Figures 7, 8). One assemblage was identified in each of the Dobaru.and Gamo blocks, and the Washimine and East Kumagai blocks together. Four other assemblages were identified from the West Kumagai block. They are de- scribed as follows. 6. Cypridea-Darwinula assemblage Dark gray sandy mudstone overlying unconformably the Sangun Metamorphic Rocks at Locs. 5261d, 5261c, 5261a and 5261b in the Dobaru block of the southern Kokura area is undoubtedly assigned to the W1 formation. These locali- ties are situated closely together within a stratigraphical in- terval of only 5.3 m. As shown in Figure 7, the ostracode assemblages from this mudstone appear to be different in species composition at different horizons. This, however, is due to differences in individual numbers at respective locali- ties; relatively large numbers of individuals and species were collected from Locs. 5261c and 5261b, relatively small num- bers from Locs. 5261d and 5261a. Consequently, the ostracode assemblage is better represented at Locs. 5261c and 5261b. In spite of these differences, Cypridea? sp. 3 is common among samples from the four localitlies. Therefore, the species from these four localities are consid- ered to form together a single assemblage. This assemblage is characterized by species of the gen- era Cypridea and Darwinula with six and three species, re- spectively. Clinocypris is a common genus in the assemblage, with one certain and three uncertain species. The genus Mongolianella is also common in the assem- blage. All the six species of Cypridea, except for C. (C.) cf. tuberculorostrata, are confined to this assemblage. These are interpreted to be older forms of Cypridea than those in the Wakino-Yurino area. Thus, they are probably contem- porary with the Darwinula assemblage. The occurrence of the subgenus Cypridea (Cyamocypris) should be noted, be- cause according to Cao (1996), the species of the subgenus lived in very limited environments in China. A few individu- als of C. (C.) cf. oblonga, however, were obtained here. This scarcity may imply that this locality was in relatively open environments. As to the genus Darwinula, relatively large forms such as D. cf. leguminella are dominant, but any species is not stratigraphically significant. They are significant, however, as indices of paleoclimate (Ye, 1994). Damonella cf. ovata, one of the characteristic species of the Darwinula assemblage in the Wakino-Yurino area, is included in this assemblage. 7. Cypridea tera subassemblage The ostracode assemblage from Loc. 5455 in the Gamo block is characterized by the abundance of Cypridea tera, accompanied by Cypridea (Pseudocypridina) aff. jianchangensis and C. cf. anhuaensis. Itis almost the same as that from the Upper Wakamiya Formation at Loc. 5467 of the Wakino-Yurino area. The subassemblage has a relation to the Mongolianella- Cypridea assemblage, because two of the three dominant and subordinate species are also found commonly in the Mongolianella-Cypridea assemblage. Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup Block of Southern Kokura area Gamo Formation Species Loc.|s261di—ci—aib | | 5453| 5452 e ee Cyprinotus toutaiensis e e ® & Eucypris ? sp.1 Lycopterocypris cf. sinuolata Mongolianella zerussata longiuscula M. cf. zerussata longiuscula M. aff. zerussata longiuscula Mongolianella aff. palmosa Mongolianella cf. palmosa Mongolianella ? sp.2 Mongolianella ? sp.3 Mantelliana jingguensis Mantelliana ? sp.1 Sinocypris cf. jinghongensis Candona praevara "Candona sp. 4" PAIKET AL. Cyclocypris ? cf. valida Cyclocypris ? sp. 1 Damonella cf. ovata Rhinocypris cf. tuberculata "Rhinocypris cf. jurassica j. " CAO Rhinocypris ? cf. jurassica Rhinocypris ? aff. jurassica "Rhinocypris sp.1" CAO "Rhinocypris sp.2" CAO Cypridea (C. ) cf. actuosa Cypridea (C.) cf. tuberculorostrata Cypridea (C. ) aff. delnovi "Cypridea (C.) sp.4" PAIK ET AL. Cypridea (Cyamocypris ) cf. oblonga C. (Pseudocypridena ) jinjuria C. (P.) jianchangensis C. (P. ) aff. jianchangensis Cypridea cf. anhuaensis Cypridea kyushuensis Cypridea tera Cypridea: ? sp.1 Cypridea ? sp.3 Cypridea sp.5 Clinocypris sp.1 Clinocypris ? sp.2 Clinocypris ? sp.3 Clinocypris ? sp.4 Darwinula contracta Darwinula incurva Darwinula cf. junesi Darwinula cf. leguminella Darwinula cf. submuricata Darwinula cf. sarytirmensis Darwinula aff. subparallela r g i O SL LE 3 a | SE à Darwinula - ler RS lo ilo Cypridea - > Mongolianella - Ss CS I Assembl sembla : 3 SS ls el oe Darwinula A. ® Rhinocypris ?-Candona | à 2 2 ZF N A à Du is - n a Cha PAPERS > BANN DR ; ] > Figure 7. Ostracode species and assemblages in five blocks in the southern Kokura area. The formations in Gamo, Washimine, East Kumagai and West Kumagai blocks are respectively inferred from their ostracode assemblages. 152 Keiichi Hayashi Southern Kokura area N NV 5451h Yurino area W5451d we W. Kumagai 4 ©5451b AE _\5451a S u E. Kumagai Ex s221b Ê Na > Washimine + 5452 5 5467 #5453 CE 45455 2; A5203B Gamo Wa A5203D Wakino area W5261b 3752261 Dobaru su W5261a Lower Wakamiya Nyoraida Fm. E [15254 < 052275 oO) =: © peed DM SAL unconformity 2 Qa © = Co WwW c œ =) 2 D LL fault == axis of folding | strata with poo Figure 8. Stratigraphical distribution of ostracode assemblages. The relationships between assemblages and biostratigraphical zones are shown in Figure 6. Ostracode Assemblages and Subassemblages © Eoparacypris S.A. Mongolianella-Cypridea A. Cypridea tera S.A. Rhinocypris S.A. Mongolianella S.A. Nodular Cypridea S.A. Large Cypridea S.A. Cypridea? cf. renalata S.A. Darwinula-Mongolianella- Rhinocypris?-Candona A. Darwinula A. Cypridea-Darwinula A. EU FY 604 RE rly preserved ostracode fossil Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup 153 8. Darwinula-Mongolianella-Rhinocypris?-Candona as- semblage From Locs. 5221a and 5221b in the East Kumagai block, the former located 7m below the latter, a high-diversity (A = 0.11-0.24 ) ostracode assemblage was obtained. The as- semblage involves 19 species belonging to 11 genera. The faunal composition is the most complex among all the as- semblages described in this paper. The sample size for the two dominant species, Darwinula aff. subparallela and Rhinocypris? cf. jurassica, are only slightly larger than those for several subordinate species. Therefore, it is inadequate to name the assemblage after the leading generic or species names. Among the subordinate species, four species be- long to the genus Mongolianella and two species to the genus Candona. Thus, the high-diversity assemblage is named the Darwinula-Mongolianella-Rhinocypris?-Candona assemblage. The assemblage is somewhat similar to the Cypridea- Darwinula assemblage and Darwinula assemblage in the abundance of Darwinula, and also resembles the Mongolianella-Cypridea assemblage in the abundance of Mongolianella. This may mean that the assemblage is tran- sitional from early Darwinula-dominant assemblages to later large Cypridacean-abundant assemblages. At species level, however, the components of the genus Darwinula in this assemblage are different from those of the Darwinula assemblage of the Sengoku and Nyoraida Formations and the Cypridea-Darwinula assemblage of the Dobaru block, except for D. cf. /eguminella with a long stratigraphical range extending throughout the Wakino Subgroup. Two ofthe three species of the genus Cypridea are held in common the Cypridea-Darwinula assemblage in the Upper Wakamiya Formation in the Yurino area, and the remaining one is common with the assemblage of the Dobaru block. The assemblages at Locs. 5453 and 5452, the former 10 m below the latter are also identified with the Darwinula- Mongolianella-Rhinocypris?-Candona assemblage. This identification is based on the abundance of Darwinula and Mongolianella, and on the fact that four of the seven species comprising the assemblage also occur in the high-diversity assemblage of the East Kumagai block. In particular, three of the four species characteristically occur in the East Kumagai block. 9. Large Cypridea subassemblage At Loc. 5451a of the West Kumagai block, a very large Cypridea, C. sp.5, occurs exclusively. This species is the biggest in all the ostracodes of the Wakino Subgroup. Other species are few and cannot be identified to species because of poor preservation. This unique assemblage seems to have settled in a limited environment on ash-field bottoms. This ostracode association is assigned to a subassemblage owing to its restriction to the limited occur- rence at a single locality. 10. Nodular Cypridea subassemblage The characteristic Cypridea with nodulated surface, “C. sp. 4” of Paik et al. (1988), occurs dominantly at Loc. 5451b, which is about 3.8 m above Loc. 5451a within the same West Kumagai block. Such a nodulate species is very rare in the Wakino Subgroup, though another nodulate species is present in the Rhinocypris subassemblage from the same West Kumagai block and the Mongolianella-Cypridea as- semblage from the Upper Wakamiya Formation in the Yurino area. A subordinate species is large-sized Mongolianella cf. palmosa, which is characteristic of the Upper Wakamiya Formation in the Wakino-Yurino area. This association of ostracodes is also assigned to a subassemblage owing to its occurrence at a single locality. 11. Mongolianella subassemblage A quite different assemblage from that of Locs. 5451a and 5451b is found at 5451d about 1.5 m above Loc. 5451b. Because of small numbers of individuals, only one species was so far found at this locality. This exclusive species is Mongolianella zerussata longiuscula, which is, in contrast, coexistent with many other species at Loc. 5203B. This ostracode association is also assigned to a subassemblage owing to its appearing at a single locality. 12. Rhinocypris subassemblage This assemblage is found at Loc. 5451h, which is located 3.4 m above Loc. 5451d, and shows the highest diversity (A = 0.21) among the four localities within the West Kumagai block. It is named because of the abundance of Rhinocypris. The genus Rhinocypris of this subassemblage consists of five species, R. cf. tuberculata, R.? cf. jurassica, “R. cf. jurassica jurassica”, “R. sp.1” and “R. sp.2”, among which the last three were described by Cao (1996). Of the three species, “Rhinocypris sp. 2” of Cao (1996) is common to the Mongolianella-Cypridea assemblage from the Upper Wakamiya Formation in the Yurino area. Cypridea (C.) aff. delnovi is also abundant in the subassemblage. Ostracode assemblages and sedimentary environments Characteristics of Early Cretaceous ostracode assem- blages.— Generally, the diversity of nonmarine ostracode assemblages from the Wakino Subgroup is extremely high as compared to those of Recent or Cenozoic ones. This high diversity is most remarkable in the Lower Cretaceous ostracode assemblages all over the world. However, the reasons behind this high diversity have not been sufficiently discussed until now, in spite of the importance for assessments of ostracode assemblages. Some living ostracode assemblages from isolated lakes around the world are remarkably similar to one another. This owes much to transport by migratory water birds, either in mud sticking to their feet and trapped in feathers or in the intestinal tract (Krommelbein, 1962, Brasier, 1980). Since most nonmarine ostracode eggs are very resistant against desiccation, their dispersion could be largely accomplished by water birds. However, such Early Cretaceous migratory water birds are unknown (Figure 10). The oldest evidence of water birds in East Asia is the footprints of webbed feet from the Upper Cretaceous Uhangri Formation of Korea (Yang et al., 1995; Figure 10). The age of the formation is younger than 85-92 Ma (radiometric age of the Hwangsan Tuff in the underlying formation) and older than 63-67 Ma (radiometric age of the Haennam basin intrusives in the overlying formation). On the other hand, shore birds had already become habi- Keiichi Hayashi 154 Cypridea tera a ouo7 obejqwassy uesseplidA) 261e7 dno1qns oureM "Ww eAıweyem 1oddn = "Candona sp.1" Paik et al. jeuonisueu] Cypridea (Pseudocypridina) jinjuira Dana 2 anne EYE M 19M07 Darwinula cf. oblonga Genus THe cD eplesoAN Damonella cf. ovata (ueder ‘nysnAy uisyyiou ‘sn09983919 19M07) Darwinula cf. leguminella a A Cypridea (C.) cf. actuosa eg 7 ‘V ejnuimieg ö H d 5 A H 5 A ö H A d A 7 ö 5 A ö d C. (Pseudocypridina) jianchangensis ‘Wu nyobuas Clinocypris obliquetruncata a Imm Mongolianella cf. z. longiusucula To sp.1 er] Wakino-Yurino Area (Type Area) : Southern Kokura Area Figure 9. Some of the representative ostracodes from the Wakino Subgroup are arranged at their stratigraphical and geographical positions. Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup 155 N. Kyushu Hida = Haennam basin intrusives Uhangrichnus chuni : Duck-like bird with webbed feet Hwangsanipes choughi : Flamingo-like bird with webbed feet 85-92Ma Ivy | Hwangsan Tuff Alben Jindongornipes kimi : Largest bird footprint in Cretaceous Aptian (Choi, 1985) Koreanaornis hamanensis : a similar species is found in the Early Cretaceous sediments of China (Zhang et al., 1987; Lockley et al., 1992). This is referred to footprints of plovers that is one of Haman Fm. NE Shilla Cg. Fm. Chilgok Fm. Sindong G. the Recent migrant water birds. Akaiwa Subg. Aquatilavipes sp. Do Bo) > n Itoshiro Figure 10. Occurrence of Cretaceous water and shore birds in Korea and Japan. tants of lacustrine shorelines in East Asia by Early Cretaceous. For example, Kim (1969) reported avian tracks associated with many invertebrate trace fossils from the Haman Formation of the Lower Cretaceous Hayang Group of the Kyeongsang Supergroup in Korea. More rencently Choi (1985) has suggested that these deposits are probably Aptian to early Albian in age. Yang et al. (1990) and Lockley et al. (1991) discovered many avian tracks at 31 localities in the Jindong Formation that overlies the Haman Formation. They concluded that there appear to be at least two quite distinct footprint types, Jindongornipes kimi and Koreanaornis hamanensis in the Jindong Formation. Koreanaornis hamanensis resembles the footprint of various modern species of plovers. Recent plovers are migratory shore birds, one of which is known to migrate several thou- sand kilometers. Matsukawa (1991) reported bird tracks from the Valanginian-Hauterivian? Izuki Formation (upper part of the Itoshiro Subgroup of the Tetori Group) in central Japan, which is slightly older than or almost contemporane- ous with the Wakino Subgroup. Considering that aviform tracks are widespread and a sig- nificant component of Early Jurasssic ichnological assem- blages, birds presumably evolved rapidly in the Late Jurassic and Early Cretaceous (Lockley et a/.,1992). The shore bird radiation may have occurred in Early Cretaceous, but this apparently did not yet produce fully aquatic birds. Given this, it may be surmised that only shore birds were ac- tive on the shore of the sedimentary basin of the Early Cretaceous Wakino Subgroup. Consequently, the ostracodes whose eggs could then be transported by birds were restricted to shoreline-inhabiting species. It is consid- ered that species living in water deeper than 10 cm or so 156 were seldom transported by birds. Therefore, many spe- cies presumably evolved in situ in each lake, giving rise to high-diversity assemblages. The similarity of contempora- neous ostracode assemblages within the same lakes may have been maintained. The similarity, however, was not warranted in assemblages of isolated lakes long distances aprt in the Early Cretaceous. Namely, it is suspected that the ostracode assemblages were different from lake to lake. As Lower Cretaceous ostracode assemblages were changeable from place to place, ostracode biostratigraphical zonation and correlation should not be based directly on ostracode assemblages of a certain kind, but on more gen- eral features common among closely related assemblages. Sedimentary environments indicated by fossil charophytes and estherids.—At some horizons of the Wakino Subgroup, fossil charophytes are found abundantly together with ostracode fossils. Fossil estherids occur accompanying ostracode fossils at many horizons. These charophyte and estherid fossils are useful to assess sedimentary environ- ments. Ecological discussions of these taxa have been little done, in spite of their importance ‘for indications of paleoenvironments. Then, it should be discussed what kind Keiichi Hayashi of environments these taxa indicate. Sedimentary environments indicated by fossil charophy- tes: Fossil charophytes occur abundantly in the Sengoku Formation at Loc. TM1 of the Wakino area and the Upper Wakamiya Formation at Loc. 5247 of the Yurino area. According to the classification generally accepted, charophytes consist of 3 orders and 6 families including fos- sil species. But of the three only one order (Charales) with four families survives today, of which only one family (Characeae) has living species. About 250 living species are known from all over the world, of which about 70 species are living in Japan. This group appeared in the Silurian, and became highly di- versified by the Cretaceous but declined to the Recent. The ecology of recent charophytes is very significant, because it forms “Chara zone” in the lowermost part of the depth distri- bution of aquatic plants in lakes (Kazaki, 1967; Figure 11). The depth of the lower limit of the “Chara zone? is inferred to be about twice the average depth of transparency in sum- mer, based on the data shown in Figure 11. The upper limit of the “Chara zone” is determined by the depth of the overly- ing “zone of Submerged Plants”, which ranges from one to Spermatophyta Algae | Marsh io ete Er — nn LL Li Om i : = 19 IL > 5 | VA QI Zone of emergent plants 1, i Zone of floating-leaved plants 4 \ 1-3m 4 Zone of submerged plants t "Chara Zone" 7 5-30m ' 0 | 1 ! | \ Average depth of transparency |"Chara Zone" in summer (m) (m) v 14 Twice of the average depth of transparency in summer 11 7.5 Kawaguchiko Yunoko Figure 11. Kazaki, 1967). aquiherbosa, that is, a shallow bottom covered by aquatic plants. form the “Chara zone”. (After Kazaki, 1967) Schematic diagram showing vertical zonation of aquatic large plants in lake shore environments (partly adopted from Compiled from many ecological studies of recent freshwater botany. Vertical zonation is generally formed in the The lowermost part is exclusively abundant in charophytes, which Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup 157 several meters. Consequently, the Recent “Chara zone” is usually formed on the shallow bottom that is deeper than several meters and shallower than 30 m. Inthe Cretaceous, however, the upper limit of the zone is inferred to have been shallower than that in the Recent, because plants forming zones over the “Chara zone”, most of which belong originally to terrestrial spermatophyta, invaded submerged environ- ments from terrestrial environments during or after the Cretaceous. Therefore, the “Chara zone” is considered to have been a little wider, namely, a few to 30 m. If this is true, charophytes accompanied by many other aquatic plants indicate the “zone of the submerged plants”, which is shallower than a few meters. In such shallow water, a calm environment in which plants can grow is considered to have been restricted to enclosed margins of lakes or marshes on the fluvial plain, because waves and currents usually prevent plants from growing. Large aquatic plants tend to grow in bays rather than in open-shore environments (Ikushima, 1969). Among many kinds of aquaplants, charophytes especially prefer lentic environments to litic environments, as lentic environments favor the swimming of sperm during fertilization. As discussed above, the abundant occurrence of fossil charophytes surely indicates shallow and calm water envi- ronments. Such environments can be seen in enclosed bottom parts of marginal lakes, shallow swamps or marshes on the fluvial plain. Sedimentary environments indicated by fossil estherids: |n the southern Kokura area, estherids were collected by Ota (1957) from W3 and W4 formations exposed near Yamada Park and were described as Euestheria imamurai, E. kokuraensis and Cyclestheroides sp. by Kusumi (1960). Additional estherids were collected by Ota et al. (1979) from W3 and W4 formations in the same place. Among them, those from the basal part of W4 formation were identified as Euestheria imamurai, E. kokurensis and Cyclestheroides sp. by Kusumi (1979). In the Wakino-Yurino area, estherid fos- sils have been newly found in the Lower Wakamiya Formation at Loc. 52261 of the Yurino area. They were identified as Orthestheria kokurensis (the genus Orthestheria has replaced Euestheria) by Chen (1996). According to a recent classification, estherids are formally called Conchostraca, an order of Branchiopoda (Crustacea). Six Recent species are known in Japan, and at least four of them are unique to Japan. All the species of Recent Conchostraca live in very limited environments with very shallow (about 5 to 10 cm, in maximum 20 cm) muddy bot- toms which dry up occasionally. Desiccation is indispensa- ble for eggs of Conchostraca to mature. In East Asia, at present, the drying up of lakes takes place in winter. If this was true for Cretaceous time, the Conchostraca could be useful as a indicator of paleoenvironments. Sedimentary environments of the ostracode assemblages. — The sedimentary environments of the ostracode assem- blages described above are discussed below. 1. Darwinula assemblage This assemblage generally suggests such depositional environments as marginal lacustrine bottoms or terrestrial shallow ponds on the fluvial plain. Charophytes, gastro- pods and plant fragments co-occur abundantly with ostracodes in poorly sorted sandy siltstone at Loc. TM1. As discussed above, the siltstone containing these kinds of fos- sils is considered to have been deposited in water shallower than several meters. The bottom was covered with many kinds of aquatic plants, as is easily inferred from numerous plant fossil remains. The water must have been stagnant except for episodic events of storms and floods. Such stag- nant and shallow-water environments are supposed to have been in the enclosed part of lacustrine shores shallower than a few meters, or marshes on the fluvial plain. The assemblage at Loc. 52275 must have been in envi- ronments somewhat different from those of Loc. TM1, be- cause the sediments at the former locality are made up exclusively of black sandy siltstone with ostracode-crowded layers. The lack of plant fossils suggests that the siltstone was deposited on a bottom deeper than the base of the ver- tical distribution of aquatic plants (cf. Figure 11), or in open shallow-water environments. The former is considered more probable because of the scarcity of fossils. Moreover, if the latter was the case for Loc. 5Z275, many kinds and large numbers of animals should have lived there. However, the depositional environment is not thought to have been so deep, because it was also inhabited by many individuals of the gastropod Brotiopsis wakinoensis. The genus Brotiopsis belongs to the Pleuroceridae, almost all the Recent species of which live on lake or river bottoms shal- lower than several meters. Far deeper environments are thought to have existed in the surroundings of Loc. 5254 of the Wakino area and Loc. 5251 of the Yurino area, based on analysis of sedimentary facies. Mudstone with thin silty laminae at Loc. 5254 is compared to a deposit resulting from seasonal suspension clouds, and mudstone intercalated by graded sandstone at Loc. 5251 is inferred to be of turbidite origin by Seo et al. (1992). These facies are relatively poor in ostracode and other fossils. In contrast, the depositional environments of the Nyoraida Formation at Loc. 5241 are considered to have been shal- low-water ones because of the relative abundance of ostracodes in massive mudstone, presumably bioturbated. This assemblage indicates a subtropical-tropical climate, the work of Ye (1994) having shown that the genus Darwinula was widely distributed and able to diversify in southern China, but declined to the north. 2. Cypridea? cf. renalata subassemblage This subassemblage is inferred to suggest a fluvial plain, judging from estherid fossils and sedimentary facies. Estherids live only in shallower water than 20 cm, where the bottom is occasionally emerged and dried up. Laterally changeable lithologies from clay to pebbly conglomerate and sedimentary structures such as channel structures and cross-laminations support flood plain environments. This kind of severe environments for aquatic animals al- lows ostracode life for only a short term, and so, almost all of the individuals are of small size. The scarcity of ostracodes in the Lower Wakamiya Formation is explained by such a severe environment. 3. Mongolianella-Cypridea assemblage This assemblage at Locs. 5203D and 5203B is presumed to have been on a variable widespread shallow-water bot- 158 Keiichi Hayashi tom, because many kinds of niches seem to have existed in the same water mass, as suggested by the variety of ostracodes and sediments (Matsukawa et al., 1996). This assemblage at Loc. 5247 shows a lower species di- versity (A = 0.44) than the ones at Locs. 5203D (A = 0.15 ) and 5203B (A = 0.18). Itis explained by a relatively deeper environment, which is shown by exclusively abundant charophyte fossils. Such an environment corresponds to the so-called “Chara zone”, which is the lowermost zone in the vertical distribution of aquatic plants at water depths from a few to 30 m as already discussed. 4. Cypridea tera subassemblage This subassemblage is known both in the Wakino-Yurino and the southern Kokura area. With thin parallel laminations of dark gray mudstone inter- calated with sandstone, the depositional environment for the Cypridea tera subassemblage in the Wakino-Yurino area (Loc. 5467) is inferred to have been similar to that of Locs. 5203D and 5203B: a variable widespread shallow-water bot- tom. On closer view, the environment at Loc. 5467 seems to have been somewhat antagonistic to ostracodes, as the ostracode-bearing layer is overlain by sandstone as thick as 7m. The same subassemblage is in thinly parallel-laminated mudstone intercalated with sandstone at Loc. 5455 in the Gamo block in the southern Kokura area. From the lithological similarity, the depositional environment is in- ferred to have been similar to that of Locs. 5203D , 5203B and 5467. The environment may have been of widespread shallow-water bottom, though the environment of Loc. 5455 may have been slightly hostile to ostracode life, as sand- stone intercalations are relatively frequent. 5. Eoparacypris subassemblage The low diversity of species (A = 0.41) in this subassem- blage suggests that species of the genus Eoparacypris lived in restricted environments. Judging from the lithology with- out intercalations of sandstone, it is certain that a quiet envi- ronment persisted for a long time. According to Anderson (1985), this genus is relatively abundant in marly beds. This may suggest shallow lake environments, where the rate of evaporation was high. However, carbonate is not pre- served in any of the studied materials. 6. Cypridea-Darwinula assemblage This assemblage lived in a shallow and enclosed part of the marginal lacustrine environment, because massive sandy mudstone shows repeated bioturbations and sporadi- cally contains granules of secondarily formed iron sulfate. Many kinds of animal fossils other than ostracodes, such as fish, turtles and gastropods occur in this sandy mudstone. The turtle fossils are especially indicative of near-shoreline environments. This sandy mudstone, however, contains few plant fossils, which are generally rich in enclosed parts of the marginal lacustrine environments and terrestrial marshes on the fluvial plain. According to Ye (1994), the genus Darwinula was widely distributed and evolved diversely in southern China while declining to the north in the Late Cretaceous. This means that the genus Darwinula preferred a subtropical-tropical cli- mate to temperate-cold one. The occurrence of the genus Darwinula indicates that the Cypridea-Darwinula assem- blage existed in subtropical-tropical climates, as did the Darwinula assemblage in the Wakino-Yurino area. 7. Darwinula-Mongolianella-Rhinocypris?-Candona as- semblage This highly diversified assemblage (A = 0.11-0.24) at Locs. 5221a, 5221b, 5452 and 5453 was on shallow-water bottoms, which were dried up temporally. Sedimentary structures such as channels and mudcracks and the lithology of reddish sandstone indicate fluvial depositional environments. The topset of deltas may have spread here. 8. Large Cypridea subassemblage This subassemblage must have been under the influence of intense volcanic activity, because the lithology consists mostly of white tuff. Intercalations of poorly sorted reddish sandstone exhibit shallow-water bottoms which saw occa- sional emergence. It is to be expected that only the ex- tremely large-sized species survived drastic environmental changes caused by ash fall that killed other species which lived there. 9. Nodular Cypridea subassemblage The environment for this subassemblage is inferred to resemble that of the underlying large Cypridea subassemblage from the lithology of tuffaceous mudstone at Loc. 5451a. No difference between them has been found. 10. Mongolianella Subassemblage The bottom environment of this subassemblage is similar to that of the large Cypridea subassemblage and the nodular Cypridea subassemblage, as far as the lithology is con- cerned. 11. Rhinocypris subassemblage The bottom environment for this subassemblage is pre- sumed to have been almost the same as that for the large Cypridea (Loc. 5451a), nodular Cypridea (Loc. 5451b), and Mongolianella (Loc. 5451d) assemblages in view of the simi- lar lithologies among them. Zonation and correlation Biostratigraphical zonation based on the ostracode as- semblages has been established in the Wakino-Yurino area. By using this zonation, the Wakino Subgroup in several blocks of the southern Kokura area is correlated with the for- mations in the Wakino-Yurino area. Zonation by ostracode assemblages.—Remarkable shifts in the ostracode assemblages were clearly recognized in the Wakino Subgroup in the Wakino-Yurino area (Figure 9); hence the subgroup can be divided into the following three assemblage zones toward the top of the sequence. 1. Darwinula assemblage zone All the ostracode assemblages from the Sengoku and Nyoraida formations are assigned to the Darwinula assem- blage (Figure 6). The range of the Darwinula assemblage provides a basis for a single biostratigraphical zone. This zone is called here the “Darwinula assemblage zone (in brief, a. z.)”. 2. Transitional assemblage zone The Cypridea? cf. renalata subassemblage was obtained from only one locality, as the Lower Wakamiya Formation is only sparsely fossiliferous (Figure 6). But the subassem- blage shows clearly different characteristics from both the Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup 159 ZONE Nyoraida Fm. Molluscan zone Molluscan fauna Stratigraphy (Ota, 1960) (Hase, 1960) Upper Wakamiya Fm. Viviparus onogoensis- Upper Wakino Assemblage Zone Nakamuranaia ? cf. or Wakamiya |Paraleptolepis- be Lower Wakamiya Fm. chingshanensis emule Vera Ella Transitional Assemblage Zone Brotiopsis wakinoensis Lower Wakino or |Nipponamia- Saeed ie ZONE Sengoku faunule |Aokiichthys fauna Fish fauna (Yabumoto, 1994) Diplomystus- Wakinoichthys fauna Ostracode assemblage zone (this paper) Large Cypridacean Darwinula Assemblage Zone Figure 12. Comparison among biostratigraphical zonations by various kinds of faunas. underlying and overlying assemblages. This poorly desig- nated subassemblage is regarded as a “transitional” assem- blage from the underlying Darwinula assemblage to the overlying cypridacean-dominant assemblages, and defines the “transitional assemblage zone (a. z.)”. 3. Large Cypridacean assemblage zone Three different ostracode assemblages were recognized in the Upper Wakamiya Formation, though other formations of the Wakino Subgroup each contain a single assemblage (Figure 6). One of the three assemblages, the Mongolianella-Cypridea assemblage, represents a recur- rence within the formation. Two of the three assemblages, the Cypridea tera subassemblage and the Eoparacypris subassemblage are observed at a single locality. The dif- ferences among these three subassemblages seem to be determined by environmental differences. Consequently, it is practical to adopt the general characteristics and names of higher taxa. Hence, the Upper Wakamiya Formation is biostratigraphically named the “Large Cypridacean assem- blage zone” after large forms of Cypridea, Mongolianella and Candona, all of which belong to the superfamily Cypridacoidea. This ostracode biostratigraphical zonation is compared with the other biostratigraphical zonations previously pro- posed on the basis of defferent kinds of fossils (Figure 12). The Nyoraida Formation, which has been biostratigraphically considered to be barren by Hase (1960) and Yabumoto (1994) and assigned to the lower part of the molluscan Viviparus onogoensis-Nakamuranaia? cf. chingshanensis zone by Ota (1960) (originally, he described it as the Viviparus onogoensis-Nakamuranaia? sp. cf. N. chingshanensis zone), was assigned to the upper part of the Darwinula assemblage zone in the ostracode zonation. The Lower Wakamiya and Upper Wakamiya Formations can be distinguished from each other by the ostracode zonation inthe same ways as the fish zonation by Yabumoto (1994), though they cannot be discriminated by the molluscan zonation (Ota, 1960; Hase, 1960). Correlation of formations in the southern Kokura area.—In the southern Kokura area, the Wakino Subgroup is divided into many blocks by faults. Owing to such complicated geo- logical structures, it is difficult to determine the exact Stratigraphical positions of the exposure at each block. Therefore, the same block has been regarded as different formations by previous studies. 1. Dobaru block The strata which have been assigned to the W1 formation (Ota, 1955, 1960; Hase, 1958) and contain the Cypridea- Darwinula assemblage in the Dobaru block were correlated with the Sengoku or Nyoraida Formation of the Wakino- Yurino area by ostracode biostratigraphy, because the Cypridea-Darwinula assemblage from the lower stratigraphi- cal part in the Dobaru block is similar to the Darwinula as- semblage from the Sengoku and Nyoraida Formations in the Wakino-Yurino area in the abundance of Darwinula. However, there is a great difference in the abundance of the genus Cypridea. This is probably owing to the rareness of plants covering the bottom, as described above in this sec- tion. No species of Cypridea in the Cypridea-Darwinula as- semblage is in common with those of the five assemblages and subassemblages in the Lower Wakamiya and Upper Wakamiya Formations ofthe Wakino-Yurino area. This fact also supports the above correlation. During the early depositional stage of the Wakino Subgroup, in which Darwinula was dominant, the deeper and stagnant nearshore water environments probably allowed ancestral species of Cypridea to live. Damonella cf. ovata, known only from the Darwinula a. z. and occurring in both the Cypridea-Darwinula assemblage and the Darwinula assem- blage, also strengthens the correlation. 2. Gamo blocks The sediments in the Gamo block were correlated with the Upper Wakamiya Formation in the Wakino-Yurino area, be- cause they contain the same Cypridea tera subassemblage belonging to the Large Cypridacean assemblage zone in the Wakino-Yurino area. The block has been assigned to the W4 formation in the previous studies (Ota, 1957, 1960; Hase, 1958; Ota et al. 1979). The ostracode zonation leads to the same conclu- sion. 3. East Kumagai and Washimine blocks The East Kumagai block has been regarded as distribut- ing the W3 formation by Ota (1957, 1960) and Hase (1958). Recently, however, Sakai et al. (1992) considered it to be “Unit B” of their subdivisions of the Wakino Subgroup in Yamada Park of Kokura. On the other hand, the strata in 160 Keiichi Hayashi the Washimine block have been assigned to different forma- tions by different authors; for example, to the W3 formation by Ota (1957, 1960), equivalent of the Nyoraida (W2) Formation by Hase (1958), and “Unit A” by Sakai et al. (1992). Both the Lower Cretaceous strata in the East Kumagai and Washimine blocks yield the same high-diversity (5453: À = 0.12, 5221a, 5221b: A = 0.11, 0.12) ostracode assem- blage. The Darwinula-Mongolianella-Rhinocypris?-Candona a. z. shows some relations to the Mongolianella-Cypridea assemblage that belongs to the large Cypridacean a. z. in the Wakino-Yurino area, because it contains Cypridea kyüshuensis, which is one of the characteristic species of the Mongolianella-Cypridea assemblage. Such relations are also shown by the abundance of Mongolianella. On the other hand, the abundance of Darwinula suggests subtropical-tropical climates. Lycopterocypris cf. sinuolata from the East Kumagai block is common with the Cypridea- Darwinula assemblage of W1 formation in the Dobaru block. Rhinocypris? cf. jurassica from the East Kumagai block is found only in the transitional a. z. in the Wakino-Yurino area. In the southern Kokura area, however, this species survived until the depositional time of the West Kumagai block, which may be assigned to the large Cypridacean a. z. as dis- cussed below. In summary, the strata bearing the Darwinula- Mongolianella-Rhinocypris?-Candona a. z. in the East Kumagai and Washimine blocks are correlated with the tran- sitional a. z. in the Wakino-Yurino area, namely, with the Lower Wakamiya Formation. 4. West Kumagai block The West Kumagai block has been considered to be occu- pied by the W3 formation (equivalent to the Lower Wakamiya Formation) by Ota (1957, 1960) and Hase (1958), though Ota et al. (1979) regarded the strata in the block as the W4 formation (the Fourth Formation). Recently, Sakai et al. (1992) assigned it to “Unit B”, which overlies “Unit A”. The block contains four ostracode subassemblages: the large Cypridea, nodular Cypridea, Mongolianella and Rhinocypris ones in ascending order. These four assem- blages have common characteristics with one another; all of them contain large-sized species or nodulate species of the superfamily Cypridoidea. They are Cypridea sp. 5, Mongolianella cf. palmosa, M. zerussata longiuscula, “Cypridea (C.) sp. 4” of Paik et al. (1988), Rhinocypris cf. tuberculata and “Rinocypris sp. 1” and “R. sp. 2” of Cao (1996). These characteristics lend themselves to the corre- lation with the large Cypridacean assemblage zone in the Wakino-Yurino area. Therefore, the strata in the West Kumagai block were correlated with the Upper Wakamiya Formation. 5. Stratigraphy and geological structure of the Wakino Subgroup In conclusion, the ostracode biostratigraphy revealed that the staratigraphy and geological structures in the southeren Kokura area are as follows. The formations previously called the W1, W2, W3 and W4 formations are formally called here the Sengoku, Nyoraida, Lower Wakamiya and Upper Wakamiya Formations, respec- tively, because the ostracode biostratigraphical zonation that has been established in the type areas is well discernible in the southern Kokura area. The Sengoku Formation in this area consists of more fine- grained sediments, and secondarily formed iron in them shows a more reducing environment than in the Wakino area. The Lower Wakamiya Formation in this area was de- posited in widespread shallow water and rarely dried-up en- vironments, because it yields much abundant in the way of ostracode fossils than in the Yurino area. In contrast to the Sengoku and Lower Wakamiya Formations, the Nyoraida and Upper Wakamiya Formations in this area do not seem to be different from the Wakino-Yurino area. In the Dobaru district, the Wakino Subgroup begins with the Sengoku Formation, which clino-unconformably overlies the Paleozoic strata. The Sengoku and the overlying Nyoraida Formations are distributed with a northward dip- ping structure, and are faulted to bound on the basement rocks or intrusive rocks. t In the northern part of the area, the Lower Wakamiya and Upper Wakamiya Formations are distributed in a principal anticline. Specifically, the Upper Wakamiya Formation is distributed in the southern Gamo block and the northern West Kumagai block, and the Lower Wakamiya Formation is in the Washimine and East Kumagai blocks, both of which are situated in an axial part of the anticline. In detail, how- ever, many small faults and foldings are involved in places in this area. Conclusions As the first biostratigraphical study on Mesozoic nonmarine ostracodes in Japan, 11 assemblages have been established, and the zonation based on these assemblages has been proposed. Major results of these investigations are Summarized as follows: 1) From the Wakino Subgroup in the Wakino-Yurino area, five assemblages and subassemblages were recognized: the Darwinula assemblage from the Sengoku and Nyoraida Formations, the Cypridea? cf. renalata subassemblage from the Lower Wakamiya Formation, and the Mongolianella- Cypridea assemblage, the Cypridea tera subassemblage and the Eoparacypris subassemblage from the Upper Wakamiya Formation. 2) Based on stratigraphical changes in general features of these assemblages, stratigraphical zonation by ostracodes was proposed as the Darwinula a. z. (assemblage zone), transitional a. z. and large Cypridacean a. z. in ascending order. This method of zonation is reasoned by vertical changes of the ostracode assemblages. These assem- blages were easily recognized because of their characteris- tic species composition. This probably is due to the absence of water birds as main transporters of ostracode eggs, though ostracode eggs of shoreline-inhabiting species could have been transported by shore birds. 3) In the southern Kokura area, seven ostracode assem- blages and subassemblages were recognized in the Wakino Subgroup in five blocks: the Cypridea-Darwinula assem- blage from the W1 formation in the Dobaru block, the Cypridea tera s. a. in the Gamo block that has been as- signed to the W4 formation, the Darwinula-Mongolianella- Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup Rhinocypris?-Candona assemblage in the Washimine and East Kumagai blocks, the large Cypridea, nodular Cypridea, Mongolianella and Rhinocypris subassemblages from the West Kumagai block. With regard to the stratigraphical zonation proposed in the Wakino-Yurino area, each of the blocks was correlated as follows: the strata in the Gamo block certainly belong to the large Cypridacean a. z., those in the Washimine and East Kumagai blocks are probably as- signed to the transitional a. z., and the West Kumagai block is surely attributed to the large Cypridacean a. z. Acknowledgements This paper was based on work for a doctoral thesis awarded by Kyushu University. The author expresses his sincere appreciation to H. Okada, T. Hanai, N. Ikeya, A. Matsukuma, for their helpful suggestions and critical reading of the manuscript. The author is particularly grateful to M. Matsukawa for his encouragement and support during the laboratory and field work. M. Ota and Y. Yabumoto, and M. Tamura helped the author with sampling and offering ostracodes in northern Kyushu. Acknowledgements are also due to O. Takahashi for his great assistance in photog- raphy by using SEM. 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G., Sakai, T. and Okada, H., 1992: Occurrence and origin of rhythmites, in Lower Cretaceous lacustrine sedi- ments in the Wakino Subgroup, Kyushu. Science Reports, Department of Earth and Planetary Science, Kyushu University, vol. 17, p. 45-54. (in Japanese) Seo, S. G., Sakai, T. and Okada, H., 1994: Depositional envi- ronments of the Wakino Subgroup of the lower Cretaceous Kanmon Group in the Kitakyushu area, Japan. Memoirs of the Faculty of Science, Kyushu University, series D, vol. 18, p. 41-60. Yabumoto, Y., 1994: Early Cretaceous freshwater fish fauna in Kyushu, Japan. Bulletin of the Kitakyushu Museum of Natural History, no. 13, p. 107-254. Yang, S. Y., Lockley, M. G., Greben, R., Erickson B. R. and Lim, S. K.,1995: Flamingo and duck-like bird tracks from the Late Cretaceous and Early Tertiary: evidence and im- plications. /chnos, vol. 4, p. 21-34. Yang, S. Y., Lim, S. K., Lockley, M. G., and Fleming, R. F.,1990: On Cretaceous bird tracks from the Jindong Formation, Gyeongsong Group, Korea. Journal of the Geological Society of Korea, vol. 20, p. 580. Ye, C. H.,1994: Succession of Cypridacea (Ostracoda) and nonmarine Cretaceous stratigraphy of China. Cretaceous Research, vol. 15, p. 285-303. Paleontological Research, vol. 5, no. 3, pp. 163-176, September 28, 2001 © by the Palaeontological Society of Japan Further notes on the turrilitid ammonoids from Hokkaido- Part 2 (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XC) TATSURO MATSUMOTO' and TAKEMI TAKAHASHI ‘c/o Kyushu University Museum, Fukuoka, 812-8581, Japan *28-109 Hanazono-cho, Mikasa, 068-2124, Japan Received 11 December 2000; Revised manuscript accepted 10 May 2001 Abstract. Six species of Turrilites, two species of Mesoturrilites and two species of Mariella are de- scribed on the basis of material from the lower and middle parts of the Cenomanian (mid- Cretaceous) in the central and northwestern Hokkaido. Several of them are well known for their worldwide distribution and occur in Hokkaido at correlatable stratigraphic levels. Three new spe- cies, Turrilites complexus, T. miroku and Mesoturrilites pombetsensis, are established, showing in- teresting but still questionable relationships with some previously known ones. open nomenclature require further study. Two species in Key words: Cenomanian, Hokkaido, Mariella, Mesoturrilites, Turrilites Introduction The material from the Cretaceous Yezo Group of Hokkaido provides not only examples of well known, wide- spread species but also of other, little known or new ones. Selected examples of both categories are studied to improve systematic, biostratigraphic and biogeographic knowledge. The studied specimens came primarily from the Cenomanian of the Ikushunbetsu Valley of the Mikasa dis- trict, central Hokkaido, and the Abeshinai-Saku area of the Nakagawa district, northwestern Hokkaido. For the stratigraphy of the two areas, readers may refer to the two papers: Matsumoto (compiled, 1991, p. 3-5, 21-24) for the former and Matsumoto (1942, p. 180-214) for the latter. The material depends primarily on the collections of T. T. and T.M. In addition to them several specimens from these and also adjacent areas treated in the two papers written in Japanese, i. e., Nishida ef a/ (1997) and Hayakawa and Nishino (1999) are cited with brief remarks. An additional specimen from Abeshinai has been provided by M. Okamura. Repositories.—The specimens treated in this paper are Officially registered in the following institutions, with prefixes: GK: Geological Collections, Kyushu University Museum, Fukuoka, 812-8581, Japan GS: Geological Collections in Saga University, Saga, 840-8502, Japan IGPS: Museum of Natural History, Tohoku University, Sendai, 980-8578, Japan NMA: Nakagawa Museum of Natural History, Nakagawa, 098-2802, Hokkaido, Japan UMUT: University Museum, University of Tokyo, Hongo, Tokyo, 113-0033, Japan The specimen collected by T. T. is indicated with the pre- vious number in brackets. Likewise, the specimen collected by T. M. and once stored in UMUT under the heading of GT is indicated in brackets, for it is now officially transferred to GK. Systematic descriptions (continued from Part 1) Genus Turrilites Lamarck, 1801 Type species.— Turrilites costatus Lamarck, 1801 (p. 101) by original designation. Diagnosis. — Tightly coiled turrilitids with small apical angle. Ribs with no or two to four rows of tubercles; ribs and tubercles equal in number in all rows (modified from Wright and Kennedy, 1996, p. 349). Remarks.—Besides well known T. scheuchzerianus Bosc, 1801, 7. costatus Lamarck, 1801 and 7. acutus Passy, 1832, two new species established below occur in the Cenomanian of Hokkaido. Turrilites complexus sp. nov. Figures 1, 2, 3A-D 164 Tatsuro Matsumoto and Takemi Takahashi Figure 1. Turrilites complexus sp. nov. A, B. GK.H8552 (holotype). C, D. GK.H8553. E. GK.H8554. A, C, E: lateral views. B, D: basal views. Figures are all x1.5. Photos courtesy of M. Noda. Notes on the Turrilitidae-Part 2 165 Table 1. Measurements of Turrilites complexus Sp. nov. Specimen NW Hp Ht D ap h d h/d R(T) GK.H8552 9.0 84.0 102.0 30.0 20° 12.0 23.5 0.51 26-22 GK.H8553 8.5 87.0 105.3 33.5 19° 14.5 28.2 0.51 22-16 GK.H8554 7.0 103.5 133.0 31.0 20° 15.5 31.0 0.50 24-17 GK.H8550 TE 40.7 55.0 16.8 222 72 15.0 0.48 31-22 NMA-151 7.5 33.8 > 13.6 19° 5.3 11.0 0.48 27-23 (?) NW = number of preserved whorls, Hp = total height of the preserved shell, Ht = total height of shell from the pre- served last whorl to the estimated apex, D = diameter of the preserved last whorl, ap = estimated apical angle. h = height of an exposed flank of a late whorl, diameter of the same whorl, R or T = number of ribs or tubercles in a given row per whorl, showing change with growth, if any. Linear dimension is in mm. Material and occurrence.—Holotype is GK.H8552 [= previ- ous S.40-5-16] (Figure 1A, B; Figure 3A, B) collected by T. T. in 1965 at Loc. 1k1100, on the right side of the River Ikushunbetsu, from the lower part of the Member Ilb of the Mikasa Formation (see Matsumoto, 1991, p. 22, fig. 1). Paratypes from the type locality are GK.H8550 [= S.39-4-27] (Figure 3C, D), GK.H8553 [= S.40-8-7] (Figure 1C, D) and GK.H8554 [= S.50-4-13] (Figure 1E), collected by T. T. in 1964, 1965 and 1975 respectively. Another paratype is a large but incomplete specimen, GK.H8558 [= previous GT. I-3150] (Figure 2A, B), collected by T. M. in 1938 at Loc. T591b on the left side of the River Abeshinai of the Nakagawa district. Also NMA-151, collected by T. Nishino at “Loc. Y" [Yasukawa] and illustrated by Hayakawa and Nishino (1999, pl. 10, fig. f) as T. costatus, should now be transferred to this species. There are more examples from both Mikasa and Nakagawa districts, but at present they be- long to private possessions. Diagnosis.—Turreted shell with a low apical angle, show- ing the ontogenetic change of ornamentation from numer- ous, crowded ribs with scarcely discernible tubercles to the diagnostic ribs with tubercles of moderate intensity like Turrilites costatus. In addition to the three rows of ribs or tu- bercles like those of T. costatus, there are clavate small tu- bercles of the fourth row, from which radial ribs run on the lower (or basal) surface to the narrow umbilicus. The con- cave zone between the upper and lower ribs is faint in youth, moderately distinct in the middle or main stages, and may become indistinct at the last stage. Description.—The available specimens are scarcely af- fected by secondary deformation. They are, however, in- complete in that the very apex is lacking and their last whorl is more or less deficient. The holotype (Figure 1A, B; Figure 3A, B) and a paratype, GK.H8553 (Figure 1C, D) are slightly over 100 mm in the original height. In both speci- mens the preserved last whorl is still septate. GK.H8554 (Figure 1E) is the largest of the four specimens from the type locality, showing 133 mm in the total height of the shell. The body chamber is preserved in this specimen, but its apertural part is destroyed. GK.H8550 (Figure 3C, D) shows the characters of the young shell, although the initial part Is lacking. Figure 2. Turrilites complexus sp. nov. A, B. GK.H8558. Despite some deficiencies mentioned above, they show A is the detached lower whorl of B and slightly turned clockwise as a whole the above-described diagnostic characters. to show clearly the saddle between E and L. Figures are x1. This is also supplemented by the measurements (Table 1). Photos by C. Ueki. 166 Tatsuro Matsumoto and Takemi Takahashi Minor differences between specimens can ke regarded as infraspecific variation. For instance, the decrease in the rib density with growth varies from individual to individual (see Figure 4). The tubercles on the last whorl of GK.H8554 (Figure 1E) become weaker than those of the preceding whorls, but a similar feature often occurs in the last whorl of the turrilitid ammonoids. The septal suture at a young stage is exposed partly on GK.H8550. L is situated on the concave zone between the upper and lower ribs. The suture of a late growth stage is much incised (see Figure 2). The E-L saddle is so broad that L is shifted toward the lower whorl seam and U is in the middle part of the lower whorl face (Figure 2A). The incised branches of an element (probably |) are extended from the concealed side (Figure 2B). Comparison and discussion.—With respect to the charac- ters of the middle to late growth stages this species resem- bles Turrilites costatus Lamarck, but it is distinguished by the rigure 3. A-D. Turrilites complexus sp. nov. A, B. GK.H8552 (holotype). Fig. 3A is 180° turned from Fig. 1A; Fig. 3B is another basal view in a different light from Fig. 1B. Figures slightly over natural size. Turrilites aff. costatus Lamarck. acutus Passy, 1832. J. GS.G114, x2. (Coquand). GK.H8549, lateral and basal views, x2. G. Turrilites scheuchzerianus Bosc, 1801. exposed from the rock matrix, x1.5. H, |. Turrilites costatus Lamarck, 1801. K. GS.G113, x2. L. GS.G127, x1.7. GK.H8562, x2. Photos courtesy of M. Noda (A-D), N. Egashira (G, H, J-L) and C. Ueki (I, M, N). C, D. GK.H8550, lateral and basal views, x2. E, F. Gk.H8563, half I. GK.H8560, x1. J-M. Turrilites N. Mesoturrilites cf. aumalensis H. GK.H1373, x2. M. GK.H8559, x1. Notes on the Turrilitidae-Part 2 167 NUMBER OFRIBS 20 DA 4 30 40mm WHORL DIAMETER Figure 4. Diagram showing the ontogenetic change of rib density in some representative specimens of Turrilites complexus sp. nov. (small solid circle), Turrilites costatus Lamarck (solid square), and Turrilites scheuchzerianus Bosc (solid triangle). 1: GK.H8550, 2: GK.H8552 (holotype), 3: GK.H8554, 4: GK.H8553, 5: GK.H8560, 6: BGS GSM 7772 (Sharpe, 1857, pl. 26, fig. 1). presence of spirally elongated tubercles of the fourth row. In younger growth stages the two species are undoubtedly different in ornamentation. Also, as is shown in Figure 4, in contrast to the ontogenetic decrease of rib density in T. complexus, T. costatus maintains uniform density with growth. With respect to the morphological characters of young shells this species resembles Turrilites scheuchzerianus Bosc in showing interrupted ribs on rather flat or only gently convex flank, without or with very faintly appeared swellings. The number of ribs seem to vary between individuals in 7. scheuchzerianus, but the decrease of the number with growth is not so remarkable as in T. complexus. Again, the presence of the clavate tubercles of the fourth row in T. complexus is a distinction. As to the characters of the mid- die to late stages T. complexus is clearly different from T. scheuchzerianus. Stratigraphically T. complexus first appears from a lower level than T. scheuchzerianus and T. costatus. Hence, it can be presumed that the latter two species may have branched from the former almost simultaneously or succes- sively at slightly different times. The middle-aged shell of this species resembles Mariella (Mariella) oehlerti (Pervinquière, 1910) (see also Matsumoto et al., 1999, p. 109, figs. 2-4; Matsumoto et al., 2000, p. 8, fig. 3) in the whorl shape and ornamentation. The latter shows a wide extent of variation in the density of tubercles, as Klinger and Kennedy (1978, p. 32, fig. 9) have demon- strated. But the ontogenetic change of ornament in the lat- ter species is not so great as in T. complexus. On the average tubercles are predominant over ribs in M. (M.) oehlerti, but ribs in the upper row characterize the middle- aged whorls of T. complexus as in the main part of the T. costatus shell. The spirally elongated tubercles of the fourth row are common in M. oehlerti and T. complexus. There is, however, to some extent infraspecific variation. For instance, Klinger and Kennedy (1978, p. 33) pointed out the presence of “variety A” in M. (M.) oehlerti “which differs from the “typical form” in possessing moderately to well- developed ribs’. Numerous specimens of M. (M.) oehlerti from Zululand and Natal in South Africa seem to be more or less fragmentary, as are shown by the illustrations by Klinger and Kennedy (1978, pl. 6, figs. H-N, P; pl. 7, fig. G). If frag- mentary pieces of a middle-aged shell of 7. complexus were mixed with them, they might be regarded as the ribbed vari- ety of M. (M.) oehlerti. Discussion.—This species occurs in the lower part of the Member Ilb of the Mikasa Formation. This unit is biostratigraphically defined as the Zone of Mantelliceras japonicum - Sharpeiceras kongo, that is, the second unit in the three subdivisions of the lower Cenomanian in the Ikushunbetsu Valley. It was erroneously listed as Turrilites costatus in the stratigraphic notes by Matsumoto et al. (1969, p. 287) and also Matsumoto (in, Matsumoto, 1991, p. 22). It occurs also in the Abeshinai Valley of the Nakagawa district. A specimen from Loc. T591b is referable to the middle or upper part of the lower Cenomanian, because Loc. T591b is above Loc. T591a, where Mesoturrilites cf. aumalensis (Coquand, 1862) (see description in later pages) was obtained, and well below Loc. T591d, where Turrilites acutus Passy, 1832 (see below) occurred. The “Locality Y” of Yasukawa, where a specimen of T. complexus (NMA-151) was collected, is a fairly extensive exposure of Strata, about 70 m in thickness, but the stratigraphic level of NMA-151 is not precisely recorded by Hayakawa and Nishino (1999). Although they ascribed the entire thickness of the exposed strata of “Loc. Y” to the middle Cenomanian, the assignment is questionable, because Cunningtoniceras 168 Tatsuro Matsumoto and Takemi Takahashi Table 2. Measurements of Turrilites costatus Lamarck. Specimen NW Hp Ht D ap h d h/d R(T) GK.H8560 6 105.0 150.0 41.0 20° 20.0 37.0 0.54 22 NMA-145 5 115.0 165.0 45.0 23° 24.0 42.5 0.56 ca.21 Legend as for Table 1. In NMA-145 about 120° of each whorl is embedded in the rock matrix. Table 3. Measurements of Turrilites aff. costatus Lamarck. Specimen NW Hp Ht D ap h d h/d R(T) GK.H8549 8.0 19.6 20.8 10.2 32 3.7 8.0 0.46 15-24 Legend as for Table 1. sp., an index of middle Cenomanian, was obtained, accord- ing to the collector (Yutaka Koike), from the uppermost part of the sequence. At present this species is known to occur only in Japan. In view of the worldwide distribution of 7. scheuchzerianus and T. costatus, whether T. complexus has a more exten- sive distribution should be clarified. Turrilites scheuchzerianus Bosc, 1801 Figure 3G Turrilites scheuchzerianus Bosc, 1801, p. 190; Wright and Kennedy, 1996, p. 349 (with full synonymy) Type.—“The status and whereabouts of the type material (Bosc, 1801, p. 190) have not been well established” (Wright and Kennedy, 1996, p. 349). Material.—GK.H8563 [= previous GT.1-3154] (Figure 3G) collected by T. M. from a floated nodule at Loc. T32-33p, Saku-gakko-no-sawa, Nakagawa district. NMA - 144, NMA-143 and NMA-142, collected by T. Nishino from “Loc. T” of Nakagawa district and described in Japanese by Hayakawa and Nishino (1999, p. 11, pl. 10, figs. a, b-c, e). Descriptive remarks.—This species has been amply de- scribed and discussed by Wright and Kennedy (1996, p. 349, pl. 106, figs. 7, 8, 11, 12; pl. 107, figs. 1-7; text-figs. 137G, J; 138C, D, F-I, N; 139D-I; 140A, D-I; 143H; 147A, B) on the basis of numerous specimens from South England and extensive regions in the world. In addition to the speci- mens reported by Hayakawa and Nishino (vide supra), we know that a well preserved specimen occurred in the Zone of Cunningtoniceras takahashii at Loc. IK1051b of the Ikushunbetsu Valley. It is quite similar to a British specimen (BMNH 30210, Wright and Kennedy, 1996, pl. 107, fig. 7), but it is not officially registered. Distribution.—Middle part of the Cenomanian in Hokkaido. For the range in South England and the worldwide distribu- tion see Wright and Kennedy, 1996, p. 353. Turrilites costatus Lamarck, 1801 Figure 3 H, | Turrilites costatus Lamarck, 1801, p. 102 (pars); Wright and Kennedy 1996, p. 354, pl. 103, figs. 1, 2, 5; pl. 104, figs. 1-4, 6, 8-10; pl. 105, figs. 1, 5, 6, 10, 12, 13, 16, 17, 19; pl. 106, figs. 1-6, 9, 10; text-figs. 137C; 139A-C; 142A, F, G; 143A-G, L-P (with full synonymy). Type. —The specimen from Rouen figured by Douvillé (1904, p. 54a, fig. 1) in the Lamarck Collection is the lectotype designated by Kennedy (1971, p. 30). It is kept in the Muséum National d’Histoire Naturelle, Paris and was reillustrated by Wright and Kennedy (1996, text-fig. 142F). Material and occurrence.— GK.H8560 [= GT.I-3157a] (Figure 31) and GK.H8561 (not figured) collected by T. M. in 1938 on the left side of the River Shakotan [= Sakugawal; NMA-176 and NMA-145 collected by T. Nishino from “Loc. T” on the right bank of the River Teshio, all in the Nakagawa district. GK.H1373 (Figure 3H) collected by T. M. in 1939 from Loc. Y524, Tengu-zawa of the Shuparo area (for the lo- cation see Matsumoto, 1942, pl. 25). Descriptive remarks.—This specimen is well defined by previous authors, especially by Wright and Kennedy, 1996 (vide supra). GK.H8560 is a good example from Hokkaido, for it resembles the lectotype. NMA-145 could be regarded as a passage form to T. acutus Passy in its pointed tuber- cles. It is, however, quite similar to GK.H8560 (see ap, h/d and R(T) in Table 2). Distribution.—The described specimens from Hokkaido are of middle Cenomanian age. For the range in England and also worldwide distribution of this species see Wright and Kennedy, 1996, p. 358. Turrilites aff. costatus Lamarck, 1801 Figure 3 E, F Material_—A single specimen, GK.H8549 [= previous S.4 3-5-7] (Figure 3E, F) collected by T. T. in 1968 at Loc. Ik1100 from the lower part of the Member Ilb of the Mikasa Formation. Descriptive remarks.—This is a small, probably immature specimen. It looks like T. costatus, but it shows a larger apical angle and lower whorls in comparison with the latter (compare Table 3 with Table 2). Its younger whorls show rather prominent tubercles in the upper row at moderate in- tervals (15-17 per whorl) and corresponding number of small tubercles in the lower row. Hence, the young shell is rather similar to T. acutus (vide post). The later whorls have tuberculated ribs like those of T. costatus, but they are rather Notes on the Turrilitidae-Part 2 169 Table 4. Measurements of Turrilites acutus Passy. ap h d h/d V Specimen NW Hp Ht D GK.H8559 3 40.0 77.0 32.5 Pr 12.0 25.0 0.48 20 NMA-131 6 50.0 60.0 25.0 30° 9.0 19.0 0.47 18 GK.H8551 9 175.0 = ca.77 = ca.32 ca.67 ca.0.48 20 Legend as for Table 1. GK.H8551 is so much deformed that D and d are roughly estimated on the basis of the measured maximum and minimum dimensions. crowded and numerous (24 in the preserved last whorl). There are closely set two rows of spirally elongated tuber- cles along the lower whorl seam. Thus, the shell of this stage is similar to the middle-aged shell of 7. complexus. The morphological characters of the still later stage of this specimen are not known. Despite the incomplete preservation, the specimen is so peculiar that it is tentatively described under the above heading. Its relation with Mariella (M.) oehlerti (Pervingiere, 1910) (see Matsumoto et al., 1999) should be examined on the basis of further material. Turrilites acutus Passy, 1832 Figures 3 J-M, 5, 6 Turrilites acutus Passy, 1832, p. 9, pl. 16, figs. 3, 4; Wright and Kennedy, 1996, p. 358, pl. 103, fig. 3; pl. 104, figs. 5, 7, 11; pl. 105, fig. 21; pl. 108; figs. 1-4, 8, 11, 12; text-figs. 138M; 141A; 146N-O (with full synonymy). Lectotype.—The original of Passy, 1832, pl. 16, fig. 3 by the subsequent designation of Juignet and Kennedy, 1977, p. 65. For its photographic illustration see Wright and Kennedy, 1996, pl. 108, fig. 8a-c. Material and occurrence.—GK.H8559 [= previous GT.I- 3155] (Figure 3M) collected by T. M. in 1938 at Loc. T591d, a cliff on the left side of the River Abeshinai and NMA-131 collected by Nishino from “Loc. T” on the right bank of the River Teshio (Hayakawa and Nishio, 1999, p. 11, pl. 10, fig. h), both in the Nakagawa district. GS.G113, GS.G114 and GS.G127 (Figure 3K, J, L; reproduced here from Nishida et al., 1997, pl. 7, figs. 10, 11 and pl. 12, fig. 5) collected by Kawashita and Egashira from a floated nodule in the Fuku- no-sawa, a branch of the River Shumarinai in the Soeushinai area (for the location see Nishida et al., 1997, text-fig. 8). GK.H8551 [= previous S.43-4-30] (Figure 5) collected by T. T. in 1968 at Loc. Ik1102, north side of the River Ikushunbetsu, from the bed with Cunningtoniceras takahashii (Matsumoto). The above records of occurrence all indicate a middle Cenomanian age. Diagnosis.—On the basis of the previous works the diag- nosis may be written as follows. A species of Turrilites characterized by pointed tubercles of two rows on the flank, with a concave zone between them, and also clavate smaller tubercles of the third row along the lower whorl seam; the upper tubercles are bullate upward; weak radial ribs may run on the lower surface at least partly. Whorls are rather low, showing h/d below 0.5; hence the apical angle is normally 25°-30°. Description. — GK.H8559 is similar to the lectotype and some other specimens of the corresponding growth stage, e. g., those illustrated by Wright and Kennedy (1996, pl. 106, figs. 1, 2, 8, 17) or by Atabekian (1985, pl. 29, figs. 1, 2, 4). Figure 5. Turrilites acutus Passy, 1832. GK.H8551. Lateral view of a deformed specimen, x0.8. Photo courtesy of M. Noda. 170 Tatsuro Matsumoto and Takemi Takahashi On the basal surface of GK.H8559 weak radial ribs run from the clavate tubercles of the third row, showing a gentle cur- vature. The suture is well shown on this specimen (Figure 6). It is essentially similar to the suture illustrated by Atabekian (1985, pl. 29, figs. 1a, 1b). GK.H8551 is a large specimen, although it is deformed. The diagnostic characters are clearly manifested by its main part, but in its later whorls the tubercles are rather blunt and transitional to longer ribs (see Figure 5). Figure 6. Distribution. —Middle Cenomanian in Hokkaido. For the worldwide distribution see Wright and Kennedy (1996, p. 361). Turrilites miroku sp. nov. Figure 7 Material.—Holotype, here designated, is GK.H5916 from Loc. Ik1067p, Shimo-ichino-sawa of the Ikushunbetsu Turrilites acutus Passy, 1832. Septal suture of GK.H8559 at h = 12.5 mm. Broken line = whorl seam, dotted line = approximate outline of a tubercle or rib, E = external lobe, L = lateral lobe, U = umbilical lobe. A branch of an internal element (probably I) is extended from the unexposed side. Figure is about x4. Drawing by T. M. Figure 7. Turrilites miroku sp. nov. GK.H5916 (holotype). Two lateral (A and B turned 180°) and basal (C) views; also another lateral view (D) which is turned 120° anticlockwise from A. A-C are x1; Dis x1.5. Photos courtesy of M. Noda. Notes on the Turrilitidae-Part 2 171 Table 5. Measurements of Turrilites miroku sp. nov. Specimen NW Hp Ht D GH.H5716 4 68.0 107.0 31.0 Legend as for Table 1. Valley. Specific name.—Miroku [= Maitraya in Sanskrit], a deity in Buddhism, who will help people in the remote future. Diagnosis.—A species of Turrilites with small apical angle. Each whorl is characterized by downward steeply inclined flat flank, with its maximum diameter at the level of lower tu- bercles. The upper, longer ribs rather weak and faintly tuberculated at their lower end. Lower ribs short, prorsiradiate, and sharply tuberculated in their upper part, terminating at the smaller tubercles of the third row aligned along the lower whorl seam. The lower (or basal) whorl face gently convex and nearly smooth. Description.—The holotype consists of four whorls of 68 mm in total height. It lacks the whorls of the early and also the last stages. Assuming that one more whorl is the lost body chamber, the restored shell would be at least 105 mm in total height and 40 mm in diameter of the basal surface. The estimated apical angle is 21° Each whorl of this specimen shows a peculiar shape, for its main part of the flank is flat, without convexity, and steeply inclines downward to the level of the prominent tu- bercles in the lower part, where the maximum diameter is lo- cated. Downward from this level, the lower portion of the flank inclines inward for a short distance to the lower whorl seam. Whorls are tightly in contact. The ratio of height (h) to diameter (d) in each whorl, excluding the unexposed lower surface, distinctly exceeds 0.5 (see Table 5). The ornament is also peculiar to this species. The ribs on the upper flank are weak but moderately numerous, 22 per whorl. Each of them terminates at a small and blunt tuber- cle. Below this first row of tubercles there is a narrow and shallow, spiral groove; then comes the second row of mod- erately prominent tubercles, where the flank is somewhat angular at the tubercle or shouldered along the interspace. A short but sharp rib runs from each tubercle of the second row downward to a less prominent small tubercle of the third row, which runs along the lower whorl seam. The upper nbs run transversally with slight curvature, whereas the lower ribs are clearly prorsiradiate together with the bullate tubercles. Lower or basal surface of the whorl is almost smooth and gently inflated around a narrow umbilicus. Septal sutures are partly exposed but not clearly traced. Comparison.—At present only one specimen (holotype) is available for this species. Its approximate size described above is somewhat larger than the lectotype of Turrilites acutus Passy, 1832 (pl. 16, fig. 3; reillustrated by Wright and Kennedy, 1996, pl. 105, fig. 5) and probably smaller than the lectotype of Turrilites wiestii Sharpe, 1857 (pl. 27, fig. 8; reillustrated by Wright and Kennedy, 1996, pl. 105, fig. 18). Some young shells of Turrilites scheuchzerianus Bosc, 1801, exemplified by such specimens as illustrated by Wright and Kennedy (1996, text-fig. 138C-D, F-G, N; pl. 107, fig. 1), are somewhat similar to the present species in showing a downward broadening whorl, nodelike swelling, if not tuberculation, of the lower ribs, and the smooth basal surface. However, in typical examples of T. scheuchzeria- nus the apical angle is smaller, the whorl flank is gently con- vex, and the tubercles are not developed. With respect to the characteristic whorl shape, the present species is similar to a certain form of T. wiestii represented by a group of specimens illustrated by Wright and Kennedy, 1996, pl. 105, figs. 7, 8, 11 and pl. 108, figs. 9, 13. It is, however, different from the above form as well as the lectotype of 7. wiestii (Sharpe, 1857, pl. 27, fig. 8; reillustrated by Wright and Kennedy, 1996, pl. 105, fig. 18) in its more numerous and less distant ribs with weaker tuber- cles. The lectotype shows a dissimilar whorl shape. This species could be referred to the subgenus Ostlingoceras (Ostlingoceras) Hyatt, 1900, but in the latter the transversal ribs are more numerous and crowded, the tu- bercles of the second row are smaller and weaker, and the lower (or basal) surface of the whorl has radial ribs, with third and/or fourth rows of small tubercles on its marginal zone. The ribs on the holotype of T. miroku are 22 per whorl, showing nearly the same density as that of T. costatus (see Tables 2 and 5). Discussion.—This species is somewhat peculiar in its morphological characters. In this paper it is assigned at least tentatively to Turrilites on the grounds of the above comparison. The holotype of this species was in a transported nodule, which can be inferred to have been derived from somewhere in the lower Cenomanian on account of its having been re- covered close to Loc. Ik1065b, where a lower Cenomanian species, Ostlingoceras (O.) bechei (Sharpe) was obtained (see Matsumoto and Takahashi, 2000, p. 262). It should be noted that 7. wiestii is recorded from the lower Cenomanian of England near the boundary of the Mantelliceras dixoni Zone and the Acanthoceras rhotomagense Zone (Wright and Kennedy, 1996, p. 354). At any rate, we have to get more material to clear up questionable points about the systematic and biostratigraphic allocation of the present species. Genus Mesoturrilites Breistroffer, 1953 Type species.—Turrilites aumalensis Coquand, 1862. Diagnosis.—Turrilitid ammonoids with four rows of tuber- cles or ribs; the first row on the main part of flank made up of ribs and/or tubercles, the second and the third rows of small tubercles on spirally elongated, narrow ridges sepa- rated by a groove; the fourth row of small tubercles on the marginal zone of the lower whorl surface where radial ribs run to a narrow umbilicus (modified from Matsumoto and Inoma, 1999, p. 37). 172 Tatsuro Matsumoto and Takemi Takahashi Mesoturrilites cf. aumalensis (Coquand, 1862) Figure 3 N Compared.— Turrilites aumalensis Coquand, 1862, p. 323, pl. 35, fig. 3. Mesoturiilites aumalensis (Coquand, 1862). Wright and Kennedy, 1996, p. 346, pl. 98, fig. 5; pl. 105, figs. 2, 3, 14; text-figs. 134J, K; 138S-U, W; 146A-G (with full synonymy). Material_—GK.H8562 [= previous GT.I-3310] (Figure 3N), collected by T. M. in 1938 at Loc. T591a, the lowest part of a sequence of strata exposed on the right side of the River Abeshinai in the Nakagawa district. Descriptive remarks.—This specimen is small and incom- pletely preserved. It shows a pyramidal shape, conical tu- bercles of moderate intensity and density at about the midflank, and corresponding number of spirally elongated tu- bercles in two rows, with a narrow groove in between, along the lower whorl seam. The clavate tubercles of the fourth row and radial ribs arising from them are faintly discernible on the lower face. Although the preservation is insufficient, this specimen can be called Mesoturrilites cf. aumalensis. It occurs at the level immediately below that of Turrilites complexus (vide ante). Mesoturrilites pombetsensis sp. nov. Figures 8, 9 Material and occurence.—Holotype, here designated, is GK.H8532 [= previous S. 37-7-17] (Figure 8A-D) collected by T. T. in 1963 from a transported nodule on the Onkonosawa, a branch of the River Ponbetsu in the Mikasa district. Paratype is GK.H8548 (Figure 8E, F), collected by T. T. at Loc. 1k1101 on the right side of the R. Ikushunbetsu. The fossiliferous sandy rocks which contain the above speci- mens are referred to the lower part of the Member IIb of the Mikasa Formation. Diagnosis. — Pyramid-shaped species of Mesoturrilites Figure 8. A-F. Mesoturrilites pombetsensis sp. nov. views of GK.H8532 (holotype), slightly, over natural size. Noda. Three lateral (A, B and C turned about 120° anticlockwise) and basal (D) Lateral (E) and basal (F) views of GK.H8548, x1.67. Photos courtesy of M: Notes on the Turrilitidae-Part 2 173 Table 6. Measurements of Mesoturrilites pombetsensis sp. nov. Specimen NW Hp Ht D ap h d h/d GK.H8532 5.5 55.0 60.0 46.0 47° 14.7 33.7 0.44 18 GK.H8548 3.0 29.0 42.0 28.0 45° 8.3 19.3 0.43 22 Legend as for Table 1. with moderate apical angle, ornamented by fairly coarse ribs on the upper flank, each of which is provided with a node at about the midflank immediately above a shallow concave zone; also two closely set rows of spirally elongate tubercles in the lower part with a groove in between. In more or less later stages the prorsiradiate ribs run across the concave zone and the groove. The ribs further extend radically on the gently convex lower (or basal) surface, with tubercles of the fourth row on the margin of the circular base. Description.—The holotype consists of nearly six septate whorls, with a fraction of crushed body chamber at the pre- served end (Figure 8A, D). It is moderately large (Table 6). A single paratype is small and corresponds to the young part of the holotype. The entire shell shape is pyramidal; the ex- posed outer face of the whorl consists of a nearly flat or gen- tly inclined upper portion, steeply inclined main part, and incurved lower portion. The interwhorl junction is deep. The ornament somewhat changes with growth. In the early growth stage the upper ribs are very coarse and tuberculated at their lower end. This is well manifested at the early stage (with d < 15 mm) of the paratype, but is less clear in the holotype. Below the zone of upper ribs a shal- lowly concave, spiral zone runs at about the midflank. In the middle to late growth stages, the ribs are elongated and the spiral groove is reduced. The prorsiradiate ribs run across the shallowing groove and connect themselves with the spirally elongated tubercles of the second and third rows. They extend to the radial ribs on the lower surface. The ribs are curved at about the rounded, small tubercles of the fourth row. On the well preserved lower face, delicate spiral lines or lirae may be observed and tiny dots may be discerni- ble at the crossing points with the radial ribs (Figure 8 D, F). Septal suture is deeply and finely indented. Moreover, the extra branches of a lobe (1?) are extended from the other side (Figure 9). Comparison and discussion.—The holotype of this spe- cies is the largest among hitherto reported specimens of Mesoturrilites. If its body chamber is preserved, it would be about 80 mm in height and 75 mm in basal diameter. However, it is actually difficult to estimate the real size of the adult shell in the previously described species, because their types are incompletely preserved. The present species is somewhat allied to Mesoturrilites aumalensis (Coquand, 1862) (p. 323, pl. 35, fig. 3), rede- fined by Wright and Kennedy (1996, vide ante) in the gen- eral shell shape and the ornamentation of the young stage. In later growth stages ribs become predominant in the for- mer, whereas tubercles characterize the latter. In this re- spect this species may be somewhat allied to M. corrugatus Wright and Kennedy (1996, p. 348, pl. 98, figs. 4, 17), but the ribs in the latter are narrower and sharper, without such Figure 9. Mesoturrilites pombetsensis sp. nov. External suture of GK.H8532 (holotype) ath = 15 mm. Figure is about x4. Symbols as for Figure 6. Drawing by T. M. nodes as seen on the ribs of M. pombetsensis. Distribution.—At present this species is represented by only two specimens from the lower part of the Cenomanian in Hokkaido. Although they are fairly well preserved, more material should be searched for to ascertain the vertical range and geographical distribution. Genus Mariella Nowak, 1916 Subgenus Mariella (Mariella) Nowak, 1916 Remarks.— Altogether 10 species of M. (Mariella) from Hokkaido have been recently described (Matsumoto et al., 1999; Matsumoto and Kawashita, 1999; Matsumoto and Kijima, 2000; Matsumoto et al., 2000). Two more species are described below. Mariella (Mariella) cenomaniensis (Schlüter, 1876) Figure 10 Type. —Lectotype, by the subsequent designation of Kennedy, 1971 (p. 29), is the original of Schlüter, 1876, pl. 37, fig. 6. The specimen illustrated by Wright and Kennedy (1996, text-fig. 141B) is supposed to be this specimen. Material and occurrence.—Gk.H8557 [= previous S.55-9- 14] (Figure 10A, B), collected by T. T. in 1960 at the point of the Hachigatsu-zawa, near the confluence with the branch rivulet called the Okufutamata-zawa. It is in a calcareous nodule of fine sandstone derived probably from the lower 174 Tatsuro Matsumoto and Takemi Takahashi Figure 10. Mariella (Mariella) cenomanensis (Schlüter, 1876). Lateral (A) and basal (B) views of GK.H8557, x1.5. Photos courtesy of M. Noda. Cenomanian part exposed upstream from this locality (see the Geological Map of Kamiashibetsu by Shimizu et al, 1953). Description.—This single specimen is small but it shows 9 whorls. Its estimated apical angle is low (about 20°), al- though it is somewhat deformed. The outer exposed whorl face is convex and the whorl junction is deeply impressed. The exposed part of each whorl in lateral view is compara- tively high, showing h/d = 0.62 in a measured part. The tubercles in two rows on the main part of the flank are coarse, numbering 18 per whorl in each row. There is a smooth sloping zone above the upper row of subrounded tu- bercles. The tubercles of the second row are somewhat clavate. There are spirally elongated tubercles of the closely set third and fourth rows at about the edge between the lateral and lower (or basal) faces. Remarks.—This specimen resembles smaller examples of M. (M.) cenomanensis, e. g., those described by Kennedy (1971, p. 28, pl. 8, fig. 10) and Atabekian (1985, p. 41, pl. 10, figs. 1-6). It is certainly identified with this species on the grounds of the described characters. The apical angle 23° by Wright and Kennedy (1996, p. 342) is somewhat larger than that in ours or in Atabekian’s small specimens. This may depend on estimations made from the whorls of differ- ent growth stages. Distribution.—M. (M.) cenomanensis has been reported to occur in the lower Cenomanian of various regions in the world (see Wright and Kennedy, 1996, p. 344). Mariella (Mariella) aff. circumtaeniata (Kossmat, 1895) Figure 11 Compared. — Turrilites circumtaeniatus Kossmat, 1895, p. 141, pl. 18, figs. 4, 5. Mariella (Mariella) circumtaeniata (Kossmat, 1895). Klinger and Kennedy, 1978, p. 26, pl. 5, figs. A-C; text figs. 3G, 6D (with full synonymy) Material. —IGPS 108380 (Figure 11A, B), collected by Makoto Okamura in 1972, at his Loc. AB14 [= Loc. T590c of Matsumoto (1942)] on the left side of the River Abeshinai in the Nakagawa district. Descriptive remarks.—This specimen is a highly distorted body chamber, measured as 106 x 50 mm in the basal out- line. The flank on the figured part (Figure 11A) is well rounded, but the other side is flattened. The ornament con- sists of three rows of tubercles and the looped ribs. The looping or intercalation of the ribs is frequent in the space between the upper row of tubercles and the upper whorl seam. The interval between the upper and middle rows of tubercles is slightly wider than that between the middle and lower rows. The coiling is sinistral and the ribs are prorsiradiate, extending to the radial ones on the basal sur- face. The tubercles of the first row and the ribs of the upper part are very weak. Whether this is the original character or a secondary feature created by weathering is not clear. As the body chamber alone is available, we have to leave the present material in open nomenclature. More material should be searched for to clear up the classification. M. (Mariella) circumtaeniata has been reported to occur in the upper Albian of southern India, Madagascar, South Africa (Zululand) and (?) New Zealand (see Klinger and Kennedy, 1978, p. 26). The locality of the present speci- men is referred to the Unit Ila (lower part of the Cenomanian) in the Abeshinai Valley. Notes on the Turrilitidae-Part 2 175 Figure 11. body chamber). Conclusions To conclude this paper the following results are summa- rized. (1) Three well known species of worldwide distribution, Turrilites scheuchzerianus Bosc, T. costatus Lamarck and T. acutus Passy, occur in the middle Cenomanian of Japan. (2) Turrilites complexus sp. nov. is established on several specimens from the Mikasa and Nakagawa districts of Hokkaido, which were previously misidentified with T. costatus. This new species shows in youth some features of T. scheuchzerianus and later those of T. costatus. It re- tains also some characters of Mariella (Mariella) oehlerti (Pervinquiere). (3) Another new species, T. miroku, based on a single specimen from Mikasa, is similar in some respects to a cer- tain form of T. wiestii Sharpe, but distinct from the lectotype of the latter. Further study of more material is required. (4) Mesoturrilites cf. aumalensis (Coquand) is found in the lower Cenomanian of Nakagawa. Furthermore, M. pombetsensis sp. nov. is erected on the specimens from the lower Cenomanian of Mikasa. It has distinct ribs and weaker tubercles. (5) Mariella (Mariella) cenomanensis (Schlüter), another cosmopolitan, is first recorded from Hokkaido. (6) M. (M.) aff. circumtaeniata (Kossmat) is reported from Nakagawa, but more material is required for adequate tax- onomy and age correlation. Mariella (Mariella) aff. circumtaeniata (Kossmat, 1895). A is x1 and B is x0.8. Photos courtesy of M. Noda. Lateral (A) and basal (B) views of IGPS 108380 (a crushed Acknowledgments Makoto Okamura provided a specimen which he obtained from the Abeshinai Valley. Hiroshi Hayakawa. and Takanobu Nishio allowed us to examine the specimens stored in the Nakagawa Museum of Natural History, where Yoshinori Hikita helped us. Tamio Nishida supported us by reproducing some specimens in his care at Saga University and further helped us in various other ways. To compare the specimens from Japan with those from England one of us (T. M.) visited the Natural History Museum, where he owed much to D. Phillips. Photographs were taken by Chuzaburo Ueki, Naoko Egashira and Masayuki Noda. Kazuko Mori assisted us in preparing the manuscript. Two anonymous referees helped us to improve the manuscript. We thank all of these persons for their kindness. References cited Atabekian, A. A., 1985: Turrilitids of the late Albian and Cenomanian of the southern part of the USSR. Academy of Sciences of the USSR, Ministry of Geology of the USSR, Transactions, vol. 14, p. 1-112, pls. 1-34. (in Russian) Bosc, J. A., 1801: /n, Buffon, G. L. Leclerc, Comte de, Histoire Naturelle des Coquilles, 5, Paris, 395p. Breistroffer, M., 1953: L’evolution des Turrilitidés albiens et cénomaniens. Compte Rendus Hebdomadaires des Sciences de l'Académie des Sciences, vol. 237, p. Tatsuro Matsumoto and Takemi Takahashi 1349-1351. Coquand, H., 1862: Geologie et paléontologie de la region sud de la Province de Constantine. Mémoires de la Societe d'Emulation de la Province, Marseille, vol. 2, p. 1-320, 321-341 (supplement), pls. 1-35. Douvillé, H., 1904: Turrilites costatus Lamarck. Paléontologie Universalis, no. 54, p. 54-54b. Hayakawa, H. and Nishino, T., 1999: Cenomanian ammonite fauna from Nakagawa, Hokkaido, Japan. Bulletin of Nakagawa Museum of Natural History, vol. 2, p. 1-40. (in Japanese with English abstract) Hyatt, A., 1900: Cephalopoda. In, Zittel, K. A.: Textbook of Palaeontology, 1st English edition translated by C. R. Eastman, p. 502-592. Macmillan, London and New York. Juignet, P. and Kennedy, W. J., 1977: Faunes d’Ammonites et biostratigraphie comparée du Cénomanien du nordouest de la France (Normandie) et du sud de l’Angleterre. Bulletin trimestriel, Société Géologique de Normandie et des Amis de Muséum du Havre, vol. 63, p. 1-192. Kennedy, W. J., 1971: Cenomanian ammonites from southern England. Special Papers in Palaeontology, vol. 8, p. 1- 133, pls. 1-64. Klinger, H. C. and Kennedy, W. J., 1978: Turrilitidae (Cretaceous Ammonoidea) from South Africa, with a dis- cussion of the evolution and limits of the family. Journal of Molluscan Studies, vol. 44, p. 1-48, pls. 1-9. Kossmat, F., 1895: Untersuchungen über die Südindische Kreide-Formation. Beiträge zur Paläontologie und Geologie Oesterreich-Ungarns und des Orients, vol. 9, p. 97-203, pls. 15-25. Lamarck, J. B. P. A. de Monet de, 1801: Systeme des animaux sans vertebres, Paris, 432p. Matsumoto [Matumoto], T., 1942: Fundamentals in the Cretaceous stratigraphy of Japan, Part 1. Memoirs ofthe Faculty of Science, Kyushu Imperial University, Ser. D, vol. 1, no. 3, p. 129-280, pls. 1-20. Matsumoto, T. (compiled), 1991: The mid-Cretaceous am- monites of the family Kossmaticeratidae from Japan. Palaeontological Society of Japan, Special Papers, no. 33, p. i-vi, 1-148, pls. 1-31. Matsumoto, T. and Inoma, A., 1999: The first record of Mesoturrilites (Ammonoidea) from Hokkaido, Paleontological Research, vol. 3, no. 1, p. 36-40. Matsumoto, T., Inoma, A. and Kawashita, Y., 1999: The turrilitid ammonoid Mariella from Hokkaido - Part 1. Paleontological Research, vol. 3, no. 2, p. 106-120. Matsumoto, T. and Kawashita, Y., 1999: The turrilitid ammonoid Mariella from Hokkaido-Part 2. Paleontologi- cal Research, vol. 3, no. 3, p. 162-172. Matsumoto, T. and Kijima, T., 2000: The turrilitid ammonoid Mariella from Hokkaido-Part 3. Paleontological Resear- ch, vol. 4, no. 1, p. 33-36. Matsumoto, T., Muramoto, T. and Takahashi, T., 1969: Selected acanthoceratids from Hokkaido. Memoirs of the Faculty of Science, Kyushu University, Ser. D, vol. 19, no. 2, p. 251-296, pls. 25-38. Matsumoto, T. and Takahashi, T., 2000: Further notes on the turrilitid ammonoids from Hokkaido-Part 1. Paleontologi- cal Research, vol. 4, no.4, p. 261-273. Matsumoto, T., Takashima, R. and Hasegawa, K., 2000: Some turrilitid ammonoids from the mid-Cretaceous of the Shuparo Valley, central Hokkaido. Bulletin of the Mikasa City Museum, Natural Science, no. 4, p. 1-13. Nishida, T., Matsumoto, T., Kawashita, Y., Egashira, N., Aizawa, J. and Ikuji, Y., 1997: Biostratigraphy of the mid- dle part of the Cretaceous Yezo Group in the Soeushinai area of Hokkaido - with special reference to the transi- tional part from Lower to Upper Cretaceous: supplement. Journal of the Faculty of Culture and Education, Saga University, vol. 1, no. 1, p. 237-279. (in Japanese with English abstract) Nowak, J., 1916: Uber die bifiden Loben der oberkretazischen Ammoniten und ihre Bedeutung für die Systematik. Bulletin International de l’Académie des Sciences de Cracovie, serie B, 1915, p. 1-13. Passy, A., 1832: Description géologique du département de la Seine inférieure, Rouen, 371 p., 20 pls. Pervinquiere, L., 1910: Sur quelques ammonites du Cretacé algerien. Mémoires de la Sociéte Géologique de France, Paléontologie, vol. 17, mémoir 42, p. 1-86, pls. 1-7. Schlüter, C., 1876: Cephalopoden der oberen deutschen Kreide. Palaeontographica, vol. 24, p. 121-264, pls. 36-55. Sharpe, D., 1857: Description of the fossil remains of Mollusca found in the Chalk of England. Cephalopoda, part 3. Monograph of the Palaeontographical Society, London, no. 36, p. 37-68, pls. 17-27. Shimizu, S., Tanaka, K. and Imai, |., 1953: Kamiashibetsu. Explanatory Text of the Geological Map of Japan, 1: 50000, 78p. (in Japanese) + 21 p. (resume in English). Geological Survey of Japan. Wright, C. W. and Kennedy, W. J., 1996: The Ammonoidea of the Lower Chalk, part 5. Monograph of the Palaeontographical Society, London, no. 601, p. 320- 403, pls. 95-124. Paleontological Research, vol. 5, no. 3, pp. 177-191, September 28, 2001 © by the Palaeontological Society of Japan Small Permian dicynodonts from India SANGHAMITRA RAY Geological Studies Unit, Indian Statistical Institute, 203 B. T. Road, Calcutta 700 035, India (email: sray @samuseum.ac.za) Received 17 July 2000; Revised manuscript accepted 6 June 2001 Abstract. The Lower Gondwana Kundaram Formation of the Pranhita-Godavari valley records the sole occurrence of Permian amniotes in India. The horizon has yielded various dicynodonts, mainly represented by medium-sized Endothiodon. This assemblage also contains several small dicynodonts belonging to the family Pristerodontidae and Emydopidae. Pristerodon (P. mackayi Huxley, 1868), Emydops (E. platyceps Broom and Haughton, 1917) and Cistecephalus (C. microrhinus Owen, 1876) are described here. This is the first detailed description of these genera from outside Africa. The older name Emydops in place of Emydoses is retained and the Indian specimens of Pristerodon, Emydops and Cistecephalus are compared with those from the Beaufort Group, Karoo Supergroup of South Africa. Based onits vertebrate fauna, the Kundaram Formation is broadly correlated with the Tropidostoma and Cistecephalus Assemblage Zones of the Beaufort Group, Karoo Supergroup, South Africa, the basal beds of the Madumabisa Mudstones of Zambia, the Ruhuhu and the lower part of the Kawinga Formation of Tanzania and the Morro Pelado Member of the Rio do Rasto Formation of Brazil. It suggests a Late Permian Tatarian age for the Kundaram Formation. The distribution of the Kundaram dicynodonts in the other Gondwanan countries indi- cates the close proximity of the continents during that period and a lack of endemism or provinci- ality. Key words: Dicynodont, Gondwana, Kundaram, Pranhita-Godavari valley Introduction Permian dicynodonts have been reported from the Kundaram Formation, a Lower Gondwana horizon of the Pranhita-Godavari valley, one of the several Gondwana ba- sins in India (Kutty, 1972; Ray, 1997). The formation is un- derlain by the coal-bearing Barakar Formation and overlain by the sand-dominant Kamthi Formation (Table 1). The flu- vial sediments of the Kundaram Formation comprise red mudstone, sandstone, sandstone-mudstone alternations and ferruginous shale (Ray, 1997). The extensive red mudstone ground of the Kundaram Formation contains abundant fossils of Permian dicynodonts, which have been collected from the two locali- ties near Golet (Figure 1) in the northwestern part of the Pranhita-Godavari valley (Kutty, 1972). Most of the speci- mens were encrusted with a hard iron matrix, resulting in the masking of the original shapes and forming oblate and spherical nodules. These were collected in situ as isolated skulls with and without lower jaws and other cranial frag- ments. The separated skulls and lower jaws are mainly preserved with their dorsal sides up. Those skulls with as- sociated lower jaws are found lying on their sides with their lateral sides up. Postcranial elements are relatively rare though a few in the form of rolled vertebrae and broken limb ends are present and show signs of rolling, abrasion and rounding. Fossil material prepared mechanically with a dental vibrotool reveals the preponderance of medium-sized Endothiodon (superfamily Endothiodontoidea). There are at present two species of Endothiodon, E. uniseries and E. mahalanobisi (Ray, 2000). The former has a skull length (SL) around 300 mm while in the latter it is around 160 mm. In addition, the assemblage contains some very small dicynodonts (SL 50 mm approx.) characterised by a broad intertemporal bar relative to the interorbital region. The aim of this paper is to describe the small and varied dicynodonts of the Kundaram Formation. These dicynodonts are known mainly from Africa and those mentioned here are the first forms from outside Africa to be described in detail. The paper also discusses’ the biostratigraphic and palaeobiogeographic implications of this unique fauna. Systematic palaeontology Infraorder Dicynodontia Owen, 1859 Superfamily Pristerodontoidea Cluver and King, 1983 Family Pristerodontidae King, 1988 Genus Pristerodon Huxley, 1868 178 Sanghamitra Ray Table 1. Lower Gondwana succession of the Pranhita-Godavari valley, India. Formations Main lithologies Fossils Age Sandstone and : Permo- i ? nodont N kein siltstone diey Triassic Kund ee d dicynodonts, Late undaram sancstoneran captorhinid Permian ferruginous shale Sandstone, Glossopteris Early to Barakar carbonaceous Late flora 2 shale and coal Permian : Tillite, greenish Early valealı shale, sandstone Permian Type species. — Pristerodon mackayi Huxley, 1868 (sub- sequent designation by Keyser, 1993). Pristerodon mackayi Huxley, 1868 Figures 2A-E, 3-4 Pristerodon mackayi Huxley, 1868, p. 204-205, pl. 12; King, 1988, p. 113; Keyser, 1993, p. 47 (see for prior synonymies). Holotype.—BMNH R1810, skull and lower jaw from East Deccan Trap a) Upper Gondwana Lower Gondwana Precambrian basement [A ] Fossil locality Figure 1. ties. Inset: Major Gondwana basins of India. London, Cape Province, South Africa; Assemblage Zone, Late Permian. Diagnosis.— Small dicynodonts with or without maxillary tusks; broad intertemporal region; wide parietal exposure; palatine large, leaf-like; postcanine teeth in an oblique, anteriorly converging row; long interpterygoidal vacuity ex- tending to the rear of the vomer; median interpterygoid ridge continues anteriorly on the ventral surface of the anterior pterygoid process; deep dentary sulcus, prominent lateral dentary shelf (Cluver and King, 1983; King, 1988; Keyser, 1993). Material. — SIR 209, anterior part of a laterally com- pressed skull and lower jaw; ISIR 369, anterior part of skull; ISIR 370, distorted skull with lower jaw, ISIR 372, occiput. Repository.—The specimens are housed in the Geology Museum, Indian Statistical Institute, Calcutta. Locality and horizon.—Near Golet, Pranhita-Godavari val- ley, India; Kundaram Formation, Late Permian. Description.—The Indian material includes a well pre- served but laterally compressed, small, anterior half of a skull with associated lower jaw (ISIR 209). Its total length measured along the dorsal midline is inferred to be about 50.6 mm. The morphology of the skull and lower jaw fol- lows the typical dicynodont pattern and the description of in- dividual bones is not repeated here. Cistecephalus 19°00’ Godavari R. Geological map of the Pranhita-Godavari valley, India (after Kutty et al., 1987) showing the fossil locali- Permian dicynodonts from India 179 Figure 2. AE. Pristerodon mackayi Huxley, 1868. A-D.ISIR 209. Partial skull with attached lower jaw in A, dorsal, B, ventral, C, right lateral, D, left lateral views. x1.1. E. ISIR 372. Partial occiput in posterior view. x1.3. F-H. Emydops platyceps Broom and Haughton, 1917. ISIR 208. Skull and lower jaw in F, dorsal, G, ventral, H, right lateral views. x1. 1-J. Cistecephalus microrhinus Owen 1876. ISIR 210. Partial skull and lower jaw in I, dorsal view. x1.3. J, left lateral view. x0.8. 180 Sanghamitra Ray Pmx dx in Kae Lit | 15 | ln N vi | I \ \ \ les | NT | i! Figure 3. Pristerodon mackayi Huxley, 1868. ISIR 209. Restored partial skull and lower jaw in A, dorsal, B, ven- tral and C, lateral views. Figure 4. Pristerodon mackayi Huxley, 1868. ISIR 369. Anterior part of skull in ventral view. Scale bar represents 10 mm. Hatched lines indicate broken surfaces. Scale bar represents 10 mm. Skull Snout and skull roof. The narrow and tapering snout is composed of the completely fused premaxillae, which con- tinue posteriorly to form a wedge between the external nares. The nares open near the extremity of the snout. Small, subrounded septomaxilla, recessed within the naris, forms its posteroventral margin. The maxilla occupies the anterolateral sides of the skull and bears large caniniform tusks and about 3-4 postcanine teeth. The preorbital length (measured from the tip of the snout to the anterior end of orbit) is 16.6 mm. It is covered by the elongated, paired nasals mostly, followed by the frontals posteriorly. Only the anterior part of the orbit is preserved, well defined by a nar- row rim. The preserved part of the interorbital region is broad (9 mm), flat and formed by the relatively extensive frontal. Anterolaterally the orbital rim consists of the subtriangular prefrontal, which is rather large in comparison to the more ventrally placed subrounded lacrimal and slen- der jugal. The lacrimal bears a prominent foramen just Permian dicynodonts from India 181 flush with the orbital rim. Palate. Palatal features are studied from ISIR 369 and ISIR 372 along with ISIR 209 as in the latter the lower jaw is in position. The anteriormost premaxilla forms a sharp pe- ripheral rim and posteriorly is in sutural contact with the vomer medially and palatine and maxilla laterally. Posteromedial to the caniniform tusk in ISIR 209 or to the subcircular alveolus in ISIR 369, the maxilla bears a uniserial, short tooth row, tending to converge anteriorly. Though teeth are not preserved in ISIR 369, the apertures of the alveoli are confluent and form a short, shallow groove. The margin of this groove is raised above the surface of the maxilla. The palatines in ISIR 369 are broad, leaf-shaped, bearing undulations and forming the lateral margin of the choanal slits. The anterior pterygoid rami have sharp ven- tral edges (ISIR 209). In ISIR 372, the parasphenoid- basisphenoid complex as in other dicynodonts is fused to the posterior end of the pterygoidal plate. The basiphenoid tubera are separated by a deep median cleft. Two distinct ridges run along the anterior surface of the tubera while their faces are laterally oriented, concave and consist of the fora- men ovalis. In ISIR 209, the cultriform process of the parasphenoid extends as a slender rostrum between the interpterygoid vacuity. Anteriorly the sphenethmoid com- plex stands in a groove on the dorsal surface of the cultriform process. The epipterygoid is L-shaped with a short anterior and longer posterior quadrate ramus. The quadrate- quadratojugal complex is typical of dicynodonts. Occipital and otic regions. In ISIR 372, the occiput is subrectangular in shape and is flanked on either side by the squamosal. The occipital condyle is situated medially al- most near its ventral margin. Above the condyle is situated an elongate foramen magnum. A major portion of the occiput is formed by the large, medially placed supraoccipital ventrally and interparietal dorsally. Laterally the supraoccipital is in sutural contact with the tabulars and ventrolaterally with the rodlike opisthotic. This latter suture is interrupted by a distinct post-temporal fenestra. The opisthotic forms the ventral margin of the occiput. Laterally on either side of the condyle is a pair of jugular foramen, piercing the exoccipitals. Lower jaw The portion of the lower jaw anterior to the Meckelian fenestra is preserved in ISIR 209. The relationships of the various elements of the lower jaw follow the normal dicynodont pattern. The anterior dentary symphyseal end is narrow, slender and forms a cutting edge. Though the dorsal surface is hardly visible as the lower jaw is attached to the skull, a deep but short, longitudinal dentary sulcus is discerned, which is for occlusion with the upper jaw teeth. Laterally the jaw ramus bears a distinct and high dentary shelf just above and anterodorsal to the Meckelian fenestra, which is quite long and elliptical. The dentary extends up to the posterodorsal end of the fenestra while the angular forms its ventral margin. The subrounded reflected lamina of the angular extends well below the ventral margin of the lower jaw. A small, elongated splenial medially forms the anteroventral margin of the lower jaw. The anterior end of the rodlike prearticular is preserved and in sutural contact with the splenial. Discussion.—An imperfect ‘lacertilian’ skull collected by G. Mackay from East London, South Africa was originally described by Huxley (1868) as Pristerodon mackayi. It was a nearly complete skull with a posteriorly widening intertemporal bar. The skull was considered by Seeley (1895) to be an endothiodont because of its postcanine teeth. Many diverse dicynodonts bearing little or no resem- blance to each other except for the postcanine teeth were traditionally placed under Endothiodontidae. Later works by Van Hoepen (1934) and Cluver and King (1983) led to the placement of Pristerodon and its related forms within the family Pristerodontidae. King and Rubidge (1993) consid- ered Pristerodon to be characterised by a _ broad intertemporal bar with exposed parietals, large, leaflike pala- tine, postcanine teeth in a short oblique row, long interpertygoid vacuity, deep dentary sulcus and a prominent lateral dentary shelf. All the Pristerodon species (P. mackayi, P. agilis, P. boonstrai, P. buffaloensis, P. vanhoepeni and P. whaitsi) were differentiated on the bases of the presence or absence of the maxillary tusk, nasal bosses and position of the alveolus (King, 1988). However, investigation of a large number of toothed dicynodonts earlier considered as endothiodont by Keyser (1993) revealed that the vast majority of the described spe- cies belonging to Pristerodon and various other genera are junior synonyms of Pristerodon mackayi, the only valid spe- cies of Pristerodon. He further suggested that the crista oesophagea forming ridges on the anterior pterygoid rami is a diagnostic feature of Pristerodon. On the other hand, King and Rubidge (1993) emphasised the sigmoidal curve of the anterior pterygoid ramus of Pristerodon. All the Indian specimens (ISIR 209, ISIR 369, ISIR 370, ISIR 372) are skulls of small dicynodonts with an average skull length of about 50 mm. These are characterised by caniniform tusks, wide intertemporal regions, short, oblique postcanine tooth row, large, leaflike palatines, high and dis- tinct lateral dentary shelf and deep dentary sulcus. All these features definitely show that these pertain to Pristerodon mackayi. Superfamily Diictodontoidea Cluver and King, 1983 Family Emydopidae Cluver and King, 1983 Subfamily Emydopinae Cluver and King, 1983 Genus Emydops Broom, 1912 Type species. — Emydops minor Broom, 1912 (subse- quent designation by Keyser, 1993). Emydops platyceps Broom and Haughton, 1917 Figures 2F-H, 5-6, 7E-F Emydops platyceps Broom and Haughton, 1917, p. 125: King, 1988, p. 116. Emydops tener Keyser, 1993, p. 49, fig. 5.1. Holotype.—SAM-PK-2667, skull from Dunedin, Beaufort West, South Africa; Cistecephalus Assemblage Zone, Late Permian. a r 1 Æ | ; ‘i Pf Ca | =) fy À (ER : 1} Wim Ai | 5 EN \ g\ : HN Figure 5. Emydops platyceps Broom and Haughton, 1917. ISIR 208. Restored skull and lower jaw in A, dorsal and B, ventral views. The stippled area indicates matrix covering. Scale bar represents 20 mm. Revised diagnosis.— Small dicynodonts with or without caniniform tusks; prominent lacrimal foramen; wide intertemporal region with parietal exposure; median premaxillary ridge on palate bordered by grooves on either side, irregularly placed maxillary and dentary teeth; small palatal embayment just anterior to caniniform process; flat, squarish palatine with notched medial and concave posterior margins; straight anterior pterygoid process, prominent lat- eral dentary shelf; dentary symphysis drawn up into a sharp cutting edge. Material.—\|SIR 208, a complete, slightly distorted skull Sanghamitra Ray Figure 6. Emydops platyceps Broom and Haughton, 1917. ISIR 208. Restored skull and lower jaw in A, lateral and B, occipital views. Scale bar represents 20 mm. with attached lower jaw. Repository.—The specimen is housed in the Geology Museum, Indian Statistical Institute, Calcutta. Locality and horizon.—The specimens were collected near Golet (Figure 1), Adilabad district, Andhra Pradesh, India from the Late Permian Kundaram Formation, Gondwana Supergroup. Description.— Skull General features. The small and triangular skull measures 47.8 mm along the dorsal midline. The snout is narrow, ta- pering anteriorly and quite short (preorbital length is 10 mm). Measurements of the skull are given in Table 2. The ellipti- cal nostril is situated close to the midline at the extremity of the snout. It is bordered by the premaxilla anterodorsally, nasals posterodorsally and the maxilla posteriorly and ven- trally. The orbit is relatively small, subrounded (diameter 10 mm approx.) and anterodorsally positioned. The interorbital region is flat, quite broad and about 15.5 mm. Beyond the orbit, the zygomatic arch flares out and meets the occipital plane at a high angle. The temporal fenestra is large, elon- gated and extended beyond the level of the occipital condyle. The intertemporal region is much wider than the Permian dicynodonts from India 183 Table 2. Measurements of the skull (ISIR 208) of Emydops platyceps. All measured in mm. Parameters Emydops platyceps (ISIR 208) Skull length a. Measured along the dorsal 47.8 midline b. Over squamosal wings 58.4 c. At palatal midline = Preorbital snout length 10 Postorbital snout length 25 Length from anterior edge of 37 premaxilla to anterior edge of pineal foramen Skull width across squamosal 44.5 Diameter of pineal foramen 2.8 Interorbital width 15.5 Intertemporal width 28 Snout width 16.7 Length of temporal fenestra 31.6 Width of temporal fenestra 14.3 Greatest width of occiput 41.3 Width of occipital condyle 13.8 Least squamosal width of the 28 occiput Occipital height 25.5 interorbital bar (Table 2) and gradually widens posteriorly. A small, circular pineal foramen is situated medially on a slightly raised area at the posterior end of the skull. The skull roof is relatively flat but gently sloping anteriorly. The occiput is trapezoid in shape with a large, elliptical occipital condyle situated medially near its ventral margin. Snout and skull roof. The anteriormost premaxilla sepa- rates the nostrils dorsally and forms a wedge-shaped con- tact with the paired nasals posteriorly. Posterolaterally it is in contact with the maxilla, a major element on the anterolateral sides of the skull. The maxilla borders the nasal openings ventrally and posteriorly. The septomaxilla is slightly exposed along the posteroventral border of the nasal cavity. In dorsal view, posterior to the premaxilla is a pair of large nasals. This is followed posteriorly by the fron- tal occupying most of the skull roof anterior to the temporal fenestra. Posterolaterally the nasal is bordered by a small elongated prefrontal. The latter, along with the relatively large, subrounded lacrimal, form the anterior margin of the orbit. There is a distinct lacrimal foramen. Dorsally and posterodorsally the circumorbital rim is formed by the frontal and a small, triangular postfrontal respectively. Ventrally the orbit is bordered by the jugal. The slender, rodlike post- orbital forms the narrow anteromedial border of the temporal fenestra. Characteristically the intertemporal region com- prises mostly the widely exposed parietals. Medially at the frontoparietal junction is a large, rhomboidal preparietal, which lies entirely in front of the pineal foramen. The circu- lar pineal foramen is situated on a slightly raised area, at the posterior end of the skull roof and is bounded by the parie- tals. Posterior to the pineal foramen is a single, large interparietal, which occupies a dorsomedial position on the occiput. The squamosal is the posteriormost element in dorsal view and divisible into three parts as is typical of dicynodonts. Attached to the anterior face of the squamosal is a small quadratojugal. Palate. The anterior part of the palate cannot be partly seen because of matrix covering and as the lower jaw is in position. Posteriorly the pterygoid bone is narrow with a poorly developed pterygoidal crest. The parasphenoid-basisphenoid complex is fused to the posterior end of the pterygoidal plate. The basisphenoid consists of two anteriorly converging tubera separated by a narrow and deep median cleft. The faces of the tubera are laterally oriented, concave and house the foramen ovalis. The quadrate is strongly fused with the more laterally placed quadratojugal, though there is deep groove between them. The palatal face of the quadrate, as in other dicynodonts, is composed of a broad, medial and a lateral condyle separated by a shallow groove. Lying between the medial face of the quadrate and the fenestra ovalis is a thin, long, rodlike, imperforate stapes with slightly expanded ends. Occipital and otic regions. In posterior view, the occiput is trapezoid in outline. It bears a prominent, elliptical occipital condyle medially, which is composed of the paired exoccipitals and the basioccipital. Above the condyle is an elongated, triangular foramen magnum. The dorsal margin of the foramen magnum is formed by the supraoccipital, which also forms the roof of the braincase. The interparietal, situated on the dorsal side of the supraoccipital, is characterised by a median ridge tapering ventrally. Ventrolateral to the condyle is a jugular foramen, piercing the exoccipital and the rodlike opisthotic, which ex- pand laterally overlapping the squamosal. A large post- temporal fenestra is present near the occipital condyle at the sutural contact between the opisthotic and the dorsally placed supraoccipital. Laterally the occiput is margined by the winglike flanges of the squamosal. The anterior face of the occiput bears a pair of small, flat prootics, which along with the opisthotics form the anterior and posterior walls, re- spectively of the otic capsule. Lower jaw The lower jaw is attached to the skull. The anterior end is relatively slender and is drawn up into a sharp cutting edge. The dentary symphysis is strongly fused. Laterally the jaw ramus bears a distinct, high dentary shelf and a large Meckelian fenestra. The anteriormost element of the lower jaw, the dentary, extends posteriorly as far as the posterior end of the Meckelian fenestra. It is bounded posteriorly by the surangular and posteroventrally by the angular. Presence or absence of teeth cannot be determined as the lower jaw is in position. The reflected lamina of the angular is quite small and is in line with the ventral margin of the lower jaw. The transversely widened posterodorsal surface of the articular forms lateral and medial condyles separated by a low ridge as found in the dicynodonts. It slopes down- ward posteriorly to form the retroarticular process. Discussion.— 184 Sanghamitra Ray On the genus Emydops A small dicynodont skull, about 45 mm in length, was first described by Broom (1912) from Kuilspoort, Beaufort West, South Africa as a new genus and species Emydops minor. It is tuskless with a wide intertemporal region, a large me- dian preparietal forming the anterior margin of the pineal fo- ramen, a slender postorbital arch and a feeble beak. Broom (1913) redefined Emydops as a small tuskless form with a few unserrated postcanine teeth. Subsequently, a number of Emydops species, collected from the Permian part of the Beaufort Group of South Africa, were described by Broom (1913, 1921). These species were distinguished based on the shapes and arrangements of the bones of the frontal and parietal regions. Broom and Haughton (1917) described another new species of Emydops, E. platyceps based on a tusked skull from Dunedin, Beaufort West, South Africa. Broom (1921) created a new genus Emydopsis (the type species is Emydopsis trigoniceps), characterised by the presence of only three or four posteriorly serrated teeth. Toerien (1953) stated that the number and size of the teeth alone cannot be used to differentiate between Emydops, Emydopsis and Pristerodon, then considered to be closely related to the former two genera. He further concluded that Emydops may be differentiated from Pristerodon on the basis of the size of the palatine and the absence of the palato-premaxillary contact in Pristerodon. The holotypes of the type species of Emydops, E. minor (AMNH 5525; Figure 7A) and Pristerodon, P. mackayi (BMNHR 1810; Figure 7B) were again examined by Cluver and King (1983). They stated that in both specimens, few characters of taxonomic importance are visible. They sup- plemented the generic diagnoses of Emydops and Pristerodon from the information accumulated from other species of the two genera. According to them, the charac- teristic features of Emydops include: small dicynodonts with wide intertemporal region and exposed parietals (Figure 7C), platelike palatine with concave posterior border, quite short interpterygoidal vacuity, presence of embayment in the palatal rim and weak interpterygoidal crest, prominent lateral dentary shelf, dentary symphysis drawn up into sharp cutting edge and shallow groove on the dorsal edge of the dentary. Keyser (1993) while reviewing the small dicynodonts of South Africa transferred most of the holotypes of Emydops species to Pristerodon mackayi. According to him, Emydops minor, the type species of Emydops, displays no distinctive features-a view also shared by Cluver and King (1983). Keyser (1993) found E. minor to be similar to Pristerodon mackayi and considered Emydops minor as nomen dubium. He suggested that E. platyceps is the only valid species, characterised by large and square palatines which are perforated by foramina. He renamed Emydops in part as Emydoses (Keyser, 1993, p. 48) and assigned two species to the genus, namely Emydoses tener (Figure 7D) and Emydoses platyceps (Emydops platyceps of Broom and Haughton, 1917; holotype SAM-PK-2667; Figure 7E). However, King and Rubidge (1993) considered Emydops to be well characterised. Emydops is differentiated from the other toothed dicynodonts (Eodicynodon, Pristerodon and Robertia), based on such features of the palate and lower Figure 7. Skulls in dorsal view. A. Emydops minor, holotype AMNH 5525 (after Cluver & King, 1983). B. Pristerodon mackayi, holotype BMNHR 1810 (after Cluver and King, 1983). C-F. Emydops platyceps, C, SAM-PK-11060 (after Cluver & King 1983); D, SAM-PK-K10170 (syntype, Emydoses tener of Keyser, 1993); E, holotype SAM-PK-2667, F, ISIR 208. Scale bars represent 10 mm. jaw as the size and shape of the palatine, arrangement of the postcanine teeth, lateral dentary shelf and dorsal surface of the lower jaw (King and Rubidge, 1993; p. 141, table 2). From the above review, it is evident that a disagreement persists regarding the nomenclature of the genus Emydops. Though Keyser (1993) in effect renamed Emydops as Emydoses because most of the earlier described species, including the type species of the formers, had in his view be- come junior synonyms of Pristerodon mackayi, the generic diagnosis remains nearly the same for Emydops and Emydoses. Moreover, Emydops is a long-accepted name in its accustomed meaning. Thus in the present study prior- ity is given to the older name of the genus and the name Emydops is retained, to provide stability and avoid confusion in the nomenclature by introducing a new name. On the species of Emydops As mentioned earlier Keyser (1993) considered E. Erratum In the article by Komatsu, Saito and Fürsich (Vol. 5, No. 2), the columnar section in the upper left of Figure 7 (page 128) was partly obliterated during the printing process. Remove the corrected columnar section below and affix it to the appropriate position. Limatula iwayae Entolium inequivalve XX À A Aa Phycosiphon isp. Palaeonucula makitoensis Spirophycus \sp. Palaeophycus isp. Inoceramus maedae Skolithos isp. Oxytoma tetoriense Spirophycus isp Modiolus maedae Pleuromya hidensis Tetorimya carinata Inoceramus maedae Phycosiphon isp. Pinna sp. aff. P. sandsfootensis Figure 7. Ecological reconstruction of the bivalve fauna in shelf deposits of the Mitarai Formation. Permian dicynodonts from India 185 Table 3. Comparative measurements of several specimens of Emydops. All measured inmm. Abbreviations used: SL, skull length along dorsal midline; SLsq, skull length over the squamosals, PSL, preorbital snout length; SnW, snout width, IO, interorbital width, IT, intertemporal width; TF, length of temporal fenestra; SW, skull width; OcH, occipital height; OcW, occipital width. Parameters Specimens SL SL sq PSL SnW IO IT IT/IO TF SW OcH OcW ISIR 208 47.8 58.4 10 16.7 15.5 28 1.81 31.6 44.5 25.5 41.3 SAM-PK-2667 40.58 51.9 9.75 15.68 10.69 15.69 1.48 - 34.54 - SAM-PK-10170 49.33 61.36 7.97 17 10.52 19.88 1.89 32.9 47.46 18.35 39.58 SAM-PK-10148 51.06 58.72 16.26 16.28 10.96 18.38 1.68 30.2 42.88 23.66 35.34 SAM-PK-K1671 30.38 39.37 7.58 12.34 4.9 9.8 2 20.55 29.1 15.74 21.95 SAM-PK-3721 44 54.1 - 12.15 11.2 15.85 1.42 29.44 - 18.89 30.4 SAM-PK-10172 40.16 46.03 11.34 10.33 8.11 14.8 1.82 33.3 - SAM-PK-11060 41.23 47.32 11.13 - 12 15.86 1.32 21 28.96 20.38 27.78 SAM-PK-K1517 46.69 56.64 11.58 - 15.38 19.77 1183 17.5 30.4 22.03 30.6 SAM-PK-K5974 56.2 65.5 - - 14.95 22.63 1.51 35.94 43.83 27 48.8 SAM-PK-K6693 47.94 59.56 12.33 16.37 12.08 18.54 1.53 25.7 44.4 18.85 33.22 SAM-PK-K6623 46.03 54.85 12.21 16.98 13.52 16.55 1.22 30.46 53.88 24.5 33.31 platyceps Broom and Haughton, 1917 and E. tener Keyser, 1993 as the only valid species. The former was characterised by large, squarish palatines, which are perfo- rated by foramina and the latter by its “slender’ build (Keyser 1993). The use of features like slender or delicate skull to define species is subjective (King, 1993) and avoided in the present study. A close examination of Emydops specimens housed at the South African Museum, Cape Town, including the holotype SAM-PK-2667 of E. platyceps and the syntypes (SAM-PK-10148 and SAM-PK-10170) of E. tener reveal that the shape of the palatines are similar in all the specimens. The palatal portion of the palatine is flat, squarish and bears a notch or palatine foramen in its medial margin. Its posterior margin is concave. Although the area between the medial margin of the palatine and the vomer along the ventral midline is covered with matrix in most of the specimens, the presence of the notch can be clearly dis- cerned, especially in SAM-PK-10148, SAM-PK-3721, SAM-PK-K1671, SAM-PK-11060 and SAM-PK-K6623. Moreover, it appears that the syntypes of E. tener do not have any feature different from E. platyceps Broom and Haughton, 1917. It is considered here as the junior syno- nym of E. platyceps Broom, 1912. Thus, from the speci- mens available for study, it appears that the genus Emydops has only one valid species, E. platyceps and is now distin- guished by the generic features of Emydops: small dicynodonts which may be tusked or tuskless, prominent lacrimal foramen flush with the orbit, wide intertemporal re- gion with broad parietal exposure, irregularly placed maxil- lary and dentary teeth, small embayment on the palatal rim anterior to the caniniform process, premaxillary ridge bor- dered by grooves on either side, flat, squarish palatine with notched medial and concave posterior margins, straight an- terior pterygoid process, dentary symphysis drawn up into a sharp cutting edge and a prominent lateral dentary shelf. Comparison between the Indian and South African forms ISIR 208 (Figure 7F) is a small skull (47.8 mm) with broad intertemporal region and widely exposed parietal. The pterygoid bridge posterior to the choanae, though not well preserved, is quite narrow (Figure 5B). The lateral dentary shelf is very distinct and high and the dentary symphysis is drawn up into a sharp cutting edge. Thus, it is assigned to the genus Emydops. The anterior palatal features are not visible because of the position of the lower jaw. Table 3 gives a detailed comparison of ISIR 208 with a number of South African forms, including the holotype of E. platyceps (SAM-PK-2667), based on different cranial parameters. It shows that the overall skull proportions of ISIR 208 such as length, width, occipital height, occipital width and length of the temporal fenestra fall within the range of the South African forms. On the other hand, the snout length is much shorter while the interorbital and intertemporal width with re- spect to the skull length is much greater than that of the SAM specimens. IT/IO ratio (1.8) though again within the range, which varies from 1.22 (SAM-PK-K6623) and 2 (SAM-PK-3721), is at the higher end of the range. The interorbital (IO) and intertemporal (IT) width relative to the skull length and IT/IO ratio are found to be not reliable spe- cific characters (Keyser, 1975; King, 1993) and are not con- sidered here. However, in ISIR 208 the pineal foramen is situated near the end of the intertemporal bar. The preparietal lies entirely in front of the pineal foramen and does not form its anterior margin (Figure 7F). Though this feature is not found in any other Emydops specimens and is unique to ISIR 208, more specimens with this feature need to be discovered before it can be considered as a reliable specific character. Apart from this, ISIR 208 bears overall similarity with E. platyceps and is placed within Emydops platyceps. 186 Sanghamitra Ray Subfamily Cistecephalinae Broom, 1903 Genus Cistecephalus Owen, 1859 Type species. — Cistecephalus microrhinus Owen, 1876 (subsequent designation by King, 1988). Cistecephalus microrhinus Owen, 1876 Figures 21-J, 8-10, 11A-B Cistecephalus microrhinus Owen, 1876, p. 63, pl. 64, fig. 4-7: King, 1988, p.118, fig. 33 (see for prior synonymies). Holotype. —BMNH R 47066, an imperfect skull from Stylkraans, Graaff-Reinet, Cape Province, South Africa; Cistecephalus Assemblage Zone, Late Permian. Diagnosis.—Small, toothless emydopids with broad or narrow intertemporal region; lacrimal foramen, postfrontal and preparietal absent; pterygoid meeting below parabasisphenoid complex; interpterygoidal vacuity absent; stapes perforated or deeply incised; prominent lateral Figure 8. Cistecephalus microrhinus Owen, 1876. ISIR 210. Partial skull with lower jaw in A, dorsal and B, lateral views. Scale bar represents 20 mm. Figure 9. Cistecephalus microrhinus Owen, 1876. ISIR 366. Anterior part of skull in ventral view. Scale bar repre- sents 10 mm. Figure 10. Cistecephalus microrhinus Owen, 1876. ISIR 367. Anterior part of lower jaw in dorsal view. Scale bar rep- resents 10 mm. dentary shelf (Keyser, 1973; King, 1988). Material.—\SIR 210, anterior portion of a skull with at- tached lower jaw, lacking the posterior part of the zygomatic arch, squamosals, occiput and postdentary bones, ISIR 365, a laterally compressed skull with attached lower jaw, ISIR 366, left portion of skull, ISIR 367, snout region, ISIR 368, anterior part of a lower jaw. Repository.—The specimens are housed in the Geology Museum, Indian Statistical Institute, Calcutta. Locality and horizon.—The specimens were collected near Golet (Figure 1), Adilabad district, Andhra Pradesh, India from the Late Permian Kundaram Formation, Gondwana Supergroup. Description.— Skull ISIR 210 is a small, triangular skull with a slight lateral and anteroposterior distortion. Its length along the dorsal midline from the anterior end of the premaxilla to the poste- rior end of the pineal foramen is 41 mm while the total length is inferred to be about 52 mm. Different measurements of ISIR 210 are given in Table 4. Its snout is short, broad and tapers anteriorly with the nostrils situated close to the midline and separated by a large, swollen and wedge- shaped premaxilla. The maxilla occupies the anterolateral sides of the skull. The septomaxilla is completely recessed within the nostril. The orbits are circular, relatively small, anterodorsally placed and separated by a wide interorbital Permian dicynodonts from India 187 Skulls in dorsal and lateral views; A-B, A, after Broili and Schroder, 1935; Figure 11. Cistecephalus microrhinus. B, ISIR 210; C, Cistecephaloides boonstrai (after Cluver, 1974a); D, Kawingasaurus fossilis (after Cox, 1972). Scale bars represent 10 mm. region. This region consists of large, paired nasals anteriorly and frontals posteriorly. The anterior part of the circumorbital rim is formed by the large, elongated prefrontal and rectangular lacrimal. The postfrontal is absent. The intertemporal region widens considerably (31 mm approx.) especially at the posterior end of the skull. A small, circular pineal foramen is situated at the far end of the skull roof. The paired parietals constituting the intertemporal bar are broad, widely exposed and laterally bordered by the slightly raised but narrow postorbital. The postorbital is separated from the prefrontal by the frontal. The preparietal is absent. Table 4. Measurements of the skull (ISIR 210) of Cistecephalus microrhinus. Asterix (*) indicates inferred measurements. All measured in mm. Cistecephalus microrhinus Parameters (ISIR 210) Skull length 52° Preorbital snout length 1725 Postorbital snout length 23 Length from anterior edge of 41 premaxilla to posterior edge of pineal foramen. Diameter of the pineal foramen 2 Interorbital width 28.5 Intertemporal width 31 Snout width 27.5 Beyond the pineal foramen, the posterior part of the skull and the zygomatic arches are broken. In ISIR 210, the slender jugal is completely overlapped by the squamosal; the latter reaches the maxilla because of antero-posterior compression. The usual Cistecephalus feature of maxilla and squamosal separated by the jugal is preserved in ISIR 365. The palate of the specimen ISIR 210 cannot be studied as the lower jaw is in position and at- tached to the skull. The anterior part of the palate is studied from the specimens ISIR 365 and ISIR 367. It is edentulous and consists of a sharp palatal rim formed anteriorly by the premaxilla and posterolaterally by the maxilla. The pala- tines are very small and curved posteriorly. A narrow vomerine septum separates the very small internal nostrils. Lower jaw The lower jaw is described from the specimens ISIR 210, ISIR 365 and ISIR 368. It is short, robust and deep. The dentaries are completely fused at the symphysis and form sharp, transverse cutting edge anteriorly. Posterior to the cutting edge, the dorsal surface of the dentary is slightly raised and further posteriorly it bears a pair of ridges. Posteriorly the lower jaw is flared out laterally. Above the Meckelian fenestra is present a distinct lateral dentary shelf. The posterior ends of the specimens and the postdentary bones are not preserved in the specimens ISIR 210 and ISIR 367. In ISIR 210, the lower jaw is attached to the pal- ate showing that the latter is much wider than the symphyseal region of the lower jaw. Discussion. — The subfamily Cistecephalinae contains small, toothless emydopids with very broad intertemporal re- gion lacking the postfrontal and preparietal (King, 1988). Other characteristic features of this subfamily include perfo- rated or deeply incised stapes, vestigial or no interpterygoid vacuity, reduced palatine, premaxilla extended far back posteriorly, anterior edge of the dentary symphysis forming a sharp cutting edge and a prominent lateral dentary shelf. This subfamily is composed of three genera, Cistecephalus Owen, 1876 (Figures 11A-B), Cistecepha- loides Cluver, 1974a (Figure 11C) and Kawingasaurus Cox, 1972 (Figure 11D). The cranial and postcranial morphology 188 Sanghamitra Ray Table 5. Distinguishing features of Cistecephalus, Cistecephaloides and Kawingasaurus (sources: Broili and Schroder, 1935; Cox, 1972; Cluver, 1974a; King, 1988). Cistecephaloides Kawingasaurus Parameters Cistecephalus Snout Short and broad Orbits Large, anterolaterally placed orbits May be broad or narrow Absent or present low down within the orbit Prefrontal separated from postorbital by frontal Relatively slender Circular, situated at the far end of the intertemporal bar Interorbital region Lacrimal foramen Relation between prefrontal, frontal and postorbital Postorbital Pineal foramen Squamosal May be separated from maxilla by jugal Otic region Normal Short and broad Flattened, laterally expanded Small Small Broad Broad Large Large Prefrontal meeting postorbital Prefrontal separated from post- orbital by frontal Relatively slender Absent Very robust Very small, insignificant Separated from maxilla by Reaches maxilla jugal Normal Highly inflated of these taxa have been studied in detail (Seeley, 1894; Broom, 1932, 1948; Broili and Schroder, 1935; Keyser, 1973 and Cluver, 1974a, b, 1978) and show that the features like the broad, triangular skull with wide interorbital and intertemporal regions, rounded occiput and absence of the interpterygoidal vacuity are of a highly specialised animal with fossorial habits. However, Cistecephaloides differ from Cistecephalus in having a very high skull roof, sloping anteriorly and with the prefrontal in sutural contact with a ro- bust postorbital, while Kawingasaurus is distinguished by the absence of the pineal foramen and an inflated otic region. The other distinctive features of Cistecephalus are given in Table 5. The Indian specimens exhibit a short snout, circular orbit, absence of the postfrontal, preparietal and the lacrimal fora- men, frontal separating the postorbital and prefrontal, wide intertemporal region, circular pineal foramen, transverse cutting edge of the dentary and prominent lateral dentary shelf (Figure 11B). These features clearly indicate that the specimens belong to the genus Cistecephalus. A large number of Cistecephalus species were originally erected, distinguished by parameters such as their size dif- ferences, broad or narrow skull, and variations in the ar- rangement of the skull roof bones (Owen, 1876; Broom, 1932, 1948). All the fossils were collected from the Permian part of the Beaufort Group of South Africa. Keyser (1973) suggested that Cistecephalus species are members of a growth series and synonymised all the species with C. microrhinus, the latter being the only valid species of the genus. The Indian Cistecephalus is compared with the South African forms (SAM-PK-K6814, SAM-PK-K7667, SAM-PK-K7852, SAM-PK-K8304 and SAM-PK-10665) collected from the Late Permian part of the Beaufort Group of the Karoo Supergroup and housed in the South African Museum, Cape Town (Table 6). The total skull lengths of the African specimens studied vary between 42 mm and 63 mm. The skull length of ISIR 210 and ISIR 365 (Table 6) falls well within that range. The intertorbital width of the African specimens varies between 10 and 18 mm and that of Table 6. Comparative measurements of several specimens of Cistecephalus. All measured in mm. Index to the abbreviations is given in Table 3. Parameters Specimen SL SW 1O IT ITAO SAM-PK-K6814 54.38 59.06 16.88 39.38 2.33 SAM-PK-K7667 63 70 17 25 1.47 SAM-PK-K7852 42 37 10 25 2.5 SAM-PK-10665 48.46 4269 11.54 32.31 2.8 SAM-PK-K8304 55 62 18 45 2.5 ISIR 210 52* = 28.5 31 1.1 ISIR 365 46.4 = 18.2 23 1.2 “inferred ISIR 365 is 18.2 mm. The specimen ISIR 210 shows a marked increase in interorbital width (about 28 mm) because of antero-posterior compression. However, in all other as- pects, the Indian specimens bear an overall similarity with the African forms. Concluding remarks The Permian in India is very poorly represented by verte- brate fossils. Apart from some palaeoniscoid fishes and temnospondyl amphibians from other Gondwana basins (Werneburg and Schneider, 1996), the Kundaram verte- brates record the sole occurrence of the Permian amniotes in India. Studies have shown that the fauna is largely repre- sented by the two species of Endothiodon (Ray, 2000). The present work further strengthens this fauna with the addition of three more genera, Pristerodon (P. mackayi), Emydops (E. platyceps) and Cistecephalus (C. microrhinus). King (1992) reported the presence of Oudenodon. The only non- dicynodont member is a captorhinid (Kutty, 1972). Although the study of the Kundaram fauna is far from com- pletion, it is worthwhile to mention some important aspects Permian dicynodonts from India 189 of the fauna. 1. The most complete vertebrate record of the Late Permian period is found in the lower part of the highly fossiliferous Beaufort Group of the Karoo Supergroup, South Africa and is subdivided into six biozones. The Kundaram fauna bears a remarkably close similarity to that of the Beaufort Group of South Africa. Pristerodon has a wide range covering all the five Permian biozones of the Beaufort Group except for the Eodicynodon Assemblage Zone (Rubidge, 1995), and hence is not useful for precise correla- tion. Endothiodon first appears in the Pristerognathus Assemblage Zone but predominates in the Tropidostoma Assemblage Zone. In this latter zone, Cistecephalus occurs very infrequently and Emydops makes its first ap- pearance (Figure 12). In contrast, Endothiodon persists as a rare fossil while Cistecephalus becomes abundant in the succeeding Cistecephalus Assemblage Zone. This zone also records the first appearance of Oudenodon. However, the Kundaram fauna shows a preponderance of Endothiodon amounting to about thirty individuals with four or five partial skulls of Cistecephalus and Emydops. The dominance of Endothiodon followed by Emydops and Cistecephalus in the Kundaram fauna indicates a broad cor- relation with the Tropidostoma and Cistecephalus Assemblage Zones of the Beaufort Group of South Africa. The Kundaram Formation is also correlated with the basal beds of the Madumabisa Mudstones of Zambia, the Ruhuhu and lower part of the Kawinga Formation of Tanzania and the Morro Pelado Member of the Rio do Rasto Formation of mackayi (SL ca. 50.6 mm), Emydops sp. (SL ca. 47.8) and Cistecephalus microrhinus (SL ca. 50 mm) are also small. This smallness of size is also reflected in the captorhinid (SL ca. 50 mm). The dominance of the small forms in the Kundaram fauna is comparable with that of the Cistecephalus Assemblage Zone. In this zone, more than 70% of the total faunal as- semblage is composed of small forms, in marked contrast to that of the underlying Tropidostoma Assemblage Zone. The latter zone is characterised mainly by medium to large dicynodonts such as Rhachiocephalus (Rubidge, 1995). There are too many unknown parameters, to say with confi- dence what might have caused this size differentiation. It may be due to preservational bias, transportational sorting or palaeoclimatic and palaeogeographic influences and ne- cessitates further study of the Permian Kundaram fauna. 3. The distribution of Kundaram dicynodonts, Endothio- don, Oudenodon, Pristerodon, Emydops and Cistecephalus, in the now widely separated geographic areas (Table 7) sug- gests that there was no apparent physical barrier between these regions. Moreover, the Pangean distribution of these dicynodont-bearing regions shows a broad and regular zone, extending from Brazil in the west to India in the east (Ray, 1999). It indicates the close proximity of the conti- nents during that time and a lack of endemism or provincial- ity among these genera. Table 7. Distribution of the five dicynodont genera (after Anderson and Cruikshank, 1978; King, 1992; Ray, 1999). Brazil. It suggests a Late Permian Tatarian age for the Mal T Kundaram Formation. South Africa India a AN Zambia Bes Brazil 2. Another distinctive feature of the Kundaram vertebrate gay nee es fauna is the small size of its individual members. Pristerodon + Endothiodon shows two distinct clusters of skull size. E. Endothiodon + + 4: mahalanobisi has an average SL of about 160 mm and is Emydops a much smaller than the other known Endothiodon species, Cistecephalus + while that of E. uniseries is about 350 mm. Other Or dicynodonts of the Kundaram Formation like Pristerodon Peer ea 5 x 5 Pristerodon Endothiodon Emydops Cistecephalus Oudenodon Eodicynodon Tapinocephalus Pristerognathus Tropidostoma Cistecephalus Dicynodon ASSEMBLAGE ZONES Figure 12. Ranges of the Kundaram dicynodont genera present in the Beaufort Group, Karoo Supergroup, South Africa (after Rubidge, 1995). 190 Sanghamitra Ray Acknowledgements The author sincerely thanks Dr. S. Bandyopadhyay, Indian Statistical Institute, for guidance, support and reading the manuscript critically. Thanks are due to Prof. T.-S. Kutty, Indian Statistical Institute, Calcutta, and Dr. M. Cluver, South African Museum, Cape Town for permission to study the Indian and Karoo fossil collection respectively, Dr. B. Rubidge, BPI for Palaeontological Research, Johannesburg, for help throughout the research work and Mr. A. Das for il- lustrations. The valuable suggestions of the reviewers are gratefully acknowledged. The Indian Statistical Institute, Calcutta, provided the financial support and infrastructure. References Anderson, J. M. and Cruickshank, A. R. I., 1978: The biostratigraphy of the Permian and Triassic. Part 5: A re- view of the classification and distribution of Permo- Triassic tetrapods. Palaeontologia Africana, vol. 21, p. 15-44. Broili, F. and Schroder, J., 1935: Beobachtungen an Wirbeltieren der Karooformation. VI. Über den Schader von Cistecephalus Owen. Sitzungsberichte der Bayeri- schen Akademie der Wissenschaften, vol. 1935, p. 1-20. Broom, R., 1903: On the classification of the theriodonts and their allies. Report of the South African Association for the Advancement of Science, vol. 1, p. 286-295. Broom, R., 1912: On some new fossil reptiles from the Permian and Triassic beds of South Africa. Proceedings of Zoological Society of London, vol. 1912, p. 859-876. Broom, R., 1913: On some new genera and species of dicynodont reptiles with notes on a few others. Bulletin of American Museum of Natural History, vol. 32, p. 441- 457. Broom, R., 1921: On some new genera and species of anomodont reptiles from the Karoo beds of South Africa: Proceedings of Zoological Society of London, vol. 1921, p. 647-674. Broom, R., 1932: The Mammal-like Reptiles of South Africa and the Origin of Mammals. 376 p. H. F. and G. Witherby, London. Broom, R., 1948: A contribution to our knowledge of the verte- brates of the Karoo beds of South Africa. Transactions of the Royal Society of Edinburgh, vol. 61, p. 577-629. Broom, R. and Haughton, S. H., 1917: Some new species of Anomodontia (Reptilia). Annals of the South African Museum, vol. 12, no. 5, p. 119-125. Cluver, M. A., 1974a: The skull and mandible of a new cistecephalid dicynodont. Annals of the South African Museum, vol. 64, p. 137-155. Cluver, M. A., 1974b: The cranial morphology of the Lower Triassic dicynodont Myosaurus gracilis. Annals of the South African Museum, vol. 66, p. 35-54. Cluver, M. A., 1978: The skeleton of the mammal-like reptile Cistecephalus with evidence of a fossorial mode of life. Annals of the South African Museum, vol. 76, no. 5, p. 213-246. Cluver, M. A. and King, G. M., 1983: A reassessment of the re- lationships of Permian Dicynodontia (Reptilia, Therapsida) and a new classification of dicynodonts. Annals of the South African Museum, vol. 91, no. 3, p. 195-273. Cox, C. B., 1972: A new digging dicynodont from the Upper Permian of Tanzania. In, Joysey, K. A. and Kemp, T. S. eds., Studies in Vertebrate Evolution. p. 173-189. Oliver and Boyd, Edinburgh. Huxley, T. H., 1868: On Saurosternon bainii and Pristerodon mackayi, two new fossil lacertilian reptiles from South Africa. Geological Magazine, vol. 5, p. 201-205. Keyser, A. W., 1973: A preliminary study of the type area of the Cistecephalus zone and the revision of the family Cistecephalidae. Memoir of the Geological Survey of Republic of South Africa, vol. 62, p. 1-71. Keyser, A. W., 1975: A re-evaluation of the cranial morphology and systematics of some tuskless Anomodontia. Memoir of the Geological Survey of South Africa, vol. 67, p. 1- 110. Keyser, A. W., 1993: A re-evaluation of the smaller Endothiodontidae. Memoir of Geological Survey of South Africa, vol. 82, p. 1-53. King, G. M., 1988: Anomodontia. /n, Wellnhofer P., ed., Encyclopedia of Paleoherpetology, vol. 17C, p. 1-174. Gustav Fischer Verlag, Stuttgart. King, G. M., 1992: The palaeobiogeography of Permian anomodonts. Terra Nova, vol. 4, p. 633-640. King, G. M., 1993: How many species of Diictodon were there? Annals of the South African Museum, vol. 102, no. 9, p. 303-325. King, G. M. and Rubidge, B. S., 1993: A taxonomic revision of small dicynodonts with postcanine teeth. Zoological Journal of the Linnean Society, vol. 107, p. 131-154. Kutty, T. S., 1972: Permian reptilian fauna from India. Nature, vol. 237, p. 462-463. Kutty, T. S., Jain, S. L. and RoyChowdhury, T. 1987: Gond- wana sequence of the Northern Pranhita-Godavari valley: its stratigraphy and vertebrate faunas. Palaeobotanist, vol. 36, p. 214-229. Owen, R., 1859: On the orders of fossil and recent Reptilia and their distribution in time. Report of the British Association for the Advancement of Science, vol. 1859, p.153-166. Owen, R., 1876: Descriptive and Illustrative Catalogue of the Fossil Reptilia of South Africa in the Collection of British Museum (Natural History). 88 p. Taylor and Francis, London. Ray, S., 1997: Some contributions to the Lower Gondwana stratigraphy of the Pranhita-Godavari valley, Deccan India. Journal of the Geological Society of India, vol. 50, no. 5, p. 633-640. Ray, S., 1999: Permian reptilian fauna from the Kundaram Formation, Pranhita-godavari Valley, India. Journal of African Earth Sciences, vol. 29, no. 1, p. 211-218. Ray, S., 2000: Endothiodont dicynodonts from the Late Permian Kundaram Formation, India. Palaeontology, vol. 43, no. 2, p. 375-404. Rubidge, B. S., 1995: Biostratigraphy of the Beaufort Group. South African Commission for Stratigraphy, Biostrati- graphic Series 1, p. 1-45. Seeley, H. G., 1894: Researches on the structure, organisa- tion and classification of the fossil Reptilia. Part IX, sec- tion 1. On the Therosuchia. Philosophical Transactions of the Royal Society, Series B, vol. 185, p. 987-1018. Seeley, H. G., 1895: Researches on the structure, organisation and classification of the fossil Reptilia. Part IX, section 6. Associated remains of two small skeletons Permian dicynodonts from India from Klipfontein, Fraserburg. Philosophical Transactions Dicynodontidae na aanleiding van nuwe vorme. of the Royal Society, Series B, vol.186, p. 149-162. Palaeontologiese Navorsing van die Nasionale Museum, Toerien, M. J., 1953: Evolution of the palate in some Bloemfontein, vol. 2, p. 67-101. anomodonts and its classificatory significance. Werneburg, R. and Schneider, J. S., 1996: The Permian Palaeontologia Africana, vol. 1, p. 49-117. temnospondyle amphibians of India. Special Papers in Van Hoepen, E. C. N., 1934: Oor die indeling van die Palaeontology, vol. 52, p. 105-128. Appendix Institutional abbreviations AMNH, American Museum of Natural History, New York; BMNH, British Museum (Natural History), London; ISI, Indian Statistical Institute, Calcutta; SAM, South African Museum, Cape Town. Anatomical abbreviations AlV Alveolus Pal Palatine Ang Angular Pf Pineal foramen Ar Articular Pmx Premaxilla Bo Basioccipital Po Postorbital Bs Basisphenoid Pof Postfrontal D Dentary Pp Preparietal Eo Excoceipital Pr Prootic Fr Frontal Prf Prefrontal Fm Foramen magnum Pt Pterygoid Ip Interparietal Ptf Post-temporal fenestra Ipt.v Interpterygoidal vacuity Q Quadrate J Jugal Qj Quadratojugal Jf Jugular foramen RI Reflected lamina E Lacrimal Sph Sphenethmoid complex Lds Lateral dentary shelf St Stapes Lf Lacrimal foramen Smx Septomaxilla Mx = Maxilla So Supraoccipital Mf Meckelian fenestra Sp Splenial Na Nasal Sq Squamosal Op Opisthotic V Vomer P Parietal 191 Paleontological Research, vol. 5, no. 3, pp. 193-200, September 28, 2001 © by the Palaeontological Society of Japan Quantification of optically granular texture of benthic foraminiferal walls RITSUO NOMURA Foraminiferal Laboratory, Faculty of Education, Shimane University, Matsue, 690-8504, Japan (e-mail: nomura@edu.shimane-u.ac.jp) Received 31 August 2000; Revised manuscript accepted 11 June 2001 Abstract. Three main textures may occur in optically granular walls of hyaline calcareous foraminifera: mosaic granular, jagged granular, and minute granular. The size and shape of the op- tical granules within them indicates that these wall textures are intimately related to the crystalline arrangement of the units and their elements, and also to the wall thicknesses of the foraminiferal tests. and walls are thick. correspond to the minute-granular texture. Highly complex minute-granular textures are observed if the foraminiferal tests are large In general, crystallographically compound and intermediate wall structures Both formsize (ratio of perimeter to area) and Shannon-Wiener index for polarized crystal units explain these different wall textures well. This study suggests a method for quantification of wall textures based on image processing. Key words: benthic foraminifera, crystal unit, ecology, optical textures, test walls Introduction Hyaline calcareous walls of benthic foraminiferal tests consist of small crystallites and their assembled crystal units. Hansen (1968, 1970) clarified these crystalline struc- tures by scanning electron microscope studies, and in the 1970s several authors examined these foraminiferal test structures in diverse foraminiferal taxa (e.g., Banner and Williams, 1973; Stapleton, 1973; Bellemo, 1974a, b; Conger et al., 1977). Features of the crystalline structures in test walls are revealed by high interference colors under polariz- ing microscopy. Wood (1949) introduced the terms radial and granular structures for these optical features of foraminiferal walls. Nomura (1983, 1988) further recog- nized variations in each optical texture, and subdivided granular structure into mosaic, jagged, and minute (Figure 1.1-1.3), and radial textures into distinct and indistinct. These subdivisions of the granular walls are based on the optical grain size and the structure. Although a clear-cut distinction between them is sometimes difficult, the mosaic granular has larger and less jagged appearances than the jagged one. Optical grains of the minute granular are con- spicuously small and complicated in comparison with the mosaic and jagged ones. These optical textures clearly re- flect the complexity of crystalline structures consisting of various optical axes of the crystal units and their elements (Nomura, 1983). The optical textures of foraminiferal walls have mainly been utilized for systematic purposes. Loeblich and Tappan (1964, 1974, 1987) used optical features of foraminiferal walls for their hierarchical classification. This classification now needs to be reexamined in view of in- creased knowledge. Apart from its application to foraminiferal systematics, wall texture can be used to assist in interpretation of foraminiferal ecology and paleoecology (Nomura, 1988, 1997). In a preliminary report (Nomura, 1997), | suggested that granular textures show variations corresponding to the preferred ecology of individual species. The best example is found in the ecological difference be- tween epifaunal and infaunal species. Mosaic granular tex- ture is mainly found in infaunal taxa, and minute granular texture is seen in epifaunal taxa (Nomura, 1997). It is em- pirically understood that the crystal units of foraminiferal tests show variations in their perimeter and area in polarized light. As there are gradual changes among the mosaic, jag- ged, and minute granular textures, however, application of these optical textures to ecology and paleoecology is not de- finitive. Information on the ecological and ontogenetic char- acters of the wall textures is still limited. In order to clarify the optical grains of these textures by quantitative analyses, | examined live and dead specimens having different textures and different growth stages. Observations of the wall texture using a polarizing micro- scope are particularly useful on account of the simple meth- odology employed. Definition of analytical methods is needed however to perform reliable comparisons of foraminiferal wall textures. 194 Ritsuo Nomura KT Te Benthic foraminiferal wall texture 195 Table 1. Species examined in this study. taxa test size (mm) wall thickness (um) depth inm mad) condition Anomalinoides glabratus (Cushman) 0.24-0.56 2.5-15.0 54(HK le) dead Cassidulina reniforme (Norvang) 0.14-0.20 1.0-2.5 194(HN3-9°) dead Chilostomella oolina Schwager 0.38-0.49 1.0-3.8 Pliocene lioka Formation, Choshi °° fossil Cibicides lobatulus (Walker and Jacob) 0.38-0.78 6.8-18.2 54(HK-1°) dead Cibicides refulgens Montfort 0.22-0.71 4.5125 54(HK-1') dead Cibicidoides pseudoungerianus (Cushman) 0.56-0.83 8.0-11.3 99(HK-4°) dead Cibicidoides wuellerstorfi (Schwager) 0.23-0.72 1.5-20.0 99(HK-4°) dead Elphidium advenum (Cushman) 0.20-0.62 2.0-12.5 54(HK-1°) live, dead Fursenkoina pauciloculata (Brady) 0.29-0.83 1.3-6.2 54(HK-1°) live, dead Globocassidulina oriangulata Belford 0.17-0.33 2.0-5.0 99(HK-4°) dead Gyroidina orbicularis d'Orbigny 0.20-0.49 2.5-14.0 99(HK-4°) dead Gyroidinoides nipponicus (Ishizaki) 0.22-0.37 3.8-4.0 54(HK-1') dead Heterolepa subhaidingeri (Parr) 0.40-0.86 6.3-19.5 99(HK-4°) live Nonionellina labradorica (Dawson) 0.22-0.39 1.0-4.7 150(CB4-1°) live Nonion manpukuziensis Otuka 0.27-0.66 2.5-7.5 54(HK-1') dead Oridorsalis umbonatus (Reuss) 0.18-0.46 1.0-4.3 150(CB4-1°) dead Pullenia bulloides d'Orbigny 0.16-0.32 2.8-5.0 150(CB4-1°) dead Paracassidulina neocarinata (Thalmann) 0.206-0.32 2.2-5.5 99(HK-4°) dead * KT-90-15, Tansei-maru Cruise, off Shimane and Yamaguchi Prefectures, Sea of Japan (Ocean Research Institute, Univ. of Tokyo) "Well preserved Methods piece. Because this method is subjective, sometimes se- lection errors can be made, especially when the unit is not To avoid such The last chambers of live and well preserved dead speci- mens of 18 foraminiferal species were analyzed (Table 1). Foraminiferal tests were first embedded in glycerin jelly and covered with a thin glass cover slip as in standard prepara- tion for microscope observation. Tests were crushed and fragments of the final chamber walls were arranged carefully by pressing the glass under a binocular microscope while the jelly was liquid enough to allow the wall pieces to move. Observations and measurements of the crystal units were carried out under a polarizing microscope at a magnification of x400. Measurements of the wall thickness were made on final wall fragments set vertically on the glass at the mag- nification of x1000, after wall texture photography. Crystal units were observed most effectively using the first-order in- terference colors arising from insertion of a gypsum plate. The image analysis was carried out using Winroof (version 3.5.2; Mitani Corporation, 2000), which runs on Windows computers. The observations were made at an angle of 45° to the optically positive or negative orientations of the crystal units. Two methods were used to quantify the texture image. Firstly the perimeters and areas of manually se- lected crystal units were measured to calculate the ratio of perimeter to area (A/P ratio or formsize) (Nomura, 1997). Ten to twenty crystal units were measured for each wall @ Figure 1. Variations of optically granular wall texture. clearly differentiated from neighboring units. selection errors, | applied a second method that detects crystal units after color processing which disintegrates the original color image into RGB (red, green, and blue). Crystal units are more effectively distinguished in the G (green) image at specific threshold values (Figure 2). Thresholding is a brightness discrimination, which selects pixels belonging to features of interest (Russ, 1990). Possible values range from 0 to 255. A block model of the green image, in which the peaks correspond to the bright- ness intensities, is shown in Figure 2.2. Selection of the crystal unit areas is thus critically controlled by the threshold values. Various threshold values were examined to find the best texture images. Statistically, pixel brightness has a characteristic frequency distribution for each texture, and usually shows a normal distribution (Figure 2.4). The fol- lowing formula was used to determine the threshold value for each specimen examined: Threshold value = Average threshold value + Standard deviation. Between 100 and 500 areas of selected crystal units were counted for each specimen. The selected unit images were subsequently converted to binary images (Figure 2.3) and their areas, perimeters, and formsizes then calculated. These measurements were 1. Mosaic-granular texture of Chilostomella ovoidea. Scale bar = 50 pm. 2. Jagged-granular texture of Elphidium advenum. Scale bar = 50 um. 3. Minute-granular texture of Cibicidoides pseudoungerianus. Scale bar = 50 um. 4a, 4b. Horizontal section of a small Heterolepa subhaidingeri and close-up of the final chamber wall showing the minute-granular texture. final chamber wall showing indistinct crystal unit boundaries. Scale bar: 4a, 200 um, 4b, 100 um. 5a, b. Horizontal section of a larger H. subhaidingeri and close-up of the Scale bar: 5a, 500 um, 5b, 100 um. 196 Ritsuo Nomura Relative frequency of pixels 0.7 Average = 117.14 Standard deviation = 55.06 Threshold 1 0.0 0 Brightness 172 255 Figure 2. Explanations for the image processing of Fursenkoina pauciloculata. 1. Green image of the texture separated from the blue and red images. 2. Block diagram of the green image. Thresholding is the brightness value used to distinguish particular images from others, ranging from 0 to 255. Dotted horizontal lines indicate the threshold value (172) in this analysis. 3. Binary image of the crystal unit areas at threshold value 172. 4. Histogram showing the relative frequency of pixel brightness (0-255). The averaged bright- ness is 117.14 and the standard deviation is 55.06. Thresholding at 172 (sum of the average and the standard deviation) accounts for 20.35% of the selected texture. based on the binary images at threshold values of 130-240. The formsize of each crystal unit is calculated by the for- mula: Formsize = 2-(Area)/(Perimeter). Values are 21. If the formsize is 1, the crystal unit is perfectly circular and its radius is 1. The A/P ratio (Nomura, 1997) is a simple expression of this formsize. The areas of the selected crystal units show a wide varia- tion between 1 to 2000s pixels. Statistical values with high standard deviation make the comparison of the formsize un- reliable. However, both the number of the selected areas and the number of pixels they contain represent the differ- ence between the textures, so that they conform to the con- cept of ecological heterogeneity that accounts for the amount of order or disorder in any given part of the wall. The Shannon-Wiener information function (H’) is herein ap- plied to evaluate the diversity of the textures: H' ~~) (Pi)(logPi) where N is the total number of the crystal units selected and Pi is the proportion in the i th-selected area to the total areas selected. Higher values of H’ indicate the textures are char- acterized by a more complex crystalline arrangement, whereas lower values represent textures consisting of more simple arrangements. It is difficult to measure the thicknesses of fixed parts of the walls, because breakage occurs randomly during crush- ing. Analysis was limited to flat pieces of final chamber walls. Sutural areas consist of complicated crystalline structures showing interwoven crystal units and elements. Such areas are not suitable for this analysis. Wall thickness is proportional to test size, and so increases in individuals with growth, even though it varies between foraminiferal species. Thus, careful selection of wall fragments is neces- sary if reliable results are to be obtained. Benthic foraminiferal wall texture 197 Results EZA Selected areas + . 160 160 The smaller specimens examined here (maximum diame- ter 0.15-0.25 mm) usually have final chamber walls between __ 140 140 1.0-5.0 um thick. However, mature specimens of species = 120 120 such as Chilostomella ovoidea, Nonionellina labradorica, = us and Cassidulina reniforme may also have thin walls (< 5.0 7 100 100 2 um). Large specimens (0.4-0.9 mm diameter) of species = 80 80 = such as Heterolepa subhaidingeri show a wide range of wall 2 = thickness (6.3-19.5 um; Table 1). Wall thickness differs be- = 60 60 m tween taxa, and appears to be reflected in wall texture. > 40 40 Thin-walled specimens show well defined boundaries be- < tween crystal units displaying distinct blue, red, and yellow 20 20 areas, but thicker specimens have indistinct boundaries, and 0 0 blue and red areas are much reduced. These color ! à final penultimate antepenultimate changes are caused by the interference order of polarizing light, because internal refraction of incident light occurs in every crystal element in the unit and at the unit boundary. Thin-walled crystal units present first-order interference Figure 3. Results of averaged areas with standard devia- tions for the last three chambers of a sectioned Oridorsalis umbonatus. Threshold value is 130. Increased areas in the color, but thicker walls containing assembled crystal units antepenultimate chamber are caused by indistinct boundaries produce multiple interference. Brightness of pale yellow im- between the crystal units. f: final chamber. p: penultimate. a: ages thus increases with increasing wall thickness. antepenultimate. Change of optical texture in relation to the wall thickness can also be seen within individuals as they grow. As ob- served in Cibicidoides pseudoungerianus tests of differing 5 N o of N 0 N Ÿ so ° où 5 a ah oo er AP Ad ch aot aS” av? 0 o © RN TP ae gh SERIES NER o ie oe $ Sp N d » DICH: IR Se RN) RS ty A S 2 QO CAO ZEN, N Ÿ ad. ae Ÿ SN A0 pa D 0 NP AS gO OL où Saad anh g Hah N DE FLE ROME USE QE CSSS a EI > = IE EEE Oh Ae Poe 0” < ,© ae À © © " Oo. Ns (oy À ow 0 \ V x 40 0" of C ow Pe BO EWE Wd hori ata Cr igen ee NSO SEES (OU 3:9 mosaic granular 3.0 jagged 2.5 a granular minute 2.0 granular ys Figure 4. Average formsize in each species. Many species have a wide variation in formsize, which is related to the different textures. Mosaic-granular texture is typified by formsize of > 2.8; formsize of minute-granular textures are < 2.4; and values for jagged-granular texture lie between 2.4 and 2.8. Hatched boxes enclose 50% of the formsizes and the tops and bottoms of the box mark =25%. Thick horizontal line indicates the median. Small circle is an exceptional value. 198 Ritsuo Nomura size (Figure 1.4, 1.5), unit boundaries of crystal units in the final chamber wall can be easily distinguished. In thicker walls, higher interference makes the boundaries less clear (Figure 1.5b). As noted above, the yellowish color in the antepenultimate chamber is caused by higher-order interfer- ence colors. The variations in average areas of the se- lected crystal units and the brightness in the walls of the last three chambers of Oridorsalis umbonatus are shown in Figure 3. The average area of the crystal units in the ante- penultimate chamber walls is four to five times larger than that in the walls of the final and the penultimate chambers. Areal increase in the antepenultimate chamber walls is clearly related to the brightness, which makes the unit boundary indistinct. Clear discrimination of the crystal units is possible in the final chamber, where wall thickness is usu- ally < 3-4 um. Based on the formsize, mosaic-granular texture occurs in Chilostomella ovoidea and many immature specimens (i.e., small specimens) of Cassidulina reniforme, Fursenkoina pauciloculata, Globocassidulina oriangulata , Gyroidinoides nipponicus, Gyroidina orbicularis, Nonion manpukuziensis and Nonionellina labradorica. This texture is recognized by formsizes of over 2.8 (Figure 4). The walls of Nonionellina labradorica show atypical mosaic-granular texture, where ei- ther the optically positive or negative conditions are domi- nant in the apertural face. Optical axes of the crystal elements are equally arranged over large areas, but are oblique to the test surface. This texture can also be seen in taxa having larger apertural faces, such as Nonion and Nonionella. Typical minute-granular texture is shown by most species of the genera Cibicidoides, Cibicides, and Heterolepa. This texture reflects the original complexity of their crystalline arrangement. In the Cibicidinae (Bellemo, 1974b, 1976), this is termed compound and the intermediate structure. Similar formsize is also seen in other mature specimens of Anomalinoides glabratus, E. advenum, G. oriangulata, G. nipponicus, G. orbicularis, O. umbonatus, Paracassidulina neocarinata and P. bulloides, except for Chilostomella ovoidea and Cassidulina reniforme. However, their crystalline structures differ slightly from those of the Cibicidinae in having larger crystal units and herring- bone structure (e.g., Nomura, 1983). Thus, the minute- granular texture is formed by the original complex crystalline structure and by an apparent feature of thick walls consisting of mosaic and jagged-granular textures. The boundary be- tween minute-granular and jagged-granular may be around a formsize of 2.4 (Figure 4). Jagged-granular texture is usually recognized between 2.4 and 2.8. These three wall textures show wide variations in the measured formsize values. In particular, thinner walls (< 5 mm) are characterized by high standard deviation values (Figure 5). Gradual changes between the different textures also occur. Excepting the Cibicidinae, most species show three differing textures according to the growth stages of the individual: mosaic-granular texture corresponds to the stage of new chamber formation or the younger growth stage of in- dividual foraminifera; jagged- and minute-granular textures correspond to the full-grown stages of individuals. A significant relationship is indicated between modified formsize (formsize divided by the square root of the number Standard deviation of formsize Wall thickness (um) Figure 5. Plots of standard deviation of formsize and wall thickness showing large variations in thinner test walls. of selected crystal units) and wall thickness (Figure 6.1). This relationship can be expressed as an exponential, with r=0.68. The formsize is divided by the square root of the number of crystal units because formsize is dependent on the number of selected areas. Mosaic granular textures are characterized by low numbers of selected crystal units and higher formsizes, whereas minute-granular textures have larger numbers of crystal units and lower formsize values. The results clearly indicate that larger formsizes have thin- ner walls, whereas specimens with smaller formsize values have thicker walls and/or originally smaller and complex crystal units. Shannon-Wiener information theory is the other quantitative expression to account for the heterogene- ity of selected units that consist of large and small areas. The result of this information function is opposite to the rela- tionship between formsize and wall thickness (Figure 6.2). It is thus negatively correlated with modified formsize at a statistically significant level (p < 0.001) (Figure 7). If the Shannon-Wiener information index is higher, then the modi- fied formsize is smaller, and textures are complex. Conversely, if the information index is lower, then modified formsize is higher and textures are simpler. As a result, distribution of respective wall textures on the formsize overlaps among different species, due to changes in the wall texture through growth. Little change in the wall texture is observed between the final and the preceding walls, as well as among different-sized specimens of thinly walled species such as Chilostomella ovoidea and Cassidulina reniforme. These species are characterized by having larger original crystal units and additional thin lami- nae in walls formed subsequently. Discussion and Conclusions Mosaic, jagged and minute granular optical wall textures result from the arrangement of crystal units and the ele- Benthic foraminiferal wall texture 199 Average formsize/\ 0.40 number of area l 0 3) 10 15 20 25 Wall thıckness (um) e A.glabratus © à Creniforme 8&8 © C. ovoidea 2 x C.lobatulus _ + C. pseudoungerianus a C refulgens E. advenum Figure 6. is here divided by the square root of the number of the area. species examined show a positive exponential relationship. Average formsize/, number of area 0.40 y = 0.73-0.09x R=0.78 0.35 0.30 0.25 0.20 0.15 0.10 0.05 4049990 95.5246:0.66:3: 0» 75, 8.0 Shannon-Wiener Index (H') C. wuellerstorfi F. pauciloculata Shannon-Wiener Index (H') > 8.0 y = 5.25 * xA(0.09) R= 0.61 0 5 10 Is) 20 25 Wall thickness (um) A G.oriangulata © G. nipponicus Oo P. neocarinata G. orbicularis > P. bulloides S FH. subhaidingeri & N.labradorica | A N. manpukuziensis O. umbonatus O 4 1. Plots of average formsize and wall thickness of the species, showing a negative exponential relationship. Formsize 2. Plots of the Shannon-Wiener index (H') and the wall thickness of the ments within any wall thickness. Mosaic-granular texture is formed by larger crystal units and thinner walls, and was once named “clumpy crystalline structure” (Nomura, 1983). Jagged-granular texture is correlated with “intricate crystal- line structure” (Nomura, 1983). Minute-granular texture is formed by two types of crystalline structures: 1) intricate crystalline structures within thicker walls, and 2) complex ar- rangement of crystal elements such as the compound and intermediate structures of Bellemo (1974b, 1976). Ratios of the perimeter to the area of the selected crystal unit have been introduced as a method of quantitatively discriminating these wall textures (Nomura, 1997). However, initially this method used manual selection of crystal units and thereby sometimes produced errors. Criteria for the selection of crystal units are needed. The present study confirms that the intimate relationships between optical texture and crys- @ Figure 7. Plot of average formsize and Shannon-Wiener index (H’) showing a negative relationship with a statistically sig- nificant correlation coefficient (r=0.78). Formsize is here di- vided by the square root ofthe number ofthe area. Symbols as in Figure 5. 200 Ritsuo Nomura talline structure can be recognized in walls showing first- order interference colors. Even in this case, image processing is required to overcome individual variations. Several adjoining crystal units may apparently form large single units in polarizing light. Such units must be elimi- nated to make realistic measurements and comparisons. The thresholding proposed is a simple method of discrimi- nating various texture images. Classification of optically granular texture in hyaline cal- careous foraminifera (Nomura, 1988, 1997) is not only a species character, but is also related to the wall thickness of the foraminiferal test and the complexity of crystalline struc- tures. In general, thinner walls show mosaic-granular tex- ture, whereas thicker walls and complex crystalline structures (compound and intermediate) exhibit minute- granular texture. Jagged-granular texture is present in walls of intermediate and moderate thickness. To evaluate these optical textures, the relationships between formsizes of the crystal units were examined for differing growth stages of foraminiferal individuals of selected species. The results suggest that the formsize of the crystal units shows a grad- ual change in accordance with the crystalline complexity of the test walls in different foraminiferal growth stages. The relationship between formsize and the wall thickness is sta- tistically significant and exponential. Shannon-Wiener infor- mation theory is applicable for quantification of the textures, and the Shannon-Wiener index is negatively correlated with the modified formsize parameter. Acknowledgments | am grateful to Martin Buzas of Smithsonian Institution and Pratul Saraswati of the Indian Institute of Technology for their constructive comments on an earlier version of this paper. | thank Bruce Hayward of Auckland Museum and Barry Roser of Shimane University for the reading of this manuscript. John Murray of Southampton Oceanography Centre reviewed this paper. References Banner, F. T. and Williams, E., 1973: Test structure, organic skeleton and extrathalamous cytoplasm of Ammonia Brünnich. Journal of Foraminiferal Research, vol. 3, p. 49-69, pls. 1-10. Bellemo, S., 1974a: Ultrastructures in Recent radial and granular calcareous foraminifera. Bulletin of the Geologi- cal Institute of the University of Uppsala, N. S., vol. 6, p. 117-122, pls. 1-6. Bellemo, S., 1974b: The compound and intermediate wall structures in Cibicidinae (Foraminifera) with remarks on the radial and granular wall structures. Bulletin of the Geological Institute of the University of Uppsala, N. S., vol. 6, p. 1-11, pls. 1-9. Bellemo, S., 1976: Wall ultrastructure in the foraminifer Cibicides floridanus (Cushman). Micropaleontology, vol. 22, p. 352-362 Conger, S. D., Green Il, H. W. and Lipps, J. H., 1977: Test ultrastructure of some calcareous foraminifera. Journal of Foraminiferal Research, vol. 7, p. 278-296, pls. 1-9. Hansen, H. J., 1968: X-ray diffractometer investigations of a radiate and a granulate foraminifera. Bulletin of the Geological Society of Denmark, vol. 18, p. 345-348 Hansen, H. J., 1970: Electron-microscopical studies on the ultrastructures of some perforate calcitic radiate and granulate foraminifera. Det Kongelige Danske Videnskabernes Selskab, Biologiske Skrifter, vol. 17, no. 2, p. 1-16, pls. 1-26. Loeblich, A. R., Jr. and Tappan, H., 1964: Sarcodina chiefly “thecamoebians” and Foraminiferida, vol. 1 and 2. /n, Moore, R. C. ed., Treatise on Invertebrate Paleontology, Protista 2 Part C. The Geological Society of America and the University of Kansas Press, p. 1c-900c. Loeblich, A. R., Jr. and Tappan, H., 1974: Recent advances in the classification of the Foraminiferida. /n, Hedley, R. H. and Adams, C. G. eds., Foraminifera, no. 1, p. 1-53, Academic Press, New York. Loeblich, A. R., Jr. and Tappan, H., 1987: Foraminiferal Genera and Their Classification, 970 p., 847 pls. Van Nostrand Reinhold Company, New York. Mitani Corporation, 2000: WinRoof, version 3.5.2. Nomura, R., 1983: Cassidulinidae (Foraminiferida) from the uppermost Cenozoic of Japan (Part 1). Science Report of Tohoku University, 2nd Series (Geology), vol. 53, p. 1-101. Nomura, R., 1988: Ecological significance of wall microstruc- ture of benthic foraminifera in the southwestern Sea of Japan. Revue de Paléobiologie, Special Volume 2, p. 859-871. Nomura, R., 1997: Application of optical structure of foraminiferal test walls to analyze the ecology and paleoecology. Kaseki (Fossils), no. 62, p. 1-14. (in Japanese with English abstract) Russ, J. C., 1990: Computer-Assisted Microscopy. The Measurement and Analysis of Image, 453 p. Plenum Press, London. Stapleton, R. P., 1973: Ultrastructure of tests of some Recent benthic hyaline foraminifera. Palaeontographica, Abt. A, vol. 142, p. 16-49, pls. 1-25. Wood, A., 1949: The structure of the wall of the test in the foraminifera: Its value in classification. Quarterly Journal of the Geological Society of London, vol. 104, p. 229-255. Paleontological Research, vol. 5, no. 3, pp. 201-213, September 28, 2001 © by the Palaeontological Society of Japan Origin of the Ceratitida (Ammonoidea) inferred from the early internal shell features YASUNARI SHIGETA', YURI D. ZAKHAROV’ and ROYAL H. MAPES’ "Department of Geology and Paleontology, National Science Museum, 3-23-1 Hyakunincho, Shinjuku-ku, Tokyo, 169-0073 Japan (e-mail: shigeta@kahaku.go.jp) “Federal Far Eastern Geological Institute, Far Eastern Branch, Russian Academy of Sciences, Prospect Stoletiya Vladivostoka 159, 690022 Vladivostok, Russia (e-mail: yurizakh @ mail.ru) “Department of Geological Sciences, Ohio University, Athens, Ohio 45701, U.S.A. (e-mail: mapes @ oak.cats.ohiou.edu) Received 1 May 2001; Revised manuscript accepted 25 June 2001 Abstract. The early internal shell features in 40 species of the Goniatitida, Prolecanitida and Ceratitida are described on the basis of well-preserved specimens from the Carboniferous and the Permian of North America, England, Siberia and Urals. Seven morphotypes were recognized in the species examined by differences of the caecum shape (bottle-shaped, gourd-shaped, subelliptical, or elliptical), the proseptum length on the dorsal side (long or short), position of the second septum (close to proseptum or not) and initial position of the siphuncle (ventral, subcentral, or central). Paraceltites elegans, the oldest known representative of the Ceratitida, has a long proseptum on the dorsal side, a relatively small ammonitella angle, the second septum does not appear in close vicinity to proseptum, and the siphuncle is ventral. These features are essentially the same as those of the prolecanitid Daraelites elegans. This fact supports the hypothesis that the Ceratitida evolved from the Prolecanitida, probably Daraelites. Key words: Ceratitida, early internal shell features, Goniatitida, phylogeny, Prolecanitida Introduction The Ceratitida, which is the dominant ammonoid order of the early Mesozoic and one of the major orders of Ammonoidea, ranged from early Permian to the end of Triassic times, and has an almost worldwide distribution (Hewitt et al., 1993; Page, 1996). The origin of this order has been thought to be from a member of the Prolecantitida, because previous authors believed that both taxa shared a common lobe development (i.e., VU type of Ruzhencev, 1960, 1962 or U type of Schindewolf, 1934, 1953; see Smith, 1932; Spath, 1934; Spinosa et al., 1975; Shevyrev and Ermakova, 1979; Saunders and Work, 1997). Zakharov (1983, 1984, 1988), however, showed that the Prolecanitida (Medlicottida in Zakharov, 1983) and the Permian Ceratitida (Paraceltitina in Zakharov, 1984) do in- deed share the same lobe developmental type, (i.e., VLU type of Ruzhencev, 1960, 1962 or A type of Schindewolf, 1934, 1953), but one identical to that of the Goniatitida. He also pointed out the difficulty in determining the ancestor of the Ceratitida based on the lobe development patterns, be- cause all early to middle Permian ammonoids have the same lobe development pattern (Zakharov, 1984). After his works, no detailed observations of various shell characters have been done as a basis for discussion of the ancestor of the Ceratitida. Since Branco (1879, 1880), the ammonoid early internal shell features have been studied by many authors, and it has been determined that there are a number of common characters in the early shells of all ammonoids. States of these characters appear to be stable at suborder or superfamily levels (Druschits and Khiami, 1970; Druschits and Doguzhaeva, 1974, 1981; Tanabe et al., 1979; Tanabe and Ohtsuka, 1985; Ohtsuka, 1986; Landman et al., 1996). This fact suggests that the early internal shell features are strongly constrained phylogenetically, and therefore, it is possible to investigate the higher phylogenetic relationships within the Ammonoidea by analyzing these character state changes (Shigeta, 1989). As compared with Jurassic and Cretaceous ammonoids, Carboniferous and Permian ammonoids have been little studied for their early internal shell features. Most previous studies (Shul’ga-Nesterenko, 1926; Bohmers, 1936; Miller and Unklesbay, 1943; Bogoslovskaya, 1959; Zakharov, 202 Yasunari Shigeta et al. Figure 1. Diagrams of the internal shell structure (left) and measurements (right) of the early ammonoid shell in median section. The terminology is from Branco (1879, 1880), Grandjean (1910), and Drushchits and Khiami (1970). Abbreviations: am: ammonitella; c: caecum; ic: initial chamber; pc: primary constriction; ps: prosiphon; s: siphunclar tube; $1: proseptum (first septum); s2: primary septum (second septum); s3: third septum; A: maximum initial chamber size; B: minimum initial chamber size; D: ammonitella size; E: ammonitella angle. 1978) excluding Tanabe et al. (1994) and Landman et al. (1999) are based on optical microscopic observations. Detailed microstructural relationships of the morphologic features have received little examination. We have studied the early internal shell features of some Carboniferous and Permian ammonoids belonging to the Goniatitida, Prolecanitida and Ceratitida, by means of scan- ning electron microscopy. In this paper, we describe some of our observations and discuss the results of our analysis with special reference to the origin of the Ceratitida. Material and methods Five species of the Prolecanitida, 34 species of the Goniatitida and one species of the Ceratitida have been ex- amined (Appendix 1). Specimens of these ammonoids were collected from the Carboniferous and Permian strata of South Urals (Kazakhstan), Siberia (Russia), England and the U.S. mid-continent (Nevada and Texas). They include genera and species studied and figured by Tanabe et al. (1994). Higher categories of these genera and species were determined following the classification of Bogoslovskaya et al. (1999). Every specimen was cut and polished along the median plane. The polished surface was etched with 5% acetic acid for a few minutes; the etched surface was washed with distilled water, dried in air, and then coated with gold or plati- num using an ioncoater. The early internal features of each specimen were observed by means of a JEOL model JSM-5310 scanning electron microscope. Four characters: maximum initial chamber size, minimum initial chamber size, ammonitella size and ammonitella angle (= spiral length of ammonitella in degrees), were measured on the etched sur- face using a digital micrometer (accuracy +0.001 mm) at- tached to a Nikon model V16D profile projector. Figure 1 illustrates the terms used to describe the mor- phologic features of the early shell in median section. The terminology is based on Branco (1879, 1880), Grandjean (1910), and Drushchits and Khiami (1970) (See Landman et al., 1996, figure 1). The specimens observed are reposited at the University Museum, University of Tokyo (UMUT) for those described by Tanabe et al. (1994) and at the National Science Museum, Tokyo (NSM) for the remain- ing specimens. Observations Prolecanitida and Goniatitida The early whorls of the Carboniferous and Permian Prolecanitida and Goniatitida consist of initial chamber (protoconch), caecum, prosiphon, proseptum (first septum), septa, siphuncle, septal neck and outer shell wall, as in other Paleozoic and Mesozoic Ammonoidea. The maximum ini- tial chamber size in median section (A in Figure 1) ranges from 0.356 mm to 0.645 mm in the Prolecanitida and from 0.356 mm to 0.590 mm in the Goniatitida (Appendix 2). The ammonitella diameter (D in Figure 1) ranges from 0.702 mm to 1.250 mm in the Prolecanitida and from 0.660 mm to 1.048 mm in the Goniatitida (Appendix 1). The ammonitella angle (E in Figure 1) is generally small (328-355°) in the Prolecanitida and relatively large (352 - 385°) in the Goniatitida. The early internal shell features of the species examined can be classified into seven morphotypes; here named for the genera that best show each variation: Epicanites, Neopronorites, Daraelites, Goniatites, Maratho- nites, Agathiceras and Thalassoceras morphotypes (Figure Origin of the ceratitid ammonoid 203 Morphotype Goniatites Marathonites Thalassoceras tg Shape of caecum in median section Bottle-shaped Bottle-shaped Subelliptical Length of proseptum (dorsal side) Initial position of siphuncle Proseptum & 2nd septum (dorsal side) Separate (fairly) Separate (a little) Separate (a little) Subcentral Figure 2. Comparison of the early internal shell features in seven morphotypes of the Carboniferous and Permian ammonoids. Each morphotype is named for the genera that best show each variation. 2). There is no intermediate form between a pair of these internal shell feature morphotypes in our data base. All of the morphotypes have a circular initial chamber in median section and a short prosiphon. Epicanites morphotype.—In median section, caecum is elongate and subelliptical (bottle-shaped), without a con- spicuous constricted base at proseptum and second sep- tum; prosiphon is short and gently curved ventrally, and proseptum resting on dorsal side of initial chamber wall is long and strongly convex adapically. Second septum is convex adorally in median section, with a retrochoanitic septal neck, and is located far from proseptum. Siphuncle keeps ventral position throughout ontogeny. Akmilleria electaensis, Artioceras rhipaeum (Figure 3.5, 6) and Epicanites loeblichi (Figure 4.1, 2) possess the early in- ternal shell morphology of this morphotype. Early internal shell features of this morphotype have been reported in other Medlicottioidea (Shul’ga-Nesterenko, 1926; Böhmers, 1936; Miller and Unklesbay, 1943; Bogoslovskaya, 1959). Neopronorites morphotype.—Caecum is gourd-shaped, with a slightly constricted base at the proseptum, bulging part between proseptum and second septum, and gradual contracting part after second septum. Prosiphon is short, tube-like and straight. Proseptum resting on dorsal side of initial chamber wall is relatively long and slightly convex adorally in median section. Second septum is slightly con- cave adorally in median section, with a retrochoanitic septal neck, and is located relatively far from proseptum. Siphuncle is ventral throughout ontogeny. Neopronorites skvorzovi (Figure 3.3, 4) possesses the early internal shell morphology of this morphotype, as de- scribed by Zakharov (1986). A similar shaped caecum was described in Parapronorites cf. biformis by Shul’ga-Nestere nko (1926), hence she named it as a double caecum. Bohmers (1936), Miller and Unklesbay (1943) and Bogoslovskaya (1959) reported similar early internal shell features in other Pronoritoidea. Daraelites morphotype--Caecum is elongate and subellip- tical (bottle-shaped), without a conspicuous constricted base at proseptum and second septum. Proseptum resting on 204 Yasunari Shigeta et al. 2 x > ° 2 ME BSE LET EEA MEE ERS Figure 3. Median sections through the early whorls of the Permian prolecanitids. Over views of the early whorls showing the pri- mary constriction (pc) (1, 3, 5) and close-up of the prosiphon (ps), the caecum (c), the proseptum (s1), the second septum (s2) and third septum (s3) (2, 4, 6). Scale bars in 1, 3 and 5: 0.5 mm. Scale bars in 2, 4 and 6: 0.1 mm. 1, 2. Daraelites elegans Tchernow (Prolecanitoidea), Artinskian, South Urals (NSM PM16189). 3, 4. Neopronorites skvorzovi (Tchernow) (Pronoritoidea), Artinskian, South Urals (NSM PM16190). 5, 6. Artioceras rhipaeum (Ruzhencev) (Medlicottioidea), Artinskian, South Urals (NSM PM16192). Origin of the ceratitid ammonoid 205 i N u RS re — 1 ze co CE CO je a EE Figure 4. Median sections through the early whorls of the Carboniferous ammonoids. Overviews of the early whorls showing the primary constriction (pc) (1, 3, 5) and close-up of the prosiphon (ps), the caecum (c), the proseptum (s1), the second septum (s2) and third septum (s3) (2, 4, 6). Scale bars in 1, 3 and 5: 0.5 mm. Scale bars in 2, 4 and 6: 0.1 mm. 1,2. Epicanites loeblichi Miller & Furnish (Prolecanitida: Prolecanitoidea), Chesterian, Oklahoma (NSM PM16188). 3, 4. Girtyoceras meslerianum (Girty) (Goniatitida: Dimorphoceratoidea), Chesterian, Oklahoma (NSM PM16193). 5,6. Cravenoceras incisum (Hyatt) (Goniatitida, Neoglyphioceratoidea), | Chesterian, Texas (NSM PM16198). | TEE 206 Yasunari Shigeta et al. 2 EB: 2 INCRE NN UE DA ANG MOAT Figure 5. Median sections through the early whorls of the Permian goniatitids. Overviews of the early whorls showing the primary constriction (pc) (1, 3, 5) and close-up of the prosiphon (ps), the caecum (c), the proseptum (s1), the second septum (s2) and third sep- tum (s3) (2, 4, 6). Scale bars in 1, 3 and 5: 0.5 mm. Scale bars in 2, 4 and 6: 0.1 mm. 1, 2. Popanoceras annae Ruzhencev (Popanoceratoidea), Artinskian, South Urals (NSM PM16214). 3, 4. Marathonites invariabilis (Ruzhencev) (Marathonitoidea), Artinskian, South Urals (NSM PM16207). 5, 6. Uraloceras sp. (Neoicoceratoidea), Wolfcampian, Nevada (NSM PM16213). Origin of the ceratitid ammonoid 207 Figure 6. Median sections through the early whorls of the Permian goniatitids. Overviews of the early whorls showing the primary constriction (pc) (1, 3, 5) and close-up of the prosiphon (ps), the caecum (c), the proseptum (s1), the second septum (s2) and third sep- tum (s3) (2, 4, 6). Scale bars in 1, 3 and 5: 0.5 mm. Scale bars in 2, 4 and 6: 0.1 mm. 1, 2. Agathiceras uralicum (Karpinsky) (Goniatitoidea), Artinskian, South Urals (NSM PM16195). 3,4. Thalassoceras gemmellaroi Karpinsky (Thalassoceratoidea), Artinskian, South Urals (NSM PM16203). 5, 6. Crimites subkrotowi Ruzhencev (Adrianitoidea), Artinskian, South Urals (NSM PM16204). EEE EEE 208 Yasunari Shigeta et al. Figure 7. Median sections through the early whorls of the Permian and Triassic ceratitids. Overviews of the early whorls showing the primary constriction (pc) (1, 3) and close-up of the prosiphon (ps), the caecum (c), the proseptum (s1), the second septum (s2) and third septum (s3) (2, 4). Scale bars in 1 and 3: 0.5 mm. (Xenodiscoidea), Roadian, Texas (NSM PM16215). area, Idaho (NSM PM16216). dorsal side of initial chamber wall is long and slightly convex adapically in median section. Second septum is convex adorally in median section, with a retrochoanitic septal neck, and does not appear to be in close vicinity to proseptum. Siphuncle keeps a ventral position throughout ontogeny. Daraelites elegans possesses the early internal shell mor- phology of this morphotype (Figure 3.1, 2). Early internal shell features of this morphotype have been found in other species of Daraelites (Böhmers, 1936; Miller and Unklesbay, 1943). Goniatites morphotype.—In median section, caecum is subelliptical, without a conspicuous constricted base at proseptum and second septum; prosiphon is short and gen- tly curved ventrally, and proseptum on dorsal side is long and slightly convex adapically. Second septum is attached to proseptum on the dorsal side, forming a necklike structure in median section. Siphuncle keeps a ventral position throughout ontogeny. Scale bars in 2 and 4: 0.1 mm. 3, 4. Nordophiceras jacksoni (Hyatt & Smith) (Noritoidea), Spathian, Bear Lake 1, 2. Paraceltites elegans Girty Genera in the major superfamilies of the Carboniferous Goniatitida, including those in the Dimorphoceratoidea, Goniatitoidea, Neoglyphioceratoidea, Somoholitoidea and Gastrioceratoidea listed in Appendix 1, possess the early in- ternal shell morphology of this morphotype (Figure 4.3-6; Appendix 1). Our observations are consistent with the de- scriptions by previous authors (Böhmers, 1936; Miller and Unklesbay, 1943; Tanabe et al., 1994). Marathonites morphotype.—In median section, caecum is ellipsoid with a strongly constricted base at proseptum and second septum; prosiphon is short and gently curved ven- trally, and proseptum on dorsal side is short and convex adapically. Second septum is attached to proseptum on dorsal side, forming a necklike structure in median section. Siphuncle keeps a ventral position throughout ontogeny. Many superfamilies of the Permian Goniatitida, including the Adrianitoidea, Marathonitoidea, Neoicoceratoidea and Popanoceratoidea, possess the early internal shell morphol- Origin of the ceratitid ammonoid 209 ogy of this morphotype (Figures 5; 6.5, 6; Appendix 1). Additionally, our observations are consistent with the data of other authors (Shul’ga-Nesterenko, 1926; Böhmers, 1936; Miller and Unklesbay, 1943; Bogoslovskaya, 1959; Tanabe et al., 1994). Agathiceras morphotype.—In median section, caecum is ellipsoid with a strongly constricted base at proseptum and second septum; prosiphon is short and gently curved ven- trally, and proseptum on dorsal side is short and slightly con- vex adapically. Second septum is convex adorally, with a retrochoanitic septal neck, and is close to proseptum on dor- sal side, forming a necklike structure in median section. Siphuncle keeps a central position in first three whorls, and subsequently gradually shifts its position toward the venter. Migration of siphuncle to ventral marginal side is completed at end of fifth whorl. Two species of Agathiceras examined possess the early internal shell morphology of this morphotype (Figure 6.1, 2; Appendix 1). Schindewolf (1934) and Bohmers (1936) re- ported similar early internal shell features in other Permian Agathiceras. Thalassoceras morphotype.—In median section, caecum, which is preceded by short and curved prosiphon, is ellipsoid with a strongly constricted base at proseptum and second septum; proseptum on dorsal side is short, and second sep- tum is close to proseptum on dorsal side. Siphuncle occu- pies a central to subcentral position in first whorl, and subsequently shifts its position gradually to the venter in the early part of second whorl. Three taxa assigned to the Thalassoceratoidea, Bisatoceras sp., Eothalassoceras inexpectans and Thalas- soceras gemmellaroi, possess the early internal shell mor- phology of this morphotype (Figure 6.3, 4; Appendix 1). Ceratitida The initial chamber of Paraceltites elegans is circular in median section (Figure 7.1, 2). Although the caecum, prosiphon and siphuncular tube are not preserved in speci- men NSM PM16215, Spinosa et al. (1975, text-fig. 11) de- scribed an elongate and subelliptical caecum without a conspicuous constricted base at proseptum and one short prosiphon. The proseptum resting on the dorsal side of the initial chamber wall is long and slightly convex adapically in median section. The second septum does not appear in close vicinity to the proseptum, and the siphuncle maintains a ventral position throughout ontogeny. The maximum ini- tial chamber size, ammonitella size and ammonitella angle in NSM PM16215 are 0.463 mm, 0.921 mm and 342° re- spectively (Appendix 1). The early internal shell morphology of the early Triassic ceratitid Nordophiceras jacksoni (Figure 7.3, 4) is similar to those observed in Paraceltites elegans and Daraelites elegans except for the much smaller ammonitella angle (264°). Discussion Since the lobe development in the Prolecanitida has been thought to be identical with that in the Ceratitida, many authors have attributed the ancestor of the Ceratitida to the Prolecanitida (Spath, 1934; Schindewolf, 1953; Ruzhencev, 1960). The oldest representative of the Ceratitida is known from the lower Middle Permian (Roadian) and is referable to Paraceltites, which is characterized by a thinly discoidal, widely evolute conch, round venter, a prominent ventral sali- ent in the growth lines, and unserrated lobes (Spinosa et al., 1975). Compared to the other prolecanitid ammonoid genera, the genus shares more similar features of conch and suture morphology with Daraelites, so that previous authors considered that Paraceltites evolved from a daraelitid stock in the Prolecanitida, probably Daraelites (Ruzhencev, 1960, 1962). Zakharov (1984, 1988), however, showed that the lobe development of the Prolecanitida is identical with that of the Goniatitida. He noted that the ammonoid family occurring in the Lower Permian, which shares common features of conch morphology, ornamentation and suture with Paraceltites, is the Eothinitidae in the Goniatitida. Paraceltites and Eothinitidae both display a widely evolute conch with mar- ginal ribs rather than nodes, round venter, and simple adult suture line. Based on these facts Zakharov (1984, 1988) suggested that Paraceltites evolved from the Eothinitidae, probably Epiglyphioceras (Zakharov, 1984, 1988). However, except for the simple adult suture line, Daraelites also possesses these characters. Inference of a possible ancestor of Paraceltites on the basis of only conch morphology and ornamentation should be avoided if other features can be utilized to resolve this ancestor-descendant problem. The Prolecanitida and Goniatitida each exhibit certain dis- tinct features in their early internal shell features that can be brought to bear on this problem. Available data show that the Prolecanitida share a short and curved prosiphon, a bot- tle-shaped or gourd-shaped caecum without a conspicuous constricted base at proseptum in median section, long prosepta on dorsal side, a ventral siphuncle, and a relatively small ammonitella angle (328-350°). The second septum does not appear in close vicinity to the proseptum. Meanwhile, species of the Goniatitida share a short and curved prosiphon, a subelliptical or elliptical caecum with a strongly constricted base at proseptum, short prosepta on dorsal side, a ventral siphuncle, and a relatively large ammonitella angle (352-385°). The second septum is close to proseptum on the dorsal side, forming a necklike structure in median section. Paraceltites elegans has a long proseptum on the dorsal side, and the second septum does not appear in close vicin- ity to proseptum. The ammonitella angle is 342° in the specimen examined. These features are characteristic of early internal shell features of the prolecanitid Daraelites elegans rather than the Goniatitida. These similarites of early ontogenetic shell features as well as the conch mor- phology of shell shape, ornamentation and sutural develop- ment strongly suggest a close phylogenetic relationship between Daraelites and Paraceltites. These observations strongly support the hypothesis of the daraelitid origin for the Ceratitida as proposed by Ruzhencev (1960, 1962). 210 Yasunari Shigeta et al. Acknowledgments We are very grateful to H. Maeda (Kyoto University) for his kind help and cooperation throughout the field survey, T. Sasaki (University of Tokyo) for arranging loans of speci- mens described by Tanabe et al. (1994), and K. Tanabe (University of Tokyo) for critical reading of the manuscript. This study was supported by the JSPS Fellowships for re- search in NIS countries and the Grant-in-Aid for Scientific Research from JSPS (nos. 12440141 and 13740302) to Y. Shigeta. References Bogoslovskaya, M. F., 1959: Vnutrennee stroenie rakovin nekotorykh artinskikh ammonoidej. Paleontologicheskij Zhurnal, 1959, no. 1, p. 49-57, pl. 2. [Internal structure of the shells of some Artinskian ammonoids.] (in Russian) Bogoslovskaya, M. F., Kuzina, L. F. and Leonova, T. 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D., 1978: Rannetriasovye ammonoidei Vostoka SSSR. 224 p., Nauka, Moscow. [Lower Triassic ammonoids of East USSR.] (in Russian) Zakharov, Y. D., 1983: Rost i razvitie ammonoidej i nekotorye problemy ekologii i evolutsii. /n, Starobogatov, Ya. |. and Nesis K. N. eds., Sistematika i ekologiya golovonogikh molluskov, p. 26 - 31. Akademiia Nauk SSSR, Zoologicheskij Institut, Leningrad. [Growth and develop- ment of the ammonoids and some problems of ecology and evolution.] (in Russian) Zakharov, Y. D., 1984: Ontogenez permskikh Pronoritidae i Medlicottiidae i problema proiskhozhdeniya tseratitov. In, Gramm, M. N. and Zakharov, Y. D. eds., Sistematika i evolutsiya bezpozonitchnykh Dalnego Vostoka, p. 23-40. Dalnevostotchnyi Nautchnyi Tsentr Akademii Nauk SSSR, Vladivostok. [Ontogeny of the Permian Pronoritidae and Medlicottidae and the problem of ceratitid origin.] (in Russian) Zakharov, Y. D., 1988. Parallelism and ontogenetic accelera- tion in ammonoid evolution. /n. Wiedmann, J. and Kullmann, J. eds., Cephalopods-Present and Past, p. 191-206. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart. 212 Yasunari Shigeta et al. Appendix 1. List of material, and measurement data and character states of the species exam- morphotype, G: Goniatites morphotype, E: Epicanites morphotype, M: Marathonites morphotype, N: Bogoslovskaya et al. (1999). Species Horizon Locality Sample Order Prolecanitida Prolecanitoidea Epicanites loeblichi Miller & Furnisii Chesterian Jack Fork Creek, Oklahoma NSM PM16188 Daraelites elegans Tchemow Artinskian Aktasty R., South Urals NSM PM16189 Pronoritoidea Neopronorites skvorzovi (Tchernow) Artinskian Aktasty R., South Urals NSM PM16190 Medlicottioidea Akmilleria electraensis (Plummer & Scott) Wolfcampian Buck Mountain, Nevada NSM PM16191 Artioceras rhipaeum (Ruzhencev) Artinskian Aktasty R., South Urals NSM PM16192 Order Goniatitida Dimorphoceratoidea Girtyoceras meslenanum (Girty) Chesterian Jack Fork Creek, Oklahoma NSM PM16193 Eumorphoceras plummen Miller & Youngquist Chesterian San Saba, Texas UMUT PM19030 Gathentes morrowensis (Miller & Moore) Morrowan Gather Mt., Arkansas UMUT PM19032 Goniatitoidea Goniatites multiliratus Gordon Chesterian Jack Fork Creek, Oklahoma NSM PM16194 Goniatites aff. crenistria Phillip Chesterian Ahloso, Oklahoma UMUT PM19019-2 Goniatites choctawensis Shumard Meramecian Clarita, Oklahoma UMUT PM19020-2 Agathiceras uralicum (Karpinsky) Artinskian Aktasty R., South Urals NSM PM16195 Agathiceras applini Plummer & Scott L. Permian Coleman, Texas NSM PM16196 Neoglyphioceratoidea Neoglyphioceras abramovi Popow Namurian Menkyule R., Verkhoyansk NSM PM16197 Cravenoceras incisum (Hyatt) Chesterian San Saba, Texas NSM PM16198 Cravenoceras lineolatum Gordon Chesterian Lick Mountain, Arkansas NSM PM16199 Cravenoceras richardsonianum (Girty) Chesterian Wapanucka, Oklahoma UMUT PM19021 Somoholitoidea Glaphyrites hyattianus (Girty) Glaphyrites warei (Miller & Owen) Glaphyrites jonesi (Miller & Owen) Glaphynites clinei (Miller & Owen) Gastrioceratoidea Homoceras subglobosum (Bisat) Arkanites relictus (Quinn, McCaleb & Webb) Thalassoceratoidea Bisatoceras sp. Desmoinesian Desmoinesian Desmoinesian Desmoinesian L. Namurian Morrowan Desmoinesian Eothalassoceras inexpectans (Miller & Owen) Desmoinesian Okmulgee, Oklahoma Collinsville, Oklahoma Collinsville, Oklahoma Collinsville, Oklahoma Stonehead Beck, Yorkshire Bradshaw Mt., Arkansas Okmulgee, Oklahoma Okmulgee, Oklahoma NSM PM16200 NSM PM16201 UMUT PM19027 UMUT PM19028 NSM PM16202 UMUT PM19029 UMUT PM19033-1 UMUT PM19036-1 Thalassoceras gemmellaroi Karpinsky Artinskian Aktasty R., South Urals NSM PM16203 Adrianitoidea Crimites subkrotowi Ruzhencev Artinskian Aktasty R., South Urals NSM PM16204 Crimites elkuensis Miller, Furnish & Clark Wolfcampian Buck Mountain, Nevada NSM.PM16205 Texoceras sp. Roadian El Capitan, Texas UMUT PM19037-1 Marathonitoidea Kargalites typicus (Ruzhencev) Artinskian Aktasty R., South Urals NSM PM16206 Marathonites invariabilis (Ruzhencev) Artinskian Aktasty R., South Urals NSM PM16207 Neoicoceratoidea Metalegoceras sp. Wolfcampian Buck Mountain, Nevada NSM PM16208 Metalegoceras baylorense White Wolfcampian Buck Mountain, Nevada UMUT PM19035 Eothinites kargalensis Ruzhencev Artinskian Aktasty R., South Urals NSM PM16209 Paragastrioceras kirghizorum Voinova Artinskian Aktasty R., South Urals NSM PM16210 Paragastnoceras artolobatum Ruzhencev Artinskian Aktasty R., South Urals NSM PM16211 Uraloceras complanatum (Voinova) Artinskian Aktasty R., South Urals NSM PM16212 Uraloceras sp. Wolfcampian Buck Mountain, Nevada NSM PM16213 Popanoceratoidea Popanoceras annae Ruzhencev Artinskian Aktasty R., South Urals NSM PM16214 Order Ceratitida Xenodiscoidea Paraceltites elegans Girty Roadian Guadalupe Mts., Texas NSM PM16215 ee ined. Data source: 1. Spinosa et al. (1975). Neopronorites morphotype, T: Thalassoceras morphotype. Origin of the ceratitid ammonoid Abbreviations: A: Agathiceras morphotype, D: Daraelites Major taxonomic positions from Initial chamber Ammonitella Length Shape of Length of Proseptum & Initial Morpho- size (mm) size angle of pro- caecumin prpseptum 2nd septum position type Max. Min. (mm) (deg.) siphon mediansection (dorsal side) (dorsal side) of sipuncle 0.426 0393 0.870 355 Short Bottle-shaped Long Separate (fairly) Ventral = 0.466 0.405 0.913 350 ? Bottle-shaped Long Separate (alittle) Ventral D 0.645 0.578 1.147 328 Short Gourd-shaped Long Separate (alittle) Ventral N 0.633 0.550 1.250 338 Short Bottle-shaped Long Separate (fairly) Ventral E 0.356 0.311 0.702 334 Short Bottle-shaped Long Separate (fairly) Ventral E 0.543 0462 0906 368 Short Subelliptical Long Close Ventral G — — 1.032 — ? ? ? ? Ventral ? 0.416 0.370 0.833 385 ? ? Long Close Ventral G 0.545 0.470 0.978 360 Short Subelliptical Long Close Ventral G 0.566 0.533 0.995 380 ? Subelliptical Long Close Ventral G 0.541 0.483 0.996 383 Short Subelliptical Long Close Ventral G 0.513 0.451 0.949 369 Short Elliptical Short Close Central A 0.520 0.466 1.010 365 ? Elliptical Short Close Central A 0.522 0.476 0.927 370 Short Subelliptical Long Close Ventral G 0.490 0.446 0.910 360 Short Subelliptical Long Close Ventral G 0.484 0.403 0815 368 Short Subelliptical Long Close Ventral G 0.486 0.446 0.813 367 ? ? Long Close Ventral G 0.590 0.498 1.048 370 Short Subelliptical Long Close Ventral G 0.527 0.458 0.916 369 Short Subelliptical Long Close Ventral G 0.535 0.470 0.920 372 ? ? Long Close Ventral G 0.413 0.373 0.720 379 ty ? Long Close Ventral G 0.496 0.458 0.933 367 Short Subelliptical Long Close Ventral G — — 0.800? — ? ? ? % ? ? 0.360 0.335 0.620 358 Short Elliptical Short Close Subcentral T 0.386 0360 0.680 365 Short ? Short Close Subcentral T 0.365 0.338 0.694 356 Short Elliptical Short Close Subcentral T 0.376 0.332 0681 365 Short Elliptical Short Close Ventral M 0.384 0350 0.725 365 Short Elliptical Short Close Ventral M —> — 0958 — ? ? ? ? 2 ? 0.468 0.419 0.909 360 Short Elliptical Short Close Ventral M 0.382 0.356 0.767 366 Short Elliptical Short Close Ventral M 0.472 0.411 0.833 365 ? ? Short Close Ventral M 0.480 0.410 0.866 365 Short Elliptical Short Close Ventral M 0.381 0.349 0.672 372 ? ? Shon Close Ventral M 0.396 0366 0689 365 ? ? Short Close Ventral M 0.413 0.377 0.736 365 ? ? Short Close Ventral M 0.408 0.370 0.735 32 ? Elliptical Short Close Ventral M 0.517 0.463 0.850 371 Short Elliptical Short Close Ventral M 0.356 0321 0660 352 Short Elliptical Short Close Ventral M 0.463 0400 0.921 342 Short’ Bottle-shaped’ Long Separate (a little) Ventral D Paleontological Research, vol. 5, no. 3, pp. 215-226, September 28, 2001 © by the Palaeontological Society of Japan Taxonomy and distribution of Plio-Pleistocene Buccinum (Gastropoda: Buccinidae) in northeast Japan KAZUTAKA AMANO' and MIKIKO WATANABE’ ‘Department of Geoscience, Joetsu University of Education, Joetsu City, Niigata Prefecture 943-8512, Japan (E-mail: amano @juen.ac.jp) *Yatashinmachi 174-2, Nanao City, Ishikawa Prefecture 926-0015, Japan Received 11 April 2001; Revised manuscript accepted 29 June 2001 Abstract. Twelve species of Buccinum are recorded from the Plio-Pleistocene of northeast Japan. Two new species, Buccinum shibatense and B. saitoi, are proposed, and a total of six distributional types (Types A-F,) are recognized among the 12 species. Three extinct species comprise the type Fu, which is endemic to the Japan Sea borderland. Type A is for species that are extinct in the Japan Sea, but are still living in the Sea of Okhotsk and Bering Sea. Type B species are known as fossils only along the Japan Sea margin, and now live in the northern Japan Sea as well as in the Northwest Pacific and the Sea of Okhotsk. Type C species have been recorded as fossils from the Pacific and the Japan Sea coasts and still live in both coasts. Type D species live only on the Pacific side, and are recorded as fossils only from there. Type E species occur as fossil and living specimens only in the Japan Sea. Species in both types A and Fy species underwent extinction owing to anoxic conditions during Pleistocene glacial episodes along the Japan Sea borderland. The type E species survived in the lower sublittoral to upper bathyal waters of the Japan Sea which had normal salinity and were oxic. Key words: Buccinum, distribution, Pliocene, Pleistocene, taxonomy Introduction Buccinum is a common group of gastropods which lives in cold and rather deep water around the North Pacific Ocean. Some species of Buccinum invaded the Arctic and North Atlantic Oceans after the opening of the Bering Strait in the late Miocene or Pliocene at 4.8-5.5 Ma (Marincovich and Gladenkov, 1999) in the same manner as did the gastropod Neptunea (Durham and MacNeil, 1967; Vermeij, 1991). The modern species of Buccinum have been taxonomi- cally summarized by Golikov (1980) and Tiba and Kosuge (1984). Golikov (1980) described 86 species and 6 subspe- cies from the world ocean while Tiba and Kosuge (1984) re- corded 107 species and 9 subspecies from just the North Pacific. In another study, 68 species and 13 subspecies have been reported in and around Japan (Higo et al., 1999). These differences in number of species and subspecies re- sult mainly from the wide range of morphological variation that obscures the limits of species and subspecies in this genus. Mitochondrial DNA sequences show that the genus can be subdivided into five clades (probably equivalent to subgenera) that are nearly concordant with the characteris- tics of shell morphology: the B. felis, B. inclytum, B. aniwanum, B. middendorffi and B. tsubai groups (Endo and Ozawa, 2001). Recently, Amano et al. (1996) and Amano (1997) summa- rized the taxonomy and distribution of Plio-Pleistocene buccinids, Ancistrolepidinae and Neptunea, from the Japan Sea borderland. These studies demonstrated for both Ancistrolepidinae and Neptunea that many species which no longer live in the Japan Sea continue to dwell in the Sea of Okhotsk and Bering Sea. These authors noted that such species suffered extinction in the Japan Sea owing to paleoenvironmental changes during the Quaternary ice ages. In order to gain further insights into this phenome- non, it is necessary to examine the distributional pattern of additional taxa. Buccinum is well suited to this purpose, be- cause of its ecological similarity to Ancistrolepidinae and Neptunea. Before discussing the distributional pattern of Buccinum, it is necessary to clarify the relationships between the species. However, since most species generally have a thin and frag- ile shell, it is difficult to obtain well preserved specimens. This unsettled classification of the modern species and the poor preservation of fossils preclude a taxonomic summary of this genus in northeastern Japan. In this paper, we will reexamine some well preserved Plio-Pleistocene specimens of Buccinum and will add two new species to the genus. 216 Kazutaka Amano and Mikiko Watanabe Based on our taxonomical reexamination, we also will dis- cuss the distributional pattern of the genus. Materials Fossils identified as Buccinum were recently collected from the following ten localities (Figure 1). 140°E BEN DENN 2 Ok AN o Loc. 1. Large cliff 2.2 km upstream from the mouth of Sakashi-no-sawa, Teshio Town, Hokkaido; gray siltstone; late Pliocene Yuchi Formation. Loc. 2. Outcrop along Shichirinagahama beach about 1.5 km north to Kawajiri, Ajigasawa Town, Aomori Prefecture; greenish gray sandy siltstone; late Pliocene Narusawa Formation. 2 EE SZ 1 BIS TT/ = By Figure 1. Collecting localities of Buccinum (using the topographical maps of “Onoppunai,” “Matsunoyama-Onsen,” “liyama,” scale 1:50,000; “Morita,” “Echigo-Shimoseki,” “Sugatani,” “Ojiya” and “Kanazawa,” scale 1:25,000 published by Geographycal Survey Institute of Japan). Taxonomy and distribution of Plio-Pleistocene Buccinum 217 Loc. 3. Riverside cliff along a side creek of the Onnagawa River, about 600 m south of Housaka Bridge, Sekikawa Village, Niigata Prefecture (Loc. 4 of Amano et al., 1996); siltstone; late Pliocene Kuwae Formation. Loc. 4. Small outcrop on the Koide River about 1.1km up- stream of its mouth, Shibata City, Niigata Prefecture (Fossil locality of Amano, 1998); muddy fine-grained sandstone; late Pliocene Kuwae Formation. Loc. 5. River bank along the Shinano River, 250 m north- east of Unoki, Ojiya City, Niigata Prefecture (Loc. 7 of Amano, 1997); conglomerate; early Pliocene Kawaguchi Formation Loc. 6. Riverside cliff of the Sabaishi River about 300 m east to Azamihira, Matsudai Town, Niigata Prefecture; peb- ble-bearing sandstone; late Pliocene Higashigawa Forma- tion. Loc. 7. Outcrop at Taihei, Matsudai Town, Niigata Prefec- ture; black mudstone; early Pliocene Kurokura Foramtion (upper part). Loc. 8. Riverside cliff of the Shibumi River 400 m east of Taihei, Matsudai Town, Niigata Prefecture; black mudstone; early Pliocene Kurokura Formation (upper part). Loc. 9. Outcrop at Kutta, liyama City, Nagano Prefecture; siltstone; early Pliocene Nagasawa Formation. Loc. 10. River bank of the Saikawa River, 1.1 km up- stream from the Okuwa Bridge, Kanazawa City, Ishikawa Prefecture (Loc. 12 of Amano et al., 1996); fine-grained sandstone; early Pleistocene Omma Formation We examined all specimens stored at the Joetsu University of Education (JUE), including the above-cited specimens as well as those obtained in the following studies: Amano and Kanno (1991), Nakata and Amano (1991), Amano and Karasawa (1993), Amano (1994) and Amano and Sato (1995). In addition, specimens including types were reexamined at the following institutions and museums: Tohoku University (IGPS), Saito Ho-on Kai Museum of Natural History (SHM), University of Tsukuba (IGUT), National Science Museum(NSM), and Kyoto University (JC). Moreover, private collections of Mr. Masayuki Shimizu (Tateyama Mus.) were also examined. In addition to our collections and those mentioned above, geographical distributions were compiled from a critical sur- vey of the literature (Iwai, 1965; Noda and Masuda, 1968; Baba, 1990). Systematic description of new species Family Buccinidae Rafinesque, 1815 Genus Buccinum Linnaeus, 1758 Buccinum shibatense sp. nov. Figure 2. 3, 2.6 Type specimen.—Holotype, JUE no. 15699, 39.7 mm high, 23.3 mm wide; Paratype, JUE no. 15700, 25.6 mm high, 24.6 mm wide. Type locality. —Loc. 4. Diagnosis. —Small species of Buccinum characterized by numerous spiral cords (36 to 40 on body whorl), two fine columellar plaits at base of inner lip, and thick outer lip weakly crenulated on inner side. Description.—Shell rather small for genus, conico-ovoidal shape; protoconch one and a half smooth whorls; teleocon- ch of seven whorls. Height of body whorl occupying about five-eighths of shell height. Suture shallow and slightly un- dulating on body whorl. Axial sculpture of many fine growth lines; spiral cords low, separated by shallow grooves, 16 (holotype) and 20 (paratype) on penultimate whorl, 36 (holotype) to 40 (paratype) on body whorl. Spiral cords on body whorl with one shallow groove. Aperture ovate; inner lip covered by thin calcareous callus, two fine and distinct columellar plaits at its base; outer lip thick, with 19 weak striae along inner side, excavated behind. Siphonal canal shallow and slightly twisted; posterior sinus narrow and short. Remarks.—At a glance, this species resembles Pseudo- liomesus ooides (Middendorff, 1849) in its shell outline and slightly twisted basal part of the inner lip. It differs from P. ooides by lacking a deep suture or a subsutural area. Comparison. —The present species is closely allied to Buccinum habui Tiba, 1984, now living at 400-500 m depth off southern Hokkaido (Higo et al., 1999). B. habui is also characterized by numerous spiral cords (26 on penultimate; 44 on body whorl), one or two fine columellar plaits at the base of the inner lip, and weak crenulations in the inner side of the thick outer lip. However, B. shibatense can be easily distinguished from B. habui by its larger shell size, less slen- der shell outline, existence of a posterior sinus, and slightly twisted siphonal canal. Buccinum saitoi sp. nov. Figure 2. 8, 2.9 Type specimen.—Holotype, JUE no. 15701, 58.8+ mm high, 29.1 mm wide; Paratype, JUE no. 15702, 31.8 mm wide. Type locality.—Loc. 4. Diagnosis. — Medium-size Buccinum characterized by thick and high spire, numerous and fine subsutural granulations, distinct nodes on shoulder (13 on body whorl). Description.—Shell size medium for genus, slender and thick; protoconch poorly preserved and of more than one whorl; teleoconch of six whorls. Spire rather high, occupy- ing about half of shell height. Suture shallow and slightly undulating on body whorl, with many fine subsutural granulations. Above shoulder, 13 oblique low axial ribs; 13 distinct nodes at shouldered edge; spiral cords low, fine, separated by narrow grooves, 13 on penultimate and 15 on body whorl. Below shoulder including base, surface sculp- ture consisting only of spiral cords; 8 on penultimate and 25 on body whorl. Aperture ovate; inner lip covered by thin cal- careous callus, nearly straight at its base; outer lip thick, smooth on inner side, excavated behind. Siphonal canal shallow; posterior sinus narrow and very short. Comparison.—The present new species is closely allied to Buccinum verrucosum Tiba, 1980 now living in the Sea of Okhotsk. B.verrucosum shares the following characteristics with the present new species: similar shell outline, thick shell, many fine subsutural plications, axial ribs above the shoulder and some granulations on the shoulder. However, B. verrucosum differs from B. saitoi by having three strong iko Watanabe = D = © fe) S © E < © © 5 N © x Taxonomy and distribution of Plio-Pleistocene Buccinum 219 spiral cords and two obscure columellar plaits. Buccinum opisoplectum Dall, 1907 can be easily distin- guished from B. saitoi in having a smaller shell, lacking granulation on the shoulder and having three strong spiral cords. Etymology.— This species is named after Mr. Atsushi Saito of Niigata Higashi High School, who collected the type specimens. Revision of some fossil species Buccinum sinanoense -was originally established by Makiyama (1927) based on the specimen (Figure 3. 4) from the early Pliocene Joshita Formation in Nagano Prefecture. Nomura (1937) illustrated a specimen as B. sinanoense Kuroda (?) (sic! from the Pliocene Kannonji Formation in Yamagata Prefecture. Based on an examination of his specimen, it is not referable to B. sinanoense because of its low and large body whorl. However, the poor preservation of its shell surface prevents us from definitely assigning this specimen to a species. Buccinum aomoriensis Hatai, Masuda and Suzuki,1961 is represented by a single specimen (Figure 3. 9) from the early Pleistocene Hamada Formation in Aomori Prefecture. This species is characterized by a large shell (shell height = 95.0 mm), many fine subsutural plications, 17 axial folds on the penultimate whorl, two strong spiral cords with two to seven intercalating cords on each whorl, and an inner lip with two columellar plaits. When they established this spe- cies, Hatai et al. (1961) did not compare their species with the closely related species, B. inclytum Pilsbry, 1904. The two species cannot be consistently distinguished, so we consider B. aomoriensis to be a junior synonym of B. inclytum. Akamatsu and Suzuki (1992) illustrated a fragmentary specimen from the early Pleistocene Shimonopporo For- mation as Buccinum opisthoplectum Dall [sic]. However, judging from their figure, this specimen is referable to B. inclytum because of its large shell (more than 50 mm without body whorl) and three rather strong spiral cords. Hatai and Nisiyama (1952) proposed the new species Buccinum wakimotoense based on a specimen from the middle Pleistocene Shibikawa Formation in Akita Prefecture, which Kanehara (1942) referred to as “B. schantaricum Middendorff.” However, they did not give a description or definition at that time. Judging from Kanehara’s (1942) fig- ure and a specimen from the Shibikawa Formation (Figure 2. 5), there is no difference between B. wakimotoense and the modern B. middendorffi Verkrüzen, 1882 as pointed out by Masuda and Noda (1976). Therefore, B. wakimotoense is a junior synonym of B. middendorffi. Buccinum rhodium Dall, 1919 lives in the Sea of Okhotsk and Bering Sea (Tiba and Kosuge, 1984). It has 22 strong sigmoid axial ribs. The specimen figured by Fujii and Shimizu (1988; Figure 3. 7) as Plicifuscus [this should be “Plicifusus’) cf. plicatus {sic] from the Pliocene Mita Formation in Toyama Prefecture has a rather large body whorl, 18 sigmoid axial ribs and 40 spiral cords. Judging from the outline and shell sculpture, their specimen is refer- able to B. rhodium. The spiral cords of modern specimens are generally weaker than on fossils. Nomura (1937) recorded one specimen as Ancistrolepis fragilis Dall var. (Figure 3. 5) from the Pliocene Kannonnji Formation in Yamagata Prefecture. However, it lacks a deeply channeled suture which is characteristic of Ancistrolepidinae. This specimen should be referred to Buccinum unuscarinatum Tiba, 1981, which lives in the Sea of Okhotsk, because of the one keel at its shoulder and many fine weak spiral cords. Buccinum cf. striatissimum Sowerby was described by Ozaki (1958) from the Plio-Pleistocene lioka Formation in Chiba Prefecture. His specimen has a constricted body whorl, a large protoconch, and a deeply channeled subsutu- ral area, all of which are characters of Ancistrolepidinae. Therefore, the lioka specimen is not a Buccinum. Buccinum suruganum kasimensis was established by Ozaki (1958) as a new subspecies, based on one imperfect specimen (NSM P1 4402) from the Pliocene Naarai Formation. Based on our reexamination of this specimen, it is clear that the number of spiral cords (four cords on the penultimate whorl) and the condition of interspaces of the ribs are included in the variation of B. leucostoma Lischke, 1872. When he established Buccinum yoroianum as a new spe- cies, Ozaki (1958) designated a small specimen (Figure 2. 2) as the paratype. However, this paratype specimen dif- fers from the holotype in having very weak spiral cords and well inflated whorls. Based on the shell outline, size and sculpture of the paratype specimen, it is assigned to B. bulimiloideum Dall, 1907. Distributional patterns The twelve Plio-Pleistocene species of Buccinum and their geological distributions in northeastern Japan are shown in Table 1. There are six types of distribution (Types A-Fy; Figures 4, 5). Type A (B. rhodium and B. unuscarinatum) is for species that are extinct in the Japan Sea, but are still living at lower sublittoral to upper bathyal depths in the Sea of Okhotsk and Bering Sea. Some Ancistrolepidinae and Neptunea show a similar distribution (Amano et a/., 1996; Amano, 1997). Buccinum middendorffi and B. inclytum belong to Type B. Fossils of these species are known only from the Japan Sea @ Figure 2. 1, 5. Buccinum middendorffi Verkrüzen. 1, x1, JUE no. 15706, Loc. 1, Yuchi Formation. 5, x1, JUE no. 15707, Loc. Anden, Akita Pref., Shibikawa Formation. 2a, b. Buccinum bulimiloideum Dall, x1.5, NSM no. 4464, “Paratype” of B. yoroianum Ozaki, lioka Formation. no. 15708, Loc. 6, Higashigawa Formation. 15702, Paratype; Loc. 4, Kuwae Formation. Formation. 3a, b, 6. Buccinum shibatense sp. nov. 3a, b, x1, JUE no. 15699, Holotype; 6, x1, JUE no. 15700, Paratype; Loc. 4, Kuwae Formation. 4a, b, 7. Buccinum tsubai Kuroda. 4a, b, IGUT no.15602, Loc. Kitaubushi, Hokkaido, Yuchi Formation. 8a, b, 9. Buccinum saitoi sp. nov. 10a, b. Buccinum striatissimum Sowerby, x0.8, JUE no. 15709, Loc. 8, Kurokura 11a, b. Buccinum ochotense (Middendorff), x0.9, IGPS no. 90462, Loc. 6 of Hatai et al. (1961), Hamada Formation. 7,x1, JUE 8a, b, x1, JUE no.15701, Holotype; 9, x1, JUE no. Kazutaka Amano and Mikiko Watanabe Taxonomy and distribution of Plio-Pleistocene Buccinum to to — Table 1. Distribution of the Plio-Pleistocene Buccinum. * living depth after Higo et al. (1999). Species Age and formation Depth range* Type A Buccinum rhodium Dall B. unuscarinatum Tiba Pliocene Nakawatari F., Nagasawa F., Mita F. 100-300m Pliocene Kannonji F., Kuwae F., Kurokura F. — Nagasawa F., Nadachi F. Type B B. middendorffi Verkrüzen Pliocene Yuchi F.; Early Pleistocene Omma F Middle Pleistocene Shibikawa F. B. inclytum Pilsbry Type C B. ochotense (Middendorff) Early Pleistocene Shimonopporo F., Hamada F. Pliocene Gobanshoyama F.; Early Pleistocene 0-50m Shimonopporo F., Hamada F., Daishaka F. Type D B. leucostoma Lischke B. bulimiloideum Dall Type E B. striatissimum Sowerby Nadachi F. B. tsubai Kuroda Mita F. Type Fs B. sinanoense Makiyama B. shibatense sp. nov. B. saitoi sp. nov. Pliocene to early Pleistocene Kazusa G. Early Pleistocene lioka Formation Pliocene Narusawa F., Kurokura F., Nagasawa F., Pliocene Yuchi F., Kawaguchi F., Higashigawa F., 50-600m 300-900m 0-50m 200-500m 100-700m Pliocene Joshita F., Ogikubo F. — Pliocene Kuwae F. Pliocene Kuwae F. borderland. Type B species now live in the upper sublittoral zone of the northern Japan Sea as well as the Northwest Pacific and the Sea of Okhotsk. Type C includes only one species, B. ochotense. This type of species is the same as the C type of Neptunea which has been recorded as fossils from the Pacific and the Japan Sea coasts and also lives in the upper sublittoral zone of both coasts. Two species (type D) live only from the lower sublittoral to the upper bathyal zone on the Pacific side, and their fossils are also recorded only from the Pacific side. These are B. leucostoma and B. bulimiloideum. Such a distribution has also been observed in the buccinids Clinopegma unicum, Neptunea kuroshio, N. fukueae and N. kanagawaensis (Amano et al., 1996; Baba, 1990; Kato, 1993). Type E species (B. striatissimum and B. tsubai) are known as fossil and living specimens only from the Japan Sea. No species of Neptunea or Ancistrolepidinae shows this type of distribution. Three extinct species (B. sinanoense, B. shibatense and B. saitoi) comprise type Fu, endemic to the Japan Sea bor- derland. It is noteworthy that no extinct species of Buccinym is confined to the Plio-Pleistocene of the Pacific Ocean side. This type of distribution does occur in Ancistrolepidinae (Amano et al., 1996) and Neptunea (E type; Amano, 1997). Discussion of distribution Species of types A and Fu underwent extinction during the Pleistocene in the Japan Sea borderland. Tada (1994) noted that bottom sediments alternated between oxic and anoxic conditions with the glacio-eustatic sea level changes many times after the late Pliocene. He also pointed out that remarkable sea level oscillations are recognized during the last 0.8 m.y. During the low glacial sea level stands, fresh- water input reduced salinity and created euxinic conditions in the enclosed Japan Sea. The type A species occurred @ Figure 3. 1,6, 7a, b. Buccinum rhodium Dall. 1, x1, JUE no. 15360, Loc. N5 of Nakata and Amano (1991); 6, x1, JUE no. 15703, Loc. 9; Nagasawa Formation. 7a,b, x1, Loc. Rengeji, Toyama Pref., illustrated by Fujii and Shimizu (1988) as Plicifuscus cf. plicatus, Mita Formation. 2, 3, 5. Buccinum unuscarinatum Tiba. 2, x1, JUE no. 15704, Loc. 7, Kurokura Formation. 3, x0.8, JUE no. 15613, Loc. 32 of Amano and Kanno (1991), Nadachi Formation. 5, x1, SHM no. 8407, Loc. Futago, Yamagata Prefecture, illustrated by Nomura (1937) as Ancistrolepis fragilis var., Kannonji Formation. 4. Buccinum sinanoense Makiyama, x1, JC no. 610024, Holotype, Joshita Formation. 8. Buccinum middendorffi Verkrüzen, x1, JUE no. 15705, Loc. 10, Omma Formation. 9 a,b. Buccinum inclytum Pilsbry, IGPS no. 90509, Hamada Formation, “Holotype“ of B. aomoriensis Hatai, Masuda and Suzuki. Type A Recent | Fossil @ e Buccinum rhodium A a B. unuscarinatum Type C Recent Fossil A A Buccinum ochotense Kazutaka Amano and Mikiko Watanabe Type B © 2 0) Recent Fossil @ e Buccinum middendorffi A a B. inclytum Lu Recent w £ Fossil I & @ e Buccinum leucostoma A a B. bulimiloideum Figure 4. Distributional pattern (types A-D) of Buccinum. Taxonomy and distribution of Plio-Pleistocene Buccinum from the lower to upper Pliocene while the type Fu species ranged from the lower to middle Pliocene. Thus, it is reasonable to infer that type A species became extinct in the Japan Sea whereas the Sea of Okhotsk and Bering Sea populations survived. The narrowly distributed endemic Fu type species became extinct after the late Pliocene. Two explanations are available to explain the distribution pattern of the types B and C. First, the species of these types survived the deteriorated environment in the Japan Sea during the Quaternary ice ages. Second, the popula- tions of species in types B and C became extinct in the Japan Sea, but survived on the Pacific side. Species of both types live in upper sublittoral depths while those of other types dwell in lower sublittoral to upper bathyal waters. Based on the presence of type A and Fy species and the low-salinity surface water of the glacial age, it is reasonable to accept the second hypothesis. Thus, the modern popula- tions of types B and C species in the Japan Sea may repre- sent recent invasions through its shallow northern entrance. The fossil records of the type D species are concentrated in the Pacific side of central Japan (Kanto Region). These species are also deep-water dwellers and survived the gla- cial episodes only in the Pacific Ocean. Type E species that survive as endemics in the Japan Sea live in intermediate waters. As already noted by Amano (1996), Portlandia toyamaensis (Kuroda, 1929) also shows this type of distribution. The same pattern occurs in the buccinids Mohnia yanamii (Yokoyama, 1926) and Lussi- volutopsius furukawai (Oyama, 1951). Mohnia yanamii is a Type E , | ‘9 Recent Fossil @ eo Buccinum striatissimum } A a B. tsubai [59] th Ww Table 2. Bathymetric distribution of the Japan Sea endemic spe- cies with fossil records. * living depth after Higo et al. (1999). Species Depth (m)* Alvania sitta (Yokoyama) 200-204 Lussivolutopsius furukawai (Oyama) 200-350 Mohnia yanamii (Yokoyama) 50-400 Buccinum striatissimum Sowerby 200-500 B. tsubai Kuroda 100-700 Curtitoma exquisita (Yokoyama) 300-400 Propebela komakahida (Otuka) 200-350 P. tayensis (Nomura and Hatai) 150 Yoldia kikuchii Kuroda 100-150 Portlandia toyamaensis (Kuroda) 100-600 characteristic species of the Omma-Manganji fauna (Otuka, 1939) and now lives in 50-400 m depth in the Japan Sea (Higo et al., 1999). Lussivolutopsius furukawai is also known as an endemic species in the Japan Sea (200-350 m depth; Higo et al., 1999) and there is one fossil specimen from the lower Pleistocene Sawane Formation at Tohoku University (IGPS no. 73410). Summarizing the Japan Sea endemic species that have fossil records (Table 2), all live in depths from 100 m-400 m. Horikoshi (1986) suspected that some species at an intermediate depth could survive during the Quaternary glacial ages. Based on radiolarian fossils from a core at GH-95 St 1208, off Shakotan Peninsula, Type Fu 9) @ Buccinum sinanoense A B. shibatense A = B. saitoi Figure 5. Distributional pattern (types E, Fu) of Buccinum. 224 Kazutaka Amano and Mikiko Watanabe Table 3. *Amano (1997) ** Amano et al. (1996) Distributional types of Buccinum, Neptunea and Ancistrolepidinae. Types Buccinum Neptunea* Ancistrolepidinae** Fy B. sinanoense N. eos Ancistrolepis masudaensis B. shibatense N. hataii A. koyamai B. saitoi N. nikkoensis A. peulepis A. aff. hikidai Clinopegma fragilis A B. rhodium N. lamellosa Ancistrolepis grammatus B. unuscarinatum N. satura Clinopegma borealis N. insularis Bathyancistrolepis trochoideus N. vinosa B B. middendorffi N. lyrata — B. inclytum N. bulbacea N. rugosa C B. ochotense N. intersculpta — N. arthritica D B. leucostoma N. kuroshio Clinopegma unicum B. bulimiloideum N. fukueae N. kanagawaensis E B. striatissimum — B. tsubai Hokkaido, Itaki et al. (1996) inferred normally saline and oxic water at depths of 200-300 m during the last glacial age (18-15 kyr BP). The inferred survival depth (200-300 m) of radiolarians is similar to that for the molluscs (100-400 m). Therefore, the endemic molluscs noted above, including type E of Buccinum, might have been able to survive the Quaternary glacial ages in the normal saline and oxic water lying between the brackish surface and the euxinic bottom waters. Based on the discussion above, we synthesize the distri- butional pattern of Buccinum, Neptunea and Ancistrolepi- dinae in Table 3. It is noteworthy that 20 species (56%) belong to the type Fu or A, and there are no extinct species whose fossil records are confined to the Pacific side. Many authors have cited temperature change as one of the impor- tant causes of extinction (ex. Stanley, 1984). However, from the above lines of evidence, we postulate that the ex- tinction of species was induced by environmental change in the Japan Sea accompanying the glacio-eustatic sea level changes during the Quaternary ice ages, not by sea surface temperature. Valentine and Jablonski (1991) noted that marine inverte- brate faunas that are not perched are unlikely to suffer ex- tinction by eustatic sea-level changes alone. They also pointed out that the trapped fauna in enclosed areas are vulnerable to any local environmental deterioration. The present study reveals the mechanism of extinction associ- ated with glacio-eustatic sea level changes in a marginal sea. Tada (1994) illustrated the two-layer model of the Japan Sea during the glacial period with a surface brackish layer and deep anoxic water. However, the existence of type E species in Buccinum suggests the possibilities of normal oceanic water between these two layers. Acknowledgments | am grateful to Geerat J. Vermeij (Univ. California, Davis) and Louie Marincovich, Jr. (California Acad. Sci.) for their critical reading of the manuscript. | thank Hiroshi Noda (Univ. Tsukuba), Masanori Shimamoto (Tohoku Univ.), Tomoki Kase (Nat. Sci. Mus.), Sadako Takeuti (Saito Ho-on Kai Mus.), Masayuki Shimizu (Tateyama Mus.), and Atsushi Saito (Niigata Higashi High School) for their help in examin- ing some fossil specimens. References Akamatsu, M. and Suzuki, A., 1992: Stratigraphy and paleoenvironment of the lower Pleistocene on the hills around Ishikari Lowland, Hokkaido. Annual Report of the Historical Museum of Hokakido, no. 20, p.1-30. (in Japanese with English abstract) Amano, K., 1994: Pliocene molluscan fauna and its paleoenvironment in Matsunoyama-machi, Niigata Prefecture. Journal of Geography, vol. 103, no. 6, p. 653-673. (in Japanese with English abstract) Amano, K., 1996: Portlandia toyamaensis (Kuroda) as an en- demic bivalve of Japan Sea. /n, Noda, H. and Sashida, K. eds., Prof. H. Igo Commemorial Volume on Geology and Paleontology of Japan and Southeast Asia, p. 141- 146. Gakujutsu Tosho Insatsu Co., Tokyo. 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(in Japanese with English abstract) Amano, K. and Sato, H., 1995: Relationship between embaymental associations and relict species-Molluscan fauna from the Pliocene Joshita Formation in the northern part of Nagano Prefecture. Fossils, no. 59, p. 1-13. (in Japanese with English abstract) Amano, K., Ukita, M. and Sato, S., 1996: Taxonomy and distribution of the subfamily Ancistrolepidinae (Gastropoda: Buccinidae) from the Plio-Pleistocene of Japan. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 182, p. 467-477. Baba, K., 1990: Molluscan Fossil Assemblages of the Kazusa Group, South Kwanto, Central Japan, 445 p., Keio Yochisha, Tokyo. (in Japanese) Dall, W. H., 1907: Description of new species of shells, chiefly Buccinidae, from the dredgings of the U.S.S. “Albatross” during 1906, in the northwestern Pacific, Bering, Okhotsk and Japanese Seas. Smithsonian Miscellaneous Collec- tions, vol. 50, no. 2, p. 139-173. Dall, W. H., 1919: Description of new species of Mollusca from the north Pacific Ocean in the collection of the United States National Museum. Proceedings of the United States National Museum, vol. 56, no. 2295, p. 293-371. Durham, J. W. and MacNeil, F. S., 1967: Cenozoic migrations of marine invertebrates through the Bering Strait region. In, Hopkins, D. M. ed., The Bering Land Bridge, p. 326- 349. Stanford University Press, Stanford, California. Endo, M. and Ozawa, T., 2001: Phylogenetic analysis of Buccinum and Neptunea inferred from mtDNA se- quences. Abstract with Programs of the 150th Regular Meeting of the Palaeontological Society of Japan, p. 45. (in Japanese) Fujii, S. and Shimizu, M., 1988: On the molluscan fossils oc- curred from Rengeji, Fuchu-machi, Neigun, Toyama Prefecture, central part of Japan. Journal of the College of Liberal Arts, Toyama University, Natural Science, vol. 21, no. 2, p. 75-89. (in Japanese with English abstract) Golikov, A. N., 1980: The molluscs Buccininae of the world Ocean. Fauna of the USSR, Mollusca, vol. 5, Sect. 2, p. 1-465, pls.1-42. (in Russian) Hatai, K., Masuda, K. and Suzuki, Y., 1961: A note on the Pliocene megafossil fauna from the Shimokita Peninsula, Aomori Prefecture, Northeast Honshu, Japan. Saito Ho- on Kai Museum, Research Bulletin, no. 30, p. 18-38, pls. 1-4. Hatai, K. and Nisiyama, S. 1952: Check list of Japanese Tertiary marine Mollusca. Science Reports of the Tohoku University, 2nd Series, Special Volume, no. 3, p. 1-464. Higo, S., Callomon, P. and Goto, Y. 1999: Catalogue and Bibliography of the Marine Shell-bearing Mollusca of Japan, 749 p. Elle Scientific Publications, Yao. Horikoshi, M., 1986: Biofacies and communities of Japan Sea. In, Horikoshi,M., Nagata, Y. and Sato, T eds., Seas around Japanese Islands, p.257-271, Iwanami Shoten, Tokyo. (in Japanese) Itaki, T., Funakawa, T. and Motoyama, |., 1996: Change in the radiolarian communities in the northeast part of Japan Sea, off Shakotan, Hokkaido, since the last glacial age. Preliminary Reports on Researches in the 1995 Fiscal Year, Comprehensive Study on Environmental Changes in the Western Hokkaido Coastal Area, p. 171-185, Geological Survey of Japan, Tsukuba. (in Japanese) Iwai, T., 1965: The geological and paleontological studies in the marginal area of the Tsugaru basin, Aomori Prefecture, Japan. Bulletin of Educational Faculty of Hirosaki University, no. 15, p. 1-68, pls. 12-20. Kanehara, K., 1942: Fossil Mollusca from Tayazawa, Waki- moto-mura, Katanishi oil field. Journal of the Geological Society of Japan, vol. 49, no. 581, p. 130-133, pl. 3. (in Japanese) Kato, S., 1993: Studies on the genus Neptunea, principally from Japan and the surrounding seas. Hitachiobi, nos. 61/62, p. 6-74, pls. 1-40. (in Japanese) Kuroda, T., 1929: Catalogue of Japanese Mollusca. Venus, vol. 1, appendix, p. 1-26. Kuroda, T., 1931: Mollusca. In, Homma F. ed., Shinano Chubu Chishitsu-shi (Geology of Central Shinano), pt. 4, p. 1-90, pls. 1-13. Kokin-shoin, Tokyo. (in Japanese) Linnaeus, C., 1758: Systema Naturae Editio decima. 823 p., Stockholm. Lischke, C. E., 1872: Diagnosen neuer Meeres-Conchylien von Japan. Malakozoologische Blätter, vol. 19, p. 100- 109. Makiyama, J., 1927: Preliminary report on the Tertiary fossils from Kami-Minochi-gun, Shinano. Chikyu (Globe), vol. 8, no. 2, p. 181-188, pl. 3. (in Japanese) Marincovich, L., Jr., and Gladenkov, A. Y., 1999: Evidence for an early opening of the Bering Strait. Nature, vol. 397, p. 149-151. Masuda, K and Noda, H., 1976: Check list and bibliography of the Tertiary and Quaternary Mollusca of Japan, 1950 1974. Saito Ho-on Kai, Special Publication, no. 1, p. 1- 494. Middendorff, A. T. v., 1849: Beiträge zu einer Malacologia Russica, Abt. 3. Aufzahlung und Beschreibung der zur Meeresfauna Russlands gehörigen Zweischaler. 94 p., 21 pls., St. Petersburg. Nakata, Y. and Amano, K., 1991: Pliocene molluscan associa- tions in the Tomikura District, extended over Niigata and Nagano Prefectures, Japan. Bulletin of the Mizunami Fossil Museum, no. 18, p. 77-91, pls. 5-7. (in Japanese with English abstract) Noda, H. and Masuda, K., 1968: On the early Miyagian marine fauna from the Ojika Peninsula, Miyagi Prefecture, Japan. Saito Ho-on Kai Museum, Research Bulletin, no. 37, p. 1-9, pl. 1. Nomura, S., 1937: On some Neogene fossils from along the upper course of the Nikko-gawa, Akumi-gun, Yamagata- ken, Northeast Honshu, Japan. Saito Ho-on Kai Museum, Research Bulletin, no. 13, p. 173-178, pl. 24. Otuka, Y. 1939: Mollusca from the Cainozoic System of east- ern Aomori Prefecture, Japan. Journal of the Geological to tN 26 Kazutaka Amano and Mikiko Watanabe Society of Japan, vol. 44, no. 544, p. 23-31, pl. 2. Oyama, K., 1951: Molluscan assemblages at intermediate depths on the Pacific and Japan Sea sides of the main islands of Japan. Bulletin of the Biogeographical Society of Japan, vol. 15, no. 2, p. 1-4. (in Japanese) Ozaki, H., 1958: Stratigraphical and paleontological studies on the Neogene and Pleistocene formations of the Tyosi dis- trict. Bulletin of the National Science Museum, vol. 4, no. 1, p. 1-182, pls. 1-24. Pilsbry, H. A., 1904: New species of Buccinum from the Kuril Islands. Nautilus, vol. 18, no. 3, p.87-89. Rafinesque, C. S., 1815: Analyse de la nature, ou tableau de l'univers et des corps organisés, 224 p. Barravechia, Palermo. Sowerby, G. B. Ill, 1899: Descriptions of two new species of shells from Japan. Annals and Magazine of Natural History, Series 7, vol. 4, p. 370-372. Stanley, S. M., 1984: Marine mass extinction: a dominant role for temperature. In, Nitecki, M., ed., Extinctions, p.69- 117, University of Chicago Press, Chicago. Stimpson, W., 1865: Review of the northern buccinums, and remarks on some other northern marine mollusks. Part 1. The Canadian Naturalist and Geologist, New Series, vol. 2, p. 364-389. Tada, R., 1994: Paleoceanographic evolution of the Japan Sea. Palaeogeography, Palaeoclimatology, Palaeoeco- logy, vol. 108, nos. 3/4, p. 487-508. 4 Tiba, R., 1980: Description of four new species of the genus Buccinum (Buccinidae, Gastropoda). Bulletin of the Institute of Malacology, Tokyo, vol. 1, no. 5, p. 77-80, pls. 24-27. Tiba, R., 1981: Description of two new species of the genus Buccinum. Bulletin of the Institute of Malacology, Tokyo, vol. 1, no. 7, p. 110-112, pls. 37-38. Tiba, R., 1984: Description of a new species of the genus Buccinum. Bulletin of the Institute of Malacology, Tokyo, vol. 1, no. 10, p. 141-142, pl. 48. Tiba, R. and Kosuge, S., 1984: North Pacific shells (14) Genus Buccinum Linnaeus. Occasional Publication of the Institute of Malacology of Tokyo, p. 1-124. (in Japanese) Valentine, J.W. and Jablonski, D., 1991: Biotic effects of sea level change; the Pleistocene test. Journal of Geophysical Research, vol. 96, no. B4, p. 6873-6878. Verkrüzen, T.A., 1882: Buccinum, L. (Fortsetzung). Jahrbuch der Deutschen Malakozoologischen Gesellschaft, vol. 3, p. 205-221, 279-301, 356-365. Vermeij, G.J., 1991: Anatomy of an invasion: the trans-Arctic interchange. Paleobiology, vol. 17, no. 3, p. 281-307. Yokoyama, M., 1926: Fossil shells from Sado. Journal of the Faculty of Science, Imperial University of Tokyo, sec. 2, vol. 1, pt. 8, p. 249-312, pls. 32-37. 227 The Palaeontological Society of Japan has revitalized its journal. Now entitled Paleontological Research, and published in English, its scope and aims have entirely been redefined. The journal now ac- cepts and publishes any international manuscript meeting the Society’s scientific and editorial standards. 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However, figures will be returned upon request by the authors after the paper has been pub- lished. Ager, D. V., 1963: Principles of Paleoecology, 371p. McGraw- Hill Co., New York. Barron, J. A., 1983: Latest Oligocene through early Middle Miocene diatom biostratigraphy of the eastern tropical Pacific. Marine Micropaleontology, vol. 7, p. 487-515. Barron, J. A., 1989: Lower Miocene to Quatemary diatom biostratigraphy of Leg 57, off northeastern Japan, Deep Sea Drilling Project. In, Scientific Party, Initial Reports of the Deep Sea Drilling Project, vols, 56 and 57, p. 641-685. U. S. Govt. Printing Office, Washington, D. C. Burckle, L. H., 1978: Marine diatoms. In, Haq, B. U. and Boersma, A. eds., Introduction to Marine Micropaleon- tology, p. 245-266. Elsevier, New York. Fenner, J. and Mikkelsen, N., 1990: Eccene-Oligocene diatoms in the westem Indian Ocean: Taxonomy, stratigraphy, and paleoecology. /n, Duncan, R. A., Backman, J., Peterson, L. C., et al, eds.Proceedings of the Ocean Drilling Program, Scientific Results, vol. 115, p. 433-463. College Station, TX (Ocean Drilling Program). Kuramoto, S., 1996: Geophysical investigation for methane hy- drates and the significance of BSR. The Journal of the Geological Soclety of Japan, vol. 11, p. 951-958. (in Japanese with English abstract) Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey (A new find of an ammonoid jaw ap- paratus). Paleontologicheskii Zhurnal 1974, p. 127-129. (in Russian) o ae ae so 17 = sd TE PLP OBE DEDEDE ee PEPE PE PE PE PE OE PE OEP | \ \ \ \ \ \ | \ | OF151EAl&1%, 20027 1 A26H (+), 14278 (H) OMAK HKD ICRA HCE CBA S tv £9. 1 8274 (A) FRERE SE LT [21H AAPOR —HAÆME + 7 4 — 0 FFF soka- HEN, À Be ARs > FRISFRER FE TR RA FR (BI) RER LE. &rıA26H (+) Et, FELSEROFHÄERZBHB OH BR 6 (FE EL TH ET, Aa DOHLÄAFHFIE2001EI1IÄSOH (4) TH. ©2002 F2 - PS it teHHR VAS Cut) CHHRLES. BHARIS6 H FH 27 A SCHOCHHEAMBHCT. KHRHBOR LUSH IL200205A7H CK) CF. 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IE 142 Paleontological Research Vol. 5, No. 3 September 28, 2001 CONTENTS Keiichi Hayashi: Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup in northern Kyushu, Japan 5. 02080.0:0.00.0.00.0.00000000000000000000000500000000000000000000000000n0000000000c000 143 Tatsuro Matsumoto and Takemi Takahashi: Further notes on the turrilitid ammonoids from Hokkaido-Part 2 (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XC) :::::::: 163 Sanghamitra Ray: Small Permain dicynodonts from India -:::::::::::-:::-:::-.:................:: 77 Ritsuo Nomura: Quantification of optically granular texture of benthic foraminiferal walls = -- 193 Yasunari Shigeta, Yuri D. Zakharov and Royal H. Mapes: Origin of the Ceratitida (Ammonoidea) inferred from the early internal shell features DoTOO OOo OO 0 C0000000000000080000000000900600000 201 Kazutaka Amano and Mikiko Watanabe: Taxonomy and distribution of Plio-Pleistocene Buccinum (Gastropoda: Buccinidae) in northeast Japan DOODOUOOUDODODOODOD DOGO elle eee etleeee seche eee eee 215 4 Paleontological Research ISSN 1342-8144 Formerly Transactions and Proceedings of the Palaeontological Society of Japan Vol. 5 No.4 December 2001 The Palaeontological Society of Japan Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Alan G. Beu (Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato ‘(Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto Univetsity, Kyoto; Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain); Roger D. K. Thomas (Franklin and Marshall College, Lancaster, USA), Katsumi Ueno (Fukuoka University, Fukuoka, Japan), Wang Hongzhen (China University of Geosciences, Beijing, China), Yang Seong Young (Kyungpook National University, Taegu, Korea) Officers for 2001-2002 President: Hiromichi Hirano Councillors: Shuko Adachi, Kazutaka Amano, Yoshio Ando, Masatoshi Goto, Hiromichi Hirano, Yasuo Kondo, Noriyuki Ikeya, Tomoki Kase, Hiroshi Kitazato, ltaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Kei Mori, Hirotsugu Nishi, Hiroshi Noda, Kenshiro Ogasawara, Tatsuo Oji, Hisatake Okada, Tomowo Ozawa, Takeshi Setoguchi, Kazushige Tanabe, Yukimitsu Tomida, Kazuhiko Uemura, Akira Yao Members of Standing Committee: Makoto Manabe (General Affairs), Tatsuo Oji (Liaison Officer), Shuko Adachi (Finance), Kazushige Tanabe (Editor in Chief, PR), Tomoki Kase (Co-Editor, PR), Kenshiro Ogasawara (Planning), Yoshio Ando (Membership), Hiroshi Kitazato (Foreign Affairs), Haruyoshi Maeda (Publicity Officer), Ryuichi Majima (Editor, “Fossils*), Yukimitsu Tomida (Editor in Chief, Special Papers), Tamiko Ohana (Representative, Friends of Fossils). Secretaries: Fumihisa Kawabe, Naoki Kohno (General Affairs), Isao Motoyama (Planning), Hajime Naruse (Publicity officer) KazuyoshiEndo, YasunariShigeta, Takenori Sasaki (EditorsofPR), Hajime Taru (Editor of “Fossils"), Yoshihiro Tanimura (Editor of Special Papers) Auditor: Yukio Yanagisawa Notice about photocopying: In order to photocopy any work from this publication, you or your organization must obtain permission from the following organization which has been delegated for copyright for clearance by the copyright owner of this publication. Except in the USA, Japan Academic Association for Copyright Clearance (JAACC), Nogizaka Bild., 6-41 Akasaka 9-chome, Minato-ku, Tokyo 107-0052, Japan. Phone: 81-3-3475-5618, Fax: 81-3-3475-5619, E-mail: kammori@msh.biglobe.ne.jp In the USA, Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. Phone: (978)750-8400, Fax: (978)750-4744, www.copyright.com Cover: Idealized sketch of Nipponites mirabilis Yabe, a Late Cretaceous (Turonian) nostoceratid ammonite. Various reconstructions of the mode of life of this species have been proposed, because of its curiously meandering shell form (after T. Okamoto, 1988). All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16-9, Bunkyo-ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp/palaeont/ Paleontological Research, vol. 5, no. 4, pp. 229-240, December 31, 2001 © by the Palaeontological Society of Japan A study of Hypoturrilites (Anmonoidea) from Hokkaido (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XCl) TATSURO MATSUMOTO' and TAKEMI TAKAHASHI? ‘c/o The Kyushu University Museum, Fukuoka, 812-8581, Japan *28-109 Hanazono-cho, Yayoi, Mikasa, 068-2124, Japan APR 1 8 2002 \ES LIBRA Received 11 January 2001; Revised manuscript accepted 26 July 2001 Abstract. This paper presents the result of our study on the genus Hypoturrilites from the Mikasa district, Central Hokkaido. H. gravesianus (d’Orbigny, 1842), H. wrighti sp. nov., H. komotai (Yabe, 1904), H. yabei Collignon, 1964 and H. nodiferus (Crick, 1907) are described, giving new or revised diagnoses and comparisons with other species. As to H. komotai the ambiguities in the previous record of occurrence are cleared up. Hence, the described species are all early Cenomanian in age. Finally the systematic allocation of Hypoturrilites in the Turrilitidae is discussed. Key words: Cenomanian, Hypoturrilites, Mariella, Mesoturrilites, Mikasa, Turrilitidae Introduction Hypoturrilites is an important genus of the Turrilitidae and more than a dozen species have been reported from various regions of the world. In Japan a magnificent specimen was described long ago under the name Turrilites komotai Yabe, 1904. It is nowadays referred to this genus. Recently H. aff. mantelli (Sharpe, 1857) and H. primus Atabekian, 1985 have been reported to occur in the lower Cenomanian of the Shuparo Valley, central Hokkaido (Matsumoto, 2000). In this paper materials from the Mikasa district are studied. The Cenomanian rocks exposed in the Ikushunbetsu Valley of this district represent a generally shallower facies in com- parison with those in the Shuparo Valley. As to the Cenomanian stratigraphy in the type section of this area readers may refer to the note by Matsumoto (1991, p. 3-5, 21-24). A supplementary note is given to a particular case concerned. The materials of this study depend primarily on the collec- tion of T. T. with an addition by Tamotsu Omori. The de- scribed specimens are to be held in the Kyushu University Museum with registered numbers under the abbreviated heading GK. One specimen of UMUT [the University Museum, the University of Tokyo] described by Yabe (1904) is restudied. For brevity the following abbreviations are used in the de- scription: D = diameter, B = breadth and H = height of the preserved last whorl; d = diameter of the whorl preceding the last one, h = height of the exposed outer face of the same whorl as above. Systematic descriptions Order Ammonoidea Zittel, 1884 Suborder Ancyloceratina Wiedmann, 1966 Superfamily Turrilitoidea Gill, 1871 Family Turrilitidae Gill, 1871 Genus Hypoturrilites Dubourdieu, 1953 Type species.—Turrilites gravesianus d’Orbigny (1842, p. 596, pl. 144, figs. 3-5) by original designation (Dubourdieu, 1953, p. 44). Diagnosis.—More or less large, sinistrally coiled turreted shell, with high or low apical angle. Whorls in tight contact, showing convex flanks and deeply impressed interwhorl junction. Each whorl ornamented by a first row of major tu- bercles at about midflank and closely set second and third rows of more numerous, spirally elongated minor tubercles in the lower part of the flank. The basal surface of the whorl ornamented by radial ribs, with minor tubercles of a fourth row on its margin. Septal suture highly indented, with L at about the concave zone below the row of major tubercles. Elongated branches of the inner element (|) extend to the zone of L (see Figures 2, 7; also Atabekian, 1985, pl. 23, fig. 1). Discussion.—The systematic position of Hypoturrilites in the Turrilitidae is debatable. We intend to discuss this prob- lem after completing the descriptions of species. Occurrence.—This genus is widespread in the lower Cenomanian of Europe (except for Northern Europe), West and Central Asia, the Middle East, North Africa, South Africa, Madagascar, South India, North Australia, New 230 Tatsuro Matsumoto and Takemi Takahashi Figure 1. A-C. Hypoturrilites gravesianus (d’Orbigny, 1842). Two lateral (A and B, 180° apart each other) and basal (C) views of GK. H8543, x 1.5. D-G. Hypoturrilites wrighti sp. nov. Three lateral (D, E and F, 90° apart successively) and basal (G) views of GK. H8544 (holotype), x 1.25. Photos coutesy of M. Noda. Hypoturrilites from Hokkaido = Zealand, Japan, Mexico and the U. S. Gulf Coast and Argentina. It seems to range upward to the middle Cenomanian in North Australia and North Africa (Wright and Kennedy, 1996, p. 364). Hypoturrilites gravesianus (d'Orbigny, 1842) Figure 1A-C Turrilites tuberculatus Mantell, 1822, p. 124 (pars), pl. 24, fig. 6. Turrilites gravesianus d'Orbigny, 1842, p. 596, pl. 144, figs. 3-5. Hypoturrilites gravesianus (d'Orbigny). Dubourdieu, 1953, p. 44; Wright and Kennedy, 1996, p. 364, pl. 102, fig. 10; pl. 105, figs. 1-6; pl. 110, figs. 2, 8, 9; pl. 111, fig. 6; pl.112, figs. 1, 3; pl. 113, figs. 1, 2, 5, 7, 10-12; text-figs. 134R; 140J, R; 141E; 145F; 147E-G (with full synonymy). Type.—The complex status of the type material of this species is explained in detail by Wright and Kennedy (1996, p. 365) and not repeated here. We agree with them in their proposal to designate BMNH C5726b as the lectotype of this species. It was illustrated by Mantell (1822, pl. 24, fig. 6) under Turrilites tuberculatus, but it is a well preserved syntype of d’Orbigny’s species (Wright and Kennedy, 1996, pl. 113, fig. 10). We support them (Wright and Kennedy, 1996, p. 363) in favour of their application to the International Commission to designate T. gravesianus d'Orbigny instead of T. giganteus Haan, 1825 (p. 75) as type species of Hypoturrilites. Material. —GK. H8543 [= previous S.36-5-14] (Figure 1A- C) collected by T. T. in 1951 at Loc. Ik1054 of the Ikushunbetsu River, from the Mantelliceras japonicum Zone. Description.—This specimen is small and probably repre- sents a young shell which corresponds to the unpreserved early part of the lectotype. Although the shell is destroyed at its top, the apical angle is roughly estimated as about 20°. The specimen preserves seven whorls which are in tight contact, showing a deeply impressed interwhorl junction. The flank of the whorl is convex and its height is less than half of the whorl diameter (h/d = 0.43). Each whorl is ornamented by a row of large, rounded tu- bercles at about midflank and two rows of small, somewhat clavate tubercles in the lower part immediately above and also along the lower whorl seam. There are rounded small tubercles of a fourth row on the marginal zone of the basal surface. The large tubercles number 10 to a whorl and the small ones of each row 20. A rib arises from each of the small tubercles of the fourth row and runs further on the basal surface to the umbilicus. In this specimen the rib is faintly swollen at the edge of the umbilicus. Some of the midflank large tubercles preserve a horizontally extended spine. The spine is septate at the domelike base. Suture is not exposed on this specimen. Comparison. — This specimen is identified with H. gravesianus because of the conformity in shell form and or- namentation with the lectotype and other examples illus- trated by Wright and Kennedy (1996). Occurrence.— As for material. In contrast to the abundant occurrences of this species in the Lower Chalk of southern England, number of examples is, so far, very few in Japan. m eee ey es ee ee ome ae = / | a Figure 2. Hypoturrilites wrighti sp. nov. Suture of GK. H8544 (holotype) on the exposed flank ath = 13.0 mm. Broken line = approximate position of whorl seam; dotted line = outline of tubercle and rib; E = external lobe; L = lateral lobe; U = umbili- cal lobe. Figure is about x 4. Drawing by T. M. Hypoturrilites wrighti sp. nov. Figures 1D-G; 2 Holotype. — GK. H8544 [= previous S.51-6-26] (Figure 1D-G) collected by T. T. in 1976 from a transported nodule of the seventh branch [= Shichino-sawa] of the Kami-ichino- sawa in the Ikushunbetsu Valley. The lithology and associ- ated species of the nodule suggest a derivation from the Mantelliceras japonicum Zone. Specific name.— In honour of C. W. Wright who has ac- complished a revised systematics of the Cretaceous Ammonoidea in addition to a number of other palaeontological contributions. Diagnosis.—Turreted shell with a rather small apical angle (about 20°) and tuberculate ornament like that of H. gravesianus and H. tuberculatus (Bosc, 1801), but interme- diate in the number of tubercles between them. A distinct rib extends upward from each major tubercle. Description.—This specimen is of moderate size, with D = 40 mm and H = 43 mm. It shows four whorls but lacks younger whorls and also the last part. The whorls are in tight contact, showing a deeply im- pressed interwhorl junction. The outer, exposed whorl face is convex and the whorl section is subcircular (B/H = 0.92). The height of the flank is slightly less than half of the diame- ter (h/d = 0.47). The whorl is ornamented by a first row of large tubercles at about the midflank, and three closely set rows of small tu- bercles in the lower part. The second row is slightly above and the third row just along the lower whorl seam; a fourth row is on the marginal zone of the basal surface of the whorl. The small tubercles of the second and third rows are spirally elongated, forming ridges which are separated by a narrow groove. On the basal surface radial ribs run with a gentle curvature from the tubercles of the fourth row toward the narrow umbilicus. In the upper part of the exposed whorl face a distinct rib extends upward from each major tubercle. The number of tubercles per whorl increases slightly with growth. In the middle growth stage it is 15 or 16 for the row of large tubercles and 24 or 25 for each row of small tuber- cles. Septal sutures are partly exposed, showing fairly narrow L 232 Tatsuro Matsumoto and Takemi Takahashi Figure 3. Hypoturrilites komotai (Yabe, 1904). Lateral (A) and basal (B) views of UMUT MM7458, x 0.6. Photos courtesy of M. Noda. Hypoturrilites from Hokkaido 233 in the zone between the first and second rows of tubercles (Figure 2). They are fine and deeply incised even on the preserved early whorls. The septa seem to be distantly separated. On the interspace between the two sutures, a branch of an inner element extends outward to the zone of L- Comparison.—The holotype of this species is generally similar to Hypoturrilites gravesianus and H. tuberculatus (Bosc, 1801) (redefined by Wright and Kennedy, 1996, p. 367). The number of large tubercles per whorl is about 10 to 12 in H. gravesianus and 20 or so in H. tuberculatus. It is 15 or 16 in H. wrighti. This number may vary to some extent, but the above difference is beyond that extent. In H. gravesianus and H. tuberculatus the upper part of the ex- posed whorl face is smooth, whereas in this species a dis- tinct rib extends upward from the large tubercle. Occurrence.— As for material. At present this species is represented by a single specimen. More material should be searched out to know clearly the stratigraphic range and geographical distribution of this species. Hypoturrilites komotai (Yabe, 1904) Figure 3 Turnlites komotai Yabe, 1904, p. 7, pls. 1 and 2. Hypoturrilites komotai (Yabe, 1904). Collignon,1964, p. 44, pl. 328, fig. 1468; Wright and Kennedy, 1996, p. 367, text-fig. 145C. Holotype.—UMUT MM7458 (Figure 3A, B), by monotypy, collected by Komota and described by Yabe (1904). Its original locality is questionable (see occurrence). Diagnosis.— A species of Hypoturrilites characterized by a very large apical angle and a low ratio of flank height to di- ameter in each whorl, which is ornamented by spinose large tubercles of the upper row and numerous small tubercles of the lower three rows. On the basal surface of the whorl ribs run obliquely to the umbilicus. Description.—The holotype is very large. It consists of four whorls, and several whorls of the early growth stage are not preserved. The last whorl, with D = 184 mm, is the body chamber, although its apertural part is destroyed. The esti- mated apical angle is as high as 70. Whorls are in tight contact; the ratio of flank height to diameter is very low (h/ d = 0.34), while the cross section of the last whorl is subelliptical, with breadth slightly larger than height (B/H = 1.11). The umbilicus is fairly narrow. The outer exposed whorl face shows a nearly flat and gently inclined upper portion and a convex main part. The latter is ornamented by a first row of large tubercles, num- bering 18 or 19 per whorl. In the lower part of the exposed whorl face somewhat above and along the lower whorl seam, there are the second and the third rows of small, obliquely or spirally elongated tubercles, numbering 35 or so per whorl in each row. From the small tubercles of a fourth row on the margin of the basal surface distinct ribs run to the umbilical margin with a gentle curvature (Figure 3B). The large tubercles of the first row originally had a spine which stretched laterally with a slightly upward curvature (see Yabe, 1904, pl. 1). One of us (T. M.) actually observed the spinose tubercles when he was a student at the University of Tokyo (in 1935), but later the spines were all broken and lost. At present the exposed top of a dome-shaped large tu- bercle preserves the septate base of the spine (Figure 3A). The holotype does not clearly show the suture, as it is cov- ered by a dark-colored shelly layer. We have not observed the specimen from Madagascar, but it is identified with this species on the basis of the gen- eral conformity in the estimated apical angle and number of large tubercles, as shown by Collignon (1964, p. 44, pl. 328, fig. 1468) and also by Wright and Kennedy (1996, p. 367, text-fig. 145C). It is small and probably immature because its preserved last whorl is still septate. The suture was not drawn by these authors. Comparison.—This species has diagnostic characters (vide supra), which enable us to distinguish it from other species. Comparison with H. yabei Collignon, 1964 is made below. Occurrence.—Yabe (1904, p. 9) cited Komota’s informa- tion that the holotype came from a loose marly nodule found below a cliff of the River Ikushunbetsu, directly upstream from the Coal Mine of Ikushunbetsu. The above record is, however, questionable from the stratigraphic point of view. The cliff is a part of our Locality Ik1103 (Figure 4) and has yielded numerous specimens of Calycoceras (Newboldiceras) asiaticum (Jimbo). In fact it is the type locality of “Acanthoceras rhotomagense var. asiatica’ of Jimbo (1894, p. 177, pl. 20, fig. 1). This fossiliferous part belongs to the Abundance Zone of Calycoceras (Newboldiceras) asiaticum in the present sense. At Loc. Ik1103 the beds with C. (N.) asiaticum are underlain by another fossiliferous sequence from which T. T. obtained a specimen of Cunningtoniceras (Matsumoto et al. 1969, pl. 33, fig. 2). Thus, the fossiliferous beds of Loc. Ik1103 are as a whole referred to the middle Cenomanian. They belong to the Mikasa Formation on the western wing of the Ikushunbetsu Anticline in our present knowledge. Long ago this part was called “the Lower Acanthoceras zone of the Trigonia Sandstone” and was thought to be underlain by the “Lower Ammonite Beds” (Yabe, 1903, p. 8). Incidentally, the Upper Acanthoceras Zone at that date was the Mammites-bearing bed of an early Turonian age ex- posed in the Yubari Mountains. In our present knowledge a fault of considerable magni- tude is presumed to run on the east side of Ik1103 (see Matsumoto et al., 1964, fig. 7) and middle Albian Lyelliceras- bearing strata of the Lower Yezo Subgroup are exposed for some distance (see Matsumoto, 1988, p. 157 - 158). Further upstream on the eastern wing of the Ikushunbetsu Anticline the successive ammonite zones in the middle part (i. e., the Member Ilb) of the Mikasa Formation are exposed. They are in ascending order as follows (Matsumoto et al., 1969; Matsumoto, 1991): (1) Assemblage Zone of Mantelliceras japonicum- Sharpeiceras kongo: middle part of the lower Cenomanian. (2) Ammonite-poor part, in which Acomposoceras renevieri (Sharpe, 1857) was found by T. T. (Matsumoto and Takahashi, 1992): upper part of the lower Cenomanian. (3) Subzone of Cunningtoniceras takahashii and Subzone of Calycoceras (Newboldiceras) orientale: middle Ceno- manian. 234 1103 3 Km Tatsuro Matsumoto and Takemi Takahashi 00 aye ws. See Figure 4. Outline map of the Ikushunbetsu Valley (part). The locations of Ik1103 and Ik1003 are shown. Regrettably Ik1003 (type locality of Reesidites minimus) was misprinted as Ik1103 in the paper by Matsumoto (1965, fig. 2 and explanation of pls. 14 and 15), but was correctly printed in figs. 4 and 34 of the same paper. For the geology of the mapped area see Yoshida and Kanbe (1955) and Matsuno et al. (1964), in the latter of which the distribution of the Mikasa Formation is clearly shown (Matsuno et al., 1964, fig. 7). Abbreviations in this Figure: BAN = Banno-sawa, KIK = Kikumezawa, PON = R. Ponbetsu, T = type locality of the Mantelliceras japonicum Zone. Put Ik at the heading of 1003 and 1103. The Zone of M. japonicum is prolific and several species of Hypoturrilites have been collected from this zone. Recently H. cf. komotai has been found in the same zone at a locality of the Ganseki-zawa, i. e. the 8th branch of the Kami-ichino-sawa, about 7 km northeast from the type out- crop (indicated as T in Figure 4) of this zone. The Mikasa Formation on the eastern wing consists mainly of sandstones and forms a ridge on the northwest side of the Kami-ichino-sawa and also another ridge on the southeast side of the Shimo-ichino-sawa (Figure 4). There is, thus, a high possibility that Komota’s nodule originated from the M. japonicum Zone of the Mikasa Formation ex- posed along the Shimo-ichino-sawa and was transported downstream for about 1.5 or 2 km. In Madagascar H. komotai is recorded from the lower Cenomanian (Collignon, 1964, p. 44). Hypoturrilites yabei Collignon, 1964 Figure 5 Hypoturrilites yabei Collignon, 1964, p. 44, pl. 328, fig, 1469; Wright and Kennedy, 1996, p. 367, text-fig. 145D. Holotype.— Original of Collignon, 1964, p. 44, pl. 328, fig. 1469 (by original designation), from the lower Cenomanian of Antanimanga of Madagascar. It is now housed in the col- lection of the Département des Sciences de la Terre, Univ ersité de Bourgogne, Dijon (France). Material.— GK. H8545 [= previous S. 40-9-4A] (Figure 5A-D) and GK. H8546 [S. 40-9-4B] (Figure 5B-H) collected by T. T. in 1960 at Loc. Ik1100, abandoned pit on the right side of the River Ikushunbetsu; also GK. H8528 collected by Tamotsu Omori (no. 86) from the Shimo-ichino-sawa, a branch of the Ikushunbetsu. They came from the fossiliferous sandstones referred to the Mantelliceras japonicum Zone of the Mikasa Formation. Description.— The three specimens are smaller than the holotype. The apical angle is moderate, i. e., around 50°, and h/d is rather low, 0.40-0.42. Whorls are tightly in con- tact and the interwhorl junction is deeply impressed. The outer exposed whorl face is convex. The umbilicus is nar- row. Each whorl is ornamented by an upper row of large tuber- cles at the most convex midflank and more or less spirally elongated small ones of three closely set rows in the lower part. The large tubercles number 12-13 per whorl and the small ones in each row are nearly twice as numerous as the large ones. The large tubercle has a horizontally elongated spine as shown by GK. H8546 (Figure 5E, G), but in many cases the spine is absent and its septate base is exposed, forming a rounded domelike outline (Figure 5A, B). A shallowly concave zone may be discernible below the Hypoturrilites from Hokkaido 235 Figure 5. Hypoturrilites yabei Collignon, 1964. A-D. GK. H8545, two lateral (A and B about 180° apart), apical (C) and basal (D) views. E-H. GK. H8546, two lateral (E and F about 180° apart), apical (G) and basal (H) views. Figures are allx 1.25. Photos courtesy of M. Noda. first row of large tubercles and a narrow spiral groove runs between the second and third rows of clavate tubercles. The tubercles of a fourth row are less clavate and situated at the curved outer edge of the basal rib. There are short riblets on the uppermost part of the flank above the zone of large tubercles. They are roughly twice as numerous as the large tubercles. The septal suture is partly exposed on a later whorl of GK. H8546. The stem of the E-L saddle is broad, whereas L is narrow and deep, resting on the zone between the first and second rows of tubercles. The extra branch exists but is not well traced. Comparison.—The described specimens are undoubtedly identified with H. yabei Collignon, 1964. This species is al- 236 Tatsuro Matsumoto and Takemi Takahashi lied to but distinguished from H. komotai by its somewhat made no mention of this character. smaller apical angle and less numerous tubercles. The up- Occurrence.— As for material. Despite the long distance, permost row of riblets is faintly shown in the illustration by H. yabei and H. komotai both occur in Japan and Collignon (1964, pl. 328, fig. 1469), although the author Madagascar. In Madagascar the two species have been re- Figure 6. Hypoturrilites nodiferus (Crick, 1907). A-C. GK. H8547, two lateral (A and B about 180° apart) and basal (C) views, x 1.5. D-F. GK. H5570, two lateral (D and E about 90° apart) and basal (F) views, Slightly reduced(x 0.95). G-I. GK. H5917, two lat- eral (G and H about 120° apart) and basal (I) views, x 1.25. Photos courtesy of M. Noda. Hypoturrilites from Hokkaido 237 corded from the same bed (Collignon, 1964, p. 44-45). Hypoturrilites nodiferus (Crick, 1907) Figures 6, 7 Turrilites nodiferus Crick, 1907, p. 177, pl. 11, fig. 5, 5a. Turrilites tuberculatoplicatus Seguenza var. tenouklensis Pervin- quiere, 1910, p. 57, pl. 5, fig. 31. Hypoturrilites nodiferus (Crick, 1907). Klinger and Kennedy, 1978, p. 22, pl.. 4, fig. 1; Collignon, 1964, p. 44, pl. 328, fig. 1466; Wright and Kennedy, 1966, text-fig. 145E. Hypoturrilites tenouklensis (Pervinquiere, 1910). Marcinowski, 1980, p. 261, pl.. 4, fig. 17; Atabekian, 1985, p. 61, pl. 28, figs. 152. Hypoturrilites laevigatus (Coquand, 1862). Wright and Kennedy, 1996 (pars), p. 373, pl. 102, fig. 2; text-fig. 146K-M (non 146P, Q). Holotype.—Original of Crick, 1907, p. 177, pl..11, fig. 5, 5a, BMNH C18749, by monotypy. Material.— GK. H8547 [= previous S. 51-9-25] (Figure 6A-C) collected by T. T. in 1976 from a transported nodule of the Ganseki-zawa [= the 8th branch of the Kami-ichino- sawa]; GK. H5570 [= previous S. 39-6-16] (Figure 6D-F) col- lected in 1954 by T. T. at Loc. Ik1101; GK. H5917 [= purchased, no. A003-17] (Figure 6G-I) from Loc. Ik1049; the latter two specimens were collected in situ. The three specimens belonged to the Mantelliceras japonicum Zone, lower part of the Member IIb of the Mikasa Formation. Description.— The apical angle is moderate, about 40°. The whoris are in tight contact, showing a deep junction. Each whorl has a convex flank and is subcircular in cross section. The tubercles are in four rows as in the above-described species of Hypoturrilites. The first row of large tubercles, 10 to 14 per whorl, is at about or slightly below the midflank. On the exposed whorl face there are numerous transverse ribs, which are individually variable in density and number, ranging from 30 to 40 per whorl. They are weakened but run adorally across the shallowly concave zone below the Figure 7. Hypoturrilites nodiferus (Crick, 1907). Suture of GK. H5570 on the flank ath = 14 mm. Legend as for Figure 2. Figure is about x 3. Drawing by T. M. row of large tubercles. Slightly above and just along the lower whorl seam there are the second and third rows of clavate, minor tubercles. They form the spiral ridges, with a narrow but distinct groove between them. The small tu- bercles of the fourth row are on the marginal zone of the basal surface, where radial ribs run to the umbilicus. The tubercles in each of the lower rows are approximately as nu- merous as the transverse ribs, but the exact correspon- dence in number may not be maintained as is shown on an undestroyed part of GK. H5570 (Figure 6D) and on the well preserved specimen from Madagascar (Wright and Kennedy, 1996, text-fig. 145D). The radial ribs on the basal surface are exactly as numerous as the small tubercles of the fourth row. Often a narrow riblet extends obliquely up- ward from the fourth tubercle to the third one. The septal suture (Figure 7) is similar to that of other spe- cies of Hypoturrilites. Comparison and discussion.—As there are some ambigu- ous points in some of the previously described taxa, discus- sion is given along with comparison. The holotype of this species from South Africa is represented by a single whorl. It was described at length by Klinger and Kennedy (1978, p. 22, pl. 4, fig. I), but they did not mention clearly the tubercles of the fourth row, which Crick (1907, p. 177) did mention and one of us (T. M.) confirmed on the original specimen. On the weathered part or when the lighting is inadequate, the small tubercles of the fourth row are scarcely discernible. This species is represented by a better preserved specimen of Collignon (1964, p. 44, pl. 328, fig. 1466; Wright and Kennedy, 1996, text-fig. 145E) from Madagascar. The holotype of Turrilites tuberculoplicatus Seguenza var. tenouklensis Pervinquiere (1910, p. 57, pl..14, fig. 31) (reillustrated by Wright and Kennedy, 1996, text-fig.146K- M), from the lower Cenomanian of Algeria, was referred to H. laevigatus (Coquand, 1862) by Wright and Kennedy (1996, p. 373). In our view it should be regarded as an ex- ample of H. nodiferus because of the resemblance in essen- tial characters. The holotype of Turrilites laevigatus Coquand (1862, p. 175, pl. 2, fig. 6) (reillustrated by Wright and Kennedy, 1996, text-fig. 146P, Q) is too much worn for the accurate definition of the species. It is estimated to have a taller shell shape with a higher h/d and a smaller apical angle in comparison with H. tenouklensis [= H. nodiferus]. The specimen from Crimea (Ukraine) which was identified with H. tenouklensis by Marcinowski (1984, p. 261, pl.. 4, fig. 17) undoubtedly shows three rows of small tubercles. It is probably another example of H. nodiferus. MH. tuberculatoplicatus (Seguenza, 1882, p. 53, pl. 5, fig. 3), from the lower Cenomanian of Italy and England (Wright and Kennedy, 1996, p. 374, pl. 102, fig. 7; pl. 113, figs. 2, 6, 8, 9), has three rows of small tubercles as in H. nodiferus. It shows, however, a much taller shell shape with smaller api- cal angle and a higher value of h/d in comparison with H. nodiferus. In this respect, one of the British specimens illus- trated by Wright and Kennedy (1996, pl. 113, fig. 4) might be H. nodiferus rather than H. tuberculatoplicatus. If the large tubercles are excluded, H. nodiferus is consid- erably similar to Mesoturrilites corrugatus Wright and Kennedy (1996, p. 348, pl. 98, figs. 4, 17), from the lower 238 Tatsuro Matsumoto and Takemi Takahashi Figures 8. Mesoturrilites aff. corrugatus Wright and Kennedy, 1996. Lateral (A) and basal (B) views of GS. G260, x 1. Photos courtesy of M. Noda. Cenomanian of England. Inthe same respect, we notice an interesting specimen (Figure 8) in the recent collection of Y. Kawashita (YKC111019) (registered at Saga University GS. G260) from the lower Cenomanian part of the Mikasa Formation in the Ganseki-zawa. It is tentatively called Mesoturrilites aff. corrugatus, for its ribs and small tubercles in three rows are more numerous than those of the British specimens. As to the rib density, however, there may be variation with growth and also between individuals. At any rate, this specimen (GS. G260) resembles GK. H8517 of H. nodiferus, if the large tubercles of the latter are ignored. Some of the transverse ribs are strengthened at or below the midflank in this specimen (GS. G260), if not forming tuber- cles as in Mesoturrilites serpuliforme (Coquand, 1862, p. 175, pl. 2, fig. 7) (see also Wright and Kennedy, 1996, p. 348, pl.. 98, fig. 10; pl. 102, fig. 5; text-figs. 138P-R, X; 146H-J). Occurrence.—As for material. Distribution.—If the above comments are accepted, this species is recorded widely from the lower Cenomanian of South Africa, Madagascar, North Africa, England (?), Ukraine, Azerbaijan, and Japan. Systematic allocation of Hypoturrilites in the Turrilitidae When Dubourdieu (1953, p. 41, fig. 13) established the genus Hypoturrilites, he was not confident about its system- atic position in the family Turrilitidae. He tentatively indi- cated it as one of the divergences from Pseudhelicoceras in parallel with Mariella [= “Paraturrilites’ in his paper] and Ostlingoceras. At about the same time, but probably after the appearance of Dubourdieu’s paper, Mesoturrilites was proposed by Breistroffer (1953, p. 1351). Its type species, M. aumalensis (Coquand, 1862), is somewhat similar to Hypoturrilites in having an upper row of fairly large tubercles at about the midflank and three rows of small tubercles in the lower part. In many species of Hypoturrilites, however, the large tubercles of the upper row at about the midflank are less numerous than the small ones in each of the lower three rows. In M. aumalensis and many other species of Mesoturrilites the small tubercles in each row are equal in number to the large ones of the upper row. In morphologi- cal terms the typical species of Mesoturrilites can be re- garded as a development of Mariella in which the ribbing was reduced and the tubercles in the lower rows are spirally elongated, as Wright and Kennedy (1996, p. 346) mentioned as one of the possible cases. In some other cases the rib- bing remained in such ways as in Mesoturrilites boerssumensis (Schlüter, 1876), M. serpuliforme (Coquand, 1862) and M. aff. corrugatus. The latter subgroup of Mesoturrilites is fairly similar to H. nodiferus or to H. tuberculatoplicatus, in which, however, the midflank tuber- cles are enlarged and reduced in number. The relationship of Hypoturrilites with Mariella takes a more definite shape. An actual morphological, if not phylogenetical, transition is observed between such a form of Mariella (M.) bergeri (Brongniart, 1822) as illustrated by Kennedy (1996, fig. 28p, 0) from the uppermost part of the Albian and the typical form of Hypoturrilites primus Atabekian (1985, p. 60, pl. 16, fig. 1; pl. 17, fig. 1; Matsumoto, 2000, p. 6, fig. 2-3) from the lower Cenomanian. Hypoturrilites betaitraensis Collignon, 1964 (p. 13, pl. 320, figs. 1387, 1388) (Wright and Kennedy, 1996, p. 375, pl. 102, fig. 12; text-fig. 134F-I), from the lower Cenomanian of Madagascar, South Africa, Algeria, West Europe and Turkmenistan, shows a pair of delicate ribs, of which one runs from the large tubercle upward to the interwhorl junction while the other is intercalatory between the large tubercles. Its small tubercles are conical or obliquely clavate as in many species of Mariella. The riblets similar to the above- mentioned delicate ribs are discernible and the small tuber- cles of the second and third rows are spirally elongated in H. yabei. Although the details of the phylogenetical relations are practically unknown, it is interesting to note that Mariella ex- tended from the Albian to tne Cenomanian and that numer- ous species of Hypoturrilites and several species of Mesoturrilites evolved almost simultaneously in early Cenomanian time. Conclusions (1) In this paper Hypoturrilites is studied based on materi- als from the Ikushunbetsu Valley of the Mikasa district. As a result, H. gravesianus (d’Orbigny, 1842), H. wrighti sp. nov., H. komotai (Yabe, 1904), H. yabei Collignon, 1964, and H. nodiferus (Crick, 1907) are distinguished. (2) In addition to the establishment of a new species , H. wrighti, the revised descriptions have made clear the distinc- tion between H. komotai and H. yabei. H. nodiferus was pro- posed long ago on the basis of a fragmentary whorl but it is now well defined, showing its diagnosis, variation, and affini- ties with other species. (3) Doubts about the occurrence of H. komotai are cleared up by ascribing its derivation to a lower Cenomanian bed. Thus, the number of described species from Hokkaido, in- cluding the recently reported H. aff. mantelli (Sharpe, 1857) and H. primus Atabekian, 1985 from the Shuparo area (Matsumoto , 2000), is altogether seven, about half of the described species from various regions of the world. (4) The systematic allocation of Hypoturrilites in the family Hypoturrilites from Hokkaido Turrilitidae is discussed. As a conclusion, numerous spe- cies of Hypoturrilites seem to have evolved almost simulta- neously from Mariella in the early Cenomanian age. At about the same time several species of Mesoturrilites may have evolved also from Mariella. A few atypical species of Hypoturrilites show a morphologically intermediate appear- ance between typical Hypoturrilites and Mesoturrilites. Acknowledgements Kazushige Tanabe and Takeo Ichikawa offered every fa- cility for the restudy of the type specimen at the Museum of the University of Tokyo. Photos in this paper were all taken by Masayuki Noda. Tamotsu Omori and Yoshitaro Kawashita provided the specimens for this study. Two anonymous referees helped us to improve the manuscript. We thank all of these persons for their kindness. References Atabekian, A. A, 1985: Turrilitids of the late Albian and Cenomanian of the southern part of the USSR. Academy of Sciences of the USSR, Ministry of Geology of the USSR, Transactions, vol. 14, p. 1-112, pls. 1-34. (in Russian) Bosc, J. A., 1801: In, Buffon, G. L. Leclerc, Comte de, Histoire Naturelle des Coquilles, 5, 395 p. Paris. Breistroffer, M., 1953: L'évolution des Turrilitides albiens et cenomaniens. Compte Rendus Hebdomadaires des Sciences de l'Académie des Sciences, vol. 237, p. 1349-1351. Brongniart, A, 1822: In, Cuvier, G. and Brongniart, A., Description géologique des environs de Paris, 428 p., 24 pis. Collingnon, M., 1964: Atlas des fossiles caracteristiques de Madagascar (Ammonites), Fascicle 11 (Cenomanien), p. 1-152, pls. 318-375. Service Géologique, Tananarive. Coquand, H., 1862: Géologie et paléontologie de la région sud de la Province de Constantine. Mémoires de la Société d’Emulation de la Province, Marseille, voi. 2, p. 1-320, 321-341 (supplement), pls. 1-35. Crick, G. C., 1907: Cretaceous fossils of Natal. /n, Anderson, W., Third and Final Report of the Geological Survey of Natal and Zululand, p. 161-250, pls. 10-15, London. Dubourdieu, G., 1953: Ammonites nouvelles des Monts du Mellegue. Bulletin du Service de la Carte Geologique de l'Algérie, ser, 1, Paléontologie, vol. 16, p. 1-76, pls. 1-4. Gill, T., 1871: Arrangements of the families of Mollusks. Smithsonian Miscellaneous Collections, no. 227, p. i-xvi, 1-49. Haan, G. de, 1825: Specimen Philosophicum Inaugurale, Exhibens Monographiam Ammoniteorum et Goniatiteo- rum, viii +168 p., London. Jimbo, K, 1894: Beitrage zur Kentniss der Kreideformation von Hokkaido. Palaeontologische Abhandlungen, neue Folge, vol. 2, p.147-194, pls. 17-25. Kennedy, W. J., 1996: Systematic palaeontology. In, Gale, A. S. et al, The Late Albian to Early Cenomanian Succession at Mont Risou near Rosans (Drome SE France): an Integrated Study (Ammonites, Inoceramids, Plankton Foraminifera, Nannofossils, Oxygen and Carbon Isotopes ). Cretaceous Research, vol. 17, p. 543-590. Klinger, H. C. and Kennedy, W. J., 1978: Turrilitidae (Cretaceous Ammonoidea) from South Africa, with a dis- cussion of the evolution and limits of the family. Journal of Molluscan Studies, vol. 44, p. 1-48. Mantell, G. A., 1822: The Fossils of the South Downs, or Illustration of the Geology of Sussex, xiv + 328 p., 43 pls. L. Rolfe, London. Marcinowski, R., 1980: Cenomanian ammonites from German Democratic Republic, Poland and Soviet Union. Acta Geologica Polonica, vol. 30, p. 215-325, pls. 1-20. Matsumoto, T., 1965: A monograph of the Collignoceratidae from Hokkaido. Part 1. Memoirs of the Faculty of Science, Kyushu University, ser. D, vol. 16, p. 1-80, pls. 1-18. Matsumoto, T. (compiled), 1988: A monograph of the Puzosiidae (Ammonoidea) from the Cretaceous of Hokkaido. Palaeontological Society of Japan, Special Papers, no. 30, p. i-iii + 1-179. Matsumoto, T. (compiled), 1991: The mid-Cretaceoue am- monites of the family Kossmaticeratidae from Japan. Palaeontological Society of Japan Special Papers, no. 33, p. i-vi+ 1-143, pls. 1-31. Matsumoto, T., 2000: /n, Matsumoto, T., partly with Takashima, R. and Hasegawa, K., Some turrilitid amnonoids from the mid-Cretaceous of the Shuparo Valley, Central Hokkaido. Bulletin of the Mikasa City Museum, Natural Science, no. 4, p. 1-13. Matsumoto, T., Muramoto, T. and Takahashi, T., 1969: Selected acanthoceratids from Hokkaido. Memoirs of the Faculty of Science, Kyushu University, Series D, vol. 19, p. 251-296, pls. 25-38. Matsumoto, T. and Takahashi, T., 1992: Ammonites of the genus Acompsoceras and some other acanthoceratid species from the Ikushunbetsu Valley, central Hokkaido. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no.166, p. 1144-1156. Matsuno, H., Tanaka, K., Mizuno, A. and Ishida, M., 1964: Iwamizawa. Explanatory Text of the Geological Map of Japan, Scale 1 : 50,000, 168 p.+ 11 p., Quadrangle Map. Hokkaido Development Agency, Sapporo. (in Japanese with English abstract) Orbigny, A. d’, 1842: Paléontologie frangaise. Terrains creta- cés, 1, Céphalopodes, p. 431-662, Mason, Paris. Pervinquiere, L., 1910: Sur quelques ammonites du Crétacé algérien. Mémoires du la Société Géologique de France, Paléontologie, vol. 17, mémoire 42, p. 1-86, pls. 1-7. Schlüter, C., 1876: Cephalopoden der oberen deutschen Kreide. Palaeontographica, vol. 24, p. 121-264, pls. 36-55. Seguenza, G., 1882: Studii geologici e paleontologici sul cretaceo medio dell'ltalia meridionale. Memorie dell’Ac- cademia Pontificia dei Nuovi Lincei, voi, 12, p. 1-152, pls. 1-21. Sharpe, D., 1857: Description of the fossil remains of Mollusca found in the Chalk of England. Cephalopoda, part 3. Palaeontographical Society, 1856,London, p. 37-68, pls. 17-27. Wiedmann, J., 1966: Stammesgeschichte und System der posttriadischen Ammonoideen, ein Überblick, 1 Teil. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, vol. 125, p. 49-79, pls. 1-2. Wright, C. W. and Kennedy, W. J., 1996: The Ammonoidea of the Lower Chalk, part 5. Monograph of the Palaeonto- graphical Society, London, no. 601, p. 320-403, pls. 95- 239 240 124. Yabe, H., 1903: Cretaceous Cephalopoda from the Hokkaido, part 1. Journal of the College of Science, Imperial University of Tokyo, vol. 18, no. 2, p. 1-55, pls.1-7. Yabe, H., 1904: Cretaceous Cephalopoda from the Hokkaido, part 2. Journal of the College of Science, Imperial University of Tokyo, vol. 20, no. 2, p. 1-45, pls.1-6. Yoshida, T. and Kanbe, N., 1955: /kushunbetsudake. Expla- Tatsuro Matsumoto and Takemi Takahashi natory Text of the Geological Map of Japan, Scale 1: 50,000, p. 1-31, Quadrangle Map. Hokkaido Develop- ment Agency, Sapporo. ( in Japanese with English ab- stract) Zittel, K. A. von, 1884: Cephaloda, /n, Zittel, K. A.: Handbuch der Paläontologie, vol. 1, p. 329-522, Oldenbourg, Mün- chen & Leibzig. Paleontological Research, vol. 5, no. 4, pp. 241-257, December 31, 2001 © by the Palaeontological Society of Japan Late Miocene ostracodes from the Kubota Formation, Higashi-Tanagura Group, Northeast Japan, and their implications for bottom environments TATSUHIKO YAMAGUCHI’ and HIROKI HAYASHI? "Graduate School of Natural Science and Technology, Kanazawa University, Kakumamachi, Kanazawa, Ishikawa Prefecture, 920-1192, Japan (e-mail: tyamagu @nihonkai.kanazawa-u.ac.jp) “Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai, Miyagi Prefecture, 980-8578, Japan (e-mail: rin@mail.cc.tohoku.ac.jp) Received 23 May 2001; Revised manuscript accepted 16 August 2001 Abstract. Sixty-seven ostracode species including those in open nomenclature are identified in thirty-six samples from the upper Miocene Kubota Formation, Higashi-Tanagura Group, distributed in Fukushima Prefecture, northeastern Japan. The lower part of the Kubota Formation yields Spinileberis sp. dominantly. In the middle to upper part of the formation, dominant species are Schizocythere kishinouyei (Kajiyama), Kotoracythere abnorma Ishizaki, Hanaiborchella triangularis (Hanai), Cytheropteron miurense Hanai, Paracytheridea neolongicaudata Ishizaki and Finmarchi- nella japonica (Ishizaki). Most of these species live off southwestern Japan under a subtropical to warm marine climate regime, but cryophilic and circumpolar species also occur sparsely in the middle to upper part. The ostracode assemblages indicate that the lower and the middle to upper parts of the Kubota Formation were deposited in an enclosed inner bay influenced by warm water and a warm shallow sea, respectively. Principal component analysis reveals that the influence of open sea water became strong in the upward sequence of the middle part. Analyses of ostracode faunas indicate that the Shiobara fauna from the Kubota Formation flourished in warm-water condi- tions. Key words: Kubota Formation, Late Miocene, Ostracoda, Shiobara fauna Introduction The Kubota Formation is known as one of the units con- taining the Shiobara fauna (Iwasaki, 1970), which flourished in Northeast Japan during the middle to late Miocene. Chinzei and Iwasaki (1967) and Iwasaki (1970) consid- ered that the Akasaka and Kubota Formations of the Higashi-Tanagura Group were deposited contemporane- ously in an inner bay. Furthermore, these authors recon- structed a Higashi-Tanagura Bay on the basis of the lithology and geometry of the basin, discussing the paleoecology of the molluscan assemblages. In their dis- cussion, Chinzei and Iwasaki (1967) compared the molluscan assemblages in the eastern Tanagura area with ones belonging to the Kadonosawa and Tatsunokuchi fau- nas, and recognized parallel communities. Iwasaki (1970) made a comparison with the molluscan assemblages in the eastern Tanagura, Shiobara, and Takasaki areas, where nearly contemporaneous deposits are distributed. Consequently, he recognized parallel communities between them and defined the Shiobara-type fauna (Shiobara fauna). The Shiobara fauna was defined as a cold-water fauna which lived in inner bays or coastal areas (e.g. Chinzei, 1963; Chinzei and Iwasaki, 1967; Chinzei, 1986). Recently some workers, however, pointed out that the fauna flour- ished in warm- to mild-temperate realms rather than cold- temperate ones, or contained warm-water species as well as cold-water ones (e.g. Ogasawara et al., 1985; Ogasawara, 1994; Ozawa et al., 1996). Thus, the Shiobara fauna has been studied by many workers paleoecologically. Many studies on the Miocene paleoenvironments have been made using molluscan fossils. For example, Chinzei (1986) and Ogasawara (1994) summarized the molluscan faunas of the late Cenozoic of Japan in the light of paleoclimates. Chinzei (1986) stated that Northeast Japan was influenced by cold water during the middle to late Miocene, since he regarded the Shiobara fauna as a cold- water fauna. On the other hand, Ogasawara (1994) thought 242 Tatsuhiko Yamaguchi and Hiroki Hayashi LEGEND bs Nikogi Fm. key bed (Kt- )/ | ++++++++ ++++++++ FE Akasaka Fm. [885] [eo 3] Haguroyama aa a! Conglomerate basement rocks © Le] Le] Le] Le] Le] Le) Ht Ht ete tte spammer 0 rer LIEN CID EER EE CREELE : ee 5 ee eee : een rrr sss 0 2Km EE | Figure 1. Geological sketch map and geological cross section of the eastern Tanagura area. Partly modified after Shimamoto et al. (1998) for the geological map. Late Miocene ostracodes Formation (thickness) Pr! PELE LE LEI, LEE PETA LT AS ane Nikogi Fm. (110m +) Bernstein Formation (ca. 250m) F 2x SF 7 0 | shell FRE fine- with Akasaka Formation (ca. 250m) Aal: Rocks fine-grained sandstone conglomera and granitic roc + N NN N NN NN NN alternating tuff and sandstone 243 Radiometric Lithology inınnn 10.6#0.3 Ma (lo error; F.T. age) (2 grained sandstone mudpipe (1 Gerror; K-Ar age) 10.7+0.2 Ma (1 Gerror; F.T. age) shell fossils te cataclastic, metamorphic ks (1) Takahashi er al. (2001) (2) Takahashi er al. (in press) (3) Shimamoto er al. (1998) (4) Yanagisawa er al. (2000) Figure 2. Diagram showing the Neogene sequence in the eastern Tanagura area and biostratigraphy and radiometric ages of tuff layers of the Kubota Formation. Compiled after Shimamoto et al. (1998) and Yanagisawa et al. (2000) for biostratigraphy and Takahashi et al. (2001) and Takahashi et al. (in press) for radiometric ages. that marine climates in Northeast Japan were warm- to mild- temperate during the middle to late Miocene, based on the modern distribution of molluscan genera and the marine zoogeographic divisions of Nishimura (1981). Paleocli- mates suggested by molluscan fossils have been based on their biogeography and phylogeny. However, only a few studies have been made on other fossil groups from depos- its yielding the Shiobara fauna. To approach the problems mentioned above, we quantita- tively examined ostracodes from the upper Miocene Kubota Formation of the Higashi-Tanagura Group. Geological setting The eastern Tanagura area lies about 70 km south of Fukushima City, Fukushima Prefecture, northeastern Japan (Figure 1). The geology of the eastern Tanagura area has been stud- ied by many workers (e.g., Chinzei and Iwasaki, 1967; Iwasaki, 1970; Otsuki, 1975; Shimamoto et al., 1998). The Miocene distributed in the eastern Tanagura area comprises two formations: the Akasaka and Kubota Formations (Figures 1, 2). The Kubota Formation overlies conformably the Akasaka Formation and is overlain unconformably by the Pliocene Nikogi Formation. On the basis of lithology, the Kubota Formation is divided into three parts (Shimamoto et al., 1998): the lower part is composed of muddy fine-grained sandstone, yielding abundant molluscan fossils, and me- dium- to coarse-grained sandstone; the middle part muddy fine-grained sandstone with mud-pipes and tuffaceous sand- stone; the upper part cross-bedded coarse-grained sand- stone. Many felsic tuff layers are intercalated in the middle to upper part, in which Shimamoto et al. (1998) recognized seven layers as keybeds (Kt-1 to Kt-7 tuff layers). The geological age of the Kubota Formation has been de- termined by means of planktonic microfossils and radiomet- ric dating of tuff layers (e.g. Aita, 1988; Takahashi and Amano, 1989; Taketani and Aita, 1991; Shimamoto et al., 1998; Yanagisawa et al., 2000; Takahashi et al, 2001; Takahashi et al., in press). Shimamoto et al. (1998) verified that the middle and upper parts of the Kubota Formation can be assigned to the calcareous nannofossil Zone CN6 to CN7/8a of Okada and Bukry (1980), planktonic foraminifer Zone N16 of Blow (1969) and the radiolarian Lychnocanoma magnacornuta Zone of Motoyama and Maruyama (1996). Yanagisawa et al. (2000) studied the diatom assemblages from the Kubota Formation for the first time and correlated the middle part with the diatom Zone NPD5C of Yanagisawa and Akiba (1998) (Figure 2). On the other hand, Takahashi et a/. (2001) dated the ra- diometric ages of a biotite-rich tuff layer, recognized as a keybed, the Kt-1 tuff layer, by Shimamoto et al. (1998). They reported the zircon fission-track age (F.T. age) and biotite potassium-argon age (K-Ar age) of the Kt-1 tuff layer to be 10.7+0.2 Ma (1 © error) and 10.6#0.2 Ma (1 o error). Moreover, Takahashi et al. (in press) dated the zircon fis- 244 Tatsuhiko Yamaguchi and Hiroki Hayashi LÉ. Ber > 14 N IR ie A} ù IK AIN = | = 7 7 AL = a En ER. 2 ay AK Y \ FI & VA) LS S \ yy RTS —" iat rare 5 Te > / NE ETS à on iP) SEEN, | D { =, oh \ Hl ZERO A Ÿ a S R SU SS 212 1997 , CY NK2607 SN) | | TE] OT ANK2 HANAN. > te NE à ze K11 2 | IR nm - NA = NK10° ii 7) UN ie Y IK SS TD SUR UMTS on PNA AW 1 of WEN ID N SO ND IN x Up WLS \ alle Figure 3. Map showing the ostracode fossil localities (a part of 1:25,000 map of “Tanagura” and “Hanawa” published by Geographical Survey Institute of Japan). 70 65 55 45 20 Kubota Formation a (=) Akas Formation Figure 4. Columnar sections of the Kubota Formation. this study. NK21* NK20* NK19* NKI8* NKI17* NKI6* NKI5 NKI4* NK13 NK12* NKII* NKI10* NK9 NK8 NK4 150 145 135 125 120 115 110 105 95 85 Late Miocene ostracodes NK40* NK39* NK38* Nishikawa section Fa A EUR thickness (m) NK35* Kt- NK34.5* 200 NK34* 195 NK33* 190 NK32* ch 185 NK31* Kt-5 | == 180 NK30 k= NK29* 175 NK28* NK27* 170 shell fossils NK26* LE À shell fossils tf NK25* 160 I] siltstone Fasssg Ve nu F4 very fine- to fine-grained rn sandstone tf 4 ; SZ NK23* fine- to medium-grained a sandstone —= medium- to coarse-grained === sandstone mo DIE ; 22 very coarse-grained sandstone NK22 granule conglomerate ii ——ık5 sample horizon vuuuv tf ——NK20* ostracode-bearing sample horizon Kamitoyo section thickness (m) scoria pumice glassy tuff mafic mineral- bearing crystalline tuff lamination cross-bedding convolution concretion bioturbation mud pipe (Rosselia) thin tuff layer 245 Bold italic numbers with asterisk marks indicate the ostracode samples in 246 Tatsuhiko Yamaguchi and Hiroki Hayashi sion-track age of a felsic tuff, Kt-7, to be 10.6+0.3 Ma (1 © error) (Figure 2). These reported microfossil and radiomet- ric ages do not contradict the biochronology of Saito (1999). Materials and methods We collected 60 sediment samples from two sections of the Kubota Formation (Figures 3, 4) and examined 40 sam- ples: 33 samples from the Nishikawa section and 7 samples from the Kamitoyo section. The Nishikawa secticn along the Nishikawa River is typical of the Kubota Formation (Shimamoto et al., 1998). The upper part is better exposed in the Kamitoyo section along the Hokkawa River. We col- lected sediment samples from the Kamitoyo section to ex- amine fossil ostracodes from the upper part of the Kubota Formation. These two sections are well correlated to each other by virtue of five keybeds. Eighty grams of dried sediments were treated by using a saturated sodium sulfate solution and naphtha (Maiya and Inoue, 1973; Oda, 1978), washed through a 200 mesh sieve screen, and dried again. These procedures were repeated until the whole sediment sample became disintegrated. A fraction coarser than 125um (115 mesh) was sieved and di- vided by a sample splitter into aliquot parts, from which 100 to 200 individuals were picked with a fine brush under the binocular microscope. We took micrographs with a JEOL Field Emission Scanning Electron Microscope, JSM-6330F to identify the taxonomic relationships of the fossil ostracodes (Figures 5, 6). The results of our identifications are listed in Figure 7. In this figure, the estimated preserva- tion of ostracodes in each sample is as follows: good means the sample contained abundant specimens easily identified to species level; poor, the sample contained mostly speci- mens identified with difficulty to species level; moderate indi- cates somewhere between good and poor. We examined ostracode assemblages in detail from those samples, each represented by more than fifty individuals by means of the proportions (relative abundance) of major spe- cies, species diversity and equitability and performed princi- pal component analysis on data for abundance of major forty species. Ostracode assemblages from the Kubota Formation Ostracodes occurred in 36 samples and did not occur in 4 samples (samples NK1, 17, 18 and 45). We identified 67 ostracode taxa including those left in open nomenclature (Figure 7). The ostracode assemblages from the Kubota Formation can be distinctly divided into two groups (Figure 8). In the lower part of the formation, Spinileberis sp. accounts for more than 90% of the assemblage. The genus Spinileberis has been reported to occur abundantly on muddy bottoms in Recent enclosed inner bays (e.g. Hanai, 1961; Ikeya and Shiozaki, 1993). In the middle to upper part, Schizocythere kishinouyei (Kajiyama), Kotoracythere abnorma Ishizaki, Hanaiborchella triangularis (Hanai), Cytheropteron miurense Hanai, Paracytheridea neolongicaudata Ishizaki, Finmarchinella ja- ponica (Ishizaki) and so on occurred. S. kishinouyei occurs most dominantly, forming 20 to 40% of the number of speci- mens in the assemblage. Subordinate are K. abnorma and H. triangularis, accounting for 10 to 20% of the number of specimens in the assemblage. Other species represent less than 10%. Most species are reported to live in coastal areas and the open sea under the influence of the Kuroshio Warm Current (e.g. Hanai, 1957, 1970; Ishizaki, 1981; Zhou, 1995; Tsukawaki et al., 1997, 1998). All of these species are known to represent the Shiobara fauna (Ishizaki, 1966; Irizuki and Matsubara, 1994, 1995; Ishizaki et al., 1996; Irizuki et a/., 1998). Through the upper horizons of the mid- die part to the upper part, the relative abundance of Kotoracythere abnorma increases (Figure 8). Faunal structures The faunal structures of ostracode assemblages were ex- pressed by the following four indices: species diversity [H (S)], equitability (Eq.), the number of species, and number of individuals per 10 g sediment sample. These indices have been used extensively in paleoecology. Figure 9 shows vertical changes of these indices. Changes in faunal struc- tures may be related to environmental changes (e.g., Buzas and Hayek, 1998). Species diversity [H(S)] and equitability (Eq.) are expressed by the Shannon-Wiener formula and the equation of Buzas and Gibson (1969), respectively: H(S) = -% pinp; and Eg. = exp[H(S)]/S where p; means the proportion (relative abundance) of the i-th species in a sample and S the number of species. In the middle part of the Kubota Formation, the values of H(S) and Eq. range from 2.08 to 3.00 and from 0.44 to 0.64, respectively. The number of species in each sample varies from 20 to 40. Vertical changes of Eq. values are little. H(S) values and the number of species change synchro- nously. Through the upper horizon of the middle to upper part (samples NK41 and KM3) , H(S) values and the number = Figure 5. Scanning electron micrographs of selected ostracode species from the Kubota Formation. All specimens, expect for one juvenile one (7), represent adult valves. All scale bars indicate 100 um. RV = right valve; LV = left valve. 1: Aurila sp., RV, loc. NK27. 2: Callistocythere hatatatensis Ishizaki, RV, loc. NK34.5. 3: Callistocythere kotorai Ishizaki, RV, loc. NK35. 4: Callistocythere sp.2, LV, loc. NK36. 5: Coquimba cf. ishizakii Yajima, RV, loc. NK25. 6: Coquimba sp.1, RV, loc. NK10. 7: Coquimba sp.2, RV, loc. NK27. 8: Cornucoquimba saitoi (Ishizaki), LV, loc. NK35. omotenipponica Hanai, RV, loc. NK27. loc. NK10. 13: Cytheropteron subuchioi Zhao, LV, loc. NK27. 9: Cornucoquimba moniwensis (Ishizaki), LV, loc. NK21. 11: Cytheropteron miurense Hanai, LV, loc. KM3. 14: Eucytherura neoalae Ishizaki, RV, loc. NK21. 10: Cythere 12: Cytheropteron cf. sawanense Hanai, LV, 15: Finmarchinella japonica (Ishizaki), RV, loc. NK27. 16: Hanaiborchella triangularis (Hanai), RV, loc. NK27. 17: Yezocythere gorokuensis (Ishizaki), LV, loc. NK27. 18: Trachyleberis sp., RC, loc. NK35. Late Miocene ostracodes 1, 2, 3, 5, 6, 8, 10, 11,14, 15, 18 13, 16, 17— 15 um 13, 4, 7, 8, 3, 6, fe 7) & > lu <= x O = az TD Cc oO = iS) 3 D) is} = © > O = < 3 rm) 2 © Fr 11,14 == ‚12 == 10 2, 5,9, 249 Late Miocene ostracodes DRS IF DET IF I IA Acanthocythereis spp. Aurila cymba (Brady) Oo CS CS O0 cc C0 © —-[0 co © © n 00 © 000000celo-|[00 14 33 22 26 10 19 22 6 10 27 37) 42 27 12 45] 39 40 48 O0 32 34) 54 42 37 64 42) 38 78 48 Si 2 IE) 3a P_G M pP 46 G 10 3] 2 30 76 25 87 GEGEMZGEGTIMEMEGEM ER I MEGEMEGTIG = Le) o © = 9 105 127,229 163 164 234 176] 200 259 182 223 200] 209 203 195 22 816 181 101) 95 8 GM GG G|M M M M G Asterisk marks indicate samples and species used for with prin- List of ostracode species from the Kubota Formation. Figure 7. pal component analysis = poor. moderate and P M good, Abbreviation for preservation: G ci All are adult specimens. ecies from the Kubota Formation. Scanning electron micrographs of selected ostracode sp Figure 6. All scale bars indicate 100 pm. RC Lu Hermanites posterocostatus Ishizaki, RV, loc. NK27. 2 de micytherura cuneata Hanai i, RV, loc. NK36. 6 right lateral view of carapace. Loxoconcha nozokiensis Ishizaki Kotoracythere abnorma loc. NK27. 4: LV Loxocorniculum sp., LV, loc. NK27. 7 He NK34.5. 3 RV, loc. Hemicythere kitanipponica (Tabuki) Munseyella Paracytheridea neolongicaudata Ishizaki, RV, loc. NK27. Semicytherura henryhowei Hanai and Ikeya, RV, loc.NK35. 5 Ishizaki, LV, 9 RV Palmenella limicola (Norman), LV, loc. NK21. Ishizaki, LV, loc. NK40. 8 10 (Kajiyama), RV, loc. KM3. loc. NK21. hatatatensis loc. NK34. | Schizocythere kishinouyei 12 11: Rotundracythere ? sp. Schizocythere hatatatensis Ishizaki, LV, loc. KM3. loc. NK35. LV, Robertsonites sp. 14 . . 13 Spinileberis sp., LV, loc. NK3. 15 Tatsuhiko Yamaguchi and Hiroki Hayashi 250 Sample No. - KM14- : NK45 - KMI1- - KM10. ee) Se ----- NK32 - ----- NK29 - ----- NK28- No : NK26 - ---- NK23- Late Miocene ostracodes 251 of species decrease. The number of individuals in sample NK3 is 0.2 per 10 g sediment. Samples from the middle and upper parts con- tain about 40 to 400 and less than about 10 individuals per 10g, respectively. Principal component analysis In order to elucidate bottom environments of the Kubota Formation, 21 samples which contained more than 50 indi- viduals and 40 species represented by more than three indi- viduals at least in a sample were subjected to Q-mode principal component analysis. The analysis was carried out to obtain clues to the intersample relationship and to identify end members (samples having extreme properties). However, the correlation coefficient may be considered inap- propriate as a measure of similarity between samples because it requires calculation of variance across variables (Davis, 1986). Therefore, the analysis in this study was based on the covariance matrix. The computer program used in this study was a modified version written by Furuya and Obata (1996). The results of the analysis show that the first two components account for about 85 % of the total variation, which should be sufficient for discussion of general distribution patterns of the ostracode assemblages (Table 1). Figure 10 shows the stratigraphic distribution of eigenvectors in relation to the first two components. The first component This component explains more than 77% of the total variation. Schizocythere kishinouyei (score = +113.9), Kotoracythere abnorma (score = +35.9), Hanaiborchella triangularis (score = +34.5) and Cytheropteron miurense (score = +32.6) contribute greatly to this component. They are abundant in most of the samples examined. Recent representatives of these species are mostly known to occur predominantly in littoral to sublittoral habitats, which are in- fluenced by the Kuroshio Warm Current (e.g. Hanai, 1957, 1970; Ishizaki, 1966, 1981; Zhou, 1995; Tsukawaki et al. 1997, 1998). The first component is interpreted to repre- sent the abundance of ostracode species. The second component This component explains more than 7% of the total varia- tion. Kotoracythere abnorma (score = +32.0) and Cornu- coquimba saitoi s.|. (score = +8.8) have high positive scores of the second component. Hanaiborchella triangularis (score = -8.1), Rotundracythere? sp. (score = -7.9) and Schizocythere kishinouyei (score = -7.1) have high negative scores of the second component. K. abnorma and C. saitoi are extinct species. K. abnorma occurs in the middle Miocene Hatatate Formation, but does not occur in the Moniwa Formation, which is overlain conformably by the Hatatate Formation (Ishizaki, 1966). Kitamura et al. (1986) suggested that the Hatatate and Moniwa Formations were deposited in lower sublittoral to bathyal and upper sublittoral settings, respectively, based on sedimentary facies and benthic foraminifer assemblages. | Hence, K. abnorma is considered as having lived in the lower sublittoral zone under the influence of open sea water. Because C. saito/ also occurs in the Hatatate Formation, it is regarded as hav- ing lived under the influence of open sea water (Ishizaki, 1966). Thus, species having high positive scores are con- sidered as having lived in the open sea. On the other hand, species having high negative scores are reported from Recent seas, except for Rotundracythere? sp. H. triangularis is reported from the mouth of Ise and Mikawa Bays (Bodergat and Ikeya, 1988). Rotundracythere? sp. occurs in the Pleistocene Sasaoka Formation (Ishizaki and Matoba, 1985). Because Rotundracythere? sp. occurs with shallow marine molluscs, it is regarded as having like- wise lived in shallow marine waters. S. kishinouyei is re- ported from an upper sublittoral zone under the influence of coastal currents in the eastern China sea (Ishizaki, 1981). Therefore, species having high negative scores are consid- ered as having lived in shallow seas influenced by coastal currents. | Consequently, the second component is inter- preted as signalling changes of water mass: positive and negative eigenvectors represent the stronger and weaker in- fluence of open sea water, respectively. Discussion Water depths In the lower part of the Kubota Formation, Spinileberis sp. occurs dominantly. This fact suggests that the lower part was a deposit in an enclosed inner bay (e.g. Ikeya and Shiozaki, 1993). Most of the ostracode species from the middle part of the formation are reported in Recent shallow seas, as men- tioned above. Moreover, the faunal structures of the ostracode assemblages from the unit indicate high values of H(S), Eg. and the number of species. For example, the faunal structures of ostracode assemblages in the outer part of Uranouchi Bay show values of H(S), Eg. and the number of species that are 2.0 to 3.0, 0.4 to 0.6 and 20 to 40, re- spectively (Ishizaki, 1979). These values approximate those of the middle part. Thus, the ostracode assemblage from the middle part of the Kubota Formation represents a sublittoral setting. Vertical changes of the second compo- nent eigenvectors indicate that the influence of open sea water became stronger in the upward sequence. In the upper part, the low occurrence of ostracodes means that paleodepths cannot be assessed, except for the horizon of the sample KM3. The sample KM3 has a posi- tive second-component eigenvector and the horizon of the sample was deposited under the influence of open sea water. As already mentioned, Iwasaki (1970) molluscan fauna from the Kubota Formation. studied the He reported + Figure 8. Diagram showing the vertical changes for the relative abundance of major species. Broken lines show samples contain- ing more than 50 individuals of ostracodes. resent samples containing no ostracode. Dotted lines represent samples containing less than 50 individuals. For explanation of columnar sections see the legend of Figure 4. Loose dotted lines rep- 252 Tatsuhiko Yamaguchi and Hiroki Hayashi thickness (m) E 210 3 200 (individuals /10g sediment) The number of species 4 3 Ostracode number E: Ê H(S b 3 00 0 40 2.048) 3,0 0 ra 1.0 Sample No. 190 180 Kt-6 jee 170 160 150 140 130 Kt-5 120 110 100 70 60 50 40 30 Kt- 1 20 Lower 10 Late Miocene ostracodes 253 the Ostrea and Anadara-Dosinia assemblages from the lower part, the Lucinoma-Turritella assemblage from the middle part and the Mizuhopecten-Chlamys assemblage from the upper part. These molluscan assemblages repre- sent the following habitat conditions, referring to the paleobathymetric indices of molluscan fossils shown by Ogasawara and Masuda (1989): 1) the lower part represents an inner-bay environment with water depths shallower than 30 m; 2) the middle part represents depths between 100 and 200m; 3) the upper part represents depths of 30 m or less under the influence of the open sea. These estimates based on molluscan fossils from the Kubota Formation are generally consistent with the water depths suggested by ostracodes. Shimamoto et al. (1998) examined foraminifer, radiolar- ian and molluscan fossils and showed the successive changes of the planktonic/benthic foraminifer ratio (P/B ratio). They thought that the lower part was deposited in an inner bay because of the occurrence of Ostrea of in-situ origin, while the middle part was in an open sea shallower than about 100 m based on P/B ratios. Consequently, they concluded that the Kubota Formation represents a sequence of marine transgression and regression. Vertical changes of water depths suggested by ostracodes are largely consis- tent with their views. On the other hand, decreasing fre- quency of radiolarians in the upward sequence of the middle part suggests that influence of the open sea water became feeble. This representation contradicts one based on ver- tical changes of second-component eigenvectors. Some workers have pointed out that radiolarian assemblages from the Kubota Formation contain many reworked individuals (Taketani and Aita, 1991; Shimamoto et a/., 1998). There- fore, the reported frequency of radiolarians is regarded as not sufficiently representing paleoenvironmental settings during deposition of the middle part. Consequently, the middle part was subject to the strong influence of open sea water in its upward sequence. Marine climates In the lower part of the Kubota Formation, the only domi- nant species is Spinileberis sp. Recent species of this genus are widely distributed from southern China to northern Japan and occur abundantly in bays influenced by warm coastal waters (e.g. Hanai, 1961; Ishizaki, 1971; Ikeya and Shiozaki, 1993). Hence, the lower part is considered to have been deposited under the influence of warm coastal waters. In the middie part, Recent representatives of Schizocythere kishinouyei, Hanaiborchella triangularis and Cytheropteron miurense among the dominant species are reported from shallow seas under the influence of the Kuroshio Warm Current (e.g. Ishizaki, 1981; Zhou, 1995). However, such circumpolar and cryophilic species as Hemicytherura clathrata, Munseyella hatatatensis, Palmenella limicola, Finmarchinella japonica sil. and Hemicythere kitanipponica also occurred sparsely (Figure 10). Circumpolar and cryophilic species are members of high-latitude genera (Cronin and Ikeya, 1987). Irizuki and Matsubara (1995) and Irizuki et al. (1998) also reported that circumpolar and cryophilic species occurred with warm- water species in the Miocene deposits. They considered that the Miocene circumpolar and cryophilic species may not have experienced such subfrigid to frigid environments as their Recent counterparts and lived in slightly colder condi- tions than the other species because of the absence of fossil records for them from the mid-Neogene climatic optimum horizon of southwestern Japan (Ishizaki, 1963; Yajima, 1988, 1992). Hence, the middle part of the formation was deposited in a warm shallow sea under the feeble influence of cooler currents. Ostracodes are sparse in the upper part of the formation. However, species forming assemblages do not show any distinct change, comparing with the assemblages from the middle part. Hence, the upper part may also have been deposited in warm-water conditions. As mentioned above, Ogasawara (1994) studied the rela- tions between marine climates and Neogene molluscan fau- nas, considering their tolerance for marine climates. Moreover, he divided the Shiobara fauna into older and younger faunas based on characteristic species of each fauna. The molluscan fauna from the Kubota Formation belongs to the younger Shiobara fauna, because Mizuhopecten paraplebejus and Kaneharaia kaneharai, both of which characterize the younger fauna, were reported (Iwasaki, 1970). Ogasawara (1994) mentioned that the younger Shiobara fauna had lived in the warm- to mild- temperate realms of Nishimura’s (1981) zoogeographical classification of modern marine faunas around the Japanese Islands. Marine paleoclimates represented by ostracode fauna from the Kubota Formation strongly supported Ogasawara’s (1994) views. Conclusions 1) Sixty-seven ostracode species including those left in open nomenclature were reported for the first time from the upper Miocene Kubota Formation. The fauna is character- ized by the abundance of warm-water species. 2) The ostracode fauna from the Kubota Formation re- veals an enclosed inner bay paleoenvironment influenced by warm water for the lower part and a warm shallow sea under the feeble influence of cold water for the middle to upper part. Hence, the Shiobara fauna from the Kubota Formation flourished in a warm shallow sea. 3) Results of principal component analysis of succes- sively collected ostracode samples suggest that the middle part of the Kubota Formation was strongly influenced by + Figure 9. Diagram showing the vertical changes of the ostracode abundance of individuals per 10g sediment, number of species, species diversity (H(S)) and equitability (Eq.). Broken lines show samples containing more than 50 individuals of ostracodes. Dotted lines represent samples containing less than 50 individuals. Loose dotted lines represent samples containing no ostracode. For expla- nation of columnar sections see the legend of Figure 4. 254 Tatsuhiko Yamaguchi and Hiroki Hayashi eryophilic & thickness § circumpolar species (m) 5 0 20% 210 Sample No. 200 190 Upper 180 170 160 150 140 130 120 110 100 90 80 70 60 50 40 Late Miocene ostracodes 255 Table 1. Summary of principal component analysis. : Cumulative Eigenvalue Percentage Percentage PC 1 380.5 77.4 77.4 PC 2 37.8 CH 85.1 open sea water in its upward sequence. Acknowledgments We would like to express our deep appreciation to Kunihiro Ishizaki of .Ishinomaki Senshu University and Toshiaki Irizuki of Aichi University of Education for advice, continuous encouragement and reading the draft. Sincere thanks are also due to Masaki Takahashi and Yukio Yanagisawa of the Geological Survey of Japan for helpful advice on the fieldwork and geological ages and for provid- ing valuable figures. We are grateful to Kunio Kaiho of Tohoku University for helpful advice throughout the course of this study, Satoshi Ota of Miyagi Prefectural Office and Masanori Shimamoto of the Tohoku University Museum for their valuable suggestions concerning paleoenvironments during the Miocene and of the Kubota Formation, Takahiro Kamiya and Robin James Smith of Kanazawa University for helpful advice and correcting our English, and referees and editors for useful advice. Our special thanks go to Keio Otsuka of Tanagura, Fukushima Prefecture for kind help with the fieldwork. References Aita, Y., 1988: Neogene planktonic foraminifera from the Kubota Formation, Tanagura area, northeast Honshu, Japan. Bulletin of the Fukushima Museum, no. 2, p. 13-27. (in Japanese with English abstract) Blow, W. H., 1969: Late Middle Eocene to Recent planktonic foraminiferal biostratigraphy. In, Bronnimann, P. and Renz, H.H., eds., Proceedings of the First International Conference on Planktonic Microfossils (Geneva, 1969), Leiden, vol.1, p. 199-421. Bodergat, A. M. and Ikeya, N., 1988: Distribution of Recent Ostracoda in Ise and Mikawa Bays, Pacific coast of cen- tral Japan. In, Hanai, T, Ikeya, N. and Ishizaki, K., eds., Evolutionary Biology of Ostracoda - Its Fundamentals and Applications, p. 413-428., Kodansha, Tokyo and Elsevier, Amsterdam-Oxford-New York-Tokyo. Buzas, M. A. and Gibson, T. G., 1969: Species diversity: benthic foraminifera in western North Atlantic. Science, no. 163, p. 72-75. Buzas, M. A and Hayek, L.-A. C., 1998: SHE analysis for bio- facies identification. Journal of Foraminiferal Research, vol. 28, no. 3, p. 233-239. Chinzei, K., 1963: Notes on the historical changes of Neogene molluscan assemblages in Northeast Japan. Fossils (Palaeontological Society of Japan), no. 5, p. 21-26. 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C., 1995: Recent ostracode fauna in the Pacific off southwest Japan. Memoirs of the Faculty of Science, Kyoto University, Series Geology & Mineralolgy, vol. 57, no. 2, p. 21-98. Paleontological Research, vol. 5, no. 4, pp. 259-275, December 31, 2001 © by the Palaeontological Society of Japan The systematic status of the genus Miosesarma Karasawa, 1989 with a phylogenetic analysis within the family Grapsidae and a review of fossil records (Crustacea: Decapoda: Brachyura) HIROAKI KARASAWA' and HISAYOSHI KATO? "Mizunami Fossil Museum, Yamanouchi, Akeyo, Mizunami, Gifu 509-6132, Japan (e-mail: GHA06103 @nifty.ne.jp) “Natural History Museum and Institute, Chiba, Aoba-cho, Chiba 260-8682, Japan (e-mail: katoh@chiba-muse.or.jp) Received 23 May 2001; Revised manuscript accepted 16 August 2001 Abstract. Miocene of Japan is redefined. (length = 85, CI = 0.565, Ri = 0.807, RC = 0.456). The genus Miosesarma Karasawa (Decapoda: Brachyura: Grapsidae) known from the A phylogenetic analysis of 22 genera of the family Grapsidae MacLeay is provided based on 41 adult morphological characters. A single tree is produced The analysis supports the monophyly of the sub- families Plagusiinae Dana, Grapsinae MacLeay and Varuninae H. Milne Edwards. The analysis suggests that the Sesarminae Dana is polyphyletic and that Cyclograpsus H. Milne Edwards, Helice De Haan, Metaplax H. Milne Edwards and Miosesarma are derived as sister taxa to varunines. The tribe Cyclograpscaea H. Milne Edwards is treated as a subfamily Cyclograpsinae (nomen. transl.) consisting of Cyclograpsus (type genus), Helice, Heterograpsus Campbell and Griffin, Metaplax, Miosesarma and Paragrapsus H. Milne Edwards, which were previously placed within the Sesarminae. Within the Grapsidae, the Varuninae and Cyclograpsinae are sister groups nested as the most derived clade, followed by the Sesarminae, Grapsinae, and the most basal Plagusiinae. Five subfamilies within the Grapsidae are redefined based on the phylogenetic analysis. During a review of fossil records of the Grapsidae, 25 species, 17 genera and four subfamilies are recog- nized as fossils. Maingrapsus Tessier et al., Palaeograpsus Bittner, and Telphusograpsus Lörenthey, known from the European Eocene, are referred to the family Goneplacidae H. Milne Edwards and Sculptoplax Muller and Collins from the Eocene of Hungary is referred to the Xanthidae MacLeay. Fossil grapsids exhibiting the dorsal carapace only can not confidently be re- ferred to subfamilies. Key words: Brachyura, Crustacea, Decapoda, Grapsidae, Phylogeny Introduction The genus Miosesarma Karasawa, 1989 is an endemic genus known from the lower-middie Miocene of Japan (Karasawa, 1989, 1999; Kato, 1996). Karasawa (1989) originally placed the genus within the subfamily Sesarminae Dana, 1851 (Decapoda: Brachyura: Grapsidae) and demon- strated its close resemblance to extant sesarmines, Helice De Haan, 1835 and Metaplax H. Milne Edwards, 1852. Pereyra Lago (1993) and Schubart and Cuesta (1998) indi- cated that larval characters of Helice were similar to those of the grapsid subfamily Varuninae H. Milne Edwards, 1853. Schubart et al. (2000) suggested reclassification and phylogeny of the Grapsidae based upon molecular data, and that Helice and Metaplax should be classified within Varuninae. The purpose of the present paper is to redefine the genus Miosesarma based on newly obtained specimens and to provide an adult morphology-based phylogenetic analysis for 22 genera of the Grapsidae. A review of fossil records of the Grapsidae is included. Phylogenetic analysis of the family Grapsidae MacLeay, 1838 Materials and methods A total of 25 species were examined with representatives from 22 genera including one extinct genus, Miosesarma, within the Grapsidae. Among these, extant species were collected from Japan, Thailand and Malaysia. The analy- ses were based on the examination of material deposited in the Mizunami Fossil Museum, Mizunami, Japan and the 260 Hiroaki Karasawa and Hisayoshi Kato Table 1. Taxa included in the analysis. Family Grapsidae MacLeay, 1838 Subfamily Grapsinae MacLeay, 1838 Genus Geograpsus Stimpson, 1858 Geograpsus grayi (H. Milne Edwards, 1853) Genus Grapsus Lamarck, 1801 Grapsus albolineatus Lamarck, 1818 Grapsus tenuicrustatus (Herbst, 1783) Genus Metopograpsus H. Milne Edwards, 1853 Metopograpsus thukuhar (Owen, 1839) Genus Pachygrapsus Randall, 1840 Pachygrapsus minutus A. Milne Edwards, 1873 Genus Planes Bowdich, 1825 Planes cyaneus Dana, 1851 Subfamily Sesarminae Dana, 1851 Genus Chasmagnathus De Haan, 1833 Chasmagnathus convexus De Haan, 1833 Genus Cyclograpsus H. Milne Edwards, 1837 Cyclograpsus intermedius Ortmann, 1894 Genus Helice de Haan, 1835 Helice leachi Hess, 1865 Genus Metaplax H. Milne Edwards, 1852 Metaplax crenulata (Gerstecker, 1856) Genus Miosesarma Karasawa, 1989 Miosesarma japonicum Karasawa, 1989 Miosesarma naguraense Kato, 1996 Genus Nanosesarma Tweedie, 1950 Nanosesarma minutum (De Man, 1887) Genus Sesarma Say, 1817 Sesarma (Perisesarma) bidens (De Haan, 1835) Sesarma (Parasesarma) pictum (De Haan, 1835) Genus Sesarmops Serene and Soh, 1970 Sesarmops intermedium (De Haan, 1835) Subfamily Varuninae H. Milne Edwards, 1853 Genus Acmaeopleura Stimpson, 1858 Acmaeopleura parvula Stimpson, 1858 Genus Eriocheir De Haan, 1835 Eriocheir japonica (De Haan, 1835) Genus Gaetice Gistl, 1848 Gaetice depressus (De Haan, 1833) Genus Hemigrapsus Dana, 1851 Hemigrapsus sanguinensis (De Haan, 1835) Genus Pseudograpsus H. Milne Edwards, 1837 Pseudograpsus Sp. Genus Ptychognathus Stimpson, 1858 Ptychognathus sp. aff. P. ishii Sakai, 1939 Genus Varuna H. Milne Edwards, 1830 Varuna litterata (Fabricius, 1798) Subfamily Plagusiinae Dana, 1851 Genus Percnon Gistl, 1848 Percnon planissimum (Herbst, 1804) Genus Plagusia Latreille, 1804 Plagusia dentipes De Haan, 1833 Family Xanthidae MacLeay, 1838 Genus Leptodius A. Milne Edwards, 1873 Leptodius nudipes (Dana, 1852) Family Cancridae Latreille, 1803 Genus Cancer Linnaeus, 1758 Cancer amphioetus Rathbun, 1898 Natural History Museum and Institute, Chiba, Japan. The material examined is listed in Table 1. The subfamilial ar- rangement of the genera conforms to Sakai (1976), Manning and Holthuis (1981) and Karasawa (1989). Outgroups in- cluded two heterotrematous crabs, Cancer amphioetus Rathbun, 1898 (Cancridae) and Leptodius nudipes (Dana, 1852) (Xanthidae) outside of the Grapsidae (Table 1). Table 2 lists 41 adult morphological characters and charac- ter states used in the analysis. The missing data were scored unknown. The data matrix is provided in Table 3. The phylogenetic analysis used PAUP version 3.1.1 (Swofford, 1993), utilizing a data matrix originating in MacClade version 3 (Maddison and Maddison, 1992). Heuristic search analyses were performed with the following options in effect: addition sequence, simple; one tree held at each step during stepwise addition; tree-bisection- reconnection (TBR) branch stepping performed; MULPARS option activated; steepest descent option not in effect; branches having maximum length zero collapsed to yield polytomies; topological constraints not enforced; tree unrooted; multistate taxa interpreted as uncertain; character state optimization, accelerated transformation (ACCTRAN). All characters were unordered, unscaled and equally weighted. Characters Forty-one characters were included in the data matrix (Table 3). There are 34 binary characters and 7 multistate characters. In the text, characters and character states are indicated by numbers in parentheses (e.g. 1-0 = character 1+character state 0). Carapace.—In examined material the carapace is usually smooth (3-0; Figures 1.1, 1.2, 1.5-1.8, 4.11, 4.12, 4.15); however, all grapsine genera and a sesarmine Sesarma bear oblique ridges dorsally (3-1; Figure 1.3, 1.4). One outgroup taxon, Cancer, and two plagusiines, Plagusia and Percnon, possess frontal teeth (4-0; Figure 1.1, 1.2), while all other examined taxa have a straight frontal margin with- out teeth (4-1; Figure 1.3-1.8). Most taxa have a narrow orbital margin (5-0; Figure 1.1-1.4, 1.6), but a varunine Hemigrapsus and three sesarmines, Chasmagnathus, Metaplax and Miosesarma, possess wide orbital margins (5-1: Figures 1.5, 1.7, 1.8, 4.5, 4.11, 4.12, 4.15). Both outgroup taxa, all plagusiines and all grapsines lack infraorbital ridges (6-0; Figure 2.9-2.11); however, all sesarmines and all varunines bear infraorbital ridges (6-1; Systematic status of Miosesarma 261 Table 2. Characters and states used in the phylogenetic analysis. mb à ar fs) oo OO k WHY — ee ee ee ON On & WwW DY no — oO © ND D ND ND ND D ND ND ND © © —J DOA BR À ND = 30 Carapace Ratio of carapace length/width: wider than long (0); about equal (1); long (2) Maximum carapace width: midlength (0); anterior (1); posterior (2) Carapace with oblique ridges dorsally: absent (0); present (1) Frontal margin with frontal teeth: present (0); absent (1) Orbital width: narrow (0); wide (1) Infraorbital ridge: absent (0); present (1) Upper orbital margin with notch: present (0); absent (1) Lateral teeth: present (0); absent (1) Pterygostomian and ventrolateral surfaces with oblique striae: absent (0); present (1) Eye stalk and antennule Eye stalk: short (0); long (1) Antennule: not visible dorsally (0); visible dorsally (1) Maxilliped 3 Ratio of merus/ischium: short (0); subequal (1); very short (2) Anterolateral margin of merus: quadrate (0); expanded (1); convex (2) merus and ischium with oblique, hairy ridge: absent (0); present (1) Maxilliped 3 with wide rhomboidal gap: absent (0); present (1) Exopod: wide (0); narrow (1) Articulation of palp: anteromesial angle of merus (0); anterior margin of merus (1) Dactylus: long (0); short (1) Abdomen Male abdomen: fused somites (0); 7 somites (1) Male abdomen width; narrow (0); wide (1) Thoracic sternum Thoracic sternum width: narrow (0); wide (1) Sternites 1 and 2: distinct (0); indistinct (1) Suture between sternites 3 and 4: distinct (0); indistinct (1) Median groove on sternite 3: present (0); absent (1) Median groove on sternite 4: present (0); absent (1) Button: present (0); absent (1) Anterior end of sterno-abdominal cavity: shallow (0); sternite 4 (1); sternite 3 (2) Cristiform margin of anterior sterno-abdominal cavity: absent (0); present (1) Deeply concave lateral margin of sternites 3-4: absent (0); present (1) Transverse groove on sternite 8: absent (0); present (1) Sternite 8 visible in ventral view: indistinct (0); distinct (1) Sternite 8 visible in posterior view: indistinct (0); distinct (1) Location of male gonopore: coxae (0); sternite 8 (1) Location of male gonopore on sternite 8: excluded (0); lateral (1); inner (2) Gonopod Gonopods 1: sinuous (0); twist (1); linear (2) Pereiopods Cheliped with elongate, slender palm: absent (0): present (1) Chelipeds with pectinated crests on dorsal margin of propodus: absent (0); present (1) Chelipeds with hairs on lateral surfaces of propodus near base of fingers: absent (0); present (1) Chelipeds with tubercles on dorsal margin of dactylus: absent (0); present (1) Pereiopods 2-5 meri with longitudinal ridge on lateral surface: absent (0); present (1) Pereiopods 2-5 meri with oblique ridges on lateral surface: absent (0); present (1) 262 Table 3. oO Oo oO So oO [©] [®) oO Characters Taxa Hiroaki Karasawa and Hisayoshi Kato Input data matrix of 41 characters and 24 genera. The last two taxa are outgroups. Missing character states are shown by ?. 2 ND D D ine) D D ine) (ds) (ee) w wo (ds) & (9%) wo 3 > > Geograpsus Grapsus Metopograpsus Pachygrapsus Planes Chasmagnathus Cyclograpsus Helice Metaplax Miosesarma a a 2.10 — © © © © ON © © = © © © © © © © © = = ND CU + 1 1D © © © © © = = = = = |o 3 = = = = = = ge 1 nr x © x © © © © olu 1 x x x x © © © © 0]o = = = = = = || © © © © © © = mr © Ola © © © © © © © © © ©olwo ON OO SOS) CO => oo © © © © © © © © — = = = = CO © + = |N — D ND NN D ND = = FH — H/H0 — 4A = = = © © © © 0; — SN HN SA A Sle & oe Se Se eS Ns = N N En oO _ Nanosesarma Sesarma Sesarmops Acmaeopleura Eriocheir Gaetice Hemigrapsus Pseudograpsus Ptychognathus e Reo er _ — © = © © = © = 00 © = © © © ND © © — = © © © © © © © © = © SR DBD sts EN a S © © 6 © © © © © HS SN NS ann SS Rt Bsmt stn er Ss SCOO0OOOA 0 ooo-o000006o©0 © © © © © © © © © © oO = = = = O = = = = a 1 = = DD DD See Ce C' Ko SO © LS © © 35 = O©O © © rx © © © + aa SN SDS SO Varuna Percnon Plagusia Leptodius Cancer © ON N oO ON N © © © © oO = © © © © © © © © © © © © = = © © © © © © © © © © © © oo = = © © © N © © ND ND © © © © © © © 0 oo a © © © © OR er ONONONO) ICE ao 5 = = = = = = lo — oo © © © © © — + — © © © © S © © © ss à à = «|S US SN OS i i | SS 9 © © © © © © © © O|NM fw aa oo a a oa oa [lo De ee = = Te SS 1 = | OM EL MONO NO ON NONO)|IO D D NN ND D = = NY = | = = = = = © © = 9 © | D © © © © = © © © © 0/0 a = = = O OO OC OC OO I I MONO NON OO ©) MN RON ON oO ©) CO aa {a oa = = = = = a i gb) D ND ON ND = = = = = A/F D ND D ND ND = = = = | = =—- © co oo OO O0 0 1% © © © © © © © © © COIN W “yO © © © © © © © © © © © © © © © © © 0/0 © © © © © © © © © ©lo ooo oo = = = = —|— mi = a a = — — — — — 1 © © © © © + = a A A A à © © © © © © © © © © NN NN N en NN ER = = | OO = = = os et SR ur © 55 © À © 4552624 D D D D ND ND NN ND LD Schaan 4 © © © © © © © = = = DS © s À se À © © © 1 = = = = = nm © © © n À 1 + r r 4 © © © a À = = a a = 2 1 — D D D D D D ND = = = D D D D D ND D D ND ND © © © © © © © © © 0 © © © © © © © = + © OO eo SO) ZI CE) CE © © © © © © © © = + © © © © © © © © © © © oo © © 0000+ 0 © © © © oo = — oo = — © © © — © © = — oO = — — oo — © © © © oO —= — i © © © © © © © © © © © © © © = — © © © © © © = = © © + = © © = N © © © © © © © © © © © © © © © © o © = — © © © © Figures 2.12-2.16, 4.5, 4.8). Upper orbital fissures are pre- sent in both outgroup taxa (7-0), and absent in all taxa of the Grapsidae (7-1; Figures 1.1-1.8, 4.11, 4.12, 4.15). Two grapsines, Metopograpsus and Pachygrapsus, and a varunine Acmaeopleura possess the anterolateral margin without teeth (8-1), but all other taxa have anterolateral teeth (8-0; Figures 1.1-1.8, 4.11, 4.12, 4.15). The ptery- gostomian and ventrolateral surfaces in three sesarmines, Nanosesarma, Sesarma, and Sesarmops, are ornamented with oblique striae (9-1), while those in remaining taxa are without oblique striae (9-0). A ratio of the carapace width/ length [character 1; Figure 1.1-1.8] and a maximum cara- pace width [character 2, Figure 1.1-1.8] are variable in ex- amined taxa and both characters seem to be consistent at the generic level. Eye stalk and antennule.—In examined taxa a varunine Hemigrapsus and three sesarmines, Chasmagnathus, Metaplax and Miosesarma have slender, long eye stalks (10-1; Figures 1.5, 1.7, 1.8, 4.15), but others have stout, short ones (10-0; Figure 1.1-1.4, 1.6). The antennule in all plagusiines is visible dorsally in deep clefts of the front (11-1; Figure 1.1, 1.2), and this character defines the Plagusiinae (Alcock, 1900 and subsequent workers). In all other taxa antennules are not visible dorsally (11-0; Figures 1.3-1.8, 4.11, 4.12, 4.15). Maxilliped 3.—The merus is shorter than the ischium in both outgroup taxa, three grapsines, Metopograpsus, Pachygrapsus and Planes, a plagusiine Plagusia, and two varunines, Gaetice and Varuna (12-0; Figure 2.9); it is much shorter than the ischium in only plagusiine Percnon (12-2; Figure 2.10). In remaining taxa its length is about equal to the ischium length (12-1; Figures 2.11-2.16, 4.10). The anterolateral corner of the merus is quadrate in both outgroups (13-0), is more or less expanded and strongly convex anterolaterally in all grapsines and all varunines (13-1; Figure 2.11, 2.15, 2.16), and is not expanded but con- vex in all plagusiines and all sesarmines (13-2; Figures 2.9, 2.10, 2.12-2.14, 4.10). The possession of an oblique, hairy ridge on the merus and ischium is a definitive character of the Sesarminae (Alcock, 1900 and subsequent workers). In examined taxa, all extant sesarmines possess this oblique, hairy ridge (14-1; Figure 2.12-2.14), which all other taxa lack. In all grapsines, all sesarmines and a varunine Hemigrapsus, a wide rhomboidal gap separates maxillipeds 3 (15-1; Figure 2.11-2.15), while maxillipeds 3 are com- pletely closed together or leave a narrow gape in all other taxa (15-0; Figures 2.9, 2.10, 2.16, 4.10). The exopods are wide in two outgroup taxa and most varunines (16-0; Figure 2.16), but narrow in most grapsines, all plagusiines and all sesarmines (16-1; Figures 2.9-2.15, 4.10). In both Systematic status of Miosesarma ft A ft Figure 1. Diagrammatic representation of selected extant grapsid morphological characters. 1-8. Dorsal view of carapace. 9-14. Thoracic sternum and abdomen of male. 15, 16. Thoracic sternum of male. 1, 9: Plagusia dentipes De Haan, 1833 (CL = 43.5 mm). 2, 10, 15: Percnon planissimum (Herbst, 1804) (CL = 33.8 mm). 3: Grapsus albolineatus Lamarck, 1818 (CL = 57.6 mm). 4: Sesarma (Perisesarma) bidens (De Haan, 1835) (CL = 12.5 cm). 5, 13, 16: Hemigrapsus sanguinensis (De Haan, 1835) (CL = 18.9 mm). 6, 13: Cyclograpsus intermedius Ortmann, 1894 (CL = 18.3 mm). 7: Metaplax crenulata (Gerstecker, 1856) (CL = 29.4 mm). 8: Helice leachi Hess, 1865 (CL = 14.6 mm). 12: Sesarmops intermedium (De Haan, 1835) (CL = 24.1 cm). Abbreviations: A, antennule; a1, abdominal somite 1; a2, abdominal somite 2; a3, abdominal somite 3; a4, abdominal somite 4; a5, abdominal somite 5; a6, abdominal somite 6; aT, telson; at, anterolateral tooth; b, button; cm, cristiform margin of anterior sterno-abdominal cavity; cx5, coxa of pereiopod 5; eps4, episternite 4; eps5, episternite 5; eps6, episternite 6; eps7, episternite 7; es, eye stalk; ft, frontal tooth; or, oblique ridge; s1-2, thoracic sternites 1-2; s3, thoracic sternite 3; s4, thoracic sternite 4; s5, thoracic sternite 5; s6, thoracic sternite 6; s7, tho- racic sternite 7; s8, thoracic sternite 8; sac, sterno-abdominal cavity; tg, transverse groove on sternite 8. 263 264 Hiroaki Karasawa and Hisayoshi Kato eps6 eps6 eps6 eps/ 21 a tg 22 Figure 2. Diagrammatic representation of selected extant grapsid morphological characters. 1, 2. Gonopod 1. 3-5. Cheliped. 6-8. Merus of pereiopod 4. 9-16. Ventral view of carapace and maxilliped 3. 17-24. Thoracic sternites 7 and 8. 1, 11, 19: Grapsus tenuicrustatus (Herbst, 1783) (CL = 36.1 mm). 2, 13, 23: Cyclograpsus intermedius Ortmann, 1894 (CL = 18.3 mm). 4, 5: Sesarma (Parasesarma) pictum (De Haan, 1835) (CL = 17.4 mm). 6, 9, 17: Plagusia dentipes De Haan, 1833 (CL = 43.5 mm). 7: Grapsus albolineatus Lamarck, 1818 (CL=57.6 mm). 8: Helice leachi Hess, 1865 (CL = 14.6 mm). 10, 18: Percnon planissimum (Herbst, 1804) (CL = 33.8 mm). 12, 20: Sesarmops intermedium (De Haan, 1835) (CL = 24.1 mm). 14, 24: Metaplax crenulata (Gerstecker, 1856) (CL=29.4mm). 15, 22: Hemigrapsus sanguinensis (De Haan, 1835) (CL = 18.9 mm). 16: Ptychognathus sp. aff. P. ishii Sakai, 1939 (CL = 8.3 mm). 21: Chasmagnathus convexus De Haan, 1833 (CL = 40.1 mm). Abbreviations: cx5, coxa of pereiopod 5; eps6, episternite 6; eps7, episternite 7; eps8, episternite 8; G, gonopore; gr, tubercles on dorsal margin of dactylus; ir, infraorbital ridge; Irp, longitudinal ridge on lateral surface of pereiopod 4; orm, oblique, hairy ridge on merus and ischium of maxilliped 3; orp, oblique ridge on lateral surface of pereiopod 4; pc, pectinated crests on dorsal margin of propodus; s7, thoracic sternite 7; s8, thoracic sternite 8; tg, transverse groove on sternite 8; wg, wide rhomboidal gap between maxillipeds 3. Systematic status of Miosesarma 265 outgroup taxa and all plagusiines the palp articulates at an anteromesial angle of the merus (17-0; Figure 2.9, 2.10); however, in all other taxa it articulates at an anterior margin (17-1; Figures 2.11-2.16, 4.10). The dactyli are long in both outgroup taxa, all plagusiines, all grapsines and all varunines (18-0; ; Figure 2.9-2.11, 2.15, 2.16), but is re- duced and short in all extant sesarmines (18-1; Figure 2.12-2.14). Abdomen.—In all grapsines, all sesarmines and all varu- nines, the male abdomen consists of seven unfused ab- dominal somites (19-1; Figures 1.11-1.14, 4.9, 4.14), while the outgroup taxa and all plagusiines possess fused somites (19-0; Figure 1.9, 1.10). The outgroup taxa, most varu- nines and four sesarmines, Cyclograpsus, Helice, Metaplax and Miosesarma, have a narrow male abdomen (20-0; Figures 1.13, 1.14, 4.3, 4.9, 4.14), while the male abdomen is wide and fills the entire space between pereiopods 5 in all grapsines, all plagusiines, two varunines, Varuna and Eriocheir, and three sesarmines, Nanosesarma, Sesarma and Sesarmops (20-1; Figure 1.9-1.12). Thoracic sternum.—All grapsids possess a wide thoracic sternum (21-1; Figures 1.9-1.14, 4.2, 4.3, 4.6, 4.7, 4.9, 4.10, 4.13, 4.14, 4.16), but the two outgroup taxa have a narrow sternum (21-0). In the outgroup taxa and most extant grapsids, thoracic sternites 1-2 are distinct (22-0; Figure 1.9, 1.11-1.14), while in only plagusiine Percnon they are re- duced and indistinct (22-1; Figure 1.10). In both outgroup taxa, a suture between sternites 2 and 3 is distinct and well defined as a deep groove (23-0); however, the suture in all grapsids is indistinct and poorly defined (23-1; Figures 1.9-1.14, 4.13, 4.14). A median groove on sternite 3 is pre- sent in one outgroup taxon, Cancer, and a varunine Gaetice (24-0) , but it is absent in all other examined taxa (24-1; Figures 1.9-1.14, 4.6, 4.13). A median groove on sternite 4 is present in both outgroup taxa (25-0), but is absent in all grapsid taxa (25-1; Figures 1.9-1.14, 4.6). Guinot and Bouchard (1998) described the button on the male thoracic sternum within the Brachyura and indicated that in their ex- amined material plagusiines and grapsines possessed the button on the sternum (Figure 1.15), but that the button was either present or absent within the Varuninae and Sesarminae (Figures 1.16, 4.6). In our examined material the button [character 26] is present in both outgroup taxa, all grapsines and all plagusiines, and present or absent in sesarmines and varunines. The outgroup taxon, Cancer, possesses a shallow sterno-abdominal cavity (27-0), while all other examined taxa have a deep sterno-abdominal cav- ity (Figures 1.9-1.16, 4.6). The anterior end of the sterno- abdominal cavity reaches the anterior sternite 4 in one outgroup, Leptodius, most grapsines and all plagusiines (27-1; Figure 1.9-1.11, 1.15), and reaches sternite 3 in all sesarmines, all varunines and a grapsine Metopograpsus (27-2; Figures 1.12-1.14, 1.16, 4.6, 4.13, 4.14). Guinot and Bouchard (1998) mentioned that in the Thoracotremata a deep sterno-abdominal cavity was often anteriorly delimited by a cristiform margin. In our examined material, the cristiform margin is well defined in all sesarmines, all varunines and a grapsine Metopograpsus (28-1; Figures 1.12-1.14, 1.16, 4.6, 4.13), but absent in both outgroup taxa, all plagusiines and most grapsines (28-0; Figure 1.9-1.11, 1.15). Nanosesarma, Sesarma and Sesarmops, members of the Sesarminae, possess deeply concave lateral margins of sternites 3-4 (29-1; Figure 1.12). In both outgroup taxa and the sesarmine genera, Chasmagnathus, Nanosesarma, Sesarma and Sesarmops, the male abdomen covers entirely the sternite 8 (31-0, 32-0; Figure 1.9-1.12). The sternite 8 is not covered entirely by the abdomen and is visible in ven- tral and posterior view in all varunines and four sesarmines, Cyclograpsus, Helice, Metaplax and Miosesarma (31-1, 32-1; Figures 1.13, 1.14, 4.14), but in both plagusiine taxa the male abdomen fills the entire space between pereiopods 5 (31-0; Figure 1.9, 1.10) and is visible in ventral view (32-1; Figure 1.9, 1.10). In members of the section Heterotremata Guinot, 1977, male gonopores are located on coxae and/or the thoracic sternite 8, and the gonopores in all representatives within the Thoracotremata Guinot, 1977 are on sternite 8 (Guinot, 1977; Guinot and Richer de Forges, 1997). If male gonopores are situated on the inner part of sternite 8, the sternite is traversed by a groove which arises from the coxa and joins the gonopore or is interrupted (Figure 2.22-2.24) (Guinot, 1979; Tavares, 1992; Jamieson, Guinot and Richer de Forges, 1996). Both outgroups, all grapsines, all plagusiines, and the sesarmine genera, Chasmagnathus, Nanosesarma, Sesarma and Sesarmops, lack a transverse groove on the sternite 8 (30-0; Figure 2.17-2.20); however, most varunines and four sesarmines, Cyclograpsus, Helice, Metaplax and Miosesarma, have a groove on sternite 8 (30-1; Figures 2.22-2.24, 4.13, 4.14). In all grapsids of the Thoracotremata male gonopores are opened on thoracic sternite 8 (34-1; Figures 2.17-2.24, 4.13, 4.14), but in both outgroup taxa belonging to the Heterotremata they are lo- cated on the coxae (34-0). When male gonopores are situ- ated on sternite 8, they are opened on lateral parts of sternite 8 in all plagusiines, all grapsines and the sesarmines, Chasmagnathus, Nanosesarma, Sesarma and Sesarmops (34-1; Figure 2.17-2.21). The male gonopores are located on the inner part of sternite 8 (34-2; Figures 2.22-2.24, 4-13, 4.14) in all varunines and the sesarmines, Cyclograpsus, Helice, Metaplax and Miosesarma. Gonopod.—Only one character is found to be informative. Male gonopods 1 are sinuous (35-0) in both outgroup taxa, twisted (35-1; Figure 2.1) in a plagusiine Plagusia and all grapsines, and linear (35-2; Figures 2.2, 4.7, 4.13, 4.14, 4.16) in a plagusiine Percnon, all sesarmines and all varunines. Pereiopods. — Two sesarmine genera, Metaplax and Miosesarma, possess a slender, elongate palm of the male chelipeds (36-1; Figures 2.3, 4.4), while all other taxa pos- sess a short, massive palm (36-0; Figure 2.4). In examined material two sesarmines, Sesarma and Sesarmops, have chelipeds with pectinated crests on the dorsal margin of the propodus (37-1; Figure 2.5) and with tubercles on the dorsal margin of the dactylus (39-1; Figure 2.5). Four varunines, Acmaeopleura, Hemigrapsus, Pseudograpsus and Ptychog- nathus, bear hairs on the lateral surface of the propodus of the cheliped near the base of fingers (38-1), which all other extant taxa lack. Longitudinal ridges on the lateral surface of meri of pereiopods 2-5 are present in the Plagusiinae (40-1; Figure 2.6), but absent in all other taxa (40-0; Figures 266 Hiroaki Karasawa and Hisayoshi Kato Previous Present stud stud (1) y y Acmaeopleura 2(1), 30 (0) Ptychognathus 15(0) Pseudograpsus o é oe Gaetice = E iy = Is 18(0) 1(1), 1210), 2001) Varuna S & 20(0) se) 3 30(1) Eriocheir 31(1) 5(1), 10(1), 38(1) 32(1) Hemi eit) M0) igrapsus A ary EM Metaplax ® 18(1) 10(1) FOR = 27(2) Miosesarma D à. al 5 (2) Helice > {eb} = se) © clograpsus £ > 2 too oo = CIE oO (72) 29(1) aa Chasmagnathus 2 0 = ‘cel san Nanosesarma a £ So a, ee 3(1), 26(0), 41(1) E 13(2) 191) Sesarma 2 16(1) 20(1) 37(1), 39(1) Sesarmops ee a) rq 0.20 2541) (1) Geograpsus 34(1) 2(1) Grapsus 2 2 35(1) 1(1), 2(2) & £ 3(1), 13(1), 41(1) 8(1) 4 Pachygrapsus a a Metopograpsus (©) 5 27(2), 28(1) Planes 1(2), 16(0) ‘ ı a 1(2), 2(2),11(1), 31(1), 40(1) Plagusia G & D © D © Percnon ı So Hg © 4(1) 12(2), 22(1), 35(2) ac @ = Leptodius Xanthidae Outgroups : Cancer Cancridae Sa 24(0), 27(0) Figure 3. Single parsimonious tree of 22 genera within the Grapsidae. Length = 85, Consistency index = 0.565, Retention index = 0.807, Rescaled consistency index = 0.456. Character changes are indicated. 2.8, 4.15). All taxa within the Grapsinae and a sesarmine Sesarma possess oblique ridges on the lateral surface of meri of pereiopods 2-5 (41-1; Figure 2.7), which all other taxa lack. Results The present analysis yielded a single parsimonious tree, 85 steps long with a consistency index (Cl) of 0.565, a reten- tion index (RI) of 0.807 and a rescaled consistency index (RC) of 0.456 (Figure 3). The monophyly of the Grapsidae is well supported by ten characters, five of which are unique and unreversed: the upper orbital margin without distinct notches (7-1), a wide thoracic sternum (21-1), the absence of a suture between thoracic sternites 3 and 4 (23-1), the absence of a median groove on the thoracic sternite 4 (25- 1), and male gonopores opened on thoracic sternites 8 (33-1). Our analysis suggests that within the Grapsidae the Plagusiinae is the most basal clade, followed by the Grapsinae, Sesarminae and the most derived Varuninae. The Plagusiinae is united by five characters, three of which are unique: antennules which are visible dorsally (11-1), sternite 8 which is visible ventrally (31-1), and the posses- Systematic status of Miosesarma 267 sion of longitudinal ridges on meri of pereiopods 2-5 (40-1). The Grapsinae+Sesarminae+Varuninae clade is unambi- guously united by four synapomorphies, three of which are never reversed: the absence of frontal teeth (4-1), the palp of the maxilliped 3 which articulates at an anterior margin of the merus (17-1), and the male abdomen with seven free somites (19-1). Three synapomorphies, the carapace with oblique ridges dorsally (3-1), an expanded anterolateral cor- ner of the merus of the maxilliped 3 (13-1), and the pres- ence of meri of pereiopods with oblique ridges on the lateral surface (41-1), well support the monophyly of the Grap- sinae. The analysis shows the sister-group relationship of the Grapsinae and Sesarminae+Varuninae clades. The Sesarminae+Varuninae clade is unambiguously united by seven characters of which four are never reversed: the pos- session of the infraorbital ridge (6-1), an anterior margin of the sterno-abdominal cavity reaching the thoracic sternite 3 (27-2), the presence of the cristiform margin of an anterior sterno-abdominal cavity (28-1), and linear gonopods 1 (35-2). Our analysis suggests that the Sesarminae as customarily defined is a polyphyletic group. The monophyly of the Chasmagnathus+Nanosesarma+Sesarma+Sesarmops cla- de is united by only one character, deeply concave lateral margins of thoracic somites 3 and 4 (29-1), and is derived as the sister to the Varuninae+four remaining sesarmines (Cyclograpsus, Metaplax, Helice, Miosesarma) clade. The Varuninae and Metaplax+Miosesarma+Helice+Cyclograp- sus clades are unambiguously united by four unique synapomorphies: the presence of a transverse groove on the thoracic sternite 8 (30-1), the thoracic sternite 8 which is visible in ventral and posterior view (31-1, 32-1), and male gonopores located on the inner part of the thoracic sternite 8 (34-2). The Varuninae clade is the sister to the Metaplax +Miosesarma+Helice+Cyclograpsus clade and is united by three characters, an expanded anterolateral corner of the merus of maxilliped 3 (13-1), the absence of oblique, hairy ridges on the merus and ischium of maxilliped 3 (14-0) and a long dactylus of maxilliped 3 (18-0). Discussion The family Grapsidae is presently divided into four sub- families, Grapsinae, Plagusiinae, Sesarminae and Varuninae, based on the adult morphology (i.e., Alcock, 1900, Rathbun, 1918, Sakai, 1976, Guinot, 1979, Manning and Holthuis, 1981). However, the subfamilial arrangement of some genera within the Grapsidae has been questioned by recent contributions based on larval morphology (Pereyra Lago, 1993, Schubart and Cuesta, 1998 and many more) and molecular data using the 16S rRNA (Schubart et al, 2000). Guinot and Bouchard (1998) mentioned that both Sesarminae and Varuninae were artificial groups. Rice (1980) noted that the Grapsinae seemed to have the most advanced zoeae within the Grapsidae and thought that the four subfamilies within the Grapsidae evolved independently from a more primitive stock of which there is no larval evi- dence. Schubart, Neigel and Felder (2000) and Schubart et al. (2000) provided molecular phylogenies of the Grapsidae. Although Schubart et al. (2000) treated four subfamilies within the Grapsidae as families, we place four subfamilies within the Grapsidae according to previous stud- ies of Alcock (1900), Sakai (1976), Manning and Holthuis (1981) and others. The adult morphology-based phylogeny presented herein and the molecular phylogeny of Schubart et al. (2000) each of which supports monophyly of the Grapsidae, are each largely supported, but they differ somewhat in topology. Ten characters, five of which are unique and unreversed, well support the monophyly of the family Grapsidae in this study. Schubart, Neigel and Felder (2000) showed the paraphyly of the family based on molecular data using 16S rRNA but the subsequent study of Schubart et al. (2000) suggested the monophyly of the family; we concur that the Grapsidae is monophyletic. Our morphology-based phylogenetic analysis suggests the Plagusiinae is the earliest derived crown-group subfam- ily, followed by the Grapsinae. These results support the molecular phylogeny of the family by Schubart et al. (2000). The Plagusiinae and Grapsinae are monophyletic by our analysis. The monophyly of the Grapsinae is well sup- ported by molecular data (Schubart et a/., 2000) and larval morphology (Rice, 1980, Cuesta and Schubart, 1999). Schubart et al. (2000) showed that the Plagusiinae was polyphyletic and that only Percnon was the most basal clade. However, the larval morphology of Percnon is most similar to that of Plagusia within the Grapsidae (Rice, 1980) which supports our tree in which Percnon and Plagusia occur together on one clade. The subfamily Sesarminae is polyphyletic. The Metaplax +Miosesarma+Helice+Cyclograpsus clade is readily distin- guished from the Chasmagnathus+Nanosesarma+Sesarma +Sesarmops clade by having four unique synapomorphies and the former is derived as the sister to the Varuninae clade. One unique synapomorphy supports the monophyly of the latter sesarmine clade. The Sesarminae was previ- ously discriminated from the other three subfamilies by the possession of an oblique, hairy ridge on the merus and ischium of the maxilliped 3 (Alcock, 1900 and subsequent workers). In our analysis the presence of this ridge [charac- ter 14] is not a unique character and the character state in the Varuninae clade is the absence of the ridge, a reversal of the state identified as a synapomorphy of the Sesarminae+Varuninae clade. Guinot (1979) indicated that male gonopores of Cyclograpsus, Helice and Metaplax together with those of varunine genera were located on the inner part of thoracic sternite 8. Examination of American sesarmine genera based on molecular data (Schubart et al. 2000) suggested that Chasmagnathus and Cyclograpsus should be classified within the Varuninae and that the re- maining Sesarminae group was monophyletic. Pereyra Lago (1993) and Schubart and Cuesta (1998) also showed that larval characters of three genera, Chasmagnathus, Cyclograpsus and Helice, were similar to those of members within the Varuninae rather than Sesarma sensu lato. However, our adult-morphology based analysis indicates that Chasmagnathus remains within the “Sesarminae” clade and that Cyclograpsus and Helice belong to another clade which is derived as the sister to the Varuninae clade and are more derived than the “Sesarminae” clade. The present analysis separates the Metaplax+Miose- 268 Hiroaki Karasawa and Hisayoshi Kato sarma+Helice+Cyclograpsus clade from the “Sesarminae” clade and strongly suggests that genera piaced within the clade should be classified in another subfamily. H. Milne Edwards (1853) erected a new tribe Cyclograpscaea within his subfamily Grapsinae (= Grapsidae see Alcock, 1900). Six genera, Pseudograpsus, Heterograpsus Lucas, 1849 (= Brachynotus de Haan, 1833), Cyclograpsus, Paragrapsus H. Milne Edwards, 1853, Pralynotus de Haan, 1835 (= Gaetice), and Chasmagnathus were originally included in the Cyclograpscaea. Subsequently, Alcock (1900) rede- fined four subfamilies within the Grapsidae, and synonymized the Cyclograpscaea with the Sesarminae and Varuninae. He moved Pseudograpsus, Brachynotus and Gaetice to the Varuninae and Cyclograpsus and Chasmagnathus to the Sesarminae. Tesch (1918) referred Paragrapsus to the Sesarminae. In our phylogenetic analy- sis, Pseudograpsus and Gaetice are classified within the Varuninae, and Chasmagnathus is placed within the Sesarminae. Two genera, Brachynotus and Paragrapsus, were not examined in our analysis. We treat the tribe Cyclograpscaea which contains a remaining genus Cyclograpsus as a subfamily Cyclograpsinae H. Milne Edwards, 1853 nomen. transi. herein (type genus: Cyclograpsus by present designation). Three additional genera, Helice, Miosesarma and Metaplax are included in the Cyclograpsinae based on the present analysis. The Cyclograpsinae is distinguished from the Sesarminae in that male gonopores are located on the inner part of thoracic sternite 8, sternite 8 is visible in ventral and poserior view, and bears a distinct transverse groove that extends from the articulation of the coxa-sternal junction to the gonopore. The present subfamily differs from the Varuninae derived as its sister group by the presence of an oblique, hairy ridge on the merus and ischium and a short, reduced dactylus of maxilliped 3, and the absence of an anterolateral expansion of the merus of maxilliped 3. Paragrapsus and Hetero- grapsus Campbell and Griffin, 1966 have an oblique, hairy ridge on the merus and ischium of maxilliped 3, male gonopores located on the inner part of the thoracic sternite 8, and a transverse groove on sternite 8; therefore, it is sug- gested that both genera should be referred to the Cyclograpsinae. Within examined material the Varuninae is at least monophyletic. However, Schubart et al. (2000) showed using molecular data that the subfamily was polyphyletic, Euchirograpsus H. Milne Edwards, 1853, a non North- western Pacific genus, was the sister taxon of Plagusia, and Platychirograpsus de Man, 1896 and Glyptograpsus Smith, 1870, which both are American endemic genera, were de- rived as the sister to the Sesarminae. The reexamination of the systematic position of these three genera is beyond the scope of our study, whilst examination of the detail adult morphology would be necessary to confirm the reassign- ment of these genera. The location of gonopores on thoracic sternite 8 [character 34] and the possession of the infraorbital ridge [character 6] are supported as useful phylogenetic characters. The gonopores are located on the lateral margin of sternite 8 in the Plagusiinae, Grapsinae and Sesarminae, and on the inner part of sternite 8 in the Cyclograpsinae and Varuninae. The Plagusiinae and Grapsinae lack the infraorbital ridge, while the Sesarminae, Cyclograpsinae and Varuninae pos- sess the infraorbital ridge. The following diagnosis is given for five subfamilies based on our phylogenetic analysis: Subfamily Plagusiinae Dana, 1851.—Front with teeth. Antennule visible dorsally. Infraorbital ridge absent. Maxillipeds 3 without wide rhomboidal gap and oblique, hairy ridge on merus and ischium; anterolateral corner not expanded, convex; palp articulating at anteromesial corner of merus; exopod narrow. Male abdomen wide, filling entire space between pereiopods 5. Anterior margin of sterno- abdominal cavity reaching thoracic sternite 4. Sternal button present in male. Male gonopore located on lateral margin of thoracic sternite 8. Meri of pereiopods usually bearing lon- gitudinal ridges laterally and spines dorsally (modified from Rathbun, 1918). Subfamily Grapsinae MacLeay, 1838.— Front usually strongly deflexed. Carapace usually with oblique ridges dorsally. Infraorbital ridge absent. Maxillipeds 3 usually separated by wide rhomboidal gap, without oblique, hairy ridge on merus and ischium; anterolateral corner of merus usually expanded; palp articulating at anterior margin of merus; exopod narrow. Male abdomen wide, filling entire space between pereiopods 5. Anterior margin of sterno- abdominal cavity usually reaching thoracic sternite 4. Strernal button present in male. Male gonopore located on lateral margin of thoracic sternite 8 (modified from Rathbun, 1918). Subfamily Sesarminae Dana, 1851.— Front strongly deflexed. Infraorbital ridge present. Maxillipeds 3 sepa- rated by wide rhomboidal gap, and with oblique, hairy ridge on merus and ischium; anterolateral corner of merus not ex- panded, convex; palp articulating at anterior margin of merus; exopod narrow. Male abdomen wide, filling entire space between pereiopods 5. Anterior margin of sterno- abdominal cavity reaching thoracic sternite 3. Sternal button present or absent in male. Male gonopore located on lateral margin of thoracic sternite 8 (modified from Rathbun, . 1918). Subfamily Varuninae H. Milne Edwards, 1853.—Front moderately or little deflexed. Infraorbital ridge present. Maxillipeds 3 moderately or slightly gaping, without oblique, hairy ridge on merus and ischium; anterolateral corner of merus expanded; palp articulating at anterior margin of merus; exopod usually wide. Male abdomen rarely filling entire space between pereiopods 5. Anterior margin of sterno-abdominal cavity reaching thoracic sternite 3. Transverse groove usually present on sternite 8. Sternal but- ton usually present in male. Male gonopore located on inner part of thoracic sternite 8 (modified from Rathbun, 1918). Subfamily Cyclograpsinae H. Milne Edwards, 1853 [nom. transl. of Tribe Cyclograpscaea].—Front strongly deflexed. Infraorbital ridge present. Maxillipeds 3 separated by wide rhomboidal gap, with oblique, hairy ridge on merus and ischium; anterolateral corner of merus not expanded, con- vex; palp articulating at anterior margin of merus; exopod narrow. Male abdomen not filling entire space between pereiopods 5. Anterior margin of sterno-abdominal cavity Systematic status of Miosesarma 269 Figure 4. 1-13, 15, 16. Miosesarma japonicum Karasawa, 1989. 1: MFM83343, middle Miocene Masuda Group, frontal view of carapace and lateral view of cheliped, female, x2.5. 2: MFM39154, middle Miocene Bihoku Group, ventral view of thoracic sternum, fe- male, x2.5. 3: MFM39155, middle Miocene Bihoku Group, ventral view of thoracic sternum and abdomen, male, x2.5. 4: MFM9146, lower Miocene Mizunami Group, lateral view of chelipeds, male, x1.5. 5: MFM83344, middle Miocene Masuda Group, frontal view of carapace, male, x2.5. 6: MFM39156, middle Miocene Bihoku Group, ventral view of carapace, thoracic sternum and maxillipeds 3, male, x2.5. 7: MFM83345, middle Miocene Masuda Group, ventral view of carapace, thoracic sternum and gonopods 1, male, x2.5. 8: MFM83344, middle Miocene Masuda Group, ventral view of carapace and abdomen, male, x2.5. 9: MFM9017 (paratype), lower Miocene Mizunami Group, ventral view of thoracic sternum and abdomen, male, x2.5. 10: MFM39157, middle Miocene Bihoku Group, ventral view of carapace, thoracic sternum, abdomen and maxillipeds 3, female, x2.5. 11: MFM9016 (paratype), lower Miocene Mizunami Group, dorsal view of carapace, male, x2.5. 12: MFM9015 (holotype), lower Miocene Mizunami Group, dorsal view of cara- pace, male, x2.5. 13: MFM9147, lower Miocene Mizunami Group, ventral view of thoracic sternum, abdomen and gonopods 1, male, x2.5. 15: MFM39158, middle Miocene Bihoku Group, dorsal view of carapace and eye stalk, and lateral view of pereiopods, male, x2.5. 16: MFM83346, middle Miocene Masuda Group, ventral view of carapace, thoracic sternum, abdomen and gonopods 1, male, x2.5. 14. Miosesarma naguraense Kato, 1996, MFM83347, middle Miocene Nagura Formation, ventral view of thoracic sternum, abdomen and gonopods 1, male, x1.5. 270 Hiroaki Karasawa and Hisayoshi Kato reaching thoracic sternite 3. Transverse groove present on sternite 8. Sternal button usually absent in male. Male gonopore located on inner part of thoracic sternite 8 (rede- fined here). Redefinition of the genus Miosesarma Karasawa, 1989 Subfamily Cyclograpsinae H. Milne Edwards, 1853 Genus Miosesarma Karasawa, 1989 Type species. —Miosesarma japonica Karasawa, 1989 by monotypy. Species included. — Miosesarma japonicum Karasawa, 1989 (Figure 4.1-4.13, 4.15, 4.16) and Miosesarma naguraense Kato, 1996 (Figure 4.14). Revised diagnosis. — Carapace rectangular in outline, length about 3/4 width, widest at midlength. Front deflexed, about 1/4 carapace width. Frontal margin bilobed. Upper orbital margin sinuous, occupying about 3/4 carapace width. Anterolateral margins nearly straight, almost parallel, with 4 forwardly directed teeth. Posterolateral margin sinuous. Dorsal surface smooth, moderately vaulted transversely and weakly vaulted longitudinally. Regions well defined; epibranchial lobe more inflated; mesobranchial lobe with ridge extending from 4th anterolateral tooth; metabranchial lobe with weak ridge parallel to posterolateral margin. Infraorbital ridge present with prominence laterally. Thoracic sternum wide; sterno-abdominal cavity of male deep, reaching sternite 3; sternite 8 of male with transverse groove. Male abdomen narrow, not filling entire space be- tween pereiopods 5. Merus of maxilliped 3 subequal to ischium with convex anterolateral margin; exopod narrow. Male gonopod linear; gonopore opened on inner part of tho- racic sternite 8. Chelipeds dissimilar in both sexes; female chelae much smaller than male; propodus slender, elongate. Pereiopods flattened. Remarks. — Karasawa (1989) originally placed Miosesarma in the subfamily Sesarminae. Examination of new specimens shows that the genus is referred to the sub- family Cyclograpsinae because the infraorbital ridge is pre- sent, the gonopore is located on the inner part of the thoracic sternite 8, a narrow male abdomen does not fill all of the space between pereiopods 5, and the merus of maxilliped 3 has a convex anterolateral margin. Karasawa (1989) showed that the genus had close affinities with Recent cyclograpsines, Helice and Metaplax. Our phylogenetic analysis also suggests that Miosesarma and Metaplax are sister taxa nested as the most derived clade, followed by Helice and the most basal Cyclograpsus within the Cyclograpsinae. Most extant members of the Grapsidae live in intertidal waters and adapt to freshwater or terrestrial habitats (Guinot and Bouchard, 1998); however, Planes is known from pe- lagic waters (Manning and Holthuis, 1981) and Euchirograpsus from depths between 10 and 359 m (Manning and Holthuis, 1981). Miosesarma appears to have inhabited sublittoral and upper bathyal waters based on associated decapods and molluscs (Karasawa, 1993; Kato, 1996). Distribution. — Early-early Middle Miocene of Honshu, Japan; Ayugawa Group (Karasawa, 1997), Bihoku Group (Karasawa, 1993), Hokutan Group (Karasawa, 1997), Katsuta Group (Karasawa, 1993), Masuda Group (Karasawa, 1993), Mizunami Group (Karasawa, 1989), Chichibumachi Group (Kato, 1996), Nenokami Sandstone Member (Kato, 1996), Numanouchi Formation (Kato in prep.), Yatsuo Group (Karasawa, 1993). A review of fossil records of the family Grapsidae Previously known fossil records within the family Grapsidae have included 34 species and 21 genera. Fossil records of the Grapsinae comprise three genera: Metopograpsus from the lower Miocene of Hungary (Muller, 1998); Pachygrapsus from the middle Miocene of Hungary and Poland (Muller, 1974, 1996) and from the Pleistocene of Jamaica (Morris, 1993); and Planes from the lower Miocene of the Caucasus (Smirnov, 1929; Glaessner, 1969). The genus Sesarma (s.l.) of the Sesarminae is repre- sented by three fossil species, Sesarma paraensis Beurlen, 1958, from the upper Oligocene-lower Miocene of Brazil, Sesarma smithi H. Milne Edwards, 1853, from the Pleistocene of Australia (Etheridge and McCulloch, 1916) and Sesarma sp. from the middle Miocene of Japan (Karasawa, 1993). According to Seréne and Soh’s 1970 re- classification of the genus Sesarma (s.l.), S. smithi now be- longs to Neosarmatium Serene and Soh, 1970. Varunine genera known as fossils are Brachynotus from the middle Miocene of Hungary (Müller, 1974), Eriocheir from the Pliocene of Japan (Karasawa and Narita, 2000), Hemigrapsus from the Pleistocene of U.S.A. (Rathbun, 1926), Miograpsus Fleming, 1981 from the upper Miocene of New Zealand, Varuna from the middle Eocene of Jamaica (Withers, 1924), and Utica White, 1847 from the Pleistocene of Australia (Wintle, 1886). Among these genera Miograpsus is the only known extinct genus. Glaessner (1969) showed that Telphusograpsus Lorenthey, 1902, from the Eocene of Rumania, was refer- able to Varuna; however, Telphusograpsus is an independ- ent genus by virture of having an inflated carapace with two upper orbital fissures and with a distinct inner orbital angle, and lacking a posterolateral facet on the branchial region. Members of the Grapsidae lack a distinct inner orbital angle and upper orbital fissures. The genus is probably referred to the family Goneplacidae H. Milne Edwards, 1852. Withers (1924) reported Varuna ? sp. from the Eocene of Jamaica, but that occurrence was based only upon a portion of the merus of the cheliped; therefore, the systematic posi- tion of the species is doubtful. Karasawa (1993) described a new species, Varuna angustifrons, from the lower Oligocene of Japan; however, the species was moved from Varuna to Carinocarcinoides Karasawa and Fudouji, 2000 of the family Goneplacidae (Karasawa and Fudouji, 2000). Fossil records of the Cyclograpsinae comprise three gen- era, Cyclograpsus, Miosesarma and Helice, all known from the Miocene of Japan (Karasawa, 1989; Karasawa and Inoue, 1992; Karasawa, 1993; Kato, 1996). The extinct genus Palaeograpsus Bittner, 1875 has not been placed within any of the grapsid subfamilies (Glaessner, 1969). Previously known species of the genus include: Palaeograpsus attenuatus Bittner, 1875, P. Systematic status of Miosesarma Table 4. Distributions and geologic ranges of recognized fossil species of the family Grapsidae. Taxa Family Grapsidae MacLeay, 1838 Subfamily Grapsinae MacLeay, 1838 Genus Metopograpsus H. Milne Edwards, 1853 Metopograpsus traxleri Müller, 1998 Genus Pachygrapsus Randall, 1840 Pachygrapsus hungaricus Müller, 1974 Pachygrapsus sp., Morris, 1993 Genus Planes Bowdich, 1825 Planes prior (Smirnov, 1929) Subfamily Sesarminae Dana, 1851 Genus Sesarma Say, 1917 Sesarma paraensis Beurlen, 1958 Sesarma (s.l.) ? sp., Karasawa, 1993 Genus Neosarmatium Serene and Soh, 1970 Neosarmatium smithi (H. Milne Edwards, 1853) Subfamily Cyclograpsinae H. Milne Edwards, 1853 Genus Cyclograpsus H. Mine Edwards, 1837 Cyclograpsus directus Karasawa, 1989 Cyclograpsus rectangularis Karasawa, 1989 Genus Helice De Haan, 1835 Helice sp., Karasawa and Inoue, 1992 Genus Miosesarma Karasawa, 1989 Miosesarma japonicum Karasawa, 1989 Miosesarma naguraense Kato, 1996 Subfamily Varuninae H. Milne Edwards, 1853 Genus Brachynotus De Haan, 1833 Brachynotus febrarius Müller, 1974 Genus Eriocheir De Haan, 1835 Eriocheir japonica (De Haan, 1835), Karasawa and Narita, 2000 Genus Hemigrapsus Dana, 1851 Hemigrapsus oregonensis (Dana, 1851), Rathbun, 1926 Hemigrapsus nudus (Dana, 1851), Rathbun, 1926 Hemigrapsus sp., Rathbun, 1926 Genus Miograpsus Fleming, 1981 Miograpsus papaka Fleming, 1981 Genus Varuna H. Milne Edwards, 1830 Varuna ? sp., Withers, 1924 Genus Utica White, 1847 Utica haswelli Wintle, 1886 Utica yarraensis Wintle, 1886 Subfamily uncertain Genus Daragrapsus Müller and Collins, 1991 Daragrapsus trispinosus Miller and Collins, 1991 Genus Daranyia Lörenthey, 1901 Daranyia granulata Lörenthey, 1901 Daranyia fabiani Di Salvo, 1933 Genus Pseudodaranyia Tessier et al., 1999 Pseudodaranyia carinata Tessier et al., 1999 271 Range Locality L. Miocene Austria M. Miocene Hungary, Poland Pleistocene Jamaica L. Miocene Caucasus U. Oligo.- L. Mio. Brazil M. Miocene Japan Pleistocene Australia L. Miocene Japan M. Miocene Japan M. Miocene Japan L.- M. Miocene Japan M. Miocene Japan M. Miocene Hungary L. Pliocene Japan Pleistocene U.S.A. Pleistocene U.S.A. Pleistocene U.S.A. L. Miocene New Zealand M. Eocene Jamaica Pleistocene Australia Pleistocene Australia U. Eocene Hungary U. Eocene Hungary M. Eocene Italy M. Eocene Italy 272 Hiroaki Karasawa and Hisayoshi Kato bartonensis Quayle and Collins, 1981, P. depressus Quayle and Collins, 1981, P. guerini Via, 1959, P. inflatus Bittner, 1875 (type species), P. loczyanus Lörenthey, 1898 and P. parvus Müller and Collins, 1991 from the Eocene of Europe; P. bittneri Morris and Collins, 1991 from the Pliocene of Brunei. Among these, Schweitzer and Feldmann (2001) moved three species, P. bartonensis, P. bittneri and P. depressus, to the chasmocarcine genus Orthakrolophos Schweitzer and Feldmann, 2001, within the Goneplacidae. Palaeograpsus guerini is similar to members of Orthakrolophos, but is characterized by having transverse ridges on the dorsal carapace which are lacking in Orthakrolophos; therefore, Schweitzer and Feldmann (2001) did not include the species in Orthakrolophos. The species remains doubtfully placed within Palaeograpsus. In his original description of the genus, Bittner (1875) indi- cated that Palaeograpsus had a close affinity with Varuna and Pseudograpsus within the Varuninae. Via (1959) sug- gested that P. loczyanus closely resembles members of Carcinoplax H. Milne Edwards, 1852 within the Goneplacidae. Beschin et al. (1994) reported well pre- served carapaces associated with chelipeds and pereiopods of P. loczyanus. De Angeli (1995) also described cara- paces, abdominal sternites, chelipeds and pereiopods of P. inflatus, the type species of the genus. We agree with the opinion of Via (1959). Examination of their specimens and the type specimen of P. loczyanus by one of us (Karasawa) strongly suggests that Palaeograpsus should be placed within the Goneplacidae. In P. inflatus and P. loczyanus the infraorbital ridge is absent; a median depression on thoracic sternite 3 is present, and a groove between sternites 3 and 4 is deep and well defined. However, in members of the Grapsidae sternite 3 usually lacks a median depression and a well defined groove between sternites 3 and 4 is absent. Varuna and Pseudograpsus possess the infraorbital ridge which Palaeograpsus lacks, a unique character of the Varuninae. Palaeograpsus inflatus and P. loczyanus have slender meri of the pereiopods while genera within the Grapsidae usually possess broad, flattened meri. Palaeograpsus inflatus and P. loczyanus possess carapace and cheliped characters most like those of Carcinoplax. However, the male abdominal somites 3 and 4 of P. inflatus are fused, while members of Carcinoplax have seven free abdominal somites in males. The genus Daranyia Lorenthey, 1901 was found in the Eocene of Hungary (Lörenthey, 1901; Lörenthey and Beurlen, 1929) and Italy (Di Salvo, 1933). Lörenthey (1901) and Lorenthey and Beurlen (1929) compared Daranyia with the extant genus Euchirograpsus, but the genus differs from Euchirograpsus by having a wide, sinuous frontal margin and well separated anterolateral teeth. Glaessner (1969) did not classify the genus in a known subfamily. We agree with Glaessner’s opinion. Only the dorsal carapace of the genus is yet known. The subfamilial arrangement of the genus must await discovery of a ventral carapace and tho- racic sternites. Muller and Collins (1991) erected two monotypic genera, Daragrapsus and Sculptoplax, within the Grapsidae, based on material from the Hungarian Eocene. Sculptoplax does not appear to be a member of the Grapsidae. Sculptoplax resembles the xanthid genus Carpilodes Dana, 1851(= Liomera Dana, 1851; ICZN Opinion 73) (Müller and Collins,1991: 90); therefore, the genus is referred to the Xanthidae si. Müller and Collins (1991) indicated that Daragrapsus resembled Daranyia, but because the genus is represented by only a dorsal carapace specimen, subfamilial placement remains obscure. Tessier et al. (1999) described two new grapsid genera, Maingrapsus and Pseudodaranyia, from the Eocene of Italy. Although Tessier et al. (1999) compared Maingrapsus with Palaeograpsus, the systematic position of the genus is doubtful. Maingrapsus is characterized by having a strongly inflated carapace with three transverse ridges and a wide, anteriorly protruded front, and lacking the infraorbital ridge and anterolateral teeth. There is no similarity between Maingrapsus and any known extant members of the Grapsidae. The genus has a _ resemblance to Paracorallicarcinus Tessier et al.,1999, but differs in having a longer carapace without anterolateral teeth. Paracorallicarcinus possesses carapace characters like those of the extant Georgeoplax Türkay,1983 of the family Goneplacidae; however, the carapace in Paracorallicarcinus is more inflated with weak transverse ridges and bears well defined anterolateral teeth. Therefore, Maingrapsus is placed within the family Goneplacidae. The subfamilial placement of Pseudodaranyia awaits the discovery of better material. Thus 25 species in 17 genera of the family Grapsidae are recognized as fossils (Table 4). Three species in three ex- tinct genera are not referred to any known subfamilies. Only the Plagusiinae lacks fossil records. Acknowledgments We thank T. Komai (Natural Histery Museum and Institute, Chiba), P. Muller (Hungarian Geological Survey, Hungary), and C. Beshin and A. De Angeli (Museo Civico “G. Zannato", Italy) for loans of their material. We also thank T. Kimura (Nagoya University) for providing valuable information about the phylogenetic analysis, and L. B. Holthuis (National Museum of Natural History, Leiden) and D. Guinot (Muséum national d’Histoire naturelle, Paris) for providing useful infor- mation about classical literature. We are deeply indebted to C. E. Schweitzer (Kent State University, U.S.A.), C. L. McLay (University of Canterbury, New Zealand), and M. Tavares (Universidade Santa Ursula, Brazil) for reading the manuscript and providing useful comments. Special thanks are due to R. M. Feldmann (Kent State University, U.S.A.) for his review of the manuscript. The present work was partly supported by the Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture (no. 1663) for Karasawa. Travel for examination of Hungarian fossils was provided by a special fund from the Mizunami Municipal Government to Karasawa. 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H., 1924: Some Cretaceous and Tertiary decapod crustaceans from Jamaica. Annals and Magazine of Natural History, series 9, vol. 13, p. 81-93. 275 Paleontological Research, vol. 5, no. 4, pp. 277-282, December 31, 2001 © by the Palaeontological Society of Japan Age calibration of megafossil biochronology based on Early Campanian planktonic foraminifera from Hokkaido, Japan KAZUYOSHI MORIYA', HIROSHI NISHI? and KAZUSHIGE TANABE' "Department of Earth and Planetary Science, Graduate School of Science, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan (e-mail: moriya @gbs.eps.s.u-tokyo.ac.jp, tanabe@eps.s.u-tokyo.ac.jp) *Department of Earth Science, Graduate School of Social and Cultural Studies, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka, 810-8560, Japan (e-mail: hnishi@rc.kyusyu-u.ac.jp) Received 11 April 2001; Revised manuscript accepted 23 August 2001 Abstract. The occurrence of an Early Campanian planktonic foraminiferal assemblage consisting of Globotruncana arca, G. linneiana, Rosita fornicata and R. patelliformis is first reported from the Upper Haborogawa Formation exposed in the Haboro area, northwestern Hokkaido, Japan. This finding supports the previous interpretation that the Santonian/Campanian boundary can be placed at the basal part of Inoceramus (Platyceramus) japonicus Zone of the inoceramid biostratigraphy. Key words: biostratigraphy, Hokkaido, planktonic foraminifera, Santonian/Campanian boundary Introduction The Late Cretaceous ammonoid and inoceramid zonal schemes in Japan have been progressively improved by several recent biostratigraphic studies (e.g. Toshimitsu and Maiya, 1986; Toshimitsu et al., 1995a, b; Toshimitsu et al., 1998). Five standard inoceramid zones, i.e. Inoceramus (I.) uwajimensis, |. (l.) mihoensis, |. (l.) amakusensis, I. (Platy- ceramus) japonicus and Sphenoceramus schmidti- S. orientalis in ascending order have been proposed by Toshimitsu et al. (1995b) for the Coniacian to middle Campanian sequence in the Haboro area, northwestern Hokkaido. The megafossil assemblages in northwestern Hokkaido, however, lack frequently the Tethyan zonal markers, particu- larly during the Santonian to Maastrichtian intervals. This scarcity of marker species causes the international correla- tion difficult between the Tethyan and the Northwestern Pacific bioprovinces including Japan. We here report the occurrence of the Tethyan planktonic foraminiferal species Rosita patelliformis (Gandolfi) from the Cretaceous Upper Yezo Group in the Haboro area and dis- cuss age calibration of megafossil biochronology. Geological setting and lithostratigraphy The Upper Cretaceous strata exposed in the Haboro area are lithostratigraphically divided into three units, namely the Middle Yezo, Upper Yezo, and Hakobuchi Groups in ascending order (Figure 1). The Middle Yezo Group is composed of the Shirochi Formation. The Upper Yezo Group is subdivided into the Lower, Middle and Upper Haborogawa Formations. The Hakobuchi Group consists of the Pankezawa Formation. The Shirochi Formation is composed of alternating beds of sandstone and mudstone, and the Lower and Middle Haborogawa Formations consist of mudstone. The Upper Haborogawa Formation is charac- terized by two coarsening upward sequences, each of which begins with mudstones, graded to bioturbated muddy sandstones and ends with thick-bedded sandstones (Moriya and Hirano, 2001). The Pankezawa Formation is mainly composed of sandstone. As concerns the Upper Haborogawa Formation in the study area (Figures 1, 2), the thickness of the first sequence is about 550 m, while the second one is approximately about 530 m. The mudstones in the lower part of the first se- quence are intercalated with 4 to 5 cm thick, medium- bedded, fine- to medium-grained sandstones (Figure 3). The sandstone intercalations tend to be more frequent to- ward the top of the sequence. The uppermost part of the sequence represents a 10 m thick sandstone unit, named UHs1 (Toshimitsu, 1985), which is pale-green-colored, par- allel- and cross-laminated, frequently interbedded with thin mudstone of a few cm thick (Figure 3). This unit can be traced laterally as a marker horizon in the investigated area (Figure 2). The weakly laminated mudstones of the second 278 Kazuyoshi Moriya et al. JE a River Kotanbetsu River || Hakobuchi Group / Major fault ya Major anticline Upper Yezo Group ua Middle Yezo Group Figure 1. Index map and geological outline of the study area. The rectangle shows the investigated area where the type section of the Upper Haborogawa Formation is exposed. cycle overlie the unit UHs1, but the upper part of this cycle is not exposed in the investigated section (Figures 2, 3). Material and methods We collected three sediment samples from mudstones or sandy mudstones of the upper part of the Upper Haborogawa Formation at locs. RH1202 (along the Sakasa- gawa Forestry Road in the Haboro area), RH2530 and RH1202 7 Way-up determined 7x Way-up undetermined x Fossil locality Figure 2. Route map of the type section of the Upper Haborogawa Formation along the Sakasa River in the Haboro area, showing the mega- and microfossil localities. For RH numbers, refer Toshimitsu (1985). RH2531 (along the Nakafutamata River) (for RH1202 refer Figures 2, 3; for RH2530 and 2531 refer Toshimitsu, 1985, fig. 5a). In a laboratory, each sample, 1.5 kg in weight was disaggregated with hydrogen peroxide and sodium tetraphenylborate (Hanken, 1979) to extract foraminiferal specimens. The disaggregated residues were washed using 75 um sieve. All specimens larger than 125 um were identified. The illustrated planktonic foraminifera (Figure 4) yielded from loc. RH1202 are housed in the University Museum of the University of Tokyo (UMUT). Planktonic foraminiferal assemblages The following species were recognized from the upper Sakasagawa River Sectoin Haboro and Chikubetsu areas A Q Thi: | i Stratigraphic | Columnar Locality Ey ‚ashimitsu ieee) units section Sea | Selected inoceramids plank. foram. jonicus @ Globotruncana arca ° G. linneiana e I. (Platyceramus) jap = © IT Sle OIlo = | LL Sie 915 (OX 2 >|2 — | O CON Fe) Qo] & alt D15 Q Q =) Inoceramus (I.) amakusensis (Moriya and Hirano, 2001) Selected Selected a 2 inoceramids plank. foram i Inoceramids biozones (Toshimitsu et al., 1998) I. (P) japonicus Zone FO of I. (P) japonicus LO of /. (1) amakusensis G. linneiana @ R. fornicata © Marginotruncana pseudolinneiana ® |. (L) amakusensis Zone 1.(L) amakusensis e Figure 3. Biostratigraphic summary of selected mega- and microfossils in the Upper Haborogawa Formation along the Sakasa River and adjacent areas. The stratigraphic horizons of bioevents are compiled from Toshimitsu (1988), Toshimitsu et al. (1998) and Moriya and Hirano (2001; Chikubetsu area). A, sandstone; B, muddy sandstone; C, sandy mudstone; D, mudstone; E, acidic tuff. Campanian planktonic foraminifers from Japan 279 Table 1. Haborogawa Formation. List and the number of specimens of the planktonic foraminiferal specimens occurred from the upper part of the Upper For the localities of RH2530 and RH2531, see Toshimitsu (1985, fig. 5a). Species RH 2531 Archaeoglobigerina blowi A. bosquensis A. cretacea Dicarinella sp. Globigerinelloides asper Globotruncana arca Globo. cf. arca Globo. bulloides Globo. lapparenti Globo. linneiana 16 Hedbergella aff. planispira 1 Heterohelix reussi Marginotruncana pseudolinneiana 1 Rosita fornicata Rosita patelliformis part of the Upper Haborogawa Formation: Archaeoglobi- gerina blowi Pessagno, A. bosquensis Pessagno, A. cretacea (d'Orbigny), Dicarinella sp., Globigerinelloides asper (Ehrenberg), Globotruncana arca (Cushman), Globo. bulloides Vogler, Globo. lapparenti Brotzen, Globo. linneiana (d’Orbigny), Hedbergella aff. planispira (Tappan), Hetero- helix reussi (Cushman), Marginotruncana pseudolinneiana Pessagno, Rosita fornicata (Plummer), and AR. patelliformis (Table 1). In the assemblages, Globotruncana linneiana is the most abundant species at all localities, and Globotruncana bulloides is subordinate at locs. RH1202 and 2530. The mudstone sample from loc. RH1202 yielded a total of 61 well-preserved specimens of planktonic foramini- fers. Some of them identified as Globotruncana arca, G. linneiana, Rosita fornicata, and R. patelliformis, are shown in Figure 4. Among the assemblage, R. patelliformis is repre- sented by a single specimen (Table 1), but this is the first re- port of the species from Japan. This specimen is not so large, having a circular peripheral outline and less convex spiral (Figure 4.1). Although the last chamber is somewhat deformed, chambers in the final whorl are crescentic and narrow, and the surface of the test is not so undulated. Judging from these characters, the specimen is undoubtedly identified as A. patelliformis. Correlation Sliter (1989) proposed a scheme of Cretaceous planktonic foraminiferal biostratigraphy, showing the stratigraphic ranges of selected species. The planktonic foraminiferal zonation applied here is based on that study. The first oc- currence (FO) of A. fornicata is placed closed to the Coniacian/Santonian boundary. Although there are a few objections for the age of FO of Gjlobotruncana arca (Kopaevich and Salaj in Hancock and Gale, 1996), G. arca Locality RH 2530 RH 1202 17 14 8 1 3 3 6 4 10 40 15 4 125 38 1 9 8 1 and G. linneiana should appear within the uppermost Santonian Dicarinella asymetrica Zone (Caron, 1985; Sliter, 1989). The FO of R. patelliformis is placed within the Globotruncanita elevata Zone of the upper part of the Lower Campanian. The assemblage from the mudstone sample at loc. RH1202 is, therefore, assigned an age of Early Campanian, probably the G. elevata Zone. Discussion Inoceramus (Inoceramus) amakusensis Nagao and Matsumoto was obtained from bioturbated muddy sandstones at locs. RH1205 and RH1230 (Toshimitsu, 1985; Figures 2, 3). /. (Platyceramus) japonicus Nagao and Matsumoto occurs from the mudstones above the UHs1 sandstones (Toshimitsu, 1988; loc. RH 1211 in Figures 2, 3). The last occurrence (LO) of / (/.) amakusensis is recognized at about 50 m below the unit UHs1, whereas /. (P.) japonicus first appears at about 20 m above UHs1 (Toshimitsu, 1998; Moriya and Hirano, 2001). Hence, the Upper Haborogawa Formation can be biosratigraphically divided into the /. (/.) amakusensis and I. (P.) japonicus Zones, with a boundary within the UHs1 sandstones (Figure 3). Toshimitsu et al. (1998) defined the Santonian/Cam- panian boundary by the FOs of the ammonoid Submortoniceras cf. condamyi (Collignon) and a planktonic foraminifer Globotruncana arca in the Haboro area, and placed the boundary just above the UHs1 of the Upper Haborogawa Formation. Hancock (1991) initially stated that the FO of Submortoni- ceras might coincide with the Santonian/Campanian bound- ary. The evolution of Submortoniceras from Texanites was, however, later inferred to have occurred during the late Santonian (Gale et al., 1995; Hancock and Gale, 1996). Furthermore, although Kopaevich and Salaj (in Hancock and Kazuyoshi Moriya et al. Campanian planktonic foraminifers from Japan 281 Gale, 1996) emphasized that the “G. arca” which occurred from the Upper Santonian is an ancestral form of the true “G. arca”, the FO of G. arca should be placed within the upper Santonian D. asymetrica Zone (e.g., Caron, 1985; Sliter, 1989: Hancock and Gale, 1996). Therefore, the FOs of Submortoniceras and G. arca are inappropriate as the boundary markers, and these bioevents have not been adopted as Santonian/Campanian boundary criteria (Hancock and Gale, 1996). We found an Early Campanian planktonic foraminiferal as- semblage consisting of Globotruncana arca, G. linneiana, Rosita fornicata and R. patelliformis from just above the unit UHs1 of the upper part of the Upper Haborogawa Formation in the Haboro area (Figures 2, 33; loc. RH1202 along the Sakasagawa Forestry Road in the Haboro area). Toshimitsu et al. (1998) found a Late Santonian planktonic foraminiferal assemblage consisting of Globotruncana linneiana, Marginotruncana pseudolinneiana and Rosita fornicata from mudstones just below the UHs1 unit along the Miginosawa Creek. Toshimitsu et al. (1998) also described the occurrence of Globigerinelloides prairiehillensis Pessa- gno from about 200 m above the UHs1 unit along the Kotanbetsu River. Therefore, in the Haboro area, the Santonian/Campanian boundary can be temporally placed at the top of the unit UHs1. This level is very close to the boundary between the Inoceramus (l.) amakusensis Zone and the I. (Platycera- mus) japonicus Zone of the inoceramid biostratigraphy (Figure 3). Toshimitsu et al. (1998) expected to place the Santonian/Campanian boundary at the basal part of the /. (P.) japonicus Zone and our finding substantiates this idea. The K-Ar dating, furthermore, revealed that in the Horosari-zawa section of the Hobetsu area, a white acid tuff intercalated with mudstones of the lower part of the /. (P.) japonicus Zone is dated at 82.2 + 0.6 Ma (Shibata and Uchiumi, 1995; Toshimitsu et a/., 1998). The K-Ar age sup- ports the idea that the age of the I. (P.) japonicus Zone is Early Campanian. Concluding remarks In this paper, we have reported the FO of Rosita patelliformis at about 10 m above the sandstone beds UHs1 (Figures 2, 3; loc. RH1202 along the Sakasagawa Forestry Road in the Haboro area). Our new finding of this plank- tonic foraminifera suggests that the Santonian/Campanian boundary should be drawn around the horizon of the sand- stone beds UHs1, probably close to the boundary between the I. amakusensis and I. (P.) japonicus Zones as proposed by Toshimitsu et al. (1998). Hancock and Gale (1996) proposed the following Santonian/Campanian boundary criteria: (1) the lowest oc- currence of the ammonoid Placenticeras bidorsatum (Roemer), (2) the extinction level of the crinoid Marsupites testudinarius (Schlotheim), (3) the extinction in the planktonic foraminifers of Dicarinella concavata group, (4) the first occurrence (FO) of nannofossil Broinsonia parca (Stradner), and (5) the basal part of the paleomagnetic the Chron C33r. To set the Santonian/Campanian boundary pre- cisely in Japan, we need to inspect these boundary criteria for further study. Acknowledgments We are grateful to Tatsuo Oji and Kazuyoshi Endo for helpful suggestions and critical reading of the manuscript. Thanks are extended to Yasunari Shigeta and two reviewers for their valuable comments. We also express sincere grati- tude to Reishi Takashima for his kind help and suggestions during this study. The research was partly supported by the Sasakawa Scientific Research Grant from The Japan Science Society. References Birkelund, T., Hancock, J. M., Hart, M. B., Rawson, P. F., Remane, F., Robaszynski, F., Schmid, F. and Surlyk, F., 1984: Cretaceous stage boundaries-proposals. Bulletin of the Geological Society of Denmark, vol. 33, p. 3-20. Caron, M., 1985: Cretaceous planktonic foraminifera. In, Bolli, H. M., Saunders, J. B. and Perch-Nielsen, K. eds., Plankton Stratigraphy, p. 17-86. Cambridge University Press, Cambridge. Gale, A. S., Montgomery, P., Kennedy, W. J., Hancock, J. M., Burnett, J. A. and McArthur, J. M., 1995: Definition and global correlation of the Santonian-Campanian boundary. Terra Nova, vol. 7, p. 611-622. Hancock, J. M., 1991: Ammonite scales for the Cretaceous System. Cretaceous Research, vol. 12, p. 259-291. Hancock, J. M. and Gale, A. S., 1996: The Campanian Stage. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, vol. 66 (Supplement), p. 103-109. Hanken, N. -M., 1979: The use of sodium tetraphenylborate and sodium chloride in the extraction of fossils from shales. Journal of Paleontology, vol. 53, p. 738-740. Moriya, K. and Hirano, H., 2001: Cretaceous stratigraphy in the Chikubetsu area, Hokkaido. Journal of the Geologi- cal Society of Japan, vol. 107, p. 199-214. (in Japanese with English abstract) Shibata, K. and Uchiumi, S., 1995: K-Ar age result-5 new data from the Geological Survey of Japan. Bulletin of the Geological Survey of Japan, vol. 46, p. 643-650. (in Japanese with English abstract) Sliter, W. V., 1989: Biostratigraphic zonation for Cretaceous planktonic foraminifers examined in thin section. Journal of Foraminiferal Research, vol. 19, p. 1-19. Toshimitsu, S., 1985: Biostratigraphy and depositional facies of the Cretaceous in the upper reaches of the Haboro River in Hokkaido. Journal of the Geological Society of @ Figure 4. Planktonic foraminifera from the loc. RH1202 along the Sakasagawa forestry road in the Haboro area. 2a-c. Rosita fornicata (Plummer), UMUT MF 27978. patelliformis (Gandolfi), UMUT MF 27977. 1a-c. Rosita 3a-c. Globotruncana linneiana (dOrbigny), UMUT MF 27979. 4a-c. Globotruncana arca Cushman, UMUT MF 27980. 1-3, Scale bars are 100 um; 4, Scale bar is 50 um. 282 Kazuyoshi Moriya et al. Japan, vol. 91, p. 599-618. (in Japanese with English ab- stract) Toshimitsu, S., 1988: Biostratigraphy of the Upper Cretaceous Santonian Stage in Northwestern Hokkaido. Memoirs of the Faculty of Science, Kyushu University, Series D, Geology, vol. 26, p. 125-192, pls. 23-29. Toshimitsu, S. and Maiya, S., 1986: Integrated inoceramid- foraminiferal biostratigraphy of the Upper Cretaceous of. northwestern Hokkaido, Japan. Cretaceous Research, vol. 7, p. 307-326. Toshimitsu, S., Maiya, S., Inoue, Y. and Takahashi, T., 1998: Integrated megafossil-foraminiferal biostratigraphy of the Santonian to lower Campanian (Upper Cretaceous) in northwestern Hokkaido, Japan. Cretaceous Research, vol. 19, p. 69-85. Toshimitsu, S., Matsumoto, T., Noda, M., Nishida, T. and Maiya, S., 1995a: Integration of mega-, micro- and magneto-stratigraphy of the Upper Cretaceous in Japan. In, Chan,:K.-H. and Park, S.-O. eds., Environmental and Tectonic History of East and South Asia with Emphasis on Cretaceous Correlation (IGCP350). Proceedings of 15th International Symposium of Kyungpook National Univer- sity, Teagu. p. 357-370. Toshimitsu, S., Matsumoto, T., Noda, M., Nishida, T. and Maiya, S., 1995b: Towards an integrated mega-, micro- and magneto-stratigraphy of the Upper Cretaceous in Japan. Journal of the Geological Society of Japan, vol. 101, p. 19-29. (in Japanese with English abstract) Paleontological Research, vol. 5, no. 4, pp. 283-310, December 31, 2001 © by the Palaeontological Society of Japan Middle Permian brachiopods from the Moribu area, Hida Gaien Belt, central Japan JUN-ICHI TAZAWA Department of Geology, Faculty of Science, Niigata University, Niigata 950-2181, Japan (e-mail. tazawa @geo.sc.niigata-u.ac.jp) Received May 11, 2001; Revised manuscript accepted 18 September 2001 Abstract. Formation in the Moribu area, Hida Gaien Belt, central Japan. The new species are Fallaxoproductus moribuensis and The Moribu fauna is a Boreal-Tethyan mixed fauna and allied with the of which 2 are new, in 27 genera. Alispiriferella japonica. A Middle Permian (Murgabian) brachiopod fauna is described from the lower Moribu This fauna consists of 29 species, Middle Permian brachiopod faunas of central Japan (Ise in the Hida Gaien Belt), northeast Japan (South Kitakami Belt), eastern Russia (South Primorye), northeast China (Jilin) and north China (Inner Mongolia). These regions were probably a continental shelf bordering the northeastern mar- gin of the Sino-Korean block, which was present at a middle northern palaeolatitude in the Middle Permian time. Key words: Boreal-Tethyan mixed fauna, brachiopods, Hida Gaien Belt, Middle Permian, Moribu Introduction Moribu area by E. Horikoshi (and his students), Tsushima, Y. Miyake and by myself in 1985-1999. The brachiopod fauna that is the subject of this paper was recovered from the lower member of the Moribu Formation in the Moribu area, about 10 km NE of Takayama, Hida Gaien Belt, central Japan (Figure 1). The Moribu Formation was named by Isomi and Nozawa (1957) for a Permian suc- cession of the Hongo-Arakigawa area including the Moribu area. Since then the stratigraphy of the Moribu Formation has been discussed by Fujimoto et al. (1962), Yamada and Yamano (1980), Horikoshi et al. (1987), Tanase and Kasahara (1988), Tazawa (1996), and Yoshida and Tazawa (2000). Faunal data for the Moribu Formation are included in sev- eral papers, fusulinaceans by Yamada and Yamano (1980) and Tazawa et al. (1993), radiolarians by Umeda and Ezaki (1997), corals by Yamada and Yamano (1980), and brachio- pods by Horikoshi et al. (1987), Tazawa (1999a, b), and Shi and Tazawa (2001). To date, 5 fusulinacean and 3 brachio- pod species have been described. Permian brachiopods of the Hida Gaien Belt are poorly known. Only one fauna, consisting of 13 species in 12 genera, was described by Tazawa and Matsumoto (1998) from the Oguradani Formation in the Ise area, about 80 km SW of Moribu. Thus, the Moribu fauna is the second-described but more plentiful Permian brachiopod fauna in the Hida Gaien Belt. The purpose of the present study is to describe all avail- able brachiopod elements of the Moribu fauna, and to dis- cuss the age and palaeobiogeography of this fauna. The brachiopod fossils were collected from 10 localities in the specimens described in this paper are housed in the Department of Geology, Faculty of Science, Niigata University. Stratigraphy Fossil localities, geological map and columnar sections of the Moribu Formation are shown in Figures 2-4, respec- tively. The Moribu Formation is distributed in the northwest- ern part of the Moribu area, having a general trend of NE- SW, and dipping towards the NW, although there are beds striking N-S or NW-SE and dipping W to SW in the eastern part. The Moribu Formation is composed of shallow marine continental shelf sediments and lithologically subdivided into three members, the lower shale-sandstone member (550 m thick) with some conglomerate and limestone beds, the mid- die sandstone member (230 m thick) with some tuffaceous sandstone beds, and the upper shale member (more than 650 m thick) with numerous, thin sandstone layers. The total thickness of this formation is more than 1,430 m. The Moribu Formation covers the Lower to Upper Carboniferous Arakigawa Formation with an unconformity, and is in turn unconformably overlain by the Upper Cretaceous-Palaeo gene volcanic rocks (Nohi rhyolites). In general the Moribu Formation is sparsely fossiliferous. The lower member con- tains various marine invertebrate fossils, such as fusulina- ceans, corals, bryozoans, brachiopods, bivalves, gastropods and crinoids. The middle member lacks macrofossils, but 284 Jun-ichi Tazawa KANITTAKARA MIRAGE RS MOR I BU TAKAYAMA KOKUBU- CHO Figure 1. contains fusulinaceans and radiolarians in some horizons. The upper member is barren of fossils. Brachiopods are the most common macrofossils. The brachiopod fossils treated in this paper were collected from the shale, sandstone and argillaceous impure limestone of the lower member at 10 localities (HMF1, 2, 3, 5, 8, 12, 13, 14, 16 and 25) (Figure 2). The topographical and stratigraphical positions, rock types and brachiopod lists of the collecting localities are as follows (see also Figure 4): HMF1: Black shale, 10 m below the limestone of the lower member, at the left (east) bank of the lower Moribudanigawa River, 200 m S of a bridge in Moribu Village (Lat. 36° 12°41” N, Long. 137° 19° 10° E); Enteletes sp., Rhynchopora sp., Hustedia ratburiensis Waterhouse and Piyasin, Martiniopsis Sp., Blasispirifer cf. reedi (Licharew), and Alispiriferella japonica sp. nov. HMF2: Dark grey argillaceous impure limestone, 4 m above the base of the limestone of the lower member, at the right (west) bank of the lower Moribudanigawa River, 30 m SW of HMF1; Capillomesolobus sp, Transennatia gratiosa (Waagen), Reticulatia sp., Linoproductus lineatus (Waagen), Megousia sp., Cancrinella cf. spinosa Hayasaka and Minato, Urushtenoidea crenulata (Ting), Leptodus nobilis (Waagen), er zu 1162 ROSSE-KANAY AMA -dani oO = Pe oO ” x Mori wud a MOR I BU OSHIKIJI A 938 (Fig. 2) NYUKAWA-MURA Index map showing the study area. Derbyia sp., Stenoscisma margaritovi (Tschernyschew), Hustedia ratburiensis Waterhouse and Piyasin, Spiriferella lita (Fredericks), and Alispiriferella japonica sp. nov. HMF3: Black shale, 10 m above the calcareous conglomerate of the lower member, at the left bank of the middle Moribudanigawa River, 130 m W of the junction of the Kuragatani Valley and the Moribudanigawa River (Lat. 36° 13° 24° N, Long. 137° 20° 42” E); Orbiculoidea cf. jangarensis Ustritsky, Stenoscisma margaritovi (Tschernyschew), Hustedia ratburiensis Water- house and Piyasin, Martinia sp., Blasispirifer cf. reedi (Licharew), and Dielasma sp. HMF5: Grey fine-grained sandstone, 65 m below the sandstone of the middle member, at the left bank of the upper Moribudanigawa River, 250 m NW of the junction of the Suganotani Valley and the Moribudanigawa River (Lat. 36° 14° 17° N, Long. 137° 20° 29°” E); Yakovlevia kaluzinensis Fredericks, Juresania cf. juresanensis (Tschernyschew), Hustedia ratburiensis Waterhouse and Piyasin, Gypospirifer volatilis Duan and Li, and Alispiriferella japonica sp. nov. HMF®: Black shale, 20 m below the limestone of the lower member, at 75 m upper from the entrance of a small tributary in the mid- dle Moribudanigawa River, 250 m NE of HMF 12; Linoproductus lineatus (Waagen), Neospirifer cf. fasciger (Keyserling), and Alispiriferella japonica sp. nov. Middle Permian brachiopods from Moribu, central Japan 285 Figure 2. HMF12: Black shale, 5 m below the limestone of the lower member, at the left (south) bank of the middle Moribudanigawa River, 625 m E of the junction of the Mizuyagadani Valley and the Moribudanigawa River (Lat. 36° 13°20° N, Long. 137° 20° 21° E); Yakovievia kaluzinensis Fredericks, Waagenoconcha permocarbonica Ustritsky, Waagenoconcha cf. imperfecta Prendergast, Fallaxoproductus moribuensis sp. nov., Permun- daria asiatica Nakamura, Kato and Choi, Gypospirifer volatilis Duan and Li, and Alispiriferella ordinaria (Einor). HMF13: Black shale of the same horizon as HMF1, at the eastern slope facing the lower Moribudanigawa River, 500 m NNE of HMF1; Transennatia gratiosa (Waagen). HMF14: Black shale, 10 m below the limestone of the lower mem- ber, at the middle Mizushiridani Valley, 500 m SE of the junction of the Mizushiridani Valley and the Moribudanigawa River (Lat. 36° 13° 10°” N, Long. 137° 20° 12° E); Yakovlevia kaluzinensis Fredericks and Alispiriferella japonica sp. nov. HMF16: Black shale of the same horizon of HMF8, at the left (east) bank of the middle Moribudanigawa River, 125 m NE of HMF 12; Alispiriferella japonica sp. nov. HMF25: Black shale, 30m below the limestone of the lower member, at 100 m SW of HMF14; Yakovlevia kaluzinensis Fredericks and Gypospirifer volatilis Duan and Li. Nee OSHIKIUI 7 KES Index map showing the fossil localities (HMF1-3, 5, 8, 12-14, 16, 25) and the studied sections (D-®). The Moribu fauna Age and Correlation The brachiopod fauna described here includes the follow- ing 29 species assigned to 27 genera: Orbiculoidea cf. jangarensis Ustritsky, Capillomesolobus sp., Transennatia gratiosa (Waagen), Yakovlevia kaluzinensis Fredericks, Reticulatia sp., Juresania cf. juresanensis (Tschernyschew), Waagenoconcha permocarbonica Ustritsky, Waagenocon- cha cf. imperfecta Prendergast, Linoproductus lineatus (Waagen), Megousia sp., Cancrinella cf. spinosa Hayasaka and Minato, Fallaxoproductus moribuensis sp. nov. Permundaria asiatica Nakamura, Kato and _ Choi, Urushtenoidea crenulata (Ting), Leptodus nobilis (Waagen), Derbyia sp., Enteletes sp., Stenoscisma margaritovi (Tschernyschew), Rhynchopora sp., Hustedia ratburiensis Waterhouse and Piyasin, Martinia sp., Martiniopsis sp., Neospirifer cf. fasciger (Keyserling), Blasispirifer cf. reedi (Licharew), Gypospirifer volatilis Duan and Li, Spiriferella lita (Fredericks), Alispiriferella ordinaria (Einor), Alispiriferella Japonica sp. nov. and Dielasma sp. The list suggests a Middle Permian age, and certain taxa further suggest a narrower age ranging from the Murgabian 286 / fit Ail un (tae Ze at | Ze GE 2 Jun-ichi Tazawa = es / 7 I | 5 x ROSSE-KANAY AMA AG OS 7 À 4 ee es 7 OSHIKIJI 7 I \ = Figure 3. Geological map of the Moribu area (after Tazawa, Hasegawa and Yoshida, 2000). 1: Late Cretaceous and Palaeogene volcanic rocks, 2: Jurassic granitic rocks, 3: Dyke rocks, 4: Limestone of the Arakigawa and Moribu Formations, 5: Shale-dominant facies of the Moribu Formation, 6: Sandstone of the Moribu Formation, 7: Conglomerate of the Moribu Formation, 8: Arakigawa Formation (Carboniferous), 9: Rosse Formation (Devonian), 10: Unconformity, 11: Fault, 12: Concealed fault. to the Midian. Gypospirifer volatilis has been known only from the Murgabian of Inner Mongolia. Cancrinella cf. spinosa, Rhynchopora sp. and Blasispirifer cf. reedi are similar to the Murgabian species. Permundaria asiatica, Urushtenoidea crenulata, Stenoscisma margaritovi and Spiriferella lita are elsewhere known from the Murgabian- Midian. Yakovlevia kaluzinensis is known from the Kubergandian-Midian. Transennatia gratiosa occurs in the Murgabian-Dzhulfian. Waagenoconcha permocarbonica has a long range from the Middle Carboniferous to the Middle Permian, but the lineage is restricted up to the Murgabian. Linoproductus lineatus is a long ranging spe- cies from the Middle Carboniferous to the Upper Permian, but most common in the Middle Permian. Leptodus nobilis ranges into the Kubergandian-Dorashamian. Hustedia ratburiensis is recorded from the Yakhtashian-Dzhulfian. Middle Permian brachiopods from Moribu, central Japan 287 c Lu fea) = Lu = oo c Liu SI ae a Fo 9 a = = Lu = a a = [a Lu [se] = Lu = cr Lu = oO = MORIBU FORMATION SHALE SHALE-SANDSTONE ALT. SANDSTONE CONGLOMERATE CALCAREOUS CONGLOMERATE LIMESTONE Figure 4. Columnar sections of the Moribu Formation, showing the stratigraphic positions of the fossil localities (HMF1-3, 5, 8, 12-14, 16, 25). From this evidence, the Moribu fauna can be regarded as Murgabian in age. The Murgabian age assignment does not conflict with data from other fossils of the Moribu Formation. Published data on fusulinaceans indicate similar age to that shown by brachiopods. The brachiopods occur from the middie and upper parts of the lower member of the Moribu Formation, i.e., the horizons between the calcareous conglomerate of the lower member, with Pseudofusulina fusiformis (Schellwien and Dyhrenfurth) and Misellina sp., described by Yamada and Yamano (1980), and the sand- stone of the middle member, with Monodiexodina cf. matsubaishi (Fujimoto), described by Tazawa et al. (1993). These fusulinaceans confine the age of the brachiopod fauna between the Kubergandian and Murgabian. Consequently the age of the Moribu fauna is judged to be the Murgabian. In generic and specific composition, the Moribu fauna is most similar to the Middle Permian brachiopod faunas from the Oguradani Formation of the Ise area, Hida Gaien Belt, central Japan (Tazawa and Matsumoto, 1998), and the Barabash and Chandalaz Formations of South Primorye, eastern Russia (Fredericks, 1924, 1925; Licharew and Kotlyar, 1978; Koczyrkevicz, 1979a, b). Furthermore, the 288 Jun-ichi Tazawa INNER MONGOLIA \ ù NORTHEAST CHINA 5. PRIMORYE (VOZNESENKA) Ni SK HIDA GAIEN PS. PRIMORYE (SERGEBVKA) A SQUTH KITAKAMI mn KUROSEGAWA Figure 5. Palaeogeographical map in the Middle Permian time (adapted from Ziegler et al., 1996). Black areas are continental shelf. AF: Africa, AN: Antarctica, AR: Arabia, AU: Australia, E: Eurasia, G: Greenland, IC: Indochina, IN: India, L: Lhasa, M: Mongolia, NA: North America, Q: Qiangtang, SA: South America, SI: Sibumasu, SK: Sino-Korea, T: Tarim, Y: Yangtze. Middle Permian brachiopod faunas from the South Kitakami Belt (Hayasaka, 1925, 1960; Hayasaka and Minato, 1956; Nakamura et al., 1970; Nakamura, 1979; Tazawa, 1979; Tazawa et al., 2000), Jilin, northeast China (Lee et al., 1980) and Inner Mongolia, north China (Grabau, 1931; Lee and Gu, 1976; Lee et al., 1982; Duan and Li, 1985) also closely resembles the Moribu fauna in species composition. Palaeobiogeography of the fauna Palaeobiogeographically, the Moribu fauna contains rather numerous Boreal or bipolar (anti-tropical) elements, Yakovlevia kaluzinensis, Waagenoconcha permocarbonica, Waagenoconcha cf. imperfecta, Megousia sp., Cancrinella cf. spinosa, Fallaxoproductus moribuensis, Stenoscisma margaritovi, Rhynchopora sp. Hustedia ratburiensis, Blasispirifer cf. reedi, Gypospirifer volatilis, Spiriferella lita, Alispiriferella ordinaria, and Alispiriferella japonica. The Tethyan elements are also present but not abundant in this fauna. The Tethyan-type species in this fauna are Transennatia gratiosa, Permundaria asiatica, Urushtenoidea crenulata, Leptodus nobilis, and Enteletes sp. Consequently, the Moribu fauna is a mixture of the Boreal (bipolar or anti-tropical) and Tethyan elements, although the Boreal elements are predominant. The Hida Gaien Belt with the Moribu fauna is restricted geographically to a continental shelf in the transitional zone between the Boreal and Tethyan Realms in east Asia, i.e., the Inner Mongolian-Japanese Transition Zone of Tazawa (1991, 1998), which includes Inner Mongolia, northeast China, South Primorye, Hida Gaien and South Kitakami, and placed on the northeastern margin of the Sino-Korean block in the middle palaeolatitude of the Northern Hemisphere dur- ing the Permian (Figure 5). The Hida Gaien Belt was probably located between the Voznesenka Belt (Barabash- Vladivostok area) and the Sergeevka Belt (Nakhodka- Paltizansk area), and more northerly than the South Kitakami, as mentioned by Tazawa (2001). Systematic descriptions Order Lingulida Waagen, 1885 Superfamily Discinoidea Gray, 1840 Family Discinidae Gray, 1840 Genus Orbiculoidea d’Orbigny, 1847 Type species.—Orbicula forbesii Davidson, 1848. Orbiculoidea cf. jangarensis Ustritsky, 1960 Figure 6.11 Compare. — Orbiculoidea jangarensis Ustritsky, 1960, p. 98, pl. 1, figs. 10-12; Ustritsky and Tschernjak, 1963, p. 68, pl. 1, figs. 5-9; Ifanova, 1972, p. 84, pl. 1, figs. 26-27; Kalashnikov, 1983, p. 204, pl. 45, figs. 3, 4; Kalashnikov, 1993, p. 14, pl. 2, fig. 13; pl. 3, figs. 5a, b; pl. 4, figs. 3a, b. Material.—One specimen, from locality HMF3, external mould of a ventral valve, NU-B370. Middle Permian brachiopods from Moribu, central Japan 289 Remarks.—This specimen is assigned to the genus Orbiculoidea due to its elliptical outline, short pedicle open- ing (7 mm long) and numerous, fine concentric lirae on the ventral valve. The Moribu species is a large Orbiculoidea of about 30 mm in diameter, and most resembles Orbiculoidea jangarensis Ustritsky, 1960, originally described by Ustritsky (1960) from the Talatin Formation of Pay Khoy, Pechora Basin, northern Russia in size and external ornament. O. jangarensis has been known from the Upper Artinskian to the Ufimian of the Pechora Basin and Taimyr Peninsula (Ustritsky, 1960; Ustritsky and Tschernjak, 1963; Ifanova, 1972; Kalashnikov, 1983, 1993). Orbiculoidea sp. Hayasaka (1963, p. 479, figs. 1a, b), from the lower Kanokura Formation of the southern Kitakami Mountains (South Kitakami Belt), northeast Japan, is also close to the present species in size and external ornament of the ventral valve. But accurate comparison is difficult for the fragmentary specimen. Order Productida Sarytcheva and Sokolskaya, 1959 Suborder Chonetidina Muir-Wood, 1955 Superfamily Chonetoidea Bronn, 1862 Family Rugosochonetidae Muir-Wood, 1962 Subfamily Capillomesolobinae Pecar, 1986 Genus Capillomesolobus Pecar, 1986 Type species.— Capillomesolobus karavankensis Pecar, 1986. Capillomesolobus sp. Figure 6.8a-6.10 Material.—Three specimens, from locality HMF2: (1) ex- ternal and internal moulds of two ventral valves, NU-B371, 372; (2) external mould of a ventral valve, NU-B373. Description.— Shell medium size for genus, transverse outline; length about 12 mm, width 14 mm+ in the best pre- served specimen (NU-B371). Ventral valve gently and evenly convex in lateral profile; sulcus with median fold oc- cupying whole length of sulcus. External surface of ventral valve ornamented by numerous capillae, having a density of 6 per 1 mm near anterior margin. Remarks.—This species resembles the shells, described as Mesolobus sinuosa (Schellwien, 1898) by Hayasaka (1925, p. 93, pl. 5, figs. 5, 6) and Mesolobus sp. by Tazawa (1979, p. 25, pl. 4, figs. 2a, b), from the lower Kanokura Formation of the southern Kitakami Mountains, in size of ventral valve and characters of sulcus. But the Moribu specimens are inadequate for detailed comparison. Suborder Productidina Waagen, 1883 Superfamily Productoidea Gray, 1840 Family Productellidae Schuchert, 1929 Subfamily Marginiferinae Stehli, 1954 Tribe Paucispiniferini Muir-Wood and Cooper, 1960 Genus Transennatia Waterhouse, 1975 Type species.—Productus gratiosus Waagen, 1884. Transennatia gratiosa (Waagen, 1884) Figure 6.1-6.7 Productus gratiosus Waagen, 1884, p. 691, pl. 72, figs. 3-7; Diener, 1897, p. 23, pl. 3, figs. 3-7; Mansuy, 1913, p. 115, pl. 13, figs. 1a, b; Colani, 1919, p. 10, pl. 1, figs. 2a-c; Chao, 1927, p. 44, pl. 4, figs. 6-10; Chi-Thuan, 1962, p. 491, pl. 2, figs. 5-7. Productus (Dictyoclostus) gratiosus Waagen. Huang, 1933, p. 88, pl. 11, figs. 14a, b; Hayasaka, 1960, p. 49, pl. 1, fig. 8. Marginifera gratiosa (Waagen). Reed, 1944, p. 98, pl. 19, figs. 6-7. Dictyoclostus gratiosus (Waagen). Zhang and Ching, 1961, p. 411, pl. 4, figs. 12-18; Wang et al., 1964, p. 291, pl. 45, figs. 14-19. Gratiosina gratiosa (Waagen). Grant, 1976, pl. 33, figs. 19-26; Licharew and Kotlyar, 1978, pl. 12, figs. 5, 6; pl. 20, figs. 1a, b; Minato et al., 1979, pl. 61, figs. 11-13. Asioproductus gratiosus (Waagen). Yang et al., 1977, p. 350, pl. 140, figs. 5a-c; Feng and Jiang, 1978, p. 254, pl. 90, figs. 1-2; Tong, 1978, p. 228, pl. 80, figs. 7a, b; Lee et al., 1980, p. 373, pl. 164, figs. 14a-c; pl. 166, figs. 5-6. Asioproductus bellus Chan (Zhan), 1979, p. 85, pl. 6, figs. 7-13; pl. 9, figs. 8-10; text-fig. 18. Gratiosina sp. Minato et al., 1979, pl. 61, fig. 14; Tazawa, 1991, p. AIS: Transennatia gratiosus (Waagen). Liu et al., 1982, p. 185, pl. 132, figs. 9a-d; Wang et al., 1982, p. 214, pl. 92, figs. 6-8; pl. 102, figs. 4-9; Ding and Qi, 1983, p. 280, pl. 95, figs. 14a, b. Transennatia gratiosa (Waagen). Yang, 1984, p. 219, pl. 33, figs. 7a-c; Jin, 1985, pl. 4, figs. 33, 34, 45, 46; Tazawa and Matsumoto, 1998, p. 6, pl. 1, figs. 4-8; Tazawa, Takizawa and Kamada, 2000, p. 7, pl. 1, figs. 3-5; Tazawa, 2000, figs. 3.6, 3.7; Tazawa and Ibaraki, 2001, p. 7, pl. 1, figs. 1-3. Material.—Ten specimens, from localities HMF2, 13: (1) external and internal moulds of two ventral valves, NU- B374, 375; (2) external casts of two ventral valves, NU- B376, 377; (3) external mould of a ventral valve, NU-B378; (4) internal moulds of two ventral valves, NU-B379, 380; (5) external moulds of three dorsal valves, NU-B381-383. Description.— Shell small for genus, transversely sub- quadrate in outline, widest at hinge; length 9 mm, width 11 mm in the best preserved ventral valve specimen (NU- B374); length 11 mm-+, width 21 mm in the largest dorsal valve specimen (NU-B382). Ventral valve strongly and un- evenly convex in lateral profile, most convex at umbonal re- gion, slightly geniculated at anterior margin of visceral disc, with long trail; umbo small, slightly incurved; ears small, dis- tinct and pointed; sulcus narrow and deep; lateral slopes steep. Dorsal valve almost flat on visceral disc, slightly geniculated at anterior margin of visceral disc, followed by short trail; fold narrow and low. External surface of ventral valve reticulate on visceral disc, costate on trail; costae con- verging into sulcus anteriorly, having a density of 7-8 per 5 mm at midtrail; spines or spine bases not observed. External ornament of dorsal valve similar to that of opposite valve. Remarks.— Transennatia gratiosa (Waagen, 1884) was originally described by Waagen (1884) from the Wargal and Chhidru Formations of the Salt Range. The Moribu speci- mens are smaller than the Salt Range specimens, and most resemble the smaller shells of T. gratiosa, from the Middle Jun-ichi Tazawa 290 18a Middle Permian brachiopods from Moribu, central Japan 291 Permian (Murgabian-Midian) of the southern Kitakami Mountains (Hayasaka, 1960, p. 49, pl. 1, fig. 8), South Primorye, eastern Russia (Licharew and Kotlyar, 1978, pl. 12, figs. 5, 6; pl. 20, figs. 1a, b) and Heilongjiang and Jilin, northeast China (Lee ef a/., 1980, p. 373, pl. 164, figs. 14 a-c; pl. 166, figs. 5, 6). Transennatia insculpta (Grant, 1976, p. 135, pl. 32, figs. 1-37; pl. 33, figs. 1-16) from the Rat Buri Limestone of Ko Muk, southern Thailand, is close to T. gratiosa in general ap- pearance, but has wider shell and more prominent ears. Transennatia huananensis (Zhan, 1979, p. 86, pl. 6, figs. 14-16) from the Longtan Formation of Guangdong, south China, is also a small Transennatia, but the Chinese species differs from T. gratiosa in having finer costae on the ventral valve. Distribution. — Middle Permian (Murgabian-Midian) of Nepal (Kumaon Himalayas), Cambodia (Sisophon), Vietnam (Quang Tri), south China (Guangxi, Hubei and Shaanxi), northeast China (Jilin and Heilongjiang), eastern Russia (South Primorye) and Japan (Hida Gaien and South Kitakami Belts); Middle Permian (Murgabian) to Upper Permian (Dzhulfian) of Pakistan (Salt Range); Upper Permian (Dzhulfian) of south China (Sichuan, Guizhou, Guangdong, Hunan, Hubei, Jiangxi, Zhejiang and Anhui). Subfamily Plicatiferinae Muir-Wood and Cooper, 1960 Tribe Yakovleviini Waterhouse, 1975 Genus Yakovlevia Fredericks, 1925 Type species.— Yakovlevia kaluzinensis Fredericks, 1925. Yakovlevia kaluzinensis Fredericks, 1925 Figure 6.20-6.25 Chonetes (Yakovlevia) kaluzinensis Fredericks, 1925, p. 7, pl. 2, figs. 64-66. Yakovievia kaluzinensis Fredericks. Muir-Wood and Cooper, 1960, pl. 133, figs. 5, 6; Kotlyar, 1961, figs. 1-3; Licharew and Kotlyar, 1978, pl. 14, figs. 1, 2; Manankov, 1998, pl. 8, figs. 18, 19; Tazawa, 1999a, figs. 2.4-6; Tazawa, 1999b, p. 90, figs. 3.7-15; Tazawa, 2000, fig. 3.18. Yakovievia sp. Horikoshi et al., 1987, figs. 3A, B; Tazawa, 1987, fig. Nee Material.—Fourteen specimens, from localities HMF5, 12, 14, 25: (1) external mould of a dorsal valve and associated internal mould of the conjoined valve, NU-B192; (2) external and internal moulds of a ventral valve, NU-B157; (3) internal moulds of seven ventral valves, NU-B158-160, 193-196; (4) external moulds of three dorsal valves, NU-B163, 164, 191; (5) internal moulds of two dorsal valves, NU-B161, 162. Description.—Shell large for genus, transversely rectan- gular in outline, with greatest width at hinge; length about 37 mm, width about 44 mm in the smaller, but well preserved ventral valve specimen (NU-B157); length about 47mm, width about 64 mm in the largest dorsal valve specimen (NU-B191). Ventral valve gently convex on venter, strongly geniculated and followed by long trail; umbo small; ears large, prominent, but not clearly differentiated from visceral part; sulcus narrow and shallow, originating near umbo and extending to anterior margin. External ornament of ventral valve invisible except for a row of oblique spines just anterior to posterior margin. Dorsal valve almost flat on venter and strongly geniculated; fold narrow and low on anterior half of valve. External surface of dorsal valve ornamented by nu- merous fine costellae, with a density of 11-13 per 5 mm at midvalve. Ventral valve interior with a pair of small, elongate subtrigonal adductor scars and two large diductor scars; diductor scars striated anteriorly and demarcated by a strong ridge posterolaterally. Internal structures of dorsal valve obscure in the present material. Remarks. — The Moribu specimens are referred to Yakovlevia kaluzinensis Fredericks, 1925, originally de- scribed by Fredericks (1925) from the Chandalaz Formation of the Vladivostok area, South Primorye in size and shape of the shells, in particular, the transversely rectangular outline. Yakovlevia impressa (Toula, 1875, p. 236, pl. 5, figs. 1a-—c) from the Middle Permian of Spitsbergen differs from Y. kaluzinensis in having larger and more prominent ears. Distribution. —Middle Permian (Kubergandian-Midian) of southeastern Mongolia (near Mt. Dzhirem-Ula), eastern Russia (South Primorye) and central Japan (Hida Gaien Belt). Family Productidae Gray, 1840 Subfamily Dictyoclostinae Stehli, 1954 Genus Reticulatia Muir-Wood and Cooper, 1960 Type species.—Productus huecoensis King, 1931. + Figure 6. 1-7. Transennatia gratiosa (Waagen), 1: Internal mould of a ventral valve, NU-B375, 2: Internal mould of a ventral valve, NU-B374, 3: External cast of a ventral valve, NU-B377, 4: External cast of a ventral valve, NU-B376, 5: External mould of a dorsal valve, NU-B382, 6: External mould of a dorsal valve, NU-B383, 7: External mould of a dorsal valve, NU-B381, 8a-10. Capillomesolobus sp., Ba, 8b: External latex cast of ventral valve, NU-B373, (8b x2), 9: External latex cast of a ventral valve, NU-B372, (x2), 10: Internal mould of a ventral valve, NU-B371, (x2), 11. Orbiculoidea cf. jangarensis Ustritsky, external mould of a ventral valve, NU-B370, 12, 13. Reticulatia sp., 12: External mould of a dorsal valve, NU-B477, 13: External mould of a dorsal valve, NU-B476, 14a-15b. Juresania cf. juresanensis (Tschernyschew), 14a, 14b: Internal mould and external latex cast of a ventral valve, NU-B384, 15a, 15b: Internal mould and lateral view of external latex cast of a ventral valve, NU-B385, 16. Megousia sp., external mould of a dorsal valve, NU-B404, 17. Cancrinella cf. spinosa Hayasaka and Minato, external cast of a ventral valve, NU-B397, 18a-19. Linoproductus lineatus (Waagen), 18a, 18b: External mould and external latex cast of a dorsal valve, NU-B396, 19: External cast of a ventral valve, NU-B395, 20-25. Yakovlevia kaluzinensis Fredericks, 20: Internal mould of a ventral valve, NU-B158, 21: Internal mould of a ventral valve, NU-B159, 22: Internal mould of a ventral valve, NU-B160, 23: Internal mould of a ventral valve, NU-B193, 24: Internal mould of a dorsal valve, NU- B161, 25: External mould of a dorsal valve, NU-B163. (Natural size unless otherwise indicated). 292 Jun-ichi Tazawa Reticulatia sp. Figure 6.12, 6.13 Material.—Two specimens, from locality HMF2, external moulds of two dorsal valves, NU-B476, 477. Description.—Shell small for genus, slightly transverse subquadrate in outline; length about 29 mm, width about 34 mm in the larger specimen (NU-B476). Dorsal valve flat on disk, strongly geniculated and followed by short trail. External surface of dorsal valve ornamented by regular nu- merous rugae and costae on disc, costae only on trail; costae numbering 5 in 5 mm at anterior margin of disc. Internally, dorsal valve having strong cardinal process; other details not observed. Remarks.—These specimens are safely assigned to the genus Reticulatia by its shape and external ornament of the dorsal valve. However, the specific identification is difficult because of the poor preservation. Superfamily Echinoconchoidea Stehli, 1954 Family Echinoconchidae Stehli, 1954 Subfamily Juresaniinae Muir-Wood and Cooper, 1960 Tribe Juresaniini Muir-Wood and Cooper, 1960 Genus Juresania Fredericks, 1928 Type species.— Productus juresanensis Tschernyschew, 1902. Juresania cf. juresanensis (Tschernyschew, 1902) Figure 6.14a-6.15b Compare.— Productus juresanensis Tschernyschew, 1902, p. 276, 620, pl. 29, figs. 1-2; pl. 47, figs. 1-2; pl. 53, figs. 4a, b; Fredericks, 1925, p. 27, pl. 4, figs. 118, 119. Buxtonia juresanensis (Tschernyschew). Chao, 1927, p. 81, pl. 8, figs. 4-8; Czarniecki, 1969, p. 282, pl. 7, figs. 1-10; pl. 8, figs. 1-5; pl. 9, figs. 1-5; Sarytcheva and Sokolskaya, 1952, p. 102, pl. 17, fig. 117. Productus (Juresania) juresanensis (Tschernyschew). Ozaki, 1931, p. 107, pl. 10, figs. 5a-c. Productus juresanensis typicus Miloradovich, 1935, p. 79, 140, pl. 5, figs. 22-26; text-fig. 29. Juresania juresanensis (Tschernyschew). Grabau, 1936, p. 140, pl. 13, figs. 5-6; Gobbett, 1963, p. 82, pl. 4, figs. 34-37; Nakamura, 1959, p. 203, pl. 2, figs. 1a-c; Yanagida, 1967, p. 52, pl. 15, figs. 1-7; text-fig. 4; Kalashnikov, 1980, p. 40, pl. 8, figs. 10a-v; Lazarev, 1982, p. 70, pl. 8, figs. 8-11; Liu et al., 1982, p. 207, pl. 79, figs. 10a-c; Zhang et al., 1983, p. 293, pl. 131, figs. 2a, b; Zeng, 1990, p. 217, pl. 4, figs. 9a-c; Fan and He, 1999, p. 119, pl.10, figs. 9-10. Material.—Two specimens, from locality HMF5, external and internal moulds of two ventral valves, NU-B384, 385. Description.—Shell medium size for genus, longer than wide; length about 26 mm, width about 22 mm in the smaller but better preserved specimen (NU-B385). Ventral valve strongly convex in both lateral and anterior profiles, with small, convex ears, shallow sulcus and very steep. lateral slopes. External ornament of ventral valve consisting of regular concentric bands and numerous spine bases of two sizes on them; smaller spine bases sometimes occur be- tween larger ones on anterior half of valve. Remarks.—In external character the Moribu specimens resemble well the ventral valves of Juresania juresanensis (Tschernyschew, 1902), from the Lower Permian Indiga Horizon of Timan (Tschernyschew, 1902, pl. 29, figs. 1a-c) and from the Maping Limestone of Yunnan Province, south China (Grabau, 1936, pl. 13, figs. 5-6). But the poor pres- ervation of this material makes accurate comparison difficult. J. juresanensis has been described from the Middle Carboniferous (Moscovian) to the Middle Permian (Midian) of Spitsbergen, northern Russia (Novaya Zemlya, Urals, Timan, Kanin Peninsula and Moscow Basin), northern Thailand, south China (Yunnan ), northwest China (Xinjiang and Gansu), north China (Inner Mongolia, Shanxi and Shandong), eastern Russia (South Primorye), and northeast Japan (South Kitakami Belt). Tribe Waagenoconchini Muir-Wood and Cooper, 1960 Genus Waagenoconcha Chao, 1927 Type species.—Productus humboldtii d’Orbigny, 1842. Waagenoconcha permocarbonica Ustritsky, in Ustritsky and Tschernjak, 1963 Figure 7.20-7.23 Waagenoconcha permocarbonica Ustritsky, in Ustritsky and Tschernjak, 1963, p. 79, pl. 7, fig. 6; pl. 8, figs. 1-3; Lee et a/, 1980, p. 364, pl. 168, figs. 1, 6; pl. 169, figs. 3, 4; Duan and Li, 1985, p. 107, pl. 37, figs. 3-5; Shi and Waterhouse, 1996, p. 77, pl. 9, figs. 4-15; pl. 10, figs. 1-4; Tazawa, 2000, figs. 3.16, 3.17. Material.—Eight specimens, from locality HMF12: (1) ex- ternal and internal moulds of a conjoined valve, NU-B386; (2) internal moulds of a conjoined valve, NU-B387; (3) exter- nal moulds of two ventral valves, NU-B388, 389; (4) external and internal moulds of two dorsal valves, NU-B390, 391; (5) external moulds of two dorsal valves, NU-B392, 393. Description. — Shell large for genus, transverse, subrectangular in outline, with greatest width slightly anterior to midvalve; length 49 mm, width 51 mm in a ventral valve specimen (NU-B388). Ventral valve strongly convex in both lateral and anterior profiles, with steep lateral slopes; sulcus moderately developed, originating at about 8-10 mm from umbo, deepest at midvalve, and shallowing and widen- ing anteriorly. Dorsal valve with low fold, flat on visceral disc, moderately geniculated, and followed by short trail. External surface of ventral valve ornamented by irregular concentric rugae and numerous, quincuncially arranged spine bases; spine bases br ming fine at anterolateral parts; numbering 5-6 in 5 mm ut midvalve, 15-17 in 5 mm near anterior margin. External ornament of dorsal valve similar to that of opposite valve. Internal structures of both valves obscure. Remarks.—These specimens are referred to Waageno- concha permocarbonica Ustritsky, 1963, originally described by Ustritsky (in Ustritsky and Tschernjak, 1963) from the Bashkirian to the Sakmarian of Taimyr, on account of size, Middle Permian brachiopods from Moribu, central Japan 293 shape and external ornament of both valves. Waagenoconcha sp. B, described and figured by Liu and Waterhouse (1985, p. 15, pl. 2, figs. 3, 4) from the Middle Permian Zhesi (Jisu) Formation of Xiujimqingi, Inner Mongolia, differs from the present species in its less trans- verse outline. Waagenoconcha waageni (Rothpletz, 1892) from the Middle Permian of Timor is close in general outline, but it has more numerous and stronger concentric bands and coarser spine bases on the ventral valve (see Archbold and Bird, 1989, figs. 3C, D). Distribution.—Middle Carboniferous (Bashkirian) to Lower Permian (Sakmarian) of northern Russia (Taimyr); Lower Permian (Sakmarian) of western Canada (Yukon Territory); Middle Permian (Kubergandian-Murgabian) of north China (Inner Mongolia), northeast China (Jilin and Heilongjiang) and central Japan (Hida Gaien Belt). Waagenoconcha cf. imperfecta Prendergast, 1935 Figure 7.24a, 7.24b Compare.— Waagenoconcha imperfecta Prendergast, 1935, p. 15, pl. 4, figs. 1-3; Prendergast, 1943, p. 25, pl. 3, figs. 7-9; Coleman, 1957, p. 82, pl. 10, figs. 8-14; pl. 11, figs. 1-6; Tazawa, 1974b, p. 127, pl. 1, figs. 4-6; pl. 2, figs. 2-7; pl. 3, figs. 1-3; pl. 4, figs. 1-4, 7. Waagenoconcha (Wimanoconcha) imperfecta Prendergast. Arch- bold, 1993, p. 20, figs. 11A-H, 12A-K, 13A-G. Material.—One specimen, from locality HMF2, external and internal moulds of a dorsal valve, NU-B394. Remarks.—The single dorsal valve specimen from Moribu is small in size (length 27 mm, width 29 mm), almost flat on venter, with a low and wide fold on the anterior half of the valve, weakly geniculated, and ornamented by numerous, fine, quincuncially arranged spine bases, having a density of 8 per 5 mm at the midvalve. This specimen may be a young shell of Waagenoconcha imperfecta Prendergast, 1935, which has been described from the Upper Permian (Dzhulfian) Hardman Formation of the Canning Basin, west- ern Australia (Prendergast, 1935, 1943; Coleman, 1957; Archbold, 1993) and the Middle Permian (Murgabian) lower Kanokura Formation of the southern Kitakami Mountains, northeast Japan (Tazawa, 1974b). W. imperfecta is distin- guished from any other waagenoconchids by its very fine and closely arranged spine bases on both the ventral and dorsal valves. Superfamily Linoproductoidea Stehli, 1954 Family Linoproductidae Stehli, 1954 Subfamily Linoproductinae Stehli, 1954 Genus Linoproductus Chao, 1927 Type species.—Productus cora d'Orbigny, 1842. Linoproductus lineatus (Waagen, 1884) Figure 6.18a-6.19 Productus lineatus Waagen, 1884, p. 673, pl. 66, figs. 1-2; pl. 67, fig. 3; text-figs. 21a-d; Diener, 1903, p. 138, pl. 7, figs. 1a-c; Tschernyschew, 1914, p. 30, 63, pl. 10, figs. 1a-c. Productus (Linoproductus) lineatus (Waagen). Grabau, 1931, p. 293, pl. 29, figs. 25-27. Linoproductus lineatus (Waagen). Chao, 1927, p. 129, pl. 15, figs. 25-27; Ivanov, 1935, p. 105, pl. 5, fig. 6; pl. 6, figs. 1-4; Minato, 1943, p. 54, pl. 2, figs. 2-5; Sarytcheva and Sokolskaya, 1952, p. 115, pl. 21, fig. 149; Volgin, 1960, p. 70, pl. 7, figs. 2a-v; Lee and Gu, 1976, p. 259, pl. 162, fig. 10; Feng and Jiang, 1978, p. 260, pl. 92, figs. 4a, b; Licharew and Kotlyar, 1978, pl. 13, fig. 1; Tong, 1978, p. 231, pl. 81, figs. 7a, b; Lee et al., 1980, p. 376, pl. 152, fig. 13; Yang, 1984, p. 222, pl. 34, figs. 14a, b; Sremac, 1986, p. 28, pl. 9, figs. 9a-c; Wang and Yang, 1998, p. 100, pl. 16, figs. 1, 3-6. Linoproductus lineatus lineatus (Waagen). Ramovs, 1958, p. 515, 592, pl. 6, figs. 1a-c; pl. 7, figs. 1a-c; pl. 8, figs. 1a, b. Linoproductus cf. lineatus (Waagen). Yanagida, 1963, p. 74, pl. 10, figs. 8-14. Linoproductus lineata (Waagen). Ding and Qi, 1983, p. 291, pl. 99, figs. 3a-c. Material.—Two specimens, from localities HMF2, 8: (1) external cast of a ventral valve, NU-B395; (2) external mould of a dorsal valve, NU-B396. Remarks.—The specimens from Moribu are referred to Linoproductus lineatus (Waagen, 1884), originally described by Waagen (1884) from the Amb, Wargal and Chhidru Formations of the Salt Range, because of similarities in size, shape and external ornament. The ventral valve specimen (NU-B395) is elongate in outline (length 44 mm, width 40 mm), and has small ears and a shallow sulcus. The dorsal valve specimen (NU-B396) is also longer than wide, with a rather short hinge line, and ornamented by numerous costellae (8-10 per 5 mm at the midvalve) and irregular, strong concentric rugae. The type species, Linoproductus cora (d’Orbigny, 1842), from the Lower Permian of Bolivia, differs from L. lineatus in its larger, transverse shell and in having much larger ears and lacking a ventral sulcus (see Muir-Wood and Cooper, 1960, pl. 111, figs. 3-6). Distribution.—Middle Carboniferous (Moscovian) of north- east China (Jilin); Upper Carboniferous (Kasimovian- Gzhelian) of Russia (Moscow Basin and southern Fergana); Lower Permian of northwest China (Xinjiang); Lower Permian (Asselian) to Upper Permian (Dzhulfian) of Croatia, Pakistan (Salt Range), India (Spiti, Punjab Himalayas), Fergana, south China (Guizhou, Sichuan and Hubei), north- west China (Gansu), north China (Inner Mongolia), northeast China (Jilin), eastern Russia (South Primorye) and Japan (Mizukoshi in Kyushu Island and Moribu in the Hida Mountains). Subfamily Anidanthinae Waterhouse, 1968 Genus Megousia Muir-Wood and Cooper, 1960 Type species. — Megousia auriculata Muir-Wood and Cooper, 1960. Megousia sp. Figure 6.16 294 Jun-ichi Tazawa Middle Permian brachiopods from Moribu, central Japan 295 Megousia sp. Tazawa, 2000, fig. 3.3. Material.—One specimen, from locality HMF2, external mould of a dorsal valve, NU-B404. Remarks.—This specimen is safely assigned to the genus Megousia on the basis of its small size, transversely elliptical outline (length 11 mm, width 26 mm), and in having greatly developed ears with radial ornament. The Moribu species superficially resembles Megousia solita Waterhouse (1968, p. 1172, pl. 154, figs. 1-6, 8-10), from the Middle Permian Ulladulla Formation of New South Wales, eastern Australia, but the material is too poor for comparison. Megousia koizumii Nakamura (1972, p. 438, pl. 2, figs. 1, 4, 5), from the Middle Permian Kashiwadaira Formation of the Takakurayama area, Abukuma Mountains, northeast Japan, is clearly distinguished from the present species by its larger, recurved and hung down ears. Subfamily Grandaurispininae Lazarev, 1986 Genus Cancrinella Fredericks, 1928 Type species.—Productus cancrini de Verneuil, 1845. Cancrinella cf. spinosa Hayasaka and Minato, 1956 Figure 6.17 Comapare.— Productus villiersi kozlowskianus Fredericks. 96, pl. 5, figs. 10, 11. Cancrinella cancriniformis spinosa Hayasaka and Minato, 1956, p. 144, pl. 23, figs. 4a, b. Cancrinella spinosa Hayasaka and Minato. Tazawa, 1976, pl. 2, fig. 5; Minato et al., 1979, pl. 62, figs. 5-8, 11. Hayasaka, 1925, p. Material. —One specimen, from locality HMF2, external cast of a ventral valve, NU-B397. Remarks.—The fragmentarily preserved specimen is as- signed to the genus Cancrinella on the basis of its small sized ventral valve (length 18 mm+, width 16 mm+), lack- ing sulcus, and ornamented by fine concentric rugae and numerous, quincuncially arranged spine bases on the venter. This specimen can be safely assigned to the Cancrinella cancriniformis group of Grigoreva et al. (1977) by having dis- tinct rugae on the ventral valve. Within the group, the Moribu species is closely allied to Cancrinella spinosa Hayasaka and Minato, 1956, described from the Middle Permian (Murgabian) lower Kanokura Formation of the southern Kitakami Mountains (Hayasaka, 1925; Hayasaka and Minato, 1956; Tazawa, 1976; Minato et al., 1979) in size, shape and external ornament of the ventral valve. Family Monticuliferidae Muir-Wood and Cooper, 1960 Subfamily Compressoproductinae Jin and Hu, 1978 Genus Fallaxoproductus Lee, Gu and Li, 1982 Type species. — Fallaxoproductus sutungensis Lee, Gu and Li, 1982. Fallaxoproductus moribuensis sp. nov. Figure 7.12a, 7.12b Material.—Two specimens, from locality HMF12: (1) ex- ternal and internal moulds of a ventral valve (holotype), NU-B398; (2) external mould of a ventral valve, NU-B399. Diagnosis.—Shell medium size for genus, slightly elon- gate trigonal, with very fine costellae on ventral valve, having a density of 12-14 in 5 mm near anterior margin. Description.—Shell small to medium for genus, slightly elongate trigonal in outline, with short hinge, greatest width near anterior margin; length about 39 mm, width about 32 mm in the holotype (NU-B398). Ventral valve strongly con- vex on umbonal slope and slightly convex to nearly flat on anterior half of valve; beak prominent, strongly incurved, but not overhanging hinge line; without ears and sulcus. External surface of ventral valve ornamented by regular, nu- merous, fine costellae, numbering 12-14 in 5 mm near ante- rior margin; spines clustering along lateral margins; rugae completely absent. Internal structures of ventral valve ob- scure in the present material. Remarks.—Fallaxoproductus moribuensis sp. nov. can be differentiated from the type and two other described species, F. dedorus Lee, Gu and Li, 1982 and F. plenus Lee, Gu and Li, 1982, both from the Lower Permian of the Xiujimqingi area, Inner Mongolia, by its fine costellae on the ventral valve. The type species, Fallaxoproductus sutungensis Lee, Gu and Li, 1982, is much closer to F. moribuensis in size and outline of shell, but it differs from the latter in having fewer and more strong costellae on the ventral valve. # Figure 7. 1-9. Urushtenoidea crenulata (Ting), 1: Internal mould of a ventral valve, NU-B407, 2: Internal mould of a ventral valve, NU-B411, 3: Internal mould of a ventral valve, NU-B409, 4: Anterior view of internal mould of a ventral valve, NU-B405, 5a, 5b: Ventral and dorsal views of internal mould of a conjoined valve, NU-B406, 6: External mould of a dorsal valve, NU-B416, 7: External mould of a dorsal valve, NU-B415, 8: Internal mould of a dorsal valve, NU-B418, 9: Internal mould of a dorsal valve, NU-B417, 10a, 10b. Enteletes sp., internal mould of a ventral valve, NU-B430, (10b x2), 11. Derbyia sp., internal mould of a ventral valve, NU-B429, 12a, 12b. Fallaxoproductus moribuensis sp. nov., internal mould and external latex cast of a ventral valve, NU-B398 (holotype), 13-16. Leptodus nobilis (Waagen), 13: Internal mould of a ventral valve, NU-B424, 14: Internal mould of a ventral valve, NU-B427, 15: Internal mould of a ventral valve, NU-B421, 16: Internal mould of a ventral valve, NU-B426, 17a-19. Permundaria asiatica Nakamura, Kato and Choi, 17a, 17b: External latex cast and internal mould of a ventral valve, NU-B400, 18: External latex cast of a ventral valve, NU-B402, 19: External latex cast of a ventral valve, NU-B403, 20-23. Waagenoconcha permocarbonica Ustritsky, 20: External latex cast of a ven- tral valve, NU-B388, 21: External mould of a dorsal valve, NU-B392, 22a, 22b: Ventral and dorsal views of internal mould of a conjoined valve, NU-B387, 23: Internal mould of a dorsal valve, NU-B390, 24a, 24b. Waagenoconcha cf. imperfecta Prendergast, internal and ex- ternal moulds of a dorsal valve, NU-B394. (Natural size unless otherwise indicated). 296 Jun-ichi Tazawa Subfamily Schrenkiellinae Lazarev, 1986 Genus Permundaria Nakamura, Kato and Choi, 1970 Type species. — Permundaria asiatica Nakamura, Kato and Choi, 1970. Permundaria asiatica Nakamura, Kato and Choi, 1970 Figure 7.17a-7.19 Striatifera? sp. Hayasaka and Minato, 1956, p. 144, pl. 23, figs. 6, 7. Permundaria asiatica Nakamura, Kato and Choi, 1970, p. 296, pl. 2, figs. 1, 2; Tazawa, 1974a, p. 315, pl. 43, figs. 3-4; Minato et al. 1979, pl. 62, figs. 12, 13; Tazawa, 2000, fig. 3.4. Material.—Four specimens, from locality HMF12, external and internal moulds of four ventral valves, NU-B400-403. Remarks.—Among the specimens from Moribu, the larg- est ventral valve specimen (NU-B400) may have originally been about 45 mm long, and about 70 mm wide, although both the anterior portion and left half of the valve have been broken off. The valve is slightly convex in the lateral and anterior profiles, and is ornamented by irregularly developed and somewhat flexuous concentric rugae and numerous costellae, numbering 11-12 in 5 mm near the anteror mar- gin. Another specimen (NU-B403) is also an imperfect ven- tral valve, but the posterior part is well preserved. The ventral valve has a straight hinge, large and flattened ears, and a small, pointed and slightly elevated umbo. These specimens can be identified with Permundaria asiatica Nakamura, Kato and Choi, 1970 by having a small and pointed umbo, irregular and slightly flexuous rugae, and relatively coarse costellae on the ventral valves. P. asiatica was originally described by Nakamura et al. (1970, p. 296) based on two specimens, the holotype from the lower Kanokura Formation of the southern Kitakami Mountains, northeast Japan, and the paratype from the Sisophon Limestone (Yabeina Zone) of Sisophon, Cambodia. The present species is easily distinguished from the following three Permundaria species in having coarser costellae on both valves: P. sisophonensis Nakamura, Kato and Choi (1970, p. 297, pl. 2, figs. 3a, b) from the Sisophon Limestone of Cambodia, P. tenuistriata Tazawa (1974a, p. 317, pl. 43, figs. 1, 2) from the lower Kanokura Formation of the south- ern Kitakami Mountains, and P. liaoningensis Lee and Gu (in Lee et al., 1980, p. 385, pl. 172, figs. 5-8) from the Lower Permian of Liaoning and Heilongjiang, northeast China. Permundaria shizipuensis Jin, Liao and Fang (1974, p. 310, pl. 162, fig. 18) from the Maokou Formation of Guizhou, south China, differs from P. asiatica in having a massive and rounded umbo on the ventral valve. Distribution. — Middle Permian (Murgabian-Midian) of Cambodia and Japan (South Kitakami and Hida Gaien Belts). Suborder Strophalosiidina Schuchert, 1913 Superfamily Aulostegoidea Muir-Wood and Cooper, 1960 Family Aulostegidae Muir-Wood and Cooper, 1960 Subfamily Chonosteginae Muir-Wood and Cooper, 1960 Genus Urushtenoidea Jin and Hu, 1978 Type species.—Urushtenia chaoi Jin, 1963. Urushtenoidea crenulata (Ting, in Yang et al., 1962) Figure 7.1-7.9 Eomarginifera crenulata Ting, in Yang et al., 1962, p. 85, pl. 37, figs. 6 right-8. Urushtenia costata Ting, in Yang et al., 1962, p. 87, pl. 25, figs. 5-7; pl. 37, fig. 6 left. Urushtenia chenanensis Chan, in Chan (Zhan) and Lee, 1962, p. 478, 488, pl. 3, figs. 4-6; Tong, 1978, p. 218, pl. 78, figs. 16a-c. Urushtenia crenulata (Ting). Jin, 1963, p. 20, pl. 1, figs. 17-24; pl. 2, figs. 9, 10, 18-20; text-fig. 5; Yang et al, 1977, p. 335, pl. 136, figs. 11a-c; Feng and Jiang, 1978, p. 246, pl. 89, figs. 11a, b; Tong, 1978, p. 218, pl. 78, figs. 17a-c; Yang and Gao, 1996, pl. 34, figs. 7-8. Urushtenoidea chenanensis (Chan). Jin and Hu, 1978, p. 117, pl. 2, fig. 9; Hu, 1983, pl. 3, figs. 4-5. Urushtenoidea maceus (Ching). Nakamura, 1979, p. 227, pl. 1, figs. 1-4; pl. 2, figs. 1-3; Minato et al., 1979, pl. 65, figs. 8-11. Urushtenoidea crenulata (Ting). Nakamura, 1979, p. 228, pl. 1, figs. 5-9; pl. 3, figs. 1-2; Tazawa, 2000, figs. 3.10, 3.11. Uncisteges crenulata (Ting). Liu et al., 1982, p. 178, pl. 129, figs. 1a-d; Jin, 1985, pl. 6, fig. 41; Zhu, 1990, p. 74, pl. 14, figs. 4- 14; pl. 17, figs. 12, 12a. Material.—Fifteen specimens, from locality HMF2; (1) ex- ternal mould of a ventral valve and associated internal mould of conjoined valve, NU-B405; (2) internal mould of a con- joined valve, NU-B406; (3) internal moulds of six ventral valves, NU-B407-412; (4) external and internal moulds of a dorsal valve, NU-B413; (5) external moulds of three dorsal valves, NU-B414-416; (6) internal moulds of three dorsal valves, NU-B417-419. Description.—Shell medium size for genus, transversely subquadrate in outline; hinge straight, a little less than great- est width; the latter occurring at about midvalve; length 12 mm, width 19 mm in a smaller ventral valve specimen (NU-B406); length 12 mm, width 20 mm in a larger dorsal valve specimen (NU-B415). Ventral valve strongly geniculated at right angle and fol- lowed by long trail; umbo small; lateral slopes steep; ears small; sulcus low and wide, originating at midvisceral disc. External ornament of ventral valve consisting of few weak concentric rugae and costae on visceral disc, numerous costae on trail; costae regular, straight and strong on trail, with a density of 6 per 5 mm at middle of trail; anterior half of ventral trail having some concentric rugae and row of spines on costae. Dorsal valve almost flat on visceral disc, strongly geniculated, and followed by short trail; fold low and wide. External ornament of brachial valve similar to that of opposite valve, but more distinct and regular reticulate orna- ment on visceral disc. Interior of dorsal valve with a median septum, extending to midvalve, a pair of elongate muscle scars on both sides of median septum. Other internal structures not observed in the present specimens. Remarks.—These specimens are identical with Urushte- noidea crenulata (Ting, in Yang et al., 1962) in size, shape Middle Permian brachiopods from Moribu, central Japan 297 and external ornament of shell, especially the density of costae on the ventral trail. Urushtenoidea chenanensis (Chan, in Chan and Lee, 1962) is a synonym of the present species. Urushtenoidea maceus (Jin, 1963), originally described and figured as Urushtenia maceus from the Middle Permian of Hubei, Anhui, Zhejiang and Jiangsu, south China (Jin, 1963, p. 19, pl. 2, figs. 1-6) somewhat resembles U. crenulata in size and outline, but the former differs from the latter in having much finer costae on the ventral valve. Distribution. — Middle Permian (Murgabian-Midian) of Cambodia (Sisophon), south China (Guizhou, Sichuan, Hunan, Guangdong, Jiangxi, Fujian, Jiangsu, Hubei and Shaanxi), northwest China (Qinghai and Gansu), and Japan (South Kitakami and Hida Gaien Belts). Superfamily Lyttonioidea Waagen, 1883 Family Lyttoniidae Waagen, 1883 Subfamily Lyttoniinae Waagen, 1883 Genus Leptodus Kayser, 1883 Type species.—Leptodus richthofeni Kayser, 1883. Leptodus nobilis (Waagen, 1883) Figure 7.13-7.16 Lyttonia nobilis Waagen, 1883, p. 398, pl. 29, figs. 1-3; pl. 30, figs. 1, 2,5, 6, 8, 10, 11; Diener, 1897, p. 37, pl. 1, figs. 5-7; Noetling, 1904, p. 112, text-figs. 4-7; Noetling, 1905, p. 140, pl. 17, figs. 1, 2; pl. 18, figs. 1-11, text-fig. 2; Mansuy, 1913, p. 123, pl. 13, fig. 10; Mansuy, 1914, p. 32, pl. 6, figs. 7a-d; pl. 7, figs. 1a-e; Diener, 1915, p. 99, pl. 10, fig. 15; Albrecht, 1924, p. 289, figs. 1a, b; Grabau, 1931, p. 285, pl. 28, figs. 3-6; Huang, 1932, p. 89, pl. 7, figs. 9, 10; pl. 8, figs. 8, 9; pl. 9, figs. 1-8, text-figs. 8-11; Simic, 1933, p. 49, pl. 4, fig. 1. Lyttonia tenuis Waagen, 1883, p. 401, pl. 30, figs. 3, 4, 7, 9. Lyttonia sp. Yabe, 1900, p. 2, text-figs. 1, 2. Lyttonia cf. tenuis Waagen. Mansuy, 1912, p. 19, pl. 4, fig. 4; pl. 5, figs. 1a-e; Huang, 1936, p. 493, pl. 1, fig. 6. Oldhamina (Lyttonia) richthofeni var. nobilis Waagen. 1916, p. 76, pl. 4, fig. 2, text-fig. 22. Lyttonia richthofeni (Kayser). Hayasaka, 1917, p. 43, pl. 18, figs. 1-8; Hayasaka, 1922a, p. 62, pl. 11, figs. 1-6; Hayasaka, 1922b, p. 103, pl. 4, figs. 12, 13; Fredericks, 1925, p. 14, pl. 3, figs. 105-107; Licharew, 1932, p. 56, 86, pl. 1, figs. 1-16; pl. 2, figs. 1, 2,5, 7, 10, 12; pl. 3, figs. 2-7; pl. 4, figs. 1-17; pl. 5, figs. 1-4, 6; Mashiko, 1934, p. 182, text-fig. Lyttonia (Leptodus) richthofeni Kayser. Hamlet, 1928, p. 31, pl. 6, figs. 1-4. Lyttonia richthofeni forma nobilis Waagen. Licharew, 1932, p. 69, 96, pl. 2, figs. 13, 14; pl. 5, figs. 1-4, 6; text-fig. 3. Lyttonia cf. richthofeni (Kayser). Huang, 1932, p. 87, pl. 8, figs. 4a, b. Leptodus nobilis (Waagen). Wanner and Sieverts, 1935, p. 249, pl. 9, figs. 27, 28; text-figs. 16-18; Termier and Termier, 1960, p. 241, text-pl. 3, figs. 1-10; Chi-Thuan, 1961, p. 274, pl. 1, figs. 1a, b; Schréter, 1963, p. 107, pl. 3, figs. 5-8; Sarytcheva, 1964, p. 65, pl. 7, figs. 5-8; text-fig. 1; Ruzhentsev and Sarytcheva, 1965, pl. 39, figs. 6-8; Cooper and Grant, 1974, pl. 191, figs. 8, 9; Grant, 1976, pl. 43, figs. 18, 19; Lee and Gu, 1976, p. 267, Fredericks, pl. 162, figs. 1, 2; Tazawa, 1976, pl. 2, fig. 8; Yang et a/., 1977, p. 371, pl. 147, fig. 5; Feng and Jiang, 1978, p. 269, pl. 100, fig. 2; Licharew and Kotlyar, 1978, pl. 14, figs. 18-15; Jin et al, 1979, p. 82, pl. 23, fig. 15; Minato et a/., 1979, pl. 66, figs. 1, 4, 5; Zhan, 1979, p. 93, pl. 9, fig. 12; Lee et a/., 1980, p. 389, pl. 172, figs. 15, 16; Wang et al., 1982, p. 229, pl. 95, fig. 20; Zhan and Wu, 1982, pl. 4, fig. 4; Ding and Qi, 1983, p. 297, pl. 102, figs. 7, 8; Yang, 1984, p. 226, pl. 35, fig. 12; Gu and Zhu, 1985, pl. 1, figs. 31, 33, 34; Liao and Meng, 1986, p. 81, pl. 2, figs. 24, 25; Sremac, 1986, p. 30, pl. 10, figs. 1-2; Tazawa, 1987, fig. 1.11; Kotlyar, in Kotlyar and Zakharov, 1989, pl. 20, fig. 6; pl. 23, fig. 12; Liang, 1990, p. 225, pl. 40, figs. 1, 5; Tazawa and Matsumoto, 1998, p. 7, pl. 2, figs. 7-12; Tazawa et al., 1998, p. 241, figs. 2.1, 2.2; Kato et al., 1999, p. 47, figs. 4a, b; Tazawa, 2000, figs. 3.14, 3.15, 7.1a, 7.1b; Tazawa and Ibaraki, 2001, p. 11, pl. 1, figs. 7-10. Lyttonia cf. nobilis Waagen. Huang, 1936, p. 493, pl. 1, fig. 5. Leptodus cf. nobilis (Waagen). Thomas, 1957, p. 177, pl. 20, figs. 1-6. Leptodus richthofeni Kayser. Shimizu, 1961, pl. 18, figs. 14, 15; Schreter, 1963, p. 106, pl. 3, fig. 4; Sarytcheva, 1964, p. 65, pl. 7, figs. 2-4; Yang et al., 1977, p. 372, pl. 147, fig. 10; Yang, 1984, p. 226, pl. 35, fig. 11; Duan and Li, 1985, p. 119, pl. 35, figs. 17-19. Leptodus ivanovi Frederiks. Minato et al., 1979, pl. 66, fig. 3. Leptodus sp. Minato et al., 1979, pl. 66, fig. 2. Leptodus tenuis (Waagen). Yang, 1984, p. 226, pl. 35, fig. 13; Duan and Li, 1985, p. 119, pl. 35, figs. 14-16; Liang, 1990, p. 226, pl. 40, fig. 9; Zhu, 1990, p. 79, pl. 18, figs. 19-21. Leptodus sp. Tazawa, 1987, fig. 1.10. Gubleria sp. Zhu, 1990, p. 80, pl. 16, fig. 24. Material.—Nine specimens, from locality HMF2: (1) exter- nal and internal moulds of three ventral valves, NU-B420- 422; (2) external mould of a ventral valve, NU-B423; (3) in- ternal moulds of five ventral valves, NU-B424-428. Description.—Shell small to medium size for genus, elon- gate subtrigonal in outline, with greatest width near anterior margin; length 40 mm, width 32 mm in the largest specimen (NU-B424). Ventral valve almost flat, slightly convex in lat- eral and anterior profiles. Ventral valve interior with regu- larly and synmmetrically arranged lateral septa on both sides of mediam septum; lateral septa broad and solid (solidiseptate), straight to slightly arched toward front, num- bering 12 pairs in the largest specimen; interseptal spaces 2.0-2.5 mm in width; median septum highly developed. Remarks.—These specimens are relatively small in size, and seem to be immature shells of Leptodus nobilis (Waagen, 1883), originally described by Waagen (1883, p. 398) from the Wargal and Chhidru Formations of the Salt Range. The Moribu specimens externally most resemble the shells, described as Lyttonia richthofeni (Kayser) by Hayasaka (1917, p. 43, pl. 18, figs. 1-6; Hayasaka, 1922a, p. 62, pl. 11, figs. 2, 3) from the lower Kanokura Formation of the southern Kitakami Mountains. The type species, Leptodus richthofeni Kayser, 1883 from the Permian of Loping, Jiangxi Province, south China (Kayser, 1883, p. 161, pl. 21,figs.9-11; Cooper and Grant, 1974, p. 411, pl. 191, figs. 11-15) differs from L. nobilis in having a more strongly convex ventral valve, with sharp lat- 298 Jun-ichi Tazawa eral septa and much broader interseptal spaces. Distribution. —Middie Permian (Kubergandian) to Upper Permian (Dorashamian) of Hungary, Croatia, Serbia, west- ern Russia (Caucasus Mountains), Pakistan (Salt Range and Khiser Range), India (Kashmir), Nepal (Kumaon Himalayas), Cambodia, Laos, Timor, northern Australia (Port Keats), northwest China (Tibet and Qinghai), south China (Yunnan, Guangxi, Guizhou, Sichuan, Hubei, Hunan, Guangdong, Jiangxi, Fujian and Zhejiang), north China (Inner Mongolia), northeast China (Jilin and Heïongjiang), eastern Russia (South Primorye), and Japan (Imo, Kamiyasse, Matsukawa and Ogatsu in the South Kitakami Belt, Moribu and Ise in the Hida Gaien Belt, Takauchi in the Maizuru Belt and Akasaka in the Mino Belt). Order Orthotetida Waagen, 1884 Suborder Orthotetidina Waagen, 1884 Superfamily Orthotetoidea Wagen, 1884 Family Derbyiidae Stehli, 1954 Genus Derbyia Waagen, 1884 Type species.—Derbyia regularis Waagen, 1884. Derbyia sp. Figure 7.11 Derbyia sp. Tazawa, 2000, fig. 3.2. Material.—One specimen, from locality HMF2, internal mould of a ventral valve, NU-B429. Remarks.—This specimen is safely assigned to the genus Derbyia by its almost flat ventral valve, ornamented by nu- merous fine costellae and having a strong median septum 10 mm long. However, the single imperfect specimen does not allow specific assignment. Order Orthida Schuchert and Cooper, 1932 Suborder Dalmanellidina Moore, 1952 Superfamily Enteletoidea Waagen, 1884 Family Enteletidae Waagen, 1884 Genus Enteletes Fischer de Waldheim, 1825 Type species.— Enteletes glabra Fischer de Waldheim, 1830. Enteletes sp. Figure 7.10a, 7.10b Enteletes sp. Tazawa, 2000, figs. 3.1a, 3.1b. Material.—One specimen, from locality HMF1, internal mould of a ventral valve, NU-B430. Remarks.—The single ventral valve specimen of Moribu is safely assigned to the genus Enteletes by its small size (length about 10 mm, width about 11 mm), rounded elliptical outline, and having a long median septum and a pair of thin, long, subparallel dental plates, both of them extending to the midvalve. Specific identification remains difficult due to the poor preservation of the specimen. Order Rhynchonellida Kuhn, 1949 Superfamily Stenoscismatoidea Oehlert, 1887 Family Stenoscismatidae Oehlert, 1887 Genus Stenoscisma Conrad, 1839 Type species.—Terebratula schlotheimii von Buch, 1835. Stenoscisma margaritovi (Tschernyschew, 1888) Figure 8.1a-8.4 Camarophoria margaritovi Tschernyschew, 1888, p. 355, figs. 1-3; Fredericks, 1924, p. 48, pl. 1, figs. 32-42; text-fig. 4. Camarophoria humbletonensis Howse. Hayasaka, 1922a, p. 62, pl. 9, figs. 10-12; pl. 10, fig. 9; Hayasaka, 1966, p. 1226, text- figs. 6-8. Stenoscisma humbletonensis (Howse). Tazawa, 1976, pl: 2, figs. 9, 10; Minato et al., 1979, pl. 66, figs. 6-8. Stenoscisma gigantea (Diener). Lee and Gu, 1976, p. 272, pl. 176, fig. 3; pl. 177, fig. 18; Lee et al., 1980, p. 395, pl. 173, figs. 6, 8. Stenoscisma margaritovi (Tschernyschew). Licharew and Kotlyar, 1978, pl. 17, figs.7a, b; Koczyrkevicz, 1979b, p. 50, pl. 11, figs. 5, 6; Duan and Li, 1985, p. 120, pl. 43, figs. 5-8; Tazawa and Matsumoto, 1998, p. 9, pl. 2, figs. 1-5; Tazawa, 2000, fig. 3.5; Tazawa, Takizawa and Kamada, 2000, p. 10, pl. 1, figs. 7-11. Stenoscisma gigantea elongatum Lee and Su, in Lee et al., 1980, p. 395, pl. 173, figs. 1, 2. Stenoscisma purdoni (Davidson). Lee et al., 1980, p. 395, pl. 173, figs. 4, 5, 7. Material.—Five specimens, from localities HMF2, 3: (1) external cast of a conjoined valve, NU-B431; (2) external casts of three ventral valves, NU-B432-434; (3) external cast of a dorsal valve, NU-B435. Description.—Shell medium size for genus, longer than wide, with greatest width slightly anterior to midvalve; length 21 mm, width about 18 mm in the best preserved specimen (NU-B434). Ventral valve gently convex in lateral profile; umbo small; sulcus shallow; costae often bifurcating or inter- calating anteriorly, numbering 7-9 on sulcus and 6-7 on each flank. Dorsal valve moderately convex in lateral pro- file, with low fold; costae numbering 8 on fold and 6-7 on each flank. Remarks.—These specimens are poorly preserved but can be referred to Stenoscisma margaritovi (Tscherny- schew, 1888) by their narrow and elongate outline, shallow ventral sulcus and low dorsal fold, and rather numerous costae on both valves. The shells, described and figured as Stenoscisma humbletonensis (Howse, 1848) from the lower Kanokura Formation of the southern Kitakami Mountains (Hayasaka, 1922a, 1966; Tazawa, 1976; Minato et al., 1979), are re- ferred to S. margaritovi on the basis of their shallow sulcus, low fold, and many costae on both valves. An elongate species, described as Stenoscisma gigantea (Diener, 1897), S. gigantea elongatum Lee and Su, in Lee et al., 1980, and S. purdoni (Davidson, 1862) from the Middle Permian of Jilin and Heilongjiang, northeast China and Jisu (Zhesi), Inner Mongolia (Lee and Gu, 1976; Lee et al, 1980), may be conspecific with S. margaritovi . Middle Permian brachiopods from Moribu, central Japan 299 Stenoscisma tetricum Grant (1976, p. 185, pl. 50, figs. 9-28) from the Rat Buri Limestone of Ko Muk, southern Thailand is also close to S. margaritovi in size and outline, but the Thailand species is distinguished from the present species by its strong concentric laminae on both valves. Distribution. — Middle Permian (Murgabian-Midian) of north China (Inner Mongolia), northeast China (Heilongjiang and Jilin), eastern Russia (South Primorye), and Japan (South Kitakami and Hida Gaien Belts). Superfmily Rhynchoporoidea Muir-Wood, 1955 Family Rhynchoporidae Muir-Wood, 1955 Genus Rhynchopora King, 1865 Type species. — Terebratula geinitziana de Verneuil, in Murchison et al., 1845. Rhynchopora sp. Figure 8.5a-8.5c Rhynchopora sp. Shi and Tazawa, 2001, p. 756, figs. 2.2a, b. Material.—One specimen, from locality HMF1, internal mould of a conjoined valve, NU-B478. Remarks.—This specimen is safely assigned to the genus Rhynchopora by its small size (length 10 mm, width 9 mm), pentagonal outline, fine simple costae and, in particular, the high dorsal fold which originates from midvalve, has 5 costae and is sharply incurved ventrally to form almost a square-shaped, flat anterior surface at the anterior margin. The Moribu specimen well resembles Rhynchopora tchernyshae Koczyrkevicz (1979a, p. 47, pl. 11, figs. 1-4), originally described from the lower Barabash Formation of South Primorye, in size and outline of the shell, and the number of costae on the dorsal fold. But accurate compari- son is difficult for the poorly preserved specimen. Order Athyridida Boucot, Johnson and Staton, 1964 Suborder Retziidina Boucot, Johnson and Staton, 1964 Superfmily Retzioidea Waagen, 1883 Family Neoretziidae Dagis, 1972 Subfamily Hustediinae Grunt, 1986 Genus Hustedia Hall and Clarke, 1893 Type species.—Terebratula mormonii Marcou, 1858. Hustedia ratburiensis Waterhouse and Piyasin, 1970 Figure 8.6a-8.6c Hustedia ratburiensis Waterhouse and Piyasin, 1970, p. 138, pl. 23, figs. 15-30; Grant, 1976, p. 241, pl. 66, figs. 1-69; pl. 67, figs. 51-58; Sun, 1991, p. 254, pl. 6, figs. 5-8; Yanagida and Nakornsri, 1999, p. 118, pl. 32, figs.11-16. Hustedia thailandica Waterhouse and Piyasin, 1970, text-figs. 12, 13. Hustedia nakornsrii Yanagida, 1970, p. 79, pl. 14, figs. 9a-d. Material. —Four specimens, from localities HMF1, 2, 5: (1) external moulds of two ventral valves, NU-B436, 437; (2) external mould of a dorsal valve, NU-B438; (3) internal mould of a dorsal valve, NU-B439. Description.—Shell small to medium for genus, suboval in outline, with greatest width slightly anterior to midvalve; length 9 mm, width 8 mm in the larger ventral valve speci- men (NU-B436). Ventral valve moderately convex in both lateral and anterior profiles, without sulcus. External sur- face of ventral valve ornamented by simple, broad and rounded costae; 2 close-set costae medially and 3 pairs of costae laterally. Dorsal valve moderately convex in both profiles, having no fold, and ornamented by 3 costae medi- ally and 3 pairs of costae laterally; costae originating at umbo except median costa, which commences a little below umbo; outer 2 pairs of costae curved towards posterolateral margins. Internal structure of dorsal valve obscure in the present material. Remarks.—The Moribu specimens can be referred to Hustedia ratburiensis Waterhouse and Piyasin, 1970 by their external ornament, 2 close-set costae on median part of the ventral valve and 3 costae on median part of the dorsal valve, especially the median costa of the dorsal valve origi- nating a short distance below umbo. This species was described and compared in detail by Waterhouse and Piyasin (1970), Yanagida (1970) and Grant (1976). A single dorsal valve specimen, figured by Koizumi (1979, pl. 1, fig. 5) as Hustedia indica (Waagen, 1883) from the Kashiwadaira Formation of the Takakurayama area, Abukuma Mountains, northeast Japan, resembles closely H. ratburiensis in having a median costa originating slightly anterior to umbo. Distribution. — Lower Permian (Artinskian) to Upper Permian (Dzhulfian) of north-central Thailand (Khao Hin King), southern Thailand (Khao Phrik, Khao Tok Nam and Ko Muk), and central Japan (Hida Gaien Belt). Order Spiriferida Waagen, 1883 Suborder Spiriferidina Waagen, 1883 Superfamily Martinioidea Waagen, 1883 Family Martiniidae Waagen, 1883 Subfamily Martiniinae Waagen, 1883 Genus Martinia M'Coy, 1844 Type species.—Spirifer glaber Sowerby, 1820. Martinia sp. Figure 8.7a, 8.7b Material.—One specimen, from locality HMF3, internal mould of a ventral valve, NU-B440. Remarks.—This specimen is safely assigned to the genus Martinia by its transversely subelliptical ventral valve with several vascular markings radially branching out from umbonal region and extending two-thirds of the length of the valve. However, the poor preservation of this specimen prevents accurate specific identification. Family Martiniopsidae Kotlyar and Popeko, 1967 Genus Martiniopsis Waagen, 1883 Type species.—Martiniopsis inflata Waagen, 1883. Jun-ichi Tazawa 300 Middle Permian brachiopods from Moribu, central Japan 301 Martiniopsis sp. Figure 8.8, 8.9 Material.— Two specimens, from locality HMF1, internal moulds of two ventral valves, NU-B441, 442. Remarks. — These specimens are fragmentarily pre- served, but safely assigned to the genus Martiniopsis by their transversely oval outline and a pair of long adminicula reaching to the midlength of the ventral valves. The Moribu species is a medium, transverse Martiniopsis; length about 21 mm, width about 28 mm in the lager specimen (NU- B441), and most resembles Martiniopsis cathaysiensis Grabau (1936, p. 242, pl. 21, figs. 7, 8; pl. 24, figs. 9a-e), from the Maping Limestone of Guangxi and Guizhou, south China, in size and shape of the ventral valve. The single ventral valve specimen, described as M. cathaysiensis by Hayasaka (1967, p. 254, figs. 2a, b) from the lower Kanokura Formation of the southern Kitakami Mountains, is poorly preserved, and inadequate for compari- son. Superfamily Spiriferoidea King, 1846 Family Trigonotretidae Schuchert, 1893 Subfamily Neospiriferinae Waterhouse, 1968 Genus Neospirifer Fredericks, 1919 Type species.—Spirifer fasciger Keyserling, 1846. Neospirifer cf. fasciger (Keyserling, 1846) Figure 8.10a-8.10c Compare.— Spirifer fasciger Keyserling, 1846 pars, p. 231, pl. 8, fig. 3b only; Chao, 1925, p. 236, pl. 3, figs. 1-2. Spirifer (Neospirifen fasciger Keyserling. Ozaki, 1931, p. 28, pl. 1, figs. 3-6. Neospirifer fasciger (Keyserling). Archbold and Thomas, 1984 pars, figs. 1F, H, I, 2C only; Poletaev, 1997, pl. 4, figs. 2-7. Material.—One specimen, from locality HMF8, external mould of a conjoined valve, NU-B443. Remarks.—The material available is a single imperfect shell lacking the anterior and lateral parts. This specimen is safely assigned to the genus Neospirifer because of its distinct fasciculate costae on the lateral slopes of both valves. Externally the Moribu specimen most resembles the shells of Neospirifer fasciger (Keyserling, 1846), described from the Upper Carboniferous of Gansu and Shanxi, north China and Jilin and Liaoning, northeast China (Chao, 1925; Ozaki, 1931). The lectotype of N. fasciger, designated by Cooper and Grant (1976, p. 2173) and refigured by Archbold and Thomas (1984, figs. 1F-I, 2C) and Poletaev (1997, pl. 4, figs. 3b-3d) is also close to the pre- sent specimen in size, outline and ornament of the brachial valve. The present material is, however, too imperfect for comparison. Genus Blasispirifer Kulikov, 1950 Type species.—Spirifer blasii de Verneuil, 1845. Blasispirifer cf. reedi (Licharew, in Licharew and Kotlyar, 1978) Figure 8.11a-8.13 Spirifer cf. reedi Licharew. Shi and Tazawa, 2001, p. 756, figs. 2.4-6. Material.— Three specimens, from localities HMF1, 3: (1) internal mould of a conjoined valve, NU-B479; (2) internal mould of a ventral valve, NU-B480; (3) internal mould of a dorsal valve, NU-B481. Description.—Shell small for genus, slightly transverse, rounded rhomboidal in outline, with narrow hinge; length 13 mm, width 14 mm in a dorsal valve specimen (NU-B481). Ventral valve with a narrow and deep sulcus. Dorsal valve having a narrow but distinct fold; costae mostly simple, but weakly bundled in the innermost pair bounding fold; number- ing 9-12 on each slope, 5-6 on fold in dorsal valve. Internally ventral valve lacking dental plates. Dorsal valve with no crural plates. Remarks.—These specimens are safely assigned to the genus Blasispirifer by their small, rounded rhomboidal shell, fine, weakly bundled costae on dorsal valve, and lacking both dental plates and crural plates. In size and shape, the Moribu specimens most resemble Blasispirifer reedi + Figure 8. 1a-4. Stenoscisma margaritovi (Tschernyschew), 1a, 1b: Ventral and dorsal views of external cast of a conjoined valve, NU-B431, 2: External cast of a ventral valve, NU-B434, 3: External cast of a ventral valve, NU-B433, 4: External cast of a ventral valve, NU-B432, 5a-5c. Rhynchopora sp., dorsal and anterior views of internal mould of a conjoined valve, NU-B478, (5b, 5c x2), 6a-6c. Hustedia ratburiensis Waterhouse and Piyasin, 6a, 6b: External latex cast of a dorsal valve, NU-B438, (6b x2), 6c: External cast of a ventral valve, NU-B436, (x2), 7a, 7b. Martinia sp., internal mould of a ventral valve, NU-B440, (7b x2), 8, 9. Martiniopsis sp., internal moulds of two ventral valves, NU-B442, 441, 10a-10c. Neospirifer cf. fasciger (Keyserling), ventral, posterior and dorsal views of exter- nal latex cast of a conjoined valve, NU-B443, 11a-13. Blasispirifer cf. reedi (Licharew), 11a, 11b: Internal mould of a dorsal valve, NU-B481, (11b x2), 12a, 12b: Ventral and dorsal views of internal mould of a conjoined valve, NU-B479, 13: Internal mould of a ventral valve, NU-B480, 14a-14c. Alispiriferella ordinaria (Einor), external and internal latex casts and internal mould of a ventral valve, NU- B458, 15-18. Alispiriferella japonica sp. nov., 15: Internal mould of a ventral valve, NU-B462, 16a, 16b: External and internal latex casts of a ventral valve, NU-B461 (holotype), 17: Posterior view of external latex cast of a conjoined valve, NU-B460, 18: External latex cast of a ventral valve, NU-B465, 19-22. Spiriferella lita (Fredericks), 19: External cast of a dorsal valve, NU-B455, 20: External cast of a dor- sal valve, NU-B452, 21: External cast of a dorsal valve, NU-B456, 22: External cast of a ventral valve, NU-B451, 23-26. Gypospirifer volatilis Duan and Li, 23: External latex cast of a ventral valve, NU-B444, 24: External latex cast of a dorsal valve, NU-B449, 25: Internal mould of a ventral valve, NU-B448, 26: External latex cast of a ventral valve, NU-B445, 27, 28. Dielasma sp., external latex casts of two ventral valves, NU-B475, 474. (Natural size unless otherwise indicated). 302 Jun-ichi Tazawa (Licharew, 1978), originally described by Licharew (in Licharew and Kotlyar, 1978, p. 73, pl. 21, figs. 13a, b, v) from the Chandalaz Formation of South Primorye. Accurate comparison is difficult due to the lack of clear external information in the present material. Genus Gypospirifer Cooper and Grant, 1976 Type species. — Gypospirifer nelsoni Cooper and Grant, 1976. Gypospirifer volatilis Duan and Li, 1985 Figure 8.23-8.26 Gypospirifer volatilis Duan and Li, 1985, p. 127, 207, pl. 48, figs. 1-2; pl. 49, figs. 1-2. Gypospirifer sp. Tazawa, 2000, figs. 3.12, 3.13. Material. — Seven specimens, from localities HMF5, 12, 25: (1) external moulds of a conjoined valve, NU-B444; (2) external moulds of three ventral valves, NU-B445-447; (3) internal mould of a ventral valve, NU-B448; (4) external and internal moulds of a dorsal valve, NU-B449; (5) external mould of a dorsal valve, NU-B450. Description.—Shell medium to large for genus, trans- versely semielliptical in outline, with greatest width at hinge, and slightly alate; length 42 mm, width about 73 mm in the best preserved specimen (NU-B445). Ventral valve gently convex in lateral and anterior profiles, most convex at umbonal region; umbo slightly extended and strongly incurved; sulcus very deep and rapidly widening anteriorly, with U-shaped bottom. External surface of ven- tral valve ornamented by numerous fine costae and concen- tric ornament of some rugae and numerous fine growth lines; costae subridged, added by bifurcation, and weakly fasciculated, numbering 9-10 in 10 mm at about midvalve, 7-8 in 10 mm at anterior margin. Dorsal valve gently con- vex in both profiles, having a high and narrow fold. External ornament of dorsal valve identical to opposite valve. Ventral interior with a pair of thick, short dental plates and a deeply impressed, large, heart-shaped muscle field. Other internal structures not preserved. Remarks.—These specimens are referred to Gypospirifer volatilis Duan and Li, 1985, originally described from the Middle Permian Zhesi (Jisu) Formation of the Zhesi area, Inner Mongolia, by their size, outline and surface ornament of shells, especially the deep ventral sulcus and high dorsal fold. Gypospirifer marcoui (Waagen, 1883, p. 510, pl. 47, figs. 1-3) from the Amb and Wargal Formations of the Salt Range most resembles G. volatilis, but differs from the latter in hav- ing a shallower ventral sulcus and a lower dorsal fold. The type species, G. nelsoni Cooper and Grant (1976, p. 2214, pl. 591, figs. 8-9) from the Hueco Formation of west Texas is clearly distinguished from G. volatilis by its more transverse shell, shallower ventral sulcus and lower dorsal fold. Distribution.—Middle Permian (Murgabian) of north China (Inner Mongolia) and central Japan (Hida Gaien Belt). Family Spiriferellidae Waterhouse, 1968 Subfamily Spiriferellinae Waterhouse, 1968 Genus Spiriferella Tschernyschew, 1902 Type species.—Spirifer saranae de Verneuil, 1845. Spiriferella lita (Fredericks, 1924) Figure 8.19-8.22 Spirifer saranae mut. lita Fredericks, 1924, p. 36, pl. 1, figs. 16-27; Hayasaka, 1925, p. 98, pl. 5, fig. 14. Spiriferella lita (Fredericks). Tazawa, 1979, p. 28, pl. 4, figs. 12-13; pl. 5, figs. 1-4, 6; Tazawa, 2000, fig. 3.9. Material.—Seven specimens, from locality HMF2: (1) ex- ternal cast of a ventral valve, NU-B451; (2) external mould and casts of three dorsal valves, NU-B452-454; (3) external casts of three dorsal valves, NU-B455-457. Description.—Shell medium size for genus, transversely trapezoidal in outline; cardinal extremities blunt, produced; hinge straight, equal to widest part; length about 40 mm, width 68 mm+ in a dorsal valve specimen (NU-B457); length about 27 mm, width 43 mm in the best preserved dor- sal valve specimen (NU-B452). Ventral valve having a deep, wide, V-shaped and smooth-bottomed sulcus and 5 strong, simple costae on each side of sulcus. Dorsal valve moderately convex in both lateral and anterior profiles, with a high fold and 5-6 simple or slightly bifurcated costae on each side of fold; fold having a median groove. Remarks. — Spiriferella lita (Fredericks, 1924), originally described from the Middle Permian of Ussuri, South Primorye, is characterized by its strong and simple costae on the ventral valve, especially the enormously large costae on both sides of the sulcus. The material available consists of a fragmentarily preserved ventral valve and six incom- plete dorsal valves. These specimens can be assigned to S. litaon account of their large, transverse shells with strong and simple costae on the ventral valve. Spiriferella keilhavii (von Buch, 1846), from the Middle Permian of Bear Island, is also a large, transverse Spiriferella, but it differs from S. lita by its weakly fasciculate costae on both valves. Distribution. — Middle Permian (Murgabian-Midian) of eastern Russia (South Primorye) and Japan (South Kitakami and Hida Gaien Belts). Genus Alispiriferella Waterhouse and Waddington, 1982 Type species.—Spiriferella ordinaria Einor, 1939. Alispiriferella ordinaria (Einor, in Licharew and Einor, 1939) Figure 8.14a-8.14c Spirifer (Spiriferella) keilhavi var. ordinaria Einor, in Licharew and Einor, 1939, p. 140, pl. 23, figs. 6, 7; pl. 24, figs. 1a-d. Spiriferella ordinaria Einor. Nelson and Johnson, 1968, p. 738, pl. 95, figs. 5, 6; pl. 96, figs. 4-6; text-figs. 10, 13a; Bamber and Waterhouse, 1971, pl. 15, figs. 10, 12-14; Waterhouse et al., 1978, pl. 2, figs. 6-8. Middle Permian brachiopods from Moribu, central Japan 303 Alispiriferella ordinaria (Einor). Waterhouse and Waddington, 1982, p. 30, pl. 2, figs. 7-13; text-figs. 11i, j, 20; Abramov and Grigorjeva, 1988, p. 158, pl. 22, figs. 7a-g; pl. 25, figs. 4, 5; Shi and Waterhouse, 1996, p. 133, pl. 25, figs. 11-15; text-fig. 46. Material_—Two specimens, from locality HMF12: (1) ex- ternal and internal moulds of a ventral valve, NU-B458; (2) external mould of a dorsal valve with internal moulds of a conjoined valve, NU-B459. Description. — Shell small to medium for genus, slightly wider than long, subpentagonal in outline, with greatest width at hinge; length about 31 mm, width about 37 mm in the better preserved specimen (NU-B458). Ventral valve moderately convex in lateral profile, most convex at posterior third of shell length; cardinal extremities blunt, produced; interarea moderately high, triangular in shape and slightly concave; sulcus deep and having smooth, broad, V-shaped bottom; 4 pairs of broad, rounded, simple or bifurcated costae on ventral valve. Dorsal valve having a low fold, with a deep, wide, flat-bottomed median groove for almost entire length; 4 pairs of bifurcated or tri- furcated costae on dorsal valve. Ventral valve interior with a pair of high dental plates and a deeply impressed heart-shaped muscle field. Other inter- nal structures not observed in the present material. Remarks.—The Moribu specimens are not so well pre- served but they can be identified with Alispiriferella ordinaria (Einor, 1939) by their small, slightly wider subpentagonal shell, with weakly bundled costae on both ventral and dorsal valves. This species was originally described by Einor (in Licharew and Einor, 1939) from the Lower Permian of Novaya Zemlya, and afterwards redescribed by Waterhouse and Waddington (1982) as the type species of the genus Alispiriferella. Distribution. — Lower Permian (Asselian) to Middle Permian (Murgabian) of the Arctic Russia (Novaya Zemlya, western Verkhoyansk Range), northern Canada (Yukon Territory) and central Japan (Hida Gaien Belt). Alispiriferella japonica sp. nov. Figure 8.15-8.18 Spiriferella sp. Horikoshi et al., 1987, p. 142; Tazawa, 1987, text- figs. 1.1, 1.3. Alispiriferella sp. Tazawa, 2000, fig. 3.8. Material. —Fourteen specimens, from localities HMF1, 2, 5, 8, 14, 16: (1) external mould of a conjoined valve, NU- B460; (2) external and internal moulds of three ventral valves, NU-B461 (holotype), 462, 463; (3) external moulds of eight ventral valves, NU-B464-471; (4) internal moulds of two dorsal valves, NU-B472, 473. Diagnosis.—Small, transversely much wider Alispiriferella with alate cardinal extremities, smooth ventral sulcus and coarse, simple and rounded costae on both valves. Description. — Shell small for genus, alate, transversely subquadrate in outline, with greatest width at hinge; length 21 mm, width 39 mm in the largest specimen (NU-B465); length 18 mm, width about 32 mm in the holotype (NU- B461). Ventral valve strongly convex in lateral profile, most con- vex at umbonal region; umbo well extended and strongly incurved; interarea moderately high, nearly triangular in shape; cardinal extremities slightly produced; sulcus deep and wide, having smooth, rounded bottom; costae broad and simple with rounded crest, numbering 4-5 on each flank of ventral valve. Dorsal valve moderately convex in lateral profile; fold originating at beak and having a narrow but dis- tinct median groove, which extends from umbo to anterior margin; each flank having 3-4 coarse, simple and rounded costae. Ventral valve interior with high dental plates and a deeply impressed heart-shaped muscle field; the latter is longitudi- nally striated and divided into two parts by a low ridge with a median narrow groove. Dorsal valve interior obscure in the present material. Remarks. — Alispiriferella japonica sp. nov. is distin- guished from Alispiriferella ordinaria (Einor, 1939) by its more alate and wider outline, smooth noncostate ventral sulcus and coarse, simple costae on both valves. The present species somewhat resembles Alispiriferella sp. Yanagida (1996, figs. 2.2, 2.4) from the Middle Permian Tsunemori Formation of Akiyoshi, southwest Japan in hav- ing transverse shell, broad, simple costae on both valves, and dorsal fold with a narrow median groove. The Akiyoshi species is unfortunately represented by only two incomplete specimens, and an accurate comparison is therefore ham- pered. Alispiriferella gydalensis (Zavodowsky, 1968, p. 159, pl. 46, fig. 1) from the Middle Permian Omolon Horizon (corre- lated with the Kungurian) of the Kolyma River region, north- eastern Siberia, differs from A. japonica in having a much larger shell and dorsal fold with a wide, shallow median groove. Order Terebratulida Waagen, 1883 Suborder Terebratulidina Waagen, 1883 Superfamily Dielasmatoidea Schuchert, 1913 Family Dielasmatidae Schuchert, 1913 Subfamily Dielasmatinae Schuchert, 1913 Genus Dielasma King, 1859 Type species. — Terebratulites elongatus Schlotheim, 1816. Dielasma sp. Figure 8.27, 8.28 Material. —Two specimens, from locality HMF3, external moulds of two ventral valves, NU-B474, 475. Description. — Shell medium size for genus, elongate subpentagonal in outline, almost flat to slightly concave in both lateral and anterior profiles; length 29 mm, width 15 mm in the larger specimen (NU-B474). Ventral valve with nar- row but distinct median fold, originating slightly anterior to umbo and extending to anterior margin. External surface of ventral valve smooth. Remarks. —This species may be a new species of Dielasma. The Moribu species resembles Dielasma sp. B, described by Yang et al. (1962, p. 118, pl. 46, figs. 8a-c) 304 Jun-ichi Tazawa from the Middle (?) Permian of Qilianshan Mountains, Qinghai, northwest China, in size and shape of the ventral valve and in having a narrow, distinct median fold on the ventral valve. Dielasma biplex Waagen (1882, p. 349, pl. 25, figs. 3-5) from the Wargal Formation of the Salt Range also has a nar- row median ventral fold, but it is clearly distinguished from the Moribu species by its strongly convex ventral valve. Acknowledgements | would like to thank Guang R. 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B., 1996: Permian world topography and climate. /n, Martini, |. P., ed., Late glacial and Postglacial Environmental Changes - Quaternary, Carboniferous-Permian and Proterozoic, p. 1-37, Oxford University Press, New York. Paleontological Research, vol. 5, no. 4, pp. 311-318, December 31, 2001 © by the Palaeontological Society of Japan A phosphatized cephalopod mouthpart from the Upper Pennsylvanian of Oklahoma, U.S.A. KAZUSHIGE TANABE’, ROYAL H. MAPES? and DAVID L. KIDDER? "Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan (e-mail: tanabe @eps.s.u-tokyo.ac.jp) “Department of Geological Sciences, Ohio University, Athens, Ohio 45701, U.S.A. (e-mail: mapes@ohiou.edu, kidder @ ohiou. edu) Received 27 August 2001; Revised manuscript accepted 2 November 2001 Abstract. An exceptionally well-preserved cephalopod mouthpart was discovered in a phosphate concretion from the lower Missourian (Upper Pennsylvanian) in Tulsa, Oklahoma, U. S. A. It con- sists of an almost complete jaw apparatus and a radula, both of which are in the living orientation. The black upper and lower jaws, preserved as phosphate, were probably chitinous. The lower jaw is slightly larger than the upper and is characterized by a widely open outer lamella. The upper jaw is built up of a large outer lamella and a short, scallop-shaped inner lamella; the former is distinctly divided into two portions in the posterior region. The radula is preserved in the anterior portion of the buccal cavity; it is made of more than ten rows of teeth, each consisting of seven tooth ele- ments with a pair of marginal plates. The overall features of the jaws and radula are essentially similar to those described in association with ammonoids rather than nautiloids and coleoids, sug- gesting that this mouthpart can be referred to the Ammonoidea. However, the lower jaw in our specimen differs from previously described mandibles of Carboniferous Gastrioceratoidea, Neoglyphioceratoidea, Gonioloboceratoidea, and Dimorphoceratoidea in its less elongate outline. For this reason, we refer the cephalopod mouthpart to the Ammonoidea other than the above superfamilies with reservation. Key words: Ammonoidea, cephalopod mouthpart, Oklahoma, Upper Pennsylvanian Introduction All exatnt cephalopods possess a well-developed buccal mass in the proximal portion of the digestive system. The organic hard tissues of the cephalopod buccal mass consist of upper and lower jaws (beaks or mandibles) and a radula, all of which are surrounded by well-developed jaw-radular musculature. Fossilized remains of jaws and radula are rarely found in body chambers of ectocochliate cephalopod shells, especially of ammonoids and in the soft tissue re- mains of coleoids (see Tanabe and Fukuda, 1999, for a re- cent review). As Mapes (1987) has briefly documented, the marine Carboniferous in the U.S. Midcontinent occasionally yields goniatite conchs preserving jaws and a radula within their body chambers (Saunders and Richardson, 1979; Tanabe and Mapes, 1995; Doguzhaeva et al, 1997). These goniatites occur in carbonate and phosphate concre- tions, together with occasional isolated cephalopod jaws and even more rarely radulae. In this article, an exceptionally preserved cephalopod mouthpart from the Upper Pennsylvanian of Oklahoma is described and its possible taxonomic relationship is discussed on the basis of compari- son with the jaws and radulae of extant and fossil cephalo- pods. Material and its geologic setting The cephalopod mouthpart examined was preserved as a nucleus in a small spherical phosphate concretion (ca. 15 mm in diameter) that was recovered by one of us (RHM) from the Lower Missourian (Upper Pennsylvanian) on the southern side of Tulsa, Tulsa County, Oklahoma. The con- cretion came from an approximately 3 m thick stratigraphic sequence that consists of three distinct black platy shales that were exposed at the northeast corner of the junction of the 71st Street and the U.S. Highway 75 in the southern part of Tulsa, Tulsa County, Oklahoma (SW1/4, SW1/4, sec. 2, T. 18 N., R. 12E.: Supulpa 71/2 minute quadrangle; Figure 1). These shales were deposited in marine water under oxygen-stressed conditions that occurred during three dis- tinct times of marine transgression and regression (Boardman, personal commun., 2001). The stratigraphic 312 Kazushige Tanabe et al. ets Ray RIESE HT Nes = UE = a En D er * \ i : ox N SIE AS | A) Se i NG? À DPA Ss DA | i ZAI STH 5 : 7 5 | ake a: fe u ÿ, Oh for 1e Jenks HI, Index map of the southern part of Tulsa, Figure 1. Oklahoma, showing the locality of the cephalopod mouthpart re- main examined. assignment by Boardman et al. (1995, see localities OKM- 28 and 56, p.86, although the reported coordinates they pro- vide are incorrect) places these shale units in the lowest three cycles of the basal Missourian in the northern Midcontinent. All of the shales belong to the Coffeyville Formation, and the stratigraphic assignments for the three shale beds from oldest to youngest are the basal Tacket Shale, the lower Tacket Shale (= Mound City Member, Hertha Formation of Kansas) and the upper Tacket Shale (= Huspuckney Member, Swope Limestone of Kansas). The exposure originally extended laterally for about 100 m and was covered by thousands of phosphate concretions that were eroding from the three black platy shales. Initial collections were made of the loose specimens on the sur- face without regard to stratigraphic position. In about 1990, prior to a field expedition to recollect and sample the expo- sure stratigraphically, the Oklahoma Highway Department of Transportation grassed the exposure, and it is not collect- able at this time. The cephalopod mouthpart specimen examined is housed in the Zoological Collection of Ohio University (OUZC). Notes on preservational conditions It has been reported that some phosphate concretions from some Carboniferous Midcontinent black shales contain both mineralized skeletal material (bones and shells) and less commonly preserved softer organs (cephalopod mouthparts) of invertebrates (for mouthpart reports see Closs, 1967; Mapes, 1987; Tanabe and Mapes, 1995; Dogushaeva et al., 1997). The reasons why and how phos- phate preserves the soft tissue remains in this geologic set- ting has not been addressed. Because of the lack of in situ phosphate concretions from this Oklahoma locality, a de- tailed study of these specimens to solve the above problems is not warranted at this time. However, it is possible to make some general exterior and internal observations about the concretions from this exposure to help explain the preserva- tion. There are five concretion types classified on the basis of shape (flat and spheroidal) and on surface texture (smooth, rough, and bioturbated). The five concretion types are: 1) spheroidal with a smooth exterior, 2) flat with a smooth exte- rior, 3) spheroidal with a rough exterior, 4) flat with a rough exterior, and 5) bioturbated nodules which bear no body fos- sils. The cephalopod mouthparts that form the basis of this paper and most of the fossil material from this locality are preserved in the type 1 concretions. Although no system- atic characterization of the nodule types was linked to the outcrop stratigraphy during initial collections in the early 1990s, the lowest shale (basal Tacket Shale Member) ap- peared to contain the most fossiliferous concretions. The internal fabric of the concretions probably controls the surface texture and one of these fabrics lent itself particularly well to fossil preservation. Fecal pellets are common in these coprolite-dominated phosphate nodules. Both of the smooth-surfaced concretions (types 1 and 2) have a tightly packed, pelletal fabric without interstitial calcite cement; whereas, the two rough-surfaced types contain loosely Well-preserved mouthpart in unaltered coprolitic material Poorly-preserved mouthpart in altered coprolitic material 4 = early cement (e.g. phosphate) 1 later calcite cement Figure 2. Schematic illustration of pelletal coprolites. 1. Tightly packed pelletal fabric that was cemented early enough to favor high-quality fossil preservation. 2. Calcite-cemented and loosely packed fabric that resulted in a rough surface exterior. Relatively poor fossil preservation characterizes these concre- tions probably because of later calcite cement that precipitated with infiltration of fluids that altered the coprolite and its enclosed fossils. Upper Pennsylvanian cephalopod mouthpart 313 DORSAL JOIY31LNV U Oo 12) en m po) Oo D VENTRAL Figure 3. Dorsal (1) and left lateral (2) views of the phosphatized cephalopod mouthpart examined, and the reconstructed diagram of the jaw apparatus (anterolateral view) (3). Ohio University Zoological Collection, OUZC 4001. Abbreviations. ouj: outer lamella of upper jaw, iuj: inner lamella of upper jaw, olj: outer lamella of lower jaw, ilj: inner lamella of lower jaw, r: radula. packed pellets and conspicuous interstitial calcite cement. The tight packing of pellets probably resulted in part from rapid, early diagenetic phosphate cementation of these con- cretions that sealed the concretions and favored high-quality fossil preservation by restricting entry of later pore fluids (Figure 2.1). Softness of pellets may also be a preserva- tional factor, but analysis for that is beyond the scope of this report. The calcite cementation and loose packing of the rough concretions which contain poorly preserved fossils are interpreted as the result of infiltration of later diagenetic fos- sil-altering fluids (Figure 2.2). Based on these observations, it seems apparent that the mode of phosphate and carbonate preservation will control some of the preservational potential of cephalopod mouthparts. However, detailed studies of carefully collected concretions will be required to resolve some of these preservational variables. Description of the cephalopod mouthpart Methods of observations.— The cephalopod mouthpart from the Tacket Shale (Tacket specimen) was coated with platinum and examined by means of a Hitachi model S2400 scanning electron microscope. SEM images of the jaws and radula were transferred to a desktop computer via a PCI interface, and different portions of them were reorganized into a few images using imaging software (Quartz PCI and Adobe Photoshop, Ver. 5). They were printed out using a high-resolution digital photo-printer (Fuji Film Pictrography, model 3500). Ss) ~ ® o Q © < cs F o =) JS ao =) N © SZ Upper Pennsylvanian cephalopod mouthpart 315 For determination of upper and lower jaws, we follow the criteria described by Lehmann (1976, 1990), Nixon (1988a, 1996), and Tanabe and Fukuda (1999), who relied upon the comparison with the jaws of extant cephalopods. Overall morphology.— The Tacket specimen, of about 11.5 mm maximum length and 7 mm width, consists of an al- most complete jaw apparatus and a radula (Figure 3.1, 3.2). The ventral margin of the upper jaw fits well with the dorsal margin of the lower jaw. The anterior portion of the lower jaw is partly eroded and/or corroded, and where the mandi- ble is missing, a radular ribbon is exposed in the buccal cav- ity between the jaws (r in Figure 3.2). These observations indicate that the jaws and radula have been fossilized by keeping their original life orientation as a complete buccal mass. Upper jaw.—The upper jaw is made of a black material which was probably originally chitinous. It consists of a large outer lamella and a short inner lamella, which are joined in the anterior portion; the former, though the anterior portion is missing due to weathering, is distinctly divided into two wing portions in the posterior region (Figure 3.1). The open angle of the wings is about 45°. The dorsal margin of the paired wing portions exhibits a sharp ridge-like elevation. This elevation can be traced to the anterior portion where two wing portions are connected by a slightly concave outer lamellar element (Figure 4.4). The inner shorter lamella is scallop-shaped and is prominently convex dorsally (Figure 4.1, 4.2). The anterior portion is partly missing, but the re- constructed outline suggests that this portion appears to be sharply pointed (Figure 3.3). The inner lamella is orna- mented with dense concentric lirae (Figure 4.1-4.3). The outer lamella lacks growth lines and instead retains a deli- cate pattern represented by numerous honeycomb-like po- lygonal pits (Figure 4.5, 4.6). Each pit, about 8-12 um diameter, is surrounded by a sharp ridge (Figure 4.6). In view of their shape and distribution, these pits are undoubt- edly comparable to the anchor-type polygonal imprints of co- lumnar cells (becublasts) that are present on the outer side of the upper jaw and on the inner side of the lower jaw in ex- tant coleoids (Dilley and Nixon, 1976). Lower jaw.—As in the upper jaw, the lower jaw is made of a black, probably originally chitinous material without any trace of a calcareous element. It is slightly larger than the upper jaw (Figure 3.2), and consists of a large outer lamella and a short inner lamella, though the inner one is partly visi- ble from outside in the eroded anterior buccal cavity (ilj; Figures 3.2, 3.3). The two lamellae are connected to each other in the anterior portion. The outer lamella is curved posteriorly, with an open angle of about 50 degrees. Its outer surface is sculptured by regular-spaced, concentric un- dulations, which become finer and denser toward the poste- rior margin (Figure 3.2). Radula.—The exposed radula comprises a total of 13 rows of teeth, retaining their original orientation. Each transverse row, about 2.5 mm wide, consists of seven tooth elements (a central rhachidian tooth, two paired lateral teeth, and a pair of marginal teeth), with a pair of marginal plates (Figures 5.1, 5.2). The shape of the rhachidian tooth is un- clear because it is hidden by lateral teeth. The paired inner and outer lateral teeth are unicuspid, asymmetrical in frontal view and project markedly toward the anterodorsal side; the former is much shorter than the latter. The paired marginal teeth are the longest in the tooth elements and unicuspid as are the lateral teeth. The marginal plate has an oval outline. Taxonomic relationships The isolated cephalopod mouthpart from the Tacket Shale exhibits several characteristic features including 1) a radula consisting of a total of seven tooth elements in each row, 2) an upper jaw being build up of a short, scallop-shaped inner lamella and a large outer lamella that is distinctly divided into two portions in the posterior region, 3) a lower jaw being made of a widely open outer lamella and a shortly reduced inner lamella, 4) absence of a calcareous jaw element, and 5) presence of coleoid-type polygonal imprints of beccublasts on the upper jaw lamella. These observations provide a reliable basis to infer the taxonomic relationship of the mouthpart owner by comparison with the radulae and jaws of extant and fossil cephalopods (Table 1). The upper jaw in our specimen is distinguished from those of extant coleoids and Nautilus in that the outer and inner lamellae of the latter are never divided into two wing portions (Clarke, 1986; Nixon, 1988a, b; Tanabe and Fukuda, 1999). Among the extant and fossil cephalopods, upper jaws with paired la- mellae are only known from ammonoids (Tanabe and Fukuda, 1999, fig. 19.3). The three-dimensional architec- ture of the upper jaws of Goniatitina and Ceratitina is still un- clear due to relatively poor fossil preservation. Bandel (1988, fig. 6) and Zakharov (1974, fig. 2B), respectively, re- constructed the upper jaws of the Upper Paleozoic goniatite (Eoasianites) and the early Triassic ceratite (Olenekites), as consisting of a widely opened, well-developed outer lamella and a short, reduced inner lamella. Later, Doguzhaeva et al. (1997) interpreted that the upper jaw of Girtyoceras (Carboniferous Goniatitina) is made of a large inner lamella and a short outer lamella, though they did not present an il- lustration showing this construction. The structure of the upper jaw in the Tacket specimen correlates well with the re- construction of the upper jaws of goniatites and ceratites by Bandel (1988) and Zakharov (1974). Unlike the upper jaws of Goniatitina and Ceratitina, those of most Jurassic and Cretaceous ammonoids consist of a large inner lamella with paired lateral walls and a short, reduced outer lamella, though the two lamellae appear to be united as a single la- mella in Late Cretaceous Ancyloceratina (e. g. Jeletzkytes; @ Figure 4. Upper jaw of the phosphatized cephalopod mouthpart examined. 3: Closeup of 2, showing the fine concentric lirae. 4. Part of anterior of the scallop-shaped short inner lamella with concentric fine lirae. portion showing the outer lamella (ouj) with a strong lateral ridge and marginal portion of the inner lamella (iuj). 1, 2: Anterior (frontal) (1) and right lateral (2) views 5. Outer surface of the left lateral portion of the outer lamella ornamented with numerous honeycomb-like imprints of beccublasts. 6. Closeup of imprints of beccublasts on the jaw plate, each surrounded by a sharp ridge. 316 Kazushige Tanabe et al. Figure 5. 1. Anterior view of the radular ribbon preserved in the buccal cavity which is partly covered with the inner lamella of the lower jaw (lj). 2. Diagram showing the frontal view of a transverse row of the radula. Abbreviations. R: central rachidian tooth, L1: inner lateral tooth, L2: outer lateral tooth, M1: marginal tooth, MP: marginal plate. Table 1. Upper Pennsylvanian cephalopod mouthpart 317 Comparison of the morphological features of buccal structure in extant and fossil cephalopods (modified from Tanabe and Fukuda, 1999). Upper jaw elements Lower jaw elements Beccublast Radular teeth Cephalopod taxa Rostrum Lamellae Rostrum Inner lamella Calcite cover imprints in each row Recent Nautilus calcified non-divided calcified shortly reduced partly present micropores 9 Recent Coleoidea non-calcified non-divided non-calcified projected absent polygonal pits 7 posteriorly Ammonoidea Goniatitina non-calcified divided calcified? shortly reduced absent polygonal pits 7 Ceratitina non-calcified divided non-calcified shortly reduced absent unknown unknown Phylloceratina unknown unknown calcified shortly reduced absent unknown unknown Lytoceratina unknown unknown calcified shortly reduced absent polygonal pits unknown Ammonitina non-calcified non-calcified non-calcified shortly reduced present polygonal pits 7 or absent Ancyloceratina non-calcified non-calcified non-calcified shortly reduced present unknown 7 Present specimen non-calcified non-calcified non-calcified shortly reduced absent polygonal pits 7 Landman and Waage 1993, figs. 37, 39-41; Subptycho- ceras; Tanabe and Landman, 2001, text-fig. 2. 6). The lower jaw of the Tacket specimen is similar in the de- velopment of a large outer lamella to those of Upper Paleozoic Goniatitina such as Eoasianites (Neoicocera- toidea, Neoicoceratidae; Closs, 1967, fig. 4; Bandel, 1988, fig. 6), Cravenoceras (Neoglyphioceratoidea, Cravenocera- tidae; Mapes, 1987, fig. 3.3, 3.4; Tanabe and Mapes, 1995, figs. 2-2, 3), Wiedeyoceras (Gonioloboceratoidea, Wiedeyo- ceratidae; Saunders and Richardson, 1979, fig. 7), and Girtyoceras (Dimorphoceratoidea, Girtyoceratidae; Doguz- haeva et al., 1997, fig. 4), but in the latter, the outer lamellae are much more elongated posteriorly than in the former (we follow Bogoslovskaya et al., 1999 for higher taxonomy of each genus). The lower jaw of an indeterminate goniatite (not Girtyoceras limatum as reported in Doguzhaeva et al. 1997, fig. 2C, D) possesses a calcified rostrum, but such cal- cification has not yet been observed in the lower jaws of other Goniatitina and the Tacket specimen. The radula in the Tacket specimen is allied to those of Goniatitina (e.g. Eoasianites; Lehmann, 1976, fig. 72; Tanabe and Mapes, 1995, figs. 2-4, 4-2; Cravenoceras; Tanabe and Mapes, 1995, figs. 2-3, 4-1; Girtyoceras; Doguzhaeva et al., 1997, figs. 5A, 6A) in the number of tooth elements in each row and the overall shape of each tooth, though there are some variations in the relative length of marginal and lateral teeth. Also, polygonal imprints of beccublasts observed in the upper jaw of our specimen have been found on the upper jaw lamella of Girtyoceras (Doguzhaeva et al., 1997, figs. 5B) as well as on the inside surface of the lower jaws of Gaudryceras (Cretaceous Lytoceratina; Tanabe and Fukuda, 1983, figs. 2, 3) and an unidentified aspidoceratid (Upper Jurassic Ammonitina; Tanabe and Fukuda, 1999, fig. 19.5D). To summarize the above comparison, the overall features and structure of the jaws and radula in the Tacket specimen show an affinity to those described from the Upper Paleozoic Goniatitina, although, there is a marked difference in the lower jaw shape of the Tacket specimen and other described goniatite mandibles. Because of this difference in lower jaw shape, we refer the Tacket cephalopod mouthpart to the Ammonoidea and to a superfamily other than the Gastrioceratoidea, Neoglyphioceratoidea, Goniolobocera- toidea, and Dimorphoceratoidea with reservation. Acknowledgments We thank N. H. Landman and H. Maeda for critical review and D. Boardman for his aid in determining the stratigraphic position ofthe three shale units. Thanks are extended to A. P. Bennison who discovered the exposure and brought it to the attention of RHM. This work was supported by the sci- entific research grant from the Japan Society for Promotion of Science (no. 12440141 for 2000-2001). References Bandel, K., 1988: Operculum and buccal mass of ammonites. In, Wiedmann, J. and Kullmann, J. eds., Cephalopods- Present and Past, p. 653-678. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart. Boardman, D. R., Work, D. M., Mapes, R. H. and Barrick, J. E., 1994: Biostratigraphy of Middle and Late Pennsylvanian (Desmoinesian-Virgilian) ammonoids. Kansas Geological Survey Bulletin, vol. 232, p. 1-121. Bogoslovskaya, M. F., Kuzina, L. F. and Leonova, T. B., 1999: Klassifikatsiya i rasprostranenie pozdnepaleozoyskikh ammonoidey (Classification and distribution of Late Paleozoic ammonoids). /n, Rozanov, A. Yu. and Shevyrev, A. A.eds., Iskopaemye Cefalopody: Noveyshie dostizheniya v ikh izuchenii (Fossil Cephalopods: Recent Advances in Their Study), p. 89-124. Russian Academy of Sciences, Paleontological Institute, Moscow. (in Russian with English abstract) Clarke, M. R., 1986: A Handbook for the Identification of Cephalopod Beaks, 273 p. Clarendon Press, Oxford. Closs, D., 1967: Goniatiten mit Radula und Kieferapparat in der Itarar& Formation von Uruguay. Paläontologische Zeitschrift, vol. 41, p. 19-37. 318 Dilly, P. N. and Nixon, M., 1976: The cells that secrete the beaks in octopods and squids (Mollusca, Cephalopoda). Cell and Tissue Research, vol. 167, p. 229-241. Doguzhaeva, L. A., Mapes, R. H. and Mutvei, H., 1997: Beaks and radulae of Early Carboniferous goniatites. Lethaia, vol. 30, p. 305-313. Landman, N. H. and Waage, K. M., 1993: Scaphitid ammon- ites of the Upper Cretaceous (Maastrichtian) Fox Hills Formation in South Dakota and Wyoming. Bulletin of the American Museum of Natural History, vol. 215, p. 1-257. Lehmann, U., 1976: Ammoniten. Ihr Leben und ihre Umwelt, 171 p. Ferdinand Enke Verlag, Stuttgart. Lehamnn, U., 1990: Ammonoideen, 257 p. Ferdinand Enke Verlag, Stuttgart. Mapes, R.H., 1987: Upper Paleozoic cephalopod mandibles: frequency of occurrence, modes of preservation, and paleoecological implications. Journal of Paleontology, vol. 61, p. 521-538. Nixon, M., 1988a: The buccal mass of fossil and recent Cephalopoda. /n, Clarke, M. R. and Trueman, E. E. eds., The Mollusca, Paleontology and Neontology of Cephalopods, Vol. 12, p. 103-122. Academic Press, San Diego. Nixon, M., 1988b: The feeding mechanisms and diets of cephalopods-living and fossil. /n, Wiedmann, J. and Kullmann, J. eds., Cephalopods-Present and Past, p. 633 - 644. Schweizerbartsche Verlagsbuchhandlung, Stuttgart. Kazushige Tanabe et al. Nixon, M., 1996: Morphology of the jaws and radula in ammonoids. /n, Landman, N. H., Tanabe, K. and Davis, R. A. eds., Ammonoid Paleobiology, p. 23-42. Plenum Press, New York. Saunders, W. B. and Richardson, E. S. Jr., 1979: Middle Pennsylvanian (Desmoinesian) Cephalopoda of the Mazon Creek Fauna, Northeastern Illinois. /n, Nitecki, M. R. ed., Mazon Creek Fossils, p. 333-359. Academic Press, New York. Tanabe, K. and Fukuda, Y., 1983: Buccal mass structure of the Cretaceous ammonite Gaudryceras. Lethaia, vol. 16, p. 249-256. Tanabe, K. and Fukuda, Y., 1999: Morphology and function of cephalopod buccal mass. /n, Savazzi, E. ed., Functional Morphology of the Invertebrate Skeleton, p. 245-262. John Wiley & Sons, London. Tanabe, K. and Landman, N. H., 2001: Morphological diversity of the jaws of Cretaceous Ammonoidea. Proceedings of the 5th International Symposium, Cephalopods-Present and Past, Vienna, 1999. Abhandlungen der Geologischen Bundesanstalt, vol. 57, p. 157-165. Tanabe, K. and Mapes, R. H., 1995: Jaws and radula of the Carboniferous ammonoid Cravenoceras. Journal of Paleontology, vol. 69, p. 703-707. Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey. Paleontologicheskii Zhurnal, 1974, no. 4, p. 127-129. (in Russian) Paleontological Research, vol. 5, no. 4, pp. 319-330, December 31, 2001 © by the Palaeontological Society of Japan Taxonomic and phylogenetic aspects of the shell ultrastructure of nine Cretaceous rhynchonellide brachiopod genera NEDA MOTCHUROVA-DEKOVA Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan (present address: National Museum of Natural History, 1, Tsar Osvoboditel Blvd., 1000 Sofia, Bulgaria) (e-mail: dekov@gea.uni-sofia.bg) Received 1 April 2001; Revised manuscript accepted 5 November 2001 Abstract. The shell ultrastructure of nine Cretaceous rhynchonellide brachiopod genera was stud- ied using SEM with the purpose of finding additional criteria for the taxonomy and phylogeny of Late Cretaceous rhynchonellides. basiliolidine type structure of the secondary shell. The genus Orbirhynchia is characterized by a coarse fibrous The genera Cyclothyris, Cretirhynchia, Septatoechia, Belbekella, Lamellaerhynchia, Almerarhynchia, Burrirhynchia and Grasirhynchia have a fine fibrous rhynchonellidine type structure. An outline of some diagnostic characteristics for each genus is presented. Some diagenetic alterations of the shell, such as silicification and recrystallization are also discussed. Key words: Cretaceous, rhynchonellide brachiopods, shell ultrastructure, systematics Introduction Over the last four decades the shell ultrastructure of brachiopods has been extensively studied in order to throw light on the process of biomineralization. Since the contri- butions of Williams (1968a,b), MacKinnon (1974), and Smirnova (1984) shell ultrastructure has been used as an additional criterion for taxonomic and phylogenetic pur- poses. Shell ultrastructure of some Mesozoic rhynchonelli- des has been sporadically studied since the 1970's: Triassic - by Dagys (1974), Michalik (1993); Jurassic - by Baker (1971), Kamyshan (1977, 1986), Kamyshan and Adel (1979), Taddei Ruggiero and Ungaro (1983); Lower Cretaceous - by Smirnova (1984). The shell ultrastructure of Late Cretaceous rhynchonellide brachiopod genera is poorly known. For the first time Nekvasilova (1974) briefly mentioned differences in the mo- saic elements between the Late Cretaceous genera Orbirhynchia Pettitt and Cretirhynchia Pettitt. A short sum- mary on some Late Cretaceous representatives from the Lesser Caucasus was published by Ali-zade et al. (1981), but without any illustrations. Gaspard (1990a, 1990b, 1996 etc.) published some illustrations of the microstructure of several species of the genus Cyclothyris McCoy, with em- phasis on the growth patterns and effects of diagenesis. Motchurova-Dekova (1992) reported preliminary results on the shell ultrastructure of the genera Cyclothyris and Orbirhynchia. Recently the ultrastructure of some repre- sentatives of Erymnaria Cooper and the new genus Costerymnaria Motchurova-Dekova and Taddei Ruggiero was studied (Motchurova-Dekova and Taddei Ruggiero, 2000). The purpose of this paper is to describe the shell mi- crostructure of additional Cretaceous rhynchonellide genera with emphasis on Late Cretaceous representatives. New characters are found, increasing the possibility of using shell microstructure as an additional criterion in taxonomy and phylogeny. Material and methods A comparative ultrastructural SEM analysis has been car- ried out on nine Cretaceous rhynchonellide genera. Depending on the available material, some genera were in- vestigated extensively (Orbirhynchia, Cyclothyris, Cretirhyn- chia, Septatoechia), while others were examined briefly for comparative purposes (Belbekella, Lamellaerhynchia, Almerarhynchia, Burrirhynchia, Grasirhynchia). This pre- liminary study aims at discerning only certain general fea- tures. More detailed results will be published later. Of importance in any ultrastructural comparison is the need for consistency in the location of longitudinal and trans- verse sections of adult shells. The sections should be the same for all specimens in order to be able to compare the ultrastructural details between different specimens. 320 Neda Motchurova-Dekova For the present study SEM analyses were carried out on fifty transverse shell sections from thirty-four specimens be- longing to twenty-nine species of nine Cretaceous rhynchonellide genera. In most specimens usually only two very close transverse sections of both valves were observed for each specimen. The sections were cut perpendicular to the plane of symmetry. Following the recommendation of Sass and Monroe (1967) the sections were made at the maximum width of the valves. In some specimens one of the sections was made more posteriorly and crossed the muscle field. Longitudinal sections in the plane of symmetry, made before this study, gave only general information about the thickness of the shell and the calcitic layers along the shell length and the length of the fibres. The primary layer was normally affected by diagenetic processes and/or was not well preserved. Thus the charac- teristics of the secondary layer were mainly used as diag- nostic features. The measurements of the cross-sections of fibres were taken in the central part of the transverse sec- tion. Because the long axes of fibres are usually inclined to the shell surface at about 10°, the real values of the width and thickness of the fibres presented here could be slightly overestimated. This usually holds true for all measure- ments taken, so principally it should not affect the way of comparison because similar values are compared. The longer axis in the cross-sections of the fibres, usually parallel to the shell surface, is the width (W) of the fibre; the shorter axis, perpendicular to the longer axis, is the thick- ness (T) of the fibre. A coefficient “C” is introduced here representing the ratio between the width and the thickness of the fibre in the cross-section. “C,” is the ratio W/T in the larger fibres, which usually make up the main part of the shell. “C2” is the ratio W/T of the thinner fibres, usually building the outer or the innermost sublayer of fibres in the shell, or forming thin bands of finer fibres inside the section. The shape of the cross-sections of the fibres and the differ- entiation of the secondary layer were used as additional di- agnostic criteria. The reported W and T values, measured at the central part of the maximum width section of each specimen, were compared. The range of their variation (lowest and highest values) was taken into consideration. The following is a brief summary of the results. Detailed data about the occurrences of the mentioned species can be found in the cited references. When a species is first men- tioned here, the name of the collection is given and open no- menclature is used in some cases. Abbreviations: NHM - Natural History Museum London; NMNHS - National Museum of Natural History-Sofia. Observations and results All studied fossil rhynchonellides are impunctate and com- posed of two calcitic layers - primary microgranular and sec- ondary fibrous (Figure 1A). The previously described tertiary prismatic layer in the genus Cyclothyris (Motchurova- Dekova, 1992, 1994) was not observed. observations showed instead that a row of large calcite prisms, perpendicular to the internal surface was developed in many specimens. Though they look like a prismatic layer, they are a result of diagenetic calcite formation Extensive SEM. (Figures 1B, 2A, D). Recrystallized diagenetic calcite prisms forming a pseudo-tertiary layer were also observed in lenses in the interior of the secondary layer (Figure 5B). Such extensive SEM observations of the diagenetic altera- tions of the shell and the observation of this type of pseudo “tertiary layer’ which is a result of secondary diagenetic processes, call into question the report of a tertiary layer in some rhynchonellides. The periostracum is rarely preserved in fossil material. Gaspard (1982) reported a remarkable preservation of the organic cover of the Cretaceous terebratulid Sellithyris. Casts of periostraca on the external shell surface of living and fossil brachiopods are more frequently found. In the course of the present study neither of the above states of preservation of the periostracum were observed. However, in a particular spot of a transverse section of Cyclothyris difforms, the primary microgranular layer is overlain by an extremely thin calcite layer, only 2-10 um thick (Figure 1D- F). It could be possibly interpreted as a diagenetically formed calcitic pseudomorph on the organic periostracum. The primary layer is composed of isometric or elongate microgranular calcitic prisms perpendicular or slightly in- clined to the shell surface. In most specimens the primary layer is fully or partly recrystallized (Figure 3F). It is inter- esting to note that in shells affected by strong silicification the primary layer is usually not silicified (Figure 1C, D). This is because the primary layer is not porous and is more com- pact than the fibrous layer when the organic sheets in the secondary layer are dissolved during early diagenesis. The secondary layer is built up of fibres with long axes subperpendicular to the growth lines of the shell. The fibres display variable shapes in cross-section. The shape may be rhomboidal or parallelogram with variously outlined sides and angles (Figure 2E); or may have an anvil-like outline, formed by two arcs - larger and smaller, connected laterally by two sides; or the small arc can be missing (Figures 3F, 5D). Those species characterized by more isometric rhom- bic cross-sections of the fibres have lower values of the co- efficient C, whereas species with fibres that are anisometric (elongate) anvil-like or rhombic in sections have higher val- ues of C. In some specimens the secondary layer is strongly silicified (Figures 1B, 5F). When the silicification is not complete, siliceous pseudomorphs of the organic sheets are observed, representing a high relief silica grid envelop- ing the fibres (Figure 1E, 2E). In this case it is considered that the fibres, although recrystallized, have preserved their original shape. Orbirhynchia Pettitt, 1954 Seven species of Orbirhynchia were studied: Orbirhynchia reedensis (Etheridge), (Figure 2C), Upper Turonian, de- scribed in Nekvasilova (1974); O. mantelliana (J. de C. Sowerby), Middle Cenomanian (Coll. Eric Simon, Cran d’E cailles); O. aff. mantelliana, O. aff. boussensis Owen (Figure 2E), O. parkinsoni Owen, O. wiesti (Quenstedt), Cenomanian (Motchurova-Dekova, 1996), and Orbirhynchia sp.1, Bulgaria, Lower Maastrichtian (Coll. NMNHS). The shell is relatively thin - 300-400 um. The primary layer is rarely preserved, 20-40 um thick and usually recrystallized. The secondary layer is built up of fibres that are anisometric shell ultrastructure of Cretaceous rhynchonellide brachiopods 321 TS = Ss SS SSS , ER Figure 1. A. Cyclothyris aff. difformis (Valenciennes in Lamarck), Predboj near Prague, Czech Republic, Cenomanian, sample 18a. Transverse section through the whole shell thickness. p.l. - primary layer below, secondary layer differentiated. B-F. Cyclothyris difformis (Valenciennes in Lamarck) from Dobreva chuka, NE Bulgaria, Cenomanian. B - sample 43a, section through the whole shell thickness; p.l. - primary layer on the left, not silicified, secondary layer partly silicified; arrow on the right-diagenetic calcite underlying the secondary layer. C - sample 42b, rib; primary layer above, recrystallized, but not silicified, secondary layer-partly silicified close to the primary layer. D - sample 42b, strongly silicified secondary layer-below and recrystallized, but non silicified primary layer above. The primary layer is overlain by a thin cover layer, supposed to be the calcitic pseudomorph of the periostracum - arrow. E - sample 43a, partly silicified secondary layer (s.l.) and non silicified primary layer (p.l.), covered by thin calcitic layer, probably a pseudomorph of the periostracum - arrow. F - close up of the area arrowed in E. 322 Neda Motchurova-Dekova Figure 2. A, B. Cyclothyris antidichotoma (Buvignier), Shenley Hill, Leighton Buzzard, Bedfordshire, England, Lower Albian, L. regularis Subzone. A - sample 13a, section through the whole shell thickness, primary layer missing. Internal shell surface in the lower left corner encrusted with diagenetic calcitic prisms. B - sample 13, Section through the whole shell thickness. Primary layer below, recrystallized. C. Orbirhynchia reedensis (Etheridge), Bohemia, Czech Republic, Upper Turonian, sample 21a. Whole shell thickness, primary layer above. D. Burrirhynchia leightonensis (Walker), Leighton Buzzard, Bedfordshire, England, Lower Albian, L. regularis subzone, sample 4a. Secondary fibres. Internal shell surface, vertical, on the left, overgrown by diagenetic calcite crystals (arrow), per- pendicular to the surface. E. Orbirhynchia aff. boussensis Owen, Kaspichan, NE Bulgaria, Cenomanian, sample 37. Secondary layer, rhomboidal or parallelogramic fibres; siliceous pseudomorphs on the organic sheets in the lower half of the picture (arrow). F. Cretirhynchia plicatilis sensu Aliev and Titova, 1988, Lesser Caucasus, Russia, Coniacian-Santonian, sample 34b. Section through a rib, secondary layer. shell ultrastructure of Cretaceous rhynchonellide brachiopods 323 in cross-section, representing well-shaped rhombi or paral- lelograms, with straight sides and well defined angles. Rarely the cross-sections of the fibres are anvil-like. The fibres are very large (W = 35-120 um, T = 10-50 um; C, = 1.1-4, usually 2-3). The stacking of the fibres is uniform. In some species thinner fibres are developed close to the external surface, passing gradually into larger fibres towards the internal part of the shell. Cyclothyris McCoy, 1844 Cyclothyris antidichotoma (Buvignier), (Figure 2A, B), Lower Albian (Owen, 1962); C. aff. difformis, (Figure 1A), Cenomanian (Nekvasilova, 1973), C. difformis (Valencien- nes in Lmk), (Figure 1B-F), Cenomanian (Motchurova- Dekova, 1996), C. zahalkai Nekvasilova, Lower Turonian, (Nekvasilova, 1973) and C. vespertilio (d’Orbighy), France, Santonian (Coll. NHM) were examined. The shell thickness is 300-350 um in C. zahalkai and C. antidichotoma, and reaches 700-1000 um in C. difformis and C. vespertilio. The primary layer is relatively thick in C. aff. difformis and C. difformis, reaching up to 20% (50-80 um) of the total shell thickness. It is interesting to note that both species with thick primary layers inhabited a very shallow transgressive sea floor, namely the sublittoral zone near its boundary with the littoral zone (Nekvasilova, 1973). All species are char- acterized by the predominance of anisometric anvil-shaped (to rarely rhomboidal) fibres in the secondary layer, 15-30 um thick and 2-10 um wide. C,is usually between 4 and 5, but can reach a maximum value of 8. The secondary layer is usually composed of several packages of fibres with differ- ent orientation, so that the distribution of the fibres is not uni- form in any particular cross-section (Figure 1A). In Cyclothyris antidichotoma a band of distinctly more isometric fibres is noted near the interior of the shell (Figure 2B), which looks like fibres close to the anterior margin of muscle scar tissue. Cretirhynchia Pettitt, 1950 The summary given below concerns only some species attributed to Cretirhynchia by different authors. The type species Cretirhynchia plicatilis (J. Sowerby) was not studied due to lack of material. The revision of this genus was still in progress during the preparation of this paper. In the re- cently published first step in the revision (Simon and Owen, 2001), the genus was split in four subgenera and one new genus was proposed. This probably could explain the vari- ability in the shell ultrastructure of the studied species. The thick-shelled species of Cretirhynchia constitute a group that is easily distinguished from the other representa- tives of Cretirhynchia (Motchurova-Dekova, 1993). In the current study these are Cretirhynchia plicatilis sensu Aliev and Titova, 1988 (Figure 2F) from Lesser Caucasus, Coniacian-Santonian (Aliev and Titova, 1988), Cretirhynchia sp. 1, Upper Campanian, and Cretirhynchia sp. 2 (Figure 3A), Lower Maastrichtian from Bulgaria (Coll. NMNHS). They seem to be close to the type species Cretirhynchia plicatilis (J. Sowerby). The three species studied here are characterized by thickening of the umbonal parts with callus, which blurs the outline of the internal morphology. The se- rial sections show strongly convergent dental plates, short ventrally deflected hinge plates, simple subquadrate crural bases, and radulifer crura keeping close together anteriorly. However, their serial sections are more similar to the sec- tions of C. norvicensis Pettitt, published by Owen (1962), than to the sections of Cretirhynchia plicatilis published by Pettitt (1950). The shell of the three studied species (Cretirhynchia plicatilis sensu Aliev and Titova, 1988; Cretirhynchia sp. 1 and Cretirhynchia sp. 2) is very thick: 1000-1800 um. Where preserved, the primary layer was strongly recrystallized, built up of acicular crystals perpen- dicular to the shell surface. The secondary layer is charac- terized by the prevalence of comparatively isometric fibres (Figures 2F, 3A), which have rhombic or rarely anvil-like out- lines (W = 20-40 um; T = 15-25 um; C, having lower values - 1.2 to 2.5, rarely reaching 3.5). In these species the anisometric fibres are usually confined to the outermost part of the shell, reaching higher coefficients C; - up to 8-10 (Figure 3A). According to Simon and Owen (2001), the group of spe- cies with the above mentioned internal details constitute the subgenus Cretirhynchia (Cretirhynchia). SEM investiga- tions on the type species Cretirhynchia plicatilis (J. Sowerby) are also necessary to confirm the above remarks about the shell ultrastructure of the “true” Cretirhynchia. The remaining species attributed to the genus Cretirhynchia display a different fabric of shell ultrastructure. The shell of Cretirhynchia exsculpta Pettitt, Lower Campanian (Pettitt, 1950) is 350-600 um thick. The pri- mary layer is 30-40 um thick and composed of fine acicular calcite crystals, almost perpendicular to the shell surface. The pattern of the secondary layer is different in two sec- tions at a distance of 2 mm. In the section posteriorly to the mid-line, two kinds of fibres are developed (Figure 3B): (1) more isometric (W = 25-50 um; T = 10-20 um; C; = 1.8-3) and (2) more anisometric, (W = 40-65 um; T = 4-15 um; C2 = 3-6). The prevailing part of the fibres is rhombic to parallelogram, but some are anvil-like. The thinner fibres seem to be distributed in thin subparallel bands within the section, but recrystallization blurs the original pattern. The second section situated more anteriorly, shows monoto- nously arranged fibres with no obvious signs of recrystallization, although the bands of thinner (or differently oriented) fibres could also be noticed (Figure 3C). Cretirhynchia aff. cuneiformis, Upper Turonian (Nekvasi- lova, 1974). Most probably this Bohemian species is quite distinct from Cretirhynchia cuneiformis Pettitt (1950), which has just been assigned as the type species of the new genus Woodwardirhynchia by Simon and Owen (2001). The maximum shell thickness in Cretirhynchia aff. cuneiformis is 370 um, the primary layer being 30um thick and built up of acicular crystallites (Figure 3D). The secondary fibres have rhombic to anvil-like outlines. Relatively isomeric fibres are sporadically distributed in bands or lenses (W = 25-38 um; T =7-17 um; C, = 2-3.5). The anisometric fibres prevail (W = 20-50 um; T = 3-14 um; C, = 3.5-6.5). These peculiari- ties are reminiscent of Cyclothyris, but the fibres in Cyclothyris have a maximum of 40 um width. Cretirhynchia minor Petitt, Upper Turonian (Nekvasilova, 1974) was recently removed from the genus Cretirhynchia (Simon and Owen, 2001). The shell of this minute 324 Neda Motchurova-Dekova Figure 3. A. Cretirhynchia sp. 2, Nikopol, Lower Maastrichtian, Bulgaria, sample 45-10. Sulcus - section through the whole shell thickness, external surface below. Primary layer missing. Sublayer of finer anisometric fibres in the outermost part of the shell. B. Cretirhynchia exsculpta Pettitt, Brighton, E. Sussex, England, Lower Campanian, Marsupites Zone, sample 7a. Whole shell thickness. Primary layer below. C. Cretirhynchia exsculpta Pettitt, Brighton, E. Sussex, England, Lower Campanian, Marsupites Zone, sample 7b. Section through the rib. Primary layer above. D. Cretirhynchia aff. cuneiformis Pettitt, Cizkovice near Lovosice, Czech Republic, Upper Turonian, sample 19. Whole shell thickness, primary layer above. E, F. Cretirhynchia minor Pettitt, Cizkovice near Lovosice, Czech Republic, Upper Turonian, sample 22b. E - Section through a rib. F - Boundary between the primary and the secondary layers, anvil- like fibres. shell ultrastructure of Cretaceous rhynchonellide brachiopods 50 um D rl T Se, Figure 4. A. Cretirhynchia bohemica (Schloenbach), Malnice near Louny, Czech Republic, Lower Turonian, sample 20b. Small fragment of non silicified fibres (low relief), strong silicification (high relief). B. Septatoechia inflata Titova, Tuarkir, Turkmenistan, Upper Maastrichtian, sample 26b. Section through a rib, primary layer missing, secondary differentiated. High relief silicified organic sheets subparallel to the shell surface separate the bundles of fibres with different orientation. C. Septatoechia inflata Titova, Novachene, Bulgaria, Upper Maastrichtian, sample 52a. Boundary between the secondary fibres (upper right corner) and a very thick myotest (lower left half) in the ventral valve. D. Septatoechia amudariensis (Katz), Nardyvaldivaly, Badhyz region, East Turkmenistan, Upper Maast- richtian, sample 27a. Secondary fibres crossed by two subparallel bands of high relief silicified organic sheets. E. Septatoechia aff. Rhynchonella baugasii d'Orbigny, Komunari, Bulgaria, Upper Campanian, sample 51b. Orthodoxly stacked fibres in a rib. F. Belbekella mutabilis Lobatscheva, Kuibyshevo, SW Crimea, Russia, Berriassian, sample 32b. Section through the whole shell. Myotest occupying the interior half of the shell thickness separated by a silicified organic sheet (arrow). 326 Neda Motchurova-Dekova rhynchonellide is 450 um thick. The primary layer is microgranular, partly recrystallized (Figure 3F) and 20-25 um thick. Close to the exterior, at about one third of the shell thickness, finer anisometric fibres are developed; W=30-45 um; T = 6-10 um; C2 = 3.5-6.5. The remaining part of the shell is built up of uniformly arranged more iso- metric fibres, (W = 25-40 um; T = 10-17 um; C, = 2.2-3.5); (Figure 3E). Cretirhynchia bohemica (Schloenbach), Lower Turonian (Nekvasilova, 1974) was strongly silicified and only some isolated fragments of the original structure were preserved. The shell is relatively thick - 480 um and the primary layer is recrystallized, 30-40 um thick. Judging from the narrow spots of non-altered secondary shell (Figure 4A), the fibres are anisometric, very fine and anvil-like (W = 16-40 um; T = 4-8 um; C = 3.2-7). These are amongst the most anisometric fibres of all the studied species, referable to Cretirhynchia, and are very similar to the fibres in Cyclothyris. As Nekvasilova (1974) suggested, the generic assignment of this species is uncertain and new data are necessary to elucidate in detail its affinities. Septatoechia Lobatscheva and Titova, 1977 The type species Septatoechia inflata Titova was investi- gated using representatives from the type locality in Turkmenistan, Lower Maastrichtian (Figure 4B) (Lobatscheva and Titova, 1977) and from Bulgaria, Upper Maastrichtian (Figure 4C) (Motchurova-Dekova, 1996). In addition, two other species were studied: Septatoechia amudariensis (Katz) from the Upper Maastrichtian in Turkmenistan (Figure 4D) (Lobatscheva and Titova, 1977) and from Bulgaria, and Septatoechia aff. Rhynchonella baugasii d’Orbigny, Upper Campanian from Bulgaria (Figure 4E) (Motchurova-Dekova, 1996). This genus is character- ized internally by a very high median septum and subparallel to convergent dental plates. The shell is very thick, reach- ing 1000-2000 um. The primary layer is relatively thin: 30-50 um. The secondary layer is composed of many packages of differently orientated relatively isometric fibres. They are 15-40 um wide and 8-30 um thick. C, starts from very low values (C; = 0.8-3). Externally and internally thin- ner anisometric fibres are developed. Centrally, the shell is built up of relatively isometric thicker fibres. The main part of the fibres is rhombic, or less commonly anvil-like, espe- cially the thinner fibres. Before erecting the genus Septatoechia (Lobatscheva and Titova, 1977), its represen- tatives were assigned to the genera Cyclothyris or Cretirhynchia because of internal and external similarities. In fact Septatoechia represents an interesting mixture of morphologic characteristics, typical of Cyclothyris and Crtirhynchia. Judging from ultrastructural evidence, Septatoechia is much closer to Cretirhynchia sensu stricto, displaying a very thick shell, and relatively isometric and similarly sized rhombic fibres in the secondary shell. As in Cretirhynchia, the rhombic cross-sections of the fibres in Septatoechia have rounded edges. In both genera the myotest is typically very thick (Figure 4C). The fibres in Septatoechia, however, are more isometric and the secon- dary layer seems to be differentiated (Figure 4B). Single representatives of five other Cretaceous rhynchonellide genera were studied for comparison. Belbekella Moisseev, 1939 The shell thickness in the type species Belbekella airgulensis Moisseev, Berriassian (Lobatscheva, 1993) is 600 um. The primary layer, built up of acicular calcite, is 40-100 um thick. The fibres are uniformly arranged and anvil-like (W = 15-40 um; T = 2-6 um; C: = 4-7). A more posterior cross-section, cutting the muscle field of the pedicle valve of Belbekella mutabilis Lobatscheva, Berriassian (Lobatscheva, 1993) was studied. A very thick myotest (up to 300 um) was observed (Figure 4F). Lamellaerhynchia Burri, 1953 Lamellaerhynchia geokderensis Moisseev, Upper Barremian, Turkmenistan (Coll. Lobatscheva) shows shell thickness of 700-1000 um. The primary layer is micro- granular and 20-25 um thick. The secondary layer is built up of fibres, more anisometric and finer ones close to the ex- terior shell surface (W = 10-20 um; T = 3-5 um; Cz = 3-5) and more isometric and larger ones toward the interior mar- gin of the shell (W = 25-30 um; T = 8-15 um; Ci = 2-3). The majority of the fibres have anvil-like cross-sections, but some of the larger and thicker fibres tend to have rhombic sections (Figure 5A). Burrirhynchia Owen, 1962 The type species Burrirhynchia leightonensis Walker, Lower Albian (Owen, 1956) has a shell thickness of 500-600 um. The primary layer is 20 to 50 um thick. The secondary layer is composed of uniformly arranged anisometric anvil- like fibers (Figure 5D); W = 20-50 um; T = 5-10 pm; C: = 3.5-6, with average values of C; around 5. Thinner fibres are developed close to the outer surface (Figure 5D), but there is no noticeable differentiation of the secondary layer (Figures 2D, 5C). Almerarhynchia Calzada, 1974 Almerarhynchia pocoviana Calzada and Pocovi (1980), Upper Campanian has a relatively thin shell - 290 um. The primary layer is 20 um thick and strongly recrystallized. The secondary layer is built up of monotonously stacked rhombic and parallelogram, to rarely anvil-like fibres, with predomi- nance of anisometric rhombic fibres. Although the majority of fibres (W = 25-35 um; T = 4-10 um; C; = 3-7) are anvil- like in cross sections (Figure 5E), they are not convex as in other species but tend to be rhombic. Close to the primary layer finer fibres are developed (W = 15-20 um; T = 3-6 um; C2 = 3-6). Similar finer fibres, but not well differen- tiated, are developed close to the internal part of the shell. The finer fibres do not constitute a distinct sublayer. The overall appearance of the cross section of the secondary layer is uniform. Grasirhynchia Owen, 1968 The shell thickness of the type species Grasirhynchia grasiana (d’Orbigny), Cenomanian, (Owen, 1968) is 300 um. The primary layer is 15-20 um thick. The shape of the fi- bers in the secondary layer is blurred by the strong silicification of the interfibre spaces, vacated after the early shell ultrastructure of Cretaceous rhynchonellide brachiopods 327 Table 1. Comparative ultrastructiral characteristics of four Cretaceous rhynchonellide brachiopod genera. Fibre dimensions Peculiarities of the shell ultrastructure Genus W (um) T(um) C=WT Orbirhynchia 35-120 10-50 1-4 rhombic or parallelogramic, relatively more isometric fibres, uniformly arranged. Cyclothyris 15-30 2-10 4-8 anvil-like anisometric fibres; often differen- tiated secondary layer. Cretirhynchia 20-40 15-25 1.2-2.5 thick shell, rhombic, rarely anvil-like, rela- (C. plicatilis sensu Aliev and Titova, 1988) tively isometric fibres. Septatoechia 15-40 8-30 0.8-3 very thick shell; rhombic, rarely anvil-like, diagenetic decay of the organic sheaths (Figure 5F). The silicification is stronger in the umbonal part of the shell. In this case it is probable that the shape and dimensions of the fibres were altered by the diagenesis. The secondary layer is built up of two kinds of uniformly distributed fibres: (1) finer close to the exterior (W = 15-25 um; T = 2-5 um; C2 = 4.5-9) and (2) larger in the central and internal part of the shell (W = 35-55 um; T = 8-12 um; C, = 3-4.5). The tran- sition from the finer to the larger fibres is continuous. The majority of the fibres are rhomboidal. Some of them, espe- cially close to the primary layer, show anvil-like sections. Conclusions This study generally confirms the validity of the classifica- tion of Kamyshan (1977) who distinguished two types of fi- brous structures of the secondary layer among Mesozoic rhynchonellides: coarse-fibrous basiliolidine type and fine fibrous rhynchonellidine type. The studied Cretaceous genera have been accommodated in this scheme, although large variation in fibre size is noticed. Data about fibre shape and size of genera, for which suffi- cient material was available, are given in Table 1. Along with the previously studied genera Erymnaria and Costerymnaria (Motchurova-Dekova and Taddei Ruggiero, 2000), the genus Orbirhynchia is characterized by a coarse fibrous basiliolidine type microstructure of the secondary layer. Orbirhynchia has large fibres with well-defined rhom- bic cross-sections. It seems that during the Cretaceous the representatives of the pugnacoid stock (Mancenido and Owen, 1996, 2000) developed a coarse fibrous secondary layer. All the remaining genera can be accommodated within the group of species with a fine fibrous rhynchonellidine type of ultrastructure, although they display a larger fibre size than those reported for the Jurassic and Lower Cretaceous representatives (Smirnova, 1984). When compared to the Upper Cretaceous Orbirhynchia, however, all the other stud- ied genera are characterized by a smaller fibre size (Table 1). Cyclothyris is characterized by a typical rhynchonellidine type ultrastructure sensu Kamyshan (1977). Cretirhynchia and Septatoechia are also classified within the rhynchonellidine group. Both genera, however, have relatively isometric fibres; often differenti- ated secondary layer. somewhat larger fibres than Cyclothyris, and with a peculiar relatively isometric shape in cross-section. It is suggested that Cretirhynchia and Septatoechia are more closely related to each other than to any of the other studied genera. Additional investigations on other representatives of Cretirhynchia are necessary to confirm this relationship. Belbekella, Lamellaerhynchia, Almerarhynchia, Burrirhynchia and Grasirhynchia have anisometric fibres, similar to those of Cyclothyris. Their larger fibre size and undifferentiated secondary layers distinguish them from Cyclothyris. Burrirynchia has uniformly arranged anisometric fibres quite distinct from the pattern of Cretirhynchia plicatilis sensu Aliev and Titova, 1988. Burrirynchia seems closer to Cyclothyris judging by similarities in the fibre shape. The fibre size in Burrirynchia shells, however, is larger. Before drawing conclusion about the relationship between Burrirynchia and Cretirhynchia suggested by Owen (1962), the shell ultrastructure of the type species Cretirhynchia plicatilis should also be studied. In summary it appears that the genera belonging to the Cretaceous representatives of the hemithiridoid and rhynchonelloid stocks (Mancenido and Owen, 1996, 2000) display a fine fibrous rhynchonellidine type microstucture of the secondary layer. Finally it should be pointed out that the benefits of using shell microstructural data for the purposes of distinguishing taxa should not be overestimated. Sometimes the dimen- sions of the fibres and the texture of the secondary layer were found to vary widely from one section to another, even in one specimen. A complete pattern of the shell ultrastructure can be obtained only if a set of sections, both transverse and longitudinal, is made and examined and if sufficient numbers of species from each genus are studied. Acknowledgments This study was carried out during a long-term scholarship granted by the Japan Society for the Promotion of Science at the Paleobiological Laboratory, Tokyo University. | ex- press my sincere thanks to the head of the Laboratory K. Tanabe, to K. Endo and M. Saito for their invitation to per- form the work in this laboratory and for their continuous help during my stay in Tokyo. Thanks are due to S. Long and E. 328 Neda Motchurova-Dekova Figure 5. A, B. Lamellaerhynchia geokderensis (Moisseev in Weber) from Keldje, Tuarkyr, Turkmenistan, Upper Barremian. A - sample 30a, rib, internal shell surface on the top. Secondary shell, subparallel silicified organic sheets crossing the shell (arrow). B - sample 30b, rib. Primary layer (p.l.) partly preserved. A pseudo-tertiary (diagenetic) layer (pseudo t.l.) of calcite prisms is devel- oped in the interior of the secondary layer (s.l.). The dashed white line indicates the internal surface of the shell overgrown by diagenetic calcite prisms in the upper left corner. C, D. Burrirhynchia leightonensis (Walker), Leighton Buzzard, Bedfordshire, England, Lower Albian, L. regularis subzone, C - sample 4b. The whole shell thickness, primary layer (p.l.) above. D - close up of the area arrowed inC. E. Almerarhynchia pocoviana Calzada and Pocovi, Sierra de Mont-Roig, Spain, Upper Campanian, sample 25a. The whole shell thickness, primary layer above, recrystallized. Silicified organic sheets crossing the section (arrow). F. Grasirhynchia grasiana (d’Orbigny) from Warminster, Wiltshire, England, Lower Chalk, Cenomanian, sample 9b. Section through a rib, strongly silicified and recrystallized secondary shell; partly preserved primary layer (p.l.) above. shell ultrastructure of Cretaceous rhynchonellide brachiopods 329 Owen (London), S. Lobatscheva and M. Titova (St. Petersburg), O. Nekvasilova and J. Zitt (Prague), E. Simon (Brussels) and S. Calzada (Barcelona) for supplying material for study. I thank the Organizing Committee for a grant-in- aid to attend the Millennium Brachiopod Congress, London 2000 in order to present this paper. | am grateful to the referees D. Mackinnon (Christchurch) and Al. Popov (Vladivostok) for the constructive and helpful comments. Special thanks go to K. Moriya, T. Sasaki, |. Sarashina (Tokyo) and V. Dekov (Sofia) for their continuous technical help. This is a contribution to the project “Revision of the genus Cretirhynchia”, partly supported from the Bulgarian National Science Found - grant no. MU-F-08/96. References Aliev, O. V. and Titova, M. V., 1988: Brachiopoda, Upper Cretaceous. In, Ali-zade, Ak. A. et al. eds., The Cretaceous Fauna of Azerbaijan, p. 220-240. Elm, Baku. (in Russian) Ali-zade, Ak. A., Aliev, S. A. and Gamzatov, G. A., 1981: Shell ultrastructure of the Late Cretaceous rhynchonellides from the Lesser Caucasus. Voprosy paleobiogeokhimii, no. 1, p. 50-54. (in Russian) Baker, P. G., 1971: A new micromorphic rhynchonellid brachiopod from Middle Jurassic of England. Palaeontology, vol. 14, no. 3, p. 696-703. Calzada, S. and Pocovi, A., 1980: Braquiopodos senonienses de la sierra del Mont-Roig (Prepirineo de Lerida). Boletin Real Sociedad Espanola de Historia natural, section Geologica, no. 78, p. 5-19. Dagys, A. S., 1974: Triassic Barachiopods (Morphology, systematics, phylogeny, stratigraphic significance and biogeography). 388 p. Nauka, Siberian section, Novosi- birsk. Gaspard, D., 1982: Microstructure de terebratules biplisees (Brachiopodes) du Cénomanien de la Sarthe (France). Affinités d'une des formes avec le genre Sellithyris Midd. Annales de Paléontologie (Vertebre-Invertebres), vol. 68, no.1, p. 1-14. Gaspard, D., 1990a: Microstructural organization of the exo- skeleton of some articulate brachiopods (Terebratulida, Rhynchonellida)-The importance of the calcitic granules and the effects of diagenesis. /n, Suga, S. and Naka- hara, H., eds., Mechanisms and Phylogeny of Minerali- zation in Biological Systems. p. 403-407. Springer Verlag, Tokyo. Gaspard, D., 1990b: Growth stages in articulate brachiopod shells and their relation to biomineralization. /n, MacKin- non, D. |.; Lee, D. E.; Campbell, J. D. eds., Brachiopods Through Time. p. 167-174. Balkema, Rotterdam. Gaspard, D., 1996: Taphonomy of some Cretaceous and Recent brachiopods. In, Copper, P. and Jin, J. eds., Brachiopods, Proceedings of the Third International Brachiopod Congress, Sudbury, Canada 1995, p. 95- 102, Balkema, Rotterdam. Kamyshan, V. P., 1977: Organizational levels of the shell sub- stance, structure and texture of the shell of Mesozoic and Cenozoic rhynchonellides. Abstracts of the Third all- union conference on Mesozoic and Cenozoic brachio- pods. 15-18 Nov., Kharkov, Russia, p. 21-24. (in Russian) Kamyshan, V. P., 1986: On the microstructure features of the shell growth in Jurassic rhynchonellides (Brachiopoda). Vestnik Kharkovskogo Universiteta, seria Geologiches- kaia, vol. 16, no. 283, p. 75-77. (in Russian) Kamyshan, V. P. and Adel, A. A., 1979: New data on the shell microstructure and morphology of Jurassic Praecy- clothyroidea (Brachiopoda). Vestnik Khar'kovskogo Universiteta, seria Geologicheskaia, vol. 10, no. 184, p. 20-26. (in Russian) Lobatscheva, S. V., 1993: The genus Belbekella Moisseev, 1939, (Brachiopoda), its content and evolution. In, Bogdanova, T. N., and Khozatskiy, L. |, eds. Phylogenetic Aspects of Paleontology, p. 83-97. Nauka, St. Petersburg. (in Russian) Lobatscheva, S. V. and Titova, M. V., 1977: About a new genus of rhynchonelloid brachiopod from the Cretaceous of Turkmenia. Annual of the All-union Paleontological Society, no 19, p. 102-113. (in Russian) MacKinnon, D., 1974: The Shell Structure of Spiriferide Brachiopoda. Bulletin of the British Museum (Natural History), Geology, vol. 25, no. 3, p. 189-261. Mancenido, M. O. and Owen, E. F., 1996: Post-Paleozoic rhynchonellides: an overview. In, Copper P. and Jin, J. eds., Brachiopods, Proceedings of the Third International Brachiopod Congress, Sudbury, Canada 1995, p. 368. Balkema, Rotterdam. Mancenido, M. ©. and Owen, E. F., 2000: Post-Paleozoic Rhynchonellida (Brachiopoda): classification and evolu- tionary background. In, Brunton, H. ed., The Millennium Brachiopod Congress, London, Abstracts, p. 58. The Natural History Museum, London. Michalik, J., 1993: Growth and structure of some Rhaetian rhynchonellid shells (Brachiopoda) from the Central Western Carpathians. In, Pälfy, J and Vörös, A. eds., Mesozoic Brachiopods of Alpine Europe, p. 101-108. Hungarian Geological Society, Budapest. Motchurova-Dekova, N., 1992: Peculiarities of the shell micro- structure of Late Cretaceous rhynchonellides (Brachiopoda) and their early diagenetic alterations. An- nual of the University of Mining and Geology, Sofia, vol. 38, no 1, p. 19-33. (In Bulgarian with English abstract) Motchurova-Dekova, N., 1993: Brachiopods of the order Rhynchonellida from the North European type Upper Cretaceous in Bulgaria-taxonomy and stratigraphic signifi- cance. Unpublished PhD thesis, 225 p. University of Mining and Geology, Sofia. (in Bulgarian) Motchurova-Dekova, N., 1994: Emended diagnoses of four Cretaceous rhynchonellid genera. Geologica Balcanica, no 24, p. 87-89. Motchurova-Dekova, N., 1996: Late Cretaceous rhynchonellid assemblages of North Bulgaria. /n, Copper, P. and Jin, J. eds., Brachiopods, Proceedings of the Third International Brachiopod Congress, Sudbury, Canada 1995, p. 185-189, Balkema, Rotterdam. Motchurova-Dekova, N. and Taddei-Ruggiero, E., 2000: First occurrence of the Brachiopod family Erymnariidae Cooper in the Upper Cretaceous of southern Italy. Palaeontology, vol. 43, no. 1, p. 173-197. Nekvasilova, O., 1973: The brachiopod genus Bohemirhynchia gen. n. and Cyclothyris McCoy (Rhynchonellidae) from the Upper Cretaceous of Bohemia. Sbornik geologickych ved, Paleontologie, no. 330 15, p. 75-117. Nekvasilova, O., 1974: Genus Cretirhynchia and Orbirhynchia (Brachiopoda) from the Upper Cretaceous of North-West Bohemia. Sbornik geologickych ved, Paleontologie, no. 16, p. 35-67. Owen, E. F., 1956: The Lower Cretaceous brachiopods “Rhynchonella” gibbsiana (J. de C. Sowerby) and Sulcirhynchia hythensis sp. nov. The Annals and Magazine of Natural History, vol. 12, no. 9, p. 164-172. Owen, E. F., 1962: The brachiopod genus Cyclothyris. Bulletin of the British Museum (Natural History), Geology, vol. 7, no. 2, p. 39-63. Owen, E. F., 1968: A further study of some Cretaceous rhynchonelloid brachiopods. Bulletin of the Indian Geol ogists’ Association, vol. 1, p. 17-32. Pettitt, N. E., 1950: A monograph on the Rhynchonellidae of the British chalk, Part |. Palaeontographical Society, no. 103, p. 1-26. Neda Motchurova-Dekova Sass, D. B. and Monroe, E. A., 1967: Shell growth in recent Terebratuloid Brachiopoda. Palaeontology, vol. 10, no. 2, p. 298-306. Simon, E. and Owen, E. F., 2001. A first step in the revision of the genus Cretirhynchia Pettitt, 1950. Bulletin de I’In- stitut Royal des Sciences Naturelles de Belgique, vol. 71, p. 53-118. Smirnova, T. N., 1984: Lower Cretaceous Brachiopods, p. 200, Nauka, Moscow. (in Russian) Taddei Ruggiero, E. and Ungaro, T., 1983: Sardorhynchia crassa gen. nov., sp.nov. (Brachiopoda), from the Jurassic of Sardinia. Boletino della Societa Paleon- tologica Italiana, vol. 22, no. 3, p. 225-246. Williams, A. 1968a: A history of skeletal secretion among ar- ticulate brachiopods. 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However, figures will be returned upon request by the authors after the paper has been pub- lished. Ager, D. V., 1963: Principles of Paleoecology, 371p. McGraw- Hill Co., New York. Barron, J. A., 1983: Latest Oligocene through early Middle Miocene diatom biostratigraphy of the eastern tropical Pacific. Marine Micropaleontology, vol. 7, p. 487-515. Barron, J. A., 1989: Lower Miocene to Quaternary diatom biostratigraphy of Leg 57, off northeastern Japan, Deep Sea Drilling Project. /n, Scientific Party, Initial Reports of the Deep Sea Drilling Project, vols. 56 and 57, p. 641-685. U. S. Govt. Printing Office, Washington, D. C. Burckle, L. H., 1978: Marine diatoms. In, Hag, B. U. and Boersma, A. eds., Introduction to Marine Micropaleon- tology, p. 245-266. Elsevier, New York. Fenner, J. and Mikkelsen, N., 1990: Eocene-Oligocene diatoms in the westem Indian Ocean: Taxonomy, stratigraphy, and paleoecology. /n, Duncan, R. A., Backman, J., Peterson, L. C., et al, eds.Proceedings of the Ocean Drilling Program, Scientific Results, vol. 115, p. 433-463. College Station, TX (Ocean Drilling Program). Kuramoto, S., 1996: Geophysical investigation for methane hy- drates and the significance of BSR. Journal of the Geological Society of Japan, vol. 11, p. 951-958. (in Japanese with English abstract) Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey (A new find of an ammonoid jaw ap- paratus). Paleontologicheskii Zhurnal 1974, p. 127-129. (in Russian) POPOL ELE LE LE LTD DT DE DT DE DE DE DT DE DE DE DT DE DE DE DE DE DE DE DE DE DE DE DE DE DL DE DL DL DT DE ST BE SE DEE TEFE OB 151) PSit, 2002471 A268 (+), 14278 (A) OHELSRY LEN SA FEFS CHEN &3. 1 A27H (HB) FRIABSRELT [21H APORR -TEME- 74 — 0 FRED 5Ofs—: HbA, À B+ RET: PRISER AFTER RA FF ER (BI ZEHN LET. 7 1 H26H (+) ls, FELSEROFRERHE OH BERSHETELTBOKES. MR DALASHHINE2001E1I1AÄSOHR (4) T3. ©2002 FS - RaUsEFAVYREBNE GRH) TEL ES. RRARIA6 AD~ Fach HMSBHCT. LH HÉROS U]II2002€ 5 A 7 H (AK) CF. OHEMFLZTUE, IMAÉTEMÈRN 27-97 Ya yF7PyY a - NI-ZAERLTBHEF. Hi FSP DEEE CENTRES. PEHLSESOHETERO E TCHAUBE FEU. BASE + VV FU OÙ LRORLUBZHEÉ FASO LASS TÉRRE hack CHREAYD FSW. E-mail P77 7ATOMLASSZEM, RANE LTRUAU TEV EHA. EKMPERICMT SEH DES THROTSHHE CHA CES, 7305-8571 >< idm KEG 1-1-1 ARATE HEMFSTER) za PGBS Tel: 0298-53-4302 (E18) Fax: 0298-51-9764 E-mail: ogasawar @ arsia.geo.tsukuba.ac.jp TRS Al 9 7305-8571 >< ISTH KES 1-1-1 TRASH EA Tel: 0298-53-4212 (2) (or 53-4465 (ER=Z)) Fax: 0298-51-9764 E-mail: isaomoto @ sakura.cc.tsukuba.ac.jp PPP BPE PLD LDP ODED LPL DEDEDE DED ODL DEDEDE DL DL DED EDL DOD LD EDL OLED LOLOL DLO LOLOL SL OL SL OST OS ABORTICBZTAZHA, SGBEOSBUAK, HER FH AH ER SULENZAMS5Oo2H BATSNCWEST, HEOEHZAUTELDOEN CT, AVYVEFAYTHMRACH Bald - Hee IEAN AAS Behe SWHARRMBRACH THA HRA 22H BRERA LC BAO MEE $a-J7LN-7RRBBREME (7 1 % x À IK) OXRERFTAR HAS (HAKKAR) Ick, ; ENDE A A G # WM + À 20014 12H27H A) hil 7113-8622 HAM ABHIAS-16-9 2001 #12 A 31H FE 47T BREFL2ZEEKR + >» 4 — Æ adh ah by te a el ey ty (ial fey fst - k - MEERE teh e BRE: RK ee KB Al fl EA Samengetet EA MH 2,500F9 7176-0012 Bra EKSEIL201301 5 03-3991-375 4 ISSN 1342-8144 Paleontological Research BSE, #45 s iii | | Paleontological Research Vol. 5, No. 4 December 31, 2001 CONTENTS Tatsuro Matsumoto and Takemi Takahashi: A study of Hypoturrilites (Ammonoidea) from | 29 | | Hokkaido (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XCl) -------------- Tatsuhiko Yamaguchi and Hiroki Hayashi: Late Miocene ostracodes from the Kubota Formation, Higashi-Tanagura Group, Northeast Japan, and their implications for bottom environments :::::--- Hiroaki Karasawa and Hisayoshi Kato: The systematic status of the genus Miosesarma Karasawa, 1989 with a phylogenetic analysis within the family Grapsidae and a review of fossil records (Crustacea: Decapoda: Brachyura) eee ee eee mie 0508000,050.09.000000000000004800000000000000000000009 Kazuyoshi Moriya, Hiroshi Nishi and Kazushige Tanabe: Age calibration of megafossil biochronology based on Early Campanian planktonic foraminifera from Hokkaido, Japan ::::::::-- Jun-ichi Tazawa: Middle Permian brachiopods from the Moribu area, Hida Gaien Belt, central Japan - - -- Kazushige Tanabe, Royal H. Mapes and David L. Kidder: A phosphatized cephalopod mouthpart from the Upper Pennsylvanian of Oklahoma, US Ar 2s ae ro ae Neda Motchurova-Dekova: Taxonomic and phylogenetic aspects of the shell ultrastructure of nine Cretaceous rhynchonellide brachiopod genera ms ss © «| oe ee ee eee (0 fe) 0} eee eee eo ol fel sie) ee net ce ce)... | ITUTION LIBRARIES | ili | ‘uleontological ~~ Research = Vol. 6 No. 1 April 2002 Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Alan G. Beu (Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato (Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto University, Kyoto, Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain), Roger D. K. Thomas (Franklin and Marshall College, Lancaster, USA), Katsumi Ueno (Fukuoka University, Fukuoka, Japan), Wang Hongzhen (China Dies of Geosciences, Beijing, China), Yang Seong Young (Kyungpook National University, Taegu, Korea) Officers for 2001-2002 President: Hiromichi Hirano Councillors: Shuko Adachi, Kazutaka Amano, Yoshio Ando, Masatoshi Goto, Hiromichi Hirano, Yasuo Kondo, Noriyuki Ikeya, Tomoki Kase, Hiroshi Kitazato, Itaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Kei Mori, Hirotsugu Nishi, Hiroshi Noda, Kenshiro Ogasawara, Tatsuo Oji, Hisatake Okada, Tomowo Ozawa, Takeshi Setoguchi, Kazushige Tanabe, Yukimitsu Tomida, Kazuhiko Uemura, Akira Yao Members of Standing Committee: Makoto Manabe (General Affairs), Tatsuo Oji (Liaison Officer), Shuko Adachi (Finance), Kazushige Tanabe (Editor in Chief, PR), Tomoki Kase (Co-Editor, PR), Kenshiro Ogasawara (Planning), Yoshio Ando (Membership), Hiroshi Kitazato (Foreign Affairs), Haruyoshi Maeda (Publicity Officer), Ryuichi Majima (Editor, “Fossils” ), Yukimitsu Tomida (Editor in Chief, Special Papers), Tamiko Ohana (Representative, Friends of Fossils). 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Phone: (978)750- 8400, Fax: (978)750-4744, www.copyright.com Cover: Typical Pleistocene fossils from the Japanese Islands. Front cover: Sinomegaceros yabei (Shikama). Back cover: Paliurus nipponicum Miki, Mizuhopecten tokyoensis (Tokunaga), Neodenticula seminae (Simonsen and Kanaya) Akiba and Yanagisawa and Emiliania huxleyi (Lohmann) Hay and Mohler. All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16-9, Bunkyo-ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp/palaeont/ Paleontological Research, vol. 6, no. 1, pp. 1-22, April 30, 2002 © by the Palaeontological Society of Japan Middle Miocene ostracods from the Fujina Formation, Shimane Prefecture, Southwest Japan and their paleoenvironmental significance GENGO TANAKA’, KOJI SETO’, TAKAO MUKUDA’ AND YUSUKE NAKANO' ‘Graduate School of Science and Engineering, Shizuoka University, Shizuoka, 422-8529, Japan "Department of Geoscience, Shimane University, Matsue, 690-8504, Japan (e-mail: seto@riko.shimane-u.ac.jp) "Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, 739-8521, Japan (e-mail: takaom@hiroshima-u.ac.jp) “Okehazama 4-59-226, Arimatsu-cho, Midoriku, Nagoya, 458-0911, Japan (e-mail: y-nakano@chikyumaru.co.jp) Received 16 August 2001; Revised manuscript accepted 8 November 2001 Abstract. Thirty-five ostracod species belonging to 18 genera are recognized from the Middle Miocene Fujina Formation (ca. 14-12 Ma), 3 km southwest of Matsue City, Shimane Prefecture, Japan. Most of these species are part of the recent Japan Sea proper water fauna; they are also classified into 4 categories, circum- polar, cryophilic, endemic cool-temperate and temperate species. the Fujina Formation was deposited under a cold-water environment. These ostracod assemblages indicate that Ten new species, Ambtonia shimanensis, A. takayasui, Acanthocythereis fujinaensis, A. izumoensis, Cluthia tamayuensis, C. subjaponica, Kotoracythere tsukagoshii, Laperousecythere ikeyai, Palmoconcha irizukii, and Robertsonites yatsukanus are de- scribed. Key words: Fujina Formation, Japan Sea proper water, Middle Miocene, ostracods, paleoenvironment Introduction The Japan Sea developed as a result of back-arc spread- ing prior to 16 Ma and then further expanded by clockwise rotation of the southwestern part of the Japanese islands be- ginning 15 Ma (Otofuji and Matsuda, 1984). During this short period (ca. 16.5-15 Ma), a tropical to subtropical molluscan fauna, called the Kadonosawa Fauna, spread widely around the Japanese islands. At about 15 Ma, this Kadonosawa fauna was replaced by a cool to temperate molluscan fauna, the Shiobara-Yama type fauna in the Japan Sea region (Chinzei, 1986). According to Chinzei (1986), this drastic faunal change in molluscs was caused by the closure of the Tsushima Straits in the western por- tion of the Japan Sea. Based on studies of molluscan as- semblages in the Middle Miocene of the San’in district along the Japan Sea, the shallow embayment facies (the Shiobara Fauna) appeared after the Omori period (ca. 14.5-15 Ma). During the Fujina period (ca. 14-12 Ma), the molluscan assemblages were accompanied by an off- shore facies (the Yama Fauna) and an increase in colder species of the Shiobara Fauna (Takayasu er al., 1992). Thus, it is thought that the Fujina Formation was deposited under a cold-water environment which resulted from the closure of the Tsushima Straits. However, the presence of warm-water cephalopod species (Aturia sp. and Argonauta tokunagai) in several horizons may suggest the influence of a warm-water current (Sakumoto et al., 1996). Because benthic ostracods do not have a pelagic life stage, they can be easily isolated by environmental barriers. Although Miocene ostracod assemblages in Japan have been reported from several localities (Ishizaki, 1963, 1966; Yajima, 1988, 1992; Irızuki, 1994; Irizuki and Matsubara, 1994, 1995; Ishizaki er al., 1996; Irizuki er al., 1998), the one report from the marine sediments in the southwest of Japan only covered the early Middle Miocene Bihoku Group (Yajıma, 1988). To describe the ostracod assem- blages in the Fujina Formation, therefore, it is very impor- tant to consider marine paleoenvironments of the Japan Sea coast and to examine their paleoenvironmental signifi- cance. 130° 00'E 136° 00'E Japan Sea Upper Member = Fujina F 7 N Lower Member Conglomerate A and sandstone [I] Omori F. NES Andesite lava Figure 1. Map of the study area. Geological setting of Fujina Formation The Fujina Formation was named by Tomita and Sakai (1937), then redefined by Ogasawara and Nomura (1980) and Takayasu and Nakamura (1984). This formation cov- ers over 50 km, striking approximately EW to NE-SW and dipping about 10°N along the southern part of the Shinji Lowland (Figure 1). It is about 500 m in maximum thick- ness and conformably overlies the Omori Formation, which is composed of andesite lava in the lower part and shallow marine andesitic conglomerate and sandstone in the upper part (Kano er al., 1994). The Fujina Formation near the type locality (this study area) is divided into the Lower and Upper Members by lithology. The Lower Member is com- posed of alternating layers of massive, gray, very fine- grained sandstone (0.5-5 m in thickness) containing cal- careous nodules, and massive, dark gray siltstone (0.5-1 m in thickness). The sediments of the uppermost part of this member are made of a medium-grained sandstone (0.5 m in thickness) containing pebbles. The Upper Member is mainly composed of a massive, dark gray siltstone which is intercalated with felsic tuff layers (2 m in thickness), cal- careous nodule beds, and “Modiolus” beds (0.3 m in thick- ness) in the uppermost part. Many marine molluscs, vertebrates (e.g., Desmostylus japonicus and Carcharodon megalodon) and decapods occur in all of the Fujina Formation (Kano et al., 1994). Based on the planktonic Gengo Tanaka et al. pa 3 B2 1 Location B Location A Upper Member Fujina Formation 10m Ea siltstone very fine sandstone coarse sandstone EE with pebbles felsic tuff ææ "Modiolus" bed © =} = © = = © = ° ey i calcareous nodules Omori Formation fo) VA Teredo sp. . n no.ostracod horizon —A, B ostracod horizon Figure 2. Columnar sections of the Fujina Formation. foraminifers, the Upper Member of the Fujina Formation is assigned to N.10-11 of Blow’s zones (14.6/14.8-12.4 Ma) (Nomura and Maiya, 1984). Materials and methods Fossiliferous sediment samples used in this study were collected from the upper part of the Lower Member to the Upper Member of the Fujina Formation at two locations (Figure 2). Each of the dried sediment samples (80 g) of a total of 46 collected were disaggregated, making use of naphtha for rock maceration (Maiya and Inoue, 1973), washing through a 235 mesh (63 4 m) sieve, and drying again. This procedure was repeated until the whole sedi- ment sample was disintegrated. A fraction coarser than 120 mesh (125 um) sieve was sieved and all the ostracod specimens present were picked. Miocene ostracods from Fujina Formation Pye A1 A2 A3 A4 AS A6 A7 AB A9410 AIT A12 A13 A14 AIS AIG A17 AIBAIY A20 A21 A22A23424A25 Bi B2 B3 BA Acanthocythereis dunelmensis (Norman, 1865) Acanthocythereis fujinsensis sp. nov. Acanthocythereis izumoensis sp. nov. Acanthocythereis koreana Huh and Whatley, 1997 Acanthocythereis tsurugasakensis Tabuki, 1986 Loxoconcha subkotoraforma Ishizaki, 1966 Loxoconchidea sp. Munseyella hatatatensis Ishizaki, 1966 Paijenborchella cf. tsurugasakensis Tabuki, 1986 Palmenella limicola (Norman, 1865) Palmoconcha irizukii sp. nov. Robertsonites japonicus (Ishizaki, 1966) Robertsonites reticuliformus (Ishizaki, 1966) Robertsonites cf. tuberculatus (Sars, 1866) 1 ROMANS IGN 22 I EON 785 3 Uae pe ERS IE TREE EI EI SIERT SE Z ZU S 27 2AB HT SET ZIHTAGENS SET AT EZ TE ET EI 1522830 CARS ARE ee A OTe TEE Gres ano. 2B all Se OSL AIO) 212s Ps I Te Te N 7 960 880 1440 1680 80 800 1120 320 320 1040 1680 1440 1440 1120 1040 1040 80 80 240 60 80 2240 1440 1680 1760 Figure 3. List of ostracod species from the Fujina Formation (— —: circumpolar species; —: cryophilic species; +: endemic cool-temperate spe- cies; ++: temperate species). Characteristic ostracods from Fujina Formation Thirty-five species in 18 genera of ostracods were identi- fied from 29 samples (25 samples from Location A and 4 samples from Location B); (Figure 3). Ostracods from the Fujina Formation can be divided into four different tem- perature-related categories: 1) circumpolar, 2) cryophilic, 3) endemic cool-temperate and 4) temperate species. Cronin and Ikeya (1987) recognized 26 circumpolar and 21 cryophilic species from several Plio-Pleistocene formations of Japan. They referred to ostracods known from Recent and/or Cenozoic deposits of the North Atlantic and adjacent arctic seas as “circumpolar species”, and species that typi- cally occur with circumpolar species in Japanese deposits (in most cases being members of high-latitude genera) as “cryophilic species”. Irizuki (1994) selected 13 circum- polar, 9 cryophilic and 4 endemic cold-water species from the Late Miocene Fujikotogawa Formation, Akita Pre- fecture, northern Japan. Irizuki and Matsubara (1995) de- scribed 5 circumpolar and 8 cryophilic species from the early Middle Miocene Suenomatsuyama Formation, Iwate Prefecture, northeastern Japan. They pointed out that circumpolar and cryophilic species preferred living in colder water than other species even during the Miocene. They also recognized 13 temperate species that preferred warmer waters than those mentioned as circumpolar and cryophilic indicators. The following 4 categories concern their (paleo) biogeographic distributions in the northern hemisphere and the relative water temperatures during deposition of the Fujina Formation. 1. Circumpolar species (4 species) These species were widely distributed from middle- to high-latitude regions in the Miocene (Figure 4; regions 1- 10), and dominate the upper horizons of the Fujina For- mation. Acanthocythereis dunelmensis (Norman), Munsey- ella hatatatensis Ishizaki, Palmenella limicola (Norman) and Robertsonites tuberculatus (Sars). 2. Cryophilic species (2 species) Since the Miocene, these species have been distributed around the Japanese islands (Figure 4; regions 5 and 9), and are prominent in the upper horizons of the Fujina For- mation with the circumpolar species. Acanthocythereis tsurugasakensis Tabuki and Robertsonites reticuliformus N \ Q N r7cQ7b\Q7d Region @R: Recent OH: Holocene a,b,c Q: Pleistocene PI [aP:Plio.-Pleist. 520" Place or ON: Pliocene Formation etc. OM: Miocene Figure 4. Geographic and stratigraphic distributions of char- acteristic species of the Fujina Formation. R [2a-e: Barents Sea (a-e: Elofson, 1941; b: Hartmann, 1992, 1993; c: Freiwald and Mostafawi, 1998); 2f: Russian Harbour (Neale and Howe, 1975); 3a, b: Greenland Sea (Elofson, 1941); 3c: Baffin Bay (Elofson, 1941); 3d: Labrador Sea (Hulings, 1967); 6a: North Sea (Elofson, 1941; McKenzie et al., 1989); 6b: Baltic Sea (Elofson, 1941; Rosenfeld, 1977); 7a: England (Elofson, 1941); 7b: Ireland (Elofson, 1941); 7c: Labrador Sea (Hulings, 1967); 7d: Bay of Biscay (Caralp et al., 1967; Caralp et al., 1968); 8: Gulf of Alaska (Brouwers, 1988, 1990); 9a: Sendai Bay (Ikeya and Itoh, 1991); 9b:off Shimane (Ikeya and Suzuki, 1992); 9c : Ulleung Basin (Cheong et al., 1986); 9d: Fukuoka (Hanai, 1957a)]. H [3a-c:Baffin Bay (Neale and Howe, 1975); 3d-f Baffin Island (Neale and Howe, 1975); 6: Sandnes Clay (Lord, 1980); 7a: Labrador Sea (Neale and Howe, 1975); 7b, c: off Nova Scotia (Neale and Howe, 1975); 9: Takahama shell bed (Kamiya and Nakagawa, 1993); 10: off NewYork (Neale and Howe, 1975)]. Q [4a: Prudhoe Bay Boreholes (McDougall, Brouwers and Smith, 1986); 4b, c: Gubik F. (Swain, 1961, 1963); 5a: Wakimoto F. (Cronin and Ikeya, 1987); 5b: Sasaoka F. (Cronin and Ikeya, 1987); 6: Esbjerg deposit (Bassiouni, 1965); 7a: Tyrrel Sea F. (Cronin, 1989); 7b, c: East Goldthwait Sea F. (Cronin, 1989); 7d, e: St. Lawrence Lowland (Cronin, 1981); 9: Shimosa G. (Yajima, 1982; Yajima and Lord, 1990; Ozawa et al., 1995); 10: off NewYork (Neale and Howe, 1975)]. P [3: Tjornes Beds (Cronin, 1991); Sa: Setana F. (Cronin and Ikeya, 1987); Sb: Tomikawa F. (Cronin and Ikeya, 1987); 5c: Daishaka F. (Tabuki, 1986); 9a: Kitaura F. (Cronin and Ikeya, 1987); 9b: Sawane F.(Cronin and Ikeya, 1987); 9c: Junicho F. (Cronin and Ikeya, 1987); 9d: Omma F. (Cronin and Ikeya, 1987; Kamiya et al., 1996); 9e: Ssukou F. (Malz, 1982)]. N [1: Kap Kobenhavn F. (Brouwers et al., 1991; Penney, 1993); 3: Lodin Elv F. (Penney, 1993); 9 a: Tatsunokuchi F. (Ishizaki, 1966); 9b: Tentokuji F. (Irizuki, 1996)]. M [5a: Kadono- sawa F. (Irizuki and Matsubara, 1994); 5b: Kamikoani F. (Yajıma, 1988); 9a: Hatatate F. (Ishizaki, 1966); 9b: Fujikotogawa F. (Irizuki, 1994); 9c: Togi Mud F. (Yajima, 1988); 9d: Yeonil G. (Huh and Paik, 1992a,b; Huh and Whatley, 1997); 9e: Fujina F. (This study); 9f: Kobana F. (Irizuki et al., 1998); 9g: Shukunohora Sandstone (Yajima, 1988)]. Gengo Tanaka et al. (Ishizaki). 3. Endemic cool-temperate species (3 species) These species are mainly distributed around the Japan Sea area from the Miocene to the Recent (Figure 4; regions 5 and 9), and occur throughout the Fujina Formation. Callistocythere japonica uranipponica Hanai, C. kyong- Juensis Huh and Whatley and Paijenborchella cf. tsuruga- sakensis Tabuki. C. japonica uranipponica was recogniz- ed by Hanai (1957a) as a subspecies of C. japonica, and is restricted along the Japan Sea coast and the Pacific side of northern Japan after the Miocene. C. kyongjuensis was re- ported with some cold-water species in the Early Miocene Chunbuk Conglomerate Formation of Korea (Huh and Paik, 1992a,b). P. tsurugasakensis occurs in the Omma Formation (Late Pliocene to Early Pleistocene) with many warm- and a few cold-water species (Ozawa, 1996). 4. Temperate species (5 species, including 3 new species) These have been distributed around the Japanese islands since the Miocene (Figure 4; regions 5 and 9), and domi- nate into the Lower Member to the lowermost part of the Upper Member of the Fujina Formation. Acanthocythereis koreana Huh and Whatley, A. takayasui Tanaka sp. nov., Falsobuntonia taiwanica Malz and Kotoracythere tsuka- goshii Tanaka sp. nov. and Palmoconcha irizukii Tanaka sp. nov. A. koreana was first reported with cold-water species in the Early Miocene Chunbuk Conglomerate Formation of Korea (Huh and Paik, 1992a, b). A. takaya- sui has been reported in the Early Miocene from Mizunami, central Japan with some warm- and shallow-water species (as F. taiwanica; Yajima,1988, pl. 1, fig. 7), but this spe- cies occurred with some colder species in the Early Miocene of Korea (as A. obai; Huh and Paik, 1992a, pl. 2, fig. 14, and F. taiwanica; Huh and Paik, 1992b, pl. 2, fig. 14). F. taiwanica, P. irizukii and K. tsukagoshii occurs in horizons deposited under warm-water conditions of the Early-Middle Miocene Kadonosawa Formation, Iwate Pre- fecture, northeastern Japan (as K. sp.; Irizuki and Matsu- bara, 1994, pl. 1, fig. 3). K. tsukagoshii also occurs in the Omma Formation (Late Pliocene to Early Pleistocene) (as Pectocythere quadrangulata; Ozawa, 1996, pl. 8, fig. 2). Thus, it is probable that these temperate species adapted to colder environments during the Miocene in the Japan Sea area. Discussion and conclusion According to Ikeya and Cronin (1993), the Recent Japan Sea proper water is characterized by the ostracod species A. dunelmensis, Elofsonella concinna, P. limicola, Robert- sonites, Cluthia and Rabilimis, and these species suggest cold-water isotherms along the upper slope at depths of Miocene ostracods from Fujina Formation RI, = LIN i PS = À G Ss ai ot Figure 5. Internal views of each species. 1: Kotoracythere tsukagoshii Tanaka sp. nov., female, LV, paratype, Loc. 1-A15, SUM-CO-1211 2: Cluthia tamayuensis Tanaka sp. nov., female, RV, paratype, Loc. 1-A1, SUM-CO-1217; 3: Cluthia subjaponica Tanaka sp. nov., female, LV, paratype, Loc. 1-A15, SUM-CO-1220; 4: Laperousecythere ikeyai Tanaka sp. nov., male, LV, paratype, Loc. 1-A11, SUM-CO-1229; 5: Acanthocythereis fujinaensis Tanaka sp. nov.., female, LV, paratype, Loc. 1-A11, SUM-CO-1234; 6: Acanthocythereis izumoensis Tanaka sp. nov., female, LV, paratype, Loc. 1-A17, SUM-CO-1239; 7: Robertsonites yatsukanus Tanaka sp. nov., male, LV, paratype, Loc. 2-B1, SUM-CO-1249; 8: Ambtonia shimanensis Tanaka sp. nov.. LV, paratype, Loc. 1-A19, SUM-CO-1252; 9: Ambtonia takayasui Tanaka sp. nov., female, LV, paratype, Loc. 1-A15, SUM-CO-1256; 10: Palmoconcha irizukii Tanaka sp. nov., female, LV, paratype, Loc. 1-A15, SUM-CO-1261. Scale bar is 0.10 mm. ~ 3 + © S “4 S = S > fe) 50 = © (©) Miocene ostracods from Fujina Formation 100-300 m. These assemblages resemble the Middle Mio- cene assemblage from the uppermost part of the Lower Member to the Upper Member of the Fujina Formation. Sakumoto er al. (1996) reported some cephalopod species that indicate that the paleo-Tsushima warm-water current flowed in the Proto-Japan Sea. Warmer conditions are in- dicated by the absence of cool-water ostracodes in part of this formation and the presence of prominent circumpolar and cryophilic species towards the upper horizons of the Fujina Formation, so we think that the Fujina Formation gradually became colder and colder towards the upper hori- zon, and that the warm-water current did not influence the benthic ostracods. Similar results have also been recog- nized from the benthic molluscan assemblages (Ogasawara and Nomura, 1980; Takayasu, 1986). Hence, it is con- cluded that during the early Middle Miocene period, tem- perate Pacific-side species invaded the coastal and offshore seafloor of the Japan Sea, and afterwards, with the change in marine climate and regional tectonic events, some taxa became isolated in embayments and offshore areas and adapted to cooler conditions. Systematic descriptions (by G. Tanaka) All the illustrated specimens are deposited in the collec- tions of the Shizuoka University Museum (SUM-CO- Number). Type locality of all new species is indicated by the index number: Loc. 1 or 2-horizon number; (Loc. 1: 35° Zanes 023; Loc: 2: 35° 25.6 N; 133° 01.4°E). Morphological terms follow the usage of Hanai (1961), Scott (1961) and Athersuch er al. (1989). The following abbreviations are used in this paper: C, carapace; RV, right valve; LV, left valve; L, length of valve; H, height of valve. Order Podocopida Sars, 1866 Superfamily Cytheroidea Baird, 1850 Family Eucytheridae Puri, 1954 Subfamily Pectocytherinae Hanai, 1957 Genus Kotoracythere Ishizaki, 1966 Kotoracythere tsukagoshii Tanaka sp. nov. Figures 5.1, 6.1-6.3 Kotoracythere sp. Irizuki and Matsubara, 1994, pl. 1, fig. 3. Pectocythere quadangulata Hanai, Ozawa, 1996, pl. 8, fig. 2. Etymology.—In honor of A. Tsukagoshi (Shizuoka Uni- versity, Japan) a specialist in ostracod systematics. Types.—Holotype, LV of male, SUM-CO-1208 (L = 0.66 mm, H = 0.32 mm). Paratypes, RV of male, SUM- CO-1209 (L = 0.67 mm, H = 0.32 mm); C of female, SUM- CO-1210 (L = 0.64 mm, H = 0.33 mm); LV of female, SUM-CO-1211 (L = 0.64 mm, H = 0.32 mm). Type locality.—Loc. 1-A15. Diagnosis.— Valve oblong box-shaped. Surface orna- mented by scattered deep pits and very weak reticulations. Vestibule widely developed along anteroventral margin. Radial pore canals few. Anterior and posterior teeth of median element composed of upper and lower elements re- spectively. Description.—Valve oblong box-shaped in lateral view. Anterior margin evenly rounded with infracurvature; dorsal margin straight, sloping gently toward posterior; posterior margin truncated dorsally and rounded ventrally; ventral margin nearly straight. Large sexual dimorphism; in lat- eral view, male forms more elongate; in dorsal view, fe- male forms having inflated carapace in the posteroventral area. Eye spot not observed. Surface ornamented by scattered deep pits, which are the openings of normal pore canals, and very weak reticulation. In dorsal view, cara- pace is elongate ovate, widest in the posteromedian area, but compressed in the median area in female forms. In an- terior view, carapace subovate, broadest at point near mid- height. Marginal zone broad anteriorly, vestibula widely developed in the anteroventral area and narrowly in the posteroventral area. Marginal pore canals few, 7 in ante- rior. 5 in posterior. Selvage well developed. Hinge pentodont: In LV, anterior and posterior elements are interiorly opened sockets respectively; median element is a crenulate bar with teeth at anterior and posterior termina- tions which are composed of upper and lower elements re- spectively. One V-shaped frontal scar. Four elliptical adductor scars are in a vertical row, the middle two are nar- row. Two small elliptical mandibular scars. Two dorsal scars (one elliptical, dorsomedial; one elliptical, mid- dorsal). Prominent fulcral point. Remarks.—This species differs from K. sp. widely re- ported from Plio-Pleistocene formations of north and cen- tral Japan (Ishizaki and Matoba, 1985; Tabuki, 1986; Cronin and Ikeya, 1987; Ozawa, 1996), in its very weak re- ticulation. The present species is distinguished from Pectocythere tsiuensis Brouwers, 1990 from the Quaternary @ Figure 6. 1-3, Kotoracythere tsukagoshii Tanaka sp. nov. 1a-e: male LV, holotype, Loc. 1-A15, SUM-CO-1208; 2a-c: male RV, Loc. 1-A15, SUM-CO-1209; 3a-d: female carapace, Loc. 1-A15, SUM-CO-1210. 4-5, Cluthia tamayuensis Tanaka sp. nov. 4a-e: female LV, holotype, Loc. 1-A16, SUM-CO-1215; 5a-c: male RV, paratype, Loc. 1-A15, SUM-CO-1216. 6-7, Cluthia subjaponica Tanaka sp. nov. 6a-e: female LV, holotype, Loc. 1-A16, SUM-CO-1218; 7a-c: male LV, paratype, Loc. 1-A15, SUM-CO-1219. uranipponica Hanai, 1957, male LV, Loc. 1-A16, SUM-CO-1213. SUM-CO- 1214. 8: Callistocythere japonica 9: Callistocythere kyongjuensis Huh and Whatley, 1997, male LV, Loc. 1-A15, 10: Munseyella hatatatensis Ishizaki, 1966, male RV, Loc. 2-B3, SUM-CO-1212. Scale bar is 0.10 mm. sediments of the Gulf of Alaska, North America, in its very weak reticulation and the outline of the anterior margin. Occurrences.—Early to Middle Miocene and Pleistocene sediments, Honshu, Japan (M5a, M9e and P9d; see Figure 4). Genus Munseyella van den Bold, 1957 Munseyella hatatatensis Ishizaki, 1966 Figure 6.10 Munseyella hatatatensis Ishizaki, 1966, p. 153, pl. 19, fig. 2; Cronin and Ikeya, 1987, p. 76, pl. 3, fig. 16; Ikeya and Itoh, 1991, fig. 19A; Huh and Paik, 1992b, pl. 3, fig. 9; Irizuki, 1994, p. 8, pl. 1, fig. 2; Kamiya er al., 1996, pl. 2, fig. 3; Ozawa, 1996, pl. 7, fig. 2. Munseyella mananensis Hazel and Valentine, 1969, p. 749-751, pl. 97, figs. 19-24, pl. 98, figs. 1, 3, 4, 11, 12, text-figs. 4a, b, 5a, e, g; Cronin, 1989, pl. 2, fig. 8. Remarks.—Cronin and Ikeya (1987) thought that M. hatatatensis was conspecific with M. mananensis Hazel and Valentine, 1969. Based on carapace morphology and geographical distribution, I have followed their opinion. Occurrences. —Miocene to Recent sediments of North Atlantic, Japan and Korea (H3a-c, P5a, b, Q5b, Q7a, b, H7a-c, M9a, b, d, e, P9c, d, R9a, Q10, H10; see Figure 4). Family Leptocytheridae Hanai, 1957 Genus Callistocythere Ruggieri, 1953 Callistocythere japonica uranipponica Hanai, 1957 Figure 6.8 Callistocythere japonica uranipponica Hanai, 1957a, p. 457-459, pl. 9, figs. 3a-c; Ishizaki and Matoba, 1985, pl. 2, fig. 8; Kamiya and Nakagawa, 1993, pl. 2, fig. 1. Callistocythere cf. japonica uranipponica Hanai. Ishizaki, 1966, p. 147, pl. 16, fig. 13. Remarks.—C. japonica uranipponica was recognized by Hanai (1957a) as a subspecies of C. japonica. C. japonica uranipponica is distinguished from C. japonica in having a more narrowly rounded posteroventral margin. Occurrences.—Miocene to Recent sediments along the Japan Sea and the north Pacific areas of Japan (Q5b, M9e, N9a, H9, R9d; see Figure 4). Callistocythere kyongjuensis Huh and Whatley, 1997 Figure 6.9 Callistocythere kyongjuensis Huh and Whatley, 1997, p. 32, 34, pl. 1, figs. 1-6. Gengo Tanaka et al. Callistocythere sp. A Huh and Paik, 1992b, pl. 3, fig. 11. Remarks.— This is the first reporting of C. kyongjuensis from Japan. Occurrences.—Miocene sediments of the south Japan Sea side areas (M9d, e; see Figure 4). Genus Cluthia Neale, 1973 Cluthia tamayuensis Tanaka sp. nov. Figures 5.2, 6.4, 6.5 Etymology.—For the type locality in the town of Tamayu. Types.—Holotype, LV, SUM-CO-1215 (L = 0.41 mm, H = 0.26 mm). Paratypes, RV of male, SUM-CO-1216 (L = 0.39 mm, H = 0.24 mm); RV of female, SUM-CO-1217 (L = 0.41 mm, H = 0.24 mm). Type locality.—Loc. 1-A16. Diagnosis.—alve subreniform. Anterior margin evenly rounded. Surface densely pitted with small, deep, polygo- nal pits. A mid-ventral carinal ridge runs toward the mid- posterior area. Radial pore canals (10 anteriorly; 10 posteriorly). Significant sexual dimorphism. Description.—Valve subreniform in lateral view. An- terior margin evenly rounded; dorsal margin straight, slop- ing toward posterior; posterior margin straight (LV), truncate (RV); ventral margin concave. Large sexual dimorphism; in lateral view, male forms more elongate; in dorsal view, female forms inflated laterally. Eye spot not observed. Surface densely pitted with small, deep, po- lygonal pits. A carinal ridge occupies the mid-ventral area, runs toward the mid-posterior area. One tubercle de- veloped in the posterodorsal area. In dorsal view, cara- pace appears compressed and subhexagonal; lateral outline sinuate, anterior end more pointed than posterior. In ante- rior view, carapace subpentagonal, broadest at the carinal ridge; anterior marginal rim strong. Marginal zone nar- row, with narrow anterior and posterior vestibula. Marginal pore canals are straight and number 10 anteriorly; 12 ventrally; 10 posteriorly. Selvage well developed. Hinge entomodont: In RV, anterior element is an elliptical tooth; a crernulated median socket lies just below the smooth bar; posterior element is a well-developed toothplate. One very large U-shaped frontal scar. Four adductor scars in a vertical row (the uppermost and lower- most are semicircular, the middle two are elliptical). One semicircular mandibular scar. Two dorsal scars (one elon- gate dorsomedial; one semicircular mid-dorsal). Remarks.—his species differs from C. japonica Tabuki, 1986 from the Plio-Pleistocene Daishaka Formation, north- ern Japan, in its posterior outline,deep polygonal pits and the carinal ridge toward mid-posterior. The present spe- Miocene ostracods from Fujina Formation 9 cies is distinguished from C. ishizakii Zhao, 1988 (MS) from the Late Pleistocene and Holocene drilling cores of the Okinawa Trough, East China Sea (in Ruan and Hao, 1988), in its lateral outline and deep polygonal pits. Occurrence.—nly from the Fujina Formation (M9e; see Figure 4). Cluthia subjaponica Tanaka sp. nov. Figures 5.3, 6.6, 6.7 Etymology.—For its close resemblance with Cluthia ja- ponica Tabuki. Types.—olotype, LV of female, SUM-CO-1218 (L = 0.40 mm, H = 0.24 mm). Paratypes, LV of male, SUM- CO-1219 (L = 0.40 mm, H = 0.23mm); LV of female, SUM-CO-1220 (L = 0.40 mm, H = 0.24 mm). Type locality.—Loc. 1-A16. Diagnosis.— Valve subreniform. Anterior margin even- ly rounded. Surface densely pitted with small, deep, round pits. Radial pore canals (23 anteriorly; 16 posteriorly). Prominent fulcral point. Sexual dimorphism weak. Description. — Valve subreniform in lateral view. An- terior margin evenly rounded; dorsal margin straight, slop- ing toward posterior; posterior margin straight; ventral margin nearly straight to slightly convex. Sexual dimor- phism weak. Eye spot not observed. Surface densely pit- ted with small, deep, round pits. One tubercle developed in the posterodorsal area. In dorsal view, lateral outline nearly straight; anterior end more pointed than posterior. In anterior view, LV arched, broadest at point near mid- height; anterior marginal rim strong. Marginal zone rela- tively broad, with narrow anterior and posterior vestibula. Marginal pore canals are straight, numbering 23 in anterior, 5 in ventral, 16 in posterior. Selvage well developed. Hinge entomodont: in LV, anterior and posterior elements are elongate sockets connected by a containant respec- tively; a crernulated median bar lies just below the containant. One very large U-shaped frontal scar. Four adductor scars in a vertical row (the uppermost one is semi- circular, the lower three are elliptical). One circle mandibular scar. One elliptical dorsal scar mid-dorsally. Prominent fulcral point. Remarks.—This species differs from C. japonica Tabuki, 1986 from the Plio-Pleistocene Daishaka Formation, the north Japan, in its lateral outline, small round pits and lack of tubercles in the posterodorsal and posteroventral areas. Occurrence.—Only from the Fujina Formation (M9e; see Figure 4). Subfamily Schizocytherinae Mandelstam, 1960 Tribe Paijenborchellini Deroo, 1966 Genus Paijenborchella Kingma, 1948 Paijenborchella cf. tsurugasakensis Tabuki, 1986 Figure 7.1, 7.2 Paijenborchella tsurugasakensis Tabuki, 1986, p.65-67, pl. 2, figs. 12-19, text-fig. 18-3; Kamiya er al., 1996, pl. 3, fig. 3; Ozawa, 1996, pl. 7, fig. 8. Remarks.—This species was first described from the Plio-Pleistocene Daishaka Formation, the north Japan by Tabuki (1986). Specimens from the Fujina Formation dif- fer slightly from the type specimen, in the shape of posteroventral area. Occurrence. — Miocene to Pleistocene sediments of Japan Sea side areas and northern Honshu, Japan (PSc, M9e and P9d; see Figure 4). Genus Palmenella Hirschmann, 1916 Palmenella limicola (Norman, 1865) Figure 7.3 Cythere limicola Norman, 1865a, p. 193; Norman, 1865b, p. 20, pl. 6, figs. 1-4. Palmenella limicola (Norman). Hirschmann, 1916, p. 582-594, text-figs.8-27; Elofson, 1941, p.277, 278, text-fig. 21; Triebel, 1949, p.189, 190, pl. 2, figs. 5, 6; Swain, 1963, p.830, 831, pl.99, figs. 3a-d, text-fig.9d; Ishizaki, 1966, p.156, pl.19, fig. 8; Hanai, 1970, p. 704, text-figs. 6B (solid line), 7G, H; Neale and Howe, 1975, pl. 5, figs. 7, 8; Rosenfeld, 1977, p. 15, 16, pl. 1, figs. 3-6; Lord, 1980, pl. 3, fig. 6; Cronin, 1981, p. 412, pl. 11, figs. 1, 2, 4; Cheong et al., 1986, pl. 2, fig. 1; McDougall er al., 1986, pl. 13, fig. 8; Cronin and Ikeya, 1987, p. 86, pl. 2, fig. 17; Brouwers, 1988, figs. 5, 6; Yajima, 1988, pl. 2, fig. 8; Athersuch et al., 1989, p. 82, 83, pl. 1 (2), fig. 28; Brouwers, 1990, pl. 1, fig. 15, pl. 4, figs. 9, 12, 17, pl. 6, fig. 1; Brouwers er al., 1991, pl. 1, fig. 7; Cronin, 1991, fig. 7-11; Huh and Paik, 1992a, pl. 1, fig. 10; Huh and Paik, 1992b, pl. 1, fig. 10; Hartmann, 1993, p.241, pl. 1, figs. 2-4; Irizuki, 1994, p. 8, pl. 1, fig. 4; Irizuki and Matsubara, 1994, pl. 1, fig. 7; Ozawa et al., 1995, pl. 1, fig. 4; Kamiya et al., 1996, pl. 2, fig. 1; Ozawa, 1996, pl. 7, fig. 9; Irizuki et al., 1998, fig. 5-8; Freiwald and Mostafawi, 1998, pl. 59, fig. 4; (not) Wagner, 1970, pl. 4, fig. 14. Kyphocythere limnicola (Norman). Swain, 1961, fig. 2-20. Palmenella sp. Hanai, 1961, p. 369, text-fig.11, figs. 4a, b. Occurrences.—Miocene to Recent sediments of high- latitude areas (N1, Pla, b, Qla, b, R2a-e, P3, R3a, c, Q4a, b, MSa, b, P5a, b, H6a, R6a, b, R7a, b, R8, M9b-f, P9d, Q9, R9c; see Figure 4). Gengo Tanaka et al. : yi Ay & FEES RR Miocene ostracods from Fujina Formation 11 Family Hemicytheridae Puri, 1953 Subfamily Urocythereidinae Hartmann and Puri, 1974 Genus Urocythereis Ruggieri, 1950 Urocythereis pohangensis Huh and Whatley, 1997 Figure 7.8 Urocythereis pohangensis Huh and Whatley, 1997, p. 36, 37, pl. 2, figs. 3-9. Urocythereis sp. Huh and Paik, 1992a, pl. 1, figs. 17, 18; Huh and Paik, 1992b, pl. 1, figs. 17, 18. Remarks.—This is the first report of U. pohangensis from Japan. Occurrences.— Miocene sediments of the south Japan Sea side areas (M9d,e; see Figure 4). Genus Laperousecythere Brouwers, 1993 Laperousecythere ikeyai Tanaka sp. nov. Figures 5.4, 7.4-7.7 Etymology.—In honor of N. Ikeya (Shizuoka University, Japan), who is a specialist in the taxonomy and biogeo- graphy of the Cenozoic and Recent marine ostracods of the western Pacific region. Types.—Holotype, LV of male, SUM-CO-1225(L = 0.95 mm, H = 0.51 mm). Paratypes, RV of male, SUM-CO- 1226 (L = 0.95 mm, H = 0.49 mm); LV of female, SUM- CO-227 (L = 0.92 mm, H = 0.55 mm); RV of female, SUM-CO-1228 (L = 0.89 mm, H = 0.49 mm); LV of male, SUM-CO-1229 (L = 0.91 mm, H = 0.52 mm). Type locality.—Loc. 1-A15. Diagnosis.— Valve subquadrate. Surface ornamented by polygonal reticulations and a carinal ridge runs nearly parallel to anterior and ventral margin. Vestibule narrow. Four circular/elliptical adductor scars, in three of these the ventral side is subdivided. Description.—Valve subquadrate in lateral view. An- terior margin evenly rounded with infracurvature; dorsal margin straight, sloping gently toward posterior; posterior margin truncated and caudated ventrally; ventral margin nearly straight to slightly convex. Large sexual dimor- phism; in lateral view, male forms more elongate; in dorsal view, the carapaces of female forms are inflated postero- ventrally. Eye spot large and flat. Surface ornamented by polygonal reticulations. A strong carinal ridge occurs at base of eye spot, runs nearly parallel to anterior and ventral margin, and ends at posteroventral area. A subcentral tu- bercle is developed. In dorsal view, lateral outline nearly straight; anterior end more pointed than posterior. On dor- sal surface of carapace a V-shaped groove runs along hinge line (in vertical section). In anterior view, carapace subovate, broadest at point near mid-height. Marginal zone relatively broad, with narrow anterior and posterior vestibula. Marginal pore canals are straight and number 35 in anterior, 17 in posterior, and a few mid-ventrally. Selvage and list well developed. Hinge holamphidont: in LV, anterior element has an auxiliary tooth in a large elon- gate socket; anteromedian element is a smooth tooth, posteromedian element is a bar; posterior element is an elongate socket. Three frontal scars (the upper two are cir- cular, the lowermost one is elliptical). Four circular/ellipti- cal adductor scars; the three at ventral side are subdivided. A deep anteromedian depression between frontal and ad- ductor scars, corresponding to the external subcentral tuber- cle. One elliptical mandibular scar. Six dorsal scars (two dorsomedially; two mid-dorsally; two anterodorsally); the uppermost one is semicircular, the others are circular/ellip- tical. Prominent fulcral point. One semicircular ventral scar is below and anterior to the mandibular scar. Ocular sinus conspicuous. Remarks.—This species differs from L. robusta (Tabuki, 1986) from the Plio-Pleistocene Daishaka Formation, northern Japan, in its slightly convexed ventral margin, polygonal reticulation and lack of secondary reticulations. The present species is distin- guished from L. ishizakii Irizuki and Matsubara, 1995 from the Early-Middle Miocene Suenomatsuyama Formation, northeast Japan, in its outline and possession of a strong carinal ridge. Occurrence.—Only from the Fujina Formation (M9e; see Figure 4). Family Trachyleberididae Sylvester-Bradley, 1948 Subfamily Trachyleberidinae Sylvester-Bradley, 1948 Tribe Trachyleberidini Sylvester-Bradley, 1948 Genus Acanthocythereis Howe, 1963 @ Figure7. 1-2, Paijenborchella cf. tsurugasakensis Tabuki, 1986. A16, SUM-CO-1222; 3: Palmenella limicola (Norman, 1865), female LV, Loc. 1-A18, SUM-CO-1223. 4a-e: male LV, holotype, Loc. 1-A15, SUM-CO-1225; 5a-c: male RV, paratype, Loc. 1-A15, SUM-CO-1226; 6a-c: female LV, paratype, nov. la: male LV, Loc. 1-A17, SUM-CO-1221; 2a, b: female LV, Loc. 1 4-7, Laperousecythere ikeyai Tanaka sp. Loc. 1-A15, SUM-CO-1227; 7a-c: female RV, paratype, Loc. 1-A15, SUM-CO-1228. 8: Urocythereis pohangensis Huh and Whatley, 1997, male LV, Loc. 1-A15, SUM-CO - 1224. 9: Acanthocythereis dunelmensis (Norman, 1865), female LV, Loc. 2-B4, SUM-CO - 1230. Acanthocythereis koreana Huh and Whatley, 1997, female LV, Loc. 1-A13, SUM-CO-1240. 10: 11-13, Acanthocythereis fujinaensis Tanaka sp. nov. 11a-d: male C, holotype, Loc. 1-A13, SUM-CO-1231; 12a-e: female LV, paratype, Loc. 1-A11, SUM-CO-1232; 13a-c: female RV, paratype, Loc. 1-All, SUM-CO-1233. Scale bar is 0.10 mm. 12 Gengo Tanaka et al. Acanthocythereis dunelmensis (Norman, 1865) Figure 7.9 Cythereis dunelmensis Norman, 1865a, p. 193; Norman, 1865b, p. 22, pl. 7, figs. 1-4. Cythere dunelmensis (Norman). Brady, 1868, p. 416, pl. 30, figs. 1-12. Cythereis dunelmensis (Norman). Elofson, 1941, p. 296-300, figs. 8-11, text-figs. 29, 30; Elofson, 1943, p. 10; (not) Tressler, 1941, p. 100, pl. 19, fig. 21. Trachyleberis dunelmensis (Norman). Hulings, 1967, p. 324, figs. 7, 8T, pl.4, figs. 24, 25; Caralp et al., 1967, pl.13, fig. 1; Caralp et al., 1968, pl.10, fig. 1. Acanthocythereis dunelmensis (Norman). Neale and Howe, 1975, pl. 1, figs. 3, 11, 13-16; Rosenfeld, 1977, p. 23, 24, pl. 5, figs. 65-68; Lord, 1980, pl. 1, figs. 8-13; Cronin, 1981, p. 400, pl. 8, figs. 1, 2; Cronin, 1986, pl. 2, fig. 9; McDougall et al., 1986, pl. 13, figs. 2-4; Cronin and Ikeya, 1987, pl. 1, figs. 1, 4; Brouwers, 1988, figs. 5-7; Athersuch er al., 1989, p. 133, 134, pl. 3 (10), fig. 52; Cronin, 1989, pl. 2, fig. 9; McKenzie et al., 1989, pl. 1, fig. 1; Hartmann, 1992, pl. 5, figs.4-6; Ikeya and Suzuki, 1992, pl. 1, fig. 2; Brouwers, 1993, pl. 1, figs. 1-5, pl. 2, fig. 1, pl. 16, fig. 1, text-fig. 3, 4; Irizuki, 1994, p. 10, pl. 2, fig. 3; Irizuki, 1996, figs. 7-1, 2; Kamiya et al., 1996, pl. 2, figs. 8-10; Ozawa, 1996, pl. 1, fig. 1; Freiwald and Mostafawi, 1998, pl. 59, figs. 1, 2. Acanthocythereis cf. A. dunelmensis (Norman). Penney, 1993, fig. 5-I. ? Acanthocythereis dunelmensis (Norman). Cronin and Compton- Gooding, 1987, pl. 2, fig. 4. ? Acanthocythereis cf. A. dunelmensis (Norman). Cronin, 1991, fig. 8-11. Cletocythereis dunelmensis dunelmensis (Norman). Bassiouni, 1965, pl. 2, fig. 8. Cletocythereis dunelmensis minor Bassiouni, 1965, p. 513, 514, pl. 2, fig. 9. Actinocythereis sp., Swain, 1961, fig. 2-36. Cletocythereis elofsoni elofsoni Bassiouni, 1965, p. 514-516, pl. 2, figs. 4, 5. Cletocythereis elofsoni elofsoni abbreviata, Bassiouni, 1965, p. 516, pl. 2, figs. 6, 7. Cletocythereis noblissimus Swain, 1963, p. 824, 825, pl. 98, fig. 5, pl. 99, figs. 15a, b, text-fig. 10a. Acanthocythereis ? sp. A Cheong et al., 1986, pl. 2, fig. 17. Acanthocythereis ? sp. B Cheong et al., 1986, pl. 2, fig. 18. Acanthocythereis ? sp. C Cheong et al., 1986, pl. 2, fig. 19. Trachyleberis ? rastromarginata (Brady). Swain, 1961, fig. 2-32. Occurrences.—Miocene to Recent sediments of high- latitude areas (R2a-f, P3, R3a, b, d, Q4a-c, P5a, b, Q5a, b, Q6a, H6a, R6a, b, Q7a-e, R7a-d, R8, M9b, N9b, P9a, b, d, R9b, c; see Figure 4). Acanthocythereis fujinaensis Tanaka sp. nov. Figures 5.5, 7.11-7.13 Etymology.—For the type locality. Types.—Holotype, C of male, SUM-CO-1231 (L = 0.41 mm, H = 0.24 mm). Paratypes, LV of female, SUM-CO- 1232 (L = 0.43 mm, H = 0.27 mm); RV of female, SUM- CO-1233 (L = 0.42 mm, H = 0.27 mm); LV of female, SUM-CO-1234 (L = 0.46 mm, H = 0.29 mm). Type locality.—Loc. 1-A13. Diagnosis.—Valve subquadrate. Posterior margin even- ly rounded. Conical spines developed in the anteroventral margin. Surface ornamented by polygonal reticulations with clavate/conic conjunctive spines. Description.— Valve subquadrate in lateral view. An- terior margin evenly rounded with conical spines, espe- cially anteroventrally; dorsal margin straight, sloping to- ward posterior with several spines; posterior margin evenly rounded with conical spines posteroventrally; ventral mar- gin concave in male forms, nearly straight in female forms. Strong sexual dimorphism; in lateral view, male forms more elongate; in dorsal view, carapaces of female forms inflated posteroventrally. Eye spot large and protruding. Surface ornamented by polygonal reticulations with clavate/conical conjunctive spines. A row of clavate/coni- cal spines occurs at base of eye spot, runs parallel to ante- rior margin. Three parallel carinal ridges occupy the mid- ventral area, the uppermost one with clavate spines. A subcentral tubercle developed. In dorsal view, carapace elongate subovate, pointed in front. In anterior view, cara- pace subovate, lateral outline nearly straight. Marginal zone relatively broad, with very narrow anterior and poste- rior vestibula. Marginal pore canals are straight/curved with median swellings and number 42 in anterior, 18 in ventral, 23 in posterior. Selvage developed. Hinge holam- phidont: in LV, anterior element has an auxiliary tooth in a large elongate socket; anteromedian element is a smooth tooth, posteromedian element is a bar; posterior element is an elongate socket. One U-shaped frontal scar. Four ad- ductor scars in a vertical row (the uppermost one is semicir- cular, the lower three are elliptical). One elliptical mandibular scar. Three dorsal scars mid-dorsally; the low- ermost one protrudes like a tongue, the upper two are ellip- tical. Prominent fulcral point. One elliptical ventral scar is below and anterior to the mandibular scar. Ocular sinus conspicuous. Remarks.—This species differs from A. koreana Huh and Whatley, 1997 from the Miocene, Korea, in its evenly rounded posterior margin, developed anteroventral conical spines and prominent clavate conjunctive spines. Occurrence.—Only from the Fujina Formation (M9e; see Figure 4). Miocene ostracods from Fujina Formation 13 Acanthocythereis izumoensis Tanaka sp. nov. Figures 5.6, 8.1-8.4 Etymology.—Izumo is the ancient provincial name of the type locality. Types.—Holotype, LV of male, SUM-CO-1235 (L = 0.92 mm, H = 0.56 mm). Paratypes, RV of male, SUM- CO-1236 (L = 0.91 mm, H = 0.53 mm); LV of female, SUM-CO-1237 (L = 0.90 mm, H = 0.60 mm); RV of fe- male, SUM-CO-1238 (L = 0.92 mm, H = 0.59 mm); LV of female, SUM-CO-1239 (L = 0.90mm, H = 0.61 mm). Type locality.—Loc. 1-A16. Diagnosis.—Valve subquadrate. In male forms, a large conical spine at the posteroventral corner is prominent. Surface smooth with scattered clavate/conical spines. A row of clavate spines runs parallel to mid-ventral margin. In anterior view, carapace subtrapezoidal, broadest at about one-fifth height from the ventral side. No vestibule. Description. — Valve subquadrate in lateral view. Anterior margin evenly rounded with conical spines, espe- cially anteroventrally; dorsal margin straight, sloping to- ward posterior with several clavate/conical spines; posterior margin evenly rounded with several conical spines, a large conical spine at the posteroventral corner is more promi- nent in male forms; ventral margin convex. Strong sexual dimorphism; in lateral view, male forms more elongate; in dorsal view, female forms having inflated carapace in the mid-posterior area. Eye spot large and protruding. Sur- face smooth with scattered clavate/conical spines. A row of clavate/conical spines occurs at base of the eye spot, runs parallel to anterior margin. A row of clavate spines runs parallel to mid-ventral margin. In dorsal view, cara- pace elongate subovate, pointed in front. In anterior view, carapace subtrapezoidal, broadest at about one-fifth height from the ventral side. Marginal zone broad; vestibule not developed. Marginal pore canals are straight/curved with median swellings and number 40 in anterior and 20 in pos- terior. Selvage developed. Hinge holamphidont: in LV, anterior element has an auxiliary tooth in a large elongate socket; anteromedian element is a smooth tooth, posteromedian element is a bar; posterior element is an elongate socket. One V-shaped frontal scar. Four adduc- tor scars in a vertical row (the uppermost and lowermost are semicircular, the middle two are elliptical). One ellip- tical mandibular scar. Three dorsal scars; the dorsomedian one protrudes like a tongue, the mid-dorsal two are elon- gate. Prominent fulcral point. One elliptical ventral scar is below and posterior to the mandibular scar. Ocular sinus conspicuous. Remarks.— This species differs from A. mutsuensis Ishizaki, 1971 from the Recent sediments of Mutsu Bay in northern Japan, in its row of clavate spines running parallel to the mid-ventral margin. The present species is distin- guished from A. koreana Huh and Whatley, 1997 from the Miocene, Korea, by its smooth surface with scattered clavate/conical spines. Occurrence.—Only from the Fujina Formation (M9e; see Figure 4). Acanthocythereis koreana Huh and Whatley, 1997 Figure 7.10 Acanthocythereis koreana Huh and Whatley, 1997, p. 39, pl. 3, figs. 6-12. Acanthocythereis mutsuensis Ishizaki. Huh and Paik, 1992a, pl. 2, figs. 8, 9; Huh and Paik, 1992b, pl. 2, figs. 8, 9. Acanthocythereis dunelmensis (Norman). Irizuki and Matsubara, 1994, pl. 1, fig. 13. Occurrences.—Miocene sediments of the south Japan Sea side areas (M9d, e; see Figure 4). Acanthocythereis tsurugasakensis Tabuki, 1986 Figure 8.5 Acanthocythereis tsurugasakensis Tabuki, 1986, p. 85, 86, pl. 11, figs. 2-10, text-fig. 20-2; Ozawa, 1996, pl. 1, fig. 3. Occurrences.—Miocene to Pleistocene sediments along the Japan Sea and Northern Pacific areas of Japan (P5c, M9e and P9d; see Figure 4). Genus Robertsonites Swain, 1963 Robertsonites japonicus (Ishizaki, 1966) Figure 8.6 Buntonia japonica Ishizaki, 1966, p. 156, 157, pl. 19, figs. 6, 7, text-fig.1, figs. 1, 5. Occurrences.— Miocene sediments of Honshu, Japan (M9a, e; see Figure 4). Robertsonites reticuliformus (Ishizaki, 1966) Figure 8.7 Buntonia reticuliforma Ishizaki, 1966, p. 157, 158, pl. 16, fig. 7, text-fig.1, fig. 1; Tabuki, 1986, p. 91-93, pl. 14, figs. 1-12, text-figs. 17-1, 2; Cronin and Ikeya, 1987, p. 84, pl. 2, fig. 15; Yajima and Lord, 1990, fig. 4-9; Huh and Paik, 1992a, b, pl. 2, fig. 13; Irizuki, 1994, p. 10, pl. 2, figs. 4-6; Irizuki, 1996, figs. 7-3, 4; Kamiya et al., 1996, pl. 3, fig. 6; Ozawa, 1996, pl. 8, fig. 6. Robertsonites ? reticuliforma (Ishizaki) [sic]. Yajima, 1982, p. 2055 PL A213: SS 8 + Ÿ S a S = a E © 50 = ® D Miocene ostracods from Fujina Formation 15 Remarks.—This species was first described by Ishizaki (1966) from the Middle Miocene Hatatate Formation in northern Japan. Specimens in Tabuki (1986), Irizuki (1994, 1996), Kamiya er al. (1996) and Ozawa (1996) have a prominent posterodorsal subvertical ridge. Occurrences. — Miocene to Pleistocene sediments of Honshu, Japan (P5c, Q5a, b, M9a, b, d, N9b, P9a, c, d, Q9a; see Figure 4). Robertsonites cf. tuberculatus (Sars, 1866) Figure 8.8 Cythereis tuberculata Sars, 1866, p. 37. Cythere tuberculata (Sars). Brady, 1868, p. 406, 407, pl. 30, figs. 25-39. Robertsonites tuberculata (Sars) [sic]. Hulings, 1967, p. 324, pl. 4, figs. 21-23; text-figs. 4e, 8p-8s; Neale and Howe, 1975, p. 419, pl. 1, fig. 1; Rosenfeld, 1977, p. 24, 25, pl. 5, figs. 61-64. Robertsonites tuberculatus (Sars). Cronin, 1981, p. 400, 402, pl. 8, fig. 5; Horne, 1983, p. 39-52, pls. 1-14; Athersuch er al., 1989, p. 148, 149, pl. 4 (7), fig. 59; Cronin, 1989, p. 133, pl. 2, fig. 10; McKenzie et al., 1989, pl. 1, fig. 12; Cronin, 1991, p. 779, fig. 8-2; Hartmann, 1992, p. 187, 188, pl. 5, figs. 7-12; pl. 6, figs. 1-6; Penney, 1993, fig. Sh. Robertsonites gubikensis Swain, 1963, p. 821, 822, pl. 98, figs. 8a, b; pl. 99, fig. 12; text-fig. 9b. Robertsonites logani (Brady and Crosskey). Swain, 1963, p. 823, pl. 97, fig. 13. Robertsonites tuberculatina [sic] Swain, 1963, p. 822, 823, pl. 98, fig. 10; pl. 99, fig. 1; text-fig. 9c. Remarks.—This species exhibits considerable variation in outline and ornament, with variable development of nodes and reticulation (Brouwers, 1993). Occurrences.—Miocene to Recent sediments of high- latitude areas (N1, R2b, f, N3, P3, R3d, Q4b, c, R6a, b, Q7b-e, R7c; see Figure 4). Robertsonites yatsukanus Tanaka sp. nov. Figures 5.7, 8.9-8.12 Etymology.—The district name of the type locality. Types.—Holotype, LV of male, SUM-CO-1245 (L = 0.95 mm, H = 0.53 mm). Paratypes, RV of male, SUM- CO-1246 (L = 0.93 mm, H = 0.51 mm); LV of female, SUM-CO-1247 (L = 0.94 mm, H = 0.59 mm); RV of fe- male, SUM-CO-1248 (L = 0.91 mm, H = 0.55 mm); LV of male, SUM-CO-1249 (L = 0.94 mm, H = 0.54 mm). Type locality.—Loc. 2-B1. Diagnosis.—Valve quadrate, tapering posteriorly. Sur- face ornamented by polygonal reticulations. Vestibula de- veloped in the anteroventral area and very narrow in the posteroventral area. One J-shaped frontal scar. Description.— Valve quadrate, tapering posteriorly in lateral view. Anterior margin evenly rounded, weakly denticulated anteroventrally; dorsal margin undulate, slop- ing toward posterior; posterior margin evenly rounded and weakly denticulated anteroventrally; ventral margin nearly straight. Strong sexual dimorphism; in lateral view, male forms are more elongate; in dorsal view female carapaces are inflated posteriorly. Eye spot small and flat. Surface ornamented by polygonal reticulations. Two anterior carinal ridges prominent, one running from the anterior part of eye spot to the anteroventral area, the other starting at base of eye spot, bifurcating in anterodorsal area and run- ning into anteroventral area. Three carinal ridges run nearly parallel to anterior, ventral and posterior margin and end at posterodorsal area. In dorsal view, carapace is elon- gate ovate. In dorsal surface of carapace a V-shaped groove runs along hinge line (in a vertical section). In an- terior view, carapace subovate, broadest at point near mid- height. Marginal zone relatively broad, vestibula developed in the anteroventral area and very narrow in the posteroventral area. Marginal pore canals straight, number 48 anteriorly, 15 ventrally and 14 posteriorly. Selvage de- veloped. Hinge holamphidont: in LV, anterior element is a large elongate socket; anteromedian element is a tongue like tooth, posteromedian element is a bar; posterior ele- ment is an elongate socket. One J-shaped frontal scar. Four adductor scars in a vertical row (the uppermost and lowermost are semicircular, the middle two are narrow). One elliptical mandibular scar. Eight dorsal scars (five dorsomedially; two mid-dorsally; one anterodorsally); the dorsomedian one protrude like a tongue, the others are cir- cular/elliptical. Fulcral point not observed. One elliptical ventral scar is below and posterior to the mandibular scar. Ocular sinus conspicuous. Remarks.—This species differs from R. hanaii Tabuki, 1986 from the Plio-Pleistocene Daishaka Formation in @ Figure 8. 1-4, Acanthocythereis izumoensis Tanaka sp. nov. la-e: male LV, holotype, Loc. 1-A16, SUM-CO-1235; 2a-e: male RV, paratype, Loc. 1-A16, SUM-CO-1236; 3a-c: female LV, paratype, Loc. 1-A16, SUM-CO-1237; 4a-c: female RV, paratype, Loc. 1-A17, SUM- CO-1238. 5: Acanthocythereis tsurugasakensis Tabuki, 1986, female LV, Loc. 2-B2, SUM-CO-1241. 6: Robertsonites japonicus (Ishizaki, 1966), male LV, Loc. 1-All, SUM-CO-1242. 7: Robertsonites reticuliformus (Ishizaki, 1966), male LV, Loc. 1-A15, SUM-CO-1243. cf. tuberculatus (Sars, 1866), female LV, Loc. 2-B4, SUM-CO-1244. 9-12, Robertsonites yatsukanus Tanaka sp. nov. 8: Robertsonites 9a-e: male LV, holotype, Loc. 2-B1, SUM-CO-1245; 10a-c: male RV, paratype, Loc. 2-B1, SUM-CO-1246; 11a-e: female LV, paratype, Loc. 2-Bl, SUM-CO-1247; 12a-c: female RV, paratype, Loc. 2-B1, SUM-CO-1248. Scale bar is 0.10 mm. = S + S 3 4 S S 3 Fr © (er) Ss © oO Miocene ostracods from Fujina Formation iy northern Japan, in its inflated carapace and three carinal ridges running nearly parallel to anterior, ventral and poste- rior margins. À. yatsukanus is distinguished from R. tsugaruana [sic] Tabuki, 1986 from the Plio-Pleistocene Daishaka Formation in northern Japan, in lack of secondary reticulations. Occurrence.—Only from the Fujina Formation (M9e; see Figure 4). Subfamily Buntoniinae Apostolescu, 1961 Genus Ambtonia Malz, 1982 Ambtonia shimanensis Tanaka sp. nov. Figures 5.8, 9.1, 9.2 Etymology.—The prefecture name, Shimane, of the type locality. Types.—Holotype, RV, SUM-CO-1250 (L = 0.61 mm, H = 0.33 mm). Paratypes, LV, SUM-CO-1251 (L = 0.63 mm, H = 0.35 mm); LV, SUM-CO-1252 (L = 0.65 mm, H = 0.36 mm). Type locality.—Loc. 1-All. Diagnosis. — Valve subcylindrical. Dorsal margin nearly straight. In dorsal view, carapace elongately arrow- head-shaped, tapered in front. Maximum width about one- sixth length from the posterior end. In anterior view, carapace subovate, broadest near mid-height. One V- shaped frontal scar. Description. — Valve subcylindrical in lateral view. Anterior margin evenly rounded; dorsal margin nearly straight; truncated and caudate ventrally; ventral margin nearly straight to slightly convex. Sexual dimorphism un- known. Eye spot not observed. Surface smooth, scat- tered deep punctations which are the openings of normal pore canals. Anterior area compressed along the anterior margin. In dorsal view, carapace elongately arrowhead- shaped, tapered in front. Maximum width at about one- sixth length from the posterior end. In anterior view, carapace subovate, broadest at point near mid-height. Marginal zone broad in the anterior area, vestibula devel- oped in the anteroventral area and very narrow in the posteroventral area. Marginal pore canals are straight and number 39 anteriorly, 7 ventrally and 11 posteriorly. Selvage and list well developed. Hinge hemiamphidont: in LV, anterior element has a large elongate socket; anteromedian element is a smooth elongate tooth, postero- median element is a crenulate bar; posterior element is an elongate socket with several lobes dorsally. One V-shaped frontal scar. Four elliptical adductor scars in a vertical row, the middle two of which are narrow. One elliptical mandibular scar. Two dorsal scars protrude like pivots in the dorsomedian area. Fulcral point not observed. One small round ventral scar is below and posterior to the mandibular scar. No ocular sinus. Remarks.—This species differs from A. obai (Ishizaki, 1971) from the Recent sediments of Mutsu Bay in northern Japan, in its caudate posteroventral margin, slightly convex ventral margin and compressed anterior area. The present species is distinguished from A. tongassensis Brouwers, 1993 from the Quaternary sediments of the Gulf of Alaska, North America, in its caudated posteroventral margin, nearly parallel dorsal and ventral margins, and number of marginal pore canals. This species differs from A. glabra Malz, 1982 from the Plio-Pleistocene Ssukou Formation of southwest Taiwan, in its straight dorsal margin. Occurrence.—Only from the Fujina Formation (M9e; see Figure 4). Ambtonia takayasui Tanaka sp. nov. Figures 5.9, 9.3, 9.4, 9.6 Falsobuntonia taiwanica Malz. Yajima, 1988, pl. 1, fig. 7; Huh and Paik, 1992b, pl. 2, fig. 14. Ambtonia obai (Ishizaki). Huh and Paik, 1992a, pl. 2, fig. 14. Etymology.—In honor of K. Takayasu (Center for Coast- al Lagoon Environments of Shimane University, Japan), who is a specialist in the taxonomy and paleoecology of the molluscs of the Fujina Formation. Types.—Holotype, LV of female, SUM-CO-1253 (L = 0.64 mm, H = 0.37 mm). Paratypes, RV of female, SUM- CO-1254 (L = 0.63 mm, H = 0.33 mm); RV of male, SUM- CO-1255 (L = 0.62 mm, H = 0.33 mm); LV of female, SUM-CO-1256 (L = 0.64 mm, H = 0.37 mm). Type locality.—Loc. 1-A16. Diagnosis. — Valve subcylindrical. arched. In dorsal view, carapace elongately arrowhead- shaped, tapered in front. Maximum width about one-fifth length from the posterior end. In anterior view, carapace subpentagonal, lateral outline nearly straight. One J- shaped frontal scar. Description. — Valve subcylindrical in lateral view. Anterior margin evenly rounded; dorsal margin arched; posterior margin truncated and caudated ventrally; ventral Dorsal margin @ Figure9. 1-2, Ambtonia shimanensis Tanaka sp. nov. la-c: LV, paratype, Loc. 1-A11, SUM-CO-1251; 2a-e: RV, holotype, Loc. 1-A11, SUM-CO-1250. 3-4, 6, Ambtonia takayasui Tanaka sp. nov. 3a-e: female LV, holotype, Loc. 1-A16, SUM-CO-1253; 4a-c: female RV, paratype, Loc. 1-A16, SUM-CO-1254; 6a-c: male RV, paratype, Loc. 1-A11, SUM-CO-1255. 1-A20, SUM-CO-1257. 7-9, Palmoconcha irizukii Tanaka sp. nov. 5: Falsobuntonia taiwanica Malz, 1982, male LV, Loc. 7a-d: male C, holotype, Loc. 1-A15, SUM-CO-1258; 8a-e: female LV, paratype, Loc. 1-A15, SUM-CO-1259; 9a-c: female RV, paratype, Loc. 1-A15, SUM-CO-1260. Scale bar is 0.10 mm. 18 Gengo Tanaka et al. margin straight. Weak sexual dimorphism. Eye spot not observed. Surface smooth; scattered deep punctations, which are the openings of normal pore canals. Anterior area compressed along the anterior margin. Three weak muri run parallel to posterior margin in the posterior area. In dorsal view, carapace elongately arrowhead-shaped, ta- pered in front. Maximum width about one-fifth length from the posterior end. In anterior view, carapace subpen- tagonal, lateral outline nearly straight. Marginal zone broad in the anterior area, vestibula developed in the anteroventral area and very narrow in the posteroventral area. Marginal pore canals straight, number 39 anteriorly, 6 ventrally and 15 posteriorly. Selvage and list well devel- oped. Hinge hemiamphidont: in LV, anterior element has a large elongate socket; anteromedian element is a smooth elongate tooth, posteromedian element is a crenulate bar; posterior element is an elongate socket with several lobes dorsally. One J-shaped frontal scar. Four elliptical ad- ductor scars in a vertical row, the middle two are narrow. One round mandibular scar. Two dorsal scars protrude like pivots in the dorsomedian area. Fulcral point not observed. One small round ventral scar is below and pos- terior to the mandibular scar. No ocular sinus. Remarks.— This species differs from A. tongassensis Brouwers, 1993 from the Quaternary sediments of the Gulf of Alaska, North America, in its outline in lateral view. Occurrence. — Miocene formations from Japan and Korea (M9d, e, g; see Figure 4). Falsobuntonia taiwanica Malz, 1982 Figure 9.5 Falsobuntonia taiwanica Malz, 1982, p. 392, 393, pl. 8, figs. 51-56; Huh and Paik, 1992a, pl. 2, fig. 15; Huh and Paik, 1992b, p. 111, pl. 2, fig 15; (non) Yajima, 1988, pl. 1, fig. 7; Huh and Paik, 1992b, p. 111, pl. 2, fig. 14. Occurrences.— Miocene to Pleistocene sediments of Japan, Korea and Taiwan (M9d, e and P9e; see Figure 4). Family Loxoconchidae Sars, 1926 Genus Palmoconcha Swain and Gilby, 1974 Palmoconcha irizukü Tanaka sp. nov. Figures 5.10, 9.7-9.9 Palmoconcha sp. Irizuki and Matsubara, 1994, pl. 1, fig. 19. Etymology.—In honor of T. Irizuki (Aichi University of Education, Japan) who is a specialist in the study of Cenozoic fossil ostracod assemblages of Japan. Types.— Holotype, C of male, SUM-CO-1258 (L = 0.47 mm, H = 0.28 mm). Paratypes, LV of female, SUM-CO-1259 (L = 0.49 mm, H = 0.31 mm); RV of female, SUM-CO-1260 (L = 0.46 mm, H = 0.31 mm); LV of female, SUM-CO-1261 (L = 0.51 mm, H = 0.34 mm). Type locality.—Loc. 1-A15. Diagnosis.—Valve rhomboidal. Surface ornamented by punctations in the anterior area. Three concentric muri occur in the anteroventral area, convex ventrally in the mid- ventral area, ends in mid-posterior area. One prominent murus runs from the mid-dorsal area to the posterodorsal area, arched dorsally. One large U-shaped frontal scar. Description.—Valve rhomboidal in lateral view. An- terior margin evenly rounded; dorsal and ventral margins straight in male forms, arched in female forms; posterior margin truncated obliquely in upper half and lower half making blunt angle slightly above mid-height. Strong sex- ual dimorphism; in lateral view, male forms more elongate; in dorsal view, carapaces of female forms inflated in lateral outline. Eye spot not observed. Surface ornamented by punctations in the anterior area, polygonal reticulations and secondary reticulations in the median and posterior areas. Three concentric muri occur in the anteroventral area, convex ventrally in the mid-ventral area, ends at mid- posterior area. One prominent murus runs from the mid- dorsal area to the posterodorsal area, arched dorsally. In dorsal view, carapace ovate, widest at mid-length, pointed at the anterior and posterior ends. In anterior view, cara- pace subovate, broadest a little below mid-height. Marginal zone broad anteriorly and posteriorly, with devel- oped vestibula. Marginal pore canals straight, number 6 anteriorly, 11 ventrally, 6 posteriorly. Selvage and list well developed. Hinge gongylodont: In LV, anterior ele- ment is a downturned claw-shaped ridge around a socket; median element is a smooth bar; posterior element is a horseshoe-shaped socket around a ball-like knob. One large U-shaped frontal scar. Four adductor scars in a ver- tical row (the upper three are elliptical, the lowermost one is semicircular). Two elliptical mandibular scars. Five elliptical dorsomedian dorsal scars. Prominent fulcral point. Remarks.—This species differs from Loxoconcha (Pal- moconcha) parapontica Zhou, 1995 from the Recent sedi- ments of Kumano-nada and Hyuga-nada, southwest Japan, in its anterior marginal outline and punctations in the ante- rior area. P. irizukii is distinguished from P. saboyamensis (Ishizaki, 1966) from the Middle Miocene Hatatate Formation of northeast Japan, in the outline of the anterior margin and the three concentric muri running toward the mid-posterior area. Occurrences. — Middle Miocene sediments, Honshu, Japan (M5a and M9e; see Figure 4). Acknowledgements The authors express their deep gratitude to N. Ikeya, A. Miocene ostracods from Fujina Formation Tsukagoshi (Shizuoka University) and T. Irizuki (Aichi University of Education) for advice and continuous encour- agement throughout the course of the present study. Thanks are also due to R. M. Ross (Paleontological Research Insti- tution, New York), R. J. Smith (Kanazawa University) and K.M. Satish (Shizuoka University) for reading our manu- script. This manuscript was improved by two anonymous referees. We thank K. Tanehira (Shimane), K. Kitakaze (Hiroshima), T. 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Paleontological Research, vol. 6, no. 1, pp. 23-40, April 30, 2002 © by the Palaeontological Society of Japan Stratigraphic and palaeoenvironmental significance of a Pennsylvanian (Upper Carboniferous) palynoflora from the Piaui Formation, Parnaiba Basin, northeastern Brazil RODOLFO DINO' AND GEOFFREY PLAYFORD’ 'Petrobras/Cenpes, Ilha do Fundäo, 21949-900 Rio de Janeiro, Brazil; and Universidade do Estado do Rio de Janeiro (UERJ), Faculdade de Geologia/DEPA, Maracanä, 20559-013 Rio de Janeiro, Brazil (e-mail: dino @ cenpes.petrobras.com.br) "Department of Earth Sciences, The University of Queensland, Brisbane, Australia 4072 (e-mail: g.playford@earth.ug.edu.au) Received 17 September 2001; Revised manuscript accepted 25 November 2001 Abstract. A well-preserved palynoflora is reported from within a cored interval of a coal-exploratory borehole (1-UN-23-PI of the Geological Survey of Brazil) in the southern part of the Parnaiba Basin, north- eastern Brazil. The sample studied is from the lower portion of the Piaui Formation. Its palynoflora is char- acterized by particular abundance of the trilete cavate/pseudosaccate miospores Spelaeotriletes triangulus Neves and Owens, 1966 and S. arenaceus Neves and Owens, 1966, together with cingulizonate forms mainly attributable to Vallatisporites Hacquebard, 1957 and Cristatisporites R. Potonié and Kremp emend. Butter- worth ef al., 1964. Radially and bilaterally symmetrical monosaccate pollen grains are also well-represented, chiefly by Plicatipollenites Lele, 1964 and Potonieisporites Bhardwaj, 1954, respectively. Taeniate grains (i.e., monosaccates and bisaccates) are relatively minor constituents of the palynoflora; no marine microplankton were encountered. Several species are described in detail: the trilete apiculate spores Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivastava, 1969 and Horriditriletes uruguaiensis (Marques-Toigo) Archangelsky and Gamerro, 1979; and the taeniate pollen grains Meristocorpus ostentus sp. nov. and Lahirites segmentatus sp. noy. A Pennsylvanian (Late Carboniferous: late Westphalian) age is adduced for the palynoflora via its correlation with part of the Tapajés Group (specifically, the upper Itaituba Formation) of the Amazonas Basin in northern Brazil. The entirely land-derived palynomorphs, associated with abundant plant debris, corroborate previous suggestions that the lower part of the Piaui Formation accumulated in a nonmarine setting under conditions of aridity. Key words: biostratigraphy, Brazil, Pennsylvanian, palynology, Parnaiba Basin, Piaui Formation Introduction The Carboniferous-Permian rocks of the Palaeozoic ba- sins in north and northeast Brazil provide excellent regional source and reservoir systems for liquid petroleum and gas. Palynology has been applied successfully as a basis for biostratigraphic subdivision of these upper Palaeozoic se- quences, although the carbonate and evaporite intervals therein are normally only sparsely, if at all, palyniferous. In the Parnaiba Basin (Figure 1), the Balsas Group, with the Piauf Formation at its base, comprises these younger Palaeozoic deposits. During the Balsas tectonic-deposi- tional cycle, the Parnaiba Basin experienced conditions of severe aridity, and received predominantly continental de- posits (Cunha, 1986; Lima Filho, 1991). Lithologies are mainly of sandy, evaporitic, and muddy character and clearly reflect strongly oxidizing conditions of deposition. Such factors obviously tend to militate against their palyno- stratigraphic potentialities. Accordingly, only a few paly- nological investigations have been conducted on upper Palaeozoic strata of the Parnaiba Basin. Inferences about age and palaeoenvironment (Müller, 1962) were based on material from exploratory wells drilled by Petrobras. At the beginning of the 1970s, the National Department of Mineral Production (DNPM) initiated research on coal en- countered in several wells drilled close to the basin border, but no biostratigraphic analyses were undertaken. The present study concerns the lower part of the Balsas Group, viz., the Piaui Formation, as intersected in one of the DNPM wells. The aims are to determine the chronostrati- graphic position of the strata, their possible correlation with other Brazilian Palaeozoic basins, and their environment of deposition. The section of the 1-UN-23-PI well, investigated herein, 24 Rodolfo Dino and Geoffrey Playford e Santarem Teresina _e Carolina ae e Floriane i main cities ++* boundary of Parnaiba Basin 555] Piaui Formation outcrop © studied well (1-UN-23-PI) Figure 1. pled for this study. provides the first spore-pollen inventory for the lower part of the Piauf Formation. Obviously, a comprehensive palynological evaluation of the whole formation would necessarily be based on systematic sampling through the vertical extent of the formation, as developed in the subsur- face and in outcrop. As discussed subsequently, the identified spore-pollen assemblage can be compared, for purposes of stratal corre- lation, with those that characterize palynostratigraphic units established elsewhere; particularly the Upper Carboni- ferous-Permian palynozones defined in the Tapajös Group of the Amazonas Basin, northern Brazil (Playford and Dino, 2000b). Palaeoenvironmental implications of the Piaui palynoflora are somewhat limited, and are considered Locality map, Parnaiba Basin, northeastern Brazil, indicating site of borehole (1-UN-23-PI of the Geological Survey of Brazil) sam- in concert with physical evidence advanced by previous workers. Outline of stratigraphy The Parnaiba Basin is essentially a Palaeozoic basin, but includes a cover of younger (Mesozoic and Cenozoic) strata. It is a substantial intracratonic entity, occupying some 600,000 km’ in the western part of Brazil’s northeast- ern region and positioned among fold belts that border the Guaporé, Sao Luiz, and San Francisco cratons. Total stratal thickness is ca. 3500 m, of which 2900 m comprise Palaeo- zoic sediments and the remainder are Mesozoic and Ceno- zoic deposits. The basin’s Palaeozoic succession is divi- Pennsylvanian palynoflora from Brazil 25 sible into three major sedimentary cycles related to different tectonic, structural, and climatic circumstances. In ascending order, these cycles are manifested lithostrati- graphically by what are termed the Serra Grande, Canindé, and Balsas Groups. The initial cycle, of Silurian age, began with the tec- tonic-thermal development of a large depression in which fluvial, deltaic, and shallow marine sediments of the Serra Grande Group accumulated (Cunha, 1986; Goes and Feijö, 1994). With continuing tectonic evolution, the Canindé Group (of the second cycle) was deposited during Devo- nian-Early Carboniferous time. This consists of deltaic and shallow marine to paralic deposits at the base, grading upwards into fluvial-deltaics and periglacials, and culmi- nating with fluvial-deltaic and storm-related deposits. The final (Balsas) Palaeozoic cycle in the basin commenced in the Pennsylvanian and extended through the Permian until earliest Triassic time. It followed pronounced uplift that exposed and eroded much of the Brazilian, indeed South American, platform. Accordingly, the Parnaiba Basin ex- perienced strong erosion, as evidenced by its extensive and well-developed pre-Balsas unconformity. Moreover, the climate changed markedly: from the temperate and humid climates of the preceding cycles to conditions characterized by increasing heat and aridity (Mesner and Wooldridge, 1962, 1964). The sediments of this third phase signify dominantly continental conditions, with occasional marine incursions that became increasingly evaporitic. Piaui Formation The term Piaui was introduced by Small (1914) to desig- nate—as “Série Piauf —the entire Palaeozoic section of the Paraiba Basin. Its application was later restricted (Duarte, 1936) to constitute—as the Piauf Formation—the lowest of four formations that embody the basin’s youngest Palaeozoic sedimentary cycle (Balsas Group). This usage is still widely accepted and is adopted herein. The Piaui Formation is a predominantly clastic sedimentary unit, de- veloped widely in the Parnafba Basin and resting unconformably upon the Canindé Group. The formation crops out in a broad, almost continuous strip along the east- em and southern margins of the basin and discontinuously to the west (Andrade and Daemon, 1974; Suguio and Fulfaro, 1977). Its maximum thickness of ca. 350 m is en- countered in the subsurface. Mesner and Wooldridge (1964) proposed a twofold sub- division of the Piaui Formation. The lower part consists of pink to red sandstone; the upper part comprises alternating green and red shales, thin anhydrite beds, pink dolomite, and red or pale grey carbonate beds containing marine fos- sils. Lima Filho (1991), while maintaining the binary sub- division, modified slightly the Piauf Formation’s limits. He recognized several depositional systems in the forma- tion, in particular citing evidence of aeolian and deltaic sedimentation and, towards the top, an episode of shallow marine, carbonate deposition. Accordingly, Lima Filho (1991) concluded that the Piaui Formation accumulated under arid conditions in a setting that included an extensive interior desert and an evaporitic marine basin. The Piaui Formation consists chiefly of continental redbeds, aeolian sandstones, and fluvial deposits. How- ever, brief marine incursions are attested by the presence of richly fossiliferous carbonate platform or lagoonal sedi- ments, particularly in the formation’s upper part as devel- oped in the basin’s northeastern sector. Known locally by such names as Mocambo, Contendas, Meruoca, Carima, Vidalgo, and Boa Esperanga, these marine strata become increasingly evaporitic upsection, providing evidence of progressive aridity. The marine faunas, though mostly undescribed, are diverse. They include bivalves, gastro- pods, cephalopods, brachiopods, trilobites, bryozoans, and echinoderms (crinoids especially), together with conodonts, agglutinated and calcareous Foraminifera, ostracodes, micro-molluscs, and other microfossils (see Duarte, 1936; Kegel, 1951; Kegel and Costa, 1951; Mesner and Woold- ridge, 1964; Campanha and Rocha Campos, 1979; Assis, 1980). Faunal affinities between the Piaui Formation and the Itaituba Formation of the Amazonas Basin - as noted by such authors as Mendes (1966), Tengan er al. (1976), Campanha and Rocha Campos (1979), and Assis (1980) - support the hypothesis of a marine connection between the Parnaiba and Amazonas Basins during Pennsylvanian time. Material and methods This study is based on material from a continuously cored well designated as 1-UN-23-PI and located in the state of Piaui, municipal district of Antonio Almeida, at latitude 7° 15° 18° South, longitude 44° 12° 24°° West, in the southern Parnaiba Basin (Figure 1). Three samples were collected from the depth interval 137.6-145.8 m, rep- resentative of the top of the Piauf Formation’s lower por- tion (Figure 2). Of these samples, only one (a grey silt- stone, at 145.0 m) proved palyniferous, yielding an abundant and well-preserved palynoflora. The two unpro- ductive samples, collected at depths of 137.6 m and 145.8 m, are both greenish grey shales. Conventional physico-chemical methods were applied in the laboratory preparation of the samples, specifically those outlined in Playford and Dino (2000a, p. 10-12). Light- microscope photographs of palynomorphs were taken with a Zeiss MC 80 DX camera coupled with a Zeiss Axioplan microscope using Kodak T-Max (100 ASA) film. Scan- ning electron microscopy assisted in the identification of several species. 26 Rodolfo Dino and Geoffrey Playford 1-UN-23-PI &: 137.6-¢ Piaui Formation (part) 145.0 145.8 shale sandstone === mudstone e sample depth (m) Figure 2. Portion of 1-UN-23-PI litholog showing palyno- logically sampled interval of Piaui Formation. Composition of palynoflora The palynoflora recovered from the productive Piaui sample is dominated by pteridophytic trilete spores and gymnospermous monosaccate pollen grains occurring in al- most equal proportions (each accounting for ca. 45% of the total assemblage). Taeniate bisaccate grains are relatively minor constituents (ca. 7%). In addition, fresh or brackish water green algae (Botryococcus, Brazilea) have been re- covered. No palaeomicroplanktic elements were encoun- tered. Given below is an inventory of all palynomorph taxa identified. The large majority of these are illustrated by light micrographs (Figures 3, 5-8) and a few also by scan- ning electron micrographs (Figures 4, 9). In the system- atic section, four species (asterisked hereunder) are described in detail, and brief notes are appended on dis- crimination of the two Spelaeotriletes species encountered. Illustrated specimens are listed in relevant figure captions with slide number followed by microscope-stage coordi- nates (per standard “England Finder” slide). Permanent repository of the specimens is Petrobras/Cenpes/Divex/ Sebipe, Cidade Universitaria, Quadra 7, Ilha do Fundäo, 21949-900 Rio de Janeiro, RJ, Brazil. Spores Anteturma Proximegerminantes R. Potonié, 1970 Turma Triletes Reinsch emend. Dettmann, 1963 Suprasubturma Acavatitriletes Dettmann, 1963 Subturma Azonotriletes Luber emend. Dettmann, 1963 Infraturma Laevigati Bennie and Kidston emend. R. Potonié, 1956 Leiotriletes sp. [Figure 3.7] Calamospora sp. cf. C. sinuosa Leschik, 1955 [Figure Sell] Punctatisporites gretensis Balme and Hennelly, 1956 [Figure 3.5] Punctatisporites sp. [Figure 3.6] Infraturma Apiculati Bennie and Kidston emend. R. Potonié, 1956 Subinfraturma Granulati Dybova and Jachowicz, 1957 Granulatisporites austroamericanus Archangelsky and Gamerro, 1979 [Figures 3.2, 3.3, 4.1] Cyclogranisporites minutus Bhardwaj, 1957 [Figure 3.4] Subinfraturma Nodati Dybovä and Jachowicz, 1957 “Acanthotriletes” menendezii Gonzales-Amicon, 1973 [Figure 3.8] "Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivastava, 1969 [Figure 3.9] Subinfraturma Baculati Dybovä and Jachowicz, 1957 Horriditriletes ramosus (Balme and Hennelly) Bharad- waj and Salujha, 1964 [Figures 3.11, 4.2] “Horriditriletes uruguaiensis (Marques-Toigo) Archan- gelsky and Gamerro, 1979 [Figures 3.10, 4.3, 4.4] Baculatisporites sp. Raistrickia cephalata Bharadwaj, Kar, and Navale, 1976 [Figures 3.12, 9.3] Raistrickia sp. cf. R. saetosa (Loose) Schopf, Wilson, and Bentall, 1944 [Figure 3.13] Raistrickia sp. Subinfraturma Verrucati Dybova and Jachowicz, 1957 = Figure 3. Y45/2; 3, x750, 20005916/3, R51. M49/2. 6. Punctatisporites sp., x500, 20005916D, PSS. 20005916D, H39. 9. Brevitriletes levis, «750, 20005916/1, A64/3. triletes ramosus, x500, 20005916D, W48/3. 20005916/1, B57. 1. Calamospora sp. cf. C. sinuosa, x500, 20005916E, K/42. 4. Cyclogranisporites minutus, x750, 20005916D, M36/3. 7. Leiotriletes sp., x750, 20005916B, N39/2. 10. Horriditriletes uruguaiensis, x1000, 20005916D, 038/1. 12. Raistrickia cephalata, x750, 20005916E, V50/3. 14. Verrucosisporites sp. cf. V. morulatus, x750, 20005916/2, U66. 2, 3. Granulatisporites austroamericanus; 2, x750, 20005916/3, 5. Punctatisporites gretensis, x750, 20005916E, 8. “Acanthotriletes” menendezii, x1000, 11. Horridi- 13. Raistrickia sp. cf. R. saetosa, x750, Pennsylvanian palynoflora from Brazil Verrucosisporites andersonii Backhouse, 1988 [Figure 3-1,.3:2] Verrucosisporites sp. cf. V. morulatus (Knox) Smith and Butterworth, 1967 [Figure 3.14] Suprasubturma Laminatitriletes Smith and 1967 Butterworth, 28 Rodolfo Dino and Geoffrey Playford Figure 4. 1. Granulatisporites austroamericanus, «1900, 20005916/S1, S41/2. 2. Horriditriletes ramosus, x2000, 20005916/S1, S42. 3, 4. Horriditriletes uruguayensis; 3, x1900, 20005916/S1, Q41; 4, x2300, 20005916/S1, N39. Subturma Zonolaminatitriletes Smith and Butterworth, 1967 Infraturma Cingulicavati Smith and Butterworth, 1967 Vallatisporites arcuatus (Marques-Toigo) Archangelsky and Gamerro, 1979 [Figure 5.3] Vallatisporites russoi Archangelsky and Gamerro, 1979 [Figure 5.4] Vallatisporites sp. 1 [Figure 5.5] Vallatisporites sp. 2 [Figure 5.6] Vallatisporites sp. 3 [Figure 5.7] Cristatisporites inconstans Archangelsky and Gamerro, 1979 [Figure 5.10] Pennsylvanian palynoflora from Brazil 29 Suprasubturma Pseudosaccititriletes Richardson, 1965 Infraturma Monopseudosacciti Smith and Butterworth, 1967 Spelaeotriletes arenaceus Neves and Owens, 1966 [Figure 5.9] Spelaeotriletes triangulus Neves and Owens, 1966 [Figure 5.8] Turma Monoletes Ibrahim, 1933 Suprasubturma Acavatomonoletes Dettmann, 1963 Subturma Azonomonoletes Luber, 1935 Infraturma Laevigatomonoleti Dybovä and Jachowicz, 1957 Laevigatosporites vulgaris (Ibrahim) Ibrahim, [Figure 5.11] Infraturma Sculptatomonoleti Dybovä and Jachowicz, 1957 Striatosporites heyleri (Doubinger) emend. and Dino, 2000a [Figure 5.12] 1933 Playford Pollen grains Anteturma Variegerminantes R. Potonié, 1970 Turma Saccites Erdtman, 1947 Subturma Monosaccites Chitaley emend. and Kremp, 1954 Infraturma Aletesacciti Leschik, 1955 Florinites occultus Habib, 1966 [Figure 6.10] Florinites sp. [Figure 5.13] Infraturma Vesiculomonoraditi Pant, 1954 Potonieisporites brasiliensis (Nahuys, Alpern, and Ybert) emend. Archangelsky and Gamerro, 1979 [Figure 6.5] Potonieisporites densus Maheshwari, 1967 [Figure 6.11] Potonieisporites elegans (Wilson and Kosanke) Wilson and Venkatachala emend. Habib, 1966 [Figure 6.3] Potonieisporites neglectus Potonié and Lele, 1961 Potonieisporites novicus Bhardwaj, 1954 [Figure 6.2] Potonieisporites ovatus (Kar) Gutiérrez, 1993 [Figure 6.9] Potonieisporites simplex Wilson, 1962 [Figure 6.1] Potonieisporites triangulatus Tiwari, 1965 [Figure 6.8] Potonieisporites sp. [Figure 7.4] Peppersites ellipticus Ravn, 1979 [Figure 6.7] Caheniasaccites ovatus Bose and Kar emend. érrez, 1993 Costatascyclus crenatus Felix and Burbridge emend. Urban, 1971 [Figure 6.4] Infraturma Triletesacciti Leschik 1955 Cannanoropollis densus (Lele) Bose and Maheshwari, 1968 [Figure 7.5] Cannanoropollis korbaensis (Bharadwaj and Tiwari) Foster, 1975 [Figure 6.6] Plicatipollenites gondwanensis (Balme and Hennelly) Lele, 1964 [Figure 7.6] R. Potonié Guti- Plicatipollenites trigonalis Lele, 1964 Infraturma Striasacciti Bharadwaj, 1962 Striomonosaccites ovatus Bharadwaj, 1962 [Figures 7.9, 9 Meristocorpus explicatus Playford and Dino, 2000 [Figure 8.6] "Meristocorpus ostentus sp. nov. [Figure 7.1-7.3] Subturma Disaccites Cookson, 1947 Infraturma Disaccitrileti Leschik, 1955 Limitisporites sp. Infraturma Striatiti Pant, 1954 Illinites unicus Kosanke, 1950 [Figure 7.7] Protohaploxypinus amplus (Balme and Hennelly) Hart, 1964 [Figure 8.4] Protohaploxypinus bharadwajii Foster, 1979 [Figures 7.8, 8.3] Protohaploxypinus sp. cf. Striatopodocarpites magni- ficus Bharadwaj and Salujha, 1964 [Figure 8.5] Striatopodocarpites sp. cf. S. phaleratus (Balme and Hennelly) Hart, 1964 [Figure 7.10] Striatoabieites sp. cf. S. anaverrucosus Archangelsky and Gamerro, 1979 [Figure 8.7] Taeniaesporites sp. [Figure 8.8] “Lahirites segmentatus sp. nov. [Figures 8.1, 8.2, 9.2, 9.4] Striatopodocarpites sp. [Figure 8.9] Turma Plicates Naumova emend. R. Potonié, 1960 Subturma Monocolpates Iversen and Troels-Smith, 1950 Cycadopites sp. Sculptured monocolpate form indet. [Figure 7.12] Green algae (division Chlorophyta) Class Chlorophyceae, order Chlorococcales Botryococcus braunii Kützing, 1849 Class Zygnemaphyceae Brazilea scissa (Balme and Hennelly) Foster, 1975 [Figure 7.11] Systematic palaeontology Genus Brevitriletes Bharadwaj and Srivastava, 1969 Type species.— Brevitriletes communis Bharadwaj and Srivastava, 1969; by original designation. Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivastava, 1969 Figure 3.9 Apiculatisporites levis Balme and Hennelly, 1956, p. 246-247, pl. 2, figs. 19-21. Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivas- tava, 1969, p. 226-227, pl. 1, figs. 17-20. Rodolfo Dino and Geoffrey Playford 30 Pennsylvanian palynoflora from Brazil 31 Anapiculatisporites ? variornatus Menéndez and Azcuy, 1969, p. 88, 90; pl. 3, figs. A-H. Apiculiretusispora variornata (Menéndez and Azcuy) Menéndez and Azcuy, 1971, p. 28. Retusotriletes baculiferus Ybert, 1975, p. 186, pl. 1, figs. 21-23. non Apiculatisporis [sic] levis Balme and Hennelly; Cesari, Archangelsky, and Seoane, 1995, p. 78; pl. 1, fig. 2. For further synonymy see Foster (1979, p. 35). Description.—Spores radial, trilete. Amb circular, sub- circular, or very broadly rounded subtriangular. Laesurae distinct, straight, extending almost to equatorial periphery; simple or accompanied by narrow and somewhat irregular lips; frequently terminating in + distinct curvaturae imper- fectae. Exine 1.5-2 um thick, sculptured distally and equatorially with small, discrete, apiculate elements com- prising spinae, coni, and galeae, 1.2-2.5 um long (usually ca. 1.5-2 um), 0.5-2 um in basal diameter, spaced 0.5-2 um apart. Proximal surface laevigate or very sparsely and finely spinose/conate; sometimes polumbrate, with thick- ened (darkened) interradii emphasizing contact areas or parts thereof. Dimensions (25 specimens).—Equatorial diameter, ex- cluding sculptural projections, 22 (30) 37 m. Remarks and comparison.—The specimens described above are in close accord with those described originally (Balme and Hennelly, 1956) and subsequently (Backhouse, 1991, 1993) from the Collie Coal Measures (Permian) of southwestern Australia, and also with Foster’s (1979) mate- rial from Permian strata of the Bowen Basin, Queensland. In degraded specimens, the apiculate sculptural projections tend to exhibit decapitate or otherwise blunted termini and may thus resemble bacula. In terms of coarseness of sculpture, a morphological continuum exists among speci- mens belonging to Brevitriletes levis (Balme and Hennelly) Bharadwaj and Srivastava, 1969 (cf. Backhouse, 1991, p. 263). Ybert’s (1975) photomicrographs of his species Retuso- triletes baculiferus leave no doubt as to its synonymy with Brevitriletes levis. The same is considered applicable to Apiculiretusispora variornata (Menéndez and Azcuy) Menéndez and Azcuy, 1971; see also Césari and Gutiérrez (2001, pl. 2, fig. 6). A specimen recorded by Césari et al. (1995, see above synonymy) as Apiculatisporis (sic) levis differs from the latter in having sparser, essentially rod-like sculpturing elements. Previous records. —Known widely from the uppermost Carboniferous and Permian of Gondwana. South Ameri- can reports include those from Argentina (Menéndez and Azcuy, 1969, 1971; Mautino er al., 1998; Vergel, 1998; Césari and Gutiérrez, 2001) and Brazil (Ybert, 1975; Burjack, 1978; Marques-Toigo, 1988). Genus Horriditriletes Bharadwaj and Salujha, 1964 Type species.— Horriditriletes curvibaculosus Bharad- waj and Salujha, 1964; by original designation. Discussion.—Foster (1979, p. 38) has clarified the diag- noses and differential diagnoses of Horriditriletes Bharadwaj and Salujha, 1964 and its type species. Horriditriletes uruguaiensis (Marques-Toigo) Archangelsky and Gamerro, 1979 Figures 3.10, 4.3, 4.4 Neoraistrickia uruguaiensis Marques-Toigo, 1974, p. 604, pl. 1, figs. 4, 5. Neoraistrickia baculicapillosa Pons, 1976, p. 120-121, pl. 2, figs. 14-16. Horriditriletes uruguaiensis (Marques-Toigo) Archangelsky and Gamerro, 1979, p. 424-426. Description.—Spores radial, trilete. Amb subtriangular with straight or slightly concave sides and broadly rounded apices. Laesurae more or less distinct, straight, extending at least three-quarters of distance to equator, infrequently with narrow lip development. Exine 1-1.8 um thick, sculptured irregularly and heterogeneously with bacula (mainly), associated with verrucae, coni, spinae, and clavae of similar dimensions. Sculptural elements discrete and developed comprehensively, but more conspicuous distally and equatorially; length usually 1-4 um, bases 0.8-2.5 um in diameter and spaced 0.5-6 um apart. Dimensions (20 specimens).—Equatorial diameter, ex- cluding sculptural projections, 33 (43) 60 um. Comparison. — Horriditriletes uruguaiensis (Marques- Toigo) Archangelsky and Gamerro, 1979 is distinguished from the type species (see Bharadwaj and Salujha, 1964, p. 193-194, pl. 2, figs. 34-39) by its larger size and more densely distributed sculpture; and from H. ramosus (Balme and Hennelly) Bharadwaj and Salujha, 1964, which has more uniformly baculate sculpture and subtriangular amb typically with slightly convex sides (Balme and Hennelly, 1956, p. 249, pl. 3, figs. 39-41). “ Figure5. 1,2. Verrucosisporites andersonii, 1, 750, 20005916/3, A49; 2, x750, 20005916/3, A47. 3, Vallatisporites arcuatus, x500, 20005916/3, D39. 4, Vallatisporites russoi, x750, 20005916/3, C54. 5, Vallatisporites sp. 1, x500, 20005916D, R39/3. 7, Vallatisporites sp. 3, x500, 20005916D, E50. 10, Cristatisporites inconstans, x500, 20005916D, D48/4. x500, 20005916D, 036/4. Spelaeotriletes arenaceus, x750, 20005916D, 044. 750, 20005916E, H37/2. 12, Striatosporites heyleri, «500, 20005916D, S52. 6, Vallatisporites sp. 2, 8, Spelaeotriletes triangulus, x750, 20005916D, F48/4. 9, 11, Laevigatosporites vulgaris, x 13, Florinites sp., x500, 20005916D, S57. 32 Rodolfo Dino and Geoffrey Playford Pennsylvanian palynoflora from Brazil 33 Previous records. — Originally described (Marques- Toigo, 1974) from the Lower Permian of Uruguay, Horri- ditriletes uruguaiensis has been recorded subsequently in rocks of similar age from there and from Brazil and Argentina (e.g.. Pons, 1976; Archangelsky and Gamerro, 1979; Marques-Toigo, 1988; Beri and Goso, 1996; Dias, 1994; Césari et al., 1995; Beri and Aguilar, 1998; Vergel, 1998). According to Césari and Gutiérrez (2001), this spe- cies occurs in the Upper Carboniferous-Lower Permian in- terval of central western Argentina. Genus Spelaeotriletes Neves and Owens, 1966 Type species. — Spelaeotriletes triangulus Neves and Owens, 1966; by original designation. Discussion.— Playford et al. (2001) have provided a comprehensive review of Spelaeotriletes Neves and Owens, 1966 in terms of its diagnosis, differential diagno- sis, and Gondwanan representation. Spelaeotriletes is represented commonly in the Piauf palynoflora by two species that were instituted concurrently by Neves and Owens (1966) and share very similar mor- phological attributes; viz., the type species S. triangulus (Figure 5.8) and S. arenaceus (Figure 5.9). Both species were described in detail by Playford and Dino (2000a, p. 21-22, pl. 5, figs. 1-7; pl. 6, figs. 5, 6) on the basis of nu- merous well-preserved specimens they encountered in the Pennsylvanian portion of the upper Palaeozoic Tapajös Group, Amazonas Basin. The difficulties that may arise in satisfactorily separating these species from each other have been discussed by Playford and Dino (2000a) and Playford et al. (2001); see also Spinner and Clayton (1973, p. 161), Playford and Powis (1979, p. 391), and Ravn and Fitz- gerald (1982, p. 144). Pending re-examination of the re- spective type specimens of S. triangulus and S. arenaceus, and study of possible topotype material, the species are here distinguished - albeit somewhat provisionally as, for instance, in Playford er al. (2001)— in accordance with Neves and Owens’s (1966, p. 345-346) original criteria (principally sculptural). These are that the exoexine (i.e., outside of the virtually laevigate contact faces) bears sculp- turing elements that are generally coarser and more densely and regularly distributed in S. triangulus than in S. arenaceus. Previous records.—S. arenaceus and S. triangulus have been reported widely, either individually or as a single merged specific entity, from upper Palaeozoic (more par- ticularly, lower-middle Pennsylvanian) strata of both north- ern and southern hemispheres (Playford and Dino, 2000a, p21): Genus Meristocorpus Playford and Dino, 2000b Type species.—Meristocorpus explicatus Playford and Dino, 2000b; by original designation (monotypic). Meristocorpus ostentus sp. nov. Figure 7.1-7.3 Meristocorpus sp. C of Playford and Dino, 2000b, p. 100, pl. 4, figs. 1, 2. Diagnosis. — Pollen grains bilateral, monosaccate, taeniate, monolete. Amb transversely oval to elongate, ends rounded. Laesura distinct to perceptible, straight or somewhat curved, length variable. Outline of corpus (in polar view) similar to amb, exine 1-1.5 um thick; proximal surface bearing 5-12 subparallel taeniae, mostly continu- ous, infrequently bifurcating, each 3-8 um wide, with inter- vening clefts 0.5-1.5 um wide. A pair of straight to broadly curved folds developed marginally across corpus and marking saccus attachments thereto. Saccus relatively narrow where adjoining transverse sides of corpus, with greatest development about longitudinal sides (“ends”) of corpus; fine to medium endoreticulum evident in well- preserved specimens. Dimensions (19 specimens, in polar aspect). — Overall breadth 82 (92) 110 um; overall length 34 (48) 65 um. Corpus breadth 55 (70) 82 um; corpus length 27 (43) 60 um. Holotype.—Slide 20005916/3, S38/1; Figure 7.3. Proxi- mal aspect. Amb transversely elongate-oval; overall leng- th 47 um, width 88 um; corpus well-defined, 43 um long, 72 um wide, outline closely conforming with amb, proxi- mal face modified by 7 subparallel transverse taeniae ex- tending for full corpus breadth, some bifurcation but mainly continuity; longitudinal corpus margins with promi- nent, straight to outwardly convex folds; maximum sacci development about corpus ends; sacci with fine endore- ticulation; laesura perceptible, slightly curved, length 13 um. Type locality.—Brazil, Parnaiba Basin, Piauf Formation; 1-UN-23-PI well, core, 145.0 m. Etymology.— From the Latin, ostentus, stretched out. @ Figure 6. 1. Potonieisporites simplex, x500, 20005916C, P34/1. 2. Potonieisporites novicus, x500, 20005916C, G34/4. 3. Potonieisporites elegans, x500, 20005916C, D44/3. M37/4. 6. Cannanoropollis korbaensis, x500, 20005916C, D39/4. Potonieisporites densus, x500, 20005916/3, C48/4. 4. Costatascyclus crenatus, x500, 20005916/3, T57/3. 7. Peppersites ellipticus, x500, 20005916C, A39/2. triangulatus, x500, 20005916C, J41/2. 9. Potonieisporites ovatus, x500, 20005916B, T41/4. 5. Potonieisporites brasiliensis, x750, 20005916A, 8. Potonieisporites 10. Florinites occultus, x500, 20005916/2, U66. 11. 34 Rodolfo Dino and Geoffrey Playford Figure 7. 1-3. Meristocorpus ostentus sp. nov.; 1, x750, 20005916/3, G50/3; 2, x500, 20005916B, O40/3; 3, holotype, x500, 20005916/3, S38/1. 4. Potonieisporites sp., x500, 20005916D, G33/3. 5. Cannanoropollis densus, x500, 20005916D, M33. 6. Plicatipollenites gondwanensis, x500, 20005916F, P35/1. 7. Illinites unicus, x500, 20005916D, x50/3. 8. Protohaploxypinus bharadwajii, x500, 20005916/2, P57/3. 9. Strio- monosaccites ovatus, x500, 20005916E, N/37. 10. Striatopodocarpites sp. cf. S. phaleratus, x500, 20005916C, F33/1. 11. Brazilea scissa, x750, 20005916/3, K46/2. 12. Sculptured monocolpate form indet., x500, 20005916F, S44. Remarks.—The identification herein of well-preserved (2000b), enables its formal establishment as a new species. specimens of this distinctive form, additional to those re- Meristocorpus ostentus sp. nov. is distinguished from other ported and designated informally by Playford and Dino forms assigned to the genus mainly by the very prominent Ww un Pennsylvanian palynoflora from Brazil Figure 8. 1,2. Lahirites segmentatus sp. nov.; 1, holotype, x750, 20005916A, M58/2; 2, x500, 20005916A, E39. 3. Protohaploxypinus bharadwajii, x500, 20005916F, D48/1. 4. Protohaploxypinus amplus, x750, 20005916/3, C48/2. 5. Protohaploxypinus sp. cf. Striatopodocarpites magnificus, #500, 20005916C, A39/4. 6. Meristocorpus explicatus, «500, 20005916A, N39/3. 7. Striatoabieites sp. cf. S. anaverrucosus, x500, 20005916C, D35/3. 8. Taeniaesporites sp., x500, 20005916C, D34/4. 9. Striatopodocarpites sp., x500, 20005916/3, D41/4. 36 Rodolfo Dino and Geoffrey Playford Figure 9. 1. Striomonosaccites ovatus, x1200, 20005916/S2, N39. 2, 4. Lahirites segmentatus sp. nov., 2, x800, 20005916/S2, N40/4; 4, x675, 20005916/S2, N55/4. 3. Raistrickia cephalata, «1500, 20005916/S2, P57/3. elongation of its corpus and by relative proportions of the Genus Lahirites Bharadwaj, 1962 corpus and sacci. Previous records. — From the Itaituba Formation, Type species. —Lahirites raniganjensis Bharadwaj, 1962; Amazonas Basin: Illinites unicus Zone, Westphalian C by original designation (monotypic). (Playford and Dino, 2000b). Discussion.—The salient attributes of Lahirites Bharad- waj, 1962, as exemplified by its type species, are circular Pennsylvanian palynoflora from Brazil 37 corpus bearing nine proximal transverse (“horizontal”) taeniae that have a relatively coarse, segmented (“brick- work-like”) appearance resulting from fine (“vertical”), lin- ear, intra-taeniate channels cross-connecting the clefts bounding adjacent taeniae. The well-developed, protru- sive sacci impart a distinctly diploxylonoid appearance. As discussed by Playford and Dino (2000b, p. 111), the three genera Lahirites, Verticipollenites, and Hindipolleni- tes, as established by Bharadwaj (1962), have sufficient common features to render their mutual segregation prob- lematical. Our choice of Lahirites as generic repository for the species newly described below is based mainly on its closer similarity to L. raniganjensis Bharadwaj, 1962 than to the type species of either of the other genera. Lahirites segmentatus sp. nov. Figures 8.1, 8.2, 9.2, 9.4 Diagnosis.— Pollen grains bisaccate, taeniate, strongly diploxylonoid. Corpus circular or near-circular with slight longitudinal elongation (polar orientation); exine 2-3 um thick, infragranulate. Cappa comprising 7-12 transverse taeniae that are continuous or, more commonly, irregularly furcant. Taeniae 7-10 um wide, separated by fine clefts 1-2 um wide; taeniae divided irregularly into broadly rec- tangular segments by fine channels disposed normally to inter-taeniate clefts, thus producing a brickwork-like nega- tive reticulum. Cappula narrowly rectangular. Sacci > semicircular, with medium to coarse endoreticulum, distal attachment roots producing longitudinal folds near corpus borders. Dimensions (16 specimens, in polar aspect). — Overall breadth 110 (135) 150 um; overall length 63 (89) 105 um. Corpus breadth 35 (55) 65 um; corpus length 50 (62) 75 um. Holotype.—Slide 20005916A, M58/2; Figure 8.1. Proxi- mal aspect. Strongly diploxylonoid; overall breadth 150 um, overall length 97 um; corpus subcircular with slight longitudinal elongation (64 um x 75 um), exine 2 um thick, featuring transverse, bifurcating taeniae, 7-10 um wide, separated by fine clefts and incised (approximately at right angles to the latter) by very narrow, irregular, and less dis- tinct channels; cappula 23 um x 75 um; sacci > semicircu- lar, breadth 73 um, length 97 um, with medium-coarse endoreticulum. Type locality.—Brazil, Parnaiba Basin, Piaui Formation; 1-UN-23-PI well, core, 145.0 m. Etymology.—From the Latin, segmentum, partition, seg- ment. Comparison. — Certain Indian Permian species of Lahirites warrant comparison with L. segmentatus sp. nov. These species, with their principal morphological distinc- tions from L. segmentatus, are as follows: L. raniganjensis Bharadwaj, 1962 (p. 92, pl. 13, fig. 172), taeniae non- furcant; L. singularis Bharadwaj and Salujha, 1964 (p. 204-205, pl. 8, figs. 119-121), generally smaller, corpus thin-walled but with distinct marginal ridge, non-furcant taeniae; and L. rotundus Bharadwaj and Salujha, 1964 (p. 205-206, pl. 8, fig. 125; pl. 9, figs. 126, 127), corpus with non-furcant taeniae and “laterally prominent marginal ridge”. Correlation and age of palynoflora Many of the palynomorphs in the present assemblage are identifiable with taxa that are known to have relatively broad stratigraphic ranges within the upper Palaeozoic of South America, and hence do not assist in definitive dating and correlation of the subject stratum. However, certain of the more vertically restricted species can usefully be ap- plied biostratigraphically. These include the following: Raistrickia cephalata, Vallatisporites arcuatus, Cristati- sporites inconstans, Spelaeotriletes arenaceus, S. triangul- us, Striatosporites heyleri, Peppersites ellipticus, Illinites unicus, and Meristocorpus explicatus. All have been documented previously from the upper Palaeozoic of Brazil (Amazonas Basin principally: Playford and Dino, 2000a, b) and/or of Argentina (e.g., Archangelsky and Gamerro, 1979, Archangelsky et al., 1996, Césari and Gutiérrez, 2001). Müller’s (1962) palynostratigraphic study included analysis of the Piaui Formation as cored in 15 oil explora- tion wells in the Parnaiba Basin (then termed Maranhäo Basin). He recognized, in descending order, zones K, L, and M, covering the Piaui and the overlying Pedro de Fogo Formation and, supposedly (and, we believe, mistakenly), part of the underlying Poti Formation. The zones cannot be regarded, on present standards, as rigorously defined biostratigraphic units; they were ascribed generally to the Pennsylvanian (Westphalian-Stephanian). Zones L-M, represented by the Piaui Formation, include some forms en- countered in the present sample; i.e., Cristatisporites inconstans (Müller’s “Tl-2-I), Vallatisporites arcuatus (“TI-2-e”); Verrucosisporites sp. cf. morulatus (“Tl-r-b”), Raistrickia cephalata (“Raistr-a”), Protohaploxypinus bharadwajii (“V-D-i/st-al”), and possibly Spelaeotriletes sp. (“Tl-z-b”). Accordingly, the sample studied here is compatible with zones L-M (more particularly, the latter) of Müller (1962). With regard to the Amazonas Basin, no really precise equivalence of the present assemblage can be established vis-a-vis the Playford and Dino (2000b) palynozonation of the upper Palaeozoic Tapajés Group. This may well be a consequence of the current study being based on only one, fortuitously productive sample from within an otherwise non-palyniferous Piaui interval. Moreover, very little is 38 Rodolfo Dino and Geoffrey Playford known of the Parnaiba Basin’s overall Carboniferous- Permian palynological sequence. Species considered to be stratigraphically significant in the Tapajös Group, and oc- curring also in the Piaui sample, include Illinites unicus, Striatosporites heyleri, and Raistrickia cephalata. Prima facie, therefore, the Piaui assemblage could be regarded as falling somewhere within the Amazonas zonal interval de- fined eponymously and collectively by these three species. However, viewed in more detail, it should be noted that both S. heyleri and R. cephalata are represented very spar- ingly, by only one or two specimens, in contrast to their re- spective zonal abundances in the Amazonas Basin. Correlation with the Illinites unicus Zone (Playford and Dino, 2000b, p. 120-121) appears most likely from the pre- sence of /. unicus in association with Meristocorpus explicatus and M. ostentus and with plentiful Spelaeo- triletes triangulus, S. arenaceus, and zonate-cingulizonate forms (Vallatisporites, Cristatisporites). Additional sup- port for this zonal correlation is provided by the scant rep- resentation of taeniate bisaccate pollen grains (which become increasing prevalent in post-/. unicus palyno- zones). The Illinites unicus Zone embraces the upper part of the Itaituba Formation, directly beneath the Nova Olinda Formation, in the Tapajös Group succession of the Amazonas Basin. Hence, zonal attribution of the study sample signifies correlation of at least the subject Piaui stratum with the upper Itaituba Formation. This effec- tively corroborates other palaeontological evidence (previ- ously cited herein) of faunal affinities between the Itaituba and Piaui Formations, and strengthens the lithostratigraphic correlation between these two formations that was origi- nally advanced by Mesner and Wooldridge (1964). It fol- lows that the upper part of the lower Piaui Formation can be ascribed a mid Pennsylvanian (late Westphalian) age (Playford and Dino, 2000b, p. 131). Correlation of the present Piauf sample with the Argentinian palynozonation cannot be effected in any satis- factory way owing to the very generalized characteristics promulgated for those zones (Césari and Gutiérrez, 2001, p. 133). The best that can be said is that the Piaui suite would be attributable to the zones DMb or DMc. Palaeoenvironmental inferences As discussed previously, sedimentological and palaeon- tological studies indicate an interplay of several environ- mental circumstances or settings nonmarine, paralic, marine, evaporitic during accumulation of the Piaui Forma- tion. Many lines of evidence, including data from core de- scriptions, well logs, remote sensing, lithofacies analyses, and sedimentary petrography, point to the lower part of the formation being predominantly nonmarine and reflecting conditions of aridity. In the studied sample, the abundant land-derived plant debris in association with wholly terrestrial palynomorphs surely attest to nonmarine conditions. Moreover, the prevalence of monosaccate pollen grains, produced by cordaitalean gymnosperms, suggest arid climatic condi- tions. Regarding the green algal palynomorphs, the pres- ence of Botryococcus permits no unequivocal palaeoen- vironmental inferences (e.g., Batten and Grenfell, 1996, p. 210), other than indicating a quiescent aquatic situation; but Brazilea is suggestive of an exclusively freshwater habitat (Colbath and Grenfell, 1995). Conclusions 1. The spore-pollen palynoflora recovered from the sin- gle productive sample, representing the upper part of the lower Piaui Formation in the southern Parnaiba Basin, comprises pteridophytic trilete spores associated with a range of gymnospermous pollen grains, principally monosaccates. Taeniate bisaccates are relatively uncom- mon. 2. In biostratigraphic terms, the assemblage bears closest similarity to the //linites unicus palynozone of the Tapajös succession in the Amazonas Basin. 3. The zonal attribution connotes correlation of the palyniferous Piaui stratum with the upper part of the Itaituba Formation of the Tapajös Group, and dating of the stratum as mid Pennsylvanian (late Westphalian). 4. Such palaeoenvironmental indications that can be gleaned from the palynoflora corroborate the sedimento- logical, geophysical, and other prior data that imply a nonmarine depositional situation under arid conditions. Acknowledgements Sincere appreciation is expressed to the following: Alarico A.F. Mont’ Alverne, Chief Geologist of the 4th District of DNPM, in Recife, for granting permission for this study and for facilitating sample collection; Dra. Luzia Antonioli, of Petrobras/Cenpes and Universidade Federal do Rio de Janeiro, for assistance in technical mat- ters; and Professor Geoffrey Clayton (Trinity College, University of Dublin) and another (anonymous) reviewer for their helpful comments on the manuscript. 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Paleontological Research, vol. 6, no. 1, pp. 41-65, April 30, 2002 © by the Palaeontological Society of Japan Indian metoposaurid amphibians revised DHURJATI PRASAD SENGUPTA Indian Statistical Institute, Geological Studies Unit 203 Barrackpore Trunk Road, Calcutta 700035, India (dhurjati@ isical.ac.in) Received 18 August 2000; Revised manuscript accepted 30 November 2001 Abstract. A recent collection of more than a hundred fossil bones belonging to at least six individuals of metoposaurids from the basal part of the Late Triassic, Maleri Formation of the Pranhita-Godavari valley, Gondwana succession, has helped to formulate new ideas. Detailed morphological studies have been used to include all specimens of metoposaurids so far collected from India within a single taxon, Buettneria maleriensis, a new combination. A reconstruction of the skeleton of Buettneria maleriensis is presented for the first time. Buettneria maleriensis remains are common in the continental red beds of India, deposited under fluvial con- ditions witnessing seasonal climate changes. While some bones of Buettneria maleriensis were rolled and transported after death and are now found as sporadic fossils in mudstone (or occasionally in sandstones and calcirudites), the other type of occurrences, the rich accumulation of bones, are present only in mudstones. Buettneria maleriensis was replaced by the Chigutisauridae, a temnospondyl family exclusive to Gondwana- land. India is the only place where both metoposaurids and chigutisaurids are found in such close succession. The paleoposition of India during the later part of the Triassic may have been responsible for this. Key words: Buettneria, India, Late Triassic, Maleri Formation Introduction The Metoposauridae is a Late Triassic temnospondyl amphibian family known from Europe, North America, North Africa and India. They were quite large (at least 1.5 m in length), essentially aquatic animals (Defauw, 1989), with flat and heavily ornamented skull roofs marked with lateral line canals. Metoposaurids are to some extent mor- phologicaly similar to the present day crocodiles. How- ever, unlike crocodiles, they had limbs unsuitable for quick movement on land. The first metoposaurid, Metoposaurus diagnosticus (Meyer, 1842), was described from Europe. Subsequently a large number of metoposaurids belonging to several gen- era and species have also been reported from Europe and North America (Fraas, 1889, 1896, 1913; Lydekker, 1890; Watson, 1919; Romer, 1947; Colbert and Imbrie, 1956 and Werneburg, 1990). Dutuit (1976) carried out a study of another population of metoposaurids from North Africa. The Metoposauridae as a whole was extensively revised by Hunt (1993). However, Indian metoposaurids have not been studied in similar detail. Lydekker (1885) and Huene (1940) were the early workers to report metoposaurid frag- ments from India and Colbert (1958) discussed the signifi- cance of Indian metoposaurids in some detail. Later, Roy- chowdhury (1965) studied the Indian metoposaurids and recently a partial skull was described by Sengupta (1992). A revision of the Indian metoposaurids has been attempted here in the light of the recovery of more than a hundred fossilised bones belonging to at least six individuals. These remains represent a mass accumulation and were found near Aigerapalli village in the basal part of the Maleri Formation of the Pranhita-Godavari valley of Central India. Taphonomic and palaeobiogeographic studies of the metoposaurids have also revealed some interesting results. India is the only region where the typically Laurasian metoposaurs are found together with some stereospondyls exclusive to Gondwanaland. The significance of this asso- ciation will be discussed. Family Metoposauridae The family Metoposauridae is morphologically a very compact group which shares a number of character states. They have flat elongate skulls with tapering snouts, dorsolateral and anteriorly placed orbits, a pineal foramen far posterior to the orbits, low skulls with occipital condyles placed in the same line and plane (or a little pos- terior in certain cases) as the quadrate condyles, large paraquadrate foramina, spoollike intercentra (Romer, 1947; Watson, 1919, 1962; Colbert and Imbrie, 1956; Rouchowd- hury, 1965; Dutuit, 1976) and wide cultriform process of the parasphenoid (Coldiron, 1978). In addition, Milner 42 Dhurjati Prasad Sengupta (1990) noted that the palatine ramus of the pterygoid is rather short with a posteromedial ramus of the ectoptery- goid contributing to the strut. Jupp and Warren (1986) stated that, in metoposaurids, the posterior coronoid forms part of the dorsal margin of the posterior Meckelian fora- men. Warren and Snell (1991) further noted that the ilium of the metoposaurids has some taxonomic importance since the iliac blade is not “expanded” like other temnospondyls. They also noted that the metoposaurid humerus has well developed ends and prominent areas for muscle insertion, a rare trait among the temnospondyls. Both Werneburg (1990) and Warren and Snell (1991) suggested that the interclavicles of the metoposaurids have some characteris- tic features. While the monophyly of the family Metoposauridae is established, the taxonomy at the generic level is somewhat problematic. There are only a few character states which are variable between different populations as well as within the single population of a particular area. The problem of taxonomy of metoposaurids at the generic level thus de- pends on proper understanding of those limited numbers of character states. Colbert and Imbrie (1956) used two character states to differentiate the North American from the European popu- lations. In the North American populations the lachrymal enters the orbit margin while in the European forms it does not. The degree of overlap of the clavicles on the interclav- icles and the pattern of ornamentation of the clavicles were also different in the North American and European metoposaurids. Roychowdhury (1965) grouped all the metoposaurid genera into a single genus, Metoposaurus. Subsequently Dutuit (1976) erected some new species from North Africa and designated them as Metoposaurus at the generic level. Gregory (1980) pointed out that there are at least two metoposaurid genera present in North America; one with an otic notch and the other without. Davidow-Henry (1989) divided the metoposaurids into three generic groups, one with otic notches, one without, and a third having a pineal foramen placed more forward than in the others. This splitting was continued by the recent work on metoposaurid taxonomy by Hunt (1993) and Milner (1994). Hunt (1993) divided the metoposaurids into five genera and six species. They are: Metoposaurus diagnosticus (Meyer, 1842), M. bakeri (Case, 1931), Buettneria perfecta (Case, 1922), Dutuitosaurus ouazzoui (Dutuit, 1976, new combination sensu Hunt, 1973), Arganasaurus lyazidi (Dutuit, 1976, new combination sensu Hunt, 1973)and Apachesaurus gregorii (Hunt, 1993). Hunt stated that the last-mentioned genus has a very shallow otic notch while in the other gen- era they are deeper. The most conspicuous change in the work of Hunt (1993) is the lumping of many taxa found from various places of the world into Buettneria perfecta, which also in- cludes the Indian metoposaurid, Metoposaurus maleriensis (Roychowdhury, 1965), making it a junior synonym of B. perfecta. All the species of Buettneria have their lachry- mals included within the border of the orbits. Following a different approach, Milner (1994) grouped the metoposaurids into more than one “grade” which are further divided into certain “clades.” He included “M. maleriensis” within the clade Anaschisma. The latter ac- cording to him is a “terminal clade” with the elongate lach- rymal entering the orbit margin (a character-state of grade Buettneria), large, closely spaced nares and the supraorbital lateral line canals always broken behind the orbits (charac- ter states which separate Anaschisma from Buettneria). Indian metoposaurids The history of the work on Indian metoposaurids was discussed in detail by Roychowdhury (1965). Only one more specimen of the family has been described in recent years by Sengupta (1992). Hence only a brief discussion on the Indian metoposaurids is provided below. In India metoposaurids are known from the Maleri Formation of the Pranhita Godavari (P-G) valley and the Tiki Formation of the Son Mahanadi valley. Initially, the Indian metoposaurids were known from fragmentary sur- face collections which did not permit diagnosis below fam- ily level (Lydekker,1885; Huene,1940). Later, systematic collection of in situ specimens from the Maleri Formation yielded a number of well preserved fragments. These fragments were sufficiently diagnostic and included at least two partial skulls, clavicles and interclavicles, and vertebral elements. Roychowdhury (1965) erected Metoposaurus maleriensis on the basis of these specimens and also pre- sented a restoration of the skull. As mentioned earlier Hunt (1993) included M. maleri- ensis aS Buettneria perfecta. The taxonomic status of the Indian metoposaurids is revised in the present work. All the specimens of the Indian metoposaurids are grouped into a single genus and species, Buettneria maleriensis, a new combination. Systematic paleontology Order Temnospondyli Zittel, 1888 Family Metoposauridae Watson, 1919 Genus Buettneria Case, 1922 Buettneria maleriensis (Roychowdhury, 1965) new combination Figures 1-16 Metoposaurus maleriensis Roychowdhury, 1965, p. 21, figs. 3- Indian metoposaurid amphibians revised 43 Figure 1. Skull roof (A = ISIA 56, C = ISIA 59), palate (B = ISIA 56), interclavicle (D = ISIA 67) and occiput (E = ISIA 53) of Buettneria maleriensis, new combination. Scale bars = 5 cm. 44 Figure 2. new combination. Dhurjati Prasad Sengupta Palate (A = ISIA 58), skull roof (B = ISIA 58) and mandible (C, D = labial and lingual view of ISIA 60) of Buettneria maleriensis, Scale bars = 5cm. Indian metoposaurid amphibians revised 45 fj Ca ue Y 2 lpr Figure 3. Skull roof of Buettneria maleriensis, new combination, A = ISI A 4, B = ISI A 59. sa QJ Abbreviations: F= frontal; J = jugal; L = lach- rymal; N = nasal; P = parietal; PRF = prefrontal; PMX = premaxilla; PO = postorbital; PP = postparietal; PF = postfrontal; QJ = quadratojugal; SQ = squamosal; ST = supratemporal; T = tabular. Scale bars = 5 cm. 20, pls. 21-41; Sengupta, 1992, p. 300, figs. 1-4, pl. 1. Buettneria perfecta, Hunt, 1993, p. 78, figs. 7-9 (in part). Material examined.—GSI 2249, 2254 and 2263 (Lydek- ker, 1885), K 33/638, 616a, b, 630a, 606a, 611a, 602a (Huene, 1940), ISI A 1 to 17 (Roychowdhury, 1965), ISI A 53 (Sengupta, 1992), ISI A 56, and ISI A 58 to175. The specimens with numbers starting with ISI A are housed in the Geological Museum, Indian Statistical Institute, Calcut- ta, India (Table 1) and specimens K 33/638, 616a, b, 630a, 606a, 611a, 602a, and GSI 2249, 2254 and 2263 are kept in the Indian Museum, Calcutta, India. Holotype.—ISI A 4, in the collection of the Geology Museum, Indian Statistical Institute, Calcutta, India. Paratypes.—ISI A 1 to 3 and ISI A 5 to 17, 53, 56, 58 to 175. Distribution and age.—B. maleriensis occur in the lower part of the Maleri Formation of the Pranhita Godavari val- 46 Dhurjati Prasad Sengupta Figure 4. Scale bars = 5 cm. ley and also in the Tiki Formation of the Son Mahanadi valley of Central India. Material examined were mostly collected around the villages of Achlapur, Gampalpalli and Aiegarapalli, Adilabad District of Andhra Pradesh, India. The age of B. maleriensis is Late Carnian. Diagnostic characters. — Buettneria maleriensis has the lachrymal in the margin of the orbits and thus it differs from all other metoposaurids except B. perfecta, sensu Hunt (1993). B. maleriensis differs from most specimens of B. perfecta in the presence of large, closely spaced nares and lateral line canals never forming a loop behind the or- Skull roof of Buettneria maleriensis, new combination, A = ISI A 8, B = ISI A 58. Abbreviations used are same as Figure 3. bits (Milner, 1994). Two specimens (FMNH UC 447 and 448, kept in the Field Museum of Natural History, University College collection, Chicago) designated as “Anaschisma” by Branson, 1905 have similarity with B. maleriensis in this regard. B. maleriensis, however, has a different type of ornament than that of “Anaschisma” and has a comparatively larger orbit. The lachrymal is present as a narrow strip of bone in B. maleriensis. The anterior boundary of the lachrymal and that of the prefrontal are at the same level. All the speci- mens of B. maleriensis are unique in having parts of the Indian metoposaurid amphibians revised 47 Table 1. List of the specimens of Buettneria maleriensis new combination, housed in the Geology Museum, Geological Studies Unit, Indian Statistical Institute (ISI) Calcutta. Element ISI no. Element ISI no. Element ISI no. Part of skull ISIA I Femur, Right ISI A 84 Intercentrum (Dorsal) ISI A 129 Part of skull ISIA2 Femur, Right ISI A 85 Intercentrum (Dorsal) ISI A 130 Part of skull ISI A 3 Ilium, Right ISI A 86 Intercentrum (Dorsal) ISI A 131 Part of skull ISI À 4 Ilium, Right ISI A 87 Intercentrum (Dorsal) ISI A 132 Left squamosal ISI A 5 Ilium, Right ISI A 88 Intercentrum (Dorsal) ISI A 133 Part of skull ISIA 6 Scapulacoracoid, Rt ISI A 89 Atlas ISI A 134 Part of skull ISI À 7 Scapulacoracoid, Rt ISI A 90 Atlas ISI A 135 Part of skull ISI A8 Scapulacoracoid, Rt ISI À 91 Intercentrum (Caudal) ISI A 136 Interclavicle ISI A 9 Scapulacoracoid, Lt ISI A 92 Intercentrum (Caudal) ISI A 137 Left clavicle ISI A 10 Scapulacoracoid, Lt ISI A 93 Intercentrum (Caudal) ISI A 138 Left clavicle ISIA 11 Scapulacoracoid, Lt ISI A 94 Intercentrum (Caudal) ISI A 139 Right clavicle ISIA 12 Ulna, Right ISI A 95 Intercentrum (Caudal) ISI A 140 Atlas ISI A 13 Ulna, Right ISI A 96 Intercentrum (Caudal) ISI A 141 Four vertebrae ISLA 14 Ulna, Left ISI A 97 Intercentrum (Caudal) ISI A 142 Three vertebrae ISI A 15 Tibia, Right ISI A 98 Intercentrum (Caudal) ISI A 143 Right ischium ISI A 16 Tibia, Left ISI A 99 Intercentrum (Caudal) ISI A 144 Left humerus ISIA 17 Radius, Right ISI A 100 Intercentrum (Caudal) ISI A 145 Partial skull ISI A 53 Fibula, Right ISI A 101 Intercentrum (Caudal) ISI A 146 Complete skull ISI A 56 Neural spine ISI A 102 Intercentrum (Caudal) ISIA 147 Partial skull ISI A 58 Neural spine ISI A 103 Intercentrum (Caudal) ISI A 148 Complete skull ISI A 59 Neural spine ISI A 104 Rib (Dorsal) ISI A 149 Left msndible ISI A 60 Neural spine ISI A 105 Rib (Dorsal) ISI A 150 Left mandible ISI A 61 Intercentrum (Dorsal) ISI A 106 Rib (Dorsal) ISI A 151 Right mandible ISI A 62 Intercentrum (Dorsal) ISI A 107 Rib (Dorsal) ISI A 152 Right mandible ISI A 63 Intercentrum (Dorsal) ISI A 108 Rib (Dorsal) ISI A 153 Clavicle, left ISI A 64 Intercentrum (Dorsal) ISI A 109 Rib (Dorsal) ISI A 154 Clavicle, left ISI A 65 Intercentrum (Dorsal) ISI A 110 Rib (Cervical) ISI A 155 Interclavicle ISI A 66 Intercentrum (Dorsal) ISI A 111 Rib (Dorsal) ISI A 156 Interclavicle ISI A 67 Intercentrum (Dorsal) ISI A 112 Rib (Dorsal) ISI A 157 Humerus, Right ISI A 68 Intercentrum (Dorsal) ISI A 113 Rib (Dorsal) ISI A 158 Humerus, Left ISI A 69 Intercentrum (Dorsal) ISI A 114 Rib (Dorsal) ISI A 159 Humerus, Right ISI A 70 Intercentrum (Dorsal) ISI A 115 Rib (Caudal) ISI A 160 Humerus, Right ISIA 71 Intercentrum (Dorsal) ISI A 116 Rib (Caudal) ISI A 161 Humerus, Right ISI A 72 Atlas with spine ISI A 117 Rib (Dorsal) ISI A 162 Humerus, Left ISI A 73 Axis ISI A 118 Rib (Dorsal) ISI A 163 Humerus, Right ISI A 74 Axis ISI A 119 Rib (Cervical) ISI A 164 Humerus, Right ISI A 75 Axis ISI A 120 Rib (Caudal) ISI A 165 Humerus, Left ISI A 76 Intercentrum (Dorsal) ISI A 121 Rib (caudal) ISI A 166 Ischium, Left ISI A 77 Intercentrum (Dorsal) ISI A 122 Phalange (post.right) ISI A 167 Ischium, Right ISI A 78 Intercentrum (Dorsal) ISI A 123 Phalange (post.right) ISI A 168 Ischium, Left ISI A 79 Intercentrum (Dorsal) ISI A 124 Phalange (post.right) ISI A 169 Cleithrum, Left ISI A 80 Intercentrum (Dorsal) ISI A 125 Phalange (ant.right) ISI A 170 Cleithrum, Right ISIA 81 Intercentrum (Dorsal) ISI A 126 Phalange (ant.right) ISI A 171 Cleithrum, Left ISI A 82 Intercentrum (Dorsal) ISI A 127 Phalange (ant.right) ISI A 172 Femur, Left ISI A 83 Intercentrum (Dorsal) ISI A 128 Phalange (ant.right) ISI A 173 Phalange (post.right) ISI A 174 two main sets of the line canals, lateral and supraorbital, within the lachrymal. They are sinuous and touch each other inside the lachrymal. The ratio of the width of the lachrymal at the orbit mar- gin and the diameter of the orbit ranges between 0.2588 and 0.3409 in B. maleriensis. This ratio ranges from 0.6 to 0.4545 in case of B. perfecta. It appears that in B. per- fecta the lachrymal is more equant and has a wider inser- tion on the orbit margin (Case, 1922, fig. 1). This is evident also in “B. howardensis” (Sawin, 1945, fig. 3) and in “Eupelor browni” (Colbert and Imbrie, 1956, fig. 8) which were grouped into B. perfecta by Hunt (1993). The curvature of otic notch, the shape of the tabular horn, the position and size of the orbits and the narial open- ings with respect to the skull length are also more uniform among the specimens of B. maleriensis than they are in B. 48 Dhurjati Prasad Sengupta Figure 5. A = ISI A 56, skull roof of Buettneria maleriensis, new combination (abbreviations used are same as Figure 3). B = Occiput of B. maleriensis, based on the right side of ISIA 58. Abbreviations: EO = exoccipital; EOC = exoccipital condyle; FM = foramen magnum; OL= otic lamellae; PFM = paraquadrate foramen; PP = postparietal; PT = pterygoid; PTF = posttemporal fenestra; PTS = pterygoid sinus; Q = quadrate; QJ = quadratojugal; SQ = squamosal; XT = broken part of the stapes; T = tabular; TB = tubercule. perfecta. Remarks.—As discussed earlier, Hunt (1993) differenti- ated Buettneria from all other metoposaurids by the pres- ence of the lachrymal in the orbit border. Other metoposaurids were further divided into several genera and species on the basis of certain synapomorphies and autapomorphies. For example, Dutuitosaurus and Apache- saurus share the apomorphy of having presacral centra with a diameter length < 0.8 cm and the former has the maxilla entering the orbit margin as an autapomorphy (Hunt 1993, Scale bars = 5 cm. p. 80). For the genera which do not have the lachrymal in the orbit margin, the shape of the lachrymal was considered by Hunt (1993) to separate Metoposaurus diagnosticus from Metoposaurus bakeri. Apachesaurus has been partly characterised by the flexure of the supraorbital canal being separated from the lachrymal (Hunt, 1993, p. 81). However, all metoposaurids having their lachrymal in the orbit were grouped as B. perfecta by Hunt. The shape of the lachrymal or the position of the flexure of the supraorbital line canals or any other variations were not Indian metoposaurid amphibians revised 49 Figure 6. A = ISI A 53, skull roof of Buertneria maleriensis, new combination (abbreviations used are same as Figure 3). B,C = Interclavicles of B. maleriensis; B = collected from Tiki Formation (G.S.I. 2249, originally described by Lydekker 1885 as a skull roof bone), C = from Maleri (K33/638, Huene 1940). considered. Thus Buettneria sensu Hunt (1993) lacks any autapomorphy and results in a metataxon (Smith, 1994). Differentiating B. maleriensis from B. perfecta (sensu Hunt, 1993) on the basis of the width of the lachrymal at the orbit margin and the presence of the flexures of both the lateral and supraorbital line canals on the lachrymal is, therefore, relevant. A, B and C are after Sengupta 1992. Scale bars = 5cm. The localities yielding B. perfecta are restricted to the central and eastern United States, western Europe and northeastern Africa. During Late Triassic times these lo- calities were believed to be very close and probably con- nected by land (Hunt, 1993, fig. 1). The population of B. maleriensis occurs outside that zone. Roychowdhury (1965) also emphasized the geographic isolation of the 50 Dhurjati Prasad Sengupta I fh N / = hay XS / N fi IN N / es a! I \ N 1,7 RD KE D D Ka . a, is Pa a bacs … APV - DS I N \ Zu “I, a ‘Hy i 4 Q PTF OPIS AMPA SH AMPL AOP Figure 7. A = ventral view of the palate of Buettneria maleriensis, new combination based on ISIA 56. B = the anterior palatal vacuities and the straight row of teeth behind based on a supplementary fragment ISIA 56a collected from Nalapur. Note the detached tooth, complete and well preserved, cemented later on the vomer. C = ventral view of the skull roof of B. maleriensis based on ISIA 59. Abbreviations: AJP = alar process of the jugal; AMPA = adductor mandibulae, posterior articularis (after Wilson, 1941); AMPL = adductor mandibulae posterior longus (after Wilson, 1941); AOP = attachment for the cartilaginous otic process; APV = anterior palatal vacuity; ASO = attachment for the supraoccipital; CH = choana; DBC = dorsal side of cartilaginous brain case; ECT = ectopterygoid; EO = exoocipital; MX = maxilla; NC = dorsal impression of the nasal capsule (after Wilson, 1941); OT = otic capsule; PAL = palatine; PMX = premaxilla; PMXT = premaxillary teeth; PSP = parasphenoid; PT = pterygoid; PTD = deep portion of pterygoideus (after Wilson, 1941); PTF = posttemporal fenestra; PTS = superficial pterygoideus (after Wilson, 1941); Q = quadrate; SH = suspensorius hyoideus (after Wilson, 1941); V = vomer; Vt = vomerine tusk. Scale bars = 5 cm. Indian population and suggested that biometric studies Colbert and Imbrie (1956, figs. 13, 14, p. 434-438, table could reveal its specific characters. The biometric studies 8) illustrated a technique to plot the bivariate population of Indian metoposaurids will be dealt in a separate publica- range diagram of certain skull roof parameters. The field tion. Meanwhile certain observations are noted below. range for B. maleriensis has been calculated using similar Indian metoposaurid amphibians revised 51 Figure 8. Dorsal view of the palate of Buettneria maleriensis, new combination; A = ISI A 59; B = ISI A 7, after Roychowdhury (1965). Abbreviations: DSQ = descending process of the squamosal; E = epipterygoid; EO = exooccipital; EOR = ascending process of the exoccipital (broken); LOT = lateral ridge bounding otic region; OT = otic capsule; PCR = ridge on the cultriform process of the parasphe- noid; POT= posterior ridge bounding otic region; PSP = parashenoid; QJ = quadratojugal; RBPT= rim of the basipterygoid process; SPH= depression for sphenethmoid; SQ= squamosal. Scale bags = Scm. B. techniques. It is found that the range of B. maleriens is specific and only partly overlapping with the multigeneric North American species now grouped together as Buett- neria perfecta by Hunt (1993). Sengupta and Ghosh (1993) attempted some cephalo- metric studies of some of the individuals of the North American metoposaurids and B. maleriensis. They used several skull roof parameters and extracted three major Figure 9. Right mandible of Buettneria maleriensis, new com- bination based on ISIA 60. From top: labial, lingual and dorsal views. Bottom: left mandible of Buettneria maleriensis based on ISIA 61. Abbreviations: ADF = adductor fossa; AMF = anterior Meckelian foramen; ANG = angular; CR (1,2,3) = coronoids; D = dentary; PIP = preglenoidal internal process; PMF = posterior Mecke- lian foramen; PRT = prearticular; PTP = postglenoidal process; RTP = retroarticular process; SA = surangular; SP (1,2) = splenials. Scale bar = 5 cm. factors through a principal-component-based factor analy- sis. They found that the plots of the factor scores on two- dimensional Cartesian coordinates (Sengupta and Ghosh, 1993, fig. 2) indicate a peripheral position of the Indian metoposaurids with respect to the main concentration of the similar plots of the American metoposaurids. General characters of Buettneria maleriensis Osteology of both the dorsal and ventral sides of the skull roof and of the palate of the metoposaurids have been described in some detail by Cope (1868), Fraas (1889, 1913), Case (1922, 1932 ), Watson (1919), Sawin (1945 ), Romer (1947), Colbert and Imbrie (1956), Roychowdhury (1965), Dutuit (1976) and Hunt (1993) among others. Wilson (1941) discussed the soft parts. Hence only the general characters of the skull of B. maleriensis are given below. Skull roof.—Buettneria maleriensis has a very flat skull with short snout and anterolaterally placed orbits (Figures 52 Dhurjati Prasad Sengupta Figure 10. single atlas with anterior (F) and dorsal (G) views are also shown. dal intercentra. 1A-C; 2A, B; 3; 4; 5A; 6A). Skulls have well defined, curved tabular horns and deep otic notches. The pineal fo- ramen is placed well posterior to the orbit. The postparie- tal is shorter than the parietal. The posterior part of the skull has rather thick rectangu- lar bones, namely the tabular, postparietal, parietal and supratemporal, which are strongly ornamented with circular pits walled by high ridges. The snout, with close, large nares, is also well built with a similar type of ornament. Premaxilla and nasal are the two major bones in this area. Roychowdhury (1965) noted the presence of an extra bone in one of the specimens (ISI A 4) of B. maleriensis exposed on the dorsal surface of the skull. No such bone has been identified in any of the newly collected specimens. This is probably the extra Elements of vertebral columns of Buettneria maleriensis, new combination. presacral column; C = dorsal, D = lateral and E = ventral views of second such pre sacral column. H, I and J are the dorsal, lateral and ventral views of a set of three adjacent cau- All the specimens were collected from the Aigerapalli accumulation. A = lateral and B = dorsal views of one possible AT and AX are the atlas and the axis. Another Scale bars = 5 cm. sutural growth noted in many temnospondyls (Romer, 1947; Welles and Cosgriff, 1965). The floor of the naris is made up of the septomaxilla which is thin and flat. The middle part of the skull table is flat, thin and has elongate bones, namely, the frontal, postorbital, prefrontal and jugal with elongate ridges and valleys as ornament. The lateral line canals do not form a loop posterior to the orbit. The lachrymal becomes narrow and touches the orbit margin. Palate.—The ventral side of the palate (Figure 7A, B) has a flat rectangular base composed of parasphenoid from which a triradiating structure emerges with two palatine rami of the pterygoid between sub temporal and interptery- goid vacuities and a wide, flat cultriform process of the parasphenoid in the middle. The latter connects the base Indian metoposaurid amphibians revised Figure 11. vical, thoracic, sacral and caudal ribs are not known. at the top and internal view at the bottom). rib; D = possibly the lone sacral rib and E = caudal rib. Scale bar = 5 cm. of the parasphenoid to the wide vomers. On the ventral side of the skull roof a narrow ridge is present in the midline particularly in the postorbital part (Figure 7C). This tapers towards the anterior and is perforated by the pineal foramen. This ridge corresponds in position to the depression present on the dorsal side of the cultriform proc- ess of the parasphenoid. This depression probably housed the cartilaginous sphenethmoid (Figure 8). The position of the epipterygoid and the foramen of the internal carotids, the recess for the basipterygoid process, the anterior end of the depression for the sphenethmoids and the position of the arcuate ridges bordering the otic re- gion on the dorsal side of the palate of B. maleriensis are figured (Figure 8). These features, however, are similar in all the metoposaurids (see Case, 1922, figs. 2, 3; Wilson, 1941, figs. 1, 2; Roychowdhury, 1965, fig. 12; DuTuit, 1976, pls. 11-15). On the dorsal side of the pterygoid, in ISI A 59, a part of the epipterygoid is preserved (Figure 8A, B). The ascend- Nn Ww gay Ribs (left side) of Buettneria maleriensis, new combination based on specimens ISIA 149 to ISIA 166. The total number of cer- In the diagram, only the preserved specimens are arranged one after another (external view A = one of the two cervical ribs preserved. B =a typical anterior thoracic rib; C = posterior thoracic ing process of the epipterygoid was previously illustrated by Roychowdhury (1965, p 28). The braincase and associ- ated features, the position of the epipterygoids and adjacent canals shown by Roychowdhury (1965), Case (1922) and Dutuit (1976) are noted in almost all the new specimens of B. maleriensis. Similar braincases are partly preserved in ISI A 7 and ISI A 59. The stapes is partly preserved in two individuals, ISI A 56 and ISI A 58 (Figure 5B). Maxillary and palatal dentitions.—Maxillary and palatal dentitions extend far posterior to the centre of the inter- pterygoid vacuities. Vomerine and palatine tusks are pre- sent. One of the paratypes (ISI A 56a) has two well deve- loped, circular, well separated, anterior palatal vacuities and a series of small vomerine teeth posterior to them (Figure 7A, B). Occiput.—The occiput has the shape of a triangle with the base made up of postparietal and tabular on the dorsal side (Figure 5B). The exoccipital sutures with the postparietal and tabular housing a small, circular posttem- 54 Dhurjati Prasad Sengupta Figure 12. Some of the postcranial bones of Buettneria maleriensis, new combination, collected from the Aigerapalli metoposaur graveyard. A = Humeri, ventral view (ISIA 69 to 76), B = Femora, ventral view (ISIA 83 to 85), C = Ilia, lateral view (ISIA 86 to 88), D = Cleithra, mesial view (ISIA 80 to 82), E = Ischia, dorsal view (ISIA 77 to 79) and F = Scapulocoracoids, mesial view (ISIA 89, 90, 92, 94) with supraglenoid foramen (SF). Scale bars = 5 cm. poral fossa at the junction of the three bones. The foramen magnum is at the centre of the triangle which is terminated by the flat parasphenoid and occipital condyles almost at the same ventral level. There is a little vaulting of the pterygoid and the ascending processes of the bone sutures with the quadratojugal and squamosal. These bones form the dorsal margin of a large, elliptical paraquadrate fora- men. Unlike the earlier composite reconstruction of the occiput (Roychowdhury, 1965, fig. 11, p. 21), the speci- mens described here show a thin insertion of the pterygoid in the lateral part of the paraquadrate foramen. Mandible.—The mandible of B. maleriensis is described here for the first time. Two complete mandibles and a few broken fragments are available for study (Figure 9). The specimens are deepest in the region of the angular and their cross-sections are squared at the midlength. One of the specimens (ISIA 60) is more cylindrical in cross-section and narrow at the region of the spenials. The mandible has Indian metoposaurid amphibians revised Nn Nn Figure 13. Clavicles and interclavicles of Metoposaurus diagnosticus Fraas, 1913 (A = clavicle, B= interclavicle; C= clavicle interclavicle together); “Buettneria howardensis” Sawin, 1945 (D =clavicle; E = interclavicle; F = clavicle interclavicle together); B. maleriensis, new combina- tion. (G = clavicle: H = clavicle; I = interclavicle; J = clavicle interclavicle together); “M. For B. maleriensis two different types of clavicles are shown (G and H). interclavicle together; M = interclavicle); Sc = sensory canal. ouazzouri” Dutuit, 1976 (K = clavicle; L= clavicle C; F and L are after Wernerburg (1990). Diagrams are schematic (not in scale) as interclavicles are enlarged (compared to respective clavicles) to illustrate the ornament. a short retroarticular process with articular, surangular and prearticular exposed on the dorsal surface. Jupp and Warren (1986) described this as the type of postglenoid area noted in some temnospondyls including metopo- saurids. The angular is the dominant bone of the labial side. On the lingual side a large, elongate posterior Meckelian foramen is present whose anterior border is formed by the posterior coronoid. The adductor fossa is 56 Dhurjati Prasad Sengupta Ail thy ANS 5 ‘ al Hl * 7 ENTP internal, D = posterior views and right I = digits of manus of the right DLPR Figure 14. Right radius of Buettneria maleriensis, new combination, A = external, B = anterior, C = ulna E = external, F = anterior, G = internal, H = posterior views (based on ISIA 100 and ISIA 95 respectively). side (ISI A 170, to 173, phalangeal formula based on Dutuit , 1976). Right humerus based on ISIA 68; J = Ventral, K = Dorsal views. = Deltoidial process; ECTP = ectepicondyle; ENTP = entepicondyle; SUPPR = supinater process. Scale bars = 5cm. large and elliptical. No coronoid process is present. There is a large circular depression around the symphyseal tusk which forms part of the dentary tooth row. A small row of teeth is present on the inner side of the circular de- pression. Vertebral elements.— All metoposaurids have typical discoid intercentra of different sizes and shapes (Figure 10). The overall shapes vary from circular to triangular and sometimes these variations are associated with their po- sition in the vertebral column. Variations are also noted Indian metoposaurid amphibians revised Left tibia of Buettneria maleriensis, new combination, A = posterior, B = internal, C = anterior, D = external and right fibula, E (based on ISIA 99 and 101 respectively). Pes of the right side (based on ISI A 167, 168, Left femur based on ISIA 83; J = ventral, K = dorsal views; TR = trochanter. Scale Figure 15. = posterior, F = internal, G = anterior, H = external. 169 and 174). Phalageal formula based on Dutuit (1976). bars = 5 cm. trated 22 intercentra for one individual of “M. ouazzoui” among individuals. The vertebral count of an individual of In the recon- the metoposaurids is uncertain. Sawin (1945) figured 18 (XIII /14/66) and 20 for another (XIII /4/66). presacral intercentra for Buettneria. Dutuit (1976) illus- struction of B. maleriensis an average of 20 presacral 58 Dhurjati Prasad Sengupta Figure 16. Composite restoration of Buettneria maleriensis, new combination. Dark lines represent elements from one individual. Scale bar = 10cm. intercentra have been figured. The new collection from Aigerapalli includes 23 dorsal and 13 caudal intercentra. From the accumulation of vertebral elements of at least six individuals, parts of two possible columns (Figure 10) are reconstructed from the presacral vertebrae following Sawin (1945) and Dutuit (1976). The atlas is double faceted at the anterior end to host the double condyles (Figure 10A, B, F, G). In one of the two inferred vertebral columns just mentioned (Figure 10A) the axis and one intercentra (possibly occurring just behind the axis) have two rib facets on the lateral side. In some of the intercentra the facets protrude whereas in larger irtercentra (which are possibly further down the trunk), the posterior presacrals have only the facet without the neck. Anterior to the facet there is another curvature. In lateral view these two curvatures form an hourglass-like depression. This is more pronounced in the caudal intercentra (Figure 101). The caudals are triangular in outline, quite flat on the dorsal side, platyocoelous to opisthocoelous and smaller in size (Figure 10H-J). Sawin (1945) figured a sacral intercentrum which really differs little from some of the presacrals of the Indian taxon. In one axis, a space created by the underside of the base of the posteriorly depressed neural arch and the scooped posterior dorsolateral part of the intercentrum clearly indi- cates the shape of the pleurocentrum. In another speci- men, parts of the plerocentrum are preserved. Dutuit (1976) described one vertebra of “M. ouazzoui” where both the intercentrum and pleurocentrum are preserved and the combined centrum looks like a discoid with a slightly off- centered notochordal perforation. This type of vertebra has also been observed in Compsocerops cosgriffi, an Indian chigutisaurid (Sengupta, 1995). However, no such pleurocentral ossification is noted in B. maleriensis. Unfortunately all the specimens in the collection have their neural arches broken. The axis has the base of the neural arch preserved in some specimens. An interver- tebral position of the arches has been predicted by some authors (e.g. Roychowdhury, 1965; Dutuit, 1976; Warren and Snell, 1991). However, there is no direct evidence for this in the specimens of B. maleriensis. Ribs.—The total number of ribs present is uncertain. Two cervical, several anterior presacral and some abdomi- nal ribs have been found (Figure 11). One possible sacral and few caudal ribs are also present. The cervicals have two separate facets or rib heads. The presacral rib heads are elliptical with capitulum and tuber- culum connected by a narrow extension. The postsacral ribs have triangular or even squarish heads. The anterior presacral units have flattened distal extensions with uncina- te processes. The abdominal ribs are cylindrical and lack the uncinate process. Warren and Snell (1991) noted that temnospondyls possess a single sacral rib which is ex- panded both proximally and distally and is stout and short. One short, curved and distally expanded rib is figured here as a possible sacral ribs (Figure 11D). It has a rather ex- panded proximal end but is quite thin. The caudals are shorter, curved and pointed distally. Elements of the pectoral girdle.— The scapulocoracoid and the cleithrum are new additions to the Indian metoposaurid collections. They have the usual characters of metoposaurids (Dutuit, 1976). The clavicle and interclavicle have already been described (Roychowdhury, 1965). The scapulocoracoid has an enclosed supraglenoid opening (Figure 12F). This was considered as a primitive character (Warren and Snell, 1991). The cleithrum is spoon-shaped with dorsal expansions (Figure 12D). Clavicle and interclavicle. — Roychowdhury (1965) noted two different types of clavicles in the Indian metopo- saurids. He also mentioned that the clavicles of M. diag- Indian metoposaurid amphibians revised 39 nosticus have a long contact anterior to the interclavicle which is not seen in B. maleriensis. Sengupta (1992) illus- trated two similar-looking interclavicles, one from the Tiki and the other from the Maleri Formation which are redrawn here (Figures 6B, C). Colbert and Imbrie (1956) used the difference in the position of the centre of ossification and the variable nature of the clavicle-interclavicle overlap as taxonomically important characters. This variability was also highlighted by Warren and Snell (1991) and Werneburg (1990). Figure 13 indicates the clavicles and interclavicles of different metoposaurid taxa with variations in the ornament, position of the centre of ossificaton and nature of overlap of the clavicle on the interclavicle. However, ISI A 12 as illustrated by Roychowdhury (1965, figure 18), has a unique shape. A sensory canal is present in the clavicles of the Indian metoposaurids. This was also noted in M. ouazzoui (Dutuit, 1976). Ilium and ischium.—The ischium is a semicircular bone and the ilium is elongate with a dorsal blade which is rather thick (Figure 12C). Warren and Snell (1991) considered this as a character of taxonomic value. Fore limbs.—The humerus, like all other metoposaurid humeri, is well built, twisted and has pronounced processes for muscle attachments (Figure 14J, K). The ulna (Figure 14A-D) and radius (Figure 14E-H) are similar to the ones described by Dutuit (1976) for the metoposaurids from Morocco. Some digits of the right manus were also found (Figure 141). Hind limbs.—The femur, figured for the first time here (Figure 15J, K ), is rather long and fully ossified with com- plete distal and proximal articular surfaces. The areas for trochanters are well developed. The tibia (Figure 15A- D), fibula (Figure 15E-H) and some digits of the right pes (Figure 151) are also figured. The proximal and distal end of the tibia and fibula are less expanded than in “B. howardensis” as figured by Sawin (1945). A composite restoration of B. maleriensis is shown in Figure 16. Aspects of taphonomy Buettneria maleriensis, as stated earlier, is known from a large number of specimens from the Maleri Formation of the Pranhita-Godavari valley. Its occurrence in the Tiki Formation of the Son Mahanadi valley is rare. Hence em- phasis is given here to the geology and the nature of occur- rence of B. maleriensis in the Maleri Formation. Geological attributes.—Mudstone, sandstone and peloi- dal calcarenite/calcirudite of various colours of the Maleri Formation crop out in NW-SE trending linear belts (Figure 17). The overall dip is 12 to 18 degrees towards the NE. The paleocurrent direction is towards the north. The mudstone is dominantly red in colour and is structureless. Smectite is the major constituent of the clayey part (Sarkar, 1988). Haematite crystals are also common and iron oxide is responsible for the red colour (Robinson, 1970). The mudstones are exceptionally rich in vertebrate fossils. The sandstone is usually calcareous, cross-bedded, fine- to coarse-grained, containing weathered feldspars and infrequent garnets. Rock fragments and clay galls of different size, shape and colours are common. Fining-upward sequences are discernible in the sandstones (Sarkar, 1988). The sand bodies form narrow elongate ridges with mudstone valleys in between. The peloidal calcarenite/calcirudite occurs either as soli- tary mounds and/or a string of such mounds within the red mudstone and also at the bottom of the sandstone (Sarkar, 1988, p. 267). The peloidal calcarenite/calcirudites are cross-bedded with overlapping troughs of various magni- tudes and comprise calcite-cemented spherical or discoid peloids of micrite or microspary calcite. According to Sarkar (1988) the paucity of broken abraded peloids and other evidences indicate a local pedogenic origin of the peloids. Sengupta (1970) noted that while the mudstones repre- sent the interchannel facies, the sand bodies are deposited in the channels of a meandering river system flowing north in a large valley trending NW-SE. Maulik and Chaudhuri (1983) described such sandbodies as ephemeral channel fills. Palaeoclimate. — Pascoe (1959) suggested that the Maleri sediments were deposited in an extremely arid envi- ronment. Robinson (1970) first noted that the red mud- stones of the Pranhita-Godavari valley were not necessarily deposited in desert like conditions. The Maleri vertebrate fauna indicates a well watered country. The colour of the mudstone is imparted by iron oxides and the high content of ferric oxides and presence of haematite crystals indicate an oxidising environment of deposition. Recent works suggest that the red colour may be remotely linked with cli- mate (Pye, 1983). The absence of many dessication cracks and footprints as well as the occurrence of fewer evaporites indicate that the climate was not arid. This is also sup- ported by the presence of unionids and an array of aquatic or amphibious vertebrates. The paucity of plants was pre- viously considered as an indicator of aridity. However, this is negative evidence and a good number of herbivore remains are found. On the other hand, the high smectite content (Sarkar, 1988) may indicate low rainfall (Singer, 1980). Peloidal calcirudite and arenite are also indicative of reworking of older soil profiles (Sarkar, 1988). To ex- plain the contrasting evidence it is suggested that there was possibly seasonality in the climate. The aquatic members of the Maleri fauna, living in ephemeral rivers, had sur- vived the drier situations by concentrating in the more per- manent bodies of water (Robinson, 1971; Chatterjee et al., 60 Dhurjati Prasad Sengupta 1987). Mode of occurrence. — Animals living in the lowland habitat are mostly found in the floodplain deposits of the Maleri Formation (Kutty, 1971). Though exact propor- tions are difficult to determine, the number of lowland metoposaurids are always more than those of the robust rhynchosaurs and phytosaurs. The floodplains were well watered with a good drainage as remains of lowland or semiaquatic vertebrates are found there, associated with oc- casional bivalves, fossil wood and other sporadic plant de- bris, within thick red-coloured mudstones (Behrensmeyer and Hook, 1992). Fossils are found as cracked, flaked or distorted bones which are often covered by peloidal calcirudite and calcarenite and calcareous concretions. Various stages of bone weathering (Behrensmeyer, 1982) are also present in the fossilized bones of the Pranhita-Godavari valley (Sen- gupta, 1990). The transported, disarticulated, abraded bones indicate large time gaps between their death and bur- ial (Behrensmeyer and Hook, 1992) In most of the red beds of the Maleri Formation verte- brate remains occur chiefly as surface accumulations of stray fragments and also as in situ bones in the floodplains. The in situ bones, in turn, can be fragmentary or complete. Four taphonomic facies can be identified in the Maleri sedi- ments. The vertebrate bones occur as 1) complete in situ material in the mudstone, 2) fragmentary but in situ mate- rial in mudstone, 3) well preserved but broken bone accu- mulation in the sandbodies or in the peloids and 4) stray surface accumulation in the mudstones. Types 2 and 3 can be subdivided into i) isolated but broken skeletal parts and ii) fragments of one or more skeletal elements. Bones belonging to metoposaurids are found in all these types of accumulations. Most of the metoposaurid mate- rial described by the early workers like Miall (1875), Lydekker (1885) and Huene (1940) belonged to taphono- mic facies 4. Voorhies (1969) noted three major groups of bones according to their potential for dispersal particularly by water. The bulk of the specimens of B. maleriensis be- long to Voorhies’ (1969) group which constitutes an assem- blage of skulls and mandibles. This indicates the trans- ported nature of the metoposaurid material from the Maleri Formation. The most common skull fragments are of the tabular area as it is the strongest. The jaws are frequently represented by the symphyses. The skull margins are often preserved, without the thin midskull region. The deposition of peloidal calcirudites of diagenetic origin on the bones indicates various orders of reworking. The above taphonomic picture indicates that, after death, the semiaquatic and lowland fauna of the Maleri Formation, living in a seasonal climate, were mostly ex- posed on the flood plains and were fragmented and trans- ported (and even reworked). The lowermost mudstone unit of the Maleri Formation is the thickest (Figure 17) and there the remains of lowland vertebrates are high in num- ber. In that unit, due to some events leading to mass accu- mulations, finds like Aigerapalli came into being. A closer look at the Aigerapalli site may reveal some more in- formation. Taphonomy of the Aigerapalli accumulation. — The Aigerapalli site, near the base of the basal mudstone, chiefly comprises mudstones of red colour, with a few streaks of white, calcareous, fine- to medium-grained well- sorted sandstone. The bones were excavated from an area of only 10 m by 5 m which yielded over 100 disarticulated bones of several individuals. There are 9 humeri (6 from the right side and 3 from the left) from six individuals with three different size ranges (Figure 12A). As indicated by the size ranges, two indi- viduals were larger in size, one intermediate and three were small. The larger humeri come in the size range of 12.6 to 11.5 cm in length. There are three such specimens (a left and two from right) from two individuals. The next size range is a left and a right humerus of around 10 cm length possibly representing another individual. The last size range is around 6 cm length and from 4 specimens (three from left and one right) at least three individuals can be identified. The three size domains are also supported by the length of the three femora (Figure 12B). However, two skulls were recovered of which one is complete. Though the thickest mudstone unit of the Maleri contains the metoposaur accumulation, sporadic occurrence of peloidal calcarenites/rudites within the unit suggests inter- mittent exposure to aridity. In fact, it is argued in the sec- tion dealing with paleoclimate that contradictory evidence for aridity and humidity are present in the lithology and fauna of the Maleri Formation and a seasonal climate could be a possible explanation. The aquatic fauna survived in small deeper pools at the time of aridity and might have moved away in search of safer places (Robinson, 1971, Chatterjee et al., 1987). While doing so they could be trapped in the thick mud. Their remains were buried after being scattered by various agents. The bones have evi- dences of some amount of transportation. On the other hand, some of the small postcranial as well as a number of small and delicate teeth are well preserved. Hence, the transportation was possibly not prolonged. The Aigerapalli type of bone accumulation is not uncom- mon at other metoposaurid-yielding localities around the world (Romer, 1939; Dutuit, 1976). The absence of ar- ticulated individuals is marked in the Aigerapalli and also in the mass accumulation of metoposaurids in the Lamy amphibian quarry in New Mexico (Romer, 1939). The lat- ter has a similar taphonomic background to Aigerapalli where hydrodynamic sorting of bones of dead individuals from a residual pool affected by drought has been thought Indian metoposaurid amphibians revised DHARMARAM 79°30" 0 1 7 Q Fe ee * Chigutisaurids u faunal boundary IN e Buettneria maleriensis PELOIDAL CALCIRUDITE ICALCARENITE Figure 17. Geological map around the villages of Maleri and Dharmaram. Legends: a = Kamthi Formation, b = Yerrapalli Formation, c = Bhimaram Formation, d = Maleri Formation. Within the Maleri Formation the boundary between the lower and upper Maleri fauna is shown. The lines 1, 2 and 3 represent the positions of the columnar sections shown below the map. 62 Dhurjati Prasad Sengupta Rhaetian SNUNVSOIDV Td Norian JISSVIAL ALVT SNUNVSAHIVdV V193143d VIdANLLANG Late Carnian SNdODSILVT rn roe dagl ‚ge 2 re © = a: ww oad 9,75 Ke > IS 8 à _ p > w + 35 2 z= a» mo 9 am 2 2 3 rm wa o> m< © © 2 À mg 52 © mo aos n >» a> 4 > DC Dr >| [mS Sa ISS a az es eq} 5 Bo GO a INDIA OT hassel IVAVAVAVAVAVAVAVAVAVAVAVAWAWAAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAVAN Figure 18. to be the reason behind the accumulation (Romer, 1939; Hunt and Lucas, 1989) Stratigraphic range of B. maleriensis Roychowdhury (1965) suggested that the Maleri fauna is Carnian or early to middle Norian in age. Subsequently Kutty and Sengupta (1989) divided the Maleri fauna into two groups, a lower and an upper. The age of the lower group, which includes B. maleriensis, was stated as Late Carnian. The fauna associated with B. maleriensis chiefly consists of the phytosaur Parasuchus (Paleorhinus), the rhynchosaur Paradapedon, the theropod Alwalkeria, the protorosaur Malerisaurus, the cynodont Exeraetodon, an aetosaur and a large dicynodont. Hunt (1993), following the scheme of Lucas and Hunt (1989), put the lower Maleri fauna into the early part of the Late Carnian. The presence of Paleorhinus which is found from Tuvulian marine strata of Austria and stands as a good marker fossil in continental deposits, helped to infer this age (Hunt and Lucas, 1991). Lucas (1998), stated that palynostratigraphy, sequence stratigraphy and magnetostratigraphy of the Chinle Group indicate a Late Carnian age and the principal correlatives are the lower Maleri, Schilfsandstein, Kieselsandstein, and Stratigraphic ranges of metoposaurids and other associated temnospondyls of the Late Triassic Period. Blasensandstein of the German Keuper and the Argana fauna of Morocco. There is dispute also whether the lower Maleri fauna is early Late Carnian as stated by Hunt (1993) and Hunt and Lucas (1991) or late Late Carnian as stated by Kutty and Sengupta (1989). Hunt and Lucas (1991) predicted the age of the lower and upper Maleri faunas on the basis of phytosaurs. The Upper Maleri phytosaurs are yet to be described in detail. Moreover, immediately above the upper Maleri the Lower Dharmaram fauna (Kutty and Sengupta, 1989) also has an undescribed phytosaur and one or more aetosaurs. Bandyopadhyay and Roychowd- hury (1996) noted that Rutiodon-like phytosaurs are found only from the upper Maleri and the age of the immediately overlying lower Dharmaram could be Late Norian. This suggests an Early Norian age for the upper Maleri fauna confirming the late Late Carnian age of the lower Maleri fauna occurring immediately below. Hence, it is likely that the last appearance datum of B. maleriensis is late Late Carnian. Except in North America all metoposaurids were re- stricted to the Carnian. In North America, the Dockum Formation of Western Texas, Bull Canyon and Redonda Formations of Eastern New Mexico, the Painted Desert Member of the Petrified Forest Formation and the Owl Indian metoposaurid amphibians revised 63 Rock Formation of northeastern Arizona have metopo- saurids younger than Carnian in age. The post Carnian metoposaurid, Apachesaurus, is not abundant compared to the Carnian occurrences (Hunt, 1993). From the South- western United States, Long and Murry (1995) noted “a definite replacement of large metoposaurids by smaller ones” during the Early Norian. No small temnospondyls like Apachesaurus (Hunt, 1993) and Latiscopus (Wilson, 1948) from North America or Almasaurus (Dutuit, 1976) from Morocco are found in the Late Triassic deposits of Europe or India. On the other hand, no brachyopid temnospondyl, with parabolic skull and deep palate with downturned pterygoids, has been described from the North American Late Triassic (Figure 18). Such temnospondyls are represented in Europe by the plagiosaurids (Kuhn, 1932; Milner, 1994) and in India by the chigutisaurids (Sengupta, 1995). Paleoposition of India and aspects of paleogeography, paleoclimate and faunai migration Metoposaurids are restricted chiefly to latitude 40 to 60 North, with the exceptions being the Indian occurrences. The distance of the latter from the other localities was, however, minimised to some extent by the union of the continents during the Late Triassic. On the other hand, chigutisaurids are thought to have originated in Australia (Warren and Hutchinson, 1983) and are so far found to be restricted to Gondwana. India is the only place where metoposaurids were replaced by the chigutisaurids. This has led to some interesting observations on the paleoposi- tion of India and some aspects of paleoclimate, paleoge- ography and faunal migration. The absence of endemism among the Late Triassic Indian tetrapods has long been known (Colbert, 1958; Chatterjee and Hotton, 1986). Cox (1974) noticed that the similarity coefficient of Indian fauna with that of North America and Europe is quite high (59% and 81% respec- tively). On the other hand that with Africa and South America is also not negligible (75% and 56%). Smith and Briden (1977; map 13, p. 24) have shown that, during the Triassic, Australia was close to India and so were Europe and North America. The circum-Tethyan shoreline is short and curved and the position of Africa was such that the land distance between India and North America was minimal. The figures shown by Hay et al. (1982) indicate the position of India was almost halfway between North America and Australia at the end of the Triassic. Cox (1974) noted that in the Triassic there were no major climatic barriers. Robinson (1973) postulated a sharply seasonal rainfall in parts of North America, Europe, Africa and India during the Triassic (Robinson,1973, fig.10). Parrish et al. (1982, fig. 5, p. 39) have also shown that dur- ing Induan time a low pressure belt was located in Africa with an adjacent high in the north of India and another one in Europe causing a similar type of wind flow in the areas close to the Tethys. The entire area had 100 to 200 units of rainfall (Parrish et al., 1982) without any major climatic barrier. The Late Triassic metoposaurids could have come from Laurasia along the circum-Tethyan shoreline to India as a geographically peripheral group (this could also sup- port the contention that the Indian metoposaurid, B. maleriensis, is a distinct taxon). Chigutisaurids, on the other hand, arrived later, either from Australia or South America. Acknowledgements The work was part of the integrated research programme of the Pranhita -Godavari valley carried out by the Geological Studies Unit, Indian Statistical Institute, Calcut- ta. The field work was funded by the Institute. The specimens were collected by many workers of the Institute. T. Roychowdhury and T. S. Kutty collected and prepared many of the specimens and so did D. Pradhan and Shiladri Das of the Geological Studies Unit (GSU). I am thankful to T. Roychowdhury for critically going through the manu- script. A. Warren of La Trobe University, Victoria re- viewed the manuscript and helped to improve it. She and A. Milner of Birkbeck College, London, also helped in rec- ognizing certain taxonomically important characters of the metoposaurids. References Bandyopadhyay, S. and Roychowdhury, T. 1996: Beginning of the continental Jurassic in India: A paleontological approach. In, Morales, M. ed., Continental Jurassic. Museum of Northern Arizona Bulletin 60, p 371-378. 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A., 1948: A small amphibian from the Triassic of Howard County, Texas. Journal of Paleontology, vol. 22, no. 3, p. 359-361. Zittel, K. A. von., 1888: Handbuch der Paläontologie Abteilung 1. Paläozoologie Band Ill. Vertebrata (Pisces, Amphibia, Reptilia, Aves), 900 p. R. Oldenbourg, Munich and Leipzig. Paleontological Research, vol. 6, no. 1, pp. 67-72, April 30, 2002 © by the Palaeontological Society of Japan Permian bivalves from the H. S. Lee Formation, Malaysia KEIJINAKAZAWA 28-2 Koyama Shimouchikawara-cho, Kita-ku, Kyoto, 603-8132, Japan Received 2 July 2001; Revised manuscript accepted 7 December 2001 Abstract. Three bivalve species collected from the Permian H. S. Lee Formation at the H. S. Lee No. 8 Mine in Perak, Malaysia are described. They are identified as Sanguinolites ishii sp. nov., Megalodon (Megalodon) yanceyi sp. noy., and Myalina (Myalina) cf. wyomingensis (Lea). The fossil locality is famous for the abundant occurrence of gastropods together with bivalves, cephalopods, calcareous algae and others, but is flooded and inaccessible now. Permian. The new species of Megalodon is considered to be the first record of the genus in the Key words: H. S. Lee Formation, Malaysia, Megalodon, Permian bivalves Introduction and previous research The bedrock of open-pit tin mines in the Kampar area, Perak, Malaysia is mostly composed of carbonate rocks, such as limestone, dolomitic limestone, and dolomite. The fossiliferous limestone beds occupying the uppermost inter- val of this sequence occur in the H. S. Lee and Nam Long Mines, and were named the H. S. Lee Beds by Sunthralin- gam (1968). The rich Permian fossils collected from the H. S. Lee Mine (mostly No. 8 Mine, the type locality of the formation) are described by various authors. They were first reported by Jones, Gobbett, and Kobayashi in 1966, then by Suntharalingam (1968). In addition to abundant and diverse gastropods, common bivalves, cephalopods, scaphopods, brachiopods, chitons, corals, sponges and cal- careous algae were listed. Fusulinids were reported by Ishii (1966), calcareous algae by Elliot (1968), Prodenta- lium by Yancey (1973), one chiton and 91 gastropod spe- cies in 52 genera by Batten (1972, 1979, and 1985), and two ammonoid species by Lee (1980). Concerning the bivalves, the morphology and taxonomic position of large bizarre shells of alatoconchid bivalves were discussed by Runnegar and Gobbett (1975), Boyd and Newell (1979), Yancey (1982), Yancey and Boyd (1983), and Yancey and Ozaki (1986). Ten other bivalve species were described by Yancey (1985). According to Runnegar and Gobbett (1975) and Yancey (1985) molluscan fossils are abundant in the upper 15 m of the formation. A 3- 5 m-thick alatoconchid zone is sandwiched between gastro- pod-rich limestones. Bivalves are mainly contained in the alatoconchid zone and are not common in the gastropod- rich limestones. Ten species of bivalves belonging to eight genera are enumerated in Yancey (1985): Grammatodon (Cosmetodon) obsoletiformis (Hayasaka) Grammatodon (Cosmetodon) sp. Shikamaia perakensis (Runnegar and Gobbett) Saikraconcha (Dereconcha) kamparensis Yancey and Boyd Saikraconcha (Dereconcha) sp. Prospondylus chintongia Yancey Pernopecten malaysia Yancey Palaeolima sp. Lyroschizodus sp. Permartella quadrata Yancey The age of the H. S. Lee Formation is confirmed by fusulinids and ammonoids. The upper part of the forma- tion contains the fusulinid Misellina claudiae and the lower part contains Pseudofusulina kraffti (Ishii, 1966). Accord- ing to Runnegar and Gobbett (1975), Pseudofusulina kraffti is found 10 m below the alatoconchid beds. Ishii corre- lated both fusulinid intervals to the Misellina subzone (the lower subzone of the Parafusulina zone) in South China (Sheng, 1963), and the Misellina claudiae zone in Japan, which was considered to be equivalent to the Pseudofusu- lina ambigua zone and P. kraffti zone by Kanmera (1963). Based on these fusulinids the age of the H. S. Lee Formation is assigned to the late Bolorian in the Tethys or the late Kungurian Stage in the Urals and probably corre- lates with the late Leonardian in the United States. Lee (1980) identified three ammonoid species in the H. S. Lee Formation, Adrianites cf. insignis Gemmellaro, Neocrimi- tes cf. guanxiensis Chao and Liang, and Prostacheoceras skinneri Miller, and considered the age of the formation to be Artinskian or early Guadalupian (probably late Artin- skian). The fossil evidences of both groups indicates an age of latest Cisuralian (Early Permian) or early Guadalu- 68 Keiji Nakazawa THAILAND MALAYSIA e Ipoh # Kampar 4° Kuala Lumpur 0° 104° 100° Figure 1. Index map showing the fossil locality (asterisk). pian (Middle Permian) of the three-fold division of the Permian (Wardlaw, 2000). Yancey (1985) pointed out the close similarity of the bi- valve assemblage to that of the Akasaka Limestone in cen- tral Japan, which contain Shikamaia akasakensis Ozaki, Grammatodon obsoletiformis (Hayasaka), Lyroschizodus japonicus (Hayasaka) and others. The Akasaka Limestone is one of the members of the accretionary complex believed to be shifted from the tropical region (Nakazawa, 1991). It ranges from the Parafusulina Zone up to the Codono- fusiella-Reichelina Zone. The above-mentioned bivalves are found in the Neoschwagerina Zone (Murgabian). Accordingly, the Malaysian fauna is a little earlier in age than that of the Akasaka Limestone fauna. The materials examined in the present paper were col- lected by Ishii from the horizon just above the alatoconchid zone at the H. S. Lee No. 8 Mine (Figure 1). They are part of a collection given to Kyoto University in 1970, which contains the type specimen of Prospondylus chintongia described by Yancey (1985). In addition, Sanguinolites ishii sp. nov., Megalodon (Megalodon) yanceyi sp. nov., Myalina (Myalina) cf. wyomingensis (Lea), Permartella quadrata Yancey, and Grammatodon (Cosmetodon) obso- letiformis (Hayasaka) are identified in the collection. The first three taxa are described below. The occurrence of Megalodon is most remarkable, because the genus has not previously been reported in the Permian. Furthermore, the H. S. Lee No. 8 Mine was flooded and the exposures are no longer accessible (Runnegar and Gobbett, 1975). There- fore, the above-mentioned species are worthy of descrip- tion. All the specimens are kept at the Kyoto University Museum. Systematic description Order Pholadomyoida Newell, 1965 Family Grammysiidae S. A. Miller, 1977 Genus Sanguinolites M’Coy, 1844 Sanguinolites ishii sp. nov. Figure 2A, B Materials.—A pair of incomplete right and left valves, holotype HP100027. Etymology.—Dedicated to Ken-ichi Ishii who collected the fossils and offered them to Kyoto University. Diagnosis. — Large Sanguinolites with posteriorly ex- panded shape, weak ventral sinus, and relatively weak umbonal ridge. Description.—Shell large, equivalve, inequilateral, elon- gate, trapezoidal, more than 115 mm long, 45 mm high, and about 15 mm deep, more than twice as long as high, a little expanded posteriorly; umbo subdued, prosogyrate, slightly projecting above hinge margin, lying at anterior one-fifth of shell length; umbonal ridge weak, rounded, becoming ob- solete with growth; hinge line straight, ventral margin weakly sinuous, anterior margin well rounded, and poste- rior margin truncated with rounded posteroventral corner; lunule deep and narrow; escutcheon probably absent; long, opisthodetic ligament well preserved; hinge edentulous; surface covered with weak, sometimes rugose, growth lines. Anterior and posterior gape of shell uncertain. Discussion.—A part of the anterior area and the postero- ventral area in the left valve are not preserved, and only part of the dorsal margin of the right valve is visible. However, the general shape can be judged by growth lines. The dorsal margin of the shell is thickened and contains a shallow furrow which receives the external ligament. Although the escutcheon is not observed and the concentric sculpture is weak, the present specimen is considered to be- long to the genus Sanguinolites based on the other charac- teristics, such as elongate outline, very anteriorly located umbo, presence of umbonal ridge, long opisthodetic liga- ment, edentulous hinge, and concentric ornament. This species is similar in shape to Sanguinolites kamiyas- sensis Nakazawa and Newell (1968, p.42, pl. 11, figs. 3, 4) reported from the lower Middle Permian in Japan, but dif- fers in its much larger size, weaker umbonal ridge and the absence of radial ornaments on the posterodorsal area. Permian bivalves from Malaysıa 69 Figure 2. right valves, both in natural in size. L = calcified ligament. The Upper Devonian Sphenotus (= Sanguinolites) tiogensis McAlester (1962, p. 62, pl. 26, figs. 1-14) is more similar to the present species in shape and size, but is distinguished from the latter in its stronger rugose concentric sculpture. Order Hippuritoida Newell, 1965 Superfamily Megalodontoidea Morris and Lycett 1853 Family Megalodontidae Morris and Lycett, 1853 Genus Megalodon Sowerby, 1827 Subgenus Megalodon Sowerby, 1827 Megalodon (Megalodon) yanceyi sp. nov. Figures 3A-C, 4A-F A,B. Sanguinolites ishii sp. nov., holotype (HP 100027). A. Left valve, lateral view; B. Oblique dorsal view of joined left and Materials. — Nearly complete, left and right valves. Right valve, holotype HP100025; left valve, paratype HP100026. (After the manuscript was accepted, the pos- teroventral part of the holotype specimen was accidentally damaged as shown in Figure 4A-C). Etymology.—Dedicated to Thomas Yancey for his con- tribution to the study of the molluscs of the H. S. Lee Formation. Diagnosis.—A Permian species of Megalodon character- ized by relatively unmodified cardinal hinge, and one poterior lateral tooth in the left and two in the right valve. Description.—Shell medium in size, equivalve, inequilat- eral, subtrigonal in shape, inflated, spirogyrate, strongly carinate posteriorly with a sharp umbonal ridge; angle be- 70 Keiji Nakazawa Figure 3. Sketch showing the hinge of right valve, x1.5, Abbreviations: 3a and 3b, anterior and posterior cardinal teeth; III and V, posterior lateral Megalodon (Megalodon) yanceyi sp. nov. A. teeth; L. ligament. B, C. Holotype specimen (HP100025) before damage, B, x1.0, C, x1.0. tween posterior area and flank of shell about 90°; posterior area having a weak radial furrow; hinge plate thick, hinge of right valve consisting of a strong, trigonal, anterior car- dinal tooth (3a) with a weak radial groove, a very weak, ru- dimentary, posterior cardinal tooth (3b), and two, long, posterior lateral teeth (III and V) running parallel to pos- terodorsal margin; cardinal area of left valve poorly pre- served, but judging from cardinal sockets of left valve, hinge of right valve consisting of a round, anterior cardinal tooth (4a) and a strong, trigonal, posterior cardinal tooth (2) with uneven surface and a posterior lateral tooth (IV) which is inserted between two posterior lateral teeth of right valve and continues into wide nymph; ligament external, opisthodetic, well preserved; surface of both valves covered with dense growth lines; muscle scars not observed. Discussion .—The dental formula (Bernard, 1895) of the present species is shown as 3a 3b III V 4a 2 IV The external shape and the dentition indicate that this spe- cies belongs to Megalodon (Megalodon) Sowerby (the type species of the genus is a Devonian species, M. cucullatus Sowerby; see Newell, 1969, N743 m, fig. E215-4). The details of dental features of the genus are rather variable. The Malaysian species is especially similar to Megalodon (Megalodon) abbreviatus (von Schlotheim) (= cucullatus) described by Haffer (1959, p. 149, fig. 6; p. 150, pl. 12, figs. 13, 14), who discussed the hinge character of the genus in detail. However, the cardinal plate of the de- scribed species is less robust and the cardinal hinge is less modified than the latter. Measurements.—Right valve, HP100025, length 39.0 mm, height 31.0 mm, umbonal length from anterior end of shell 8.0 mm, depth 13.0 mm, height/length ratio 1.26, depth/length ratio 0.26, maximum shell length 41.0 mm; left valve, HP100026, length 40.0 mm, height 32.0 mm, umbonal distance from anterior end of shell 9.0 mm, depth 15.0 mm, height/length ratio 1.25, depth/length ratio 0.23, maximum shell length 42.0 mm. Order Pterioida Newell, 1965 Suborder Pteriina Newell, 1965 Family Myalinidae Frech, 1891 Genus Myalina de Koninck, 1842 Subgenus Myalina de Koninck, 1842 Myalina (Myalina) cf. wyomingensis (Lea,1853) Figure 4G, H Compared with. — Modiolus wyomingensis Lea, 1853, p. 205, pl. 20, fig. la. Myalina wyomingensis (Lea). Girty, 1903, p. 422, pl. 8, figs. 8- 13. Myalina (Myalina) wyomingensis (Lea). 3, figs.1-4, 7, 10; pl. 7, fig. 6. Newell, 1942, p. 49, pl. Material.—One nearly complete left valve, HP100028. Description.—Shell medium in size, prosocline, chang- ing in shape from Promytilus type to Myalina type through ontogeny; highly vaulted, umbonal ridge prominent and rounded with umbonal angle increasing from 45° in early growth stage to 75° in adult; 35 mm long, 37 mm high, and 17 mm deep, greatest dimension 43 mm; anterior lobe well developed, anterior margin slightly sinuated, hinge margin straight and nearly equal to shell length; surface covered with close-set growth lines, occasionally developed into la- mellae; hinge unknown. Discussion.— Although the hinge of the shell cannot be observed, the present species is quite similar to Myalina (Myalina) wyomingensis (Lea) found from the Desmoinesi- an to Wolfcampian in the United States, and it is difficult to separate the two species from each other based on the external shape, but the Malaysian species seems to be less oblique and a little higher than the American M. wyomin- gensis. Permian bivalves from Malaysia 71 Figure 4. A-F. Megalodon (Megalodon) yanceyi sp. nov. HP 100025) after damage. Calcified ligament is observed in both balves. G, H. (HP100028). All figures x1.5. Acknowledgments I am very grateful to Ken-ichi Ishii of the Hayashibara Natural Science Museum, who collected the materials and offered them to Kyoto University. Norman D. Newell of the American Museum of Natural History read the draft and gave me instructive comments. Thanks are also ex- tended toTakeshi Irino of Kyoto University and S. Suzuki of the Hayashibara Natural Science Museum, who helped in preparing the photos of the fossils. Ishii gathered many small gastropod shells in addition to bivalves. These were examined and identified by Roger L. Batten (then Ameri- can Museum of Natural History) and are also kept at the Kyoto University Museum. I wish to take this occasion to Myalina (Myalina) cf. wyomingensis (Lea). Posterior (A), lateral (B), and interior (C) views of right valve of the holotype Posterior (D), lateral (E), and interior (F) views of left valve of the paratype (HP 100026), cardinal area poorly preserved. Lateral (G) and anterior (H) views of left valve my gratitude to him. Lastly, I appreciate reviewers’ valu- able suggestions and refinement of my English. References Batten, R. L., Malaysia. Part 1. pleurotomarians. Bulletin of the American Museum of Natural History, vol. 147, article 2, p. 1-44, figs. 1-52 Batten, R. L., Part 2. The trochids, patellids and neritids. American Museum Novitates, no. 2685, p. 1-26, figs. 1-33 1972: Permian gastropods and chitons from Perak, Chitons, bellerophontids, euomphalids and 1979: Permian gastropods from Perak, Malaysia. Batten, L. R., 1985: Permian gastropods from Perak, Malaysia. Part 3 The murchisoniids, cerithiids, loxonematids, and subulitids American Museum Novitates, no. 2829, p. 1-40, 72 Keiji Nakazawa figs. 1-62. Bernard, F., 1895: Premiere note sur le développement et la morphologie de la coquille chez les lamellibranches. Societe Géologique de France, Bulletin, vol. 23, pt. 3, p. 104-154. Boyd, D. W. and Newell, N. D., 1979: Permian pelecypods from Tunisia. American Museum Novitates, no. 2686, p. 1-22, figs. 1-23. Elliot, G. F., 1968: Three new Tethyan Dasycladaceae (calcareous algae). Palaeontology, vol. 11, pt. 4, p. 491-497. Girty, G. H., 1903: The Carboniferous formations and faunas of Colorado. United States Geological Survey, Professional Paper, no. 16, p. 1-544, pl. 1-14. Haffer, J., 1959: Der Schlossbau früheterodonter Lamellibranchi- aten aus dem rheinischen Devon. Palaeontographica, Abtei- lung A, vol. 112, p.133-192, pls. 11-14. Ishii, K., 1966: Preliminary notes of the Permian fusulinids of H. S. Lee Mine no. 8 Limestone near Kampar, Perak, Malaysia. Journal of Geosciences, Osaka City University, vol. 9, article 4-VI, p. 145. Kanmera, K., 1963: Fusulinids of the Middle Permian Kozaki Formation of Southern Kyushu. Memoirs of the Faculty of Sciences, Kyushu University, Series D, vol. 15, no. 2, p. 79- 141, pls. 1-19. Lea, I., 1853: On some new fossil molluscs in the anthracite seams of the Wilkes-Barre coal formation. Philadelphia Academy of Natural Science, Journal, vol. 2, p. 203-206, pl. 20. Lee, C., 1980: Two new Permian ammonoids from Malaysia. Geology and Palaeontology of Southeast Asia, vol. 21, p. 63- 72. McAlester, A., 1962: Upper Devonian pelecypods of the New York Chemung Stage. Bulletin of the Peabody Museum of Natural History, no. 16, p. 1-88, pls. 1-32. Nakazawa, K., 1991: Mutual relation of Tethys and Japan during Permian and Triassic time viewed from bivalve fossils. Jn, Kotaka, T. et al.,eds., Shallow Tethys 3, Saito Ho-onkai Special Publicaiton, no. 3, p. 3-20. Nakazawa, K. and Newell, N. D.,1968: Permian bivalves of Japan. Memoirs of the Faculty of Science, Kyoto University, Series Geology and Mineralogy, vol. 35, no. 1, p. 1-106, pl. 1-11. Newell, N. D., 1942: Late Paleozoic pelecypods: Mytilacea. State Geological Survey of Kansas Bulletin, vol. 10, part 2, p. 1-80, pls.1-15. Newell, N. D., 1969: Superfamily Megalaodontacea. In, Moore, R.C.,ed. Treatise on Invertebrate Paleontology, Part N, vol. 2, Mollusca 6, Bivalvia, N742-749. The Geological Society of America and University of Kansas, Lawrence. Runnegar, B. and Gobbett, D., 1975: Tanchintongia gen. nov., a bi- zarre Permian myalinid bivalve from West Malaysia and Japan. Palaeontology, vol. 18, no. 2, p. 315-322. Sheng, J. C., 1963: Permian fusulinids of Kwangsi, Kueichou and Szechuan. Palaeontologia Sinica, New Series, vol. 10, p. 1- 115, pls. 1c.-36. Suntharalingam, T., 1986: Upper Palaeozoic stratigraphy of the area west of Kampar, Perak. Geological Survey of Malaysia Bulletin, vol.1, p. 1-15. Wardlaw, B., 2000: Notes from the SPS Chair. p.1-3. Yancey, T. E., 1973: Apical characters of Prodentalium from the Permian of Malaysia. Malaysian Journal of Science, vol. 2 (B). p. 145-148. Yancey, T. E., 1982: The alatoconchid bivalves: Permian analogs of modern tridacnid clams. Third North American Paleontologi- cal Convention Proceedings, vol. 2, p. 589-592. Yancey, T. E., 1985: Bivalvia of the H. S. Lee Formation (Permian) of Malaysia. Journal of Paleontology, vol. 59, no. 5, p. 1286- 1297. Yancey, T. E. and Boyd, D. W., 1983: Revision of the Alatocon- chidae: a remarkable family of Permian bivalves. Palaeon- tology, vol. 26, part 3, p. 497-520, pls. 62-64. Yancey, T. E. and Ozaki, K., 1986: Redescription of the genus Shikamaia, and clarification of the hinge characters of the fam- ily Alatoconchidae (Bivalvia). Journal of Paleontology, vol. 60, no. 1, p. 116-125. Permophiles, 37, Paleontological Research, vol. 6, no. 1, pp. 73-83, April 30, 2002 © by the Palaeontological Society of Japan Systematic position and palaeoecology of a cavity-dwelling trilobite, Ityophorus undulatus Warburg, 1925, from the Upper Ordovician Boda Limestone, Sweden YUTARO SUZUKI Department of Biology and Geosciences, Faculty of Sciences, Shizuoka University, 836 Ohya, Shizuoka, 422-8529, Japan. (e-mail: sysuzuk @ipc.shizuoka.ac.jp) Received 2 August 2001; Revised manuscript accepted 7 December 2001 Abstract. The high level systematic position and autecology of the Upper Ordovician cavity-dwelling trilobite Ityophorus undulatus is discussed. The lectotype is here selected from syntypes. The Late Cambrian family Loganellidae Rasetti, 1959 appears to contain the ancestors of this species. IJtyophorus is compared with the closely related Middle Ordovician trilobite Frognaspis to pick out the stable characters. These are the yoked free cheeks, the wide cephalic doublure in combination with a distinct narrow cephalic rim, pygidial pleural and interpleural furrows, and a smooth mesial part of the inner cephalic doublural margin (lack of an embayment of the hypostomal suture). Because of the presence of several characteristics unique to the two, they are best attributed to a subfamily Ityophorinae, which is interpreted as a relict group of the Loganellidae. The discussion of the autecology is based on the structural relationship of the mouth opening and position of basal podomeres in relation to the cephalic margin, and on the functional morphology of terrace lines on the brim margin. The appendages appear to have been long to reach the substrate. The cephalon appears to have held the body rigidly by means of the terrace lines. This made it possible for the animal to use its ap- pendages freely, for instance, in scratching the substrate. Some cavities in the present study area show evi- dence of a gel-like consistency of the cavity walls, which best fits the behavior mentioned above. /tyophorus is interpreted to have been an animal adapted to cavities rich in bacterial mats, on which it may have fed. Key words: cavity dwelling, Ityophorus undulatus, life habit, Loganellidae, structural relationship, Trilobita, yoked free cheeks. Introduction The term “cryptic habit” denotes an adaptations into a buildup environment, which usually provides cohesive sub- strates with the potential to provide cavities. Caves in re- cent reefs, which offer spaces for cryptic modes of life, occasionally are dominated by sponges and cryptic bacteria (Reitner, 1993). With these, bivalves, gastropods and ar- thropods form cryptic biotopes. From a classificatory point of view, some cavity-dwelling metazoans appear to be phylogenetically relict groups (relict biota), or groups which retain primitive morphological characters (Hayami and Kase, 1996; Hobbs, 2001). This trend should have been characteristic also of ancient cavity dwellers in buildups, although no vagile metazoan fossil group has ever been recognised as a “relict group” so far. The Upper Ordovician minute trilobite species Ityophorus undulatus Warburg, 1925, which is of uncertain position in high-rank systematics (Kaesler, 1997, p. 302), is commonly found in patches of internal sediment in autochthonous taphonomical conditions (Suzuki and Bergs trom, 1999, fig. 10), commonly associated with micro- gastropods. The sediment is characteristic of the “stroma- tactis cavity” system which is a common sedimentary struc- ture in Palaeozoic carbonate mud mounds. Thus Suzuki and Bergström (1999) concluded that the present species was a cavity dweller. This rare mode of occurrence, which is defined correctly as a cavity setting, offers us an unusual chance to examine if a fossil species of cryptic habit has a similar mode of adaptation to recent examples or not. The aims of the present study are to examine the high- rank systematic position of /tyophorus undulatus, to present an example of morphological transformations in a trilobite caused by environmental pressure, and to discuss the autecology from functional and sedimentological points of view. Geological setting Ityophorus undulatus occurs in the Upper Ordovician Boda Limestone, Siljan district, Sweden. This unit 74 Yutaro Suzuki ss Fer + Kallholn Orsa Q Siljan ¥ Osmundsberget 8 pa 2 À Boda > Solberga & ; EN x d- ue N 2 Ostbjörka @’ Jutjärn fi ) f Rs ® Lake Siljan @ Boda Limestone El Ordovician - Silurian Systems 20 km —=_ | Figure 1. Locality map of some Boda Limestone bodies. consists of a set of carbonate buildup masses of which now up to 20 are known in the Siljan district of Sweden (Figure 1; Jaanusson, 1979). The thickness and the diameter of an isolated Boda Limestone body are said to be about 100-140 m and up to over 1 km, respectively (Jaanusson, 1982). However, my own observations and calculations based on a topographic map indicate a maximum size more or less half the dimension mentioned. The facies is massive pure limestone without obvious bedding, but with frequent open space structures such as stromatactis cavities and synsedi- mentary dykes. Ityophorus undulatus is commonly found with internal sediment in relatively large open space struc- tures. On the rim of these, a unique type of open space structure is often recognised, shown in Figure 2B. Micro- scopically, internal sediment is dominated by peloids, and the host sediment is micritic (Figure 2D). In case of the Boda Limestone, “normal” stromatactis structures differ considerably both macroscopically and microscopically (Figure 2A, D; or readers are referred to Pratt, 1995, p. 63, fig. 14G). The internal sediment in stromatactis cavities and host sediments of the cavity system is mostly micro- crystalline, and peloids are rare. The transversely elongate cavity system with peloids which is similar in construction to that shown in Figures 2B and 2D is generally classified as “zebra cavity of laminoid or flat stromatactis type” (for definition, see Monty, 1995, p. 25), and is interpreted as originating by the decay of superposed thin sheet-like mi- crobial mats (Pratt, 1982). Systematic description The present species was originally described in detail by Warburg (1925, p. 229). General characters and new ob- servations are presented below. Genus Ityophorus Warburg, 1925 Type species.—Ityophorus undulatus Warburg, 1925 Ityophorus undulatus Warburg, 1925 Figure 3 Ityophorus undulatus Warburg, 1925, p. 229, pl. 11, figs. 40-43; Moore, 1959, p. 0430, fig. 333; Nikolaisen, 1965, p. 237. Types.—3 syntypes, PMU D194 (Warburg, 1925, pl. 11, fig. 40), PMU D195 a, b (Warburg, 1925, pl. 11, fig. 41) and PMU D196 (Warburg 1925, pl. 11, figs. 42, 43), are housed in the Palaeontological Institute, University of Uppsala. PMU D196 is here selected as the lectotype. Type locality.— Boda Limestone, a buildup mass in Kallholn, Dalarna, Sweden. The stratigraphic level within the mass is unknown. The range of the species is likely to correspond to the Cautleyan to Rawtheyan stage of the Ashigill series, and not the Hirnantian. Repository. — All the specimens figured herein are housed in the Swedish Natural History Museum, Stockholm, with “RM” numbers. Description.—The entire exoskeleton is ovate in outline (Figure 3A). Its entire length seldom exceeds 1 cm. The cephalon occupies about half of the length, sagittally. The axis is fairly convex, and almost half of a circle in cross- section. The cephalon is horseshoe-shaped (Figure 3A) and strongly convex (Figure 3B). The maximum length in- cluding the genal spine is about twice the sagittal length and almost equal to the length of the entire body. The genal angle is acute. The long genal spine curves evenly posteriorly and adaxially. The width of the spine is almost constant throughout. Its posterior end is situated more or less at the level of the posterior end of the pygidium. The anterior cephalic rim, which is narrower and less convex than the posterior cephalic border, disappears where it meets the genal spine. Thus, the genal spine is seemingly an extension of the cephalic posterior border. The glabella is cylindroid in profile and expands slightly anteriorly. It is strongly convex transversely. Three pairs of glabellar furrows are recognised. The 2S and 3S furrows are short and extend more or less transversely. Their length is about one fourth the width of the glabella. The 1S furrow is longer than the 2S and 3S furrows. It is directed about 45° posteriorly from a transverse line. It becomes wider adaxially. Probably the furrow is bifurcated adaxially, but the specimens are too small for a definite observation. The eye ridge is short but strongly convex, and distinctly set off from the surroundings. It extends transversely in front of the level of the 3S glabellar furrows. The length of the eye ridge roughly equals the distance between the 2S Cavity trilobite /ryophorus undulatus 75 Macro- and microfacies of the Boda Limestone. Figure 2. nated internal sediment. continued white area pointed by black arrows are cavity systems. dicates microcrystalline internal sediment. are | cm. CC stands for cavity filling cement. and 3S furrow. There may be eyes, as described by Warburg (1925, p. 230). However, the structure described as the eye may be vestigial since it is not proven that there is a visual surface. The possible visual surface forms half a sphere. A median occipital tubercle is present anteriorly on the occipital ring. The peripheral genal area is steeply inclined. Five furrows extend in parallel with the narrow cephalic rim (Figure 3A). The outermost one is the furrow of the cephalic rim. The innermost one extends laterally and posteriorly from the anterior end of the glabella (Figure A. Polished slab of the core facies, vertical section. B. Polished slab of the “zebra cavity”, sampled from the rim of an open space structure. Vertical section. C. Microfacies of the core facies. D. Microfacies of the zebra cavities. White arrows indicate lami- Transversely White arrow in- All white scales Matrix is rich in bioclasts. Black arrows point to peloidal internal sediment. 3B, E; black arrows). The area between these furrows is moderately convex. The brim, here defined as the area outward of the fourth furrow described above, is broad. The undulating brim has a general dip sagittally from the inner to the outer margin of around 30° (Figure 3C). The dip gradually becomes steeper backwards to about 60° lat- erally. The facial sutures are of opisthoparian type. Their anterior branches enclose a parabolic anterior part of the cranidium (Figure 3E). obliquely backwards to cross the cephalic posterior border The posterior branch extends 76 Yutaro Suzuki Cavity trilobite /tyophorus undulatus ae at a right angle (Figure 3E; white arrow). The free cheeks are fused into a single unit, because no furrows or gaps are recognised on the cephalic doublure (compare dorsal and ventral cephalic views in Figure 31, J, respectively). The doublure closely follows the shape of the brim, and the space between the two is very narrow (Figure 3C). The doublure is wide (Figure 3C, J, L). The interior edge of the doublure (Figure 3L; white arrow) is situated below the innermost parabolic furrow in the cephalon, which is indi- cated by black arrows in Figure 3B, E. The cephalic doublure has three or four parabolic furrows which are al- most parallel to the cephalic margin (Figure 3J). An inte- rior part of the doublure, between the fourth and fifth parabolic furrow mentioned above, is steeply inclined and distinctly set off from the surrounding. Thus the cephalic doublural morphology is quite similar to the lower lamella of harpids. In the cephalic rim, terrace lines with an asymmetrical cross-section are recognised on both the dorsal and ventral side (Figure 3H). The steep surfaces of the ventral terrace lines face dorsally, whereas they face ventrally in the dorsal ones (for detail, see Figure 5). The hypostome is situated just below the glabella (Figure 31). Its anterior margin must have been in contact with the cephalic doublure mesially. Three specimens among hun- dreds of cephala show the same position of the hypostome. Thus the described position of the hypostome should be original. The length of the hypostome is 55% of that of the glabella (Figure 3D). It is strongly convex trans- versely. The maximum length is about 1.3 times longer than the maximum width. An anterior wing is relatively long (exsag.) and evenly inclined dorsally. The distal part of the wing is broadly rounded. The anterior margin is slightly depressed medially. The lateral border is narrow and short. The border furrow extends from the level of the posterior end of the anterior wing to four-fifths of the ante- rior end of the hypostome. The shoulder is triangular in shape and horizontally extended (Figure 3D; white arrow). The posterolateral corner of the central body is angulate. The posterior margin is convex without a border. No dis- tinct boundary separating the anterior and the posterior lobes is recognised. The central body is longitudinally el- liptic in shape. The thorax consists of six segments (Figure 3A). The axis gradually becomes narrower backwards. The ratio between axial and pleural widths ranges from | to 1.2 from in front to the rear. The pleurae extend almost straight transversely except for the posteriormost two segments, in which the pleurae distal to the geniculation curve moder- ately backwards. A distinct pleural furrow is present. It extends almost parallel to the anterior and posterior margins of the segment. The pygidium is wide (Figure 3A). The maximum width/length ratio is about 1.9. Six axial rings and five pairs of pleural ribs are discernible. Distal to the fulcrum, pleural ribs and furrows curve gently backward. Pleural and interpleural furrows lie parallel with each other. The posterior end of the axis is obscure. It gradually dies out posteriorly. A narrow flattened border is present. Specimens of a younger growth stage, a meraspid de- gree? (Figure 3F), and a transitory pygidium (Figure 3G) are available. Both specimens are found along with adult specimens in internal sediment. No other trilobite species is recognised in this sediment. The former specimen (Figure 3F) is most probably a moult, because it lacks the entire free cheek unit. The glabella is proportionally nar- rower than in the adult. The 2S furrow differs in its course from that of the adult. The abaxial end of the furrow does not reach to the axial furrow. The furrow is directed posteriorly and adaxially in the young specimen, but trans- versely in adults. The axial ring of the first thoracic seg- ment is seen posterior to the cephalon. A distinct eye ridge is present. Its proportion and position in relation to the glabella is almost the same as in an adult specimen. A most notable feature is the facial suture course. The ante- rior branch is not parabolic as in adult specimens, but ex- tends straight forwards. The transitory pygidium seems to have a spiny margin (Figure 3G; white arrow). The poste- rior extremity of the axis ends well in front of the margin. The preservation is not good enough to permit further ob- servations. Remarks. — Previously, Warburg (1925, p. 231) de- scribed the genal spine of the present species as being a short pointed spine. Because of the minute size of the spe- cies, it tends to be broken. In most of the cases the genal spine is recognised as a concave mould. + Figure 3. view. x17. Ityophorus undulatus Warburg, 1925. A. Complete exoskeleton, dorsal view. x18. Black arrow points to the furrow, below which the inward edge of the doublure is situated. Jutjarn. RM Ar 56890. B. Same, lateral C. Exsagittal or sagittal section of the cephalon. x39. Jutjärn. RM Ar 56891. D. Hypostome, ventral view. x54. Jutjärn. RM Ar 56892. White arrow points to the posterior wing, which is partly broken. points to the termination of the posterior branch of the facial suture. situated. F. Fairly young individual. x70. to pygidial spine. of hypostome and cephalic brim, dorsal view. x16. E. K. Occurrence pattern with microgastropods. x4. Same slab as E. J. White arrow points to the inner edge of the cephalic doublure. E. Cephalon, oblique lateral view showing curving facial suture course. x15. Specimen is in the same slab as G. L. Magnified cephalic doublure, ventral view. x45. Locality unknown. RM Ar 56893. White arrow Black arrow to the furrow, below which the inward edge of the doublure is Jutjärn. RM Ar 56894. G. Fairly young pygidium. x65. H. Magnified brim in cross section. x150. The lower brim of the two is upside down. Jutjärn. RM Ar 56896. Jutjärn. RM Ar 56895. White arrow points I. Ventral mould J. Cephalic doublure, ventral view. x12. Same slab as Specimen same as 78 Yutaro Suzuki Systematic position of /tyophorus undulatus Morphological characters of Ityophorus and Frognaspis For more than a half century, opinion on the high-rank classification of the present genus was far from a clear con- sensus. First, Warburg (1925) made a new family Ityophoridae consisting of only the present genus. Later in Moore (1959), the species was doubtfully classified as a member of the Trinucleina Swinnerton, 1915, of the order Ptychopariida without any demonstrated evidence. It is clear that the convex cephalon with horseshoe outline is just a superficially similar to a trinucleid cephalon. Nikolaisen (1965) described a new species, Frognaspis stoermeri, which is closely related to the present species, from the Middle Ordovician of Norway, and classified it into the Ityophoridae. Furthermore, he implied a neotenic development of the present species from Frognaspis stoermeri. As will be discussed in a later paragraph, Frognaspis stoermeri shares fairly many characters with the present species. The suggestion of a close relationship between the two is therefore convincing. However, Nikolaisen did not tackle the problem of the position of Ityophoridae. Fortey (1997) also gave up and simply stated that the family belongs to the Ptychopariida Swinnerton, 1915. Before examining the high-rank systematic position of the present species, we must understand how the unique morphology evolved in the phyletic lineage. Since Ityophorus undulatus preserves characters seen in young individuals of Frognaspis stoermeri, the heterochronic evo- lution of the former from the latter is worth consideration. After comparison of the two, we can sort out a “heterochr onic polish”. Then we can define stable characters and infer the ancestral conditions of characters which differ be- tween the two. In addition, one has to remember what kind of morphological changes would arise in a shift to cavity-dwelling habits in modern arthropods. Characters shared between Ityophorus undulatus and Frognaspis stoermeri are as follows: 1) wide cephalic brim. 2) facial suture course. 3) distinct furrows in the cephalic doublure. 4) small eyes. 5) fairly wide cephalic doublure with distinct narrow cephalic rim. 6) free cheeks forming single unit. 7) distinct pleural furrow (known only from the pygidi- um in the latter species). 8) narrow flattened pygidial rim. 9) pygidial pleural ribs distal to the geniculation extend obliquely backwards. 10) hypostomal morphology. 11) directions of pleural tips in the thorax. 12) cephalic doublural margin smoothly rounded mesially (no embayment for the hypostomal suture). Since the mesial part of the inner margin of the doublure is below the anterior extremity of the glabella, the hypostome should be attached to the doublure medially. Characters which are not shared by the two species are: 1) glabellar profiles (expanded in /ryophorus). 2) glabellar furrows (deepened adaxially and 1S fur- rows faintly connected over midline in Frognaspis). 3) number of segments in the pygidium. 4) ornaments on dorsal surfaces. The characters 1) and 2) in /tyophorus are apparently de- rived from younger growth stages of Frognaspis (see Nikolaisen, 1965, pl. 3, fig. 4). The inferred ancestral con- ditions of the two characters should thus be represented in the adult stages of Frognaspis. The ancestral glabellar character 1) should be preserved in the adult stage of Frognaspis. This is because the glabellar profile in /ryophorus is fairly similar to a younger stage of Frognaspis (Nikolaisen, 1965, p. 243). Thus the ancestral group should have had an anteriorly tapering glabella, and possibly the 1S furrows may have been con- nected mesially (non shared character 2). The latter situa- tion is recognised in Frognaspis. Determining the ancestral condition of character 3) is difficult. This is because the adult number of pygidial seg- ments is, in general, related to the number of thoracic seg- ments. Unfortunately, the exact number of thoracic segments is not known in Frognaspis. I can only say that the ancestral condition of the number of segments in the pygidium may vary between species in the high-rank group, in which the two species belong. Concerning character 4), since the exoskeletal ornament pattern is unstable among the genera in some family groups (e.g., Styginidae), we should hesitate to use that character in determining the high-rank systematic position. In gen- eral, recent cavity-dwelling organisms are equipped with specialized sensory organs. Especially in cavity-dwelling arthropods, the appendages tend to be long, which increases the area for the number or the size of sense organs (Culver, 1982, p. 17). Coarse tubercles on the exoskeletal surface in trilobites are generally understood as sensory ducts (Osmölska, 1975, p. 203). As will be discussed in a later paragraph, /tyophorus must have had long appendages, so the animal had the potential to equip its appendages rather than the dorsal exoskeleton richly with sensory organs. Thus smoothing of the dorsal exoskeletal surface may be a result of adaptation inhabiting cavities. Discussion of systematic position of Ityophorus I first try to narrow down candidate ancestral groups of Ityophorus from other groups with yoked free cheeks. Cavity trilobite Zryophorus undulatus 79 Next, I judge the possible relationships based on other char- acters such as ventral morphology, facial suture type, and pygidial morphology. Trilobite groups which possess yoked free cheeks are bathynotids and conocoryphids from the Lower to Middle Cambrian, Nileidae, Phacopida, Trinucleina, Harpina, Olenidae, Hypermecaspididae, some species of Dikelo- cephalidae such as Dikelocephalus retrorsus, Loganellidae, some species of Dikelokephalinidae (readers are referred to Dactylocephalus latus (Peng, 1990a, pl. 9, fig. 8) and Ciliocephalus angulatus (Peng, 1990b, pl. 17, fig. 3)), Harpididae and Entomaspididae. Of these, the Lower Cambrian groups are so different in several characters such as facial suture courses, pygidial morphology and ventral cephalic characters, that a phylogenetic relationship with Ityophorus or Frognaspis is most unlikely. Harpina and conocoryphids (marginal suture), Harpididae (marginal or characteristic proparian suture), Phacopida (proparian su- ture) are profoundly different in their facial suture types from that of Ityophorus. Among the rest, the Entomaspididae have a characteristic pygidial morphology (a narrow upturned (geniculated) border or stubby spines in front of a continuous pygidial rim: Ludvigsen er al. 1989, p. 47) which is unlikely of the ancestor of /tyophorus. Most of the Trinucleina do not have eyes with dorsal facial suture except some genera such as Orometopus which has opisthoparian facial sutures. However, the overall mor- phology, especially the pygidial morphology of trinucleid type is quite different from the /tyophorus pygidium with distinct border and posteriorly curved pleural and inter- pleural furrows. The Nileidae have a characteristic hypostome, cephalic and pygidial morphology, large eyes with no eye ridges, more or less straight pygidial furrows, all of which are unlikely in a relative of /ryophorus. The Olenidae and the Hypermecaspididae have yoked free cheeks. In the case of olenids and hypermecaspidids with a wide preglabellar field, the cranidium is similar in outline and the cephalic doublural margin smoothly rounded mesially as in /tyophorus, but the hypostomes become natant. Since the hypostome of Ityophorus and Frognaspis must have attached mesially to the cephalic doublural margin (shared character 12), their ancestor should have possessed this mode of hypostomal attach- ment. Moreover, the pleural and interpleural pygidial fur- rows of the Olenidae and the Hypermecaspididae extend obliquely posteriorly in a more or less straight way, which is different from the situation in /tyophorus. Therefore, a phylogenetic relationship between the Olenidae and Ityophorus is unlikely. Other candidates are the Dikelocephalidae, Dikelokepha- linidae and Loganellidae. Some species of the former two families, although not all, possess yoked free cheeks with a wide cephalic doublure. The pygidial morphology is also fairly similar between them. The Dikelocephalidae and the Loganellidae were extinct before the Cambrian- Ordovician transition, whereas the Dikelokephalinidae per- sisted beyond that boundary (Opik, 1967, p. 254). One could therefore think that the third group, the Dikelo- kephalinidae, might contain the ancestor of Ityophorus. Classifying the Dikelokephalinidae is usually difficult, be- cause most of the characters are too general to be diagnos- tic (Fortey and Chatterton, 1988, p. 209). However, the pygidium of Dikelokephalinidae has posteriorly curved pleural furrows but not interpleural furrows whereas Ityophorus has both. Thus, Dikelokephalinidae should not be related to /tyophorus. The Dikelocephalidae and the Loganellidae have interpleural furrows in their pygidia. However in the former, an embayment is present mesially in the cephalic doublure for an attachment of the hypo- stome. In contrast, the Loganellidae have a mesially smooth outline of the cephalic doublure (Moore, 1959, p. 0333) which is concordant with the ventral cephalic mor- phology in /tyophorus. Below I discuss the phylogenetic relations between the Loganellidae, and /tyophorus and Frognaspis. There are several shared characters between the Loga- nellidae and the two species such as the shared characters between /tyophorus and Frognaspis 1), 2), 5), 6), 7), 8), 9) and 11) listed above. Futhermore the characters of the in- ferred ancestral conditions which are listed as non-shared characters between /tyophorus and Frognaspis 1) and 2) fit well to this family. Generally, in species with the free cheeks in a single unit and a wide doublure, the cephalic rim [called a “border” in Fortey and Chatterton 1998: fig. 6, readers are referred to Whittington and Kelly (1997, p. 315) for the terminology of the “border” and “rim”] is of fairly low convexity (e.g., Fortey and Chatterton, 1988, fig. 6). Nikolaisen (1965, p. 237) stressed the differences in eye size and the hypostomal morphology in species be- tween loganellids and Frognaspis or Ityophorus, but the re- duction of eye size is a common feature in organisms adapted to cavities (Humphreys, 2000, p. 4). Anteriorly in the hypostome of /tyophorus and Frognaspis, there is a unique longitudinal median groove (Figure 3D; Nikolaisen, 1965, pl. 3, fig. 6). The groove structurally corresponds to the median longitudinal groove or depression (see Nikolai- sen, 1965, pl. 2, figs. 1, 3; pl. 3, figs. 1, 2) anteriorly in the Frognaspis glabella. In general, species with yoked free cheeks (e.g., Cloacaspis senilis: see Fortey, 1974, pl. 10, fig. 6) may or may not possess a similar longitudinal glabellar groove or depression. If present, the longitudinal groove in the glabella tends to be more weakly impressed in older growth stages (Fortey, 1974, fig. 6). Thus the groove is more or less an embryonic character. Hence the two latter genera are most likely descended from a species of the Loganellidae. However, there are still several facts 80 Yutaro Suzuki Ityophorus Figure 4. “X” in a circle), digestive tract (grey area), labrum and basal podomere. Modified from Sanders (1963: fig. 4) and Hessler and Elofsson (1992: fig. 3). doublure hypostome A. Schematic drawing of cephalocarid crustacean showing the structural relationship in basal appendage joints (represented as Positions of the joints are situated above the level of the mouth opening. B. Schematic drawing of Ityophorus undulatus showing structural relationship in inferred digestive tract (grey tube), hypostome and basal podomeres (represented as bricks). White arrows indicate dorsoventral level of mouth openings. which may differentiate Ityophorus and Frognaspis from typical Cambrian loganellids: 1) the two are Middle to Late Ordovician trilobites, 2) the body size of the two has under- gone considerable shrinking, 3) the presence of crescentic furrows in the doublure (shared character 3) in the two spe- cies, but not in Cambrian loganellids. Therefore, the two genera are best accounted for as a subfamilial group of the Cambrian Loganellidae. Ityophoridae Warburg, 1925, in- cluding Frognaspis and Ityophorus, is therefore down- graded to a subfamily Ityophorinae Warburg, 1925, of the family Loganellidae Rasetti, 1959. The Ityophorinae now appears to be a relict of the Late Cambrian group. Since growth stages are unknown in most fossil arthropods, how the Ityophorinae had evolved from a loganellidae as becomes vague. Recent animals, “progene- tic evolution” is quite common as part of a cryptic adapta- tion, and the considerable size decrease of the Ityophorinae in comparison with the Loganellidae may be one indication of “progenetic evolution”. Black double arrow indicates minimum distance between basal joints of appendages and the substrate. Functional morphology of Ityophorus undulatus The present species had attained a body with apparently a “snow-shoe” effect, which increases the area of the ani- mal substrate interface and prevents the animal from sink- ing into the substrate. A parallel is seen in harpid trilobites, although previous functional studies of these were restricted to the function of their characteristic brim. Unfortunately, we have no data on appendages in Ityo- phorus or harpid trilobites. It may be worth trying to infer the length and use of the legs from the space relationships between the probable attachment of the legs and the head shield, particularly its margin. This may give some hint of the mode of life. Elevation of leg insertion over substrate The hypostome of /tyophorus is oriented horizontally (Figures 31, 4). This means that the mouth opened back- wards, and not downwards. Recent crustaceans such as cephalocarids and notostracans a structure similar to the tri- lobite hypostome plus associated soft tissue is present, al- Cavity trilobite /tyophorus undulatus 81 though it is not homologous. This is the “labrum”. Ina crustacean with a labrum the digestive tract first extends forwards from the mouth. The tract then flexes in the head and continues backwards (Figure 4; see grey area in the cephalocarid), extending more or less straight to the anus. The digestive tract in /tvophorus should have followed the same course as in the cephalocarid crustacean (Figure 4; Ityophorus with digestive tube in grey). Actual evidence on such a digestive course in trilobies is reported in phacopid (Stürmer and Bergström, 1973, pl. 20) and trinucleid trilobites (Snadjr, 1987, fig. 3). In case of a crustacean with the mouth opening back- ward, there is an important structural relationship between the dorsoventral positions between the labrum and the basal podomeres. Since the mouth is directed backwards, food particles have to be transported mechanically (handled by appendages) or indirectly (handled by food collecting wave created by appendages) from back to front via the midvent- ral line. For transporting the food particles, the “labrum” and mouth must be situated below the level of the midvent- ral line posterior to the labrum. Since the line is higher than the labrum and the mouth, the basal podomeres, which are attached to the axial body, automatically are at more or less the same horizontal level as the mouth opening. Such a relationship is seen in three-dimensionally preserved Ceraurus (Walcott, 1881, pl. 2, figs. 1-3). In Ityophorus, the spatial relationship between hypostome and basal podomeres appears to have been identical (see white arrow in Figure 4B). Therefore, the basal podomeres must have been situated fairly high relative to the cephalic margin (Figure 4). This configuration forced the animal to de- velop long appendages simply to reach the substrate. As discussed earlier, this condition is a common feature in cav- ity-dwelling arthropods, and /tyophorus could probably rest with the brim on the substrate without using its appendages. This means that the appendages were free to be used for different aims such as food collecting. Relationship between brim and appendages In general, the morphology of the arthropod appendages directly influences the method of feeding. The combina- tion in /tyophorus of long legs surrounded by a brim form- ing a long “skirt” should have been of significance for the mode of life. As described above, the two sets of terrace lines are restricted to the edge of the brim, where the steep sides of each set face the other set (Figures 3H, 5). The lower set of terrace lines should have prevented the animal from sliding laterally outwards (Schmalfuss, 1981), while the inner set would hinder extensive sinking into the sub- Strate. When an appendage scratched the substrate in one direc- tion (Figure 5; black arrow with A), the body would be sub- jected to a pull in the opposite direction (Figure 5; black hypostome Figure 5. Schematic drawing of transversely sectioned cepha- lon (black arrow in top of the figure) with inferred appendage, show- ing the relationship of the action and reaction mechanics between the exoskeleton and the substrate when the animal was scratching. The rectangle shown in the right of the figure is the magnified cephalic rim with substrate. For more details, see text. Black arrow with A means the vector of action from exoskeleton to the substrate, black arrow with R of reaction from the latter to the former. arrow with R). This is determined by simple physical rules. Scratching or burrowing leg movements may also tend to pull animal downwards into the substrate. In Ityophorus, the terrace lines on the cephalic rim would hin- der the head shield from sliding sidewards or downwards (Figure 5; see magnification in left rectangle). Thus, for as long as the animal kept scratching, it could presumably move along inclined walls in a cavity. This mode of behaviour would work on a gel-like or sticky substrate such as a bacterial mat, the existence of which is suggested by the geological setting. Such a mode of life must require one more important factor, a low weight of the animal. Ityophorus was indeed unusually small and light. There- fore, I conclude that /tyophorus was most probably adapted to cavities coated with microbial mats. Some examples are known from Recent cavity-dwelling arthropods such as isopods which feed directly on fungi and bacteria (Sarbu and Popa, 1992). Epilogue The Late Ordovician trilobite /tyophorus undulatus ap- pears to have had a set of morphological characters charac- teristic of cavity dwellers, such as reduced eyes, long appendages relative to the body length, considerable dwarf- ing, and possible heterochronic development, which is most likely to be progenesis. The supposed ancestral group of the Ityophorinae, the Loganellidae, is thought to be extinct before the Cambrian-Ordovician transition. A relict group might have persisted into the Ordovician by “progenetic evolution”, and later adapted into a cryptic life. This is the first report that tries to interpret a phylogenetically relict fossil group as cryptic animals. 82 Yutaro Suzuki A Devonian proetid genus, Denemarkia (see Moore, 1959, 0397; Snajdr 1980, p. 146, pl. 37), was a possible cavity dweller (Alberti, 1969, p. 336) with an overall mor- phology similar to /tyophorus. Taphonomical evidence showing the entombment of Denemarkia specimens in a cavity is available (such an occurrence pattern is not illus- trated so far but a slab showing such a situation is stored in National Museum, Czech Republic, museum number L 16634). Denemarkia is known from the Devonian Konéprusy Limestone in Czech Republic (Snadjr, 1980) and the Kess Kess Limestone in Morocco (Alberti, 1969). Both limestone units are of the carbonate mud mound type of buildups. Interestingly, shared characters between Denemarkia and Ityophorus, such as fairly vaulted cephalon (see Moore, 1959, fig. 302-1b), distinct cephalic rim with wide cephalic doublure, lacking mesial embayment for the hypostomal suture (see Snadjr, 1980, pl. 27, fig. 9), a combination of which is quite rare in proetids, and less developed eye, are a fairly unique morphological combination in trilobites. A major morphological differ- ence between the two is that the dorsal exoskeleton of Denemarkia is fairly rich in tubercles, whereas /tyophorus is smooth, and this can be explained as a result of adapta- tion to cavities as discussed previously. Repeated body modifications into ityophorid-like morphology from com- pletely different clades means that there was a general ca- pacity in the Trilobita to evolve in this direction. Acknowledgements I thank two reviewers, B. D. E. Chatterton (University of Alberta, Edmonton, Canada) and P. Ahlberg (Lund Univer- sity, Sweden), for critically reading the manuscript and pro- viding constructive suggestions. I am grateful to J. Berg- strom (Swedish Museum of Natural History, Stockholm) for thorough discussions and the permission to examine museum collections. Helpful discussions of cavity organ- isms were conducted with T. Kase and Y. Kano (National Science Museum, Japan). I thank S. Stuenes (Uppsala University) for access to the type specimens. I also thank J. Slavickovä (National Museum, Prague) for sending me latex casts of Denemarkia, and for access to the specimens. This study was financially supported by the Grant-in-Aid for JSPS Research Fellow (No. 04015 in 2001-2003) from the Ministry of Education, Science, Sports and Culture, Japan. A bilateral scholarship of the Swedish Institute, and a scholarship of the Mitsubishi Shintaku Yamamuro memorial Fund are greatly acknowledged. 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Osmölska, H., 1975: Fine morphological characters of some Upper Palaeozoic trilobites. Fossils and Strata, vol. 4, p. 201-207. Opik, A. A., 1967: The Mindyallan fauna of North-western Queensland. Commonwealth of Australia, Bureau of Mineral Resources, Geology and Geophysics, Bulletin, 74, vol. 1, p. 1-404. Peng, S., 1990a: Tremadoc stratigraphy and trilobite faunas of northwestern Hunan. 1. Trilobites from the Nantsinkwan For- mation of the Yangtze Platform. Beringeria, vol. 2, p. 3-53. Peng, S., 1990b: Tremadoc stratigraphy and trilobite faunas of northwestern Hunan. 2. Trilobites from the Panjiazui Forma- tion and the Madaoyu Formation in Jiangnan slope belt. Beringeria, vol. 2, p. 55-171. Cavity trilobite /tyophorus undulatus Pratt, B. R., 1982: Stromatolitic framework of carbonate mud- mounds. Journal of Sedimentary Petrology, vol. 52, p. 1203 - 1227. Pratt, B. R., 1995: The origin, biota and evolution of deep-water mud-mound. /n, Monty, C. L. 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Geological Society of America, Boulder, Colorado, and University of Kansas, Lawrence, Kansas. 83 Paleontological Research, vol. 6, no. 1, pp. 85-99, April 30, 2002 © by the Palaeontological Society of Japan Changes in Holocene ostracode faunas and depositional environments in the Kitan Strait, southwestern Japan MORIAKI YASUHARA', TOSHIAKI IRIZUKT, SHUSAKU YOSHIKAWA' AND FUTOSHI NANAYAMA’ ‘Department of Biology and Geoscience, Graduate school of Science, Osaka City University, Osaka, 558-8585, Japan (e-mail: yassan@sci.osaka-cu.ac.jp) "Department of Geosciences, Interdisciplinary Faculty of Science and Engineering, Shimane University, Matsue 690-8504, Japan ‘Active Fault Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba, 305-8567, Japan Received 16 October 2001; Revised manuscript accepted 21 December 2001 Abstract. At least 106 species were identified from 36 samples obtained from two cores (T1 and T2 ), which were recovered from the Kitan Strait off Wakayama City, southwestern Japan. Q-mode cluster analysis of cores T1 and T2 revealed three biofacies (PL, PT and LS). Changes in depositional environments based on the observed distribution of ostracodes were analysed, and the following sequence is proposed. Before ca. 7,000 cal yr BP, the T1 site was a sandy coast, ranging from an outer bay to the open sea, close to a river mouth, at water depths of more than 15-20 m, while the T2 site ranged from a bay coast to an outer bay, close to a river mouth, at water depths of less than 15-20 m. During ca. 7,000-2,000 cal yr BP, the position of the sites fell within ranging an outer bay to the open sea at water depths of 30-40 m influenced by residual and/or tidal currents from the straits. After ca. 2,000 cal yr BP, the sites were situated on a sandy coast, ranging from an outer bay to the open sea, close to a river mouth, at water depths of more than 15-20 m. Two new species, Trachyleberis ishizakii and Cytheropteron kumaii, are also described. Key words: depositional environments, Holocene, Kitan Strait, Ostracoda, Wakayama Introduction Fossil ostracodes have frequently been used to elucidate the way in which the environment of deposition changes with time (e.g., Ishizaki et al., 1993; Cronin er al., 1994; Irizuki et al., 1998b), because they are highly sensitive in- dicators of several environmental factors (e.g., Ishizaki and Irizuki, 1990; Ikeya and Suzuki, 1992; Yamane, 1998; Yasuhara and Irizuki, 2001). However, little studies of Japanese Holocene ostracodes have been carried out (Frydl, 1982; Ishizaki, 1984; Ota et al., 1985; Ikeya et al., 1987; Ikeya et al., 1990; Iwasaki, 1992; Kamiya and Nakagawa, 1993; Irizuki er al., 1998a; Miyahara er al., 1999; Irizuki et al., 2001). Many of these studies concentrate on tem- poral changes of Holocene ostracode assemblages in small drowned valleys and enclosed bays. Irizuki et al. (1998a) elucidated paleoenvironmental changes on the western coast of the Miura Peninsula, central Japan on the basis of numerical analyses of ostracode distributions. Miyahara er al. (1999) and Irizuki er al. (2001) used sedimentary facies from cores, containing fossil ostracodes and high density radiocarbon dating to construct a relative sea-level curve and to discuss paleoceanic changes in the Osaka area, southwestern Japan. The Kitan Strait is situated between Osaka Bay and the open sea. The area provides an important record of the depositional environments of the Seto Inland Sea and Osaka Bay, and therefore yields key data for inferring paleoceanic conditions. This study aimed to elucidate ostracode faunas and the temporal change in depositional environments off the west- ern coast of Wakayama City, near the Kitan Strait. We also discuss the consequences of sea-level changes in Osaka Bay and the study area. Locality, lithofacies and methodology Drilling cores (T1 and T2) were excavated by the Nation- al Institute of Advanced Industrial Science and Technology from the Kitan Strait (T1: 34°14.7° N, 135°5.2° E, 19.61 m 86 Moriaki Yasuhara et al. Osaka Bay Kitan Strait 135° 00° E Figure 1. water depth; T2: 34°14.5° N, 135°5.2° E, 24.78 m water depth) off Wakayama City, southwestern Japan (Figure 1). Nanayama ef al. (1999) described in detail the Holocene and upper Pleistocene sequences in cores T1 and T2. We briefly mention those sequences here (Figure 2). Sediments at altitudes lower than -33.5 m in core T1 and -38.3 m in core T2 consist of sand and gravel, and the en- closing matrix is coarse sand. Sediments at altitudes be- tween -19.6 and -33.5 m in core T1 and between -24.8 and -38.3 m in core T2 consist of alternating beds of fine to medium sand layers and silt layers with shell fragments, showing intensive bioturbation. Nanayama et al. (1999) reported two layers of debris flow deposits (Df1 and Df2). Df1 is situated at altitudes of approximately -24.1 to -24.3 m in core T1 and -29.3 to -30.4 m in core T2 (Figure 2). Df2 is situated at altitudes of approximately -27.2 to -27.7 m in core T1 and -34.5 to -35.7 m in the core T2 (Figure 2). Volcanic glasses are concentrated at an altitude of ap- proximately -31 min core T2. Nanayama er al. (1999) re- ported that these volcanic glasses are correlated with the Kikai-Akahoya (K-Ah) volcanic ash, dated at ca. 7,300 cal yr BP (Fukusawa, 1995). Samples of the sediment core, each approximately 5 cm thick, were immersed in water, boiled for about one hour on a hot plate, washed through a 75 um sieve and then dried. Dry weights were calculated from the original sam- ple weight, scaled by the percentage water content of each sample. The fraction coarser than 200 um was sieved to allow the ostracode fauna to be determined, and for speci- mens of each taxon to be obtained. Samples containing abundant ostracode specimens were divided using a sample splitter into workable aliquots of approximately 100-200 specimens. In the remaining samples, all the specimens present were picked. The number of specimens refers to 132° 134° 136° 138° 140° 142° 144° 146° Index and locality maps. the estimated minimum number of carapaces present in each sample, determined by taking the total number of left or right valves, whichever was the greater. Ostracode biofacies At least 106 ostracode species were identified from 36 samples obtained from cores T1 and T2 (Appendix). A se- lection of these species is illustrated in Figure 3. Q-mode cluster analysis was used to examine vertical changes in ostracode faunas and to determine ostracode biofacies, which would closely reflect variations in the depositional environment. Taxa represented by three or more specimens in any one sample were used for analysis (some Aurila and Pontocythere species groups are ex- pressed collectively as “spp.”), and each sample contained more than 50 specimens. Horn’s overlap indices (Horn, 1966) were used to assess similarities, and clustering was achieved by the unweighted pair-group arithmetic average method. The results revealed three biofacies (PL, PT and LS; Figure 4). To interpret these biofacies reflecting depositional environments, we referred to the distributions of present-day dead ostracode shells, because many studies of the distributions of present-day ostracodes have been based on dead ostracode shells. Figures 5 and 6 show the stratigraphic positions of biofacies and percentages of 24 taxa dominating each of the biofacies in these cores. (1) Biofacies LS (Loxoconcha viva -Spinileberis quadria- culeata biofacies). —Biofacies LS is composed of seven samples and lies in the middle part of cores T1 and T2. It is characterized by the dominance of Loxoconcha viva Ishizaki, Spinileberis quadriaculeata (Brady) and Cythero- pteron kumaii sp. nov. (= Cytheropteron miurense of Ikeya Holocene ostracodes from Kitan Strait 87 altitude (m) 5 — 0 Jen sea level 5 — 410 _ 15 _ -20 _ -25 _ -30 — -35 _ su buried soil | clay A silt » = very fine sand Rs 40 - fine sand 7 medium sand + ZA Coarse sand = BEE Gravel _ ____y volcanic ash (K-Ah) 45 - shell 9780- 14C cal yr BP Figure 2. Columnar sections of T1 and T2 cores and horizons of radiocarbon age (cal yr BP). Radiocarbon ages calibrated and col- umnar sections modified from Nanayama et al. (1999). and Itoh, 1991 and Cytheropteron sp. of Yasuhara and Irizuki, 2001). Ambtonia obai (Ishizaki), Falsobuntonia hayamii (Tabuki), “form A” (Abe and Choe, 1988) of Bi- cornucythere bisanensis (Okubo), Aurila spinifera Schorni- kov and Tsareva s.l., Krithe japonica Ishizaki, Kobaya- shiina donghaiensis Zhao and Amphileberis nipponica (Yajıma) are also common. L. viva is abundant at water depths of 15-37 m in Tateyama Bay, central Japan (Frydl, 1982). S. quadria- culeata is common in most areas of Osaka Bay and Hiuchi- nada Bay (Yasuhara and Irizuki, 2001; Yamane 1998). C. kumaii is reported from the outer part of Sendai Bay near the open sea at water depths of more than 50 m (Ikeya and Itoh, 1991) and from Osaka Bay at water depths of 37.2 m (Yasuhara and Irizuki, 2001). Falsobuntonia (hayamii and taiwanica Malz) is commonly found in the open sea off Shimane at water depths of more than 50 m (Ikeya and Suzuki, 1992). A. obai is abundant at water depths of 20-40 m (e.g., Ishizaki, 1971; Frydl, 1982; Bodergat and Ikeya, 1988). A. spinifera s.l. is reported from the sandy part of Hiuchi-nada Bay near the Kurushima Strait (Yamane, 1998) and from the sandy part of Osaka Bay at a water depth of 37.2 m, where the influence of residual and/or tidal currents from the Akashi Strait is apparent (Yasuhara and Irizuki, 2001). K. japonica, Ko. donghai- ensis and A. nipponica are common at water depths of more than 15-20 m in shallow sea areas around Japan (e.g., Yasuhara and Irizuki, 2001; Yamane, 1998; Bodergat and Ikeya, 1988; Frydl, 1982; Ishizaki, 1971). The distribution of species suggests that biofacies LS is interpreted as ranging from an outer bay to the open sea at a water depth of 30-40 m, under the influence of residual and/or tidal currents from the strait. (2) Biofacies PT (Pontocythere spp.-Trachyleberis scabro- cuneata biofacies).—Biofacies PT is composed of two sam- ples and lies in the lower part of core T2. It is character- ized by the dominance of Pontocythere spp., Trachyleberis scabrocuneata (Brady), S. quadriaculeata and Loxoconcha uranouchiensis Ishizaki, with smaller numbers of Loxo- concha pulchra Ishizaki and Nipponocythere bicarinata (Brady). Intertidal and phytal species (Aurila spp. except A. munechikai and A. spinifera s.l., Australimoosella tomokoae, Cornucoquimba tosaensis, Hemicytherura spp., Loxoconcha spp. except L. optima, L. pulchra, L. tosaensis, L. uranouchiensis and L. viva, Neonesidea oligodentata, Paradoxostomatidae spp., Pseudoaurila japonica, Robu- staurila spp., Sclerochilus sp., Semicytherura spp. and Xestoleberis spp.) are also common. Pontocythere spp. are found in a range of habitats, from the sandy coasts of outer bays to open sea areas and/or river mouths (e.g., Ishizaki, 1968; Ikeya and Hanai, 1982; Yamane, 1998). T. scabrocuneata is abundant in middle to outer bay regions (Yasuhara and Irizuki, 2001). L. Moriaki Yasuhara et al. Holocene ostracodes from Kitan Strait 89 0.7 0.8 overlap index biofacies Figure 4. Dendrogram from Q-mode cluster analysis. PL, PT and LS represent the three biofacies found. uranouchiensis is common in sandy bay coasts and abun- dant at water depths of less than 10 m (Frydl, 1982). L. pulchra is an estuarine inhabitant of Hiuchi-nada Bay, Seto Inland Sea, western Japan, that prefers low salinity and a water depth of less than 4 m (Yamane, 1998). N. bicarinata is common at water depths of more than 15 m in Osaka Bay (Yasuhara and Irizuki, 2001). However, spe- cies common at water depths of more than 15-20 m in shal- low sea areas around Japan (e.g., K. japonica, Ko. donghaiensis, A. nipponica) are either rare or absent in this biofacies. Intertidal and phytal species could have been transported to this area by wave action or coastal currents. Thus, biofacies PT is interpreted as ranging from a bay coast to an outer bay, near a river mouth, with water depths of less than 15-20 m. (3) Biofacies PL (Pontocythere spp. —Loxoconcha op- tima biofacies).—Biofacies PL is composed of 21 samples and lies in the upper part of cores TI and T2, and also in the lower part of the TI core. It is characterized by the dominance of Pontocythere spp., Loxoconcha optima Ishi- zaki, L. pulchra and intertidal and phytal species. K. ja- ponica, Ko. donghaiensis and A. nipponica also occur in this biofacies. L. optima is reported from a sandy coast, ranging from an outer bay to the open sea (Ishizaki, 1968). Those species which are common in biofacies LS, such as C. kumaii, A. obai and F. hayamii, are either rare or com- pletely absent. Biofacies PL is therefore interpreted as a sandy coast, ranging from an outer bay to the open sea, near a river mouth at water depths of more than 15-20 m, but shallower than biofacies LS. Temporal changes of depositional environments Radiocarbon dating was conducted using 31 samples from cores T1 and T2 (Nanayama et al., 1999). We cali- brated these radiocarbon ages using INTCAL98 (Stuiver et al., 1998), because this was not done in the original study. Many of the radiocarbon ages in core T1 were re- versed (Figure 6): we therefore used the radiocarbon ages from core T2 to date temporal changes in depositional envi- ronments. Correlations between cores T1 and T2 are based on Nanayama et al. (1999). Based on the results of Q-mode cluster analysis, vertical changes in depositional environments and associated ostracode faunas in these cores are distinguished as fol- lows: Before ca. 7,000 cal yr BP.—This period is represented by biofacies PT, composed of two samples in core T2 (T2- 14 and 14.1), and the lower part of biofacies PL, composed of three samples in core T1 (T1-14, 17 and 18). It is considered that during this period the T2 drilling site ranged from a bay coast to an outer bay, near a river mouth, with water depth shallower than 15-20 m. At the same time, the TI site was on the sandy coast, ranging from an @ Figure 3. Scanning electron micrographs of fossil ostracodes from drilling cores in the Kitan Strait off Wakayama City. All specimens are adult left valves, except one specimen in Fig. 4.21 (an adult right valve). hayamensis Hanai (sample no. TI-8). 2. Callistocythere alata Hanai (sample no. T1-6). mm (A for 1-19; B for 20-22). 4. Callistocythere undata Hanai (sample no. T2-4). 5. Callistocythere sp. 1 (sample no. T2-8). Scale bars = 1.0 1. Callistocythere 3. Callistocythere asiatica Zhao (sample no. T2-3). 6. Ishizakiella miurensis (Hanai) (sample no. T2-3). 7. Loxoconcha pulchra Ishizaki (sample no. T1-8). 8. Loxoconcha optima Ishizaki (sample no. T1-8). 9. Loxoconcha tosaensis Ishizaki (sample no. T1-6). morpha acupunctata (Brady) (sample no. T1-6). 10. Loxoconcha viva Ishizaki (sample no. T2-8.1). 11. Parakrithella pseudadonta (Hanai) (sample no. T1-6). 13. Spinileberis quadriaculeata (Brady) (sample no. T2-13.1). 12. Cythero- 14. Falsobuntonia hayamii (Tabuki) (sample no. T2-9). 15. Xestoleberis opalescenta Schornikov (sample no. T2-3). 16. Perissocytheridea sp. (sample no. T2-2). 17. Phly- ctocythere japonica Ishizaki (sample no. T2-14). 18. Neopellucistoma inflatum Ikeya and Hanai (sample no. T2-2). 19. Ambtonia obai (Ishizaki) (sample no. T2-12). 20. Aurila spinifera s.1. Schornikov and Tsareva (sample no. T2-13). 21. Cletocythereis sp. (sample no. T2-6). 22. Trachy- leberis scabrocuneata (Brady) (sample no. T1-7). 90 Moriaki Yasuhara et al. altitude (m) -20 —T2-1— sample horizon (more than 50 specimens) 0 20 40 60 80 100(%) -72402-sample horizon p: presence (less than 50 specimens) 4 = EN form A Cytheropteron Kkurnaïï = Be) ea | 1 ES = == = E & a SANENSIS à N N) S > JA 02 Ambtonia ob Aurila munechikat Aurila spiniferas]. Callistocythere alata Cythere omotenipponica there b Cytheromorpha acupunctata cornucy cornucythere B, Bü Bi Figure 5. th, Las Loxoconcha optima Loxoconcha pulchra Loxoconcha tosaensis Loxoconcha uranouchiensis weit eae eae MATTER |) ulin THE I [1 77 he ee _ ıyei culeata rte Spinileberis quad) hinou biofacies Schizocythere Kis. brocuneata Loxoconcha viva Pontocythere spp. IS SCH 77: deep water species brackish-water species Pistocythereis bradyi intertidal and phytal species Parakrithella pseudadonta Trachylebe. Columnar section of core T2, sample horizons, radiocarbon ages (cal yr B.P.), biofacies and percentages of dominant ostracode spe- cies. Deep-water species are Amphileberis nipponica, Falsobuntonia hayamii, Kobayashiina donghaiensis, Krithe japonica and Nipponocythere bicarinata. Spinileberis furuyaensis and Spinileberis pulchra. Brackish water species are Cytherura miii, Darwinula sp., Ishizakiella miurensis, Perissocytheridea japonica, Perissocytheridea sp., Intertidal and phytal species are Aurila spp. except A. munechikai and A. spinifera s.l., Australimoosella tomokoae, Cornucoquimba tosaensis, Hemicytherura spp., Loxoconcha spp. except L. optima, L. pulchra, L. tosaensis, L. uranouchiensis and L. viva, Neonesidea oligodentata, Paradoxostomatidae spp., Pseudoaurila japonica, Robustaurila spp., Sclerochilus sp., Semicytherura spp. and Xestoleberis spp. outer bay to the open sea, near a river mouth, with water depths of more than 15-20 m. Species that are common at water depths of more than 15-20 m in shallow sea areas around Japan (e.g., A. obai, K. japonica, Ko. donghaiensis and A. nipponica) are, however, absent in samples T1-17 and T1-18. In these horizons, it is considered that water depths were shallower than the other horizons. Ca. 7,000-2,000 cal yr BP.—This period is represented by biofacies LS, and is composed of six samples in core T2 (T2-9, 10, 11, 12, 13 and 13.1), and one sample in core T1 (T1-13). These sites ranged from an outer bay to the open sea at water depths of 30-40 m, and were influenced by residual and/or tidal currents from the strait. After ca. 2,000 cal yr BP.—This period is represented by biofacies PL and is composed of nine samples in core T2 (T2-1, 2, 3, 4, 5, 6, 7, 8 and 8.1), and also the upper part of biofacies PL, which is composed of nine samples in core T1 (T1-1, 2, 3, 4, 5, 6, 7, 8 and 10). These sites were at the sandy coast, ranging from an outer bay to the open sea, near a river mouth, with water depths greater than 15-20 m, but shallower than biofacies LS. The percentage of those species that are common at water depths of more than 15-20 m in shallow sea areas around Japan (e.g., A. obai, K. japonica, Ko. donghaiensis and A. nipponica) are smaller in core T1 than in core T2. This indicates that the T1 site was in shallower water than the T2 site during this period. Holocene ostracodes from Kitan Strait altitude (m) —T1-2— sample horizon (more than 50 specimens) 0 20 40 60 80 100(%) ---TX9 -- sample horizon 91 p: presence (less than 50 specimens) | en = el aa er Sel A SES In..n..| Sasse © Ambtonia obai Aurtla munechikai Aurila Spinifera s]. Callistocythere alata : Cythere omotenipponica : Cytheromorpha acupunctata‘ Cyrheropteron kumali Loxoconcha optima Bicornucythere bisanensis form A Figure 6. cies. In the Osaka Plain and the inner part of Osaka Bay, the relative sea-level change has been studied in detail on the basis of sedimentary facies, fossil ostracode faunas and high-density radiocarbon dating of molluscan shells (Miyahara et al., 1999; Masuda er al., 2000; Masuda and Miyahara, 2000; Irizuki et al., 2001). These studies re- ported that the sea level rose rapidly from the period between ca. 11,000 cal yr BP to ca. 5,300-5,000 cal yr BP and from that time fell to the present sea level. The maxi- mum sea level highstand was at ca. 5,300-5,000 cal yr BP in Osaka Bay (Masuda er al., 2000). The historical changes in water depth at the two sites investigated in this study are similar to the relative sea-level changes proposed by Masuda et al. (2000), although the cores reveal areal dif- ferences in faunal changes during the same period. This result suggests that the relative sea-level curve of Masuda Loxoconcha pulchra biofacies Loxoconcha viva Pontocythere spp. deep water species brackish-water species Pistocythereis bradyi intertidal and phytal species Loxoconcha tosaensis Spinileberis quadriaculeata Schizocythere kishinouyei : Trachyleberis scabrocuneata Parakrithelle pseudadonta Columnar section of core T1, sample horizons, radiocarbon ages (cal yr B.P.), biofacies and percentages of dominant ostracode spe- Deep-water, brackish, and intertidal and phytal species are similar to those in Figure 5. et al. (2000) lends itself to the standard for relative sea- level change not only in Osaka Bay but also in more wide areas. Systematic descriptions All the illustrated specimens are deposited in the collec- tions of the Department of Biology and Geosciences, Graduate School of Science, Osaka City University (OCUCO). Suborder Podocopina Sars, 1866 Superfamily Darwinuloidea Brady and Norman, 1889 Family Darwinulidae Brady and Norman, 1889 Genus Darwinula Brady and Robertson in Jones, 1885 Yasuhara et al. Holocene ostracodes from Kitan Strait 93 Darwinula sp. Figure 8.5-8.8 Materials. —20 specimens. Diagnosis.— Darwinula characterized by elongate and small carapace. Occurrence.—T 1-2, 4-6, 8, T2-2 to T2-4, 6, 8, 10. Remarks.—This species has central muscle scars charac- teristic of darwinulids. This is the first fossil record of the genus from the Japanese Holocene. Ikeya and Hanai (1982) attributed a single broken valve from the Recent of Hamana-ko Bay, central Japan, to this genus. This genus has a freshwater habitat (Van Morkhoven, 1963). Superfamily Cytheroidea Baird, 1850 Family Trachyleberididae Sylvester-Bradley, 1948 Subfamily Trachyleberidinae Sylvester-Bradley, 1948 Tribe Trachyleberidini Sylvester-Bradley, 1948 Genus Trachyleberis Brady, 1898 Trachyleberis ishizakii sp. nov. Figure 7.1-7.10 Cythereis Yamigera [sic] (Brady). 64-66. Trachyleberis scabrocuneata (Brady). Ishizaki, 1969, p. 221- 222, pl. 26, fig. 8; Ishizaki, 1971, p. 92-93, pl. 4, fig. 16; Okubo, 1979, p. 156, fig. 7a, b; Ikeya and Compton, 1983, p.120, pl. 10-120, figs. la-4b, p. 126, pl. 10-126, figs. 1a- 4b; Paik and Lee, 1988, p. 550, pl. 2, fig. 11; Ikeya and Itoh, 1991, p. 145, fig. 24, C; Kamiya and Nakagawa, 1993, p. 129, pl. 4, fig. 7; Ishizaki er al., 1993, p. 329, fig. 7c; Irizuki et al., 1998a, p. 7, fig. 2.13; Kamiya er al., 2001, p. 103, fig. Kajiyama, 1913, p. 12, pl. 1, 18.18. Cythere scabrocuneata Brady. Puri and Hulings, 1976, p. 289, pl. 26, figs. 6, 8. Trachyleberis sp. 1. Ikeya and Suzuki, 1992, p. 137, pl. 9, fig. 4. Actinocythereis sp. Kamiya and Nakagawa, 1993, p. 129, pl. 4, fig. 8. Trachyleberis sp. Irizuki et al., 2001, p. 109, fig. 3.8; Yasuhara and Irizuki, 2001, p. 95, pl. 12, figs. 9-13. Etymology.—In honor of Dr. Kunihiro Ishizaki. Materials. —86 specimens. Diagnosis.—Trachyleberis characterized by subtriangu- lar valve shape, tubercles on valve surface, large dorsal tu- bercles and anterior marginal ridge. Description. — Carapace large, subtriangular, tapering posteriorly in lateral view, highest at anterior cardinal angle. Anterior margin broadly rounded and slightly ex- tended below. Dorsal margin straight. Ventral margin broadly convex in female and straight in male. Posterior margin acuminate. Anterior, ventral and posterior margins fringed by spines and tubercles. Surface ornamented with tubercles, subcentral tubercle and anterior marginal ridge. Anterior marginal ridge running from anterior cardinal angle to midpoint of anterior margin. Eye and subcentral tubercles distinct. Pore canal openings moderate in num- ber, scattered on most of valve surface. Pore canals with opening along edge of marginal contact zone of ventral marginal surface straight, numerous along anterior and posteroventral margins. Marginal infold moderate in width along anterior and posterior margins. No vestibule. Hinge holamphidont. Muscle scars consisting of one V- shaped frontal scar and a row of four adductor scars. Sexual dimorphism distinct; males more slender than fe- males. Types.— Holotype, sample no. T1-6, OCUCO 0005, male RV, L = 0.884 mm, H = 0.420 mm (Figure 7.1); 9 paratypes, sample nos. T2-8.1, OCUCO 0006, T2-7, OCUCO 0007, T2-8, OCUCO 0008, T2-7, OCUCO 0009, io AAIEI WIN, 2 Sor OCW COROOHI 12-8; OCUCO 0012, T1-6, OCUCO 0013 and T1-6, OCUCO 0014. Type locality.—Holocene sediments off Wakayama City CA lAaaNSE3s5> S2eE): Occurrence.—T1-2, 5-10, 13, 14, 18, T2-4 to T2-8, 8.1, DA lites). Remarks. — This species is similar to Trachyleberis scabrocuneata (Brady, 1880), but differs in having a shorter anterior marginal ridge, smaller carapace, straight margin broadly convex in male, larger dorsal tubercles, smaller number of surface tubercles and more slender shape. Also, this species is similar to Trachyleberis niitsumai Ishizaki, 1971, but differs in having a shorter an- terior marginal ridge, more prominent and regular surface tubercles, larger dorsal tubercles and more slender shape. © Figure 7. Trachyleberis ishizakii sp. nov. 1. Lateral view of male RV, holotype, T1-6, OCUCO 0005, L = 0.884 mm, H = 0.420 mm. 2. Internal view of male RV, T2-8.1, OCUCO 0006, L = 0.883 mm, H = 0.419 mm. 3. Lateral view of male LV, T2-7, OCUCO 0007, L = 0.869 mm, H = 0.447 mm. 4a, b. Internal view and muscle scars of male LV, T2-8, OCUCO 0008, L = 0.921 mm, H = 0.439 mm. 5. Lateral view of female RV, T2-7, OCUCO 0009, L = 0.848 mm, H = 0.463 mm. 6a, b. Internal view and muscle scars of female RV, T2-8.1, OCUCO 0010, L = 0.848 mm, H = 0.445 mm. 7. Lateral view of female LV, T2-8.1, OCUCO 0011, L = 0.848 mm, H = 0.476 mm. 8. Internal view of female LV, T2-8, OCUCO 0012, L = 0.852 mm, H = 0.480 mm. 9. Lateral view of A-1 stage RV, T1-6, OCUCO 0013, L = 0.656 mm, H = 0.359 mm. 10. Lateral view of A-1 stage LV, T1-6, OCUCO 0014, L = 0.641 mm, H = 0.362 mm. 6b and 4b. Scale bars are 0.1 mm: A for 1-4a, 5-6a and 7-10; B for Moriaki Yasuhara et al. Holocene ostracodes from Kitan Strait 95 Family Cytheruridae G.W. Müller, 1894 Subfamily Cytheropterinae Hanai, 1957 Genus Cytheropteron Sars, 1866 Cytheropteron kumaii sp. nov. Figure 8.1-8.4 Cytheropteron miurense Hanai. Ikeya and Itoh, 1991, p. 136, fig. 15, A. Cytheropteron sp. Yasuhara and Irizuki, 2001, p. 79, pl. 4, fig. 10. Etymology.—In honor of Prof. Hisao Kumai. Materials.—80 specimens. Diagnosis.— Cytheropteron characterized by subrhom- boidal valve shape, small carapace and straight ventral alar process. Description.—Carapace small, subrhomboidal in lateral view, highest at midlength. Anterior margin obliquely rounded. Dorsal margin strongly arched. Ventral margin sinuate, concave in middle, obscured in posterior third by alar process. Posterior margin protruding into a horizon- tally pointed caudal process. Surface ornamented with nu- merous reticula aligned more or less vertically, and dorsal and ventral marginal ridges. Reticula coarser in posterior half. Dorsal marginal ridge arcuate, very narrow, running along dorsal margin from anterior third to posterior termi- nal. Ventral marginal ridge starting from anterior end and running along ventral margin to form a prominent anterior edge of alar process. Eye tubercle indistinct. Pore canal openings moderate in number, scattered on most of valve surface. Pore canals with openings along edge of marginal contact zone of ventral marginal surface few, approxi- mately ten along anterior margin. Marginal infold moder- ate in width along anterior and posterior margins. Vestibule poorly developed along anterior margin, broadest at anteroventral margin. Hinge line sinuous in interior view. Hinge of right valve consists of anterior and poste- rior teeth and an intermediate groove. Intermediate groove subdivided into three parts: short anterior part with three large crenulations, finely crenulate median part and con- cave posterior part with six small sockets, of which the an- terior three are clearly separated and the posterior three are connected to each other. Hinge of left valve complemen- tary of that of right valve. Muscle scars consist of two frontal scars, of which upper scar is smaller and lower scar is elongate, and a row of four elongate adductor scars. Sexual dimorphism indistinct. Type and Dimensions.—Holotype, sample no. T2-12, OCUCO 0015, adult LV, L = 0.482 mm, H = 0.313 mm (Figure 8.3); 3 paratypes, sample nos. T1—12, OCUCO 0016, T1-12, OCUCO 0017 and T2-12, OCUCO 0018. Type locality.—Holocene sediments off Wakayama City (342 14°57 N, 135° 5:27 BE). Occurrence.—T 1-2, 5, 10, 12-14, T2-4 to T2-7, 8.1, 9, 10, 11-13, 13.1. Remarks. — This species is similar to Cytheropteron miurense, but differs in having a thinner alar process and finer and larger amount of surface ornamentation. Conclusions 1. Before ca. 7,000 cal yr BP, site T2 ranged from a bay coast to an outer bay, near a river mouth, at water depths of less than 15-20 m, and site T1 was a sandy coast, ranging from an outer bay to the open sea, near a river mouth, at water depths of more than 15-20 m, but shallower than biofacies LS. 2. From ca. 7,000-2,000 cal yr BP, the two sites varied in condition from an outer bay to the open sea at water depths of 30--40 m, where they were strongly influenced by the residual and/or tidal currents from the strait. 3. After ca. 2,000 cal yr BP, the two sites were situated along a sandy coast, ranging from an outer bay to the open sea, near a river mouth, at water depths of more than 15-20 m, but shallower than biofacies LS. Site T1 was shallower than site T2 during this period. Acknowledgements We would like to thank Kunihiro Ishizaki of Ishinomaki Senshu University for critical reading of the manuscript, and Hisao Kumai of Osaka City University for advice and continuous encouragement throughout the course of the present study. We also thank Hisao Ishii and Yoko Ishii of the Osaka Museum of Natural History for permission and assistance to access the drilling core samples, and Takamoto Okudaira of Osaka City University for providing permission to use and instruction in the operation of the scanning electron microscope (JEOL JSM-5500) in his laboratory. Anonymous reviewers improved the paper considerably. @ Figure 8. 1-4, Cytheropteron kumaii sp. nov. 1. Lateral view of adult RV, TI-12, OCUCO 0016, L = 0.482 mm, H = 0.326 mm. 2a-c. Internal view, muscle scar and hinge of adult RV, TI-12, OCUCO 0017, L = 0.530 mm, H = 0.349 mm. 3. Lateral view of adult LV, holotype, T2-12, OCUCO 0015, L = 0.482 mm, H = 0.313 mm. 4a-c. 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DN 27s SEEBEERE BEREITETE re | EVE EEBERSEEEEEEELLIESSESSSe0 USL USe on a fe a i fe le eu. nn aaa al ore ez | aS a i i i RRRRRERE Essa eee PEEP EEE 72 US RENTRER Mike Te Ess pep mae CEE CEE ERE SCE ea erect ENS i U etree entree ERNEST TEE SN Peso eee ssneeselL_ LL een pore aN | S| i U DE seo eee SE nnn eo TE aa ba RE a I I I RT LL BEREITS EESENEEREREEESEeeeeaseeeelee le BEER ARR SSDOURNn LE RES UÈtEBETEL Cr EE RER RENAN ER ANNEE U EE DR ETES TER NRAR Ne ReROne EEE TT EE NUE SIREN enr RAsER CCE OCT EE TO ER ESSSEG ERA EINES SEE ee Do EE | GRR ane a TERRE TET DE ET RER II ER I I U I ET DU DI a Eee SSeS SEES LeSeeee EE EE TE NE RGO RRRE COR D nr rue is | Re sen EN: 272772272 NN REREE TUNER ESRLONnnTr CT CR TT NES RENE RER Be ROLE CCC ET = ees RER = | ER RRRnNnRANSUnnnnTTUTT D EEE SORTE DIER IR na nn en Een PC ER NN NN Res Rue RE I I I I I CEE ET NN SES eee ee EEE eee see eee see ET 8 OS ERA OnUONT (ee eras RESORT EN I ii ET RE (Rees A SEE ENS ENSEREDULEERreC er RC Va | aS eee a ee a HE IE ERREUR I a I N U eee TE I | ID a I BE BEWIESEN EN I U DRE DOS ns EE ECS TEE SsSERRERELT [Neo SEE > I III IR | Te ET I CCC BEER EEE DEN eee eee SLL EEE ZONEN STERNEN TEEN jus See FO ED I a a I EEE ZEIG SEENBEEBIHEIEE ERAHNEN) = SG tes eee eter a me SS i i i | ae EEE BER SSEEEOSesSchSeeeshess ACTU Se PE —— a eee Se a I I I I EI nr CNT SSSR RENE a a I U U RE CEE nen ee nn mE rere SE a a SE i HH HE HH ee NN soloads awe olaulmilæ|nlw|n|æo|o = o m|m + oo 0er RER lea ERREGER Joquinu ajdures|=| 55e El El El El El ElElElElE Eu] a] ou af] CU] fo] ue eu a} ua ua eu Appendix. 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A MR ee EN 1 | 1 9 [PI PNR NT 1 11 moo a et BEIZZZZZEZTETTZZZENEEEEENEENEREREREEENENEENEGEERERENE DOTE TT TT A Ee Be eae I re i EEE D DL CINE oe eS eee ee ee Se EE Ree ARR nn 7 EEHEEEBNEERENENEERENEEGENRENREGENNENN EE LL LL ELLE “es mom [| TT asuorsımu urn | Si I TIM MINI] See 1 ea eRe 222222708 ES ee Bee ees 272222380 SR eee Dain Te EEEEREREENE sisuaryonounin pysuoooxon™|™| 17] IS] I | IT I I I IT | I IS RATES S2199dS a Sd fa Mad Bad Pod df Wiad Se" [=] om + ou t|wlolnjaoloal—|—-l—|—|-l-|/-|-— = ala] a A ZT = | I] I > le ee ed ed u ae CY] ed] ST EU ES ES EU ow EN a soquinu ajduses| = | F-IFIFIFIFIF FIEIEIEIEIEIEIEIEIE F 99 Paleontological Research, vol. 6, no. 1, pp. 101-120, April 30, 2002 © by the Palaeontological Society of Japan Taphonomy of the bivalve assemblages in the upper part of the Paleogene Ashiya Group, southwestern Japan NORIHIKO SAKAKURA Department of Geology and Mineralogy, Kyoto University, Kyoto 606-8502, Japan (E-mail: sakakura @ kueps.kyoto-u.ac.jp) Present address: Research Institute for Integrated Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, 259-1205, Japan Received 18 August 2000; Revised manuscript accepted 30 November 2001 Abstract. The Paleogene Ashiya Group, in which molluscan fossils are abundant (= Ashiya fauna), consists mainly of shallow marine deposits that exhibit sedimentary cycles especially in the Waita Formation (upper part of the Group). Each cycle is redefined as a thin transgressive basal sandstone (transgressive systems tract) overlain by a progradational coarsening-upward interval (highstand systems tract). The depositional environment varies from a shallower condition influenced by strong wave action (shoreface?) to a deeper con- dition below the storm wave base, which is followed by next shallower conditions such as lower shoreface or intertidal zone. Molluscan fossils occur only from the thin lower part of each cycle, namely the transgressive basal sandstone and from the mudstone of the earliest progradational phase. The fossils occur both as shell concentrations and more dispersed fossiliferous deposits. Bed-by-bed sampling based on taphonomic, sedi- mentologic and paleoecologic observations distinguishes four fossil assemblages, (a) Glycymeris-Phacosoma, (b) Venericardia-Crassatella, (c) Venericardia and (d) Yoldia-Nucula. These assemblages occur successively in each cycle, and their taphonomic features also change upward from a wave-generated allochthonous shellbed on the basal ravinement surface to autochthonous shell patches. The successive change accompanies a de- creasing wave-influence during a transgressive period. Epibionts, such as epifaunal byssally attached bi- valves and barnacles, occur abundantly as associated species of the Venericardia-Crassatella assemblage from the middle part of the transgressive basal sandstone. Epibiontic colonization probably reflects taphonomic feedback, with shelly substrates avoiding burial by the winnowing of sediments during transgression. Autochthonous shellbeds dominated by Venericardia subnipponica are intercalated in the glauconitic sand- stone beds (surface of maximum transgression) at the top of the transgressive basal sandstone. The shellbeds probably represent an attritional accumulation with dead shells of Venericardia supplied continuously in situ during a phase of low sediment supply. Key words: Ashiya Group, bivalves, paleoecology, Paleogene, sedimentary cycle, transgression Introduction The Ashiya Group is the uppermost sequence of coal- bearing Paleogene deposits in the northern limb of Kyushu. It consists of shallow marine sandstones and mudstones, and is biostratigraphically assigned to the latest Early Oligocene age by calcareous nannoplankton and foraminifera (Saito and Okada, 1984; Tsuchi er al., 1987). It was lithostratigraphically subdivided into the Yamaga, Sakamizu, and Waita Formations in upward sequence (Nagao, 1927a, 1928a; Okabe and Ohara, 1972 etc.). Re- cently the stratigraphic division was revised by Ozaki et al. (1993), in which the Yamaga, Norimatsu, Jinnobaru, Honjo and Waita Formations were redefined. Hayasaka (1991) investigated the group sedimentologically, distinguished 23 coarsening-upward sedimentary cycles, and gave their en- vironmental interpretations. Abundant molluscan fossils from the Group are called the Ashiya Fauna and represent the typical molluscan fauna of Oligocene age in west Japan (Nagao, 1927a, 1928a; Otsuka, 1939; Oyama et al., 1960 etc.). The molluscan fossils have been taxonomically and biostratigraphically studied by several authors (Nagao, 1927b, 1928b; Mizuno, 1963 etc.). In addition, the molluscan fauna from the Jinnobaru Formation was studied paleoecologically (Shuto and Shiraishi, 1971). However, little is known about the precise relation be- tween sedimentary cycles and the molluscan assemblages, which exhibit characteristic modes of occurrence by facies. Taphonomic features of the molluscan assemblages also re- 102 Norihiko Sakakura Route map area in Figure 2 OS SN NES NES Jus Quaternary Jinnobaru F. Basements NS Fault Fe] Alluvium NN Honjo F. G Otsuji G. x Syncline F | Pleistocene depo. ita F. Kanmon G. Figure 1. Geologic map of the Wakamatsu area, Kitakyushu, northern Kyushu. Route-mapped area in Figure 2 indicated by thick arrows and Locality 3100 are shown. main largely to be investigated. To clarify these problems, I closely examined the sedi- mentary features and modes of fossil occurrence of the Ashiya Group bed-by-bed. Through detailed observations, particularly in the Waita Formation (the upper part of the Group), I discovered a close relationship between the sedi- mentary cycle and the composition and mode of occurrence of bivalve assemblages. These changes are commonly re- peated in every cycle of the Waita Formation. This paper aims to reconstruct the sedimentological and paleoecological processes in the Ashiya Group based on detailed observations of its sedimentological and taphono- mic features. My aims here are to: (1) redefine the sedi- mentary cycles in the Waita Formation and describe its lithofacies, (2) describe modes of occurrence and the suc- cession of the molluscan assemblages in the cycle, and (3) discuss the formative process of the sedimentary and paleoecological succession. Geological setting The Ashiya Group in the study area is bounded on the east by a fault of NNW-SSE trend, and on the west by the Onga River. The strata of the group strike N 20-45° W and dip 10-30° gently northeastward except for those in the eastern limb of the syncline (Figure 1). In the eastern limb, the strata steeply strike N 10-50° W and dip 45° W. At least seven faults of similar NW-SE trend are observed Paleogene bivalve taphonomy ===] Cross-stratified sandstone == at cycle top (Facies 5 or 6) Alternation of HCS sandstone = & mudstone (Facies 4) Bioturbated basal sandstone (Facies 1) eS à i = Slumping unit === Mudstone with thin ER == sandstone bed (Facies 3) *., Fault = Mudstone (Facies 2) 4 Cycle basement Figure 2. Route map from the Iwaya to Waita coast (Figure 1). redefined sedimentary cycles are shown. or estimated. The Ashiya Group is subdivided into the Yamaga, Norimatsu, Jinnobaru, Honjo and Waita Formations in as- cending order (Ozaki et al., 1993). The lowermost Yamaga Formation is characterized by bioturbated fine sandstones. The formation is more than 170 m thick, al- though the basal part is unexposed. The succeeding Norimatsu Formation consists of the alternating sandstone and mudstone, and is 50-70 m thick. Both formations crop out in the western part of the study area (Figure 1). The Jinnobaru Formation consists of sandstones in which hummocky cross-stratification is occasionally observed, and is 140-260 m thick. The Honjo Formation consists of sandstones and mudstones, exhibits sedimentary cycles, and is about 230 m thick. Both formations crop out in the central part of the area from north to south (Figure 1). The Waita Formation (uppermost of the Group) exhibits clear sedimentary cycles composed of sandstones and mudstones (Figure 2). It is widely distributed in the east- The left section connected to the right at the asterisks (*), Localities and ern part of the area, and is more than 450 m thick, although the top part is unexposed (Figure 1). Sedimentary cycles The upper part of the Ashiya Group (Honjo and Waita Formations) consists of coarsening-upward sedimentary cy- cles (Hayasaka, 1991; Ozaki et al., 1993). Each cycle is 30-100 m thick (Figure 3), and consists of various sand- stones and mudstones. At least 11 sedimentary cycles, named W1-W11 in ascending order, are recognized in the Waita Formation (Hayasaka, 1991; Ozaki er al., 1993). Previous studies defined the sedimentary cycles as coarsen- ing-upward lithologic change, which begins with a mud- stone interval and ends with a sandstone interval (Haya- saka, 1991, p. 617, fig. 5; Figure 3). However, close examination indicates that the definition of the cycles must be revised. Specifically, there is a sharp erosional surface within the upper sandstone interval of 104 Norihiko Sakakura Lithology | RS |SEitlow are ae = Waita Formation | T Progradation =. ee W1b mie Honjo Formation Facies 15,61 4 3 = each previous “cycle” (Figure 4A). This surface marks a distinct depositional boundary between the stratified sand- stone and the mottled sandstone (Figure 3), whereas the transition from the burrowed sandstone to the overlying mudstone is continuous and gradational, as well as from the mudstone to the stratified sandstone. Therefore, it is much better to define the erosional surface as the base of each cycle. I use the names of W1-W11 to denote cycles de- fined in this way. Following this revision, each cycle consists of a trans- gressive basal sandstone (Facies 1), which fines usually from medium sandstone upward to very fine sandstone, and the overlying progradational coarsening-upward interval (Facies 2-6; Figures 4B and 5). The latter is lithologically subdivided into five sedimentary facies: mudstone (Facies 2), mudstone interbedded with very thin sandstone beds (Facies 3), alternated HCS (hummocky cross-stratification) sandstone and mudstone (Facies 4), amalgamated HCS sandstone (Facies 5), and tabular cross-stratified sandstone (Facies 6; Figure 5). As examples, successions of the cy- cle W3 and W10 are shown in Figure 5. Transgressive basal sandstone (Facies 1) The transgressive basal sandstone (Facies 1) rests on a distinctive erosional surface truncating the upper part of the underlying cycle (Figures 3, 5), and fine upward from me- dium sandstone to very fine sandstone (Figure 5). This basal sandstone facies is conformably capped with mud- stone of the Facies (2) or (3) (Figures 3, 5). The thickness of the basal sandstone attains 5-20 m, and is thin compared with the overlying coarsening-upward interval in each sedi- mentary cycle (30-100 m). The basal sandstone is gray to greenish gray in color and includes lithic granules, grains of green smectite, and pum- Figure 3. Columnar section of the Waita Formation exposed along the Iwaya to Waita coast. At least 11 sedimentary cycles, W1- Wil in ascending order, are recognized in the Waita Formation. Facies 1-6 indicate sedimentary facies in a cycle: transgressive basal sandstone (Facies 1), mudstone (Facies 2), mudstone interbedded with very thin sandstone beds (Facies 3), alternation of HCS sandstone and mudstone (Facies 4), amalgamated HCS sandstone (Facies 5), and tabular cross-stratified sandstone (Facies 6) in order. Glauconite sandstone bed is intercalated at the top of the transgressive basal sand- stone of the Cycle 3. Facies 2-4 compose the progradational coars- ening-upward interval. = Figure 4. Lithofacies of the cycles in the Waita Formation. a wave dune covers the erosional surface. The cliff is 15 m in height. D. Vertical profile of the basal sandstone. Photomicrograph of top part of basal sandstone (Facies 1), Loc. 601 la. A. Erosional basement of the sedimentary Cycle W3, Loc.6005 A shellbed showing Hammer is 30 cm long. B. Up-coarsening interval (Facies 2-5) in Sedimentary Cycle W5, Loc. 6047. C. Vertical profile of the basal sandstone (Facies 1) bioturbated by Thalassinoides ichnosp, Loc. 6006. (Natural size.) Light-colored grains are pumice, dark-colored grains green smectite. Loc. 6098a. (Natural size) E. Glauconite grains, gray in the photograph, are abundant. Scale is 0.5 mm long. F. Phycosiphon ichnosp. in vertical profile of the mudstone with thin sheet sandstone (Facies 3), Loc. 6017. (Natural size.) G. Planolites ichnosp. in vertical profile of alternation of HCS sandstone and mudstone (Facies 4), Loc. 6102. (Natural size) H. Amalgamated HCS sandstone (Facies 5), Loc. 6026. Hammer is 30 cm long. Paleogene bivalve taphonomy 106 Norihiko Sakakura Loos ng eneeeneeneneneneneeeeeeeseeen gestes anne Alternation of HCS sandstone & | mudstone (Facies 4) |? © HCS, wave ripple, 2 bioturbation (mudstone) s © Phycosiphon, Planolites rg Locs RN, = 4 iZ ‘~)' Tabular cross- & B stratified sandstone 3 ‘Mudstone with thin | £: (Facies 6) = : sandstone bed un © tabular & trough & ' (Facies 3) Sle cross-stratification, "g © current & wave ripples, 2 = S herringbone cross- | 6017 frequent bioturbation Outre 2 stratification, = © Phycosiphon Bale low bioturbation en . i B 8 Es / Alternation of HCS | #|© Mudstones (Facies 2) ra Pp sandstone & "à 5 [8 mudstone (Facies 4) Oly oe © R A Mudstone with thin |5 | § © bioturbation, [lo sandstone bed Sie ae) | 6014 (Unit 3) sl € Phycosiphon, Rosselia, S ’ 5 = Teichichunus g PE Mudstone (Facies 2) | 9 | # ds © | à © bioturbation A re Slo © Bari ‘ thin sandstone bed | & (Facies 3) aes A Saccella-Nucula uw l'O 6012 © current & wave ripples, bo | © Sans ve basal intense bioturbation © un \ Eressive pasa © Phycosiphon Ay MES glauconite (top part) v.f. sandstone), sa 05 © Thalassinoides, 6099 intense bioturbation CLEA Ophiomorpha 6098 © Thalassinoides 6005 le ES À bivalves (Figs. 8, 9) 6097 A bivalves, barnacles (Figs. 8, 9) Figure 5. sandstone (Facies 1) Oup-fining (f. sandstone - v.f. sandstone), intense bioturbation, Facies 3 in underlying cycle W2 ........ Sedimentary cycles and the lithological facies in the Waita Formation. Transgressive basal sandstone (Facies 1) © up-fining (m. sanstone - Each cycle is subdivided into the basal sandstone (Facies 1) and the up-coarsening interval (Facies 2-5 or 6). = Figure 6. Modes of fossil occurrence. A. Bidirectional imbrications (arrows) of shell fragments of the Glycymeris-Phacosoma Assemblage (a) in the basal sandstone (Facies 1) of cycle W3, at Loc. 6005. This sedimentary structure is characteristic of a wave dune.Sscale bar is 2 cm long. B. Epifaunal bivalves, Chlamys sp. and barnacles of Venericardia-Crassatella Assemblage (b2) in the basal sandstone (Facies 1) of cycle W11, at Loc. 6109. Barnacles attach to shell surface. Lens cap is 5.5 cm in diameter. C. Matrix of the host sediment of the Venericardia-Crassatella Assemblage with abundant epifauna (b2; same as in figure 6B). The shell fragments are concentrated and imbricated in the vertical profile. (X 0.9). D. Articulated shells showing geopetal of the Venericardia-Crassatella Assemblage (b2; same as in figure 6B). Scale bar is 2 cm long. E. Shell replaced by clay minerals of the Venericardia-Crassatella Assemblage (b2) in the basal sandstone (Facies 1) of cycle W10, at Loc. 6098a. Scale bar is Imm long. F. Horizontal view of shell clumps (Venericardia subnipponica) of the Venericardia Assemblage in the middle part of the basal sandstone of cycle W3, at Loc. 4407. Articulated shells are observed. Lens cap is 5.5 cm in diameter. G. Profile of the matrix deposits of the Yoldia-Nucula Assemblage (d) in the mudstone of the cycle W2, at Loc. 6001a. (Natural size.) H. Apices-oriented shells on minor erosional surface of the Yoldia-Nucula Assemblage (d; same as in figure 6G). Lens cap is 5.5 cm in diameter. Loc. 6001a. 107 y phonom Paleogene bivalve ta 108 Norihiko Sakakura Paleogene bivalve taphonomy 109 ice (Locs. 6006, 6082, 6098a; Figure 4D). In cycle W3, many glauconite grains occur, especially from the top part of the transgressive basal sandstone just below the mudstone of Facies (2) (Figures 4E, 5). The basal sand- stone is mottled and intensely bioturbated: Thalassinoides and Ophiomorpha burrows are abundant (Figure 4C). The basal erosional surface is burrowed occasionally by these ichnospecies (Loc. 6005). In addition to the basal surface, several minor erosional surfaces are recognized, usually within the lower part of the sandstone. These erosional surfaces undulate with relief of up to 30 cm, and are usually overlain by allochthonous shellbeds or pumice layers (Figures 4A, 5). The basal shellbed locally forms small shell mounds on the wavy erosional surface. These shells show bidirectional imbri- cations (Loc.6005; Figure 6A). Such sedimentary struc- ture characterizes a wave dune (Cheel and Leckie, 1992). Articulated bivalve shells are dispersed as patches in the upper part of the basal sandstone (Figures 5, 6F), in con- trast to the allochthonous shellbeds in the lower part of the facies. Molluscan fossils are abundant (Figure 7). Assemblages of (a) Glycymeris-Phacosoma, (b) Venericardia-Crassa- tella, and (c) Venericardia occur from this facies (Figure 8; described later). Progradational coarsening-upward interval (Facies 2-6) Two types of progradational coarsening-upward intervals are recognized in the Honjo and Waita Formations. The first type is composed of mudstone (Facies 2), mudstone interbedded with very thin sandstone beds (Facies 3), alter- nated HCS sandstone and mudstone (Facies 4), and amal- gamated HCS sandstone (Facies 5) in ascending order. Another type of the coarsening-upward intervals is also composed of the Facies (2-4) capped by tabular cross- stratified sandstone (Facies 6). That is, Facies (6) replaces Facies (5) in the uppermost part of the interval. Facies (5) and (6) do not coexist within a single cycle. Mudstones (Facies 2).—This facies conformably covers the basal sandstone (Facies 1), and characterizes the lower- most part of the progradational coarsening-upward interval (e.g., Cycle W3; Figure 5). It consists of dark gray lami- nated or bioturbated mudstone 5-40 m thick. Very fine sandstone beds (less than 5 cm thick) are occasionally in- tercalated in the mudstone (Locs. 4402, 6001a, 6050). Yoldia-Nucula Assemblage (Figure 8; described later) and Phycosiphon ichnosp. are abundant in the bioturbated parts (Figure 6G). Mudstone interbedded with very thin sandstone beds (Facies 3).—This facies changes transitionally from the un- derlying mudstone (Facies 2) (Loc. 6012 etc.), or directly covers the basal sandstone (Facies 1) (Locs. 6012 and 6100). It attains 3-10 m thickness (Locs. 4404, 6003, 6052 etc.), and is characterized by mudstone interbedded with very thin sandstone bed of less than 15 cm thickness. The sheet sandstone is very fine, and shows parallel, cur- rent and wave ripple laminations. Primary sedimentary structures are sometimes disturbed by Phycosiphon ichnosp. (Figure 4F). The intensely bioturbated part which directly covers the basal sandstone yields various types of ichnofossils (Planolites, Paleo- phycus, Rosselia, Skolithos etc.; Locs. 6088, 6100), and molluscan fossils such as Acila ashiyaensis and Dentalium sp. etc. (Figure 8). Alternation of HCS sandstone and mudstone (Facies 4).— This facies overlies Facies 3, and is capped with the Facies (5) or (6). It is 3-20 m thick and consists of alternations of sandstone and mudstone (Locs. 6017, 6047, 6101 etc.). The sandstone beds are 15-150 cm thick and tend to thicken upward, and each bed has a slight erosional base. Hummocky cross stratification, parallel lamination and wave ripples are well observed in the sandstone without re- markable signs of bioturbation. In contrast, the inter- bedded mudstone is commonly bioturbated by Phycosiphon ichnosp. (e.g., Cycle W3 at Loc. 6017). In Cycles W9 and W10, both sandstone and mudstone are exceptionally in- tensely bioturbated by Phycosiphon and Planolites ichnospp. (Locs. 6089, 6102: Figure 4G), and also yield Teichichnus and Rosselia ichnospp. Rosselia burrows show the upward removal trails to escape from rapid burial (Nara, 1997). Amalgamated HCS sandstone (Facies 5).— This facies consists of amalgamated HCS sandstone, 10 m thick, at the top part of the cycle (Locs. 6026, 6048; Figure 4H). The sandstone is clean, well-sorted and very fine-grained. Primary sedimentary structures, such as hummocky cross- stratification, are well preserved. Mudstone and wave rip- pled sandstone beds, 20 cm thick, are rarely intercalated in the sandstone. The top of this facies yields many Ophio- morpha burrows (Loc. 6027). Tabular cross-stratified sandstone (Facies 6).—Some cycles have tabular cross-stratified sandstone (6) at the top, Figure 7. Bivalve fossils from the Waita Formation (D, R X0.9; I, M, 0, Q X2; N X2.5; J, P X3: others X1). A, B. Glycymeris cisshuensis Makiyama, Cycle WS at loc. 6043. C. Phacosoma chikuzenensis Nagao, Cycle W9 at loc. 6083. D. Monia sp. Cycle W3 at loc. 6008. E: Chlamys sp. Cycle W10 at loc. 6098a. matsumotoi (Nagao), Cycle W10 at loc. 6083. O. Saccella sp., Jinnobaru F. at loc. 3100. Cultellus izumoensis (Yokoyama), Jinnobaru F. at loc. 3100. F-J. Venericardia subnipponica Nagao, F, G, H; Cycle W1 at loc. 4309. L. Crassatella yabei (Nagao), Cycle W5 at loc. 6043. P. Nucula sp., Cycle W2 at loc. 6001a. I, J; Cycle W2 at loc. 600la. K. Pitar M,N. Yoldia sp., Cycle W2 at loc. 6001a. Q. Angulus maximus (Nagao), Cycle W2 at loc. 600la. R. All specimens in this figure are housed in the Kyoto University Museum. 110 Norihiko Sakakura Gastropoda | others | S 2 2 2 5 E à 2 ° Q = = 2 © © & u 2 | S |u a Ss a N us ala elle g 2 SRE = 2 g AE sı5| [s|sS S|„|& 2 Ss 88/2 |, = o E SH SSG le SIE|ISa|S|S|S|a|S |, Ss |» SIEIS 0 le a |S 8 s[s/s[l2l=2]j5 5.853 5823/88 ls) je) a/F/315 8 8 e|2 |, is 18 5 Sxtlgls ls le) Si) SlS élus |sls als eg SR leis == SlSS 218 S|S/|8|)2|S|E|e|e|J|e|2 | SIS ÈS IS |sSlsls EIS |=1S ss |S|15 |3 IS 12 |8| 5 /|o | oa | 8|s S|2|2|5S | S|82|s <|8| 85 S sıIS|a|= | = |2|82 | 8 |S |£ s|S5S|2|s/|s|ıS|IS | S|s|S | S|sSs | S S|T | 2/|8|5S|S S|S/|a|E/|E|S|E IE ls |S = BARRES Elo |Ss|s|0°|s S | © o£ |3 © 2. |S &)|=/5])5|5|>2/5|S|<|S |E|S JS lala |< JA IIS 2 à [WIR (8 (2 [JS |S lo | a eee — © > © > = © = = © £ T © wn lité IL Ee ees] | | TN PR Nero 1 Sie] se Ea eas | _ eer ee ee IE TT ® EE TE &b an SLC eee ae ae a eo) OS eee ae N | Figure 8. Fossil list in the Waita Formation (route map area). Numbers of articulated bivalve shells is parenthesized. Paleogene bivalve taphonomy 111 A: Venericardia subnipponica 90° dl B: Crassatella yabei Figure 9. A-C show total modes of lateral inclination of commissure planes. Diagrams showing orientation of articulated bivalve shells in outcrop. A. Crassatella yabei at Loc. 6097, C. Cultellus izumoensis at Loc. 600la, D. Angulus maximus (tellinine bivalve) at Loc. 6001a. Lateral inclinations MORE THAN 45° are stippled by dark or light. 90° posterior, 10 5 = 45° 0 0° C : Cultellus izumoensis ae valve 7 —10° right valve 5 10 D : Angulus maximus Venericardia subnipponica at Loc. 6097, B. Left diagrams in Right dia- grams in A-C show posteriorwardl direction of selected specimens maintaining their standing positions in the left diagrams (lateral inclinations more than 45° are stippled samples of left diagrams). about 60°. either left or right. instead of Facies (5). Facies (6) consists of tabular and trough cross-stratified fine sandstone 10-15 m thick. Single sets of tabular and trough cross-stratified beds range from 20 to 40 cm thick. Herringbone cross-bedding, tidal- bundle sequences and reactivation surfaces are well ob- served in the facies (Locs. 6060, 6092, 6102; Sakakura and Masuda, 2001). Lenticular and flaser bedding, 20-30cm thick, is rarely intercalated in the tabular and trough cross- Stratified sandstone (Loc. 6070). As in Facies (5), the top of this facies yields many Ophiomorpha burrows (Locs. 6094, 6104). Interpretation of sedimentary environments Sedimentary environments of transgressive basal sand- stone (Facies 1) The transgressive basal sandstone can be interpreted as the deposits of relative sea level rises during transgression, because signs of wave influence clearly decrease upward. At the base of the basal sandstone (Facies 1), the wave dune is observed on the erosional surface. Such wave These articulated shells mainly are elevated in the posterior direction of shell length at angles of Darkly or lightly stippled blocks correspond to those areas in left diagrams. Most articulated Angulus maximus lie keeping their right valve up. D indicates dips of commissure planes and upper valve dunes strongly suggest deposition under the intense influ- ence of waves in shallow environments (Cheel and Leckie, 1992). No sedimentary structures formed by waves are observed in the upper part of the basal sandstone. Therefore, the upper part of this facies is interpreted to hav- ing been deposited below the storm wave base. The view is supported by the fining-upward features of these deposits and the bivalve assemblages whose contents and modes of occurrence differ clearly between the lower and upper parts (discussed later). Sedimentary environments of coarsening-upward inter- vals (Facies 2-6) Progradation of wave-dominated shoreline (Facies 2- 5).—The progradational coarsening-upward intervals com- posed of Facies (2-5) shows wave-influenced sedimentary structures such as wave ripples and hummocky cross- stratification increasing upward. Facies (2) is the lowermost part of this coarsening- upward interval, and shows no signs of wave-influenced sedimentary structures. It gradually changes upward into 112 Scattered shells: N=25 10 Assemblage (d): Loc. 4308 Re Rs à 20 40 Scattered shells: N=30 Assemblage (d): Loc. 6001 Mudstone Dispersed shell patches: N=113 Assemblage (ct): Loc. 4301 Scattered shells: N=130 Assemblage (b2): Loc. 6098 ® 8 © + u © = @ 2) = q u ® 2 wa = © fe EH X = Venericardia shell diameter (mm) Y = number of Venericardia valve A Figure 10. Glauconitic sandstone bed Norihiko Sakakura Thin autochthonous shellbed: N=145 Assemblage (c2): Loc. 6011 20 40 (mm) Autochthonous shellbed: N=371 Assemblage (c2): Loc. 6010 20 40 (mm) B (Top part of trans. basal sandstone in Cycle W3) A. Size distribution patterns of Venericardia subnipponica shells that occur as scattered shells or dispersed shell patches from the basal sandstone (Facies 1) and mudstone (Facies 2). In the basal sandstone, Venericardia shells vary in size from less than 10 mm diameter to up to 50 mm. The size-distributional patterns show wide level-curves rather than polymodal ones. B. Size-distribution patterns of V. subnipponica shells accumulated into autochthonous shellbeds at the top of the basal sand- The shell size-distribution pattern in the lower shellbed has a broad range from 2 mm to 48 mm and a gentle and inclined “peak” at 6-8 mm. lying mudstone (Facies 2). stone. In contrast, only small shells, less than 15 mm, occur from the over- In contrast, the pattern in the upper shellbed has a very strong mode at 2-4 mm for about 50% of the total number of valves, and with 85% concentrated in the 0-6 mm range. the overlying Facies (3) in which wave ripple are observ- able. These features suggest that Facies (2) was deposited below the storm wave base in an outer shelf environment. Facies(3) and (4) are usually intercalated between the hemipelagic Facies (2) and the amalgamated HCS sand- stone (Facies 5). They are characterized by alternation of sandstones that exhibit wave ripples and hummocky cross- stratification, and mudstone. Hummocky cross-stratifica- tion is well known in episodic storm deposits (e.g. Dott, Jr. and Bourgeois, 1982). On the other hand, the mudstone represents hemipelagic deposition during fair-weather con- ditions. Thus, the alternation of sandstones and mudstone (Facies 3 and 4) may suggest deposition above storm wave base and below fair-weather wave base. The amalgamated HCS sandstone (Facies 5) is the upper- most part of the coarsening-upward interval. This facies is characterized by amalgamated HCS sandstones with few intercalations of hemipelagic mudstone, and indicates deposition above fair-weather wave base. These charac- ters of this facies are typically found in lower shoreface de- posits (Walker and Plint, 1992). The coarsening-upward interval composed of Facies (2-5) may record a successional environmental change from below storm wave base to lower shore face. Such a successional change reflects the progradational processes of a wave-dominated shoreface (e.g., Walker and Plint, 1992). Progradation of a wave- and tide-influenced shoreline (Facies 2-4 and 6).—Another coarsening-upward interval similarly consists of Facies (2-4) in its lower and middle parts. However, the uppermost part of the interval is re- placed by the tabular cross-stratified sandstone (Facies 6), instead of amalgamated HCS sandstone (Facies 5). The tabular cross-stratified sandstone (Facies 6) overlies inner shelf deposit (Facies 4) and exhibits many tide-influ- enced sedimentary structures such as herringbone cross- stratification, tidal-bundle sequences, reactivation surfaces, and lenticular and flaser bedding (Nio and Yang, 1989). Based on these features, Facies (6) is interpreted to have accumulated in subtidal or intertidal environments. The progradational coarsening-upward interval with tidal deposits (Facies 6) at the top also reflects progradational process. In contrast to the coarsening-upward interval of a wave-dominated shoreface, however, it was deposited in a tide- and wave-influenced shelf. Such progradational Paleogene bivalve taphonomy 113 characterisitic species associated species modes of occurrence Mudstone (b) Venericardia - Crassatella = Ss © + [7 T = iS a = a a 8 2 = a a = = OD a = = = m (a) Glycymeris - Phacosoma Figure 11. Schematic diagram of bivalve assemblages, showing their compositions, typical modes of occurrence and grain size distributions of the host sediments. The lowermost Glycymeris-Phacosoma Assemblage (a) occurs from the well-sorted medium-grained sandstone (Facies 1) as an allochthonous shellbed on the basal erosional surface. On the other hand, the Yoldia-Nucula Assemblage (d) indigenously occurs from poorly sorted siltstone (Facies 2). The Venericardia-Crassatella and Venericardia Assemblages (b, d) show intermediate taphonomic features between the erosional phase and the muddy quiet phase in each cycle. deposits on a tide- and wave-influenced shelf was reported Meaning of redefined sedimentary cycle by sequence from the Devonian of the central Appalachian and upper stratigraphy Precambrian of Scotland (Prave er al., 1996; Kessler and After revision of the cycle boundaries, every cycle can Gollop, 1988). be redefined as a pair of the transgressive basal sandstone that exhibits the decreasing of wave influence, and the progradational coarsening-upward interval of the regressive phase. The new definition seems quite consistent with a 114 (d) Yoldia-Nucula 3: Loc.6012; N=29 12 cr - Maxium fooding surface -- > (c2) Venericardia _ 11 Loc. 6011; N (c2) Venericardia WEL Loc. 6010; N=185 (c2) Venericardia NN: NN: =128 10 sandstone Loc. 6008: N=110 (c1) Venericardia Loc. 6006; N=72 Transgressive basal (a) Glycymeris-Phacosoma DAFT LLC HAST T cs SR NN a 88 ISIN RS NN NN IN Loc. 6005; N=69 J------. Ravinement surface--- A : Cycle W3 Figure 12. mudstone (Facies 2). Norihiko Sakakura REA Glycymeris Phacosoma Crassatella Venericardia IM] Yoraia EI Nucula Cultellus Pitar Angulus ‘| Chlamys [|The ohters [isa] Saccella @ Wave-generated allochthonous shellbed } Indigenous shell patch, scattered shells © Autochthonous shellbed Gl. Glauconite sc... Maxium fooding surface ? ardi Crassatella ae. 34 | ( Loc. 6098: N=116 + eens x Venericardia-Crassatella Loc. 6097; N=55 Glycymeris-Phacosoma Loc. 6096; N=108 ‘.--- Ravinement surface--- Trans. basal sandstone B : Cycle W10 Successive change of fossil bivalve composition in the transgressive basal sandstone (Facies 1) and the lower part of the overlying A. Cycle W3 and B. Cycle W10 are the most typical examples. Four assemblages can be discriminated. Glycymeris-Phacosoma Assemblage (a) is replaced upward by the Yoldia-Nucula Assemblage (d) via the Venericardia-Crassatella (b) and Venericardia Assemblages (c). Although all of these assemblages are not always observable in a cycle, the successive change is widespread in every cycle in the Waita Formation. framework of sequence stratigraphy. The basal sandstone and the coarsening-upward interval reflect the transgressive and high-stand systems tracts, respectively (Posamentier and Vail, 1988). The distinct erosional surface at the base of every cycle probably corresponds with the ravinement surface (transgressive surface; Swift, 1968; Nummedal and Swift 1987), and the glauconitic sandstone beds in the top part of the transgressive basal sandstone in the Cycle W3 (Figure 6E) is regarded probably as the condensed section (Loutit et al., 1988) at maximum flooding surface, which is generated by low sediment supply and slow deposition. Revision of the sedimentary cycles provides a simple but more reasonable paleoenvironmental framework for further studies on paleoecology. Succession of molluscan assemblages Molluscan assemblages Molluscan fossils occur abundantly in, and are stratigraphically restricted to, the transgressive basal sand- stone (Facies 1) and the overlying mudstone (Facies 2 and 3) in the lower part of each cycle (Figures 3, 5 and 7). Four different fossil assemblages are distinguished from the viewpoints of faunal composition and modes of occurrence. These four assemblages occur successively within a sec- tion, appear repeatedly in every cycle in the same order, and show characteristic taphonomic features. I have ex- amined their modes of occurrence, paying particular attention to articulation and burial position of the shells, shell fabric and fragmentation in shellbeds, articulated bi- valve fossils still in life position, and shell size distribution Paleogene bivalve taphonomy 115 (Figures 6, 9 and 10). Figure 11 summarizes the contents and modes of occurrence of the four assemblages. The grain size distribution of their host sediments was investi- gated in detail by a settling tube system. The settling dis- tance was 150 cm, and the cumulative sediment weight was automatically logged by computer. (a) Glycymeris-Phacosoma Assemblage.—This assem- blage is characterized by Glycymeris cisshuensis and Pha- cosoma chikuzenensis, and is associated with Pitar matsu- motoi, Crassatella yabei etc. (Figures 8, 11, 12). The assemblage (a) characteristically occurs in clean sandstone, which rests directly on the erosional basement (ravinement surface) of the transgressive basal sandstone (Figure 12). The occurrence interval is 50-100 cm thick above the base. The host sandstone is massive or some- times mottled by bioturbation (Figure 4C, D), and is fine- to medium-grained. The shells are densely concentrated as an allochthonous shellbed of 20-50 cm thick, on an erosional surface at the base of the cycle (Locs. 6005, 6043, 6096; Figure 4A). The erosional surface shows wavy undulation, whose relief is up to 20 cm high. Bivalve shells are usually disarti- culated and somewhat fragmented. They are sometimes piled up and imbricated bidirectionally along both slopes on the crest (Loc. 6005; Figure 6A). These features are characteristic of wave dunes (Cheel and Leckie, 1992). The assemblage consists mainly of medium- to large- sized shells (30-100 mm). Their calcareous shell tests are occasionally replaced by clay minerals (Figure 6E). A grain-size distributional pattern of the sandstone ma- trix is highly concentrated, and the mode lies on fine- grained sand size ( = 2.3 ; Figure 11). Very fine sand or finer grains (@ > 3) do not contribute much (Figure 11). (b) Venericardia-Crassatella Assemblage.—The assem- blage consists mainly of Venericardia subnipponica and Crassatella yabei (Figures 11, 12). It is subdivided into two subtypes by differences of the associated species. The first subtype (bl) is associated with Phacosoma chikuze- nensis and Pitar matsumotoi which are common in the Glycymeris-Phacosoma Assemblage (a) (Locs. 6082, 6097: Figures 8, 11, 12). The second subtype (b2) is character- istically associated with epibionts represented by epifaunal byssally attached bivalves, Chlamys sp. and Monia sp., and by barnacles, which attach to molluscan shell surfaces (Locs. 6098a and 6109: Figures 6B, 8, 11, 12). The first subtype assemblage with Phacosoma and Pitar (bi) occurs from medium to fine-grained sandstone in the lower to middle parts of the transgressive basal sandstone (Figure 12). The shells occur as allochthonous shellbeds of 20 cm thick on wavy erosional surfaces (Locs. 6082, 6097 etc.), much as those of the Glycymeris-Phacosoma Assemblage (a). Green smectite and pumice grains are common in the sandstone. Grain-size distribution of the sandstone matrix shows a moderately concentrated curve (Figure 11). The mode lies on fine-grained sand size (¢ = 2.2). Silt-size or finer grains, less than 4 @ in diameter, do not amount to much. The second subtype with epifaunal byssally attached bi- valves (b2) occurs from medium to fine-grained sandstone 1-2 m thick in the middle part of the basal sandstone (Figure 12). The second subtype assemblage (b2) includes articulated individuals of Venericardia subnipponica, Crassatella yabei and Chlamys sp. (Figures 11, 12). The shells are scattered about the bioturbated sandstone which includes smectite and pumice grains, and which has also lit- tle silt or finer grains (@ > 4). The grain-size distributional pattern is similar to that of the first type (bl; Figure 11). Articulated shells account for 32% of total V. subni- pponica and 18% of total C. yabei shells (Loc. 6098a; Figure 8). Some of them are still in their living position. For example (see Figure 9), twelve among 29 articulated individuals of V. subnipponica stand with their commissure plane almost vertical. In this case, most of the standing ones raise their posterior part upward with angles around 60° (Loc. 6098c; Figure 9A). C. yabei also exhibits trend similar to that of V. subnipponica but the burial pattern is much more dispersed (Loc. 6098c; Figure 9B). Some disarticulated and articulated bivalve shells are oc- casionally encrusted by barnacles. Epifaunal byssally at- tached bivalves such as Chlamys sp. and Monia sp. are typical examples. They are encrusted not only on the outer side of shells but also on the inner side (encrustation on the inner side indicates that it occurred after the death of the host bivalves). The barnacles keep their attaching col- ony on the encrusted shell, and the large barnacles shells are consecutively attached by small individuals of new gen- erations. Barnacles also occur as dislocated colonies and disarticulated shell fragments. The shells of the assemblage (b2) are sometimes accu- mulated as shellbeds, however, no erosional surface is ob- served at the base (Loc. 6109). The matrix of the shellbed consists of a mixture of many shell fragments showing imbrications, articulated shells filled by geopetal, and me- dium- to fine-grained sands (Figure 6C and D). Shell frag- ments are variously abraded (Figure 6C). Encrustation by barnacles is common on disarticulated bivalve shells (Figure 6B). In both subtypes (bl and b2), medium- and large-sized shells of V. subnipponica (20-40 mm) are abundant (Locs. 6083, 6095, 6098b). In contrast, small shells less than 10 mm in diameter are few. Figure 10A shows a size- distributional pattern of V. subnipponica shells that are scattered about the middle interval of the basal sandstone at Loc 6098b. The smaller-shell portion might have been trimmed off the original thanatocoenosis by fragmentation and winnowing out by wave currents or the replacement of 116 Norihiko Sakakura shell tests by clay minerals (Figure 6E). (c) Venericardia Assemblage.—The assemblage is char- acterized by abundant Venericardia subnipponica (Figures 11, 12). The assemblage can be subdivided into two sub- types, cl and c2, by difference of the associated species (Figure 11). The subtype (cl) consists mostly of V. subnipponica, and has very few associated species except for Cultellus izumoensis in places (Locs. 4310a, 4313, 6006 etc; Figures 8, 12). The subtype (c2) is characterized by a great quantity of V. subnipponica, and associated Pha- cosoma chikuzenensis, Pitar matsumotoi, Monia sp. and Crassatella yabei (Locs. 6009-601 1a; Figures 8, 12). The subtype (cl) occurs commonly from very fine sand- stone 8-20 m thick in the middle to upper part of the transgressive basal sandstone (Figure 12). The sandstone yields many Thalassinoides burrows (Figure 4C). The Venericardia Assemblage (cl) occurs from much more fine-grained deposits than the assemblages (a) and (b). The grain-size distribution curve shifts fineward, and the mode lies on very fine sand size (@ = 3). Coarse and me- dium-grained sands are few. The subtype (cl) occurs as indigenous shell-patches (Figure 11) or scattered shells. Venericardia subnipponica sometimes forms a shell clump composed of tens of articu- lated individuals (Locs. 4313, 6006; Figure 6F). They fre- quently keep their living position in bioturbated very fine sandstone. Size distribution pattern of V. subnipponica in the subtype (cl) has a wide range (4-40 mm) and poly- modal curve (Loc. 4310b; Figure 10A). These features might result from overprinting of indistinguishable popula- tions because of sampling from the thick interval of bioturbated and mottled sandstone. On the other hand, Subassemblage (c2) is restrictedly found only from a glauconitic sandstone bed at the top of the transgressive basal sandstone in the cycle W3 (succes- sive Locs. 6008, 6010a and 6011a; Figure 12). The shells of the Subtype (c2) accumulated as an autochthonous shellbed (Figures 10B, 11, 12), which contained articulated large Monia sp. that probably attached to other shells with a byssus, particularly in their early growth stage (Loc. 6008; Figure 7D). The grain-size distribution curve of the host rock has a mode at very fine sand (@ = 2.4; Loc. 6010a; Figure 11), which is slightly coarser than the host rock of the subtype (cl). A great quantity of disarticulated V. subnipponica shells constructs a shellbed 40-60 cm in thickness (Loc. 6010b, Figure 10B). The shellbed starts with a gradual increase of shell content in the lower 20 cm interval, and ends at a sharp top. The shells are oriented at random, and are occa- sionally attacked by boring polychaetes. The shellbed also yields articulated individuals of V. subnipponica and P. matsumotoi (Figure 8), some still in their living positions. A quantity of V. subnipponica shells has a broad range in shell diameter from less than 2 mm to 48 mm. The histo- gram of the shell size distribution shows a mode at 6-8 mm. for 44 valves of 317; it forms a broad and inclined “peak” that rises swiftly from the smallest shells then de- clines gradually to the largest ones (Figure 10B lower). In the transitional zone from glauconitic sandstone to mudstone (Facies 2), the subtype (c2) is composed particu- larly of many small V. subnipponica shells accompanied with Angulus maximus, an associated species of the Yoldia- Nucula Assemblage (d) at Loc. 6011a (discussed below; Figures 8, 12). Many small V. subnipponica shells are concentrated into a thin shellbed 2-5 cm in thickness. The histogram of the shell diameter distribution shows a high mode at the 2-4 mm; range, in which about 50% of the total of 145 valves are included. More than 85% of the valves fall in the range of 0-6 mm, and otherwise medium- sized shells (10-30 mm) account for only about 7% (Loc. 6011b; Figure 10B). A similar distributional tendency of V. subnipponica shell diameters is represented in the Yoldia -Nucula Assemblage (d) (described immediately below). (d) Yoldia-Nucula Assemblage.—The assemblage con- sists mainly of Yoldia sp., Nucula sp., Angulus maximus, Cultellus izumoensis, Venericardia subnipponica, Dentali- um sp. (Locs. 6001a and 6012; Figures 8, 11, 12). Unlike the other assemblages, the Yoldia-Nucula assemblage oc- curs from the bioturbated mudstone (Facies 2; Figure 6G) which overlays the basal sandstone (Facies 1) at Locs. 4308a and 6012 (Figure 10), and the grain size distributional pattern shows a broad curve extending from fine sand size (@ = 2) to silt size (9 = 5; Figure 11) without an obvious peak. Usually, the molluscan fossils are scattered about the mudstone (Figure 6G). Some bivalve shells of Yoldia sp. and Nucula sp. are articulated and arranged at random. Most Cultellus izumoensis shells are articulated (Loc. 6001a; Fgiure 8). Among 26 articulated individuals, fif- teen C. izumoensis stand with their commissure plane subvertical, and frequently the posterior part is raised up- ward at angles around 60° (Loc. 6001c; Figure 9C). The shells of Angulus maximus (= tellinine bivalve) are also ar- ticulated in high numbers (Loc. 6001a; Figure 8), and retain their living position, in which their right-warped siphonal gape is oriented upward. Their articulated shells lie hori- zontally in the matrix still keeping their right valve upper- most. (Loc. 6001c; Figure 9D). Shells of Dentalium sp. and Turritella karatsuensis occur occasionally as allochthonous shell stringers (Kidwell et al., 1986) on minor erosional surfaces (Loc. 6001a). The horn- or drill-shaped shells are concentrated in parallel and arranged into a scar 50 cm long and 20 cm wide, and their apices are unimodally pointed (Figure 6H). Venericardia subnipponica occurs not only from the basal sandstone (Facies 1) but also from the mudstone Paleogene bivalve taphonomy 117 (Facies 2). In the Yoldia-Nucula Assemblage (d), V. subnipponica is a subordinate species, and is represented only by small individuals. It accounts only for 4.1% of in total 97 individuals in the assemblage (b) at Loc. 6001a (Figure 8). Figure 10A show two shell diameter distributional histograms at localities 6001b and 4308b. The pattern at Loc. 6001b has a mode at 6-8 mm, and shells larger than 12 mm diameter are scarce. Successive occurrences of molluscan assemblages The molluscan assemblages change successively in up- ward sequence within the transgressive basal sandstone and the overlying mudstone in each cycle. The successive oc- currences are similarly made up of, in ascending order, the (a) Glycymeris-Phacosoma Assemblage, (b) Venericardia- Crassatella Assemblage, (c) Venericardia Assemblage and (d) Yoldia-Nucula Assemblage (Figure 11). Their succes- sive occurrence is never reversed in order, and is uniformly repeated in every sedimentary cycle, though all the four as- semblages are not always completely observable within a cycle. Related to the faunal change, their typical modes of occurrence shift upward from allochthonous shellbed into indigenous shell clumps and patches. The most typical examples of the Cycles W3 and W10 are summarized in Figure 12. In cycle W3 (Locs. 6005- 6012; Figure 12A), the faunal succession starts with the Glycymeris-Phacosoma Assemblage (a), which occurs only as the basal allochthonous shellbed with wave dunes at the base of the cycle (Locs.6005). The Venericardia-Crassa- tella Assemblage (b) is skipped there. The lowermost as- semblage (a) is replaced upward directly by the Veneri- cardia Assemblage (c) at the 3 m-level above the base. The top part of the occurrence range of the assemblage (c) intercalates with V. subnipponica shellbeds in glauconitic sandstone bed that indicates the surface of maximum trans- gression (11-12 m level in figure 12A). The shellbeds also yield a few Phacosoma chikuzenensis and Pitar matsumotoi, both of which are associate species of the Subassemblage (c2). The indigenous Yoldia-Nucula Assemblage (d) appears at the 12.5 m-level as the lithology changes quickly from sandstone to the overlying mudstone (Facies 2). The faunal succession is almost identical in the Cycle W10, but is condensed within a thin basal interval (0-2 m level in Figure 12B). The Glycymeris-Phacosoma Assemblage (a) is also dominant on the basal erosional sur- face, and is similarly replaced upward by the Venericardia -Crassatella Assemblage (bl) on the erosional surface at the level of 0.5 m above the base (Loc.6096-6097; Figure 12B). The latter assemblage (bl) is immediately succeeded by another subtype (b2) of the Venericardia- Crassatella Assemblage with abundant epibionts, such as Chlamys sp., Monia sp. and barnacles, at the level of 0.7 m above the base (Loc. 6097, 6098a: Figure 12B). The oc- currence range of Assemblage (b2) encompasses 1.5 m in thickness, and is terminated with an increase of mud con- tent in the host rock (Figure 12B). Discussion Taphonomic implication of faunal change in cycles Molluscan fossils mostly occur from the lower part of each cycle, i.e., the transgressive basal sandstone (Facies 1) and the mudstone (Facies 2) that had been deposited during the earliest regressive phase (Figure 12). Four distinctive fossil assemblages are preserved in this relatively thin part. Close taphonomical observation can “decode” the hidden paleoenvironmental and paleoecological changes con- densed in this transgressive interval in high resolution. The lowermost Glycymeris-Phacosoma Assemblage (a) occurs only as allochthonous shellbeds on the erosional base of the transgressive basal sandstone (Figures 11, 12). Most of the shells are disarticulated completely and frag- mented considerably there, and often form wave dunes (Cheel and Leckie, 1992: Figure 6A). The matrix of the host rock is well-sorted, fine-grained sandstone, and the mud content is small (Figure 11). These features strongly suggest deposition under intensely wave-influenced condi- tions, in which the sea bottom is frequently eroded and shells are easily winnowed. The molluscan shells in this assemblage might be reworked repeatedly even if they were not transported horizontally far from their habitats. The succeeding Venericardia-Crassatella Assemblage associ- ated with Phacosoma and Pitar (bl) occurs also as wave- influenced shellbeds on additional minor erosional surfaces (Figure 11) In contrast, no signs of bottom erosion and shell rework- ing by wave currents are observable in the upper part of Facies (1) and, also in Facies (2). The Venericardia Assemblage (c) consists partly of autochthonous or indige- nous shell patches. in the upper part of the basal sandstone (Facies 1), whose grain size distributional pattern shifts fineward (@ > 3: Figure 11). The uppermost Yoldia-Nucula Assemblage (d) occurs mostly as indigenous scattered shells in the overlying mud- stone (Facies 2; Figure 12). Their shells are often articu- lated and found in their living positions (Figure 10). These are no signs of bottom erosion and shell reworking. The host rock contains very fine sand (2 < @ < 3) but is dominated by muds (Figure 11). Allochthonous shells of Dentalium sp. and Turritella karatsuensis are sometimes accumulated in depressions on the bedding plane of the mudstone, and show preferred orientation (Facies 2; Figure 6H). The cause of such apex-oriented shell stringers is not attributable to waves but to unidirectional currents (Nagle, 1967; Figure 6H). 118 Norihiko Sakakura The successional change of these taphonomic features suggests that the faunal succession is closely associated with the upward decreasing of wave influence. The Glycymeris-Phacosoma Assemblage (a) is replaced upward by the Yoldia-Nucula Assemblage (d) via the Venericardia- Crassatella and Venericardia Assemblages (b, c), while the strong wave influence declines from the erosional and win- nowing phase to the quiet muddy phase through the trans- gression period. Successive faunal change within a sedimentary cycle is widespread and exhibited repeatedly in the Waita Formation. The Glycymeris-Phacosoma Assemblage al- ways occurs as the allochthonous shellbed, which corre- sponds to an onlap shellbed (Kidwell, 1991) on the ravinement surface that indicates early transgression. The other assemblages also retain the autochthonous or indige- nous occurrences above this onlap shellbed. Besides the Ashiya Group, similar faunal change in and above onlap shellbeds is observable in the other Paleogene deposits (e.g., the Nishisonogi Group and Hioki Group). Therefore, it seems one of the basic sedimentological and paleoecological features of the Paleogene deposits in west Japan. Epibionts-enriched fauna The successive faunal records are sometimes condensed within a very short interval in a cycle, for example, within an interval of 2 m thick from the base in the cycle W10 (Figure 12). Intermittent and limited deposition of this in- terval is suggested by abundant occurrence of epibionts. Epifaunal byssally attached bivalves: Chlamys sp. and Monia sp., and barnacles occur commonly as associated species of the Venericardia-Crassatella Assemblage (b) from the lower middle part of the transgressive basal sand- stone (Figure 12). Some of them are found in the attach- ing position in situ (Figure 6B), while others are fragment- ed, abraded, and finally assimilated into the shellbed matrices showing imbrications (Figure 6C). Scarcity of fine-grained sediments in the matrix also implies that this component was winnowed out and swept away by currents (Subassemblage b2; Figure 11). These epifaunal byssally attached bivalves and barnacles require the peculiar condition that their attachment to shelly ground avoids burial by the winnowing out of sediments. A number of shells have been attached by plural genera- tions of barnacles (Loc. 6098a). Some other shells have repeatedly settled by epibionts after death. Chlamys and Monia probably attached to other shells by their byssus at least in the early ontogenetic stage, although the attachment position is not observable in the fossil record since the byssus is missing. The line of evidence converges to an argument that the shelly ground, which lifts the restriction on the migration of the epibionts, was exposed for a long time. The signs of taphonomic feedback , by which the skeletal remains of dead organisms impact on the next liv- ing community (Kidwell and Jablonski 1983), are obser- vable in places (Locs. 6008, 6098a and 6109). The epifau- nal byssally attached bivalves cannot survive on the sea- floor in which sediments are rapidly and continuously de- posited; the same is true of the cemented barnacles, because they have neither a foot to escape rapid burial nor a siphon (Stanley, 1970; Kranz, 1974). The epibiont-rich shellbeds at least in three cycles might indicate strong or gentle cur- rent-influenced conditions in which sedimentation was in- termittent, and probably, relatively slow. Autochthonous shellbed in glauconitic sandstone The glauconitic sandstone bed at the top of the transgressive basal sandstone intercalates with autochthonous shellbeds composed of a great quantity of Venericardia subnipponica shells (Subassemblage c2; Locs. 6010 and 6011). Unlike the allochthonous shellbed on the ravinement surface at the base of the cycle, the shellbed at the top is autochthonous because bivalve fossils often keep their living position (Figures 10B, 12). Abundant glauconite grains in matrices (Figure 4E), which develop in areas characterized by low sedimentation (Chamley, 1989), imply condensation as a process of shell accumulation in situ during a relatively long period. This view is also supported by the occurrence of epifaunal byssally attached bivalves such as Monia sp. The shell diameter distributional pattern of V. subnipponica in this shellbed is shown in Figure 10B (lower). These shells range in length from 2 to 48 mm, with a low mode at 6-8 mm. This may suggest a continu- ous and stable supply of dead shells of all growth stages in situ, which consist of many juveniles and a few mature specimens, except for very small juveniles that have little fossilization potential. As noted above in the sequence stratigraphic interpretation of the sedimentary cycle, the glauconitic sandstone where the autochthonous shellbed lies is regarded as a condensed section associated with the maximum-flooding surface (Figures 5, 12B). The autochthonous shellbed in the glauconitic sandstone probably reflects attrition from a normal population or “ce- metery” (Ager, 1963; Dodd and Stanton, Jr., 1990). It is produced by repetitive colonization of Venericardia subni- pponica populations in situ under low sedimentation rate during the maximum-flooding period. Such a shellbed at the top of a transgressive deposit is classified as a backlap shellbed by Kidwell (1991). On the other hand, another autochthonous shellbed is in- tercalated in the transitional zone from the glauconitic sandstone to overlying mudstone (Facies 2) (Figure 10B, upper). It is composed mostly of small shells of Venericardia Paleogene bivalve taphonomy 119 subnipponica, some of which are articulated (Figure 10B). In contrast to the Venericardia Assemblage in the glauco- nitic sandstone, the size-distributional pattern of the present species shifts strongly to the smallest portion (Figure 10B upper). The mode of the histogram lies at 2-4 mm, in which more than 50% of the total individuals are concen- trated. These features probably suggest that a mass mor- tality of juvenile shells occurred after an opportunistic larval settlement, and that these shells represent a census population (Ager, 1963; Dot and Stanton Jr., 1990). Venericardia is a typical infaunal nonsiphonate suspen- sion feeder having limited mantle fusion. They are usually shallow and slow burrowers (Stanley, 1970), and have low escape ability from rapid burial (Kranz, 1974). Con- sequently, the mass mortality may be involved with the in- cidental deposition of soupy muds that caused an obrution. The population of Venericardia juveniles might be smoth- ered by the obrution event in the transitional phase between condensed glauconitic and muddy. It should be noted that Venericardia populations in the overlying mudstone (Facies 2; Yoldia-Nucula Assemblage) are also restricted to small-diameter shells. Conclusion Based on detailed observations, 11 sedimentary cycles in the upper part of the Ashiya Group (upper Oligocene) were revised and redefined here (Figure 5). Each cycle consists of a basal erosional surface overlain by a transgressive basal sandstone and a progradational-interval of mudstones and sandstones. In this revision, every cycle is bordered by an erosional surface at the base of a fossiliferous sand- stone. Four molluscan fossil assemblages are distin- guished. They exhibit similar successive occurrences accompanied with transitions of sedimentological and taphonomical features. These are a key to understanding the Paleogene stratigraphy and paleoecology, because simi- lar successive occurrences of bivalve fossils are widespread in other Paleogene deposits in western Japan (i.e., Nishi- sonogi and Hioki Groups). The successive occurrence of bivalve fossil faunas is interpreted to result from trans- gressive-regressive shifts in sedimentary regimes (variable wave influence and sediment supply). Paleoecological aspects of Paleogene bivalves, for exam- ple Venericardia, still remain obscure. Unlike Neogene or Quaternary fauna, direct analogies from the ecology of modern relatives should not be simply drawn for Paleogene bivalves. On the other hand, taphonomic and sedimento- logic aspects can be directly read from the strata. Sedimentary regime seems to be a factor in defining the habitats of bivalves, and is regarded as the most important environmental factor controlling morphologic adaptations of bivalves (Stanley, 1970), owning to their benthic habitat, which not only is closely related to the depositional sub- strate, but also contains many infaunal styles of burrowing into deposits. Therefore, taphonomic and sedimentologic observation will be a key to understanding the paleo- ecology of Paleogene bivalve fauna. Acknowledgments I would like to express my gratitude to H. Maeda (Kyoto University) for his critical reviews and kind guidance of the manuscript. I am deeply indebted to F. Masuda and T. Sakai (Kyoto University) for their sedimentological coop- eration in the field and laboratory, and to Y. Kondo (Kochi University) for his helpful suggestions and encourage- ments. Iam also grateful to S. M. Kidwell (University of Chicago) and an anonymous referee for their helpful comments to improve the manuscript. Thanks are also ex- tended to T. Komatsu (Kumamoto University) and B. Tojo (Kyoto University) for their valuable comments, and staff of Tsuyazaki Fishery Research Laboratory of Kyushu University for their help during fieldwork. This study has been partly supported by a grant-in-aid from the Fukada Geological Institute. References Ager, D. V., 1963: Principles of Paleoecology, 371 p. McGraw-Hill Co., New York. Cheel, R. J. and Leckie, D. A., 1992: Coarse-grained storm beds of the Upper Cretaceous Chungo Member (Wapiabi Formation), southern Alberta, Canada. Journal of Sedimentary Petrology, vol. 62, no. 6, p. 933-945. Chamley, H., 1989: Clay Sedimentology, 623 p. Springer-Verlag Berlin. Dott, J. R. and Stanton, Jr., R. J., 1990: Paleoecology, Second Edition, 502 p. A Wiley-Interscience Publication John Wiley and Sons, New York. Dott, Jr., R. H. and Bourgeois, J., 1982: Hummocky stratification: Significance of its variable bedding sequences. Geological Society of America Bulletin, vol. 93, p. 663-680. Hayasaka, R., 1991: Sedimentary facies and environments of the Oligocene Ashiya Group in the Kitakyushu-Ashiya area, Southwest Japan. The Journal of Geological Society of Japan, vol. 97, p. 607-619. (in Japanese with English abstract) Loutit, T.S., Hardenbol, J., and Vail, P.R., 1988: Condensed sec- tions: the key to age determination and correlation of continen- tal margin sequences. Jn, Wilgus, C. K. et al. eds., Sea-level Changes—an Integrated Approach, SEPM, Special Publica- tion, no. 42, p. 183-213. Kessler, L.G. and Gollop, Ian.G., 1988: Inner shelf/shoreface- intertidal transition, Upper Precambrian, Port Askaig Tillite, of Islay, Argyll, Scotland. /n, de Boer, P.L., van Gelder, A. and Nio, S.D. eds., Tide-influenced Sedimentary Environments and Facies, p. 341-358. D. Reidel Publishing Company, Boston. Kidwell, S. M., 1991: Condensed deposits in siliciclastic sequences: expected and observed features. /n, Einsele, G., Ricken, W. and Seilacher, A. eds., Cycles and Events in Stratigraphy, p. 182-195. Springer-Verlag, Berlin Heidelberg. 120 Kidwell, S. M. and Jablonski, D., 1983: Taphonomic feedback: eco- logical consequences of shell accumulation. Jn, Tevesz, M. J. S. and McCall, P. L. eds., Biotic Interaction in Recent and Fossil Benthic Communities (Topics in Geobiology 3), p. 195-248. Plenum Press, New York. Kidwell, S. M., Fiirsich, F. T. and Aigner, T., 1986: Conceptual framework for the analysis and classification of fossil concen- trations. Palaios, vol. 1, p. 228-238. Kranz, P. M., 1974: The anastrophic burial of bivalves and its paleoecological significance. Journal of Geology, vol. 82, p. 237-265. Mizuno, A., 1963: Paleogene and Lower Neogene biochronology of West Japan (III. Stratigraphic and geographic distributions of molluscan faunas in West Japan). The Journal of Geological Society of Japan, vol. 69, p. 38-49. (in Japanese with English abstract) Nagao, T., 1927a: The Palaeogene stratigraphy of Kyushu (Part 17). Journal of Geography, vol. 39, p. 665-674. (in Japanese) Nagao, T., 1927b: Palaeogene fossils of the Island of Kyushu, Japan, Part 1. Science Reports of Tohoku Imperial University, vol. 9, no. 3, p. 97-128. Nagao, T., 1928a: The Palaeogene stratigraphy of Kyushu (Part 20). Journal of Geography, vol. 40, p. 143-155. (in Japanese) Nagao, T., 1928b: Palaeogene fossils of the Island of Kyushu, Japan, Part 2. Science Reports of Tohoku Imperial University, vol. 12, no. 1, p. 1-140. Nagle, J. S., 1967: Wave and current orientation of shells. Journal of Sedimentary Petrology, vol. 37, no. 4, p. 1124-1138. Nara, M., 1997: High-resolution analytical method for event sedi- mentation using Rosselia socialis. Palaios, vol. 12, p. 489- 494. Nio, S. D. and Yang, C. 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Paleontological Research, vol. 6, no. 1, pp. 121-124, April 30, 2002 © by the Palaeontological Society of Japan SHORT NOTES Revision of an Ordovician cephalopod Ormoceras yokoyamai (Kobayashi, 1927) SHUJI NIKO Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, 739-8521, Japan (e-mail: niko@hiroshima-u.ac.jp) Received 27 August 2001: Revised manuscript accepted 20 November 2001 Key words: Llanvirn, Proteoceratidae, Treptoceras yokoyamai Introduction Systematic position of an Ordovician cephalopod Ormo- ceras yokoyamai (Kobayashi, 1927) is reconsidered on the basis of type specimens kept in the University Museum of the University of Tokyo (prefixed UMUT) and the new ma- terial from the type stratum Jigunsan Formation, Choson Supergroup in Gangwon-Do, South Korea. The Jigunsan Formation, named by Yamanari (1926), is a relatively thin (45-100 m in thickness) fossiliferous sequence of inter- beded shale and subordinate limestone. On the basis of studies primarily of trilobites and cephalopods, Kobayashi (1966) assigns the principal part of the formation to Llanvirn (upper Middle Ordovician). This correlation is in agreement with conodont biochronology by Lee (1977, 1980). The newly collected specimens come from float blocks of shale at (1) locality G90075, latitude 37° 10° 39.5” N, longitude 128° 42° 7.1” E, in a field on the south- western slope of Mt. Jigun, Jikdongri, Jungdong-myeon, Yeongwol-gun (UMUT PM 27827), and (2) locality J89105, latitude 37° 5° 42.4” N, longitude 129° 0° 52.6°° E, on the northern flank of a small tributary of the Hwangji River in Jangseong, Taebaek-city (UMUT PM 27828). Systematic paleontology ? Subclass Actinoceratoidea Teichert, 1933 ? Order Actinocerida Teichert, 1933 Family Proteoceratidae Flower, 1962 Genus Treptoceras Flower, 1942 Type species. — Orthoceras duseri Hall and Whitfield, 1875. Treptoceras yokoyamai (Kobayashi, 1927) Figure | Loxoceras yokoyamai Kobayashi, 1927, p. 186, 187, pl. 18, figs. 9a-c. Sactoceras yokoyamai (Kobayashi). Kobayashi, 1934, p. 439, 440, pl. 27, figs. 1-6, pl. 28, fig. 2. Ormoceras yokoyamai (Kobayashi). Yun, 1999, p. 214. Emended diagnosis.—Small species of Treptoceras with low angle (approximately 5°) of shell expansion, oval cross section with form ratio (lateral/dorsoventral diameter) 1.2-1.5; siphuncle submarginal with siphuncular position ratio (minimum distance of central axis of siphuncle from shell wall per dorsoventral shell diameter) approximately 0.2 in adoral shell; septal necks cyrtochoanitic to subor- thochoanitic; cameral deposits weak for genus. Description. — Small-sized orthocones for genus with gradual shell expansion indicating approximately 5° in dorsoventral plane (Figure 1.1); apical shell may be curved on the basis of a specimen (UMUT PM 0686 figured by Kobayashi, 1934, pl. 27, fig. 6); details of shell surface not observed in all examined specimens, but annulations and conspicuous ornamentation not detected; cross section of shell dorsoventrally depressed, oval with form ratio of 1.2 -1.5 (Figure 1.2), largest known specimen (UMUT PM 0685 figured by Kobayashi, 1934, pl. 27, figs. 3-5) attains 11.0 mm in dorsoventral diameter and 15.5 mm in lateral diameter, whose adoral part represents apical body cham- ber; sutures transverse to slightly oblique, nearly straight or weakly sinuate to form very shallow ventral and dorsal lobes in rare cases (Figure 1.1); camerae very short, giving width/length ratios which ranges from 4.6 to 10.9+, with shallow septal curvature (Figure 1.3); no septal furrow de- tected; adoral siphuncle stenosiphonate and submarginal in position, with siphuncular position ratio approximately 0.2 (Figure 1.3); septal necks cyrtochoanitic to suborthochoani- tic, not recumbent (Figure 1.4-1.7); well-preserved dorsal septal neck attains 0.27 mm in length at dorsoventral shell diameter of approximately 7 mm; adnation area usually 122 Shuji Niko Ordovician cephalopod Ormoceras 12 absent; connecting rings relatively thick, 0.05-0.07 mm, and undifferentiated (Figure 1.5), forming subglobular pro- file in apical dorsoventral section of a specimen (UMUT PM 0686) with maximum diameter/length ratio of siphuncular segments approximately 1.3, inflation then rap- idly decreases, creating fusiform to pyriform (and subglobular in rare cases) profile in adoral dorsoventral section with ditto ratio 0.6-0.9 (Figure 1.4, 1.5); curvature of septal brims and inflation of connecting rings are slightly stronger on ventral siphuncular side than on dorsal one (Figure 1.4, 1.5); cameral deposits weak for genus, re- stricted in apical camerae, composed of thin episeptal- mural and hyposeptal deposits (Figure 1.3). Endosiphuncular deposits are also restricted to apical siphuncle (Figure 1.3); laminated parietal deposits to form thick lining on ventral siphuncular wall (Figure 1.4, 1.6); thickness of ventral lining decreases at septal foramen and its surface usually linear in profile in longitudinal section (Figure 1.4, 1.6); parietal deposits rarely developed on dor- sal connecting rings, which interrupted at septal foramen (Figure 1.4); canal system and perispatium not developed. Discussion.— Morphologically, the most diagnostic fea- ture of this species is the structure of the endosiphuncular deposits that is observable in Kobayashi’s specimen UMUT PM 0687 (Figure 1.8), and a section from the new material, UMUT PM 27827 (Figure 1.3-1.6). Its combination of the characteristic parietal deposits that form the ventral lin- ing and lack of a canal system (Figure 1.4, 1.6) confirm systematic placement of the species in the Proteoceratidae rather than the Pseudactinoceratidae (Loxoceras M’Coy, 1844; Doguzhaeva and Shkolin, 1999) or the Ormocera- tidae (Ormoceras Stokes, 1840 and its subjective junior synonym Sactoceras Hyatt, 1884). In addition, the species does not exhibit an exogastric cyrtocone, surface annu- lations and strongly bulging suturai elements, which fea- tures are diagnostic only for two closely related genera, i.e., Treptoceras (some emendations to the generic diagnosis were added by Aronoff, 1979, and Frey, 1988) and Proteo- ceras (Flower, 1955; type species Ooceras(?) perkinsi Ruedemann, 1906). These genera can be distinguished by the degree of the siphuncular changes which are less drastic in Treptoceras duseri and the present Korean species (Figure 1.3) than in Proteoceras perkinsi. The siphuncular segments of Proteoceras shift from a subglobular form to a nearly cylindrical one in the space of 6-8 camerae. Accordingly, Ormoceras yokoyamai is attributed to Trepto- ceras. Although confident determination of the proteoceratid’s WwW higher taxonomic position is pending until the apical shell form is clarified, it is herein proposed that a possible origin of the Proteoceratidae was derived from the subclass Actinocerida. Flower (1962) placed the Proteoceratidae in the order Orthocerida of the subclass Nautiloidea, and his assertion was followed in the Treatise (Sweet, 1964) and by Aronoff (1979) and Frey (1988). However, the rapid de- crease of the siphuncular inflation of Proteoceras perkinsi, Treptoceras duseri, and T. yokoyamai is exceedingly un- usual for the subclass Nautiloidea, and it seems rather sug- gestive of a phylogenetic relationship with some actino- cerids including Paractinoceras (Hyatt in Zittel, 1900), Leurorthoceras (Foerste, 1921) and Kobayashiceras (Niko, 1998). Endosiphuncular lining deposits lacking radial canal and perispatium are also known in the adoral siphuncle of Kobayashiceras. This indicates that presence or absence of the canal system in the adoral shell is not al- ways essential for Actinoceratoidea. Material examined.—The holotype, UMUT PM 0016. The five specimens, UMUT PM 0683-0687, also identified as this species by Kobayashi (1934). In addition, the two new specimens of the imperfect phragmocones of UMUT PM 27827, 44.8 mm in length, and UMUT PM 27828, ap- proximately 31 mm in length, have been examined. Acknowledgments I gratefully acknowledge my debt to the late Teiichi Kobayashi, for his helpful comments on the Ordovician stratigraphy and fauna of South Korea and encouragement when the author was a graduate student. Thanks also are due to Kan-San Ahn for aid in conducting field work and Tamio Nishida for providing locality information. The help of Takeo Ichikawa in examination of the type speci- mens, deposited in the University Museum of the University of Tokyo, is appreciated. I also thank Cheol- Soo Yun and an anonymous reviewer for their useful com- ments. References Aronoff, S. M., 1979: Orthoconic nautiloid morphology and the case of Treptoceras vs. Orthonybyoceras. Neues Jahrbuch fiir Geologie und Paldontologie, Abhandlungen, vol. 158, p. 100-122. Doguzhaeva, L. A. and Shkolin, A. A., 1999: Sifon “Loxoceras” (Pseudactinoceratidae) iz nizhnego karbona tsentral’noi Rossii: mikrostruktura, taksonomicheskoe znachenie i funktsional’- naya interpretatsiya (Siphuncle of “Loxoceras” (Pseudactino- + Figure 1. Treptoceras yokoyamai (Kobayashi). 1, 3-7, UMUT PM 27827. 1, dorsal view, x 2; 3, dorsoventral thin section, venter on right, x 8; 4, details of apical siphuncle, x 30; 5, details of adoral siphuncle, x 30; 6, details of endosiphuncular deposits, x 50; 7, details of adoral septal neck, x 50. 2. UMUT PM 27828, septal view of adoral end, venter down, silicon rubber replica, x 4. 8. UMUT PM 0687, dorsoventral polished section, venter on right, x 5.5. Abbreviations: cr, connecting ring; ed, endosiphuncular deposits; sn, septal neck. 124 ceratidae) from the Lower Carboniferous of Central Russia: Ultrastructure, Phylogenetic implication and functional mor- phology). p. 271-287. In, Rozanov A. Yu. and Shevyrev A. A. eds., Iskopaemye Tsefalopody: Noveishie Dostizhenii’ v Ikh Izuchenii (Fossil Cephalopods: Recent Advances in their Study), Rossiiskaya Akademiya Nauk Paleontologicheskii Institut, Moscow. (in Russian with English abstract) Flower, R. H., 1942: An arctic cephalopod faunule from the Cynthiana of Kentucky. Bulletins of American Paleontology, vol. 27, p. 1-50, pls. 1-4. Flower, R. H., 1955: New Chazyan orthocones. Journal of Paleontology, vol. 29, p. 806-830, pls. 77-81. Flower, R. H., 1962: Part 2. Notes on the Michelinoceratida. New Mexico Bureau of Mines and Mineral Resources, Memoir 10, part 2, p. 19-42, pls. 1-6. Foerste, A. F., 1921: Notes on Arctic Ordovician and Silurian cephalopods. Denison University Bulletin, Journal of the Scientific Laboratories, vol. 19, p. 247-306, pls. 27-35. Frey, KR. C., 1988: Paleoecology of Treptoceras duseri (Michelinoceratida, Proteoceratidae) from Late Ordovician of southwestern Ohio. New Mexico Bureau of Mines and Mineral Resources, Memoir 44, p. 79-101. Hall, J. and Whitfield, R. P., 1875: Section 1. Descriptions of in- vertebrate fossils, mainly from the Silurian System. Fossils of the Hudson River Groups. (Cincinnati Formations). Geologi- cal Survey of Ohio, vol. 2, part 2, p. 65-110, pls. 1-4. Hyatt, A., 1883-1884: Genera of fossil cephalopods. Proceedings of the Boston Society of Natural History, vol. 22, p. 253-272 [1883], 273-338 [1884]. Kobayashi, T., 1927: Ordovician fossils from Corea and South Manchuria. Japanese Journal of Geology and Geography, vol. 5, p. 173-212, pls. 18-22. Kobayashi, T., 1934: The Cambro-Ordovician formations and fau- nas of South Chosen. Palaeontology. Part 1. Middle Ordovician faunas. Journal of the Faculty of Science, Imperial University of Tokyo, Section 2, vol. 3, p. 329-519, pls. 1-44. Kobayashi, T., 1966: The Cambro-Ordovician formations and fau- nas of South Korea. Part 10. Stratigraphy of the Chosen Shuji Niko Group in Korea and South Manchuria and its relation to the Cambro-Ordovician formations of other areas. Section A. The Chosen Group of South Korea. Journal of the Faculty of Science, University of Tokyo, Section 2, vol. 16, p. 1-84. Lee, H. Y., 1977: Conodonten aus den Jigunsan- und den Duwibong-Schichten (Mittelordovizium) von Kangweon-Do, Siidkorea. The Journal of the Geological Society of Korea, vol. 13, p. 121-150. Lee, H. Y., 1980: Lower Palaeozoic conodonts in South Korea. Jn, Kobayashi, T. et al. eds., Geology and Paleontology of Southeast Asia, vol. 21, p. 1-9, pls. 1,2. University of Tokyo Press, Tokyo. M’Coy, F., 1844: A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland, 274 p. Privately published. (re- issued by Williams and Norgate, London, 1862) Niko, S., 1998: Kobayashiceras gifuense, a new actinocerid cepha- lopod from the Lower Devonian of Japan. Journal of Paleontology, vol. 72, p. 36-38. Ruedemann, R., 1906: Cephalopoda of the Beekmantown and Chazy Formations of the Champlain Basin. New York State Museum, Bulletin 90, p. 393-611. Stokes, C., 1840: On some species of Orthocerata. Transactions of the Geological Society of London, Ser. 2, vol. 5, p. 705-714, pls. 59, 60. Sweet, W. C., 1964: Nautiloidea-Orthocerida. p. K216-K261. In, Moore, R. C. ed., Treatise on Invertebrate Paleontology. The Geological Society of America, New York and the University of Kansas Press, Lawrence, Kansas. Teichert, C., 1933: Der Bau der actinoceroiden Cephalopoden. Palaeontographica, Abteilung A, vol. 78, p. 111-230, pls. 8- 15. Yamanari, F., 1926: Scale structure in Kogendo. Geographical Review of Japan, vol. 2, p. 572-590. (in Japanese) Yun, C. S., 1999: Ordovician cephalopods from the Maggol Forma- tion of Korea, Paleontological Research, vol. 3, p. 202-221. Zittel, K. A. von, 1900: Text-book of Paleontology (translated and edited by Eastman, C. 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However, figures will be returned upon request by the authors after the paper has been pub- lished. Ager, D. V., 1963: Principles of Paleoecology, 371p. McGraw- Hill Co., New York. Barron, J. A., 1983: Latest Oligocene through early Middle Miocene diatom biostratigraphy of the eastern tropical Pacific. Marine Micropaleontology, vol. 7, p. 487-515. Barron, J. A., 1989: Lower Miocene to Quaternary diatom biostratigraphy of Leg 57, off northeastern Japan, Deep Sea Drilling Project. In, Scientific Party, Initial Reports of the Deep Sea Drilling Project, vols. 56 and 57, p. 641-685. U. S. Govt. Printing Office, Washington, D. C. Burckle, L. H., 1978: Marine diatoms. /n, Haq, B. U. and Boersma, A. eds., Introduction to Marine Micropaleon- tology, p. 245-266. Elsevier, New York. Fenner, J. and Mikkelsen, N., 1990: Eocene-Oligocene diatoms in the westem Indian Ocean: Taxonomy, stratigraphy, and paleoecology. /n, Duncan, R. A., Backman, J., Peterson, L. C., et al, eds.Proceedings of the Ocean Drilling Program, Scientific Results, vol. 115, p. 433-463. College Station, TX (Ocean Drilling Program). Kuramoto, S., 1996: Geophysical investigation for methane hy- drates and the significance of BSR. Journal of the Geological Society of Japan, vol. 11, p. 951-958. (in Japanese with English abstract) Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey (A new find of an ammonoid jaw ap- paratus). Paleontologicheskii Zhurnal 1974, p. 127-129. (in Russian) es se FT BR Jo ann nn nn en nn nn ne 2 ©2002 FF - &2142002F 6 H21H (4), 22H (+), 23H (A) O3 HELP RO EFT RER ‘ee (SAB ih) CRANES. 6A2IA (4) zer 7 À 2% 24 TRAME EU 2 BEZERFEABSSH —FARBFERDELT—: tA, FEHLERN ABS NEE] SEEaNnEF+ Ek, GALMBARYY RDS ARE TRHEL Ed. -REROH LATE 2002E5A7H (A) TY. &&152E]Pl&142003°E 1 A25H (+), 26H (A) SER AFAB ABBE THE DO PE CT. OFFICE SET, ERDKOPRISRÉEREREÉ PT Ai SARE SHE LA 22 0 LK. OHEMFTL, !)MHTEMSNZI-IY sy 73 - 2 -RZZERELTEBOET. FSH ZRZSTEDETITZEDTLEEIOT, SHEBHEOAITHHYO ECKHHVGHOUR FAY. ABI: YY RYO LROMLAALE BABROHLASUTENME Pack CHRSAOR SY. E-mail P77» 7 ATOM LIAS (dH ELTZUINGTEHEEA. EXATHAMICMT SEH ADL STHROTHARSE CHAE < Ta. T305-8571 2 Ih AER 1-1-1 RASS GEMFEITEM) EN PUBS Tel: 0298-53-4302 (IH14) Fax: 0298-51-9764 E-mail: ogasawar @ arsia.geo.tsukuba.ac.jp ALL I AT SHR ERS?) 7305-8571 >< IX ER 1-1-1 TRA SHEESH Tel: 0298-53-4212 (2%) or 53-4465 (S25R35) Fax: 0298-51-9764 E-mail: isaomoto @ sakura.cc.tsukuba.ac.jp OO ed SE ELE LOL ET ET cities tits cit et tit LLL LLL LLL LLL ELL LLL LLL LL LEE ELL LL OLE RT ET ET TE = III ILL EEE EN ER ENTE UF ENT PN PN PN AP" ABORGICES ZB, ZEOSEUAL, ÉJSEDOOLÉNMTENTUEST. HEOBY ZAUTLOBEHTY. PAI Fao WEE ACTIN IAA ee M A mh bl Æ RK et Ie BARR BARAH À © AMRRA Ge KERTACEHBROBHME $2-Y7LN-IRHBAAS HE (7 1 7 LANE) ef a a os Em = 4 20024F4H 25H FE] fil 7113-8622 Hse Cy AHMIAS-16-9 20024444 28H # fr Ba ee er an NN Dim Baw feet M 4 — hk - MEERE Hi fe oe Se RE EK ee AGE N all À O9 FRE BE 2,500 T176-012 Brae BK S Edt201301 a ath 03-3991 es ISSN 1342-8144 Paleontological Research B64, #15 wii ISSN 1342-8144 Paleontological Research Vol. 6, No. 1 April 30, 2002 CONTENTS ARTICLES Gengo Tanaka, Koji Seto, Takao Mukuda and Yusuke Nakano: Middle Miocene ostracods from the Fujina Formation, Shimane Prefecture, Southwest Japan and their paleoenvironmental signifi- Rodolfo Dino and Geoffrey Playford: Stratigraphic and palaeoenvironmental significance of a Pennsylvanian (Upper Carboniferous) palynoflora from the Piaui Formation, Parnaiba Basin, northeastern Brazil == +++: -ur ores eet ntee us ee. ee ee Dhurjati Prasad Sengupta: Indian metoposaurid amphibians revised :-:-::::::::-:::-::::::....:..:. Keiji Nakazawa: Permian bivalves from the H. S. Lee Formation, Malaysia *::::-::::-:::-:::.:.... Yutaro Suzuki: Systematic position and palaeoecology of a cavity-dwelling trilobite, /tyophorus undulatus Warburg, 1925, from the Upper Ordovician Boda Limestone, Sweden :::::::::::::::-:: Moriaki Yasuhara, Toshiaki Irizuki, Shusaku Yoshikawa and Futoshi Nanayama: Changes in Holocene ostracode faunas and depositional environments in the Kitan Strait, southwestern Norihiko Sakakura: Taphonomy of the bivalve assemblages in the upper part of the Paleogene Ashiya Group, southwestern Japan chs, i as MeW ucla auuellee. = \e\ls 6 0 = ne ee elle el ets eos a see sale sen pUs ele le se ce! ie) (vier ellen ee SHORT NOTES Shuji Niko: Revision of an Ordovician cephalopod Ormoceras yokoyamai (Kobayashi, 1927) ::::-:::: | | zu | | TITUTION LIBRARIES i | leontological re Research Y Vol. 6 No. 2 June 2002 _ The Palaeontological Society offfgpan Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Alan G. Beu (Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato (Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto University, Kyoto, Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain), Roger D. K. Thomas (Franklin and Marshall College, Lancaster, USA), Katsumi Ueno (Fukuoka University, Fukuoka, Japan), Wang Hongzhen (China University of Geosciences, Beijing, China), Yang Seong Young (Kyungpook National University, Taegu, Korea) Officers for 2001-2002 Honorary President: Tatsuro Matsumoto President: Hiromichi Hirano Councillors: Shuko Adachi, Kazutaka Amano, Yoshio Ando, Masatoshi Goto, Hiromichi Hirano, Yasuo Kondo, Noriyuki Ikeya, Tomoki Kase, Hiroshi Kitazato, Itaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Kei Mori, Hirotsugu Nishi, Hiroshi Noda, Kenshiro Ogasawara, Tatsuo Oji, Hisatake Okada, Tomowo Ozawa, Takeshi Setoguchi, Kazushige Tanabe, Yukimitsu Tomida, Kazuhiko Uemura, Akira Yao Members of Standing Committee: Makoto Manabe (General Affairs), Tatsuo Oji (Liaison Officer), Shuko Adachi (Finance), Kazushige Tanabe (Editor in Chief, PR), Tomoki Kase (Co-Editor, PR), Kenshiro Ogasawara (Planning), Yoshio Ando (Membership), Hiroshi Kitazato (Foreign Affairs), Haruyoshi Maeda (Publicity Officer), Ryuichi Majima (Editor, “Fossils”), Yukimitsu Tomida (Editor in Chief, Special Papers), Tamiko Ohana (Representative, Friends of Fossils). Secretaries: Fumihisa Kawabe, Naoki Kchno, Shin’ichi Sato, Masanori Shimamoto (General Affairs), Isao Motoyama (Planning), Hajime Naruse (Publicity officer) Kazuyoshi Endo, Yasunari Shigeta, Takenori Sasaki (Editors of PR), Hajime Taru (Editor of “Fossils”), Yoshihiro Tanimura (Editor of Special Papers) Auditor: Yukio Yanagisawa Notice about photocopying: In order to photocopy any work from this publication, you or your organization must obtain permission from the following organization which has been delegated for copyright for clearance by the copyright owner of this publication. Except in the USA, Japan Academic Association for Copyright Clearance (JAACC), Nogizaka Bild., 6541 Akasaka 9-chome, Minato-ku, Tokyo 107-0052, Japan. Phone: 81-3-3475-5618, Fax: 81-3-3475-5619, E-mail: kammori@msh.biglobe.ne.jp In the USA, Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. Phone: (978)750- 8400, Fax: (978)750-4744, www.copyright.com Cover: Typical Pleistocene fossils from the Japanese Islands. Front cover: Sinomegaceros yabei (Shikama). Back cover: Paliurus nipponicum Miki, Mizuhopecten tokyoensis (Tokunaga), Neodenticula seminae (Simonsen and Kanaya) Akiba and Yanagisawa and Emiliania huxleyi (Lohmann) Hay and Mohler. All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16-9, Bunkyo-ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp/palaeont/ Paleontological Research, vol. 6, no. 2, pp. 127-145, June 28, 2002 © by the Palaeontological Society of Japan Molluscan fauna of the ‘‘Miocene” Maéjima Formation in Maéjima Island, Okayama Prefecture, southwest Japan TAKASHI MATSUBARA Division of Natural History, Museum of Nature and Human Activities, Hyogo, 6 Yayoigaoka, Sanda 669-1546, Japan (e-mail: matsu@nat-museum.sanda.hyogo.jp) Received August 2, 2001; Revised manuscript accepted January 15, 2002 Abstract. Molluscan fauna of the “Miocene” Maéjima Formation is examined from taxonomical, biostratigraphical and paleozoogeographical points of view. It is composed of four gastropods and 14 bivalves including a new species. Two assemblages, the Jsognomon and the Megangulus-Acila assemblage, were dis- criminated. The Jsognomon assemblage is autochthonous or para-autochthonous and is composed of ele- ments inhabited the littoral to upper sublittoral gravelly to rocky bottom in a warm sea. The Megangulus- Acila assemblage represents a mixed composition between muddy sand and gravelly to rocky bottom elements, and was formed in an upper sublittoral muddy bottom near a rocky shore. Occurrences of Megangulus maximus (Nagao), Isognomon (Hippochaeta) hataii Noda and Furuichi and Chlamys (Leochlamys) namigataensis (Ozaki) indicate the age of the Maéjima Formation as the Paleogene, not the Miocene. The molluscan fauna of the Paleogene Maéjima Formation contains both Tethyan Indo-Pacific elements and Northern Pacific elements. Taxonomy of selected molluscan taxa including a new arcid, Arca (Arca) uedai sp. noy., is described or discussed. Key words: Arca (Arca) uedai sp. nov., First Setouchi Series, Maéjima Formation, molluscan fauna, Paleogene Introduction The First Setouchi (or Setouti) Series (Kasama and Huzita, 1957) is the generic name for the Miocene strata scattered in the median zone of southwestern Japan (or the Setouchi Geologic Province; Ikebe, 1957), and all of its constituent formations had been regarded as uppermost lower to lower middle Miocene mainly on the basis of the lithology, sedimentary cycle and molluscs (e.g. Huzita, 1962; Itoigawa and Shibata, 1973, 1986, 1992; Ishida, 1979). It has been known that the “Miocene” molluscan assemblages in the coastal area of the eastern Seto Inland Sea (= Setouchi-Engan Belt; Yano et al., 1995a) are differ- ent from those in the neighboring backbone area (= Bihoku Belt; Yano er al., 1995a), both in the western Setouchi Geologic Province (e.g. Huzita, 1962; Itoigawa, 1969, 1971, 1983; Ueda, 1991; Yano er al., 1995a). There are two current interpretations explaining this difference; some paleontologists have postulated the existences of different water masses in the two areas in the late early to early mid- dle Miocene (e.g. Itoigawa, 1983), while others have as- sumed a paleogeographic barrier between the two areas in the late early to early middle Miocene except during times of maximum transgression (e.g. Ueda, 1991; Takayasu et al., 1992; Yano et al., 1995a). On the other hand, it is becoming clear that constituent formations of the First Setouchi Series around the eastern part of the Seto Inland Sea are of Eocene to Oligocene, not Miocene age, as a result of studies during the last fifteen years (Matsuo, 1987; Ozaki and Matsuura, 1988; Suzuki et al., 1995; Ozaki et al., 1996; Yamamoto er al., 2000b; Kurita et al., 2000, 2001). Yamamoto et al. (2000b) found latest middle to late Eocene calcareous nannofossils and dinoflagellate cysts from the “Miocene” Iwaya Formation of the Kobe Group in Awajishima Island, and considered that the difference between the “Miocene” molluscan as- semblages in the coastal area of the eastern Seto Inland Sea and those from the backbone area in the western Setouchi Geologic Province is due to chronologic difference. However, their opinion conflicts with the previous molluscan data because the Miocene species have often been listed from the First Setouchi Series in the eastern part of the Seto Inland Sea (Huzita, 1962; Saito, 1962; Saito et al., 1970; Bando and Furuichi, 1978; Itoigawa, 1983; Huzita and Maeda, 1984; Mizuno ef al., 1990; Okumura and Sato, 1999). However, most of these studies are unac- companied by either figures or descriptions of molluscan taxa. Thus, it is necessary to reinvestigate the molluscan 128 Takashi Matsubara Figure 1. Location and geologic maps of the study area. (hatched area; modified from Shibata and Itoigawa, 1980). et al. (2000). of Maéjima Island, Okayama Prefecture. fauna of the area, especially from the taxonomical point of view. The Maéjima Formation is the Tertiary in the western part of Maéjima Island, Ushimado Town, Oku County, southeastern Okayama Prefecture (Figure 1A, B), and has been regarded as one of the constituents of the Miocene First Setouchi Series (e.g. Itoigawa, 1969, 1983; Itoigawa and Shibata, 1986). The distribution of the Tertiary in this island was for the first time reported by Sato (1938), and the stratigraphy was established recently by Yamamoto (2001). Although molluscan assemblages resembling those from other “Miocene” formations in the coastal areas in the eastern part of the Seto Inland Sea have been re- ported by Itoigawa (1969, 1971, 1983) and Yamamoto (2001) provisionally, precise constituents and faunal char- acteristics still remain unclear. In this paper, I taxonomi- cally review the molluscan fauna of the “Miocene” Maéji- ma Formation and discuss the geologic age and its paleogeographical and paleozoogeographical implications. Geological setting The Maéjima Formation (Itoigawa and Shibata, 1986, as Maeshima Formation; revised by Yamamoto, 2001) is dis- tributed in the southwestern part of Maéjima Island, unconformably overlying the pre-Tertiary plutonic rocks (Figures 1B, 2). Although Yamamoto (2001) subdivided the Maéjima Formation into the Lower Conglomerate and Sandstone and the Upper Sandstone Member, they are Pt. Shirogahana o iS) = > © -_ Ay a D iS) 3 © = oO n A. Location of study area (arrow) and distribution of the “Miocene” sediments The geologic province division follows Yano et al. (1995a) partly modified after Seto AW: Awajishima Island, MJ: Maéjima Island, SH: Shodoshima Island, TS: Teshima Island. B. Geologic map of the western part treated herein as the lower and the upper part with a revi- sion of the boundary (Figure 2A). The lower part of the Maéjima Formation is less than 10 m in thickness and is composed mainly of granule to pebble conglomerate with numerous fragments of balanids, brachiopods, calcareous algae and molluscs. This part is well exposed on the southwestern coast of Maéjima Island, which is designated to be the type locality of the formation. The upper part (30 m+) consists mainly of siltstone to muddy very fine-grained sandstone and is associated with calcareous medium- to coarse-grained sandstone. The upper part abuts on the basement and is conformably un- derlain by the lower part. Outcrop of the upper part is little exposed because it is distributed only in the hilly area with a low relief. The age of the Maéjima Formation is not known pre- cisely, which indicates an age of Yamamoto et al. (2000a) preliminarily reported a Sr isotope value of about 0.7077, which indicates an age of late Eocene or older. Material Molluscan samples were collected from eight localities; five from the lower part and three from the upper part (Figure 2A, B). The preservation of fossil molluscs is quite poor and shell material of most specimens examined was dissolved away except for pectinids and an ostreid. Thus, hydrophilic vinyl polysiloixane impression materials (PROVIL novo, Putty®, regular set, Heraeus Kulzer, Inc., Mollusca from “Miocene” Maéjima Formation 129 Maéjima Formation upper part lower part Basement sist. - f. sst. md. sst. CS. -V. CS. Sst. Figure 2. Maéjima Formation. f) were made and fossil localities. Mapped area same as Figure 1B. Ltd. and EXAFINE® Putty Type, GC Co., Ltd.) were used for the examination of molds. Molluscan fauna Four species of Gastropoda and 14 species of Bivalvia including a new species were discriminated as a result of the examination (Table 1). On the basis of the dominant and associated species, the following two assemblages are discriminated (Figure 3). A. Isognomon assemblage This assemblage is characterized by an abundant occur- rence of /sognomon (Hippochaeta) hataii Noda and Furuichi, and is generally associated with a few specimens gr.-pb. cg. Columnar sections of the Maéjima Formation and locations of measured points and fossil localities. Abbreviations. slst.: siltstone; sst.: sandstone (f.: fine-grained; m.: medium-grained; cs.: coarse-grained; v.cs.: very coarse- grained); cg.: conglomerate (gr.: granule; pb.: pebble; cb.: cobble; bld.: boulder). cb.-bld. cg. granite sample horizon A. Columnar sections of the B. Map showing the points where the geologic columns (a through of Septifer (Mytilisepta) sp. The /sognomon assemblage occurred from conglomerate to conglomeratic sandstone in the lower part of the Maéjima Formation (Locs. MJ-1, 2a, 2b, 2c and 3). At Loc. 3, /. (H.) hataii occurs abundantly in the matrix of boulder conglomerate without any associ- ated species, and most of the specimens are articulated. At other localities, although most specimens of this species are disarticulated, they are less broken and a few articulated valves are included. Consequently, this assemblage is re- garded to be autochthonous or para-autochthonous in broad sense. Taking the lithology of rocks in which the assem- blage occurs and the habitat of the Recent homologues of these two species into account (Higo er al., 1999), this as- semblage inhabited littoral to upper sublittoral, gravelly to rocky bottom of an open sea. 130 Takashi Matsubara Table 1 . List of fossil Mollusca from the “Miocene” Maéjima Formation. Horizon Lower part Upper part Species name/Locality MJ-1 MJ-2a MJ-2b MIJ-2c MJ-3 MJ-4 MJ-5 MJ-6 Gastropoda Patellogastropoda, fam., gen. et sp. indet. Calyptraea sp. Naticidae? gen. et sp. indet. Muricidae? gen. et sp. indet. Bivalvia Acila (Truncacila) cf. nagaoi Oyama and Mizuno Arca (Arca) uedai sp. nov. Glycymeris (glycymeris) sp. Septifer (Mytilisepta) sp. 1 Isognomon (Hippochaeta) hataii Noda and Furuichi 6 Delectopecten sp. Chlamys (leochlamys) namigataensis (Ozaki) Crassastrea sp. Luchinidae gen. et sp. indet. Cyclocardin sp. Glans sp. Megangulus maximus (Nagano) Mactra? sp. Tapes? sp. (es) NW © D TOTAL 7 Assemblage Isognomon Megangulus-Acila en M EE CE EN [wee Pe | wos ETES Se Isognomon (Hippochaeta) hataii Noda and Furuichi Septifer (Mytilisepta) sp. Chlamys (Leochlamys) namigataensis (Ozaki) Megangulus maximus (Nagao) Acila (Truncacila) cf.nagaoi Oyama and Mizuno Cyclocardia sp. Mactra? sp. Arca (Arca) uedai Matsubara sp. nov. Figure 3. The Ostrea-Balanus assemblage of Itoigawa (1969) probably corresponds to the /sognomon assemblage. But only a single specimen of Crassostrea sp. was collected from Loc. MJ-2c among all the localities examined in the present study. Consequently, the occurrence of the Ostrea-Balanus Assemblage from the Maéjima Formation is not supported. B. Megangulus-Acila assemblage The Megangulus-Acila assemblage occurred from siltstone to medium-grained sandstone in the upper part of Molluscan assemblages of the Maéjima Formation. Number in legend indicates that of individuals. the Maéjima Formation (Locs. MJ-4, 5 and 6). This as- semblage is characterized by infaunal Bivalvia species, Megangulus maximus (Nagao) and Acila (Truncacila) cf. nagaoi Oyama and Mizuno. Most shells of these species are disarticulated and are arranging parallel to the bedding plane. However, a few articulated specimens of M. maximus, A. (T.) cf. nagaoi, Cyclocardia sp. and Mactra ? sp. are recognized. This fact indicates that most shells of these species have not been transported a great distance from their original habitat. These species are regarded as shallow burrowers in an upper sublittoral, muddy to sandy Mollusca from “Miocene” Maéjima Formation 131 bottom (Higo et al., 1999). On the other hand, Arca (Arca) uedai sp. nov., Septifer (Mytilisepta) sp. and Isognomon (Hippochaeta) hataii are considered to be epibyssate benthos on a gravelly to rocky bottom. There are no articulated specimens among these species, and thus they are considered to have been transported from their original habitat. These facts suggest that this assemblage represents a mixed composition formed in an upper sublittoral, muddy to muddy sand bottom neighboring a rocky shore in an open sea. The occurrences of muddy to sandy bottom elements such as Acila (Truncacila), Mactra? and Cyclocardia indi- cate that this assemblage is compared with the Mactra- Acila assemblage of Itoigawa (1983) characterizing the molluscan assemblages in the coastal area of the eastern Seto Inland Sea. Discussion Geologic age Among the constituents of the molluscan fauna of the Maéjima Formation, Megangulus maximus (Nagao), Isognomon (Hippochaeta) hataii Noda and Furuichi, and Chlamys (Leochlamys) namigataensis (Ozaki) are impor- tant for the age estimation (Figure 4). The first species has been recorded from the Paleogene of Kyushu and the other two species are known from the “Miocene” of southwest Honshu around the eastern part of the Seto Inland Sea. M. maximus occurs from the Funazuan to the Nishisonogian Stages (Mizuno, 1962) of southwest Japan (e.g. Nagao, 1928b; Oyama er al., 1960; Mizuno, 1964; Okamoto and Imamura, 1964; Okamoto, 1970; Shuto and Shiraishi, 1971; Kamada, 1980; Fuse and Kotaka, 1986; Shuto, 1991). Although the precise age of the stratotype of the Funazuan Stage, the Funazu Sandstone Member of the lojima Formation in the Takashima Coalfield, west Kyushu, is unknown, a calcareous nannofossil biostrati- graphy of the correlate Matsushima Group in the Sakito- Matsushima Coalfield (SK-MT in Figure 4) was studied by Okada (1992). Okada (1992) assigned this group to the Subzone CP 15b to CP 16a of Okada and Bukry (1980). In addition, Okada (1992) also correlated the Oniike Formation of the Sakasegawa Group in the Amakusa Coalfield (AM in Figure 4) and the Yotsuyama Formation of the Manda Group in the Miike Coalfield (MK in Figure 4), both of which are referred to the Okinoshiman Stage below the Funazuan Stage (Mizuno, 1964), to CP 14b to CP15b. These calcareous nannofossil biostratigraphic data suggest that the lower limit of the Funazuan Stage is in CP15b. According to Berggren et al. (1995), this calcare- ous nannofossil zone ranges from 36.0 to 34.3 Ma or the late Eocene. Okada (1992) also studied the age of the Nishisonogi Group in the Sakito-Matsushima Coalfield (SK-MT in Figure 4), the stratotype of the Nishisonogian Stage by means of calcareous nannofossil biostratigraphy, and assigned the age of the upper part of the Nishisonogi Group to sometime during CP17 to CP19 on the basis of the occurrence of Dictyococcites bisectus. According to Berggren et al. (1995), the last occurrence of this species (cited as Reticulofenestra bisecta in Berggren et al., 1995) is 23.9 Ma or the latest Oligocene. Concerning the Ashiya Group in the Chikuho Coalfield (CH in Figure 4), one of the correlatives of the Nishisonogian Stage, biostratigraphic studies were carried out by Saito and Okada (1984), Tsuchi et al. (1987), Okada (1992) and Ibaraki (1994). According to them, the age of the Ashiya Group is the late early to early late Oligocene. Further, the Taoyama Formation of the Hioki Group in the Yuyawan area (YY in Figure 4), an- other correlative of the Nishisonogian Stage, contains D. bisectus (Fuse and Kotaka, 1986). Ozaki (1999) also re- ported fission-track ages of 25.2 + 1.7 Ma and 23.1 + 1.6 Ma (error: 16) from the Hitomaru Formation which over- lies the Taoyama Formation in the Yuyawan area. Taking these data into account, the range of M. maximus is re- garded as late Eocene to Oligocene (Figure 4). I. (H.) hataii is a species originally described from the “Miocene” Teshima Formation of the Tonosho Group in Teshima Island, northern Kagawa Prefecture (SH-TS in Figure 4; Noda and Furuichi, 1972). Bando and Furuichi (1978) correlated this formation to the Shikai Formation of the Tonosho Group in Shodoshima Island, situated several kilometers east of Teshima Island. This correlation is strongly supported by the occurrence of an endemic bi- valve, Tapes nagahamaensis Saito, Bando and Noda, 1970, recorded only from the Teshima and Shikai Formations. Saito et al. (1970), Noda and Furuichi (1972), Bando and Furuichi (1978), Itoigawa and Shibata (1992) and Okumura and Sato (1999) all regarded the Tonosho Group distributed in Shodoshima and Teshima Islands as of early middle Miocene age. However, Kurita er al. (2000) reported the Eocene dinoflagellate cysts from the Shikai Formation. Consequently, the age of the Teshima Formation, which contains /. (H.) hataii, is also considered to be Eocene (Figure 4). C. (L.) namigataensis was originally described from the “Miocene” Namigata Formation in Ibara City, Okayama Prefecture (NM in Figure 4; Ozaki, 1956). The age of the Namigata Formation has been considered to be the lowest middle Miocene (e.g. Shibata and Itoigawa, 1980; Itoigawa, 1983; Yano er al., 1995a, b). Yano et al. (1995b) discriminated four benthic foraminiferal assem- blages characterized by such species as Elphidiella momiyamaensis Uchio, Pseudononion japonicum Asano, Hanzawaia tagaensis Asano and Cibicidoides pseudoun- gerianus (Cushman) from the Namigata Formation. They pointed out that these assemblages are comparable with Takashi Matsubara 132 ‘dnoip euniysounys “IN Ug ‘dnoig) T3ouosiysiN :IH’SN :dnoIg eunysnsiey IDI ‘(6661 'DIEZO ‘9861 'eIEIOY pue 95m) vore uemeAng :XA ‘(Z66I ‘ePEXO) PI2!JfeoI ewrysnsjep-ongeg : LN-NS ‘(0007 ‘72 12 EM) vere ewiysa]-eungsopiyg :SL-HS !LL6I ‘EMEBIOJ] pue OJOUIUSIN) vore EJESILUEN : WN (2661 ‘EPEXO) PIOILOD OAM “MIN ‘(HOOT ‘DIE ‘Z661 “EPEXO ‘1661 ‘TeYeS pue IyoeÄlW ‘0661 ‘72 12 reyes) play[eoD nsiesey UM “(L861 ‘PINZNS pue eMeSISeuEX :986] ‘EPIWOL) PISHIEOD uegor :gf ‘(66T “Diereg] ‘Z661 ‘EPEXO ‘L861 “ID 12 ıyons], ‘9861 ‘EPEXO pur OS) pjalyJeo) OYNATYD HO “(40007 “72 12 oowreue x) var eunysıfemy : MV :(Z661 ‘EPEXO) PIPHIEOD esnyewmy AV 'eloflurueiog oTUOIYURTY : "Id “SIISSOJouueu snoa1eo[e) :N AUS00IN “ONIN ‘Aiejod oneuseyy “WW ‘Alles :'e ‘(+961 ‘Z961) Ounzi (S (0861) Aning pue epexO (+ (6961) MoJd (€ :(S661) Ip 12 ua1sdıag pue (C661) 1uay pur pur) (7 ‘(S661) 72 12 U21S8 1 (| 2I89S au] 1x2) OY} ur passnosıp sofoads ueosnjjoun Jo adueı 9130J0u01y> pue uedef ur eyes ausZoajeg pa10ajas OY) JO UONE[OLOD) ‘p aundıy = D Fis pouozun N] am N 1 ERS) H N m0Q =S waimyny a = | ewedmnys! | | wewumyseye]L Ss IYSIOL = 1 === epoyoy] = Bocas, Sp 38: i | Sv "I = | 1 I 1 es) Se | | | à ERIC | | | (®) NE ii IS = | 14 I | ap a Q I: | u | 3 ee rs: | 1 | = E = cs = 5 5 d I » = à =O noin H N 1 3 € Z Ob Op 37:8 l | | | 5 o| | wewrysourgo eZee ! = à A popes | 3 5 ex aS «5 I 1 1 1 a = I 1 | I AS I 1 I ES zl ı | | == œ| 1 I 1 | ac #9 SSS ae a] ı to ! au DER | Hi ehem] Jo] | i Ù 1 uO = > 1 ES tl ont dl | | Sap SS BEA | | ı 1 1 | GA RER | operen |: SE cis} | Gl nv | i | SO Of | 15 En a I | eeätwen | ewrysry eumysnspep |" ss = | 1edesy Is SL-HS | 1 eınoue)[ =“ 9 [emomgex] D u Q ® 3 ! I = [feo = s = Q È eyjesesiyg 1 1 nstesey © A IW-AS 2 el À cee: = | Log OC Dei À al = = 1 aE ET [ome] | 1% } Di À: I I A = 05 HO © = : [2 | Cr] Ss en 1 = da | ! opemry tH = 8 ! l pol C3 © 1 1 © = | ! B: ogases CZ CC = l H ewefory | © = I 1 = I 1 5 = ----j---- WN nıewoJH UBOgSSeS NVAVI MS dO "N dd “OW Moses ey eN @ovisnvosntion „N ( @ (1/#90a3 Mollusca from “Miocene” Maéjima Formation 133 those of the Miogypsina kotoi-Operculina complanata Assemblage Zone of Nomura (1992), being assigned to the latest early to early Middle Miocene. However, E. momiyamaensis, H. tagaensis and C. pseudoungerianus were also reported from the Iwaya Formation of the Kobe Group by Tai (1959), from which Yamamoto er al. (2000b) reported Eocene calcareous nannofossils and dinoflagellate cysts. In addition, the benthic foraminiferal assemblages from the Namigata Formation do not include Ammonia tochigiensis (Uchio) which is one of the representative spe- cies in the Miocene benthic foraminiferal zone (Yano et al., 1995b). Consequently, the benthic foraminiferal data do not indicate a Miocene age for the Namigata Formation. On the other hand, Nishimoto and Itoigawa (1977) pre- liminarily reported Carcharodon angustidens (Agassiz) from the Namigata Formation in addition to the upper lower Oligocene Yamaga Formation of the Ashiya Group and the upper Oligocene Taoyama Formation of the Hioki Group. This fossil shark has very characteristic teeth with distinct anterior and posterior cusps. Yabumoto and Uyeno (1994) indicated that in Japan C. angustidens has been restrictedly found from the middle Eocene to the upper Oligocene of southwest Japan. Consequently, the age of the Namigata Formation is regarded to be somewhere during the middle Eocene to the late Oligocene, not the Miocene (Figure 4). Although C. (L.) namigataensis was also recorded from the middle Miocene Kawazu Formation in Shimane Prefecture by Masuda (1962), his figured specimen (Masuda, 1962, pl. 21, fig. 1) is not referred to Pecten (Chlamys) namigataensis Ozaki, 1956 (see systematic pale- ontology to be discussed below). Recently, C. (L.) namigataensis was for the first time found from the Paleogene Iwaki Formation of the Shiramizu Group in the Joban Coalfield (JB in Figure 4), northeast Honshu, Japan. Nemoto and O’Hara (2001) figured a right valve of Chlamys ashiyaensis (Nagao) from this formation, but their figured specimen is, in my opinion, C. (L.) namigataensis (see systematic paleontology). The age of the Iwaki Formation of the Shiramizu Group is considered to be the late Eocene or the early Oligocene on the basis of the oc- currence of Entelodon cf. orientalis Dashzeveg (Tomida, 1986) and the planktonic microfossils age of the Shirasaka Formation (early Oligocene; Yanagisawa and Suzuki, 1987), the uppermost constituents of the Shiramizu Group. Taking these facts into account, the geologic age of the Maéjima Formation is judged to be Paleogene, somewhere between the middle Eocene and late Oligocene. Implications of the molluscan fauna of Maéjima For- mation Itoigawa (1983) grouped the “Miocene” molluscan as- semblages from the First Setouchi Series in the coastal area of the eastern part of the Seto Inland Sea, including the Maéjima Formation, into four types, the Cyclina-Barbatia, the “Ostrea”, the Mactra-Acila and the Cyclocardia- Nuculana assemblages. Constituents of these assemblages were considered to have inhabit the intertidal to uppermost sublittoral sandy mudbottom, uppermost to upper sublittoral rocky bottom, upper sublittoral sandy bottom, and upper sublittoral muddy bottom, respectively (Itoigawa, 1983). An assemblage comparable in generic composition to the Mactra-Acila assemblage was also rec- ognized in the Maéjima Formation, namely, the Megan- gulus-Acila assemblage. Recent studies on planktonic microfossils (Kurita er al., 2000, 2001; Yamamoto et al., 2000b) indicate that some of the formations yielding these assemblages are of Eocene age, which concords with the results of the present study for age assignment. It has been known that the four assemblages of Itoigawa (1983) have little similarity in not only specific but also ge- neric compositions to the Miocene molluscan assemblages from the neighboring backbone area (e.g. Huzita, 1962; Itoigawa, 1969, 1971, 1983; Ueda, 1991; Yano et al. 1995a). The latter assemblages are represented by the embaymental arcid-potamid [potamidid] fauna of Tsuda (1965). Yamamoto er al. (2000b) preliminarily considered that the difference between the assemblages from the coastal area of the Seto Inland Sea and those from the back- bone area is chronological taking account of the Eocene planktonic microfossils from the Iwaya Formation of the Kobe Group, while previous researchers explained it by paleoenvironmental or paleogeographic factors in Miocene time (e.g. Itoigawa, 1983; Ueda, 1991; Takayasu et al., 1992; Yano et al., 1995a). The result of the present study supports the view of Yamamoto er al. (2000b), and both in- dicate that the Miocene First Seto Inland Sea (Ikebe, 1957) was not invaded in the coastal area of today’s eastern part of the Seto Inland Sea, and that the “Miocene” shallow ma- rine area in the eastern part of the Seto Inland Sea in the judgment of previous researchers (e.g. Shibata and Itoigawa, 1980; Itoigawa and Shibata, 1992; Takayasu et al., 1992) was in fact of Paleogene age. Consequently, it is necessary to revise the Tertiary paleogeography of southwest Japan on the basis of the precise geochronologic data in near future. It is notable that the molluscan fauna of the Paleogene Maéjima Formation contains both Tethyan Indo-Pacific elements and Northern Pacific elements of Honda (1991, 1994). The former are represented by such genera as Isognomon and Septifer, and the latter by, for example, Cyclocardia and Megangulus (Honda, 1994; Ogasawara, 1996). Honda (1994) revealed the northward migration of the Tethyan Indo-Pacific elements in the middle Eocene and the southward migration of the Northern Pacific ele- 134 Takashi Matsubara ments during the late early Oligocene to early Miocene. However, the precise timing and mode of migration of the molluscan fauna have not fully been clarified because Paleogene shallow marine sediments were accepted to be almost lacking in the area between Kyushu and the Pacific coast of northeast Honshu. Although the precise geologic age of the Maéjima Formation was not determined by the molluscan evidence in the present study, further geochronological studies of the Paleogene shallow marine sediments in the coastal area of the eastern part of the Seto Inland Sea and taxonomical studies of the molluscan fauna will provide a reliable basis for elucidation of the succes- sive changes of the Paleogene molluscan fauna in the Northwest Pacific region. Concluding remarks Until the middle of 1990s, Paleogene marine sediments in southwest Japan had been considered to be restricted mostly to the Southern Shimanto Belt (Taira et al., 1980) in the back arc of the Japanese Islands, except for Kyushu. Honda (1991, 1994) discriminated the North Japan- Western Okhotsk, Central Japan and Taiwan-South Japan Provinces from north to south for the western Pacific Paleogene molluscan faunal provinces. The Central Japan Province, in particular, was proposed on the basis of fragmental molluscan records from the accretionary sedi- ments deposited in the lower sublittoral zone or at greater depths. Consequently, the characteristics of the shallow marine molluscan faunas in this province have been less than clear. The result of the present study strongly sup- ports the age estimation based on planktonic microfossils by Kurita et al. (2000, 2001) and Yamamoto et al. (2000b) that the constituent formations of the “Miocene” First Setouchi Series in the coastal area of the eastern part of the Seto Inland Sea are in fact Paleogene, not Miocene (Kurita et al., 2000, 2001; Yamamoto et al., 2000b). Systematic description of selected taxa All the illustrated specimens are housed at the Museum of Nature and Human Activities, Hyogo (MNHAH). The following institutional abbreviations are also used in this paper: IGPS: Institute of Geology and Paleontology, Tohoku University, Sendai; NSMT: National Science Museum, Tokyo; UMUT: University Museum, the Unversity of Tokyo. Class Bivalvia Subclass Paleotaxodonta Order Nuculoida Superfamily Nuculoidea Family Nuculidae Genus Acila H. & A. Adams, 1858 Subgenus Truncacila Grant and Gale, 1931, ex Schenck MS Acila (Truncacila) sp. cf. A. (T.) nagaoi Oyama and Mizuno, 1958 Figure 5.4 Compare.— Acila nagaoi Mizuno (MS). Mizuno, [nomen nudum] Acila (Truncacila) nagaoi Oyama and Mizuno, 1958, p. 7-8. pl. 1. figs. 14, 15. 1956, pl. 2, fig. 1. Material.—MNHAH reg. no. D1-018895 (from MJ-5). Discussion.—The specimens from the Maéjima Forma- tion are comparable with Acila (Truncacila) nagaoi Oyama and Mizuno, 1958, in having a small, rather longer than high, posteriorly oblique, oval shell with a beak situated at four-fifths of the shell length from the anterior end and a weak posterior ridge. They are not sufficiently well pre- served to allow a precise species assignment. Subclass Pteriomorphia Order Arcoida Superfamily Arcoidea Family Arcidae Subfamily Arcinae Genus Arca Linnaeus, 1758 Subgenus Arca Linnaeus, 1758 Arca (Arca) uedai sp. nov. Figure 5.5, 5.7a-c, 5.12 Type specimens. — MNHAH reg. nos. D1 - 018896 (Holotype); D1-018897 through D1-018903(Paratypes). Type locality.—Loc. MJ-4. A small outcrop exposure on its northern side about 400m south-southeast of Yoshida Shrine, Maéjima Island, Ushimado Town, Oku County, Okayama Prefecture (34° 36° 2” N, 134° 10° 29” E). Diagnosis.—Rather small-sized Arca (Arca) with a low umbonal area, low crescent-shaped ligamental area, narrow hinge plate and shell surface sculptured by fine, low, nu- merous radial ribs. Description.—Shell rather small (less than 40 mm in shell length), transversely elongate quadrate, inequilateral, moderately inflated; hinge line straight, long; beak blunt, prosocline, situated about two-fifths anteriorly of shell length; posterior ridge distinct, shell strongly depressed be- hind it; posteroventral margin obliquely truncated; central part of shell weakly depressed; shell surface sculptured by about 60 fine, low radial ribs; ribs generally with a fine intercalary rib on interspace; growth lines fine, generally Mollusca from “Miocene” Maéjima Formation 135 Table 2. Measurements of Arca (Arca) uedai sp. nov. MNHANreg.no. Length (mm) Height (mm) D1-018896° 34.2 18.8 D1-018897° " 24.57 7° 12370: D1-018898" 35.0+° °° 152777 D1-018899" ' 30.9+ 15.9 “holotype. ""paratype. """deformed weak but rather strengthen on central depressed area; ligamental area low crescentic in shape, smooth except for one or a few, rather deep, chevron-shaped ligamental grooves; adductor muscle scars moderate in size, ovate (type A of Noda, 1966), weakly impressed; pallial line shallow, weakly impressed; inner ventral margin not crenated. Etymology.—The present new species is named in honor of the late Tetsuro Ueda of Niigata University, who con- tributed to the molluscan paleontology of the First Setouchi Series during the middle 1980s to early 1990s. Discussion.—Arca (Arca) uedai sp. nov. closely resem- bles A. (A.) miurensis Noda, 1966, from the Pleistocene Koshiba Formation in Kanagawa Prefecture. However, the present new species possesses a narrower hinge plate and lower ligamental area. A. (A.) sakamizuensis Hatai and Nisiyama, 1952, from the Oligocene Sakamizu Formation of the Ashiya Group in Fukuoka Prefecture, Kyushu, is similar to the present new species in having fine radial ribs. The former is discrimi- nated from the latter by having a more produced umbonal area and a higher ligamental area. A. (A.) washingtoniana Dickerson, 1917, from the Oligocene Gries Ranch Formation of Washington, U.S.A., is another allied species, but is distinguished from Arca (Arca) uedai sp. nov. by having coarser radial ribs on the younger shell and stronger teeth. The Recent A. (A.) boucardi Jousseaume is easily distin- guished by having a larger shell with a stronger posterior ridge, coarser, less numerous radial ribs, and a higher umbonal area. Measurements.—Table 2. Order Mytiloida Superfamily Mytiloidea Family Mytilidae Genus Septifer Récluz, 1848 Subgenus Mytilisepta Habe, 1951 Septifer (Mytilisepta) sp. indet. Figure 5.8, 5.9, 5.14 Material. —MNHAH reg. nos. D1-18905 through D1- 018907 (from MJ-2b), D1-018908 and D1-018909 (from MJ-2c), D1-018910 (from MJ-4), and D1-018911 (from MJ-6). Discussion.— Several poor specimens have been ob- tained. The occurrence of a septum in the subumbonal region and inner ventral margin lacking fine crenations in- dicate this species is referred to the subgenus Mytilisepta Habe, 1951. Septifer (Mytilisepta) sp. from the Maéjima Formation is similar in general shell shape to Septifer (Septifer) nagaoi Oyama, 1951, which was introduced as a new name for Mytilus hirsutus Lamarck of Yokoyama, 1927 from the Oligocene Nishisonogi Group in Nagasaki Prefecture. However, the holotype designated by Oyama (1951) (UMUT reg. no. CM24987) has a very finely crenated inner ventral margin, as Mizuno (1952) described. The present species is easily distinguished from the Recent species, Septifer (Mytilisepta) keenae Nomura, 1936 distributed in southern Hokkaido and southward, in having a larger shell with finer radial ribs and weakly curved anteroventral margin. Order Pterioida Superfamily Pterioidea Family Isognomonidae Genus Isognomon [Lightfoot, 1786] Subgenus Hippochaeta Philippi, 1844 Isognomon (Hippochaeta) hataii Noda and Furuichi, 1972 Figures 5.15-5.17, 6.13, 6.14 Isognomon (Isognomon) hataii Noda and Furuichi, 1972, p. 120, text-fig. 1. Isognomon (Isogonum) hataii Noda and Furuichi. Kaikiri and Nishimoto, 1995, p. 204. Type specimen.—IGPS coll. cat. no. 91766 (Holotype). Material.—MNHAH reg. nos. D1-018912 through D1- 018918 (from MJ-1), DI-018919 through D1-018924 (from MJ-2a), DI-018925 through D1-018941 (from MJ-3), and D1-018942 (from MJ-6). Emended diagnosis.—Shell of large size, mytiliform, rather thin except for ligamental area, moderately inflated; shell surface nearly smooth except for very fine, irregular, dense growth lines; byssal sinus roundly depressed; ligamental part rather thick; ligamental area rather broad, with 8 to 12 deeply concave resilifer grooves; lamellar liga- ment attachment area broader than groove, weakly de- pressed, surrounded by a fine ridge. Description.—Shell rather large in size for the genus, mytiliform, rather thin except for ligamental area, moder- ately inflated; apical angle about 60°; byssal sinus rather depressed; posterodorsal margin nearly straight or weakly PP ET & Re) % ira fH OP LES REN, S Le 3 © 5 a 2 = = a S 4 S E Pme Mollusca from “Miocene” Maéjima Formation 137 curved; posteroventral margin nearly parallel to anterior one, weakly curved; centroventral margin arcuate and smoothly continuing to antero- and posteroventral margin; shell surface nearly smooth, sculptured only by very fine, irregular, dense growth lines; ligamental part thick; ligamental area rather broad, weakly annulated, with 8 to 12 resilifer grooves on fully grown individuals; resilifer grooves subequal, perpendicular to posterodorsal margin; lamellar ligament attachment areas weakly depressed, broader than resilifer grooves, surrounded by a fine ridge, with U-shaped inner margin; three byssal-pedal retractor muscle scars on subligamental part of internal shell; pallial line shallow, coarse, irregularly dotted near beak; adductor muscle scar indistinct. Discussion.—The broad and shallow lamellar ligament attachment areas, narrow resilifer grooves and three byssal- pedal retractor muscle scars on the inner dorsal area indi- cate the Maéjima specimens are referred to the subgenus Hippochaeta. The ligamental area of the type species, Perna maxillata Lamarck, is well figured in Cox (1969) and Savazzi (1995). The examined specimens from the Maéjima Formation can be referred to Jsognomon (Isognomon) hataii Noda and Furuichi, 1972. This species was originally described from the Teshima Formation of the Tonosho Group in Teshima Island, Kagawa Prefecture, on the basis of a single incomplete left valve. Unfortunately, the shell features such as shape, thickness and surface sculpture are unknown because the holotype (IGPS coll. cat. no. 91766) is an inter- nal mold lacking both shell material and the posterior half of the ventral area. Comparison with the holotype shows that apical angle and ligamental features are identical. Consequently, /. (/.) hataii is transferred here to the subge- nus Hippochaeta, and the holotype is a fragmental juvenile specimen having less diagnostic characters. Earlier Matsubara (2001) preliminarily identified Isognomon from the Maéjima Formation as Pedalion murayamai Yokoyama, 1932, originally described from the “Bed III” (= ? middle Eocene Krasnopolievskaya Forma- tion, after Kafanov and Amano, 1997) in the Dorogawa- Hishitori Region, south Sakhalin. However, it becomes clear that the Maéjima specimens have deeper resilifer grooves, less depressed lamellar ligament attachment areas, coarser pallial line, and a much more indistinct adductor muscle scar than P. murayamai. In addition, the byssal area of P. murayamai is rather distinctly bent, while that of the Maéjima specimens is gently curved. Consequently, the Maéjima specimens are not referred to this species. It may be noted that the holotype of P. murayamai (UMUT reg. no. CM27020) is missing. The present species is also similar in shell shape to Pedalion tomiyasui Nagao, 1928a, from the middle Eocene Iojima Formation of the Okinoshima Group of Kyushu. However, it is easily distinguished from the latter species by having a larger shell with narrower resilifer grooves and weakly compressed lamellar ligament attachment areas. Pedalion clarki Effinger, 1938, originally described from the Oligocene Gries Ranch Formation of Washington, U.S.A., is another allied species, but differs in having more numerous resilifer grooves. Pedalion tugaruense Nomura, 1935a, originally de- scribed from the lower middle Miocene Tanosawa Formation in Aomri Prefecture, northeast Japan, is easily distinguished from /. (H.) hataii by its thicker, much more longitudinally elongate shell with higher ligamental area and much blunter umbonal angle. Distribution. — Teshima Formation of the Tonosho Group in Kagawa Prefecture, Eocene; Maéjima Formation in Okayama Prefecture, Eocene or Oligocene. Order Ostreoida Superfamily Pectinoidea Family Pectinidae Subfamily Chlamydinae Tribe Chlamidini Genus Chlamys [Röding, 1798] Subgenus Leochlamys MacNeil, 1967 @ Figure 5. Mollusca from the Maéjima Formation (1). All specimens in natural size, unless otherwise stated. 1. Calyptraea sp. Dorsal view of internal mold, MNHAH reg. no. D1-018890, x1.5. 2. Muricidae? gen. and sp. indet. Dorsal view, 3. Naticidae? gen. and sp. indet. D1-018891, silicon rubber cast, x 1.5. 4. Acila (Truncacila) cf. nagaoi Oyama and Mizuno. 5. Left valve, MNHAH reg. no. DI-018897 (paratype). 7a-c. Right valve, MNHAH reg. no. D1-018896 (holotype), silicon rubber cast. Umbonal view. 12. Left valve MNHAH reg. no. D1-018898 (paratype), compressed umbonal-ventrally. 8. Internal view of left valve, MNHAH reg. no. DI-018911. 14. Right valve, MNHAH reg. no. DI-018908. All specimens silicon rubber casts. nesium oxide. MNHAH reg. no. D1-018893, silicon rubber cast, «1.5. ber cast. 5, 6, 7a-c, 12. Arca (Arca) uedai sp. nov. D1-018899, x1.5. 8, 9, 14. Septifer (Mytilisepta) sp. D1-018905. All specimens whiten by mag- Dorsal view, rather compressed, MNHAH reg. no. Left valve, MNHAH reg. no. D1-018895, silicon rub- 6. Left valve, MNHAH reg. no. 7a. External view. 7b. Internal view. 7c. All specimens silicon rubber casts. 9. Internal view of right valve, MNHAH reg. no. 10a-b. Glycymeris (Glycymeris) sp. Left valve. MNHAH reg. no. D1-018904, silicon rubber cast. 10a. External view. 10b. Internal view showing especially strong teeth and ligamental area with chevron sculpture. 11. Delectopecten sp. (Leochlamys) namigataensis (Ozaki). Isognomon (Hippochaeta) hataii Noda and Furuichi. valve. MNHAH reg. no. DI-018926. silicon rubber casts. Internal view of left valve, MNHAH reg. no. D1-018943, silicon rubber cast, 2. 13. Right valve, MNHAH reg. no. DI-018945. 15. Right valve lacking ventral part. MNHAH reg. no. D1-018929. 17. Internal view of right valve, showing ligamental area. 13, 18. Chlamys 15, 16, 17. 16. Internal view of left MNHAH reg. no. DI-018916. 18. Left valve, MNHAH reg. no. DI-018944. All specimens SS = Ss © >) a 5 = = D Ss Ss Fr Mollusca from “Miocene” Maéjima Formation 139 Leochlamys MacNeil, 1967, p. 9-10. Azumapecten Habe, 1977, p. 82. Type species. — Chlamys (Leochlamys) tugidakensis MacNeil, 1967, by original designation. Unnamed “Plio- cene” in Tugidak Island, Alaska, U.S.A. Discussion. — Habe (1977) proposed the subgenus Azumapecten on the basis of the following description: “Shell of small to moderate size; right valve rather inflated, with irregular, spiny radial ribs; left valve rather com- pressed; anterior and posterior auricles intercalating a beak between them, rather large; posterior auricle rather oblique; byssal notch on anterior part of right valve” (translated from Japanese by the present writer). Pecten (Chlamys) farreri Jones and Preston, 1904, living in the Northwest Pacific was designated as the type species. The original description of Azumapecten involves several obscurities in the diagnosis and is not associated with any comparison to allied genera or subgenera. However, many malacologists have treated Azumapecten as a valid genus or subgenus (e.g. Habe, 1981; Waller, 1993; Hayami and Matsumoto, 1995; Wang, 1996; Higo et al., 1999; Hayami, 2000). On the other hand, MacNeil (1967) proposed the subge- nus Leochlamys which was typified by Chlamys (Leochlamys) tugidakensis MacNeil, 1967. MacNeil (1967) and Sinelnikova (1975) also referred “Chlamys nipponensis Kuroda” (= P. (C.) farreri) to the subgenus Leochlamys. Indeed, the large anterior auricle, deep byssal notch, relatively strong ctenolium, irregular spiny ra- dial ribs on shell surface, shagreen microsculpture at least on interspaces of ribs, and absence of distinct crenulations on the inner ventral margin are common to both subgenera. Consequently, Azumapecten Habe, 1977, is a junior syno- nym of Leochlamys MacNeil, 1967. Chlamys (Leochlamys) namigataensis (Ozaki, 1956) Figures 5.13, 5.18, 6.12, 6.15 Pecten (Chlamys) namigataensis Ozaki, 1956, p. 7-8, pl. 2, fig. 4. Chlamys (Mimachlamys) namigataensis (Ozaki). Kaikiri and Nishimoto, 1995, p. 204. Chlamys ashiyaensis (Nagao). Nemoto and O’Hara, 2001, pl. 2, fig. 2. [not of Nagao, 1928b] not Chlamys (Mimachlamys) namigataensis (Ozaki). Masuda, 1962, p. 188, pl. 21, fig. 1. [Chlamys sp.] Type specimens.—NSMT reg. no. P1-4379 (Holotype and paratypes). Although Ozaki (1956) noted a specimen registered under this number as the holotype, two unfigured specimens are also registered under the same number. They are paratypes. Material—MNHAH reg. nos. D1-018944 through D1- 018951 (from MJ-2c), and D1-018952 (from MJ-4). Emended diagnosis. — Moderate-sized Chlamys (Leo- chlamys) with 15 to 19 highly elevated radial ribs; fine ra- dial threads appearing above ribs on ventral half of disc; left valve with an intercalary rib; radial sculptures densely imbricated; anterior auricle large, with a deep byssal notch and strong byssal fasciole on right valve; shell surface sculptured by a shagreen microsculpture. Description.— Shell moderate in size, slightly higher than long, suborbicular, rather thin; apical angle between 85° and 95°; both valves with a shagreen microsculpture; lacking internal rib carinae. Right valve weakly inflated; radial ribs 18 to 19, rather irregular, highly elevated, with three radial striations mak- ing ridges; ribs on both dorsal parts finer than those on cen- ter, finely imbricated; interspace of ribs rather deep, with or without an intercalary rib; anterior auricle large, sculptured by 6 to 7 fine radial ribs; byssal notch deep; ctenolium sev- eral in number, strong; byssal fasciole broad, strongly annulated; posterior auricle about half the length of the an- terior one, with 7 to 8 radial ribs, weakly oblique anteriorly; resilifer pit moderate in size, with a weak resilifer tooth on both dorsal flanks; anterior dorsal tooth weak, long. Left valve also weakly inflated; radial ribs 15 to 18, highly elevated, rather regular, with three sharp primary striations; an intercalary rib on each interspace; postero- dorsal part sculptured by fine, imbricated, radial striations; secondary radial striations appearing at about 40 mm from + Figure 6. Mollusca from the Maéjima Formation (2). nesium oxide. 1, 6a-b. Cyclocardia sp. 6a. External view lacking umbonal and antero-ventral parts. specimens silicon rubber casts. 2. Lucinidae gen. and sp. indet. All specimens natural size, unless otherwise stated. All specimens whitened by mag- l. Left valve, MNHAH reg. no. D1-018956, x2. 6a-b. Right valve. MNHAH reg. no. DI-018955. 6b. Internal view, especially showing transported cardinal teeth, both of x 1.5. Both Left valve, MNHAH reg. no. D1-018954, silicon rubber cast, x2. 3, 10. Mactra? sp. 3. Internal view of left valve, MNHAH reg. no. DI-018969, 10. Internal view of right valve, MNHAH reg. no. D1-018968. Both speci- mens silicon rubber casts, x2. 4a-b. Tapes? sp. MNHAH reg. no. D1-018971, x2. 4a. Internal view. 4b. External view. Silicon rubber cast. 5, 7, 8, 11. Megangulus maximus (Nagao). 5. Internal view of right valve, MNHAH reg. no. D1-018965, x2. 7. Internal view of left valve, MNHAH reg. no. DI-018964, x1.5. 8. Left valve lacking posterior part of shell, MNHAH reg. no. D1-018961, x1.5. 11. Internal view of right valve lacking ventral part, MNHAH reg. no. D1-018962, x2. All specimens silicon rubber casts. 9a-b. Crassostrea sp. Left valve. MNHAH reg. no. DI1-018953. 14a. External view. 14b. Internal view. 12, 15. Chlamys (Leochlamys) namigataensis (Ozaki). 12. Left valve lacking posterior half of shell. MNHAH reg. no. D1 -018946. 15. Left valve lacking ventral part and anterior auricle. MNHAH reg. no. DI -018947. 13, 14. Isognomon (Hippochaeta) hataii Noda and Furuichi. 13. Right valve, slightly compressed. MNHAH reg. no. DI-018928. 14. Right valve. MNHAH reg. no. D1-018925. Both specimens silicon rubber casts. 140 Takashi Matsubara beak; striations on radial ribs and internal ribs tending to become imbricated ventralward with growth; anterior auri- cle sculptured by 10 to 14 fine, imbricated radial ribs; pos- terior auricle as in right valve. Discussion.—Masuda (1962) considered the present spe- cies to be a member of the subgenus Mimachlamys Iredale, 1929, as a result of examination of a single right valve col- lected from the middle Miocene Kawazu Formation in Shimane Prefecture. However, his specimen has lower ra- dial ribs, a shallower byssal notch and a broader apical angle, and is not referred to the present species. The specimens from the Maéjima Formation have a large anterior auricle, deep byssal notch with strong ctenolium, and distinct shagreen microsculpture. The shagreen microsculpture is one of the diagnostic features of the tribe Chlamidini (Waller, 1993). Thus, the present species is re- ferred to the subgenus Leochlamys MacNeil, 1967. The diagnosis of the present species is emended as above, add- ing the right valve features. Recently, Nemoto and O’Hara (2001) figured a right valve specimen identified as Chlamys ashiyaensis (Nagao, 1928b) from the upper Eocene or lower Oligocene Iwaki Formation of the Shiramizu Group in the Joban Coalfield, northeast Honshu, Japan. Their figured specimen (Nemoto and O’Hara, 2001, pl. 2, fig. 2) is, however, unmistakably referred to the present species. Pecten (Chlamys) ashiya- ensis Nagao, 1928b is distinguished from Chlamys (Leochlamys) namigataensis (Ozaki) by having a more compressed shell with more numerous, lower, more irregu- lar radial ribs lacking dense imbrications. Distribution. — Namigata Formation in Okayama Prefecture, Paleogene; Iwaki Formation of the Shiramizu Group in Fukushima Prefecture, late Eocene or early Oligocene; Maéjima Formation in Okayama Prefecture, Eocene or Oligocene. Subclass Heterodonta Order Veneroida Superfamily Carditoidea Family Carditidae Subfamily Venericardiinae Genus Cyclocardia Conrad, 1867 Cyclocardia sp. indet. Figure 6.1, 6.6a-b Material—MNHAH reg. nos. D1-018955 (from MJ-4), D1-018956 and D1-018957 (from MJ-5). Description. — Shell small, ovate, longer than high, inequilateral, oblique anteriorly, weakly inflated; radial ribs 19 to 23, rather low, round-topped, less curved; radial ribs on anterior two-thirds of shell subequal to their interspaces and broader than them on posterior part; pallial line dis- tinct; anterior adductor muscle scar ovate, distinct; poste- rior adductor muscle scar oblong, weakly impressed; inner ventral margin crenated. Discussion.— A single articulated specimen and two right valves have been obtained. It is interesting that one specimen has a transposed hinge (Figure 6.6b). Cyclocardia sp. from the Maéjima Formation closely re- sembles Cyclocardia takedai (Honda, 1980) (new name for Venericardia elliptica Takeda, 1953), from the middle to upper Eocene Poronai Formation of Hokkaido. However, the former species has round-topped radial ribs while those of the latter species are flat-topped. Cyclocardia tokunagai (Yokoyama, 1924) from the lower Oligocene Asagai Formation in Fukushima Prefecture is another allied species. However, this species is distinguished from Cyclocardia sp. from the Maéjima Formation by having a more triangular, more inequilateral shell with longer posterodorsal margin, less curved ventral margin and more numerous radial ribs. The present spe- cies differs from Cyclocardia siogamensis (Nomura, 1935b), recorded from the lower-middle Miocene of Japan and Korea, in having a less inflated shell with lower and broader radial ribs. Superfamily Tellinoidea Family Tellinidae Subfamily Tellininae Genus Megangulus Afshar, 1969 Megangulus maximus (Nagao, 1928) comb. nov. Figure 6.5, 6.7, 6.8, 6.11 Tellina maxima Nagao, 1928b, p. 80, pl. 4, figs. 8-10. Angulus (Tellinides) maximus (Nagao). Oyama et al., 1960, p. 200-201, pl. 61, fig. 6; Kamada, 1980, p. 333, pl. Pg-18, fig. 7; p. 334, pl. Pg-19. figs. 15, 16; p. 335, pl. N-93, fig. 4; Fuse and Kotaka, 1986, pl. 18, figs. 20, 21. ? Angulus (Tellinides) maxima (Nagao). Matsumoto, 1964, p. 106, pl. 1, fig. 14. Type specimens.—IGPS coll. cat. nos. 36412 (Holotype) and 36452 (Paratypes). Material.—MNHAH reg. nos. D1-018960 (from MJ-4), D1-018961 through D1-018963 (from MJ-5), and DI- 018964 through D1-018965 (from MJ-6). Description. — Shell rather small, transversely elongate subelliptical, thin, slightly inequilateral, compressed; anterodorsal margin weakly curved; anterior dorsoventral margin rounded; posterodorsal margin nearly straight, nar- rowly depressed along ligament; posterior end oblique, nar- row, subtruncated; beak low, pointed, weakly opisthocline, situated slightly posterior to middle of shell; posterior ridge weak; shell surface nearly smooth, sculptured by faint, very Mollusca from “Miocene” Maéjima Formation 141 fine, commarginal growth lines which are periodically strengthened; growth lines also rather strengthened on ven- tral part; hinge plate narrow; both valves with two small cardinal teeth and a weak, thin, long lateral tooth; posterior tooth of right valve and anterior tooth of left valve weakly bifid; nymph low; adductor muscle scars and pallial line in- distinct. Discussion.—Oyama et al. (1960) transferred the generic position of Tellina maxima Nagao, 1928b to Angulus (Tellinides) without discussion. Indeed, a thin, compressed shell with small cardinal teeth and weak posterior ridge of the present species could well be identical with those of the type species of Tellinides, Tellina timorensis Lamarck. However, the anterolateral tooth of the present species is much longer and less oblique than that of the latter. Tellina nitidula Dunker (= Fabulina hokkaidoensis Habe, 1961), the type species of Nitidotellina Scarlato, 1961, also resem- bles 7. maxima in having a thin, compressed shell, but the anterior end of the anterolateral tooth on the right valve is angularly pointed ventralward (see Habe, 1977, pl. 41, fig. 5). The most appropriate genus for 7. maxima is Megangulus Afshar, 1969. Although the members of this genus generally have a larger and thicker shell with surface sculptured by commarginal grooves, I assign Tellina maxima Nagao, 1928b to it on the basis of the cardinal properties (see Matsukuma er al., 1988 for precise internal shell features of the Recent species). Megangulus maximus (Nagao, 1928b) is closely similar to Peronidia ochii Kamada, 1962, originally described from the upper Eocene or lower Oligocene Iwaki and Asagai formations in Joban Coalfield, Fukushima Prefecture, northeast Japan. However, the former species presents a shorter shell with a more rounded posteroventral margin than the latter one. Angulus okumurai Taguchi, 1992, from the lower Miocene Yoshino Formation in Okayama Prefecture, also resembles the present species. However, the former species is distinguished from it in having a larger, more equilateral shell with orthogyrous beak and more rounded posterior margin. The precise generic position of A. okumurai is also dubious because the cardinal properties have not been sufficiently examined. Tellina (Peronidea) lutea t-matumotoi Otuka, 1940, originally described from the Miocene “Wakkauenbetu Fo rmation” of northern Hokkaido is distinguished from the present species in having a larger shell with a beak situated more anteriorly, and longer, more produced posterior dorsoventral margin. Tellina vestalioides Yokoyama, 1920 is easily distin- guished from the present species by having a more inflated shell with a stronger posterior ridge, weakly concave posteroventral margin behind a posterior ridge, more dis- tinctly truncated posteroventral margin, and stronger cardi- nal teeth. Although Matsumoto (1964) reported Angulus (Tellinides) maximus (Nagao) from the lower Miocene Oga Formation in Shizuoka Prefecture, his figured specimen has a more inflated shell with a beak situated slightly anterior to the middle of the shell, and is not referred to the present species. The specimen from the Öga Formation of Matsumoto (1964) is probably conspecific with Hiatula minoensis (Yokoyama) sensu Shibata and Kato (1988). Distribution.—Funazu Sandstone Member of the Iojima Formation of the Okinoshima Group in Nagasaki Prefecture, late Eocene; Kishima Formation in Saga Prefecture, latest late Eocene to earliest early Oligocene; Yamaga Formation of the Ashiya Group in Fukuoka Prefecture, latest early to early late Oligocene; Kiwado and Taoyama Formations of the Hioki Group in Yamaguchi Prefecture, late Oligocene; Maéjima Formation in Okayama Prefecture, Eocene or Oligocene. Superfamily Mactroidea Family Mactridae Subfamily Mactrinae Genus Mactra Linnaeus, 1767 Mactra? sp. indet. Figure 6.3, 6.10 Material. -MNHAH reg. nos. D1-018967 (from MJ-4), and D1-018968 through D1-018970 (from MJ-6). Description. — Shell rather small, roundly subtrigonal, slightly longer than high, moderately inflated; hinge plate narrow; cardinal and lateral teeth rather weak; anterior and posterior lateral teeth thin; resilifer small, shallowly de- pressed. Discussion. — On the basis of cardinal properties, this species is unmistakably referred to the family Mactridae. Unfortunately, the presence or absence of a lamellar plate between resilifer and nymph, and the mode of pallial sinus were not examined in the present material due to poor pres- ervation. Thus, the generic assignment is provisional. “Mactra sp.” was regarded as one of the characteristic elements of the Mactra-Acila assemblage from the “Miocene” around the eastern part of the Seto Inland Sea (Itoigawa, 1983). Acknowledgments I would like to express my appreciation to Y. Yamamoto (Okayama University) for his valuable suggestions on the fossil localities and stratigraphy of the Maéjima Formation. Acknowledgments are also due to T. Kase (National Science Museum, Tokyo), J. Nemoto (Tohoku University), T. Sasaki (University Museum, University of Tokyo) and 142 Takashi Matsubara H. Kato (Natural History Museum and Institute, Chiba) for their kind assistance in examining specimens. I am in- debted to H. Saegusa (Museum of Nature and Human Activities, Hyogo Himeji Institute of Technology) and Y. Suzuki (National Science Museum, Tokyo) for their co- operation in collecting references. I am grateful to G. J. Vermeij (University of California at Davis) and K. Amamo (Joetsu University of Education) for reviewing the manu- script and providing valuable comments. This study was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Sciences (no. 12740293). 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Imperial Geological Survey, Report, no. 111, p. 1-15 (Japanese part), p. 1-12 (English part), pls. 1-4. 145 Paleontological Research, vol. 6, no. 2, pp. 147-178, June 28, 2002 © by the Palaeontological Society of Japan Eocene shallow marine foraminifera from subsurface sections in the Yufutsu-Umaoi district, Hokkaido, Japan SATOSHI HANAGATA Japan Petroleum Exploration Co. Ltd., NYK Tennoz building, 2-2-20, Higashishinagawa, Shinagawa-ku, Tokyo 140-0002, Japan (Present address: Akita Prefectural Office, 4-1-1 Sannou, Akita-shi, Akita 010-8570, Japan) Received March 26, 2001; Revised manuscript accepted January 29, 2002 Abstract. In subsurface sections of the Yufutsu-Umaoi district, Hokkaido, northern Japan, three Eocene benthic foraminiferal assemblage zones were defined in the Ishikari Group and the overlying Poronai Formation. They are in ascending order: Evolutinella subamakusaensis-Haplophragmoides crassiformis Assemblage Zone, Globocassidulina globosa-Cribroelphidium sorachiense Assemblage Zone, and Bulimina schwageri-Angulogerina hannai Assemblage Zone. Assemblages characterizing each zone indicate the littoral to the inner sublittoral, middle sublittoral, and outer sublittoral paleobathymetric zones, respectively. A foraminiferal fauna in the upper bathyal zone was also identified based on reinterpretation of previous stud- ies. It is composed of calcareous species such as Gyroidina yokoyamai and Plectofrondicularia packardii. Abundant occurrences of agglutinated foraminifera in shallower paleoenvironment suggest brackish and re- lated stratified-water paleoenvironments caused by freshwater input into an embayment called the “Poronai Sea”. Such stratified conditions in coastal shallow marine areas may have formed oxygen-depleted zones as suggested in the previous study. These data and their paleoenvironmental implications are expected to fur- nish a basis for further consideration on geohistory of the Paleogene formations and also on the Eocene foraminiferal fauna of the northwestern Pacific. Key words: Eocene, foraminifera, Ishikari Group, paleoenvironment, Poronai Formation Introduction The purpose of the present paper is to delineate the Eocene shallow marine foraminiferal assemblages from borehole sections in the Yufutsu-Umaoi district, southern Ishikari Plain, Hokkaido, northern Japan; to consider depositional environments; and to describe paleobathy- metric distributions of benthic foraminifera. Studies of the Japanese Paleogene smaller foraminifera began with the report of Yokoyama (1890). Following him, studies have been conducted mainly on the fossils from the Ishikari Group and the overlying Poronai Formation in the coalfield regions of Hokkaido and from the Kyoragi Formation of the Hondo Group in the Amakusa Islands, Kyushu, southwestern Japan (e.g. Asano, 1952, 1954, 1958, 1962; Asano and Murata, 1957; Fukuta, 1962). Paleogene foraminiferal faunas at various localities in Hokkaido were studied by Kaiho (1983, 1984a, b, c) who reported on their stratigraphic and paleogeographic distributions. Kaiho (1992b) also conducted a com- parative taxonomic study of the Paleogene foraminiferal faunas from Hokkaido with other regions of the world, and recognized some species from the Poronai Formation as an “intermediate-water” fauna. His “intermediate-water” has a depth range of 100-1000 m (Kaiho, 1992b). This range almost corresponds to three bathymetric zones in the mod- ern northwestern Pacific coast of Japan according to the compilation of Akimoto and Hasegawa (1989). They are the outer sublittoral zone (approximately 70 to 180 m), upper bathyal zone (180 to 550 m) and upper middle bathyal zone (550 to 900 m). However, correlation of each paleobathymetric zone with the foraminiferal fauna was not discussed in the report. Deep marine foraminiferal assemblages generally in- clude elements transported from shallower marine environ- ments by bottom currents and/or gravity currents (Zalesny, 1959; Ingle, 1980). This means that the deep marine fauna can be recognized only after the shallower marine fauna has been identified. However, little is known about the Paleogene shallow marine foraminiferal faunas in 148 Satoshi Hanagata Kita-Akebono SK-1D A Le 141°45' 141°7'30" Ë 1 42°42' É Sankebetsu Formation (| © (lower part) \ -_ Ashibetsu Study area of Ujiié and Watanabe (1960) | Poronai i + Momijiyama Formation 43° À Numanohata SK-4D Yufutsu Oil and Gas Field Main study area of — 42°40 À A SK-3D — + 42°38 | 141°45 | 42°38' L 141°7'30" 0 2km [— = —_—} Tomakomai Port Pacific Ocean Figure 1. Index map showing the well sections studied. drawn in a 500-meter thickness interval (Japan Natural Gas Association and Japan Offshore Petroleum Development Association, 1992). Dark areas show surface distribution of the Poronai Formation, Momijiyama B = Location of the wells in the Yufutsu oil and gas field. Double circles indicate Thick lines indicate wells used in this study. eircles indicate the sites of the wells controlling the isopachs. Formation, and their equivalents after Yamada et al. (1982). the sites of the wells, and small dots indicate the bottom of the wells. Hokkaido. The material I examined in the present study is from marine strata (Poronai Formation) which grades from nonmarine coal-bearing formation (Ishikari Group), repre- senting a transgressive phase, and thus provides an oppor- tunity to study the shallow marine fauna. Moreover, because paleoenvironments of the Paleogene in Hokkaido and the northwestern Pacific region have not been well studied, data on paleobathymetric distribution of foramini- fera examined in the present study are expected to provide a basis for further studies in the region. Japan Petroleum Exploration Co. Ltd. (JAPEX) has been exploring oil and natural gas in the southern Ishikari Plain. Since the discovery of the Yufutsu oil and gas field, whose reservoir is in the Cretaceous granitoids and Paleogene conglomeratic formations, many wells have been drilled Kaiho (1984a, b) Pacific Ocean H 50 km A = Dashed lines denote isopachs of the Poronai Formation and its equivalents Double penetrating the Paleogene rocks, namely, the Ishikari Group and the overlying Poronai Formation (Yufutsu Research Group of JAPEX Sapporo et al., 1992; Fujii and Moritani, 1998; Kurita and Yokoi, 2000). The present study was conducted on three well sections in the Yufutsu oil and gas field, Numanohata SK-3D, Numanohata SK- 4D and Kita-Akebono SK-1D. In addition, the well MITI Umaoi, drilled in the Umaoi Hills about 25 km north of the Yufutsu oil and gas field, was also investigated (Figure 1; MITI = Ministry of International Trade and Industry). The present study refers to the area including these wells as the “Yufutsu-Umaoi district”. Eocene shallow marine foraminifera 149 Geological setting The middle Eocene Ishikari Group crops out in the hilly areas of the Yubari and Sorachi coal fields (Kaiho, 1983; lijima, 1996). It is composed of alternating marine and nonmarine formations. Thick coal beds are present in the nonmarine part. The Poronai Formation, which overlies the Ishikari Group, outcrops in the Yubari and Ashibetsu districts (Figure 1). It is composed mainly of massive siltstone that intercalates with acidic tuff beds in the middle to upper part (Kaiho, 1983). The geologic age of the Poronai Formation in the Yubari district was determined by calcareous nannofossils to be late Middle Eocene to Late Eocene in age (Okada and Kaiho, 1992). Broad distribution of the Poronai Formation and its equivalents in the subsurface of the Ishikari Plain is confirmed by boreholes (Figure 1A: Japan Natural Gas Association and Japan Offshore Petroleum Development Association, 1992; Japanese Association for Petroleum Technology, 1993). Many researchers have discussed the stratigraphic rela- tionship between the Ishikari Group and the overlying Poronai Formation since Yabe (1951) proposed their heteropic facies (synchronous) relationship (Asano, 1952, 1954; Saito, 1956; Sasa, 1956; Sasa er al., 1953; Yabe and Asano, 1957; Uchio, 1961, 1962), although no conclusive interpretation has yet been drawn. The present study as- sumes a conformable contact between them in the borehole sections studied here. This interpretation is based on tran- sitional characteristics of lithology as discussed later. Lithostratigraphy of study sections Lithologic columns of the study wells are presented in Figure 2. Lithologic descriptions of each section are based on the wellsite survey of ditch cuttings. Numbers shown on the left of each column are drilling depths from the sur- face. All study wells of the Yufutsu oil and gas field are deviated, therefore drilling length differs from true thick- ness of formation. In addition, formation contacts are placed on the basis of wireline logs whose depths may not match the drilling depths measured by the length of drill pipes. Interpretations of wireline logs prove that the uppermost part of the Poronai Formation is missing because of a fault in Numanohata SK-3D. Also because of a fault, an inter- val from the lowermost Poronai Formation through the upper part of the Ishikari Group is repeated in Numanohata SK-4D. After correcting for well deviations and formation dips, the true thickness of the Poronai Formation in the Yufutsu oil and gas field is estimated as approximately 450 m to 500 m, while in the vertical well MITI Umaoi, it is approxi- mately 780 m. Lithology of the Ishikari Group and the Poronai Formation in the study well sections is similar. Its vertical changes are as follows in ascending order; basal conglom- erate bed, medium to finer sandstones with siltstone beds, and finally siltstones and mudstones. The basal conglom- erate of the lowermost part of the Ishikari Group grades up- ward, intercalating with finer-grained sediments, into an alternation sequence of medium to fine sandstone beds and olive-black to olive-gray siltstone beds. Coal beds are fre- quent. The sandstone and siltstone beds of the uppermost Ishikari Group grade upward into the siltstone and mudstone of the Poronai Formation, which contains marine fossils such as foraminifera, ostracods, dinoflagellates, and fragments of mollusks. The Poronai Formation consists mainly of olive-gray or dark gray siltstone and mudstone. Tuff and sandstone beds intercalate in the upper part of the formation in Kita-Akebono SK-1D and MITI Umaoi, where the formation is thicker than in the other well sec- tions. The Upper Oligocene Minaminaganuma Formation unconformably overlies the Poronai Formation in the Yufutsu-Umaoi district (Kurita and Yokoi, 2000). The Lower Oligocene Momijiyama Formation (Kaiho, 1983; Kurita and Miwa, 1998), which overlies the Poronai Formation in the Yubari district, is not present in the study area. The upward fining of the sediments without any break from the Ishikari Group to the lower part of the Poronai Formation in the Yufutsu-Umaoi district suggests a transgressive sequence. Samples and methods All borehole samples used in the present study are ditch cuttings. Borehole conditions during drilling were good, and contamination caused by the caving was negligible. Samples were taken every 20 m; additional samples were taken from the siltstones in the coal-bearing formation. In the Kita-Akebono SK-1D well, samples were collected at every 10 m for most of the studied interval. A total of 173 samples were examined. All samples were oven-dried. Subsamples of about 100 g were soaked in boiled sodium sulfate supersaturated solution for about three hours. After removing excess so- lution, soaked samples were left more than three days. Then they were wet sieved through a 125 um-opening screen. All specimens in the residues were picked and identified under a binocular microscope. Percentages of planktonic species, agglutinated species, and calcareous benthic species, and total populations were determined for these samples. Diversity, species richness (number of species) as well as “Simpson’s Index for Diversity” (SID: Simpson, 1949) were used to analyze the 150 South LEGEND Ge] Claystone Siltstone EX Sandstone 24 Conglomerate HB Coal [TTT] Tutt <4 intrusion rock A pumice-bearing m contain coaly matter æ Ostracoda h + Calcareous Nannofossil | 3070.5 m NUMANOHATA SK-3D Upper Oligocene MINAMI- NAGANUMA FORMATION 3700m PORONAI FORMATION 3804.0 m ff 3900m En | il nt Ye 4000m D it ISHIKARI am il Figure 2. arranged at the base of the Poronai Formation. Satoshi Hanagata NUMANOHATA SK-4D 3000m 773 3678.5 m FAULT 3900m F5 Stratigraphic correlation based on lithostratigraphy and wireline geophysical loggings of the study wells. MITI Umaoi KITA-AKEBONO SK = 1 D 3600m [7 7] 3640.0m Tip un 2 3800mF 3900m 4000m 4100m 3400m 4200m 6 © 0009 488 3500m 4300m 3600m | à : Base of 3628.0 mi. wl foraminiferal occurrence ee 3900m |: fie a Well sections are Eocene shallow marine foraminifera = K ITA-AKEBONO = SK-1D >3 Stratigraphic distribution = Total Calcareous of selected species = population benthic (%) (numbers of specimens in 100 g rock) So 0 1000 o 100 5 60 40 100 40 60 20 RS SE, @l 2 : = À = ale = | 25 Biostratigraphic [7] = = = £ 2 3 < S| CL subdivision Z SM a les (This study) a a R Q S| à > SI = sl à] Sl § = & ST 37s Bir SPS si) al à S/S Sis Rare £ = 2 Ace SI el al SE foraminiferal a Sl. 8 interval SE SSNS SS eee ee kurs: zZ 5 ) ö =| 8 Bulimina schwageri - = & | "| Angulogerina hannai = Assemblage Zone D |) Eee Gey oa a Esel BRE > cc = . . = Globocassidulina e globosa - Z ce = Cribroelphidium = sorachiense a. Assemblage Zone 3628.0 m Evolutinella subamakusaensis - Haplophragmoides crassiformis Assemblage Zone PP es ohes ees ea Barren foraminiferal interval ISHIKARI GROUP 4000m For Legend, see Figure 2. | Figure 3. Stratigraphic occurrences of the selected species in Kita-Akebono SK-1D 152 Satoshi Hanagata South LEGEND Et Total population of Calcareous Benthic foraminifera Total population of Porcellaneous foraminifera EE Total population of Agglutinated foraminifera Percentage of Evolutinella subamakusaensis + Haplophragmoides crassiformis Percentage of Globocassidulina globosa + Cribroelphidium yabei FRERE Percentage of Bulimina schwageri + Angulogerina hannai For lithology, see Figure 2. NUMANOHATA SK-4D Total Index population species 0 50% 0 300 N Rare foraminiferal |....., interval 3000m FR 3227 it | Kr 3070.5 m if Total Index population species 0 250 0 50% NUMANOHATA i SK-3D i 3600m | MINAMI- NAGANUMA FORMATION Upper Oligocene PORONAI FORMATION Eocene ISHIKARI GROUP 3678.5 m FAULT | \ Aal ; 4000m Figure 4. Stratigraphic correlation of the study wells based on the assemblage zones of foraminifera. Left columns of each well section are cumulative (agglutinated, porcellaneous and calcareous foraminifera) total populations in 100 g rock samples. Curves in right column indicate per- centage of index species against total population. KITA-AKEBOND 3067.0m |} : 3200m| SK-1D Total population 0 4000m 1000 0 Index species 50% — Eocene shallow marine foraminifera MITI Umaoi Total Index population species 0 500 0 50% 3600mp 777] cena Ne I} ï 1 A it À N N a bf : ' i h | 1 u Pr LA i" N eal H 4 a CA TEs > 7 .. ww w ea N à a SE mi ? = U FA 4 | 4 f North Foraminiferal Assemblage Zones Bulimina schwageri - Angulogerina hannai Globocassidulina globosa - Cribroelphidium sorachiense Evolutinella subamakusaensis Haplophragmoides crassiforms Barren foraminiferal interval un Ww 154 Satoshi Hanagata assemblages. Only populations of specimens identified at species rank were used to calculate diversity; species identified as “spp.”, “sp. indet.”, and “miscellaneous” were excluded. Biostratigraphy As a result of analysis, 47 species belonging to 34 genera were identified from 162 samples (Appendix 1-3). Preser- vation of most specimens was poor. The present study established assemblage zones based on associations of index species based on the foraminiferal distribution. Index species are species that are abundant and have similar stratigraphic distribution among all borehole sections. Occurrences of selected species are plotted against depth for Kita-Akebono SK-1D (Figure 3). This plot reveals that some of the species have distinct similarities in stratigraphic occurrences. On the basis of this, the follow- ing three associations are recognized. 1) Evolutinella subamakusaensis and Haplophragmoides crassiformis. 2) Globocassidulina globosa and Cribroelphidium sora- chiense. 3) Bulimina schwageri and Angulogerina hannai. These three associations represent zones which occur in all the studied sections in the same stratigraphic order, and each has a unique distribution within the section (Figure 4). The upper part of the Poronai Formation above the Bulimina schwageri-Angulogerina hannai Assemblage Zone in Kita-Akebono SK-1D (depth 3200-3075 m) is re- ferred to here as “rare foraminiferal interval” because the number of foraminifera in the interval is so small. As dis- cussed later, boundaries between these assemblage zones are environmentally controlled and therefore may not indi- cate strict time horizons. Characteristics of each assemblage zone are discussed below. Boundaries between the zones are defined by changes in the abundances of the index species. Evolutinella subamakusaensis-Haplophragmoides cras- siformis Assemblage Zone. —This zone is characterized by abundant occurrences of the two index species. It also characteristically includes agglutinated foraminifera such as Reticulophragmium amakusaensis, Cyclammina pacifi- ca, and Recurvoidella sp. cf. R. lamella. The calcareous foraminifer Cribroelphidium sorachiense occurs rarely in this zone. Assemblages of this zone are characterized by generally small populations and low diversity. Globocassidulina globosa-Cribroelphidium sorachiense Assemblage Zone.—In addition to the two index species, this zone includes abundant agglutinated foraminifera such as Evolutinella subamakusaensis, Recurvoidella sp. cf. R. lamella, and Budashevaella symmetrica, and more calcare- ous species such as Melonis pompilioides and Pullenia salisburyi than in the assemblages of the underlying E. subamakusaensis-H. crassiformis Assemblage Zone. Bulimina schwageri-Angulogerina hannai Assemblage Zone.— Although this zone is similar to the G. globosa-C. sorachiense Assemblage Zone, it is distinguished by larger numbers and higher frequencies of both Bulimina schwageri and Angulogerina hannai. Assemblages of this zone also contain numerous agglutinated foraminifera, but have higher calcareous foraminiferal abundances and higher species diversities compared to those of the previous two assemblage zones. Paleoenvironment The foraminiferal fauna seen in the present material is characterized by the occurrence of abundant agglutinated foraminifera, especially species belonging to the Lituolidae and Cyclamminidae. No similar fauna so dominated by these agglutinated foraminifera has been reported from anywhere else in the world. Therefore, paleoenvironmen- tal implications of this peculiar fauna are considered based on the facts of modern foraminiferal distribution. In this section, the paleobathymetry of each assemblage zone and then the additional paleoenvironmental implications are discussed. Paleobathymetry As discussed by Ingle (1980) and McDougall (1980), paleobathymetric zonations of the Eocene Pacific Ocean are similar to the modern zonations. Paleobathymetric zonations used in the present study follow Akimoto and Hasegawa (1989)’s compilation of bathymetric distribu- tions of Recent benthic foraminifera around the Japanese Islands. Evolutinella subamakusaensis-Haplophragmoides cras- siformis Assemblage Zone. —This zone is considered to have been deposited in a shallow marine environment for the following reasons. First, it overlaps the coal-bearing formation of the Ishikari Group that is of paralic origin. Second, it yields benthic foraminifera Cribroelphidium sorachiense and Sigmoidella pacifica, both of which sug- gest shallow marine (sublittoral) deposition. Most modern Cribroelphidium live in shallow marine (outer sublittoral zone or shallower) environments, such as Cribroelphidium bartletti (Elphidium bartletti of Loeblich and Tappan, 1953), C. clavatum (E. clavatum of Buzas, 1966 and Lagoe, 1979). Sigmoidella pacifica also lives in modern shallow marine environments (Jones, 1994, as S. elegantissima). Third, assemblages of this zone lack Globocassidulina and Bulimina whose modern species live at depths greater than the inner sublittoral zone in the seas around the Japanese Islands (Akimoto and Hasegawa, 1989). Thus, the assem- Eocene shallow marine foraminifera 15 blages of the E. subamakusaensis — H. crassiformis Assemblage Zone are considered to indicate a paleobathy- metric range from the littoral zone to the inner sublittoral zone. Globocassidulina globosa-Cribroelphidium sorachiense Assemblage Zone. —The assemblages of this zone include Globocassidulina, which has its upper depth limit in the middle sublittoral zone (Akimoto and Hasegawa, 1989). In addition, C. sorachiense, C. wakkanabense and Sigmoidella pacifica, all of which indicate shallow marine environments, occur frequently in this zone. Therefore, the assemblages of the G. globosa — C. sorachiense Assemblage Zone are thought to indicate the middle sublittoral zone. Bulimina schwageri-Angulogerina hannai Assemblage Zone.—The assemblages of this zone are similar to those of the Globocassidulina globosa-Cribroelphidium sorachi- ense Assemblage Zone except that the percentages of Bulimina and Angulogerina are higher. Since modern spe- cies of Bulimina and Angulogerina have upper depth limits in the outer sublittoral (Akimoto and Hasegawa, 1989), the Bulimina schwageri-Angulogerina hannai zone is consid- ered to have been deposited in the outer sublittoral zone. The presence of Cribroelphidium species suggests either in situ deposition or transport of shallower-water species into the outer sublittoral zone, possible by marine currents. Kaiho (1992b) reported B. schwageri and A. hannai in his “intermediate-water” which ranges from depths of 100 to 1000 m. As the depth range of the outer sublittoral zone overlaps the range of Kaiho’s “intermediate water,” the present study agrees with Kaiho’s interpretation on B. schwageri and A. hannai. Historical paleobathymetric change.—Paleobathymetric interpretation of the three assemblage zones shows that the sedimentary environments during the deposition of the upper part of the Ishikari Group and the Poronai Formation in the Yufutsu-Umaoi district changed from the littoral zone to the inner sublittoral zone, then to the middle sublittoral zone, and finally to the outer sublittoral zone. The successive change in paleobathymetry suggests that the Stratigraphic interval from the first occurrence of foraminifera to the B. schwageri-A. hannai Assemblage Zone was deposited during a single transgressive phase. This interpretation supports the observation that the Ishikari Group and the Poronai Formation are conformable in the Yufutsu-Umaoi district. The “rare foraminiferal interval” at the depth 3190 m and shallower in Kita-Akebono SK-ID well indicates that a re- gressive phase followed the transgression discussed above. Evidence of the regression is based on the successive disap- pearances of the species, B. schwageri, A. hannai, G. globosa, and C. sorachiense. Shoaling of water depth pre- vented distribution of these depth-controlled species. un FORAMINIFERAL ZONES (Kaiho, 1984a, b, c) MEGA-FOSSIL ZONES (Teshima, 1954) Nonion ezoensis - Cyclammina paciffica Assemblage-zone Bulimina schwageri - Gyroidina yokoyamai Upper Bathyal Haplophragmoides subevolutus - Cyclammina pacifica Assemblage-zone Upper Bathyal Bulimina schwageri - H. umbilicatus Assemblage-zone = = = © E I =) as © = S LL © a H. umbilicatus - H. subevolutus Assemblage-zone H. tanaii - H. subevolutus A.-z. MJ : Momijiyama Formation Figure 5. Stratigraphic relation between the megafossil zones and foraminiferal assemblage zones. Consequently, the interval from the coal-bearing forma- tion of the Ishikari Group to the Poronai Formation in the Yufutsu-Umaoi district accumulated during a single transgressive and regressive sequence. This is only ob- served in the Kita-Akebono SK-1D well, since the upper- most part of the Poronai Formation is missing in the other well sections. Upper bathyal assemblages As a result of the study discussed above, species compo- sitions from the littoral zone to the outer sublittoral zones during the Eocene were described. Foraminiferal fauna of the upper bathyal zone (water depth approximately 180 to 550 m in northwestern Pacific coast of northern Japan), which is one rank deeper than the outer sublittoral zone, is not observed in the Yufutsu-Umaoi district. However, ex- istence of strata which show the upper bathyal environment was reported by Teshima (1955) in the middle part of the Poronai Formation in the Yubari district. Here, I describe upper bathyal foraminiferal fauna based on the correlation between biostratigraphy of Teshima (1955) and Kaiho (1984a, b). Teshima (1955) studied megafossils and di- vided the Poronai Formation into the A to I megafossil zones in ascending order, stating that the megafossil assem- blages of the B-C and H-I zones are similar to the molluscan association found in water depth interval of 200 to 300 m, offshore Otaru, Sea of Japan. This water depth in the Sea of Japan falls within the range of the upper bathyal zone (Akimoto and Hasegawa, 1989). According to the stratigraphic relationship between these megafossil 156 Satoshi Hanagata el (7 Sublitoral TBathyal] Species [inner | Middie | Outer | Upper | | Inner | Middle | Outer | Upper | AGGLUTINATED Cribroelphidium ishikariense (Kaiho) R R R R Alveolophragmium sp.A of the present study Cribroelphidium sorachiense (Asano) A Ammobaculites sp. A of Kaiho, 1984b A Cribroelphidium sorachiense (Asano) var. A R Ammobaculkites akabiraensis Asano R Cribroelphidium wakkanabense (Kaiho) A Ammodiscus parianus Hedberg C Dentalina sp. cf. D. kushiroensis Yoshida R Ammodiscus tenuis Brady Cc Dentalina sp. cf. D. subsoluta (Cushman) R [03 Ammomarginulina sp. A of Kaiho, 1984b R Dentalina cocoaensis (Cushman) R C Bathysiphon eocenica Cushman and Hanna C Dentalina dusenburyi Beck R © Bathysiphon vernoni Hamlin R Dentalina minuta Kaiho R Budashevaella sp. aff. B. multicamerata (Voloshinova) R Elphidium mabutii Asano” R ? Budashevaella symmetrica (Ujiie and Watanabe) | Cc Elphidium sp. A of Kaiho, 1984b Cribrostomoides sp. cf. C. cretacea Cushman and Goudkot R Epistominella exigua muttiloculata Kaiho c Cyclammina ezoensis Asano R Eponides lobatus Kaiho R C Cyclammina orbicularis Brady R Fissurina marginata (Montagu) R G Cyclammina pacifica Beck A Fissurina sp. A of Kaiho, 1984b R R Cyclammina sp. aff. C. pusilla Brady R Fursenkoina uchioi Kaiho R C Cyclammina tani Ishizaki Glandulina laevigata ovata Cushman and Applin C C Cyclammina sp. A of the present study R Globobulimina ezoensis (Yokoyama) C C Cyclammina sp. B of the present study Globocassidulina globosa (Hantken) C C Discammina sp. À of Kaiho, 1984b Cc Globocassidulina sp. A of Kaiho, 1984b R © Discammina sp. B of Kaiho, 1984b R Globulina gibba (d'Orbigny) R Cc Discammina sp. C of Kaiho, 1984b R Guttulina problema (d'Orbigny) C C Eggerella sp. À of Kaiho, 1984b R Guttulina takayanagii Kaiho R R Evolutinella subamakusaensis (Fukuta) R Gyroidina yokoyamai (Ujiie and Watanabe) A Glomospira gordialis Jones and Parker R Heterolepa poronaiensis Kaiho C Haplophragmoides crassiformis Kaiho R Lagena sp. cf. L. Jaevis (Montagu) R R Haplophragmoides sp. cf. H. deflata Sullivan Lagena sp. cf. L. perlucida (Montagu) C Haplophragmoides rugosus soyaensis Yasuda Cc Lagena sp. cf. L. sulcata (walter and Jacob) R Haplophragmoides tanaï Kaiho C Lagena striata (d'Orbigny) R R Haplophragmoides yokoyamai Kaiho R R Lagena sp. A of Kaiho, 1984b R Haplophragmoides sp. Aof the present study R % Lenticulina antipoda (Stache) Cc Haplophragmoides sp. B of the present study R ? Lenticulina ishikariensis Kaiho Cc Haplophragmoides _ sp. D of the present study R 2 Lenticulina sp. A of Kaiho, 1984b R Hyperammina elongata Brady R R Lenticulina sp. B of Kaiho, 1984b R Karrerulina sp. cf. K. hokkaidoana (Takayanagi) Cc R Melonis affinis (Reuss) R Martinottiella crassa Kaiho R Melonis elegans Kaiho (© Martinottiella rectidelicata Kaiho R Melonis lobatus Kaiho R Placentammina sp. A of the present study R ? Melonis sp. cf. M. multisuturalis van Bellen R Poronaia poronaiensis (Asano) C R Melonis pompilioides (Fitchel and Moll) C C Recurvoidella sp. cf. A. lamella (Grzybowski) C ? Melonis subevolutus Kaiho R R Recurvoides sp. A of the present study R ? Nodogeneria sp. cf. N. lepidula (Schwager) R [03 Reophax minutirectus Kaiho R Nodosaria amchitkaensis (Todd)** Cc Reophax multicamerarus Kaiho R C Nodosaria longiscata d'Orbigny R G Reophax tappuensis Asano C Cc Nonion ezoensis Kaiho R C Reticulophragmium amakusaensis (Fukuta) A ? Nonion subangularis Kaiho R R Rhabdammina sp. R R Nonion takayanagii Kaiho R Silicosigmoilina? sp. R Nonionella japonica (Yokoyama) R R Spiroplectammina nuttalii Lalicker R Nonionella mabutii Asano R Trochammina sp. cf. T. asagaiensis Asano Oolina hexagona (Williamson) C Trochammina squamata Jones and Parker Oolina simplex Reuss C Verneuilinula takayanagii (Kaiho Oolina sp. cf. O. globosa (Montagu) R PORCELLANEOUS Oolina sp. A of Kaiho, 1984b R Quinqueloculina seminula compacta Serova Planulina poronaiensis Asano Tritoculina gibba d'Orbign: Plectofrondicularia delicatula Kaiho R CALCAREOUS HYALINE Plectofrondicularia packardii Cushman and Schencki c Anomalinoides sasai Kaiho C Plectofrondicularia smithi Kaiho Cc Anomalinoides sp. A of Kaiho, 1984b R Plectofrondicularia vaughani Cushman R Bolivina euplectella Yokoyama R Praeglobobulimina pyrula (d'Orbigny) R R Brizarina saitoi Kaiho Cc Praeglobobulimina ovata (d'Orbigny) A R Brizarina serrata Kaiho C Praeglobobulimina pupoides (d'Orbigny) C Bulimina schwageri Yokoyama A Procerolagena sp. cf. P. gracillima (Sequenza) R R Bulimina sculptilus Cushman C Pseudonodosaria conica (Neugeboren) R Bulimina sp. cf. B. sculptilus Cushman C Pseudonodosaria inflata (Costa) R C Bulimina yabei Asano and Murata R Pseudopolymorphina hokkaidoana Kaiho R R Buliminella robertsi Howe and Ellis Pullenia eocenica Cushman and Siegfus C ? Cancris torquertus Cushman and Todd R Pullenia salisburyi R. E. and K. C. Stewart © © Cassidulina lobatula Kaiho R Saracenaria ujiiei Kaiho R R Cassidulina yubariensis Kaiho R Sigmoidella pacifica Cushman and Ozawa G © Cassidulinoides howei Cushman [03 Sigmomorphina schencki Cushman and Ozawa C Cc Chilostomella sp. cf. C. cylindoroides Reuss R Sigmomorphina sp. A of Kaiho, 1984b R Cibicides elmaensis Rau R Stilostomella sp. cf. S. japonica (Ishiwada) R Cibicides complanatus Kaiho Trifarina hannai (Beck) C Cibicides sp. À of Kaiho, 1984b Uvigerina ombetsuensis Kaiho A Cibicides p. B of Kaiho, 1984b Valvulineria lymani_(Yokoyama R Figure 6. Paleobathymetric distribution of benthic foraminifera. Data of Asano (1952), Ujiié and Watanabe (1960) and Kaiho (1984a, b) are also interpreted by the present study. R = Rare; C = Common; A = Abundant. Occurrences of species shown in boldface are supposed to be important for paleobathymetric interpretations. Occurrences of species with * are restricted in the Utsunai Formation (Kaiho, 1984b), and with ** to the Omagari Formation (Asano, 1952; Kaiho, 1984b). zones (B-C and H-I) and foraminiferal assemblage zones Bulimina schwageri and Angulogerina hannai (Kaiho, indicated by Kaiho (1984a; Figure 5), it is obvious that 1984a, c) as well as numerous calcareous foraminifera such foraminiferal assemblage zones F5 and F7 (Kaiho, 1984a, as Gyroidina yokoyamai and Plectofrondicularia packar- c) were deposited in the upper bathyal zone. The di. These latter two species were not encountered in the foraminiferal assemblages of these zones contain abundant Yufutsu-Umaoi district and therefore must represent the Eocene shallow marine foraminifera 157 Eocene upper bathyal zone. Paleobathymetric distributions of benthic foraminifera in the Poronai Sea are summarized in Figure 6 based on the present study and compilation of previous reports (Asano, 1952; Ujiié and Watanabe, 1960; Kaiho, 1984a, b). Paleoenvironmental implications of abundant aggluti- nated foraminifera The paleobathymetric distributions of benthic foramini- fera in the study area indicate that the shallower marine as- semblages include higher abundances of agglutinated foraminifera. Because similar assemblages dominated by agglutinated foraminifera have not been reported from other coastal regions of the North Pacific while various cal- careous species have been reported (e.g. Ingle, 1980; McDougall, 1980), a local environmental factor is consid- ered to have controlled the distribution. Greiner (1970) proposed that availability of calcium car- bonate for test construction is the controlling environmental factor in the distribution of calcareous foraminifera. In en- vironments where calcium carbonate availability is insuffi- cient for calcareous foraminifera, agglutinated foraminifera dominate. Examples of environments with insufficient calcium carbonate are found in brackish coastal areas, estu- aries, and marshes (e.g., Zalesny, 1959; Bandy and Arnal, 1960; Anderson, 1963; Scott et al., 1983; Zheng and Fu, 1992). Highly diverse agglutinated foraminiferal associa- tions are also reported from the Arctic Ocean, in areas af- fected by the brackish surface water (Vilks, 1969; Hunt and Corliss, 1993; Schröder-Adams et al., 1990). Based on these modern examples of foraminiferal ecol- ogy, abundant occurrences of agglutinated foraminifera from the Ishikari Group and the Poronai Formation are thought to be the result of deposition in areas under the in- fluence of brackish surface-water. Water stratification Previous studies on the lithostratigraphy and dinoflagellate assemblages showed that water stratification was important in the basal part of the Poronai Formation (Matsuno et al., 1964; Kurita and Matsuoka, 1994). Previ- ous studies also supposed that the Poronai Formation was deposited in an embayment called the “Poronai Sea” (Teshima, 1967; = “Paleo-Poronai Sea” of Kaiho, 1983, 1984c). This interpretation is mainly based on the geo- graphical distribution of the Poronai Formation and its equivalents (Figure 1A). Absence or rare occurrences of planktonic foraminifera and radiolarians in the Yufutsu- Umaoi district indirectly support this interpretation. Such closed paleogeography may be an important factor for the water stratification. According to Kaiho (1984a, b), Teshima (1955)’s megafossil zone A, found in the basal part of the Poronai Formation, corresponds approximately to the foraminiferal zones from the Haplophragmoides tanaii-Haplophra- gmoides subevolutus Assemblage Zone to the Haplophra- gmoides umbilicatus-H. subevolutus Assemblage Zone of Kaiho (1984a, c; Figure 5). Accounting for the synony- mies discussed in the taxonomic section below, species composition of Kaiho’s zones is similar to the Evolutinella subamakusaensis-Haplophragmoides crassiformis Assem- blage Zone and the Globocassidulina globosa-Cribroel- phidium sorachiense Assemblage Zone of the Yufutsu- Umaoi district. This similarity shows that the stratigraphic interval from the H. tanaii-H. subevolutus Assemblage Zone to the H. umbilicatus-H. subevolutus Assemblage Zone in the Yubari district was deposited under paleobathymetric conditions within, or shallower than, the middle sublittoral zone of the Yufutsu-Umaoi district. Matsuno ef al. (1964) also pointed out that the megafossil zone A defined by Teshima (1955), at the basal part of the Poronai Formation in the Yubari coal field, is rich in organic carbon and presumably was deposited in an oxygen-depleted paleoenvironment. Based on these lines of evidence, sediments deposited in stratified shallow marine water masses are widely distrib- uted in the Poronai Formation of the Yufutsu-Umaoi dis- trict and the Yubari district. These stratified water masses are believed to have formed as a result of fresh water input, as suggested by the dominant agglutinated foraminifers. In such an environment, a decreasing supply of dissolved oxygen from the sea surface may have caused oxygen de- pletion in substratum due to degradation of organic matter, as commonly observed in modern shallow marine areas (Tyson and Pearson, 1991). Conclusion Three Eocene foraminiferal assemblage zones, Evoluti- nella subamakusaensis-Haplophragmoides crassiformis Assemblage Zone, Globocassidulina globosa-Cribroel- phidium sorachiense Assemblage Zone and Bulimina schwageri-Angulogerina hannai Assemblage Zone, in as- cending order, were defined in the well sections of the Yufutsu-Umaoi district, southern central Hokkaido. Assemblages characterizing each assemblage zone indicate the littoral to inner sublittoral zone, the middle sublittoral zone and the outer sublittoral zone, respectively. Furthermore, compositions of foraminiferal assemblages of the Eocene upper bathyal zone were described based on a reevaluation of the previous studies. The upper bathyal zone is characterized by occurrence of abundant calcareous species such as Gyroidina yokoyamai and Plectofrondi- cularia packardii. Abundant occurrences of agglutinated foraminifera sug- gest brackish-water paleoenvironments caused by fresh- a — Ss a Ss = Ss x= = 2) © +— 3 n Eocene shallow marine foraminifera 159 water input. Such brackish water may cause stratification and resultant oxygen depletion. As a result of the present study, compositions of Eocene shallow marine foraminiferal assemblages in northern Japan were revealed. These data are expected to form a basis for considering the geohistory of the Paleogene for- mations in Hokkaido, as well as the paleoceanography of the northwestern Pacific region during the Eocene. Acknowledgments Kristin McDougall (U. S. Geological Survey) kindly im- proved the manuscript and gave me suggestions. I would like to thank Yokichi Takayanagi (Tohoku University) and Hiroshi Kurita (JAPEX, presently Niigata University) for critical reading of the manuscript. I also would like to express my special thanks to Michiko Miwa (JAPEX) and Tetsuro Ichinoseki (JAPEX) for fruitful sug- gestions, and Keiko Inaba and Yoko Kuwashima for tech- nical assistance. This study is published with permission of Japan Petroleum Exploration Co., Ltd. and Japan National Oil Corporation. Taxonomic notes Species which occurred in the Yufutsu-Umaoi district are arranged in taxonomic order following Loeblich and Tappan (1987). For the present identification, topotype, ideotype and hypotype specimens collected by K. Kaiho and presently deposited in JAPEX Research Center, Chiba, Japan, were compared. Because of poor preservation of the specimens, no new species were described herein, al- though several synonymies are discussed. All figured specimens are deposited in the collection of JAPEX Research Center. Bathysiphon eocenica Cushman and Hanna (Figure 7.1) Bathysiphon eocenica Cushman and Hanna, 1927, p. 210. pl. 13, figs. 2, 3. —Asano, 1952, p. 31, pl. 3, figs. 3, 4. —Ujiié and Watanabe, 1960, p. 127, pl. 1, figs. 3, 4. —Fukuta, 1962, p.7, pl. 1, fig. 1. —Kaiho, 1984b, p. 42, pl. 1, figs. 3a, b. —Kaiho, 1992b, p. 365, pl. 1, fig. 1, pl. 5, fig. 1, 2. Bathysiphon vernoni Hamlin (Figure 7.2) Bathysiphon vernoni Hamlin, 1963, p. 153, pl. 14, figs. la-2b. —Kaiho, 1984b, p. 42, pl. 1, fig. 4. Placentammina sp. A (Figure 7.5, 7.6) Description. — Test free, small, unilocular, pyriform; very finely agglutinated and almost transparent; aperture round opening at the top of pyriform shell with very short projection. Remarks.— Almost all of the specimens were deformed secondarily. Reophax tappuensis Asano (Figure 7.7) Reophax tappuensis Asano, 1958, p. 71, pl. 13, figs. 8, 9. —Kaiho, 1984b, pl. 1, figs. 10a-12. Cribrostomoides sp. cf. C. cretacea Cushman and Goudkoff (Figure 7.11, 7.12) Cf. Cribrostomoides cretacea Cushman and Goudkoff, 1944, p. 54, pl. 9, figs. 4a, b. Remarks.— All specimens are so distorted that accurate identification is difficult. Coiling planes are always tilted to show very weak streptospiral involute coiling, therefore this form must be assigned to genus Cribrostomoides fol- lowing Jones et al. (1993). It is distinguishable from allied species in its involute coiling, six to eight inflated chambers in final whorl, finely agglutinated and slightly transparent wall. Evolutinella subamakusaensis (Fukuta) (Figure 8.10-8.12) Cribrostomoides cf. cretacea Cushman and Goudkoff. — Ujiie and Watanabe, 1960, p. 127, pl. 1, figs. 3-5. Haplophragmoides subamakusaensis Fukuta, 1962, p. 9, fig. 2, pl. 1, figs. 6-10. Haplophragmoides subevolutus Kaiho, 1984a, p.114, pl. 7, figs. 7a, b. —Kaiho, 1992c, pl. I, figs. 8a, b. Cribrostomoides sp. A. Yasuda, 1986, p. 51, pl. 3, figs. 9a, b. Description. — Test free, planispirally enrolled, fre- quently coiling plane is unstable and sometimes show streptospiral appearance, slightly to completely evolute; « Figure 7. Foraminifera from the Poronai Formation and Ishikari Group appearing in the wells studied. Scale bars equal 100 um except figs. 1, 2, 4, 7,8, 11, 12, 13, and 14, where bars equal 500 um. 1. Bathysiphon eocenica Cushman and Hanna, from MITI Umaoi, 3840 m. 2. Bathysiphon vernoni Hamlin, from Kita-Akebono SK-1D, 3580 m. 3. Ammodiscus sp., from Numanohata SK-4D, 3600 m. 4a, b. Glomospira sp., from Numano- hata SK-4D, 3305 m. 5a, b. Placentammina sp. A, from Kita-Akebono SK-ID, 3330 m. 6. Placentammina sp. A, from Kita-Akebono SK-1D, 3310 m. 7. Reophax tappuensis Asano, from Kita-Akebono SK-1D, 3320 m. 8a-c. Budashevaella sp. aff. B. multicamerata (Voloshinova), from MITI Umaoi, 4000 m. 9a-c. Budashevaella symmetrica (Ujiié and Watanabe), from Numanohata SK-4D, 3240 m. 10a, b. Budashevaella symmetrica (Ujiié and Watanabe), from MITI Umaoi, 3720 m. 11a, b. Cribrostomoides sp. cf. C..cretacea Cushman and Goudkoff, from Numano- hata SK-4D, 3340 m. 12a, b. Cribrostomoides sp. cf. C. cretacea Cushman and Goudkoff, from Kita-Akebono SK-1D, 3250 m. 13a, b. Haplo- phragmoides crassiformis Kaiho, from Numanohata SK-4D, 3660 m. Specimen bilaterally compressed by secondary deformation. 14a, b. Haplo- phragmoides crassiformis Kaiho, from Kita-Akebono SK-1D, 3640 m. Satoshi Hanagata Eocene shallow marine foraminifera 161 biumbilicate; chambers inflated, 7-12 in final whorl; wall thin, finely agglutinated, exterior smoothly finished; aper- ture interiomarginal. Remarks. — This species is assigned to the genus Evolutinella because of its evolute planispiral coiling. It is also characterized by numerous chambers and finely agglu- tinated wall. Ujiie and Watanabe (1960) first reported this species from the Poronai Formation as Cribrostomoides cf. cretacea Cushman and Goudkoff. Subsequently, Fukuta (1962) included the form in the synonymy of his Haplophragmoides subamakusaensis described from the Kyoragi Formation of the Amakusa Islands, Kyushu, and noted that this species was found also from the Poronai, Akabira and Wakkanabe Formations of the Ishikari Coal field. Later, Kaiho (1984a) described A. subevolutus from the Poronai Formation and synonymized C. cf. cretacea of Ujiié and Watanabe (1960) without reference to the study of Fukuta (1962). A. subamakusaensis and H. subevolutus have quite similar morphology and are regarded here as synonyms. Kaiho and Nishi (1989) reported A. subevolutus from the Middle Eocene to Early Oligocene Hyuga Group in southern Kyushu without any figures. Thus it is obvious that E. subamakusaensis has a broad geographic distribution from Hokkaido to Kyushu, and a long stratigraphic range from the Maastrichtian to lower Oligocene. Kaiho (1984a) included the specimens having numerous chambers, up to 14, in the final whorl in H. subevolutus. However, I did not find specimens having more than 13 chambers in the present study. In Figures 8-12, specimens collected from the Kyoragi Formation (not topotypes but collected from near the type locality) are shown for comparison. Haplophragmoides crassiformis Kaiho (Figure 7.13, 7.14) Haplophragmoides cf. emaciata (Brady). —Ujiié and Watanabe, 1960, p. 127, pl. 1, figs. 6a, b. Haplophragmoides crassiformis Kaiho, 1984a, p. 114, pl. 7, figs. 3a, b. Haplophragmoides rugosus soyaensis Yasuda (Figure 8.3, 8.4) Haplophragmoides rugosus soyaensis Yasuda, 1986, p. 50, pl. 5, figs. 5a-7c. Haplophragmoides umbilicatus Kaiho, 1984a, p. 115, pl. 7, figs. 6a, b. (non Haplophragmoides umbilicatus Pearcey). Haplophragmoides apertiumbilicatus Kaiho, 1986, nom. nov. Remarks.—This species is characterized by its deeply depressed umbilicus, seven inflated chambers in the final whorl, and compact arrangement of chambers. Distinguished from H. amakusaensis Asano in possessing curved sutures. Haplophragmoides tanaii Kaiho (Figure 8.5) Haplophragmoides tanaii Kaiho, 1984a, p. 115, pl. 7, figs. Sa, b. Remarks.—This species is characterized by its small test size, coarsely agglutinated wall, and subacute periphery. H. kushiroensis Asano (1962) described from the Paleogene of eastern Hokkaido has similar morphology in its test size, number of chambers, acute periphery and coarsely agglutinated wall but is supposed to be distin- guished by possessing curved sutures. Haplophragmoides yokoyamai Kaiho (Figure 8.1, 8.2) Haplophragmoides kirki Wickenden; Mallory, 1959, p. 112, pl. 2, figs. 8a, b. —Takayanagi, 1960, p. 72, pl. 2, figs. 3a, b. Haplophragmoides yokoyamai Kaiho, 1984a, p.116, pl. 7, figs. 4a, b. Remarks.—Mallory (1959) first reported this species as H. kirki from the Eocene of California. Takayanagi (1960) also reported this species from the Albian to Campanian of Hokkaido as A. kirki. Later Kaiho (1984a) described A. yokoyamai from the Poronai Formation as new. The holotype of A. kirki from the Cretaceous of North America (Wickenden, 1932, p.85, pl. 1, fig. 1) shows a smaller test, broadly rounded periphery and more finely agglutinated wall compared to H. yokoyamai. Furthermore, specimens of Mallory (1959) and Takayanagi (1960) have a compressed test, larger test size and a coarser wall than typical H. kirki. Moreover, H. kirki is synonymized to H. excavata Cushman and Walters by Mello (1971), who added that H. excavatus shows such a wide range of morphological varia- tion that H. kirki falls within the range of variation of the + Figure 8. Figure 12a, b were collected from the Kyoragi Formation. um. la, b. Haplophragmoides yokoyamai Kaiho, from MITI Umaoi, 3840m. 3a, b. Haplophragmoides rugosus soyaensis Yasuda, from MITI Umaoi, 4160 m. Kaiho, from MITI Umaoi, 3840 m. Largest-size specimen. Foraminifera from the Poronai Formation and Ishikari Group appearing in the wells studied. Specimens shown for comparison in Scale bars equal 100 um except figs. 2, 6, 9, 10, 11, 12, and 13, where bars equal 500 Medium-sized specimen. 2a, b. Haplophragmoides yokoyamai 4a, b. Haplophragmoides rugosus soyaensis Yasuda, from MITI Umaoi, 4160 m. 5a, b. Haplophragmoides tanaii Kaiho, from MITI Umaoi, 4000 m. 6a, b. Haplophragmoides sp. A, from Numanohata SK-4D, 3110 m. Haplophragmoides sp. B, from Kita-Akebono SK-1D, 3350 m. 9a, b. Haplophragmoides sp. D, from MITI Umaoi, 3820 m. subamakusaensis (Fukuta), from Numanohata SK-4D, 3600 m. Specimen bilaterally compressed by secondary deformation. subamakusaensis (Fukuta), from Numanohata SK-4D, 3600 m. Specimen vertically compressed by secondary deformation. Specimen vertically compressed by secondary deformation. 14-16. Recurvoidella sp. cf. R. lamella (Grzybowski), all specimens from Numanohata SK-4D, 3500 m. subamakusaensis (Fukuta), from the Kyoragi Formation. from MITI Umaoi, 3920 m. 7a, b. Haplophragmoides sp. B, from MITI Umaoi, 4060 m. 8a, b. 10a, b. Evolutinella Ila, b. Evolutinella 12a, b. Evolutinella 13a, b. Recurvoides sp. A, S = S op S = S a0) = a © g S Dn Eocene shallow marine foraminifera 163 former species. Recurvoidella sp. cf. R. lamella (Grzybowski) (Figure 8.14-8.16) Cf. Trochammina lamella Grzybowski, 1898, p. 290, pl. I1, fig. 25. Cf. Recurvoidella lamella (Grzybowski). —Charnock and Jones, 1990, p. 173, pl. 6, figs. 11, 12, pl. 17, fig. 7; Kaminski and Geroch, 1993, p. 263-264, pl. 10, figs. 8, 9. Remarks.—Most specimens are depressed almost com- pletely. Budashevaella symmetrica (Ujiié and Watanabe) (Figure 7.9, 7.10) Trochammina symmetrica Ujiié and Watanabe, 1960, p. 134, pl. 1, figs. 10, 11. Description.—Test free, medium, early stage compactly streptospiral; the angle between one coiling plane and sub- sequent one increases as growth proceeds, up to 90° in an adult form, the last whorl and half of the penultimate whorl are visible on the surface in a juvenile form, but the penul- timate one becomes almost invisible in the adult, few chambers of penultimate whorl exposed in umbilical area; slightly evolute; chambers not inflated in earlier coil, become slightly inflated, seven to eight in final whorl, in- creasing slowly in size as added; sutures radial, slightly de- pressed, limbate; wall finely agglutinated, thick; aperture interiomarginal. Remarks.—The streptospiral coiling of this species con- firms the assignment to the genus Budashevaella. This species is similar to Haplophragmoides subamakusaensis Fukuta in general appearance but is distinguished by its less inflated chambers, less depressed sutures and streptospiral coiling. It is also distinguished from Budashevaella sp. aff. B. multicamerata of the present study in having fewer number of chambers in the final whorl. Budashevaella sp. aff. B. multicamerata (Voloshinova) (Figure 7.8) Aff. Circus multicameratus Voloshinova, in Voloshinova and Budasheva, 1961, p. 201, pl. 7, fig. 6, pl. 8, fig. 1. Budashevaella multicamerata (Voloshinova). — McDougall, 1980, p. 34, pl.3, figs. 4-6. Diagnosis. — Numerous chambers up to 14 in final whorl. Coiling plane of the last coil lies at about a right angle to that of the penultimate one in the umbilical area. Remarks. — This form is distinguished from B. multicamerata (Voloshinova), originally described as Circus multicameratus from the Neogene of Sakhalin, in its broadly rounded periphery. Reticulophragmium amakusaensis (Fukuta) (Figure 9.9) Cyclammina amakusaensis Fukuta, 1962, p.12, text-figs, 3a-b, pl. 3, figs. 8-10. Description.— Test free, medium, planispirally coiled and involute to very slightly evolute, 10-13 chambers in final whorl, whorls increasing rapidly in height; wall finely agglutinated; sutures depressed, straight and radial; slightly biumbilicate; aperture an interiomarginal equatorial slit. Remarks. This species was originally described from the Kyoragi Formation of the Amakusa Islands, Kyushu, as a species of Cyclammina. Because of the position of the ap- erture and reticulate wall, it is newly assigned to the current genus. Thin section showing a wide cavity in each cham- ber indicates that development of alveolar structure is quite weak (Figure 9.9c). It commonly occurred in the study sections, although it has never been recorded from the Poronai Formation in surface sections. It is highly possi- ble that the present species has been assigned to other Cyclammina species by previous workers. Cyclammina ezoensis Asano (Figure 9.3) Cyclammina ezoensis Asano, 1951a, pl. 1, figs. la, b. —Asano, 1951b, p. 20, pl. 3, figs. 2a, b. —Ujiié and Watanabe, 1960, pl. 1, fig. 7. —Kaiho, 1984b, p. 45, 46, pl. 1, figs. 21a, b. —Kaiho, 1992b, p. 367, 368, pl. 1, figs. 5a, b. Remarks. —This species is characterized by a com- pressed test with thin periphery. It was originally de- scribed from the Miocene Masuporo Formation in Hokkaido, and was commonly recovered from the Paleogene as well as Neogene formations of Japan. Neogene specimens sometimes attain much larger diame- @ Figure 9. Foraminifera from the Poronai Formation and the Ishikari Group appearing in the wells studied. figs. 1, 3, 4, 5, 7, 8, 10, 11, 12, and 13, where bars equal 500 um. 1. Ammobaculites sp., from Kita-Akebono SK-1D, 3430 m. Scale bars equal 100 um except 2a-c. Alveolophragmium sp. A, from MITI Umaoi, 3860 m. 3a-c. Cyclammina ezoensis Asano, from MITI Umaoi, 4410 m. 4a, b. Cyclammina pacifica Beck, from Kita-Akebono SK-ID, 3075 m. pusilla Brady, from Kita-Akebono SK-1D, 3260 m. 5. Cyclammina pacifica Beck, from Numanohata SK-4D, 3220 m. 6a, b. Cyclammina sp. aff. C. 7a-c. Cyclammina sp., from Numanohata SK-4D, 3240 m. Note that this specimen has 15 chambers in the final whorl. 8a-c. Cyclammina sp., from Numanohata SK-4D, 3760 m. Note that this specimen has 15 chambers and a bilaterally compressed test. 9a-c. Reticulophragmium amakusaensis (Fukuta), from MITI Umaoi, 3740 m. 10. “Clavulina” sp. from MITI Umaoi, 4060 m. 11a, b. Fragment of last chamber of “Clavulina” -like species, from MITI Umaoi, 4060 m. Note the characteristic large cone-shaped last chamber. 12a-c. Poronaia poronaiensis (Asano), from Numanohata SK-4D, 3240 m. 3210 m. 13a, b. Poronaia poronaiensis (Asano), from Kita-Akebono SK- ID, Satoshi Hanagata Eocene shallow marine foraminifera 165 ters, as much as 4 mm, but commonly have fewer chambers in comparison with the Paleogene specimens. Cyclammina pacifica Beck (Figure 9.4, 9.5) Cyclammina pacifica Beck, 1943, pl. 98, figs.2, 3. —Asano, 1952, p. 33, pl. 3, figs. la, b, 2, pl. 5, figs. 11a, b. —Asano, 1958, pl. 13, fig. 3. —Kaiho, 1992b, p. 368, pl. 1, figs. 6a, b. Cyclammina cf. pacifica Beck. —Asano, 195 la, p.7, figs. 24, 25. —Asano, 1951b, p. 20-21, pl. 3, figs. 5a, b. —Fukuta, 1962, p. 11, pl. 3, figs. 1-3. —Kaiho, 1984b, p.46, pl.2, figs. la, b. Remarks.—This species has been commonly recorded from various Neogene and Paleogene formations through- out Japan. It shows compact arrangement of chambers. Although alveolar structure is rather poorly developed in the figured specimen (Figure 9.5), degree of development of alveolar structure varies among specimens. Cyclammina sp. aff. C. pusilla Brady (Figure 9.6) Aff. Cyclammina pusilla Brady, 1881, p. 53; Type figures: Brady, 1884, pl. 37, figs. 20-23. Cyclammina pusilla Brady. —Kaiho, 1984b, p. 46, pl. 2, figs. 2a, b. Remarks.—Specimens from the Poronai Formation have a smaller test size and subacute periphery, and are therefore distinguished from C. pusilla. Poronaia poronaiensis (Asano) (Figure 9.12, 9.13) Plectina poronaiensis Asano, 1952, p. 33, 34, pl. 4, figs. 12, 13. —Asano, 1958, pl. 13, figs. 5-7. —Fukuta, 1962, p.16, pl. 5, figs. 4, 5. Poronaia poronaiensis (Asano). —Ujiié and Watanabe, 1960, p. 133, 134, pl. 2, figs. 1-8. Plectotrochammina poronaiensis (Asano). — Loeblich and Tappan, 1964, p.279. —Kaiho, 1984b, p. 48, pl.2, figs. 10a-d. Description.—Test free, short and broadly cylindrical, lower trochospiral in the early stage with four chambers, later biserial, each chambers imbricating to penultimate chambers; chambers inflated; wall finely agglutinated but occasionally includes coarse grains, internally imperfect al- veolar structure developed; aperture, interiomarginal open- ing. Remarks.—Specimens were occasionally deformed con- siderably. Loeblich and Tappan (1964) regarded the genus Poronaia as a junior synonym of Plectotrochammina, and later assigned both genera to their list of “Genera of Uncertain Status” (Loeblich and Tappan, 1987). However, Poronaia should be included in the family Textulariellidae because of possessing alveoli-like labyrinthic structure in- side the test, while both Plectina and Plectotrochammina have a simple wall. Trochammina sp. cf. T. asagaiensis Asano (Figure 10.1) Cf. Trochammina asagaiensis Asano, 1949, p. 475, text-figs. 2a-4b. Trochammina asagaiensis Asano. —Kaiho, 1984b, p. 47, pl. 2, figs. 5a-6b. Remarks.—This species is characterized by its very low trochospiral and compressed test. However, specimens examined in this study and the specimens of Kaiho (1984b) show low trochospiral, obscure earlier whorls and inflated chambers compared to T. asagaiensis. Quinqueloculina seminula compacta Serova (Figure 10.2) Quinqueloculina seminulum (Linné) var. compacta Serova, 1960, pl. 3, figs. 7a-c. Quinqueloculina weaveri Rau. —McDougall, 1980, p. 37, pl. 5, figs. 5-7. Quinqueloculina cf. seminula compacta Serova. —Kaiho, 1984b, p. 49, pl. 2, figs. 12a-c. Dentalina sp. cf. D. subsoluta (Cushman) (Figure 10.7) Cf. Nodosaria subsoluta Cushman, 1923, p. 74, pl. 13, fig. 1. Dentalina cf. subsoluta (Cushman). —Kaiho, 1984b, p. 50-51, pl. 3, fig. 3. —Kaiho, 1992b, p. 373-374, pl. 1, fig. 14. @ Figure 10. 1, 4, 5, 7a, 12, and 18, where bars equal 500 um. Foraminifera from the Poronai Formation and Ishikari Group appearing in the wells studied. Scale bars equal 100 um except figs. la, b. Trochammina sp. cf. T. asagaiensis Asano, from Numanohata SK-4D, 3220 m. 2. Quinqueloculina seminula compacta Serova, from Numanohata SK-4D, 3260 m. 3a, b. Guttulina takayanagii Kaiho, from Numanohata SK-4D, 3460 m. 4. Pseudopolymorphina sp. A, from Numanohata SK-4D, 3285m. 5. Pseudonodosaria sp. cf. P. conica (Neugeboren), from Numanohata SK-4D, 3305 m. 6a, b. Sigmoidella pacifica (Cushman and Ozawa), from Numanohata SK-4D, 3400 m. 7a, b. Dentalina sp. cf. D. subsoluta (Cushman), from Kita-Akebono SK-ID, 3360 m. 8a, b. Lenticulina sp., from Kita-Akebono SK-ID, 3600 m. 9a, b. Fissurina sp. cf. F. marginata (Montagu), from Kita-Akebono SK-1D, 3420 m. 10a, b. Lagena striata (d’Orbigny), from MITI Umaoi, 3940 m. sp. cf. P. gracilima (Seguenza), from Kita-Akebono SK-1D, 3190 m. 12a, b. Glandulina laevigata ovata Cushman and Applin, from Numanohata SK-4D, 3120 m. 13a, b. Globocassidulina globosa (Hantken), from Numanohata SK-4D, 3240 m. 14a, b. Globocassidulina globosa (Hantken), from Numanohata SK-4D, 3120 m. 15a, b. Bulimina schwageri Yokoyama, from Numanohata SK-4D, 3120 m. Yokoyama (juvenile form), from Kita-Akebono SK-ID, 3120 m. pyrula (d’Orbigny), from Numanohata SK-3D, 3720 m. hannai Beck, from MITI Umaoi, 3700 m. 11. Procerolagena 16a, b. Bulimina schwageri 17. Globobulimina sp., from MITI Umaoi, 4120 m. 18. Praeglobobulimina 19a, b. Angulogerina hannai Beck, from MITI Umaoi, 3700 m. 20a, b. Angulogerina Satoshi Hanagata Eocene shallow marine foraminifera 167 Pseudonodosaria sp. cf. P. conica (Neugeboren) (Figure 10.5) Cf. Pseudonodosaria conica (Neugeboren). —McDougall, 1980, p. 36, pl. 9, figs. 7, 8. —Kaiho, 1992b, p. 374, figs. 17a, b. Cf. Pseudoglandulina obtusissima (Reuss). —Yoshida, 1957, p. 64, text-figs. 3-9. Cf. Pseudonodosaria shitakaraensis Kaiho, 1984a, p. 118, pl. 8, figs. la, b. Lagena striata (d’Orbigny) (Figure 10.10) Oolina striata d’Orbigny, 1839, p.21, pl. 5, fig.12. Lagena becki Sullivan. —McDougall, 1980, p. 35, pl. 7, figs. 1, 4. Lagena striata (d’Orbigny). —Kaiho, 1984b, p. 51, 52, pl. 3, figs. 13a, b. —Kaiho, 1992b, p. 377, pl. 2, fig. 7. Lagena sp. cf. L. laevis (Montagu) Cf. Vermiculum laeve Montagu, 1803, p. 524; Type figure: Walker and Boys, 1784,pl. 1, fig. 9, as Serpula (Lagena) laevis ovalis. Lagena laevis (Montagu). —Kaiho, 1984b, p. 51, pl. 3, figs. 11- 13. Remarks.—Specimens of this study have similar features to those of Kaiho (1984b), but are distinguished from the Recent L. laevis in its shorter test. Procerolagena sp. cf. P. gracillima (Seguenza) (Figure 10.11) Cf. Amphorina gracillima Seguenza, 1862, p. 51, pl. 1, fig. 37. Lagena gracillima (Seguenza). —Kaiho, 1984b, p. 51, pl. 3, figs. 10a, b. Cf. Procerolagena gracillima (Seguenza). —Jones, 1994, p. 62, figs. 19-22, 24-29. Remarks.—This species is quite similar to L. gracillima of Kaiho (1984b), but different from the Recent P. gracillima in its shorter test. Guttulina takayanagii Kaiho (Figure 10.3) Guttulina takayanagii Kaiho, 1984a, p. 120, pl. 8, figs. 5a-d. Pseudopolymorphina hokkaidoana Kaiho Pseudopolymorphina hokkaidoana Kaiho, 1984a, p. 120, figs. 8a-c. Sigmoidella pacifica (Cushman and Ozawa) (Figure 10.6) Guttulina (Sigmoidina) pacifica Cushman and Ozawa, 1928, p. 19, pl. 2, fig. 13. Guttulina cf. pacifica Cushman and Ozawa. —Fukuta, 1962, p. 23, pl. 7, figs. 9-10. Sigmoidella pacifica Cushman and Ozawa. —Kaiho, 1984b, p. 58, fig. 53, pl. 4, figs. 12a-d. Remarks.—This species is known from the Eocene for- mations from Kyushu to Hokkaido. It is common in the shallow marine facies in the lower part of the Poronai Formation, as discussed earlier. Since S. pacifica is also known from Recent shallow marine environments, it ap- pears not to have changed habitat from the Eocene until the Recent. Although Jones (1994) regarded this species as a junior synonym of Polymorphina elegantissima Parker and Jones, I think these two species are distinguishable in the aspect of number of chambers visible from the the outside of the test. Fissurina sp. cf. F. marginata (Montagu) (Figure 10.9) Cf. Vermiculum marginatum Montagu, 1803, p. 524; Type figure: Walker and Boys, 1784, pl. 1, fig. 7. Cf. Fissurina marginata (Montagu). —Loeblich and Tappan, 1953, p. 77, pl. 14, figs. 6-9. Glandulina laevigata ovata Cushman and Applin (Figure 10.12) Nodosaria (Glandulina) laevigata d’Orbigny var. ovata Cushman and Applin, 1926, p. 443, pl. 7, figs. 12, 13. Glandulina laevigata ovata Cushman and Applin. —Ujiié and Watanabe, 1960, p. 129, 130, pl. 2, figs. 11, 12. —Kaiho, 1984b, pl.4, figs. 15a-c. Globocassidulina globosa (Hantken) (Figure 10.13, 10.14) Cassidulina globosa Hantken, 1875, p. 64, pl. 16, fig. 2. Globocassidulina globosa (Hantken). —Kaiho, 1992b, p. 378, pl. 2, figs. 11a, b, pl. 5, figs. 17a, b. Bulimina schwageri Yokoyama (Figure 10.15, 10.16) Bulimina schwageri Yokoyama, 1890, p. 190, pl. 24, figs. 6-8. —Ujiié and Watanabe, 1960, pl. 2, figs. 16, 17, 18. —Kaiho, 1984b, p. 62-63, pl. 5, figs. 11-15. —Kaiho, 1992b, p. 379, pl. 3, figs. 2a, b. Caucasina schwageri (Yokoyama). —Serova, 1976, p. 324, 325, pl. 1, figs. 6a-c. @ Figure 11. Foraminifera from the Poronai Formation and Ishikari Group appearing in the wells studied. Scale bars equal 100 um except fig. la-c. Heterolepa poronaiensis Kaiho, from Kita-Akebono SK-1D, 3340 m. 2a-d. Cibicides elmaensis Rau, from 10 where bar equals 500 um. Numanohata SK-3D, 3720 m. 3a-c. Cibicides sp. A, from Kita-Akebono SK-1D, 3540 m. 4a, b. Nonionella japonica (Yokoyama), from MITI Umaoi, 4000 m. Numanohata SK-4D, 3260 m. 5a, b. Melonis affinis (Reuss), from Numanohata SK-4D, 3340 m. 7a, b. Pullenia eocenica Cushman and Siegfus, from MITI Umaoi, 3980 m. K. C. Stewart, from Numanohata SK-4D, 3240 m. 9a, b. Cribroelphidium sorachiense (Asano), from Numanohata SK-3D, 3720 m. broelphidium ishikariense (Kaiho), from Numanohata SK-3D, 3800 m. 6a, b. Melonis pompilioides (Fichtel and Moll), from 8a, b. Pullenia salisburyi R. E. and 10a, b. Cri- 168 Satoshi Hanagata Figure 12. Cribroelphidium wakkanabense (Kaiho), from Numanohata SK-4D, 3240 m. 2a, b. Cribroelphidium wakkanabense (Kaiho), from Numanohata SK-3D, 3700 m. 3a, b. Cribroelphidium sp. from Kita-Akebono SK-1D, 3410 m. Note that this specimen shows subacute periphery. from MITI Umaoi, 4120 m. 5a-c. Subbotina sp., from Kita-Akebono SK-ID, 3440 m. Planktonic foraminifera genus and species indeterminable. Remarks. — This species has been recorded from Hokkaido to Kamchatka. As discussed by Kaiho (1984b), B. schwageri has three to four chambers in the first whorl, and is distinguished from the species of Caucasina which always have four chambers in the final whorl. Even if there is a phylogenetic relationship between B. schwageri and Caucasina species as pointed out by Serova (1976), emendation by reexamination of the type species of the genus Caucasina is necessary. Praeglobobulimina pyrula (d’Orbigny) (Figure 10.18) Bulimina pyrula d’Orbigny, 1846, p. 184, pl. 11, figs. 9, 10. —Asano, 1952, p. 41, figs. 10a, b. —Kaiho, 1984b, p. 62, pl. 5, figs. 10a-c. Praeglobobulimina sp. cf. P. ovata (d’Orbigny) Cf. Bulimina ovata d’Orbigny, 1846, p. 185, pl. I1, figs. 13, 14. Praeglobobulimina ovata (d’Orbigny). —Kaiho, 1984b, pl. 6, fig. 2. —Kaiho, 1992b, pl. 3, fig. 5. Angulogerina hannai Beck (Figure 10.19, 10.20) Angulogerina hannai Beck, 1943, p. 607, pl. 108, figs. 26, 28. Trifarina cushmani Todd and Knifer, 1952, p. 23, pl. 4, figs. 6a, b. Trifarina maiyai Kaiho, 1984a, p. 122, 123, pl. 9, figs. 7a, b. Foraminifera from the Poronai Formation and Ishikari Group appearing in the wells studied. Scale bars equal 100 um. 1a, b. 4a, b. Trifarina hannai (Beck). —Kaiho, 1992b, p. 380, pl. 3, figs. Ta, b. Remarks. — Relationship between T. maiyai and T. hannai follows the study of Kaiho (1992b). T. cushmani was originally reported from the Eocene in Chile and also reported from the Poronai Formation by Maiya (1979). Although Maiya (1979) did not figure any specimens, ob- servation of his specimens by the present author revealed that they are conspecific with A. hannai. I regard T. cushmani as a junior synonym of A. hannai because of their similarity in morphology, such as test size and subacute pe- riphery, on the basis of the original illustration by Todd and Knifer (1952). Cibicides elmaensis Rau (Figure 11.2) Cibicides elmaensis Rau, 1948, p. 173, pl. 31, figs. 18 - 26. — Fukuta, 1962, p. 25, pl. 8, figs. 3a, b, 7a, b. Cibicides biconbexus Kaiho, 1984a, p. 124, pl. 9, figs. 7a-c. ?Cibicides yabei Asano, 1952, p. 43, pl. 4, figs. la-c. Remarks.—Cibicides yabei Asano (1952) was described from the basal part of the Poronai Formation, but was not recorded by Kaiho (1984a, b) who studied the same forma- tion in the same area. As discussed by Asano (1952), C. Eocene shallow marine foraminifera 169 yabei is distinguished from C. elmaensis in lacking shell material filling the umbilical area, but I think that this is in- sufficient to separate C. yabei as a different species. Nonionella japonica (Yokoyama) (Figure 11.4) Pilvulineria japonica Yokoyama, 1890, p. 192, pl. 24, figs. 15 a-c. Nonionella japonica (Yokoyama). —Ujiié and Watanabe, 1960, p. 131, pl. 3, figs. 4a-c. —Kaiho, 1984b, p. 72, pl. 7, figs. 4a-c. Melonis affinis (Reuss) (Figure 11.5) Nonionina affinis Reuss, 1851, p. 72, pl. 5, figs. 32a, b. Nonion aimonoi Matsunaga, 1963, p. 109, pl. 37, figs. 2a, b. Melonis crassus Kaiho, 1984a, p., pl. 2, figs. 6a, b, 129. —Kaiho, 1992b, p. 383, pl. 4, figs. 6a, b. Melonis pompilioides (Fichtel and Moll) (Figure 11.6) Nautilus pompilioides Fichtel and Moll, 1798, p. 31, pl. 2, figs. a-c. Nonion pompilioides shimokinense Asano, 1958, p. 71, pl. 13, figs. 14a, b. Melonis pompilioides (Fichtel and Moll). —Kaiho, 1984b, p. 74, figs. 12a, b. —Kaiho, 1992b, p. 383, pl. 4, figs. 7a, b, pl. 6, figs. 5a, b. Remarks.—Recent Melonis pompilioides lives in water deeper than the middle bathyal zone around Japan (Akimoto and Hasegawa, 1989). However, in the Poronai Formation, this species occurred in shallow marine fossil assemblages. The Paleogene M. pompilioides has a larger test than the Neogene specimens but in other biometrical aspects it fits the Recent M. pompilioides studied by Hasegawa (1983). Pullenia eocenica Cushman and Siegfus (Figure 11.7) Pullenia eocenica Cushman and Siegfus, 1939, p. 31, pl. 7, figs. la, b. —Asano, 1958, pl.11, figs. 13a, b. Pullenia cf. quinqueloba angusta Cushman and Todd. —Fukuta, 1962, p. 25, pl. 8, figs. 4a, b. Pullenia compressiuscula Reuss. —Ujiié and Watanabe, 1960, p. 131, pl. 3, Fig. 5. Remarks. — This species is distinguished from P. compressiuscula and P. quinqueloba angusta in having a broadly rounded periphery and fewer chambers in the final whorl. All specimens examined in this study are replaced with pyrite. Pullenia salisburyi R. E. and K. C. Stewart (Figure 11.8) Pullenia salisburyi R. E. and K. C. Stewart, 1930, p. 72, pl. 8, figs. 2a, b. -Asano, 1958, pl. 8, fig. 17. -Ujiié and Watanabe, 1960, p. 15, pl. 3, fig. 5. -Kaiho, 1984b, p. 72, pl. 7, figs. 7a, b. Remarks. — There are many records of this species around the North Pacific region, ranging in age from the Eocene to Recent. There has, however, been confusion among researchers on the relationship between P. salisburyi and P. subcarinata (d’Orbigny), which was originally described as Nonionina subcarinata. This study follows the views of the previous workers of the Japanese Paleogene. Heterolepa poronaiensis Kaiho (Figure 11.1) Heterolepa poronaiensis Kaiho, 1984a, p. 128, pl. 11, figs. 5a-c, 7a-c. Cribroelphidium ishikariense (Kaiho) (Figure 11.10) Elphidium ishikariense Kaiho, 1984a, p. 125, pl. 10, figs. 2a, b. Remarks.—This is the first record of this species from the Poronai Formation. Cribroelphidium sorachiense (Asano) (Figure 11.9) Nonion sorachiense Asano, 1954, p. 48, figs. 4a—Sc. Elphidium sorachiense (Asano). —Ujiié and Watanabe, 1960, p. 132, pl.3, figs. 11, 12. —Kaiho, 1984b, p. 70, 71, pl. 6, figs. 12a, b. Cribroelphidium wakkanabense (Kaiho) (Figure 12.1, 12.2) Elphidium asanoi Kaiho, 1984a. p. 124, 125, pl. 10, figs. la, b. (non E. asanoi Matsunaga, 1963) Elphidium wakkanabense Kaiho, 1992a, nom. nov. p.143. Remarks.— This species was originally described from the Wakkanabe Formation, Ishikari Group as Elphidium asanoi, and was first recorded from the Poronai Formation in the present study. Elphidium wakkanabense was pro- posed as a new name replacing E. asanoi Kaiho. The homonymic relationship with E. asanoi Matsunaga (1963) is still a primary one even though Matsunaga’s species has features which cause me to remove it to the genus Cribroelphidium based on my observation of Neogene specimens. References Akimoto, K. and Hasegawa, S., 1989: Bathymetric distribution of the Recent benthic foraminifers around Japan —As a contribu- tion to the new paleobathymetric scale—. Memoirs of the Geological Society of Japan, no. 32, p. 229-240. (in Japanese with abstract in English) Anderson, G. J., 1963: Distribution patterns of Recent foraminifera of the Bering Sea. Micropaleontology, vol. 19, p. 305-317. Asano, K., 1949: Foraminifera from the Asagai formation (Tertiary) of Fukushima Prefecture Japan. Journal of Paleontology, vol. 170 23, p.473-478. Asano, K., 195la: /llustrated Catalogue of Japanese Tertiary Smaller Foraminifera, part 9-13, 19 p., Hosokawa Printing Co., Tokyo. Asano, K., 1951b: Recent and Tertiary Cyclammina from Japan and adjacent regions. Short Papers, Institute of Geology and Paleontology, Tohoku University, no. 3, p.13-24. Asano, K., 1952: Paleogene Foraminifera from the Ishikari and Kushiro Coal-Fields, Hokkaido. Short Papers, Institute of Geology and Paleontology, Tohoku University, no.4, p. 23-46. Asano, K., 1954: Foraminiferal sequence in the Paleo-Ishikari Sea, Hokkaido, Japan. Journal of the. Geological Society of Japan, vol.60, p. 43-49. (in Japanese with abstract and de- scription of new species in English) Asano, K., 1958: Some Paleogene smaller foraminifera from Japan. Science Report of Tohoku University, Second Series (Geology), vol. 29, p. 43-75. Asano, K., 1962: Japanese Paleogene from the viewpoint of foraminifera with descriptions of several new species. Contributions from the Institute of Geology and Paleontology, Tohoku University, no. 57, p. 1-32. Asano, K. and Murata, S., 1957: Eocene foraminifera from the Amakusa Islands, Kyushu (Preliminary report). Yukochu (Foraminifera), no. 7, p. 23-27. 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R., Jr. and Tappan, H., 1987: Foraminiferal Genera and Their Classification. 2 vols., 1182 p. Van Nostrand Reinhold Company, New York. Maiya, S., 1979: Cretaceous-Tertiary foraminiferal biostratigraphy in the central and southwestern Hokkaido. p. 169-177. Committee of Hokkaido Mining Promotion, ed., Petroleum and Natural Gas resources in Hokkaido, reference data. (in Japanese, title translated) Mallory, V. S., 1959: Lower Tertiary Biostratigraphy of California Coast Ranges. 416 p. American Association of Petroleum Geologists. Matsunaga, T., 1963: Benthic smaller foraminifera from the oil fields of northern Japan. Science Report of Tohoku Univer- sity, Second Series (Geology), vol. 35, p. 67-122. Matsuno, K., Tanaka, K., Mizuno, A. and Ishida, M., 1964: Iwamizawa. Explanatory Text of the Geological Map of Japan (Sapporo-147). 168 p. Hokkaido Development Agency. McDougall, K., 1980: Paleoecological evaluation of late Eocene biostratigraphic zonations of the Pacific coast of North America. Society of Economic Paleontologists and Mineralogists, Paleontological Monograph, no. 2. 46 p. Mello, J. F., 1971: Foraminifera from the Pierre Shale (Upper Cretaceous) at Red Bird, Wyoming. Professional Papers of U. S. Geological Survey, no. 393-C, p. C1-54. Montagu, G., 1803: Testacea Britannica, or Natural History of British Shells, Marine, Land and Fresh-water, Including Most Minute, p. 1-606. J. White, London. Okada, H. and Kaiho, K., 1992: Paleogene calcareous nannofossils from Hokkaido, Japan. In, Ishizaki, K. and Saito, T. eds., Centenary of Japanese Micropaleontology, p. 461-471. Terra Scientific Publishing Company, Tokyo. Reuss, A. E., 1851: Ueber die fossilen Foraminiferen und Entomostraceen der Septarienthone der Umgegend von Berlin. Zaitschrift der Deutschen Geologischen Gesellschaft, Berlin, vol. 3, p. 49-91. Rau, W. 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B. and Dobbin, L., 1990: Recent Arctic shelf foraminifera: Seasonally ice covered vs. perennially ice cov- ered areas. Journal of Foraminiferal Research, vol. 20, p. 8-36. Seguenza, G., 1862: Dei terreni Terziarii del distretto di Messina; Parte II-Descrizione dei foraminiferi monotalamici delle marne Mioceniche del distretto di Messina. p. 1-84. T. Capra. Serova, M. Ya., 1960: Paleogene Miliolidae from the Aral-Turgey Lowland. Voprosy Mikropaleontologii, Moscow, vol. 3, p. 83-131. (in Russian, title translated) Serova, M. Ya., 1976: The Caucasina eocenica kamchatica Zone and the Eocene Oligocene boundary in the northwestern Pacific. /n, Takayanagi, Y. and Saito, T., eds., Progress in 172 Ostracoda Bathysiphon ?Ammodiscus Glomospira Cribrostomoides Evolutinella Evolutinella Haplophragmoides Haplophragmoides Haplophragmoides Haplophragmoides Haplophragmoides Haplophragmoides Haplophragmoides Haplophragmoides “Haplophragmoides" Budashevaella Budashevaella Budashevaella Budashevaella Recurvoidella Reticulophragmium Reticulophragmium Cyclammina Cyclammina Cyclammina Satoshi Hanagata le LORD Zone ls | AGGLUTINATED eocenica Cushman and Hanna sp. indet. sp. i sp. cf. C. cretacea Cushman and Goudkoff F: subamakusaensis_(Fukuta sp. cf. E. subamakusaensis (Fukuta) crassiformis Kaiho rugosus soyaensis Yasuda sp. cf. H. rugosus soyaensis Yasuda tanaii_Kaiho sp. cf. H. tanaii Kaiho sp.B sp. af. B. multicamerata (Voloshinova) symmetrica (Ujiie and Watanabe) sp. cf. B. symmetrica (Ujiie and Watanabe) F sp. indet. sp. cf. R. lamella _(Grzybowski amakusaensis (Fukuta) sp. cf. R. amakusaensis (Fukuta) ezoensis Asano sp. cf. C. ezoensis Asano pacifica Beck Cyclamminidae genus et sp. indet. Poronaia Poronaia Trochammina poronaiensis (Asano) sp. cf. P. poronaiensis (Asano) sp. cf. T. asagaiensis Asano Trochamminidae genus et sp. indet. Aggulutinated miscellaneous Quinqueloculina Quinqueloculina ?Dentalina Pseudonodosaria Pseudonodosaria Pseudopolymorphina Sigmoidella 102 PORCELLANEOUS seminula compacta Serova sp. indet. CALCAREOUS HYALINE spp. sp. cf. P. conica (Neugeboren) sp. indet. sp. cf. L. laevis (Montagu) takayanagii Kaiho sp. cf. G. takayanagii Kaiho sp.A Pacifica Cushman and Oazwa Polymorphinidae genus et sp. indet. Fissurina Glandulina Glandulina Globocassidulina Globocassidulina Bulimina Praeglobobulimina Praeglobobulimina Praeglobobulimina sp. cf. F. marginata (Montagu) laevigata ovata Cushman and Applin sp. indet. globosa (Hantken) schwageri Yokoyama sp. cf. P. ovata (d'Orbigny) pyrula d'Orbigny sp. indet. Buliminidae genus et sp. indet. Angulogerina Cibicides Melonis Melonis Melonis Pullenia Pullenia Cribroelphidium Cribroelphidium Cribroel Cribroelphidium Cribroelphidium hannai Beck elmaensis Rau affinis (Reuss) pompilioides (Fichtel and Moll) p. indet. eocenica Cushman and Siegfus salisburyi R.E. and K.C.Stewart ishikariense (Kaiho) sorachiense (Asano) cf. C. sorachiense_(Asano wakkanabense Kaiho SPP. Calcareous miscellaneous Percentage of Agglutinated Foraminifera} 78] 82 Percentage of Porcellaneous Foraminiferak 0 0 Percentage of Calcareous Foraminiferaf 22 18 Total population of Foraminiferaj - aol 117 187 Diversity (Species Richness)f Diversity (Simpson's Index for Diversi Appendix 1. E. subamakusaensis - H. crassiformis So Same Dept ling dep ma PEPEEFEERPT PEER 50 “a 0 50 x 100 6 Distributions of foraminifera in the “1 : Barren Foraminifera ; *2 : Bulimina schwageri-Angulogerina hannai_; *3 : Minaminaganuma Formation Numanohata SK-3D Depth of Formation boundary (wireline depth in meter) 3649.0m 3804m rer en L DE Formation Ishikari Group || G. subgl.-C. sorachi. Numanohat: 3070.5m +1 |Butmina schwageri-A = 1 2 1l 3 | | a aml | | es | 6 & 19 | | | 1 9 6 | | 2 4l 1 I ON 7 ec) (| | 2 1 al 1 ar 16 3 Æ 17 | | 5 7 | | | | | | | 1l | 1 2 5 5 0 100 Se: 15 0 0 0: Bern Te 1 Eocene shallow marine foraminifera wells Numanohata SK-3D and Numanohata SK-4D. a SK-4D \ngulo. hannai Poronai Formation Globoca. globosa- Cribroel. sorachiense 3507.0m 3678.5m Fault Ishikari Group Ishikari Group 3698.0 m Evolutinella subamakusaensis - H. crassiformis 173 t=} fo} LE 14 13 4 | | 5 I me. 3 I I | 17) 11 alg | 104 4 | 17 SSI I 1 2l 5 sl 2 2= 73,4 y 1 | - I 15 22! 31 (1 1 I y 1 | jan | | I | I | peo 2 j 10 1 2 CURE 1 l I | 1 1 1 I 1 I I 10 | 4, 1 1 2 1 4! 20 | TOR i 1 l 4 8 2 54 74, 58 00:13 4 26) 41 70 _7al 158 11 el 16 68 67, 82 21 21 21 10 12 148 13 ~ LIN wm ah à © lo 2] | | 1l | 44, 7 ‘| | |_ 29 2| | | LL" Nez | | 2 5 1401 9 al 2| 2 | 1! lv | 1l I 1 | 4 I I 1] 2, 3 1 6 | I | 4 3 | I ai 1 1 | 1 | al 7 l I 9] 14 7 73, 67 18, 25 26 31 282) 81 161 7 63, 47 14 on 19 42 23 24 12 3 1 19 6 1 4 1 5 1 1 6 10 al ı | | | | u | | I il | | 1 | | 1 | I | Bau ie “9 ER | I | I I if | I | | | | | 1 | | | | | | Tax | | | 3 sl 2 | | I | 1 | 3 | 1 June 74 27, 95 98 92 DT 17000000 2 60' 34 23 76 91 ol 19 151 59 44 79 132 2671 25 "4 7877350907452] 16 26, 16 15 29 18 18 Casing shoe depth: 3360m 315 13 12 2 9 15328 3 1 1 3 4 1 1 1 % 97 0 0 38 28 26 72 3 3 19 21 0 0 5 2 2 70 3 a ial 1331 21 1.9 14 100 29 2 13 100 0 0 5 2 16 100 0 0 7 2 1.9 | lee | 23 54l 45 A sh), 6 | | | | | 20, 6 | | | 14 __60| 80 2 4| | il al | | | | CRE | | | | | | | | | | | | | | | | 2 | | | 1 | | Fe | {pen 92 100, 99 000 75 007 53 1591 147 5 4 2 17 16] 13 86 6 19 1 12 1 83 _ 19 3 6 1 100 100 0 0 0 0 210 _28 2 2 14 13 AS | | | | I | 2 | | | 2 2 | | | | j | | | | I | | | | | | | | | | | | | | | | | I | | | | | 1 86 100, oo 14 0 7 _5l 174 well name Satoshi Hanagata Appendix 2. Distributions of foraminifera *1 Barren foraminifera; *2 Minaminaganuma Formation KITA-AKEBONO SK-1D Depth of Formation boundary (wireline depth in meter)|3067. Formation = Assemblage Zone| * Sample Depth (drilling depth in meter)! 8] al al al als Ostracoda PLANKTONIC Subbotina sp. indet. ?PLANKTONIC miscellaneous Om Poronai Formation Rate vat anne EURE SAME - Anguiogetiie kam: a © 0 AGGLUTINATED Bathysiphon eocenica Cushman and Hanna | ] à 1 | Bathysiphon vernoni Hamlin | | | | ?Bathysiphon spp. | 1 | 2 2 | | Placentammina 2 1 Ammodiscus | al 1 1 | 1 Glomospira 1 3 1 Reophax tappuensis Asano | | | 2 Reophax sp. cf. A, tappuensis Asano | | 1 | 7 Reophax sp. | | 1 | 3 Cribrostomoides sp. cf. C. cretacea_Cushman and Walters 1 2 2 8 1 2 1 Evolutinella subamakusaensis (Fukuta) 1 8 26 6 2 24 6 1 2 1 3 1 8 Evolutinella sp. cf. E. subamakusaensis (Fukuta) | | | Haplophragmoides crassiformis Kaiho | | | Haplophragmoides sp. cf. H. crassiformis Kaiho | 5 39) 22 11 27 6 17| 22 3 7 6 4 8 Haplophragmoides rugosus soyaensis Yasuda 1 3 Haplophragmoides sp. cf. H. tanaii Kaiho 1 Haplophragmoides yokoyamai Kaiho | | 1 | | Haplophragmoides | | 1 | | Haplophragmoides | | | | Haplophragmoides 1 3 1 1 5 2 1 Haplophragmoides 1 2 2 60) 13 4 45) 71 28 20 20) 4 50 462 94 81) 37 101 24 Discammina | | | | Budashevaella sp. aff. B. multicameratus (Voloshinova) 8 8 Budashevaella symmetrica (Ujiie and Watanabe) | 41 47 22 2 2 al 4 4 à: | Recurvoides | | 72 il | Recurvoides } | 9 | 551 | Recurvoidella sp. cf. R. lamella (Grzybowski) 5 30 3 | 5 8 111 7 43 62 17 19) 12 48 59 ?Ammobaculites SPP. | | | | "Clavulina * sp. indet. 3 Alveolophragmium } | | | | Reticulophragmoides amakusaensis (Fukuta) U4 GS WG om a 7 Ga 2 1 72 6 Cyclammina ezoensis Asano | | | 1 3 Ù 4 Cyclammina pacifica Beck 1 1 2] 2 3 12, 14 #17 17 10 4 5 2 7 2| 3 3 Cyclammina sp. aff. C. pusilla Brady | | | 1 1 | 5 Cyclamminidae genus et sp. indet. 1 1 6 10 i 3 12, 21 25 10 13 6 i 3 6 11 10, 11 10 17 ?Dorothia sp. indet 1 1 Poronaia poronaiensis (Asano) | | 13 2 3 | 1 | Trochammina sp. cf. T. asagaiensis Asano | I | | Trochammina spp. | 1] 7 1 | | fragment Clavulina_like species's aperturel end 1 3 Agglutinated miscellaneous in 1 A2 16 m GH 3 14, 24 106 94 23 3, 18 27 27 24 5 SEE PORCELLANEOUS | | | Quinqueloculina seminula compacta Serova 1 5 2 il 2 Quinqueloculina SPP. 1 | 2l 38 4 | Miliolidae miscellaneous al | | CALCAREOUS HYALINE I | Dentalina sp. cf. D. subsoluta (Cushman) of Kaiho, 1984 | | | “Dentalina " spp.(fragments) | 1 8 | | Pseudonodosaria conica (Neugeboren) | | | ?Astacolus sp. } Lenticulina sp. | | | Marginulina sp. Lagena sp. cf. L. laevis (Montagu) 1 2| | 1| Ure "Lagena " SPP. 1 1 | 2 | | Procerolagena sp. cf. P. gracilima (Seguenza) | 1 | | Guttulina problema _(d'Orbign 1 1 Guttulina takayanagii Kaiho 1 - Guttulina sp. cf. G. takayanagii Kaiho | | 1 | "Guttulina " SPP. | | 1 | Pseudopolymorphina hokkaidoana Kaiho 1 | I Sigmoidella pacifica_Cushman and Ozawa 1 1 1 A? 1 a Fissurina sp. cf. F. marginata (Montagu) | Glandulina laevigata ovata Cushman and Applin 1 1 | 1 1 4 2 1 Globocassidulina globosa (Hantken) 1 1 3 | 1.2 74 A Globocassidulina spp. 1 | 2 | Bulimina schwageri Yokoyama 1 4| 50 16 2 4 9 4 3 1 1 1 Praeglobobulimina pyrula (d'Orbigny) | | | Globobulimina & Preglobobulimina spp. | 3 5 | Angulogerina hannai Beck 13), 33 20 5 1 2 3 1 1 Cibicides sp. A | | | Cibicides spp. I I | Nonionella japonica (Yokoyama) | j | | Melonis affinis (Reuss) | | | | 2 2 Melonis pompilioides (Fichtel and Moll) | 1 2 2 1 | 1 6 6 | 1 2 4 Pullenia eocenica Cushman and Siegfus 2 u & U salisburyi R.E. and K.C.Stewart | 1 2 1 | 1110 8 él 2 7 6 Heterolepa poronaiensis Kaiho Cribroelphidium ishikariense Kaiho | I | | Cribroelphidium sorachiense (Asano) 2 375977919 1 N 1 8 À | 2A 8s 8 HY} 2 Hb © Cribroelphidium wakkanabense Kaiho 4 1} 2 | | | i 13 1 Calcareus miscellaneous 10 a 1 7 7 U 1 2 2 PEST SEN 9 2 7 6 Percentage of Planktonic speices| @ 0 0 0 o 0 0 0 o 0 0 0 o 0 0 0 0 0 0 0 0 0 0 o Percentage of Agglutinated species D 333 100 556 433 89.5| 63.6 0 0 889 79.7! 495 83.3 93.4 928 o6l967 68 90.7 77.9 83.21 77.6 84.8 88,7 Percentage of Calcareous benthic species © 667 0 44.4 58.2 10.5136.4 100 100 11.1 20.31 50.5 16.7 6.64 7.22 4.031 3.3 32 9.27 22.1 1681 22.4 15.2 11.3 g 9 2 9 67 124 27 172] 277 408 241 97 149 197 626 217 161] 107 282 247 3 1 2 7 4 [7 0 1 5 11) TTS 8 7 1 © © 8] Was 1k) Di 2.33 1 __1.6 3.57 2.04, 4.31 1 3 5.21, 5.78 9.58 7.26 6.02 5.02, 6.02 2.92 2.61 8.28 4.54, 5.59 3.48 3.26 Casing shoe depth: 3096m Eocene in the well Kita-Akebono SK-ID. shallow marine foraminifera 3628.0m Ishikari Group ai | Globocassidulina globosa - Cribro. sorachiense E. subamakusaensis - H. crassiformis 187 221] 531 647 485 755 776) 778 85 912 321 S60) 350 339 287 362 288] 483 572 585 102 65) 330 150 ry 14 16 13 15 16 15 18 14 16 17 14 10 10 14 1 © > a ae = Nn iv La © ao So N N o oO © N + © o So N © oO © EFEFFEÉÉEEEEEÉEEEEE S| Sl 8 S$] S| S| S| 51 51 8) 81 8 S| 88 a — — m m m m mm a SL Le mm Sure] m oy a CRE Ter = T T I I 1l I | | =. 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Barren 3 a oO oOo Of 175 176 Satoshi Hanagata Appendix 3. Distributions of “1 : Barren Foraminifera ; *2 : Minaminaganuma Formation tina] MIT Umaoi Depth of Formation boundary (wireline depth in meter 3640.0m Poronai Formation Bulimina schwageri - Angulogerina hannai g 8] S| &| SI 8| 2| S| &| S|] 2| 8 al 3 2| 8 3] 2| 8 Sample Depth (drilling depth in meter)| 2 SI SIL SIL SILELEIL Sil 8 8 88 8| 3 als 8 SI 8 \ 1 | | i | 26122 22 | | | | | Planktonic foraminifera genus et sp. indet. il AGGLUTINATED | | | | | Bathysiphon eocenica Cushman and Hanna 1 1 | § § 1 5 2| | ?Ammodiscus sp. indet. 1 1 Glomospira SP. | | | 1 | 1 al Reophax h I | | 14 | Cribrostomoides . cf. C. cretacea Cushman and Goudkoff 5 Evolutinella subamakusaensis (Fukuta) x 1 1 | 17 1 1 1 | | 40] 6 Evolutinella sp. cf. E. subamakusaensis (Fukuta) | | | 4 3 | | Haplophragmoides rugosus soyaensis Yasuda Haplophragmoides sp. cf. H. rugosus soyaensis Yasuda | | | 2 | IN Haplophragmoides crassiformis_Kaiho | | | 2l 1 1 l Haplophragmoides sp. cf. H. crassiformis Kaiho | 11 5 | 4 6 | | | Haplophragmoides tanaii Kaiho | | | 3) | 6 Haplophragmoides yokoyamai Kaiho GS À 1 Haplophragmoides | | | 1 | 1 | Haplophragmoides | l I | 3 | "Haplophragmoides " So 98 9 ZI © 8 2. U 1 408 52) 401 17 25 3 10 10] 7 3 101 11 Ammobaculites sp. indet. | | | | | Budashevaella sp. aff. B. multicamerata (Voloshinova) | 4 | 9 | 11 7] | Budashevaella symmetrica (Ujiie and Watanabe) 2 1 3 6 2 7 4 2 15 1 2 Budashevaella sp. indet. | | | | | Recurvoides sp. A 1 1 1 Recurvoidella sp. cf. A. lamella (Grzybowski) | 5 2 2| 4 4 1 14| A 8 2| 10 2 9 2 4 32 Alveolophragmium sp. A | | 2 1 | | | Reticulophragmium amakusaensis (Fukuta) 2 2 1 2 1 2 11 4 5 9 8 1 | 4 6 10 10 8) 2 1 2] 2 Cyclammina ezoensis Asano 1 1 Cyclammina pacifica Beck 1 6 3 14 11 9 4 23 6 10 8 8 11 12 GQ & 2 4 Cyclamminidae genus et sp. indet. „98 d 7 8 27 61 13 18 14 2 131 13 6 13 12 9Ù 6 1 1 6 el 8 Poronaia poronaiensis (Asano) | | 5 2 | | Trochammina sp. cf. T. asagaiensis Asano | | | 1 1 | Trochamminidae genus et sp. indet. 4 ?"Clavulina " sp. À Clavulina sp. indet. fragment of "Clavulina “ like apertural end Aggulutinated miscellaneous PORCELLANEOUS Quinqueloculina sp. indet. CALCAREOUS HYALINE 16 4 21 26] 39 47 21 77 30] 40 56 107 30 153] 74 25 32 73 109] 71 18 15 8 40] 101 ?Dentalina SPP. | | 1 | 3 1 | | Lagena striata (d'Orbigny) | | | 1 | | Lagena sp. cf. L. laevis (Montagu) | | I 1 | I Guttulina takayanagii Kaiho 1l | | 1 | | Guttulina Pseudopolymorphina sp. indet. | | 1 | | | Sigmoidella pacifica Cushman and Oazwa 1 2 1 2 2 3 1 1 1 1 1 Polymorphinidae genus et sp. indet. | | 4 1 | 2 | | Glandulina laevigata ovata Cushman and Applin | | | | | Glandulina sp. indet. 1 ?Cassidulinoides SP. | | | | ji Globocassidulina globosa (Hantken) 1 & 1 6 | 2 1 2 1 ai 1 2 | | Globocassidulina SPP. 2 1 1 Bulimina schwageri Yokoyama 13 15 | 1 40 13! 33 8 9 57 97! 2 59 54 sl 4 1 lese Globobulimina sp. indet. | | | | 14 Buliminidae genus et sp. indet. | J À | 4 | | À | Angulogerina hannai Beck 1 4 12] 1 ; À 4 23) 20 34 18] 4 1 1 1 13 Nodogeneria sp. cf. N. lepidula (Schwager) 1 “Nonion “ sp. indet. | | 1 | | | japonica Yokoyama I | | 1l | sp. cf. M. affinis (Reuss) ] | | 3 | | Melonis pompilioides (Fichtel and Moll) | | | | | © Melonis sp. indet. | | | 2 3 | | eocenica Cushman and Siegfus 1 salisburyi_R.E. and K.C.Stewart | 2 | | | ll © Cribroelphidium sorachiense (Asano) 1 7 1 4 1 2 2 3 1 Cribroelphidium spp. 2 | | 1 2| 3 | | Calcareous miscellaneous 2 54, [A jh 7 9 8 2 EH 6 14 14 8 1 el Percentage of Agglutinated Foraminifer. 100 54 53 72,100 94 81 69 73) 66 86 87 40 60) 99 81 42 52 75) 92 89 97 79 95) 83 Percentage of Porcellaneous Foraminifer: 0 o oO 0 0 0 004 0 0 © © © 0.2) 0 @ © © 0 0 © © © 9 0 Percentage of Calcareous Foraminifera}: 0 46 47 28 0 59 19 30 27 34 14 13 60 40 07 19 58 48 25 76 11 29 21 46 17 Total population of Foraminifer. 23 _ 39 55 67! 75 68 36 232 gsl 131 147 242 111 4071 145 90 181 241 233! 118 28 34 24 10gl 209 2 6 6 6 4 6 4 12 8l 11 10 14 10 13 9 10 11 12 141 11 7 4 1 71 12 Diversity (Species Richness, Diversity (Simpson's Index for Diversit 1 1.8 21 19] 23 36 27 39 35) 29 68 57 17 27] 55 52 29 36 56) 48 53 21 53 1.4] 43 Eocene shallow marine foraminifera 177 foraminifera in the well MITI Umaoi. 4421.5m Ishikari Group Globo. globosa- Cri. sorachiense er SITES H. crassiformis 55 20 12 25 17 8 | Te woo © az 1 a ae 5 | | | I | I seal | | [2 Ji tn | l | | FANS NZ) | | | I I | I | | I I 15 45 80 19] 20 20 AMEL Tel TE 1 1 | | | | 1 2 9 7 | | | Sadia | | | 18 2 47 106] 52 32 9 11 17] 24 11 108 | | 6 2 2! radis ie | | | : | 3 4 2 HR RS 06 3 3° 2 3 I 11 6 | & 2 1 | 2 I | | | 1 | | | | | I | | I | I | 64-107 99 30) 76 66 5 8 4) 3 15 15 19 3) 2 2 1 I | | | tie 2 1 I | | | | | | | | | | | | | | | 2 | 2! | | TT | | 3 | 2 I | | Pere 4 2 ! | 1 | | | I I | I | | | I 1 | | | 4 | | | | I l | | | | | I | | 11 1 6 2 2 | 1 1] | ss I I I 1 2 1! | | 2 i 2 2 4 Aura N | (CES TE er ene tee anes a 1 B 2 © 911 94 94 52 77 81] 28 97 100 100 94; 93 100 100 100 100| 100 100 100 100 100 0 0 00511 0 032 5 0 0 0 0 0 0 0 0 0 © 0 0 © 0 0 maine 6953160) 48) 19, 18% 13.28 0 10.58.74) 0 010 OF 0 00 0 10 208 222 204 213)188 142 31 31 26! 40 39 27 179 171 14 3 3 19 af 9 1 2 3 3 FUEL ER CE 33 38 35 161 23 22 1 22 141 12 1 13 16 1923 1 2 11 1| 2 1 2 178 Micropaleontology, Selected Papers in Honor of Prof. Kiyoshi Asano. p. 314-328, American Museum of Natural History, Micropaleontology Press. 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(in Japanese) Zalesny, E., R., 1959: Foraminiferal ecology of Santa Monica Bay, California. Micropaleontology, vol. 5, p. 101-126. Zheng, S. and Fu, Z., 1992: The agglutinated foraminifera of the Bohai Sea and Huanghai Sea. In, Takayanagi, Y. and Saito, T. eds., Studies in Benthic Foraminifera, BENTHOS ‘90, Sendai, 1990, p. 183-197, Tokai University Press. Paleontological Research, vol. 6, no. 2, pp. 179-189, June 28, 2002 © by the Palaeontological Society of Japan Feeding strategy of an Early Miocene cetothere from the Toyama and Akeyo Formations, central Japan TOSHIYUKI KIMURA Gunma Prefectural Museum of Natural History, 1674-1, Kamikuroiwa, Tomioka, Gunma 370-2345, Japan (kimura@ gmnh.pref.gunma.jp) Received March 21, 2001; Revised manuscript accepted January 31, 2002 Abstract. The feeding strategy of cetothere from the Toyama and Akeyo Formations is discussed based on the mandibles of two individuals. Three synapomorphic characters in the mandible that are shared with balaenopterid whales (a laterally projecting coronoid process, a marked inward elevation at the dorsal edge of the ramus posterior to the coronoid process, and a sharply edged ventral margin on the middle part of the mandible) suggest that some cetotheres had already acquired an engulfment feeding mechanism by the late Early Miocene. Two other apomorphic characters (a quite high and elongated dorsal mandibular ridge and a ventrally well-projected mandibular angle) suggest robust development of the musculature of the mandible during the feeding process in the studied specimens in contrast to the weak development of the musculature in the balaenopterids. This may represent a primitive transitional stage of the engulfment feeding mechanism which could be related to the lack or poor development of highly elastic elements in the ventral pouch. Key words: Cetotheriidae, Early Miocene, engulfment feeding, feeding mechanism, mandible, Mysticeti Introduction Mysticetes have acquired baleen plates and developed a unique filter feeding mechanism during the process of their evolution. The feeding strategy of the extant Mysticeti is generally divided into three types: skim feeding for plank- ton (Balaenidae), mud scooping (Eschrichtiidae), and engulfment feeding for fast-swimming krill and fish (Balaenopteridae) (Brodie, 1977; Pivorunas, 1979; Berta and Sumich, 1999). The evolution of filter feeding was a primary factor for the origin of mysticetes (Fordyce, 1980, 1989). Since the Cetotheriidae are the earliest true baleen- bearing, toothless mysticete family (Barnes, 1984; McLeod et al., 1993; Fordyce and Barnes, 1994), the study of their feeding mechanism is important for considering the evolu- tion of filter feeding in mysticetes. McLeod et al. (1993) pointed out that cetotheres have the following three mor- phological characteristics as compared with balaenopterids— (1) more posteriorly directed mandibular condyle; (2) larger coronoid process of mandible; and (3) longer zygomatic process of squamosal. Based on these charac- ters, these authors briefly mentioned that cetotheres were probably engulfment feeders displaying a less specialized mandible and skull morphology and with a weaker throat groove than balaenopterids. However, there is no other detailed discussion in the literature about cetothere feeding strategy. Two cetothere mandibles were found from the Lower Miocene Toyama and Akeyo Formations, Gifu Prefecture, Japan. The mandible has a primary functional role for feeding, and its morphology may reflect to a high degree the feeding strategy. The purpose of this paper is to exam- ine the feeding strategy of the cetotheres based on the two mandibles and to discuss the evolution of the engulfment feeding mechanism. Materials Two cetothere specimens were examined in this study. Both specimens are deposited in the Mizunami Fossil Museum, Mizunami, Gifu Prefecture, Japan (MFM). MFM18124, Cetotheriidae gen. et sp. indet. (Figure 1).— Both mandibles, skull fragments, cervical and thoracic ver- tebrae, ribs, a sternum, a humerus, and some bone frag- ments. The right mandible is almost complete. This specimen was found from the Kubohara Facies of the Toyama Formation, Iwamura Group, Iwamura town, Ena County, Gifu Prefecture, Japan (Kimura er al., 2000). The horizon from which this specimen was collected is corre- lated to the Maki Member of the Toyama Formation, Iwamura Group (Ujihara et al., 1992). The Maki Member is assigned to the Crucidenticula sawamurae Zone (late 180 Toshiyuki Kimura Figure 1. Cetotheriidae gen. et sp. indet. from Toyama Formation, MFM18124, right mandible. A. Lateral view. B. Dorsal view. C. Medial view. Hachures indicate areas where mandible is damaged. Scale bar equals 50 cm. After Kimura et al. (2000). from Akeyo indet. A. Dorsal view. B. Medial Scale Figure 2. Cetotheriidae gen. et sp. Formation, MFM18125, right mandible. view. Hachures indicate areas where mandible is damaged. bar equals 10 cm. Early Miocene: Barron and Gladenkov, 1995; Yanagisawa and Akiba, 1998) based on diatom biostratigraphy (Ito et al., 1999). This specimen was originally described by Kimura et al. (2000). MFM18125, Cetotheriidae gen. et sp. indet. (Figure 2). —Right mandible. A posterior half of the mandible in- cluding condyle and angle is preserved. This specimen was found from the Lower Miocene Yamanouchi Member, Akeyo Formation, Mizunami Group, Togari, Mizunami City, Gifu Prefecture, Japan and was once referred to Mysticeti, gen. and sp. indet. (Kamei and Okazaki, 1974: p. 283, pl.97, figs.6a, b). The Akeyo Formation consists of the Tsukiyoshi, Togari, Yamanouchi, and Hazama Members in ascending stratigraphic order (Itoigawa, 1974, 1980). Kobayashi (1989) estimated the age of the Akeyo Formation to be 17-17.5 Ma on the basis of fission-track dating. Itoigawa and Sibata (1992) suggested that the Yamanouchi Member is assigned to Upper Zone N.7 to Lower Zone N.8 of Blow (1969). Kohno (2000) also sug- gested that the Yamanouchi Member is late Early Miocene (ca. 18-17 Ma) based on the radiolarian and diatom dating. These two mandibles share a characteristic morphology of a quite high and elongated dorsal ridge with a concavity at its medial side. This character clearly distinguishes the present species from any other known mysticetes. These edentulous specimens are clearly distinct from primitive, toothed mysticete families. Additionally, these two man- dibles are characterized by the following combination of characters: (1) a large mandibular foramen; (2) a well- developed coronoid process that projects dorsally, laterally, and posteriorly; (3) a posteriorly directed articular surface of the condyle; (4) a sharply edged ventral margin on the middle part of the mandible. This combination of charac- ters is not found in any extant mysticete families (Balaenopteridae, Eschrichtiidae, Balaenidae, and Neobala- enidae). Therefore, these two specimens are recognized as the same species in the Cetotheriidae, gen. and sp. indet. as will be discussed below (Kimura er al., 2000). The Cetotheriidae have long been considered as a paraphyletic grade lacking the diagnostic characters of more derived mysticete families (e.g., Fordyce and Barnes, 1994). For comparison, I examined the material of the following extant Mysticeti housed in the National Science Museum, Tokyo (NSMT): Balaenopteridae: B. acutorostrata (NSMT-M15941, NSMT-M32543), B. edeni (NSMT- M03538, NSMT-M32599); Eschrichtiidae: E. robustus (NSMT - M15940); Balaenidae: B. glacialis (NSMT - M03538). Feeding strategy of cetothere 181 Table 1. Measurements of right mandible (in mm), Cetotheriidae gen. et sp. indet. from Toyama (MFM18124) and Akeyo (MFM18125) Formations. MFM18124 MFM18125 Length of mandible in a straight 1777 734+ line Length of mandible along out- 1810 735+ side curvature Distance from anterior end of 1572 = ramus to level of center of coronoid process along out- side curvature Vertical diameter coronoid process Vertical diameter of hinder end 187+ 152+ of ramus including condyle Transverse diameter of condyle 108+ 80+ Vertical (H) and bransverse (W) diameter in 100-mm incre- ments form the anterior end of ramus throught 214+ 154+ 300 123 59 113 64 400 117 65 119+ 72 500 121 68 154+ 71 600 121 70 107 55 1600 145 71 Description The right mandible of MFM18124 is almost complete except for erosion of an angle (an), a dorsolateral edge of a coronoid process (cp), and a dorsal and lateral part of a condyle (co) (Figure 1). All of the epiphyses on the pre- served vertebrae (cervical and thoracic) are firmly ankylosed to the centra, and this condition in extant mysticetes is regarded as evidence of physical maturity (Omura, 1975). MFM18125 consists of only the posterior half of a right mandible and is smaller than MFM18124 by approximately 75% (Table 1). In MFM18125, the coronoid process is broken off except for its base and the dorsal and lateral portion of the condyle was eroded away (Figure 2). Unless otherwise mentioned, the descriptions zn 0 10 20 30 40 50 60 70 80 100 110 120 130140 150 160 170 10 2 00 4 s0 m Enr to none renom 8 width(mm) >} Lsx (cm) Figure 3. Change in measurements. A, B. Height (A) and width (B) of right mandible of MFM18124 and MFM18125 in 100- mm increments from anterior end, at left. Open squares represent minimum values, owing to breakage of specimen. Abbreviations: Lsx, distance between anterior end of ramus and measurement points along a straight line. Modified from Kimura er al. (2000). are based on MFM18124. A roughened area at the anterior tip of the mandible is short and does not exceed 75 mm. A longitudinal crease on the medial surface at the anterior tip of the mandible is 142 mm long. The horizontal ramus is rotated around its axis and its medial surface slopes lingually. The amount of rotation at the anterior tip of the horizontal ramus is about 30° against the medial surface at the region of the coronoid process. The horizontal ramus tapers slightly in dorsoventral diameter from the region of the coronoid proc- ess toward the anterior tip (Figure 3). However, the dorsoventral diameter increases at the anterior one-fifth of the mandible. MFM18124 preserves three mental foramina along the dorsolateral surface of the mandible. These foramina occur at 485, 1010, and 1199 mm behind the anterior tip of the mandible and lie at 7, 31, and 43 mm below the dorsal margin of the horizontal ramus. These foramina open into an anteriorly directed groove. Figure 4 shows the cross sections of the mandibles. There is a noticeable flattening of the anterior one-third of the medial surface of the mandible. Posterior to this, the medial surface of the ramus becomes convex medially. A concavity occurs at the medial side of the high dorsal ridge. 182 Toshiyuki Kimura RK 1s; sea MFM18125 : Figure 4. ment point along a straight line. A groove is present on the medial surface of the horizontal ramus anterior to the mandibular foramen (mf). The lat- eral surface of the mandible becomes progressively convex dorsoventrally toward the posterior end. The greatest transverse diameter is below the midline at the middle part of the mandible. Further posteriorly, the greatest diameter shifts dorsally. Ventrally the lateral surface meets the me- dial surface to form a well-defined angular edge in the mid- dle part of the mandible. This angular edge approaches the internal face anteriorly. The angular edge becomes rounded posteriorly at the region of the coronoid process. In dorsal view, the mandible is only slightly bowed late- rally (Figure 1B). The length of the mandible along the outside curvature represents only 102% of the length of the mandible in a straight line. The outward curvature is grad- ual and not abruptly flexed. There is no reflexion at the re- gion of the coronoid process as in the balaenopterids. In lateral view, the ventral profile of the horizontal ramus is almost straight (Figure 1C). But in MFM18125, the ven- tral margin of the mandible anterior and posterior to the coronoid process is dorsally arched (Figure 2B). The coronoid process projects dorsally, posteriorly, and laterally. The apex of the coronoid process is located at Cross sections of right mandible of MFM18124 (above) and MFM18125 (below). damaged. Dashed line in cross section represents mandibular foramen. 160 170 medial Ode Hachures indicate areas where mandible is Abbreviation: Lsx, distance between anterior end of ramus and measure- 87% of the length of the mandible along the outside curva- ture from the anterior extremity. The anterior margin of the coronoid process rises gradually, but its posterior mar- gin descends abruptly. A shallow concavity occurs on the medial surface of the coronoid process along its anterior margin (Figure 5). Behind the apex, the posterior edge of the coronoid process thickens whereas the anterior edge re- mains thin. An inward elevation (ie) occurs on the medial surface of the upper border near the middle of the ramus behind the coronoid process (Figure 5). The inward eleva- tion has a sharp edge and projects inward. It becomes more prominent anteriorly. This inward elevation contin- ues anteriorly and dorsally to a ridge on the medial surface of the coronoid process. In MFM18125, because of break- age, a longitudinal groove occurs at a dorsomedial edge of the corresponding part of the ramus. But the remaining part projects slightly medially, and this suggests the devel- opment of the inward elevation in MFM18125. The in- ward elevation is also found in the Balaenopteridae. However, the elevation in the Balaenopteridae is more rounded than that of MFM18124 and MFM18125 (personal observation). For a distance of at least 880 mm anterior to the apex of the coronoid process, a relatively high dorsal Feeding strategy of cetothere 183 Figure 5. mandible, medial view. ward elevation; mf, mandibular foramen; sf, subcondylar furrow. ridge forms the dorsal edge of the horizontal ramus (Figures 1, 4). Anteriorly, the dorsal ridge becomes rounded and curved medially. A mandibular foramen is large. The condyle is expand- ed from side to side and is more convex transversely than dorsoventrally. The forward-curving external border of the condyle projects beyond the lateral surface of the adjacent portion of the ramus. The maximum transverse expansion of the condyle (MFM18124, 108 mm+; MFM18125, 80 mm+) occurs below the midline of its vertical diameter. Ventrally, the condyle almost maintains its width. Ventrally, the condyle is bounded by a subcondylar furrow (sf) above the angle. This furrow extends across the pos- terior face of the condyle and decreases in depth laterally. Although the angle of MFM18124 is damaged, the pre- served portion projects far ventrally. In MFM18125, the angle is almost complete, robust and projects ventrally (Figure 2). Cetotheriidae gen. et sp. indet. from Toyama Formation, MFM18124. A, B. photograph and drawing of posterior part of right Hachures indicate areas where mandible is damaged. Abbreviations: an, angle; co, condyle; cp, coronoid process; ie, in- Scale bar equals 10 cm. Modified from Kimura er al. (2000). Discussion Morphological characters of mysticetes can reflect their feeding strategy (McLeod et al., 1993). Since the mandi- ble plays an important role in feeding process, we can make inferences about the feeding strategy of fossil mysticetes from their mandibular morphology. Apomorphies for engulfment feeding Coronoid process.—The coronoid process of the mandi- ble in the balaenopterids is large and projects both posteriorly and laterally. The coronoid process in the basal suborder Archaeoceti and the toothed mysticetes Aetiocetidae is also large, but does not project laterally (Kellogg, 1936; Barnes er al., 1995; Gingerich and Uhen, 1996; Hulbert er al., 1998). The laterally projected coronoid process of the balaenopterids is considered to be a derived condition. In contrast, the non-engulfment feed- 184 Toshiyuki Kimura Studied Specimens oa anterjor MFM18124 Balaenopteridae B. acutorostrata (NSMT-M32543) Figure 6. Hachures indicate areas where mandible is damaged. ers (Balaenidae, Neobalaenidae, and Eschrichtiidae) convergently acquired a quite small coronoid process (Barnes and McLeod, 1984) unless those three families form a monophyletic group. The coronoid process provides the insertion for the temporal muscle which generates most of the elevating force during feeding in rorquals (Carte and MacAlister, 1868; Schulte, 1916; Lambertsen, 1983; Lambertsen et al., 1995). The shape of the coronoid process is functionally important for engulfment feeding because it requires a complicated motion of the mandible (Lambertsen et al., 1995). MFM18124 has a large and laterally projected coronoid process similar to the balaenopterids (Figures 1, 5). Although the coronoid process of MFM18125 is miss- ing, the base of the process also suggests that the process is curved laterally (Figure 2B). Ventral margin of the mandible.—The cross-sectional shape of the ventral margin of the middle part of the man- dible is clearly differentiated among the mysticete families (Deméré, 1986; Nagasawa, 1994). In the Balaenopteridae, MFM18125 anterjor B. edeni (NSMT-M32599) Eschrichtiidae E. robustrus (NSMT-M15940) Balaenidae 1 1 B. glacialis (NSMT-M05153) Cross sections of mandible just behind (1) and base (2) of coronoid process (not to scale). Arrows indicate an inward elevation. the ventral margin of the cross section in the middle part of the mandible forms a well-defined angular edge (Deméré, 1986; Kimura et al., 1987; Nagasawa, 1994). The sharply edged ventral margin of the cross section in the middle part of the mandible is also developed in MFM18124 and MFM18125. The mylohyoid muscle is attached along this ventral ridge (Pivorunas, 1977; Lambertsen, 1983). In engulfment feeding, the mylohyoid muscle, together with other muscles (multiple muscle layers: Lambertsen, 1983), plays an important role in expelling the sea water through the baleen plates (Lambertsen, 1983; Orton and Brodie, 1987). The marked ridge on the ventral margin of the mandible suggests the presence of well-developed mylohyoid muscles. Inward elevation of the mandible.—The degree of devel- opment of the elevation is variable in the Balaenopteridae, stronger in B. acutorostrata than in B. edeni (Figure 6). This inward elevation is also found in B. musculus (Struthers, 1889). In Megaptera novaeangliae, the eleva- tion is rises upward on the same part of the mandible and Feeding strategy of cetothere 185 is called the post-coronoid elevation (Struthers, 1889). The studied specimens have a remarkable inward elevation on the medial surface of the upper border near the middle of the ramus behind the coronoid process similar to the balaenopterids. In contrast, the structure of the corresponding part is quite different in the Eschrichtiidae and Balaenidae. In the Eschrichtiidae, the coronoid process is quite low and pro- jects laterally. Posterior to the coronoid process, there is a low process which projects dorsally, and this process con- tinues posteriorly to a low ridge on the medial surface of the ramus. Below this low ridge, another longitudinal faint ridge is also present. In the Balaenidae (B. glacialis), the coronoid process is faint and, posterior to the coronoid process, a shallow groove is present on the dorsomedial surface of the ramus (anteroposterior length of the groove: right 46 mm/left 59 mm). This groove makes a low bump on the medial surface of the upper part of the ramus. Although there is a ridge on the dorsomedial surface of the ramus in both families, the ridge is faint and does not pro- ject medially (Figure 6). Further, there is no ridge on the medial surface of their quite low coronoid process. Therefore, these structures found in the Eschrichtiidae and Balaenidae are clearly distinguished from the prominent in- ward elevation present in the studied species and the Balaenopteridae. The frontomandibular stay is a functionally and anatomi- cally specialized tendon of the temporal muscle and is at- tached to the inward elevation (Struthers, 1889; Lambertsen et al., 1995). This stay apparatus is common among the balaenopterids and serves to support the motion of the man- dible during the feeding process, especially in initiating engulfment (Lambertsen er al., 1995). The above three characters suggest that the species had an acquired engulfment feeding mechanism. The Cetotheriidae is believed to include taxa closely related to the ancestor of the Balaenopteridae (Fordyce and Barnes, 1994). The three apomorphies are also found in the Balaenopteridae. However the phylogenetic relationship between the cetothere species in this study and the Balaenopteridae is still unclear and the analysis of the rela- tionship is beyond the scope of this study. So, more de- tailed consideration is needed to ascertain whether these characters are synapomorphies between the two. Efficiency of engulfment feeding One aspect of engulfment feeding efficiency relates to the size of the mouth cavity. The mandible of the studied specimens is slightly curved, a primitive condition (Barnes and McLeod, 1984). Deméré (1986) suggested that the width of the rostrum is directly proportional to the extent of the lateral curvature of the mandible. This suggests that the mouth cavity of the studied specimens was relatively small and that engulfment feeding in MFM18124 and MFM18125 was less efficient than in the extant balaenopterids. The mandible of the balaenopterids changes continu- ously in its position during the engulfment feeding process by three motions—(1) alpha rotation: an inward and out- ward rotation around the longitudinal axis of the mandible; (2) delta rotation: depression and elevation of the mandible; and (3) omega rotation: medial and lateral movement of a condyle of the mandible (Lambertsen er al., 1995). The temporomandibular articulation in extant balaenopterids is, unlike other mammals, composed of a fibrous meniscus in- filtrated with oil (Hunter, 1787; Carte and MacAlister, 1868; Beauregard, 1882; Beneden, 1882; Struthers, 1889; Schulte, 1916). Since this meniscus enables the movement of articulation more effectively, like planar quadrilateral connecting system, the squamomandiblar articulation of the balaenopterids can perform its complicated movements (Lambertsen et al., 1995). Cetotheres are generally char- acterized by having a more or less flattened articular sur- face of the squamosal (Miller, 1923). This suggests that the temporomandibular articulation composed of a fibrous meniscus was not acquired or poorly developed in the Cetotheriidae. Neither of the studied specimens includes the squamosal, and it is unclear that they were able to per- form these complicated movements of the mandible. Lambertsen et al. (1995) suggested that stronger lateral curvature and elongation of the mandible would increase alpha-rotation of the mandible. If these specimens were able to perform alpha-rotation, the small amount of curva- ture suggests that this could not contribute greatly to the en- largements of the mouth. This suggests that cetotheres fed less efficiently than the balaenopterids. Feeding strategy of Balaenopteridae In the Balaenopteridae, the musculature of the mandible mainly braces the jaw during engulfment feeding and does not actively open it (Lambertsen, 1983; Orton and Brodie, 1987; Lambertsen et al., 1995). This passive movement of the mandible is mainly caused by water pressure resulting from locomotion and allied action of a ventral pouch (Brodie, 1977; Orton and Brodie, 1987; Lambertsen er al., 1995; Bakker et al., 1997). The ventral pouch (body wall below the cavum ventrale: Lambertsen, 1983) is a highly elastic grooved structure which consists mainly of blubber and multiple muscle layers, covering the ventral surface of the whale from the anterior border of the mandible to the umbilicus or further (Pivorunas, 1979; Lambertsen, 1983; Orton and Brodie, 1987). The pouch is filled by voluntary increase of the curvature of its elastic ventral wall by con- traction of multiple muscle layers. This changes the water flow between the upper and lower surface of the head and causes asymmetry of the hydraulic pressure which assists in 186 Toshiyuki Kimura depressing the mandible (Bernoulli principle) (Lambertsen et al., 1995). The passive movement of the mandible in filling the pouch is also suggested by the fact that the re- laxation of jaw musculature makes the lower jaw drop (Lambertsen, 1983). Lambertsen et al. (1995) also sug- gested that as a result of the mode of attachment of the ven- tral pouch to the mandible, hydraulic pressure can rotate the mandible around its longitudinal axis (alpha rotation). Active contraction of musculature is required for water ex- pulsion, especially in the final phase (Lambertsen, 1983; Orton and Brodie, 1987). Orton and Brodie (1987) sug- gested two sources for passive motion of the mandible in expulsion and these are accompanied with changes in swimming speed. They are based on a recoil of hydraulic pressure and resiliency of elastic elements of the ventral pouch. In addition, when the whale ceases propulsive ac- tion, the energy of the frontomandibular stay against the water flow is released and the stored energy of the stay as- sists closure of the mouth (Lambertsen et al., 1995). Therefore, we can summarize the source for the efficient feeding mechanism of the Balaenopteridae as follows: (1) the strong development of the highly elastic elements in the ventral pouch; (2) the multiple muscle layers which serve to deepen the oral cavity; (3) the frontomandibular stay. Feeding strategy of studied specimens The specimens studied display the aforementioned synapomorphies with the balaenopterids, but also show two apomorphic characters, which are clearly different from the Balaenopteridae. Both these characters suggest that en- gulfing is a more active muscular process than in the Balaenopteridae Dorsal ridge.—The specimens studied have a relatively high and elongated dorsal ridge with a concavity at its me- dial side (Figures 1, 2, 4). In MFM18124, there is a roughened area on most of the medial surface of the ridge. This area can be considered as the origin of the caudal part of the mylohyoid muscle. The mylohyoid muscle is only attached along the ventral border in the extant Mysticeti (B. acutorostrata: Pivorunas, 1977, Lambertsen, 1983; B. bore- alis: Schulte, 1916) and the extant Odontoceti (Reidenberg and Laitman, 1994) at the middle part of the mandible. But in ungulates, the muscle is separated into rostral and caudal parts, and the caudal part originates from the medial surface of the mandible just ventral to the alveolar border (Getty, 1975; Sisson, 1975; Nickel et al., 1986). The close relationship between cetaceans and ungulates has been con- firmed by much paleontological and molecular data (e.g., Van Valen, 1966; Shimamura et al., 1997). It appears that cetotheres display the primitive ungulate muscle pattern; the dorsal ridge and allied concavity may indicate the area for the attachment of the mylohyoid muscle. Therefore, zygomatic process of the squamosal x glenoid surface of the squamosal line of the action of a the muscle à © moment arm of the muscle x VS DES à . > ~ x N SA. x an s Figure 7. Schematic diagram showing moment arm of super- ficial portion of masseter muscle (above) and changing of moment arm caused by ventral projection of angle (below). Solid and dashed lines indicate moment arm of muscle and line of action of muscle, re- spectively. the relatively high dorsal ridge with the well-developed concavity of the specimens studied suggests a highly devel- oped mylohyoid muscle, unlike the balaenopterids. The mylohyoid muscle is the largest muscle in the multi- ple muscle layers of the floor of the mouth. The multiple muscle layers of the ventral pouch are the primary con- tributor for active expulsion of water through the baleen (Lambertsen, 1983). In addition, at the final phase of water expulsion, the tongue is forced upwards by contrac- tion of the mylohyoid muscle and this forcibly expels the remaining sea water through the baleen (Lambertsen, 1983). The mylohyoid muscle is primarily an elevator of the tongue (Yamaoka et al., 1992). Thus, the development of the mylohyoid muscle suggests that the studied speci- mens required active musculature for water expulsion dur- ing feeding. Angle.—The angle provides the insertion of the muscles for the movement of the mandibles, such as the medial pterygoid muscle, the digastricus muscle, and the superfi- cial portion of the masseter muscle (Carte and MacAlister, 1868; Schulte, 1916; Lambertsen et al., 1995). The angle of the specimens studied is large and projects ventrally (Figure 1, 2). This is clearly shown by the ratio of mandibular height through angle to mandibular length along outside curvature of the adult individual (converted to percentages): MFM18124 10.3+%; B. acutorostrata 8.5-9.5% (Turner, 1891-1892; Omura, 1975), B. edeni 7.9-9.2% (Omura et al., 1981), B. musculus 8.3-9.3% (Struthers, 1889; Omura et al., 1970), B. borealis 7.6-8.1% (Nishiwaki and Kasuya, 1971), M. novaeangliae 9.1% (Struthers, 1889). The ventrally projected angle implies that the area for the insertion of the muscle is also posi- Feeding strategy of cetothere 187 tioned ventrally. This would increase the moment arm of the superficial masseter and thus improve the mechanical advantage of the mandible (Herring and Herring, 1974; Vizcaino and Bargo, 1998) (Figure 7). Therefore, the morphology of the angle suggests that the specimens stud- ied could produce a more powerful motion of the mandible compared with the balaenopterids. Both of these characters suggest the active contribution of the musculature of the mandible during feeding. This is in marked contrast to the passive contribution of the mus- culature of the mandible in the Balaenopteridae. The sources for the efficient feeding mechanism in the Balaenopteridae have been summarized above. In the specimens studied, the sharply edged ventral margin at the middle part of the mandible and the well-developed inward elevation indicates the development of the mylohyoid mus- cle and therefore the multiple muscle layers and frontomandibular stay, respectively. Therefore the robust contribution of the musculature of the specimens studied can be explained by the lack or poor development of the highly elastic elements in the ventral pouch. Conclusion I propose the following scenario of evolution of the engulfment feeding mechanism in baleen whales. Early mysticetes (aetiocetids) used filter feeding with teeth, and later cetotheres used baleen. Engulfment feeding was pre- sent in Cetotheriidae by the late Early Miocene. However, the feeding mechanism in the Early Miocene cetotheres re- quired more active musculature than in the balaenopterids because of poor development or lack of the highly elastic elements in the ventral pouch. The well developed elastic elements in the skin are highly characteristic and are one of the key structures enabling passive movement of the man- dible in the Balaenopteridae. The elastic elements evolved in the Balaenopteridae and enhanced efficiency of the man- dible. In addition, balaenopterids have lost the apomor- phic characters unrelated to the active musculature of the mandible during engulfment feeding. The feeding strategy suggested by the studied specimens may represent a primi- tive transitional stage of the evolution of the engulfment feeding mechanism. The skull morphology may also exert an influence on the feeding mechanism (McLeod et al., 1993). However, no skull was preserved in both specimens studied, except for a few fragments of the skull in MFM18124. Generally, cetotheres are characterized by primitive skull morphology. The apomorphic characters of the specimens studied which suggests more active contribution of the musculature of the mandible during the feeding process might not only be due to its feeding mechanism, but also to its primitive skull morphology. An additional specimen with a well- preserved skull is needed to address the feeding strategy of the studied specimens in more detail. Acknowledgments This study is a part of my doctoral thesis submitted to the Department of Earth and Planetary Sciences, Graduate School of Science, Nagoya University. I am most grateful to T. Ozawa (Nagoya University) for valuable comments. I gratefully acknowledge the constructive reviews of the manuscript and valuable comments by John E. Heyning (Natural History Museum of Los Angeles County) and J. G. M. Thewissen (Northeastern Ohio Universities). Thanks are extended to anonymous reviewers for their con- structive comments and suggestions. I am indebted to T. K. Yamada (National Science Museum) for valuable com- ments which improved the manuscript and for allowing ac- cess to specimens in his care, to Y. Okumura and H. Karasawa (both Mizunami Fossil Museum) for allowing access to specimens and their assistance, and to T. Kuramochi (National Science Museum) for assistance in observing extant mysticete specimens. This study was supported in part by Grant-in-Aid for JSPS Fellows from the Ministry of Education, Science, Sports and Culture of Japan. References Bakker, M. A. G. de., Kastelein, R. A. and Dubbeldam, J. 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Journal of the Geological Society of Japan, vol. 104, p. 395- 414. 189 ee ie Paleontological Research, vol. 6, no. 2, pp. 191-210, June 28, 2002 © by the Palaeontological Society of Japan Ostracodes from the Inter-trappean beds (Early Paleocene) of the east coast of India SUBHASH CHANDAR KHOSLA AND MADAN LAL NAGORI Department of Geology, Mohan Lal Sukhadia University, Udaipur 313002, India Received October 26, 2000; Revised manuscript accepted March 15, 2002 Abstract. Twenty-seven ostracode species from the Inter-trappean beds (Paleocene) of Duddukuru, West Godavari District, Andhra Pradesh, east coast of India are recorded and/or described. Nine species —Cytheromorpha godavariensis, Cytherura duddukuruensis, Hapsicytheridea undulata, Krithe bhandarii, Para- candona andhraensis, Munseyella indica, Neomonoceratina paraoertlii, Semicytherura diluta, and Uroleberis rasilis— are new. The identification of 6 species, previously described from the east coast of India, and also recorded in this work, are revised. The stratigraphic distribution, age and affinity and paleoecology of the ostracode fauna are also discussed. Key words: Duddukuru, East Coast of India, Inter-trappean beds, Ostracodes, Paleocene Introduction The Inter-trappean beds of the east coast of India are a key marker horizon in the stratigraphy of the country. They are of great significance in fixing the age limits of the Deccan Traps, at least those of this part of the peninsula, with which these beds are closely associated. This is be- cause of their unique stratigraphic position (Table 1) and the prolific marine microfauna they contain. There are, however, varied opinions about the age of the Inter- trappean beds and vis a vis of the associated Deccan Traps. Most of the earlier workers until the nineteen seventies considered the Inter-trappean beds as Tertiary in age, rang- ing from Paleocene to Eocene (Hislop in Hislop et al., 1860; Sahni, 1934; Rao and Rao, 1935, 1937a, 1937b; Rao et al., 1936; Rao, 1956; Sastri, 1961; Bhalla, 1967). However, these views changed markedly in the nineteen eighties during which the Deccan volcanism was demon- strated to be a major Cretaceous-Tertiary boundary (KTB) event (Courtillot et al., 1986, 1988, 1990; Baksi, 1987; Duncan and Pyle, 1988; Hallam, 1988; Sahni and Bajpai, 1988). Govindan (1981) using foraminifera from the Inter-trappean sediments from Narsapur-1 well section from Krishna-Godavari (KG) Basin (of which the present area of Duddukuru under study is a part) assigned the Deccan Traps of this well to late Maastrichtian, emplaced between 70-67 Ma. Subsequently, Raju er al. (1991, 1994, 1995), Jaiprakash et al. (1993), Saxena and Mishra (1994), and Mishra et al. (1994) studied foraminifera, cal- careous nannoplankton and dinoflagellate cysts from more well sections from the K-G Basin. The data suggest that the volcanism began during 65.5 to 65 Ma (considering KTB at 65 Ma, Sharpton ef al., 1992) in the terminal Cretaceous and continued across the KTB into the early Paleocene. The microfauna of the Inter-trappean beds of the east coast of India comprises mainly foraminifers and ostracodes. A survey of the literatures reveals that impor- tant contributions on these foraminifers have been made by Rao and Rao (1937a), Sastri (1961), Bhalla (1967), Govindan (1981), Raju and Dave (1993), and Jaiprakash et al. (1993), while on ostracodes by Jain (1978) and Bhandari (1995). With the intention of working on the ostracode fauna of the Inter-trappean beds of the east coast of India the authors collected samples of these beds from two sections. The lo- cation of the sections is given below and also in Figure 1. Section I is from a limestone quarry, belonging to M/S Facor Ltd., about 1 km south of the village of Duddukuru (17° 2° 15” N: 81° 35° 30°” E) on the Eluru-Kovvur Road, West Godavari District, Andhra Pradesh, east coast of India. Section II is from an abandoned quarry about 2 km southeast of Duddukuru. Both sections yielded a prolific, well preserved ostracode fauna much richer than those re- ported by Jain (1978) and Bhandari (1995). The assem- blage comprises a total of 27 species including 9 new ones and a number of species being reported for the first time from the region. This has necessitated revising the ostracode fauna of the Inter-trappean beds of the east coast of India. A new genus Costabuntonia has recently been 192 Subhash Chandar Khosla and Madan Lal Nagori proposed for the species previously described as Protobuntonia hartmanni Jain (Khosla, 1999). Previous work Among the earlier works on the ostracode fauna from the Inter-trappean beds of the east coast of India, an important contribution was made by Sastri (1961 and 1963) who reported the occurrence of nine species from these beds at Kuntamuru village near Rajahmundry. These species are Cytherella sp., Cytheropteron sp., ?Eucythere sp., Loxo- concha sp., Bairdia subdeltoidea (Münster), Cythere (?Xestoleberis) ranikotiana Latham, Cythereis bowerbanki Jones, Cythereis cf. mersondaviesi Latham, and Cytherel- loidea sp. Of these only the last five species were described and illustrated in his 1963 paper while the specific name Cythere (?Xestoleberis) ranikotiana was modified as Cythere ranikotiana. Bhalla (1965) recognised 16 ostra- code species from Pangadi, Andhra Pradesh. These are: Brachycythere sp., Bythocypris sp., Costa sp., Cytherella sp., Cytheretta [possibly C. laticostata (Reuss)], Hermani- tes sp. A, H. sp. B, Krithe [provisionally identified as K. bartonensis (Jones)], Leguminocythereis sp. A, L. sp. B, Neocyprideis sp., Occultocythereis sp., Quadracythere sp., ?Schizocythere sp., Semicytherura [provisionally identified as S. forestensis (Keij)], and Xestoleberis [provisionally identified as X. subglobosa (Bosquet)]. Their stratigraphic distribution and paleoecologic significance were given in his subsequent paper (Bhalla, 1967). Bhalla (1979a-c, 1980) described and illustrated the following new species from the Pangadi area: Hermanites sastryi, Loxoconcha singhi, Occultocythereis elongatum, and Quadracythere tewarii. Guha (1970) recorded Cythereis cf. tamulicus, Hermani- tes cf. pondicheriensis, Paracypris sp., Protobuntonia sp, Xestoleberis sp., and the genus Ovocytheridea. Jain (1978) described and illustrated twelve ostracode species from Kateru, Rajahmundry. Of these two species, Ovocytheridea raoi and Protobuntonia hartmanni are new, the other species represented being “Bairdia” sp. indet., ?Bythocypris sp. indet., Cytherella sp. cf. münsteri (Roemer), Cytherelloidea sp. cf. C. keiji McKenzie, 7“Cytheridea” sp. indet., Hermanites sp. cf. H. cracens Siddiqui, Limnocythere sp. indet., Loxoconcha sp. indet., Quadracythere (Hornibrookella) subquadrata Siddiqui, and ?Xestoleberis sp. indet. Bhandari (1995) recorded 15 species from the Inter- trappean beds near Duddukuru, Andhra Pradesh. Of these four species — Cushmanidea bhatiai, Cytherella mohani, Cytheridella rajahmundryensis and Palmoconcha rajui are new. The other species reported are Bythocypris? sp., Cytherelloidea sp. cf. C. keiji McKenzie, Cytheridella sp., Gyrocythere sp. cf. G. parvicarinata Siddiqui, Hermanites sastryi Bhalla, Hermanites sp., Hornibrookella tewarii (Bhalla), Nucleolina diluta Al-Furaih, Ovocytheridea raoi Jain, Protobuntonia hartmanni Jain, and Xestoleberis sp. Stratigraphy The geology of the region, along with a detailed map, has been adequately described by Bhalla (1967) and this has been followed in this work. The Inter-trappean beds are set of sedimentary strata composed mainly of limestone with shale/claystone intercalations lying in between the Deccan trap. The generalised stratigraphy of the coastal tract of the Krishna-Godavari districts, Andhra Pradesh is summarised in Table 1 (for details see references in Ramam and Murty, 1997). The Intra-trappean beds have a gentle dip of 4 to 6 de- grees towards the southeast and thickness varying from less than a meter to a little over 9 meters. The samples from which the present ostracode fauna was obtained come from the two sections. The sequence of these sections is given in Tables 2 and 3. Materials and methods The samples were broken into small pieces and boiled for 3-4 hours in water to which one or two tablespoons of soda ash were added. The disintegrated material was wet screened through set of sieves of 30, 80, and 150 mesh size. The dried, washed residue was uniformly spread on a pick- ing tray and scanned under a stereozoom microscope. The ostracodes present were hand picked with a fine sable-hair brush and arranged in assemblage slides. The type speci- mens were photographed on Jeol SEM using ORWO 120, black and white 100 ASA film A total of 4,040 ostracodes were picked up, counting both complete cara- paces and open valves as individual specimens. Their dis- tribution is given in Table 4 and all the species recognized in this work are illustrated in Figures 2-5. Composition, age and affinity of ostracode fauna The ostracode fauna of the Inter-trappean beds of Duddukuru comprises 27 species (Table 1). These belong to 13 families, 4 species each to the families Cytherellidae, Cytheridae, and Cytheruridae, 3 species each to the families Hemicytheridae and Trachyleberididae, two species to the family Xestoleberididae, and one species each to the fami- lies Bairdiidae, Candonidae, Cushmanidae, Cytherideidae, Krithidae, Limnocythereidae and Loxoconchidae. An analysis of these is given below. 1. Three species are left under open nomenclature and nine species are considered new. These are of little use in age interpretation at present. Paleocene ostracodes from India 193 Table 1. Generalized stratigraphy of the coastal tract of the Krishna- Godavari districts, Andhra Pradesh. Age Formation Quaternary Alluvium Mio-Pliocene Late Maastrichtian-Early Paleocene Late Maastrichtian Late Cretaceous Early Cretaceous Triassic-Jurassic Rajahmundry Formation Deccan Trap with Inter-trappean beds Infra-trappean Limestone Tirupati Formation Raghavapuram Formation Kota Formation (Upper Gondwana) Permian Kamthi Formation (Lower Gondwana) Archean Khondalite Table 2. Stratigraphic succession of Section I. Sample No. Lithology Thickness in meters Black colored basalt 1.2 Grey shale 0.45 Red shale 0.45 V10-11 Light yellow limestone 2 1/9 Yellowish grey clay 0.15 18 Light yellow limestone 0.76 V6-7 Yellowish grey clay 0.25 14-5 Brownish yellow marl 0.3 1/3 Grey clay 0.3 V2 Greyish white clay 0.25 vi Light yellow limestone 2.44 Black colored basalt Base not exposed Table 3. Stratigraphic succession of Section II. Sample No. Lithology Thickness in meters IV6-8 Greyish white limestone 0.81 IV5 Grey clay 0.38 IV1-4 Light yellow limestone 1.22 Base not exposed 2. Eight species, Costabuntonia hartmanni (Jain), Cush- manidea bhatiai Bhandari, Cytherella mohani Bhandari, Falsocythere elongata (Bhalla), Hermanites sastryi Bhalla, Hornibrookella tewarii (Bhalla), Neocyprideis raoi (Jain), and Palmoconcha rajui Bhandari, have so far been known only from Duddukuru (Jain, 1978; Bhalla, 1979b, c, 1980; Bhandari, 1995). 3. One species, Xestoleberis subglobosa (Bosquet), has been recorded widely from the Eocene beds of France, Belgium, Netherlands (Keij, 1957) and also from the Middle Eocene of Kachchh, western India (Guha, 1968; Khosla and Pant, 1988), Himachel Pradesh, northern India (Mathur, 1969) and the Lower Eocene of Rajasthan, west- ern India (Khosla, 1972). 4. One species, Bairdia beraguaensis Singh and Tewari, has previously been recorded from the Early Eocene beds of Jammu and Kashmir (Tewari and Singh, 1966), Pakistan (Sohn, 1970), Rajasthan (Khosla, 1972), Meghalaya (Singh, 1984) and from the Middle Eocene beds of Assam (Neale and Singh, 1985). 5. Three species, Cytherelloidea bhatiai Guha and Shukla, Paijenborchellina indica (Khosla) and Paracypris khuialaensis Bhandari, have been described from the Early Eocene beds, the first from Vridhachalam, Tamilnadu, southern India (Guha and Shukla, 1974), the other two from Rajasthan (Khosla, 1972; and Bhandari, 1996). P. indica has also been reported from Kachchh (Khosla and Pant, 1988). 6. Two species, Holcopocythere bassiporosa Al-Furaih and Nucleolina diluta Al-Furaih, have been recorded from the latest Cretaceous and Early Paleocene beds of Saudi Arabia (Al-Furaih, 1980). From the analyses given above it is apparent that the ma- jority of the ostracodes are either new or have so far been known from the Inter-trappean beds of the east coast of India. One species, X. subglobosa, occurs widely in the Eocene beds. Four species, B. beraguaensis, C. bhatiai, P. indica, and P. khuialaensis, were originally reported from the lower Eocene beds, and two species, H. bassiporosa and N. diluta, are characteristic of Early Paleocene age. So far as the Early Eocene species are concerned, it is feared that the stratigraphic horizons from where the occur- rences of these species were reported; i.e. Fuller’s Earth at Palana, Bikaner District, Rajasthan (Khosla, 1972), Kakdi Stage, Kachchh District (Khosla and Pant, 1988), and sub- surface samples from Vridhachalam District (Guha and Shukla, 1974), have not been precisely dated on the basis of planktonic foraminifers and might be of Paleocene age. The presence of H. bassiporosa and N. diluta in the Inter- trappean beds of the east coast of India is suggestive of an Early Paleocene age for the beds. This is in conformity with the views of Bhandari (1995), who has proposed an Early Paleocene age for these beds on the basis of similarity of their ostracode fauna with the ostracodes of the Karimpur Member of the Ghatal Formation of Dhananjapur Well No. 1, West Bengal Basin. In the Karimpur Member ostracodes are associated with a few planktonic foraminifers like Morozovella pseudo- bulloides and smaller benthics like Protelphidium adamsi, Discorbis midwayensis var. soldadoensis etc., suggesting an Early Paleocene (Danian) age (= IPB on Planktic scale). Paleoenvironments The Inter-trappean beds of the Rajahmundry area (as is true of other coastal formations in India) are the result of a marine transgression, which took place in Early Paleocene times. The paleoenvironment of the beds is discussed on the basis of evidence furnished by ostracodes. 194 Subhash Chandar Khosla and Madan Lal Nagori Table 4. Distribution of ostrocodes in the Inter-trappean beds of the east coast of India. Sample number Horizon Section I Section II Total 1226 Seat ST Or WE ION L'INDE SECTE Bairdia beraguaensis Singh & Tewari l l Costabuntonia hartmanni (Jain) DA 2) BAD 3 16 6 82 Cushmanidea bhatiai Bhandari 2 1 1 10 4 18 Cytherella mohani Bhandari 3 11 6 20 Cytherella sp. A 4 4 Cytherella sp. B 1 1 Cytherelloidea bhatiai Guha & Shukla 1 > I 7 Cytheromorpha godavariensis sp. nov. 2 is 7s) 3 127 Cytherura duddukuruensis sp. nov. 3 28 © 8 106 136 18 309 Falsocythere elongata (Bhalla) 4 1 35 40 Paijenborchellini gen. et sp. indet. A 22 ve 3 Hapsicytheridea undulata sp. nov. l 2 34 6 37 164 105 4 Il 364 Hermanites sastryi Bhalla 6 10 al 3 4 7 38 3 102 Holcopocythere bassiporosa Al-Furaih 18 2 4 24 Hornibrookella tewarii (Bhalla) 16 24 2 4 69 33 148 Krithe bhandarii sp. nov. A DSK). BIS 17 264 Munseyella indica sp. nov. 1 6 7 Neocyprideis raoi (Jain) 85 203 304 418 38 53 12 10 211 360 130 41 69 1934 Neomonoceratina paraoertlii sp. nov. l 39 143 92 275 Nucleolina diluta Al-Furaih 8 10 18 Paijenborchellina indica (Khosla) 24 24 Palmoconcha rajui Bhandari DS 3 » Si & 2 6 4 38 119 Paracandona andhraensis sp. nov. 10 10 Paracypris khuialaensis Bhandari 8 4 4 16 Semicytherura diluta sp. nov. 3 63 14 110 Uroleberis rasilis sp. nov. 3 3 Xestoleberis subglobosa (Bosquet) 3 7 10 TOTAL 0 0 10 85 211 344 430 40 157 162 40 383 1017 664 4 0 45 339 109 4040 Section I the genera Costabuntonia, Genus A, Holcopocythere and In Section I ostracodes make their first appearance in grey clay (Sample No. 3) where they are represented by a solitary species of Paracandona. The underlying beds, in ascending order, light yellow limestone (Sample No. 1) and greyish-white clay (Sample No. 2) are devoid of ostracode fauna. Paracandona is a characteristic freshwater genus. Its occurrence in the grey clay suggests that the bed might have accumulated in a similar environment. In the succeeding brownish-yellow marl (lower part, Sample No. 4) appears a species of Neocyprideis, which occurs commonly in it. Soon, however, the species be- comes enormously abundant in the overlying beds. In brownish-yellow marl (upper part, Sample No. 5) it consti- tutes 97% of the entire ostracode assemblage, while in yellowish-grey clay, sample Nos. 6 and 7, it forms 84% and 98% respectively. The other ostracodes present in their order of predominance are Hermanites, Costabuntonia, Holcopocythere, Genus A, Palmoconcha, Cytheromorpha, Hapsicytheridea and Neomonoceratina. Of these ostracodes, little is known about the ecology of Hapsicytheridea as they do not occur in the present day. The genera Hermanites and Neomonoceratina are epineritic and the genus Cytheromorpha is characteristic of meso- haline to littoral environments (Morkhoven, 1963). A Recent species of Palmoconcha has been described by Swain and Gilby (1974) from Station I, Bahia Sebastian Vizcaino, Baja California at a depth of 59 m. The genus Neocyprideis is closely related to the living genus Cyprideis, which probably evolved from it (Morkhoven, 1963). The latter genus inhabits freshwater to hypersaline conditions, but is most abundant in mesohaline salinities and hence is regarded as the most typical brackish-water ostracode. According to Keij (1957), Morkhoven (1963), Oertli (1967), Keen (1977) and Neale (1988), Neocyprideis also occurs predominantly in brackish-water environments. Keen (1977) records the genus from three brackish-water assemblages, maximum predominance being in assemblage IV of the Upper Eocene beds of the Hampshire Basin, U. K. Assemblage IV is taken to represent salinities of 9.0 to 16.5%. Neale (1988) has observed that minimum di- Paleocene ostracodes from India 195 Location of the Sections studied Bay of Bengal Figure 1. versity of species and abundance of individuals and reached in low brackish-water environments. In the present Sample Nos. 4-7 of Section I Neocyprideis constitute a very high proportion of the ostracode assemblages (84 to 100%) and other ostracodes together form small fractions, suggesting that the brownish yellow marl and yellowish- grey clay were deposited in a mesohaline (9 tol6.5%c), outer bay environment. There is a sharp decline both in diversity as well as fre- quency of ostracode fauna in the overlying light yellow limestone (Sample No. 8). Only two species of Neocypri- deis and Costabuntonia are encountered in this bed sug- gesting a temporary shallowing of the basin, and the bed might have been deposited in the marginal estuarine envi- ronments. This view is further corroborated by disappear- ance of foraminifers except for some Nonion. Megafossils are represented by Ostrea, characteristic of near-shore envi- ronments. There was again an influx of a large number of ostracode species in the succeeding yellowish-grey clay (Sample No. 9) and light yellow limestone (Sample Nos. 10 and 11). The ostracodes in order of predominance are : Neocypri- deis, Palmoconcha, Cytherura, Costabuntonia, Hermani- Index map of part of Andhra Pradesh showing locations of the sections studied. tes, Hapsicytheridea, Hornibrookella, Krithe, Cushmani- dea, Cytherelloidea, Cytheromorpha, Falsocythere, Holco- pocythere, Munseyella and Xestoleberis. Of these, eight genera appear for the first time. Their ecological signifi- cance is as follows. The genus Hornibrookella is extinct and therefore little is known about its ecology. The genus Cytherelloidea inhabits shallow, warm marine waters; oc- casionally it is also found in brackish-water (mesohaline) environments (Morkhoven, 1963). According to Sohn (1964), the genus is a good paleotemperature indicator and in the present-day seas it does not survive in temperatures less than 10 °C. The genus Cytherura inhabits mesohaline to littoral environments (Morkhoven, 1963). The genus Falsocythere is a shallow marine form. A living species of the genus has been described from the coastal waters of the Adriatic Seas by Bonaduce er al. (1975) and the Gulf of Aquaba (Red Sea) by Bonaduce er al. (1980). There is some difference of opinion about the ecology of the genus Krithe. According to van den Bold (1960), it occurs in a near-shore as well as an open-shore facies, while Morkhoven (1963) is of the view that the genus is strictly marine and most commonly occurs in infraneritic to bathyal environments. The genus Munseyella thrives well in an 196 Subhash Chandar Khosla and Madan Lal Nagori epineritic environment predominantly in warmer waters (Morkhoven, 1963). Studies of living species of Cushmanidea by Ascoli (1964) and McKenzie and Swain (1967) suggest that the genus inhabits lagoonal to shallow- water environments. Keen (1977) records it from the as- semblage V (polyhaline, 16.5 to 33%c) of the Upper Eocene beds of Hampshire, U.K. Ecological significance of the genera Neocyprideis, Palmoconcha, Hermanites and Cytheromorpha has already ‘been discussed. In the present beds under discussion the frequency of Neocyprideis declines considerably as com- pared to underlying beds (Sample Nos. 4 to 7) and the ap- pearance of a number of marine genera suggests that the yellowish-grey clay and light yellow limestone might have been deposited in a polyhaline bay (16.5 to 33 %o). Section II The section II is only 2.41 meters thick and comprises, in ascending order, light yellow limestone (Sample Nos. | to 4), grey clay (Sample No. 5) and greyish-white limestone (Sample Nos. 6-8). The ostracode fauna in the section is much varied and of high frequency in the lower and upper limestone beds, but absent in the middle grey clay. This succession corresponds with the upper part of the succes- sion in Section I (i.e. yellowish-grey clay and light yellow limestone). The paleoecology of the ostracodes in Section II is discussed below. The ostracodes in the light yellow limestone (Sample Nos. 1-4) in their order of predominance are Neocypri- deis, Hapsicytheridea, Neomonoceratina, Cytherura, Krithe, Cytheromorpha, Semicytherura, Costabuntonia, Cushmanidea, Palmoconcha, Hermanites, Paracypris, Cytherella, Falsocythere, Holcopocythere and Hornibrookella. The genera Cytherella, Paracypris and Semicytherura appear for the first time in this bed. These are essentially marine genera (Morkhoven, 1963). The genus Cytherella occurs at all depths and rarely is also found in brackish- water (mesohaline) environments. The genus Paracypris mainly occurs in deeper water but is very rare in occur- rence, and hence may not be of much significance. The genus Semicytherura is epineritic, predominantly littoral. The high diversity of shallow marine genera and presence of Neocyprideis in large numbers suggest that the limestone bed might have accumulated in a polyhaline-bay, brackish- water environment similar to the top two beds of Section I. The overlying grey clay (Sample No. 5) is devoid of ostracodes. Possibly there was a temporary shallowing of the basin and the bed was deposited in marginal estuarine environments similar to the light yellow limestone (Sample no. 8) of Section I. The succeeding greyish white limestone is again rich in ostracode fauna. It is represented in order of dominance by Hornibrookella, Neocyprideis, Costabuntonia, Her- manites, Falsocythere, Palmoconcha, Cytherella, Cythe- rura, Hapsicytheridea, Krihe, Xestoleberis, Paijen- borchellina, Cytherelloidea, Nucleolina, Bairdia, Cush- manidea, Munseyella, Paracypris and Uroleberis. The genera Paijenborchellina, Nucleolina, Bairdia and Uroleberis appear for the first time in this bed. The genus Nucleolina does not extend in the present day. Therefore little is known about its ecological significance. Studies of certain living species of the genus Paijenborchellina from the Abu Dhabi lagoon, Persian Gulf (Bate, 1971) show that it occurs from littoral to near-shore shelf environments. The genus Bairdia is a characteristic marine form occurring both in very shallow as well as very deep waters (Morkhoven, 1963). In the present day the genus Uroleberis occurs in epineritic environments (Morkhoven, 1963). The ecological significance of other genera has al- ready been discussed. Like the light yellow limestone (Sample Nos.1-4) of Section II and the upper two beds of Section I, the present bed is characterised by varied shallow marine ostracodes, suggesting that it was also deposited in a polyhaline bay. The paleoenvironmental inferences drawn above are more or less similar to those of Bhalla (1967) and Bhandari (1995) who also worked on the Inter-trappean beds of this region. According to Bhalla (1967), the foraminiferal and ostracode assemblages reflect rhythmic facies changes with alternate brackish-water and normal marine environments of deposition. He also recorded two marine incursions in the area. Bhandari (1995) inferred that the Inter-trappean beds of Duddukuru were deposited in brackish-water to shallow inner neritic conditions around 0-10 m deep with intermittent freshwater conditions. Systematic paleontology The classification of ostracodes in this paper follows that of Hartmann and Puri (1974). Descriptions of already known and well established species are omitted for the sake of brevity. The illustrated specimens are deposited in the museum of the Department of Geology, Mohan Lal Sukhadia University, Udaipur and catalogued with the pre- fix SUGDMF. Order Podocopida Suborder Platycopa Family Cytherellidae Genus Cytherella Jones, 1849 Type species.—Cytherina ovata Roemer, 1840. Paleocene ostracodes from India 197 Cytherella sp. A Figure 2.3 Cytherella sp. cf. muensteri (Roemer). fig. 1. Jain, 1978, p. 52, pl. 1, Material.—Four carapaces. Remarks.—The species was recorded as Cytherella sp. cf. muensteri by Jain (1978) from the Inter-trappean beds of Kateru, Rajahmundry. It, however, differs from Cythe- rella muensteri (Roemer) in having an angulated dorsal margin, the greatest height located near the middle, and a smooth surface. C. muensteri, in contrast, has the greatest height located at the posterior 1/3 of the length, has a pitted surface, and lacks the dorsal angulation. The species is left under open nomenclature. Dimensions. — A carapace, SUGDMF no. 565, length 0.69 mm, height 0.42 mm, width 0.27 mm. Occurrence.—Section II. Cytherella sp. B Figure 2.4 Material.— One carapace. Description.— Carapace subrectangular in lateral out- line; height equal in anterior and posterior halves; right valve slightly overlaps left valve along dorsal and ventral margins; dorsal margin nearly straight; ventral margin slightly concave, anterior and posterior margins rounded; valve surface smooth. Remarks.—This species differs from Cytherella mohani Bhandari, 1995 and Cytherella sp. A recorded herein in the lateral outline and degree of overlap. C. mohani is subovate in shape with a pronounced overlap, while Cytherella sp. A is an elongate form having an angulated dorsal margin. The present species is left under open no- menclature. Dimensions.— A carapace, SUGDMF no. 566, length 0.74 mm, height 0.42 mm, width 0.32. Occurrence.—Section II. Genus Cytherelloidea Alexander, 1929 Type species. — Cythere (Cytherella) williamsoniana Jones, 1849. Cytherelloidea bhatiai Guha and Shukla, 1974 Figure 2.5 Cytherelloidea bhatiae Guha and Shukla, 1974, p. 96, 97, pl. 2, fig. 10. Cytherelloidea sp. cf. C. keiji McKenzie. Jain, 1978, p. 52, 53, pl. 1, figs. 2, 3. Bhandari, 1995, p. 94, pl. 1, fig. 3. Material.—Seven carapaces. Description.—Carapace subrectangular in lateral outline, with height equal in both anterior and posterior halves; valve surface ornamented by elongate punctation; two prominent, sinuate, transverse ridges extending three- fourths of length joined by a posterior vertical ridge; and marginal rim along dorsal, anterior and ventral margins. Remarks.—The present specimens from Duddukuru are referred to Cytherelloidea bhatiai Guha and Shukla (1974) (species name misspelled as bhatiae) described from the Lower Eocene of Gopurapuram well, Vridhachalam, Tamilnadu. The form described as Cytherelloidea sp. cf. C. keiji from the Inter-trappean beds of the east coast of India by Jain (1978) and Bhandari (1995) belongs to this species. According to McKenzie et al. (1990) Keijcyoidea keiji (earlier referred to Cytherelloidea) is a Pleistocene- Recent species ranging in distribution from the southwest- ern Pacific to northwestern and southern Australia. Dimensions.— A carapace, SUGDMF no. 567, length 0.48 mm, height 0.29 mm, width 0.21mm. Occurrence.—Sections I and II. Suborder Podocopa Superfamily Cytheracea Family Cytheridae Subfamily Cytherinae Tribe Cytherini Genus Cytheromorpha Hirschmann, 1909 Type species.—Cythere fuscata Brady, 1869. Cytheromorpha godavariensis sp. nov. Figure 2.7-2.9 Etymology.—After the Indian River Godavari. Material.—124 carapaces and 3 valves. Type locality. — Light yellow limestone (Sample SUGDMF no. 3/II), Inter-trappean beds, Paleocene. Section II. Diagnosis.—Surface strongly reticulate and with a trans- verse median ridge. Description. —Carapace subquadrate in lateral outline, with greatest height at anterior cardinal angle; overlap in- distinct; valve inflated ventrally; dorsal margin straight converging posteriorly; ventral margin obscured medially; anterior margin broadly rounded; posterior margin much narrower, subangulate near mid-height; in dorsal view cara- pace somewhat biconvex, both ends taper, more in poste- rior than in anterior, maximum width posterior to middle. Valve surface strongly reticulate, edges of reticulation meshes in anterior half raised in low costae; a transverse ridge in median region. Inner lamella moderately wide along anterior and posterior margins and narrows ventrally; Subhash Chandar Khosla and Madan Lal Nagori 198 Paleocene ostracodes from India 199 vestibule present; selvage near outer periphery; normal pores few, widely spaced. Hinge gongylodont; in left valve it consists of an indistinct socket surrounded by a crenulate anterior tooth, which is a continuation of the me- dian crenulate bar and a posterior socket with a distinct tooth at its inner edge. Dimensions.—Holotype, SUGDMF no. 569, a carapace, length 0.30 mm, height 0.19 mm, width 0.14 mm; paratype I, SUGDMF no. 570, a left valve, length 0.32 mm, height 0.19 mm; paratype II, SUGDMF no. 571, a carapace, length 0.30 mm, height 0.18 mm, width 0.16 mm. Discussion.—Cytheromorpha godavariensis sp. nov. re- sembles Cytheromorpha kirtharensis Guha (1968) de- scribed from the Middle Eocene of Kachchh in general appearance. C. kirtharensis, however, differs from the present species in having concentrically arranged reticula- tion and a lack of median transverse ridge. Cythero- morpha bulla Haskin (1971) described from the Tertiary beds of the Isle of Wight also resembles C. godavariensis Sp. nov. in overall lateral outline and surface ornamentation but differs in having three distinct vertical ridges in the an- terior half. Occurrence.—Sections I and II. Tribe Pectocytherini Genus Munseyella van den Bold, 1957 Type species.—Toulminia hyalokystis Munsey, 1953. Munseyella indica sp. nov. Figure 2.10, 2.11 Etymology.—After the country of India. Material.—Six carapaces and one valve. Type locality. — Greyish-white limestone (Sample SUGDMF no. 7/Il), Inter-trappean beds, Paleocene. Section II. Diagnosis.—Surface ornamented by ridges and vertically arranged pits. Description.—Carapace subquadrate in lateral outline, with greatest height about half of length at anterior cardinal angle; posterior cardinal angle well marked; valves almost equal; dorsal margin nearly straight, sloping down posteriorly; ventral margin concave; anterior margin broadly rounded; posterior straight, nearly perpendicular to ventral margin; anterior margin fringed with 6 or 7 spines and posterior margin with two spines, one at mid-posterior and the other at posteroventral region; in dorsal view cara- pace rather compressed. Valve surface ornamented by an- terior marginal ridge which also continues ventrally slightly above margin; a dorsal ridge extending from anterior cardi- nal angle backward overhanging margin, in posterodorsal region it turns downward forming a thick knob; two short furcating transverse ridges, one in posteromedian-median region and the other in ventromedian-anteroventral region; a vertical ridge extending downward from anterodorsal re- gion; vertically arranged deep elongate pits over rest of area. Dimensions. — Holotype, SUGDMF no. 572, a right valve, length 0.38 mm, height 0.21 mm; paratype, SUGDME no. 573, a carapace, length 0.42 mm, height 0.22 mm, width 0.19 mm. Discussion.—The. species closely resembles Munseyella japonica (Hanai, 1957), a Recent species from Kanagawa Prefecture, Japan in overall shape but differs in surface ridge pattern and having vertically arranged, elongate pits. Occurrence.—Sections I and II. Tribe Paijenborchellini Genus Neomonoceratina Kingma, 1948 Type species.—Neomonoceratina columbiformis King- ma, 1948. Neomonoceratina paraoertlii sp. nov. Figure 3.1, 3.2 Etymology.— From Greek para, meaning “beside,” with reference to its resemblance with Neomonoceratina oertlii Guha, 1967. Material.—275 carapaces. Type locality. — Light yellow limestone (Sample SUGDMF no. 3/Il), Inter-trappean beds, Paleocene. Section II. Diagnosis.—Surface distinctly reticulate, meshes with 5 or 6 pores, and a depression between ventral ridge and mar- gin. Description.—Carapace elongate, subrectangular in lat- eral outline, height almost equal in anterior and posterior halves; overlap indistinct; dorsal margin nearly straight @ Figure 2. 1, 2. Cytherella mohani Bhandari. |, carapace, SUGDMF no. 563, left valve view, x78; 2, carapace, SUGDMF no. 564, dorsal view, x80. 3. Cytherella sp. A, carapace, SUGDMF no. 565, left valve view, x83. x81. 5. Cytherelloidea bhatiai Guha and Shukla, carapace, SUGDMF no. 567, left valve view, «123. 4. Cytherella sp. B, carapace, SUGDMF no. 566, left valve view, 6. Bairdia beraguaensis Singh and Tewari, carapace, SUGDMF no. 568, right valve view, x76. 7-9. Cytheromorpha godavariensis sp. nov. 7, holotype, SUGDMF no. 569, carapace, right valve view, x210; 8, paratype I, SUGDMF no. 570, left valve, internal view, x200; 9, paratype II, SUGDMF no. 571, carapace, dorsal view, x213. 10, 11. Munseyella indica sp. nov. 10, holotype, SUGDMF no. 572, right valve, lateral view, x166; 11, paratype, SUGDMF no. 573, carapace, dorsal view, x152. view, x81. 12. 13. Neocyprideis raoi (Jain). 12, carapace, SUGDMF no. 579, right valve view, x80; 13, left valve, SUGDMF no. 580, internal 200 Subhash Chandar Khosla and Madan Lal Nagori Paleocene ostracodes from India 201 anteriorly and with a distinct hump posteriorly, obscuring margin; ventral margin straight; anterior margin broadly rounded; posterior margin less so; in dorsal view ends com- pressed, sides more or less parallel. Eye tubercle present. Valve surface marked by a shallow depression in mid- dorsal and dorsomedian regions; distinct reticulation, meshes mostly quadrangular in shape and with 5 or 6 pores; three feeble longitudinal ridges, median ridge extending from mid-anterior region to posteromedian region, ventral ridges nearly parallel, sloping up and back from mid- ventral region; and a prominent depression between ventral ridge and margin. Internal characters not known. Dimensions.—Holotype, SUGDMF no. 574, a carapace, length 0.42 mm, height 0.19 mm, width 0.18 mm; paratype, SUGDME no. 575, a carapace, length 0.40 mm, height 0.19 mm, width 0.19 mm. Discussion. — The species very closely resembles Neomonoceratina oertlii Guha (1967) from the Miocene of Saurashtra, Gujarat in lateral outline and overall surface ornamentation. The latter species, however, differs in being much larger in size and having a distinct vertical sulcus. Occurrence.—Sections I and II. Paijenborchellini gen. et sp. indet. A Figure 3.3-3.5 Material.—One carapace and two valves. Description.—Carapace elongate, subtrapezoidal in lat- eral outline, with greatest height about half of length at an- terior cardinal angle; left valve slightly overlaps right valve along anterodorsal and posteroventral margins; valves somewhat inflated ventrally, overhanging margin in median and anteroventral region; dorsal margin straight, converg- ing backward; posterior cardinal angle well marked; ante- rior margin broad, obliquely rounded and fringed with 5 large, downwardly curved spines; posterior margin drawn out ventrally and fringed with two spines; in dorsal view carapace sagittate, distinctly compressed near anterior and posterior ends. Valve surface strongly tuberculate, super- imposed by punctation, and marked by a row of about 10 tubercles extending from mid-anterior to mid-ventral re- gion, with a subcentral swelling and a vertical sulcus poste- rior to it. Inner lamella moderately wide; line of concrescence and inner margin coincide; selvage periph- eral; normal pore widely scattered; central muscle scars comprise a vertical row of four scars, lowest being largest, frontal scar not known. Hinge schizodont; in left valve it consists of an anterior socket with two loculi, a postadjacent bilobate anteromedian tooth, a long crenulate posteromedian bar and a large posterior socket, open interiorly; hinge complementary in right valve, anterior tooth bilobate, posterior tooth indistinctly crenulate. Remarks.—The species probably belongs to a new genus but no name is proposed because of insufficient material. Dimensions. — À carapace, SUGDMF no. 576, length 0.62 mm, height 0.32 mm, width 0.27 mm; a left valve, SUGDME no. 577, length 0.62 mm, height 0.32 mm; a right valve, SUGDMF no. 578, length 0.61 mm, height 0.32 mm. Occurrence.— Section I. Family Cytherideidae Subfamily Cytherideinae Genus Neocyprideis Apostolescu, 1957 Type species. —Cyprideis (Neocyprideis) durocortorien- sis Apostolescu, 1957. Neocyprideis raoi (Jain, 1978) Figure 2.12, 2.13 Ovocytheridea raoi Jain, 1978, p. 53, pl. 1, figs. 7-10; Bhandari, 1995, p. 95, 96, pl. 2, figs. 1, 2. Material.—1134 carapaces and 800 valves. Remarks.—The species has previously been described as Ovocytheridea raoi Jain (1978) from the Inter-trappean beds of Kateru, Rajahmundry and from Duddukuru, West Godavari District, Andhra Pradesh (Bhandari,1995). This is the most abundant species in our collection and in certain samples it constitutes up to 90 percent of the total ostracode population. Ovocytheridea is essentially a Cretaceous genus and the majority of the described species of the genus have a trianguloid lateral outline, strongly convex dorsal margin, posterior margin steeply down-sloping and narrowly ven- trally rounded, generally smooth valve surface, narrow me- dian hinge element, distinct accommodation groove, and frontal scars that comprise two closely spaced scars. In @ Figure3. 1,2. Neomonoceratina paraoertlii sp. nov. 1, holotype, SUGDMF no. 574, carapace, right valve view, x157; 2, paratype, SUGDMF no. 575, carapace, dorsal view, x152. SUGDMF no. 581, right valve view, x72. 8, paratype, SUGDMF no. 583, female carapace, right valve view, x147. 3-5. Paijenborchellini gen. et sp. indet. valve, SUGDMF no. 577, internal view, x100; 5, right valve, SUGDMF no. 578, dorsal view, 105. A. 3, carapace, SUGDMF no. 576, right valve view, x102; 4, left 6. Cushmanidea bhatiai Bhandari, carapace, 7, 8. Krithe bhandarii sp. nov. 7, holotype, SUGDMF no. 582, male carapace, right valve view, x142; 9-11. Holcopocythere bassiporosa A\-Furaih. 9, left valve, SUGDMF no. 584, lateral view, x111; 10, right valve, SUGDMF no. 585, internal view, x113; 11, carapace, SUGDMF no. 586, dorsal view, x120. 12, 13. Cos- tabuntonia hartmanni (Jain). 12, female carapace, SUGDMF no. 554, right valve view, x90; 13, male carapace, SUGDMEF no. 557, right valve view, x87. ‘E © &0 Ss Z TS — = Ss TD = TD S Ss Ss D © S Mm = Ss TD = 3 = © ‚ei a Ss = Ta) 3 n Paleocene ostracodes from India 203 contrast to this pattern the present species has an elongate and subovate lateral outline, the greatest height slightly an- terior to the middle, dorsal margin arched, anterior and pos- terior margins evenly rounded, median hinge element quite wide, accommodation groove almost lacking, and frontal scar typically v-shaped. The species is very similar to Neocyprideis bhupendri Singh and Mishra (1968) from the Lower Eocene of Rajasthan in all the essential carapace characters (see also Khosla, 1972). This species is also recorded from the Middle Eocene of Kachchh by Khosla and Pant (1988) and the Middle Eocene of Meghalaya by Bhandari (1992). Restudy of the type material of N. bhupendri is required to clarify the identity with the present species. The species also closely resembles Neocyprideis simplex Siddiqui (2000) from the Lower Eocene of Pakistan in lateral outline and ornamentation. On the basis of the characters given above the present species is transferred to the genus Neocyprideis. Dimensions. —A carapace, SUGDMF no. 579, length 0.75 mm, height 0.48 mm, width 0.40 mm; a left valve, SUGDME no. 580, length 0.75 mm, height 0.50 mm. Occurrence.—Sections I and II. Family Krithidae Genus Krithe Brady, Crosskey and Robertson, 1874 Type species. —Ilyobates praetexta Sars, 1866. Krithe bhandarii sp. nov. Figure 3.7, 3.8 Etymology.—The species is named in honor of Dr. Anil Bhandari, Chief Geologist, Micropaleontology Laboratory, KDMIPE, ONGC Ltd., Deharadun, India. Material.—264 carapaces. Type locality. — Light yellow limestone (Sample SUGDMF no. 3/11), Inter-trappean beds, Paleocene. Section Il. Diagnosis. — Carapace elongate, with greatest height posterior to middle; ventral margin concave anteriorly; pos- terior margin forming obtuse angle with ventral margin. Description.—Sexual dimorphism distinct, males being more elongate, less high and wide than females. Carapace elongate, subrectangular in lateral outline, with greatest height almost half of length posterior to middle; left valve overlaps right valve along dorsal, anterior and mid-ventral margins; dorsal margin asymmetrically convex, merges gradually with anterior margin, and steeply sloping down- ward from posterior 2/5 of length; ventral margin with a distinct concavity anterior to middle; anterior margin nar- row, evenly rounded; posterior obliquely rounded forming obtuse angle with ventral margin; in dorsal view carapace compressed with maximum width near middle. Valve sur- face smooth. Dimensions .—Holotype, SUGDMF no. 582, a male carapace, length 0.43 mm, height 0.22 mm, width 0.19 mm; paratype, SUGDMF no. 583, a female carapace, length 0.40 mm, height 0.24 mm, width 0.19 mm. Discussion:—Krithe bhandarii sp. nov. resembles Krithe oryza Neale and Singh (1985) and Krithe cf. K. oryza from the Middle Eocene of Assam in having a vaulted dorsal margin but is readily differentiated in having a distinct con- cavity along the ventral margin and different outline of the posterior margin. Occurrence.—Sections I and II. Family Hemicytheridae Subfamily Orionininae Genus Falsocythere Ruggieri, 1972 Type species.—Falsocythere maccagnoi (Ciampo, 1972) Ruggieri, 1972. Falsocythere elongata (Bhalla, 1979) Figure 4.5, 4.6 Occultocythereis elongatum Bhalla, 1979c, p.146-148, figs. A-D. Material.—40 carapaces. Description. —Carapace elongate subquadrate in lateral outline, with greatest height about half of length at anterior cardinal angle and greatest length at ventral one-third of height; dorsal margin partly obscured due to overhanging ridge, otherwise straight, sloping down posteriorly; ventral margin slightly concave; anterior margin broadly rounded; posterior margin much narrowed, drawn out ventrally, dis- tinctly concave in upper part and obliquely truncated in lower part; anterior and posterior margins denticulate; @ Figure 4. 1. Nucleolina diluta Al-Furaih, carapace, SUGDMF no. 587, right valve view, x84. 2, 3. Hermanites sastryi Bhalla. 2, carapace, SUGDMF no. 588, right valve view, x64; 3, right valve, juvenile, SUGDMF no. 589, lateral view, x80. 4. Hornibrookella tewarii (Bhalla), carapace, SUGDME no. 590, right valve view, x86. 5-6. Falsocythere elongata (Bhalla). 5, carapace, SUGDMF no. 591, right valve view, x110; 6, carapace, SUGDMF no. 592, dorsal view, x119. 7. Palmoconcha rajui Bhandari, carapace, SUGDMF no. 593, right valve view, x122. 8-10. Hapsicytheridea undulata sp. nov. 8, holotype, SUGDMF no. 594, carapace, right valve view, x121; 9, paratype I, SUGDMF no. 595, carapace, dorsal view, x123; 10, paratype II, SUGDMF no. 596, right valve, internal view, x122. 11-13. Cytherura duddukuruensis sp. nov. 11, holotype, SUGDMF no. 597, female carapace, right valve view, x157; 12, paratype I, SUGDMF no. 598, female carapace, dorsal view, x155; 13, paratype II, SUGDMF no. 599, male carapace, right valve view, x155. 204 Subhash Chandar Khosla and Madan Lal Nagori Paleocene ostracodes from India valve surface ornamented by a high anterior marginal rim which also continues along ventral and posterior margins; an arched dorsal ridge starting from mid-dorsal region overhangs posterodorsal margin and sharply turns forming a U-shaped bend and then continues as a diagonal ridge to anteromedian region: a low vertical ridge extends down- wards from the U-shaped bend; area along marginal rim laterally compressed and smooth; faint reticulation over rest of surface Remarks:—Occultocythereis elongatum was described by Bhalla (1979c) from the Inter-trappean beds of Duddukuru. The specimens he illustrated are internal moulds, so that they lack surface reticulation and marginal denticles. The well preserved specimens we newly col- lected from the type locality allow us to reconsider the ge- neric position of this species. The lateral outline and surface ornamentation of the spe- cies differ from those of the genus Occultocythereis. Species of the latter genus generally have a subquadrate lat- eral outline and a subangular or rounded posterior margin. In addition, they have a valve surface ornamented by 1) a prominent angular massive tubercle at the posterodorsal cardinal angle and a ridge extending from it along the dor- sal margin, 2) a prominent anterior rim, 3) a small posteroventral winglike projection with a short vertical ridge posteriorly, and 4) denticles at anterior and posterior margins. Except for having a ventrally drawn-out poste- rior margin, the present species closely resembles Falsocythere indica Khosla and Nagori, 1989, a Lower Miocene species of Kerala, and F. maccagnoi (Ciampo, 1972), a Recent species, in overall lateral outline and sur- face ornamentation. On this basis the species is herein transferred to the genus Falsocythere. The difference in the shape of the posterior margin of the present species might be due to the range of variation within the genus. Dimensions.— A carapace, SUGDMF no. 591, length 0.56 mm, height 0.27 mm, width 0.19 mm; a carapace, SUGDMF no. 592, length 0.53 mm, height 0.27 mm, width 0.19 mm. Occurrence.—Sections I and II. Family Loxoconchidae Genus Palmoconcha Swain and Gilby, 1974 Tpye species.—Palmoconcha laevimarginata Swain and NO © on Gilby, 1974. Palmoconcha rajui Bhandari, 1995 Figure 4.7 Loxoconcha sp. Jain, 1978, p. 56, pl. 2, figs. 6, 7. Palmoconcha rajui Bhandari, 1995, p. 96, 97, pl. 4, figs. 1-4. Material. —84 carapaces and 35 valves. Remarks.—The present species was described from the Paleocene Inter-trappean beds of Duddukuru by Bhandari (1995). It is based on closed carapaces and its generic as- signment is highly questionable. The genus Palmoconcha is characterised by the presence of flattened, flangelike ter- minal marginal areas, a gongylodont hinge, a broad vesti- bule, and numerous closely spaced short marginal pore canals. In contrast, the present species has an anti- merodont hinge structure; in the left valve the hinge com- prises loculate terminal sockets that are connected by a finely crenulate median bar, and in the right valve it is com- plementary, has a few widely spaced, straight, marginal pore canals and lacks flangelike terminal areas and vesti- bule. Probably a new generic name is required to accom- modate this species, but it is deferred unless additional species are found. Dimensions. —A carapace, SUGDMF no. 593, length 0.51mm, height 0.29 mm, width 0.29 mm. Occurrence.— Sections I and II. Family Cytheruridae Genus Hapsicytheridea Al-Furaih, 1980 Type species. — Hapsicytheridea binodosa Al-Furaih, 1980. Hapsicytheridea undulata sp. nov. Figure 4.8-4.10 Cytheridella sp. Bhandari, 1995, p. 95, pl. 1, fig. 4. Etymology.—From Latin, meaning wavy, referring to sinuous venter surface. Material.—346 carapaces and 18 valves. Type locality. — Light yellow limestone SUGDMF no. 8/I), Inter-trappean beds, (Sample Paleocene. “ Figure5. 1. Paijenborchellina indica (Khosla), carapace, SUGDMF no. 600, right valve view, x105. 2-4. Semicytherura diluta sp. nov. 2 Zs holotype, SUGDMF no. 601, female carapace, right valve view, x150; 3, paratype I, SUGDMF no. 602, male carapace, right valve view, x137; 4, paratype Il, SUGDMF no. 603, female carapace, dorsal view, x146. 5, 6. Uroleberis rasilis sp. nov. 5, holotype, SUGDMF no. 604, carapace, right valve view, x124; 6, paratype, SUGDMF no. 605, carapace, dorsal view, «100. no. 606, left valve view, x164; 8, carapace, SUGDMF no. 607, dorsal view, x135. 608, right valve view, x71. 7, 8. Xestoleberis subglobosa (Bosquet). 7, carapace, SUGDMF 9. Paracypris khuialaensis Bhandari, carapace, SUGDMF no. 10-13. Paracandona andhraensis sp. nov. 10, holotype, SUGDMF no. 609, left valve, lateral view, x129; 11, paratype I, SUGDMF no. 610, right valve, internal view, x131; 12, paratype II, SUGDMF no. 611, left valve, internal view, x144; 13, paratype III, SUGDMF no. 612, right valve, dorsal view, x151. 206 Subhash Chandar Khosla and Madan Lal Nagori Section I. Diagnosis.—Surface marked by a prominent groove in posteroventral region, an arcuate carina near posterior mar- gin in right valve, and broad shallow reticulation. Description. — Carapace elongate, subquadrate in lateral view, with greatest height about half of length, at anterior cardinal angle; left valve larger than right valve, overlap- ping distinctly along anterior and posterodorsal margins; dorsal margin nearly straight; ventral margin sinuate; ante- rior margin broadly rounded; posterior margin subangulate near mid-height; in dorsal view carapace somewhat in- flated, maximum width half of length posteriorly, anterior end narrow, posterior region laterally compressed. Eye tu- bercle distinct. Valve surface marked by a prominent groove in posteroventral region; a depression posterior to eye tubercle; arcuate carina near posterior margin in right valve; anterior marginal area compressed and smooth; rest of the area ornamented by broad shallow reticulations, ar- ranged in concentric pattern. Inner lamella narrow; line of concrescence and inner margin coincide; selvage distinct near inner periphery; normal pores widely spaced. Hinge antimerodont; in right valve it comprises 8 anterior and 6 or 7 posterior terminal teeth and loculate median groove. Dimensions .—Holotype, SUGDMF no. 594, a carapace, length 0.53 mm, height 0.26 mm, width 0.27 mm; paratype I, SUGDMF no. 595, a carapace, length 0.53 mm, height 0.26 mm, width 0.26 mm; paratype II, SUGDMEF no. 596, a right valve, length 0.51 mm, height 0.26 mm. Discussion.—The species was originally described as Cytheridella sp. by Bhandari (1995) from the Inter- trappean beds of Duddukuru. However, unlike the genus Cytheridella, which is characterised by an adont hinge, the new species has a distinct antimerodont hinge structure. The present species resembles Hapsicytheridea binodosa Al- Furaih (1980) from the Lower Paleocene of Saudi Arabia in overall outline and surface ornamentation but dif- fers in the absence of two nodes in the posterolateral region and other ornamental details. The species also lacks a clear caudal process along the posterior margin. Occurrence.—Sections I and II. Subfamily Cytherurinae Genus Cytherura Sars, 1866 Type species.—Cythere gibba O. F. Müller, 1785. Cytherura duddukuruensis sp. nov. Figure 4.11-4.13 Etymology.— After the village of Duddukuru. Material.—309 carapaces. Type locality. — Light yellow limestone (Sample SUGDMF no. 3/II), Inter-trappean beds, Paleocene. Section II. Diagnosis.—Carapace pear-shaped in lateral outline; sur- face ornamented by dense fine punctation. Description.—Sexual dimorphism distinct, males being more elongate, less high and less wide than females; cara- pace pear-shaped in lateral outline, with greatest height at anterior cardinal angle; valves strongly compressed posteroventrally; overlap indistinct; dorsal margin straight, converging posteriorly; ventral margin distinctly sinuate medially; anterior margin broad and obliquely rounded; posterior margin with a caudal process at mid-height; in dorsal view, carapace biconvex with maximum width near middle, ends compressed. Valve surface ornamented by dense, fine punctation. Internal characters not known. Dimensions.— Holotype, SUGDMF no. 597, a female carapace, length 0.40 mm, height 0.24 mm, width 0.16 mm; paratype I, SUGDMF no. 598, a female carapace, length 0.40 mm, height 0.24 mm, width 0.18 mm; paratype II, SUGDMF no. 599, a male carapace, length 0.42 mm, height 0.21 mm, width 0.14 mm. Discussion.—Cytherura duddukuruensis sp. nov. resem- bles Cytherura interposita Lyubimova and Guha in Lyubimova er al. (1960) from the Miocene of Kachchh in overall shape. The latter species, however, differs from the present species in having an oblong lateral outline, a shallow vertical sulcus and reticulation, and meshes enclos- ing two or more punctae. Occurrence.— Sections I and II. Genus Semicytherura Wagner, 1957 Type species.—Cythere nigrescens Baird, 1838. Semicytherura diluta sp. nov. Figure 5.2-5.4 Etymology. —From Latin diluta meaning weakened or thinned; with reference to the faint ornamentation. Material.—110 carapaces. Type locality. — Light SUGDMF no. VID, Section II. Diagnosis. — Surface ornamented by feeble transverse ridges and reticulation in ventral half. Description. —Sexual dimorphism distinct, males being more elongate, less high and more wide than females; cara- pace subovate in lateral outline, with greatest height near middle and greatest length below mid-height; overlap indis- tinct; dorsal margin strongly convex in females and arched in males; ventral margin concave anteriorly but convex posteriorly; anterior margin narrowly rounded; posterior drawn out in a caudal process slightly below mid-height; in dorsal view carapace biconvex, posterior end compressed, yellow limestone (Sample Inter-trappean beds, Paleocene. Paleocene ostracodes from India 207 maximum width near middle in females, posterior in males. Valve surface ornamented by feeble transverse ridges in ventral half, lowermost ridge continuous from anteroventral to posteroventral region, other ridges intersecting each other in ventromedian region forming weak reticulation; fine punctation over rest of area. Dimensions. — Holotype, SUGDMF no. 601, a female carapace, length 0.42 mm, height 0.26 mm, width 0.22 mm; paratype I, SUGDMF no. 602, a male carapace, length 0.46 mm, height 0.24 mm, width 0.22 mm; paratype II, SUGDMF no. 603, a female carapace, length 0.43 mm, height 0.26 mm, width 0.22 mm. Discussion.—Semicytherura diluta sp. nov. closely re- sembles Semicytherura indica? subspecies described by Neale and Singh (1985, pl. 46, fig. 2) in overall outline and ornamentation. S. indica ? subspecies is based on a single specimen and inadequately described. It differs from S. diluta in having feeble transverse ridges all over the valve surface and a nearly straight ventral margin. Semicytherura longilinea Bhandari (1995) from the Lower Eocene Khuiala Formation of Jaisalmer resembles S. diluta in appearance. However, it differs in having 9 or 10 transverse ridges that extend nearly the entire length of the carapace. Occurrence.—Section II. Family Xestoleberididae Genus Uroleberis Triebel, 1958 Type species.—Eocytheropteron parnensis Apostolescu, 1955. Uroleberis rasilis sp. nov. Figure 5.5, 5.6 Etymology.— From Latin rasilis, meaning smoothed; with reference to smooth surface. Material.—Three carapaces. Type locality. — Greyish-white limestone (Sample SUGDMF no. 7/Il), Inter-trappean beds, Paleocene. Section II. Diagnosis.—Carapace ovate in lateral outline; posterior margin with an indistinct caudal process. Description. —Carapace ovate in lateral outline, with greatest height near middle; left valve slightly overlaps right valve along dorsal and posterior margins; dorsal mar- gin arched; ventral margin nearly straight; anterior margin narrowly rounded; posterior margin slightly concave in upper part, rounded in lower part and with indistinct caudal process; in dorsal view carapace biconvex, ends narrowed, maximum width slightly posterior to middle. Valve sur- face smooth. Dimensions.—Holotype, SUGDMF no. 604, a carapace, length 0.45 mm, height 0.30 mm, width 0.30 mm; paratype, SUGDME no. 605, a carapace, length 0.45 mm, height 0.32 mm, width 0.32 mm. Discussion.—The species resembles Uroleberis sp. aff. U. sp. 1 described by van den Bold (1988) from the Upper Miocene-Pliocene of the Dominican Republic in lateral outline but differs in the absence of transverse ridges in the ventral region. Occurrence.— Section II. Superfamily Cypridacea Baird, 1845 Family Candonidae Kaufmann, 1900 Subfamily Candoninae Kaufmann, 1900 Genus Paracandona Hartwig, 1899 Type species.—Candona euplectella Brady and Norman, 1889. Paracandona andhraensis sp. nov. Figure 5.10-5.13 Etymology.—After the Indian state of Andhra Pradesh. Material.—Ten valves. Type _ locality. — Light yellow limestone (Sample SUGDMF no. 3/1), Inter-trappean beds, Paleocene. Section I. Diagnosis.—Valve surface marked by dense reticulation, meshes enclosing 3 or 4 punctae. Description. — Valve subrectangular in lateral outline, with greatest height a little over half of length near anterior cardinal angle; dorsal margin straight; ventral margin slightly concave anterior to middle; anterior margin broad and evenly rounded; posterior margin slightly narrow, slop- ing down in upper half and rounded in lower; posterior car- dinal angle distinct; in dorsal view valve nearly convex, flat medially. Valve surface ornamented by dense reticulation, arranged concentrically, meshes enclosing 3 or 4 punctae; anterior and posteroventral regions laterally compressed. Inner lamella narrow; line of concrescence and inner mar- gin coincide; selvage well developed, near inner periphery. Hinge modified adont; in right valve it consists of a smooth ridge, selvage at its terminal ends raised giving socketlike appearance; hinge complementary in left valve. Central muscle scars not known. Dimensions.—Holotype, SUGDMF no. 609, a left valve, length 0.45 mm, height 0.24 mm; paratype I, SUGDMF no. 610, a right valve, length 0.45 mm, height 0.22 mm; paratype II, SUGDMF no. 611, a left valve, length 0.43 mm, height 0.22 mm; paratype III, SUGDMF no.612, a right valve, length 0.42 mm, height 0.22 mm. Discussion. — The species resembles Paracandona aff. belgica Tambareau, 1984, described from the Thanetian of the Paris Basin in subrectangular lateral outline and reticu- PRE er 208 Subhash Chandar Khosla and Madan Lal Nagori lated ornamentation. Paracandona aff. belgica, unlike the present species, has fine, hexagonal reticules and lacks lat- erally compressed anterior and posteroventral margins. Occurrence.—Section I. Acknowledgments The authors are highly thankful to P. K. Sarasvati, Indian Institute of Technology, Powai for extending SEM facili- ties, to S. R. Jakhar for his assistance in photography and other illustrations and to the anonymous reviewers for their useful suggestions to improve the paper. References Alexander, C. I., 1929: Ostracoda of the Cretaceous of north Texas. University of Texas Bulletin, no. 2907: p. 1-137. Al-Furaih, Ali A. F., 1980: Upper Cretaceous and Lower Tertiary Ostracoda (Superfamily Cytheracea) from Saudi Arabia, 211 p., 65 pls. 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These de la Faculte des Sicences, Universite de Paris, p. 1-259. Paleontological Research, vol. 6, no. 2, pp. 211-217, June 28, 2002 © by the Palaeontological Society of Japan Fossil crabs (Crustacea: Decapoda: Brachyura) from the latest Miocene Senhata Formation, Boso Peninsula, Japan HISAYOSHI KATO Natural History Museum and Institute, Chiba, 955-2, Aoba-cho, Chiba 260-8682, Japan (e-mail: katoh@chiba-muse.or.jp) Received August 27, 2001; Revised manuscript accepted March 15, 2002 Abstract. Two species of fossil decapods, Maja tomidai sp. nov. and Daldorfia sp. are described from the latest Miocene Senhata Formation of the Boso Peninsula, central Japan. The former species resembles Maja morii Kato from the middle Miocene of Japan and Maja dominoleuae Hu and Tao from the late Miocene of Taiwan. A large palm of Daldorfia sp. is the third fossil record of the genus from Japan. The discovery of Daldorfia sp. supports the existence of subtropical to tropical marine conditions in the latest Miocene of the Boso Peninsula indicated previously by molluscan evidence. Key words: Brachyura, Crustacea, Daldorfia, Decapoda, Maja, Senhata Formation, Zushi Fauna Introduction Decapod Crustacea from the upper Miocene of Japan have previously been reported from the Tano and Aya for- mations of the Miyazaki Group, Kyushu (4 species; Karasawa, 1993, 1997; Karasawa and Kato, 1996); the Uchiumigawa Group, Kyushu (1 species; Karasawa, 1990); the Itahana Formation of the Tomioka Group, central Japan (8 species; Kato, 2001); the Aosc Formation, north of Sendai (1 species; Karasawa and Kato, 1996), and the Wakkanai Formation, Hokkaido (1 species; Imaizumi, 1952). Two species of decapod crustaceans were obtained from exposures of the upper Miocene Senhata Formation in the Matsukura Kogyo Quarry in Motona, Kyonan Town, Chiba Prefecture (35° 9° N, 135° 51° E) (Figure 1). A specimen found by S. Tomida represents a new species of the majid genus Maja. Several additional fragmentary specimens were subsequently collected from the same locality by N. Kaneko and donated to the Natural History Museum and Institute, Chiba. The other specimen collected by K. Usui is identified as a large palm belonging to the daldorfiid genus Daldorfia. The purpose of this paper is to describe the new species of Maja and the undetermined species of Daldorfia, and to discuss their phylogenetic and paleobiogeographic implica- tions. The material described herein is deposited in the Mizunami Fossil Museum (MFM) and Natural History Museum and Institute, Chiba (CBM-PI). Locality and paleoenvironments The Senhata Formation exposed at the present locality is up to 130 m in thickness and is composed mainly of coarse- grained sediments, intercalating mudstones and pyroclastics (Yabe and Hirayama, 1998). The formation yields abun- dant remains of marine animals such as _ molluscs, hermatypic corals, bryozoans, isopods, echinoids, elasmo- branchs and mammals. The geologic age of the Senhata Formation has been dis- cussed from various viewpoints. Ibaraki and Tsuchi (1980) assigned the formation to Blow’s (1969) planktonic foraminifera Zone N17. Kanie et al. (1991) reported cal- careous nannofossils indicative of the CN9 Zone of Okada and Bukry (1980) from the underlying Amatsu Formation and the CN10b Zone from the overlying Inakozawa Formation. Kasuya (1987) reported a fission-track age of 6.3 + 0.4 Ma for the Ok tuff bed in the lower part of the Inakozawa Formation. To sum up these data, the geologic age of the Senhata Formation is regarded as the latest Miocene. O’Hara and Ito (1980) studied the molluscs of the Senhata Formation and noted that the assemblage is a mix- ture of relatively worn and fragmented shells of shallow- water inhabitants and well preserved shells of deep-water dwellers. They concluded that the shallow-water 212 Hisayoshi Kato 130°E 135° 140° 145° Figure 1. Map showing the fossil locality. assemblage was mixed with a bathyal assemblage as a re- sult of short distance transportation by bottom currents. Tomida (1989, 1996) recognized seven types of molluscan assemblages in the formation. He also considered the molluscan assemblage of the present locality to be a mix- ture of both a bathyal assemblage (200-250 m in depth on the continental slope) and mesoneritic to subneritic assem- blages that were transported from shallower waters. Based on the occurrences of the isopod Palaega, Karasawa et al. (1992) suggested an upper bathyal paleoenvironment for the Senhata Formation. Tomida and Itoigawa (1986) and Tomida (1989) re- ported the occurrences of the planktonic gastropod Hartungia sp. and cephalopods such as Aturia and Argonauta in various growth stages from the present local- ity. Based on the presence of these characteristic genera and other subtropical to tropical molluscs, Tomida (1983, 1996), Tomida and Itoigawa (1986) and Ozawa and Tomida (1992, 1996) deduced that the Senhata Formation was deposited under the influence of warm-water currents. In their study of the selachian (shark) assemblage of the Senhata Formation, Yabe and Hirayama (1998) also con- cluded that this formation was deposited in the upper part of the continental slope under the influence of warm-water currents. Ozawa and Tomida (1992) and Ozawa et al. (1995) pro- posed the term “Zushi Fauna” for some late Miocene to early Pliocene molluscan assemblages on the Pacific side of Japan which contain molluscan species indicative of tropi- Senhata Fm. Daldorfia sp. 30° % Locality of Zushi Fauna o Warm-temperate molluscan fauna in Ozawa and Tomida (1992) #2 Warm and cool water current 25°N Presumed land area pee 130°E 135° 140° 145° Figure 2. Localities of fossil Daldorfia species. Distribution of the Zushi Fauna and reconstruction of paleogeography are modified after Ozawa and Tomida (1992), Ogasawara (1994) and Nakamura et al. (1999). The paleoclimatology is based on Ogasawara’s (1994) divisions. cal to subtropical marine climates (Figure 2). lated this warmer marine climate with Optimum 3” of Barron and Baldauf (1990). Among the decapod genera here described, the genus Maja has 16 living species, of which 13 occur in the Indo- West Pacific (Griffin and Tranter, 1986) and 7 in Japanese warm-temperate to tropical waters south of the Boso Peninsula, central Japan (Sakai, 1976). The genus Daldorfia includes 6 living species in tropical to subtropi- cal Japanese waters (Sakai, 1976). Particularly, D. horrida (Linnaeus, 1758), the most closely related to D. sp. from the Senhata Formation, inhabits tropical to subtropical wa- ters south of the Kii Peninsula in Japan, the area washed by the warm Kuroshio Current (Sakai, 1976). Judging from the distributions of living species, the decapod species found in the Senhata Formation support the view previ- ously suggested by molluscan evidence that a warm marine climate existed along the Pacific coast of Japan in the latest Miocene. Fossil species of Daldorfia have hitherto been recorded from the upper Miocene of Japan and Oligocene of North America. They are D. nagashimai Karasawa and Kato, They corre- “Climatic Miocene crabs from Japan 213 1996 from the Aya Formation, Miyazaki Group in south- west Japan, Daldorfia sp. from the Aoso Formation in northeast Japan (Karasawa and Kato, 1996; Figure 2), and Daldorfia himaleorhaphis Schweitzer, 200la from the Jansen Creek Member of the Makah Formation in the Olympic Peninsula, Washington State, the United States of America. The Aya Formation yields molluscan species typical of the “Zushi Fauna” (Nakamura et al., 1999). While Ozawa and Tomida (1992) suggested that the “Zushi Fauna” ex- tended north into the Fukuda Formation, south of Sendai, the occurrence of Daldorfia sp. from the Aoso Formation indicates that the fauna extended north of Sendai, where a warm-water event is suggested by molluscs (Ogasawara, 1994) and planktonic foraminiferal assemblages correlative with “Climatic Optimum 3” of Barron and Baldauf (1990) (Saito and Isawa, 1995). The occurrences of Daldorfia spp. from the Aya, Senhata and Aoso formations provide additional biotic evidence for the warming event in the late Miocene to early Pliocene in northeast Japan. The occur- rence of the oldest known species of Daldorfia, D. himaleorhaphis from the Oligocene of Washington State, is considerably distant geographically from the distribution of living species of this genus. However, the high diversity of the decapod assemblages, including subtropical species from the Eocene to Oligocene of the Pacific North America, indicates a much warmer marine climate in this area than prevails today (Schweitzer, 2001b). Systematic descriptions Section Heterotremata Guinot, 1977 Superfamily Majoidea Samouelle, 1819 Family Majidae Samouelle, 1819 Subfamily Majinae Samouelle, 1819 Genus Maja Lamarck, 1801 Type species.—Cancer squinado Herbst, 1788. By sub- sequent designation (ICZN opinion 511). Discussion. — Based upon larval morphology, Rice (1983) proposed a phylogenetic relationship between gen- era within the family Majidae, regarding Maja as a “primi- tive” and Leptomithrax as an “advanced” form. Several previous studies also supposed the same relationship be- tween the two genera (e.g. Kurata, 1969). The cup-shaped orbit of living species of Leptomithrax (three closely spaced orbital spines and the antennal fossa excluded from the orbit) is generally regarded as more “complete” than that of Maja (separate spines with an antenna included within the orbit). However, the orbital features of the early middle Miocene Maja morii Kato, 1996 from Japan resemble those of Leptomithrax, including its postorbital spine which exhibits an excavated anterior surface like that typically observed in Leptomithrax (Griffin, 1966). With respect to the posterior end of the carapace, the Japanese fossil Maja species, M. morii and the new species discussed herein have a single tubercle on the posterior end of the carapace as in Leptomithrax longipes (Thomson, 1902), a living species found in Australia and New Zealand. In its adult and larval morphologies, L. longipes was regarded as unique among the members of the genus Leptomithrax (Webber and Wear, 1981; McLay et al., 1995). Judging from these characters the phylogenetic relation- ship between Leptomithrax and Maja should be reconsid- ered. The oldest fossil record of Maja is from the early Miocene (Maja robinsoni Jenkins, 1985 from South Australia), while that of Leptomithrax extends into the late Eocene (Leptomithrax griffini Feldmann and Maxwell, 1990 from New Zealand), suggesting that Maja is a more advanced form than Leptomithrax. Geologic range.—Miocene to Recent. Maja tomidai sp. nov. Figures 3.1a-c, 4, 5B Diagnosis.—Maja with moderately long, divergent ros- trum; lateral and dorsal spines acute. Intercalated and postorbital spines approximated. Dorsal regions densely covered with large, conical tubercles. Posterior end of carapace bearing single conical tubercle. Description.—Carapace pyriform in outline. Rostrum bifid, acute, widely divergent anterolaterally. Orbit round- ed. Supraorbital eave thick, sparsely granulate. Antorbital spine acutely triangular, directed laterally, slightly curved posteriorly. Intercalated spine short, triangular, about half length of antorbital and one-third length of postorbital spines. Postorbital spine triangular, directed anteriorly. Intercalated and postorbital spines closely approximated. Basal antennal article directed forward with anteromedial and anterolateral spines. Anterolateral margin of carapace bears acute, long hepatic spine and three acute branchial spines; posteriormost one lies dorsally. Dorsal regions well defined. Gastric, branchial, and hepatic regions strongly convex, covered with pointed, variable-sized coni- cal tubercles. Frontal region with two longitudinal series of conical tubercles; tubercles extending to base of rostrum, increasing in size posteriorly. Mesogastric region strongly convex with two large, conical tubercles arranged longitu- dinally. Metagastric region also highly convex with large median tubercle. Urogastric region with conical tubercle markedly smaller than others. Cardiac region strongly con- vex, defined laterally by broad, plain furrows, and medially by a large, conical tubercle. Intestinal region elevated, forming acute spine. Hepatic region with clustered tuber- cles, bordered by broad, plain depressions. Branchial re- 214 Hisayoshi Kato Figure 3. gions with numerous variable-sized tubercles. Sinuous swellings extending parallel to branchiocardiac groove consisting of large tubercles. Metabranchial region con- vex with sparse tubercles and granules, less developed than mesobranchial and intestinal swellings. Posterolateral margin rimmed, sinuously convex. Posterior end of cara- pace bearing one large, conical, axial tubercle. Palm of right cheliped slightly curved upward; preserved part of 1. Maja tomidai sp. nov., MFM 83053. Holotype. a and b, outer and medial surface of the right chela, x1.5; c, carapace, x1.0. 2. Daldorfia sp., CBM-PI 01084, manus of right chela; a ; outer surface, b ; medial surface. CBM-PI 01084, x0.5. Scale bars = 10 mm. outer surface smooth. curved downward. Discussion.—In carapace outline, the present species most resembles Maja dominoleuae Hu and Tao, 1985 from the upper Miocene of Taiwan. However, M. tomidai sp. nov. is easily distinguished from M. dominoleuae in that the orbital spines are shorter and slightly curved upward, and the dorsal surface of the carapace is densely covered by Fingers acute, slender, obviously Miocene crabs from Japan 215 Figure 4. Line drawing showing the dorsal view of carapace of Maja tomidai sp. nov. The specimen is compressed obliquely, causing the right half of the carapace to be displaced anteriorly. Scale bar = 10 mm. large tubercles. Maja tomidai sp. nov. resembles M. morii Kato, 1996 from the early middle Miocene of the Chichibumachi and Takaku groups, Saitama and Fukushima prefectures, Japan (Kato and Karasawa, 1995) in the general arrangement of tubercles and lateral spines of the carapace, but differs in having denser tubercles and more elongated spines on the dorsal surface. In addition, the antennal fossa of Maja morii seems to lie outside the orbit, while that of Maja tomidai is included within the orbit like living species of Maja (Figure 5). Despite these differences, M. tomidai sp. nov. shares the following important characters with M. morii: (1) the three orbital spines are relatively approximated, and (2) the pos- terior end of the carapace has a single conical tubercle. Most living species of Maja possess a pair of spines or tu- bercles on the posterior end of the carapace, and no species in this genus has a large, single tubercle on the posterior end of the carapace like M. tomidai sp. nov. and M. morii. Due to the incompleteness of known specimens, unfortu- nately, the ventral orbital features and the posterior end of the carapace of M. dominoleuae are not available. The carapace of the holotype is compressed and severely deformed (Figure 4). Material examined.—MFM 83053 (Holotype: carapace and appendages). CBM-PI 01085-01087. Etymology.—Named after Susumu Tomida who contrib- uted greatly to the paleontology of the Senhata Formation and discovered the holotype specimen. Measurements. — Holotype, maximum carapace length A Rt Figure 5. Line drawing showing the ventral orbital features of (A) Maja morii Kato, 1996 (CBM-PI 00177, Numanouchi Formation, Takaku Group) and (B) Maja tomidai sp. nov. (holotype). Abbreviations: Ot, orbit, Rt, rostrum, af, antennal fossa, ba, basal antennal article, ps, postorbital spine, se, supraorbital eave. Scale bar = 10 mm. (including rostrum), 78.0 mm; maximum carapace width (excluding the branchial spines), 43.5 mm. Palm length, 37.0 mm. Superfamily Parthenopoidea MacLeay, 1838 Family Daldorfiidae Ng and Rodriguez, 1986 Genus Daldorfia Rathbun, 1904 Type species.— Cancer horridus Linnaeus, 1758. By monotypy. Geologic range.—Oligocene to Recent. Daldorfia sp. Figure 3.2a, b Description.—Manus of right cheliped without fixed fin- ger large (length, 131 mm), strongly compressed; upper and lower margins diverging distally. Lateral and medial sur- faces densely nodose. Nodes conical to irregular; variable 216 Hisayoshi Kato in size up to 20 mm in diameter; surface bearing clusters of various-sized tubercles. Furrows between nodes shallow, smooth except for scattered small conical tubercles. Superior socket of articulation, situated near dorsoproximal corner of manus and directed proximally. Proximal mar- gins of lateral and medial surfaces bearing rounded, thick rims along articulation with carpus. Discussion.—The previously known fossil record of this genus from Japan includes Daldorfia nagashimai Karasawa and Kato, 1996 from the latest Miocene Aya Formation, Miyazaki Group in southwest Japan and D. sp. from the late Miocene Aoso Formation to the north of Sendai in northeast Japan (Karasawa and Kato, 1996) (Figure 2). Daldorfia? sp. from the middle Miocene Aoki Formation in central Japan (Karasawa et al., 1999) is too incomplete to permit generic assignment. It may belong to a species of the Majidae. Therefore, Daldorfia sp. described here is the third fossil record for this genus from Japan. Living species of Daldorfia are inhabitants of littoral and sublittoral zones (Sakai, 1976). Judging from the disarti- culated and incomplete state of the present specimen, it may have been transported from a littoral or sublittoral zone, together with shallow-water molluscs, to the deeper- water environment of the Senhata Formation. Material examined.—CBM-PI 01084. Measurements.—Manus length, 131 mm, manus height, 88 mm. Acknowledgments The author is much indebted to Susumu Tomida (Chukyogakuin University) and Kazuyuki Usui (Mito City) for donating the specimens. I wish to express my sincere gratitude to Rodney M. Feldmann (Kent State University, Ohio), Warren C. Blow (National Museum of Natural History, Smithsonian Institution) and Hiroaki Karasawa (Mizunami Fossil Museum) for their critical reading of the manuscript and for providing many valuable comments and discussions. Thanks are also due to Naotomo Kaneko (Geological Survey of Japan), Osamu Fujiwara (Tono Geoscience Center), Yuji Takakuwa (Gunma Museum of Natural History), and Kokichi Inoue (Abiko City) for do- nating and providing access to the fossil specimens, and giving valuable information and comments. References Barron, J. A. and Baldauf, J. G., 1990: Development of biosiliceous sedimentation in the North Pacific during the Miocene and Early Pliocene. Jn, Tsuchi, R., ed., Pacific Neogene Events, their Timing, Nature and Interrelationship, p. 43-64. Univer- sity of Tokyo Press, Tokyo. Blow, W. H., 1969: Late Middle Eocene to Recent planktonic foraminiferal biostratigraphy. /n, Bronnimann, P. and Renz, H. 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Yabe, H. and Hirayama, R., 1998: Selachian Fauna from the upper Miocene Senhata Formation, Boso Peninsula, central Japan. Natural History Research, Special Issue, no. 6, p. 33-61. 2177, | Paleontological Research, vol. 6, no. 2, pp. 219-236, June 28, 2002 © by the Palaeontological Society of Japan Internal test morphology of the genus Rectobolivina (Cushman, 1927) from the Late Cenozoic Miyazaki Group, southwestern Japan SHUNGO KAWAGATA' AND AKIO HATTA’ Marine Core Research Center, Kochi University, Akebono-cho 2-5-1, Kochi, 780-8520, Japan (e-mail: kawagata@cc.kochi-u.ac.jp) *Faculty of Education, Kagoshima University, Korimoto 1-20-6, Kagoshima, 890-0065, Japan (e-mail: hatta@ edu.kagoshima-u.ac.jp) Received September 9, 2001; Revised manuscript accepted March 18, 2002 Abstract. Six species of the genus Rectobolivina (benthic foraminifera), R. asanoi, R. bifrons, R. clavata, R. discontinuosa, R. raphana and R. striatula from the Late Cenozoic Miyazaki Group of southwestern Japan were taxonomically studied, particularly focusing on internal test morphology. Two new species of Rectobolivina, R. clavata and R. discontinuosa, and one new replacement name, Rectobolivina clavatostriatula, are proposed. Scanning electron microscopic and optical microscopic observations of dissected specimens and thin sections reveal that the chamber wall of the genus Rectobolivina is bilamellar, and that the toothplate is an extension of the chamber wall, a twisted plate strongly folded at both edges and connecting successive foramina. preceding foramen. The toothplate constantly attaches with one of its sides to the axial side of the inner margin of the It exhibits a lamellar structure, showing that the extension of the outer lamella of the chamber wall is covered by two thin inner lamellae on both axial and peripheral sides. The six species of Rectobolivina display a clear stratigraphically separated distribution during the period from latest Miocene to earliest Pleistocene. Key words: benthic foraminifera, internal morphology, lamellar structure, Miyazaki Group, Rectobolivina, toothplate Introduction The current classification scheme of benthic foraminifera requires examination of the internal test morphology (Loeblich and Tappan, 1987). This is mainly caused by the development of scanning electron microscopy (SEM) since the 1960's and of techniques for dissecting speci- mens. The genus Rectobolivina proposed by Cushman (1927) differs from the genus Siphogenerina Schlumberger, 1882 by its biserial chamber arrangement in the earlier stage, in contrast to the triserial one in Siphogenerina. Hofker (1951a) indicated the importance of the toothplate of Rectobolivina at generic level, and Hofker (1951b) pointed out the difference of toothplate orientation between Rectobolivina and Siphogenerina. The current classifica- tion (Loeblich and Tappan, 1964, 1987) adopted the signifi- cance of the toothplate orientation. Although Revets (1993) briefly described the monolamellar structure in the toothplate of the genus Siphogenerinoides Cushman, 1927, orientation as toothplate in which shows the same toothplate Rectobolivina, the structure of the Rectobolivina has not yet been described. The present paper deals with the taxonomy of Rectobolivina species from the Late Cenozoic Miyazaki Group, with emphasis on the nature of the toothplate. Geologic settings On the coastal region of Miyazaki Prefecture, southeast Kyushu, Late Cenozoic marine deposits named the Miyazaki Group are widely distributed. The Miyazaki Group unconformably overlies the Paleogene unit of the Shimanto Supergroup. Shuto (1952) divided the Miyazaki Group into three facies, the Aoshima, the Miyazaki, and the Tsuma facies from south to north, based on lithological dif- ferences and on their geographic distribution. The rela- tionship among these facies has been thought to be contemporaneous. Shuto (1952) divided the Tsuma facies into three members, the Kawabaru, the Tsuma, and the 220 Shungo Kawagata and Akio Hatta LEGEND [BER] Terrace deposits EJTakanabe M. E [III sadowara * E=]Tsuma M. Pete Kawabaru M. |: Shimanto Supergroup Koyu F to Fm = © 5 © N © = = Sa Figure 1. Takanabe Member in ascending order. The Tsuma facies was reclassified and subdivided into four members by Suzuki (1987) as follows: the Kawabaru and Tsuma Members of the Saito Formation, and the Sadowara and Takanabe Members of the Koyu Formation in stratigraphic order (Figure 1). The geologic age of the group was pre- viously assigned to latest Miocene to earliest Pleistocene based on planktonic foraminifera by Natori et al. (1972) and calcareous nannoplankton by Nishida (1980). The Tsuma facies is well exposed at the terrace cliffs along the Hitotsuse-gawa River. We collected 59 sedi- ment samples for this study from this section (Figure 2). stone alternation were selected for sampling. Omaru-gawa Hitotsuse-gawa River Pacific Ocean Geologic map of the study area (modified after Suzuki, 1987). Materials and methods Lithology and horizons of foraminifera-bearing rock samples in the section along the Hitotsuse-gawa River are shown in Figure 3. The pelitic layers in a siltstone/sand- Rock sam- ples were disintegrated with an oversaturated sodium sulfate (Na:SO:) solution following the method of Ujiie et al. (1977) and were washed using a 74 um sieve. Rectobolivina specimens were picked out from the sedi- ment residue on the sieve and identified with optical and scanning electron microscopes (SEM). A number of megalospheric specimens were dissected and observed under SEM following Nomura’s (1983) Canada balsam- Internal test morphology of Rectobolivina 221 1km MG23 oo MG25 ce — G28 1 MG30 Nyutabaru MG50 MG49 MG47 MG48 Figure 2. xylene embedding method to examine the internal test structures. All the illustrated specimens are deposited in the collec- tions of the University of Tsukuba with catalog number prefixed IGUT. Brief note on stratigraphic occurrence Rectobolivina asanoi Murata, 1951, R. bifrons (Brady, 1881), R. clavata sp. nov., R. discontinuosa sp. nov., R. raphana (Parker and Jones, 1865), and R. striatula (Cushman, 1913) were recognized in 35 sampling horizons (Figure 4). As shown in Figure 5, the stratigraphic distri- bution and the frequency of occurrence of these species are different in the study section. R. asanoi characteristically occurs only in the Kawabaru Member of uppermost Miocene age. R. bifrons and R. striatula occur at two ho- Pacific MG51 Hitotsuse-gawa River Map showing sampling localities. rizons in the upper part of the Kawabaru Member and in the lower part of the Tsuma Member, while R. clavata sp. nov. is characteristic at two horizons, one in the upper part of the Tsuma Member and another in the lower part of the Sadowara Member. R. raphana occurs in the Takanabe Member. R. discontinuosa sp. nov. is restricted to the low- est Pleistocene horizon of the Takanabe Member. Possibly, these stratigraphic distributions of the species may offer clues for the restricted but detailed correlation of Strata in a further study. Previous studies on toothplate of Rectobolivina Although Brady (1881, 1884) did not mention the exis- tence of the toothplate in the original description of Sagrina bifrons (type species of Rectobolivina), Cushman (1913) described “the internal tubular connection” of R. bifrons 222 Shungo Kawagata and Akio Hatta 0 2 Q N 5 8 © © o 3:83:98 5s ÉE SE 2 3 © s5 3 6 os = Lu L fo ao FT ST [ss MG57 | Legend Mase | |terrace deposits = mass | sandy siltstone 8 OMGS alternation of siltstone & © —.. sandstone c ES siltstone 2 E¥$#H fine-grained sandstone £ o MG53 midium-grained sandstone R MG52 -e Rectobolivina bearing = -o Rectobolivina absent £ = no foraminifera g MG51 © Fe OT MG50 Fm. Formation 5 TH MG49 M. Member © AP el Sele © = £ 2\a 2 £ ke 1,000 (m) = 3 17 q 500 $ œ | © A ric . Ÿ z|$ = 8] |» 2 3 5 | | Shp © R333 x | 0 R rt Figure 3. Geologic columnar section with the sampling levels. Stratigraphic division and thickness calculation are based on Suzuki (1987), and geologic age and planktonic foraminiferal zones are after Natori et al. (1972). (his Siphogenerina bifrons) based on observations by opti- cal microscopy. Cushman (1927, 1937) described the toothplate as “tube” or “tubular”, and Hofker (1933) called it an “internal tube”. Later, Hofker (1951a) examined toothplates of foraminifera including Rectobolivina species, and stated, “...in the biserial part of Rectobolivina, this plate is fastened at one side of the aperture of the former cham- ber, and is erected in such way, that, by contorting itself, it is attached to the opposite side of the chamber itself, giving rise to a tooth by means of its folded and flaring side...”. He (fig. 35) illustrated in detail the schematic succession of toothplates in relation to the chamber arrangement for some Rectobolivina species, particularly for Rectobolivina columellaris (Brady). He first showed that the toothplate of the genus is not a cylindrical tube but is a hemi- cylindrical plate. Hofker (1951b) showed the different modes of toothplate orientation in Rectobolivina and its re- lated genus Siphogenerina; the angle between successive toothplates in Rectobolivina is constantly 180°, whereas it is 120° in Siphogenerina. Thus, the morphology and suc- cession of the toothplates are now regarded as important taxonomic features. Loeblich and Tappan (1964) adopted Hofker’s (1951b) opinion in their classification scheme of foraminifera and placed Rectobolivina into the family Bolivinitidae Cushman, 1927. They used the term “tooth- plate” only for the superfamily Buliminoidea (= their Buliminacea). Later, Loeblich and Tappan (1987) moved Rectobolivina into the subfamily Siphogenerinoidinae Saidova, 1981. The Siphogenerinoidinae consists of 11 genera, including Rectobolivina but not Siphogenerina, which are characterized by biserial chamber arrangement in earlier stage becoming uniserial in later stage, associated with the toothplate rotating 180° between chambers. Loeblich and Tappan (1987) defined the toothplate as an extension of the chamber wall and a contorted plate extend- ing within the chamber lumen. Recently, Revets (1989, 1993, 1996) pointed out that the toothplate of the Buliminoidea (= his Buliminacea) (including Rectoboli- vina) originated from the inner layer of a bilamellar cham- ber wall, and he distinguished it from the so-called “tooth- plate” in the Rotalioidea, which shows a more complicated Structure. Toothplate in Rectobolivina Megalospheric specimens were vertically sectioned in two ways (Figure 6); i.e. cut through the broader diameter of test (Section A) and perpendicularly (section B). The following description can be applied to all species treated here. The relationship among toothplate, foramen and chamber lumen is schematically shown in Figure 7. The aperture of Rectobolivina species is elliptical to cir- cular in outline and its top fuses to the apertural lip, which never distinctly protrudes (Figure 4). The toothplate is ap- parently thin and trough-shaped, strongly folded at its side edges as seen in section A (e.g. Figures 8.2, 11.7). The plate in the uniserial stage descends straight into the cham- ber lumen towards the preceding foramen, along the center of the test (e.g. Figure 10.5), whereas it extends in a zigzag way in the biserial stage, according to the biserial chamber arrangement (e.g. Figure 10.5). The trough-shaped con- cavity (tc) of the toothplate appears alternately from cham- ber to chamber in both biserial and uniserial stages (e.g. Figure 8.2). This indicates that the toothplate retains the early ontogenic biserial (= 180°) rotation, although cham- Internal test morphology of Rectobolivina 223 bers become uniserial. After slight etching with dilute hydrochloric acid solu- tion, the chamber wall of R. bifrons (type species of the genus) shows a lamellar structure (Figure 8.5). The later chamber wall entirely covers the preceding ones, causing the thickening of the test wall in the earlier portion. The final chamber wall of R. raphana (Figure 11.4) is bilamellar, consisting of a thin inner lamella (il) and a thick outer lamella (ol). A similar lamellar structure can be seen in the toothplate (tp) of R. bifrons (Figure 9.2, 9.3), where a thick outer lamella (ol) is covered by a thin inner lamella (il) at both the axial and peripheral sides. In conclusion, it can be stated that the lamellae of the toothplate do not originate in the preceding toothplate nor septal wall, but represent an extension of the chamber wall (Figures 8.1, 9.2, 9.3, 9.5, 9.6). These observations on the lamellar structure of the toothplate differ from those by Revets (1989, 1993), who regarded the toothplate as an extension of the inner lining (= inner lamella in this study) of the chamber wall. Our observation of the internal, lamellar structure in the genus Rectobolivina ıs summarized in Figure 12, and sup- ports Hofker’s (1951a) idea that the toothplate is a part of the chamber wall. Systematic description Family Siphogenerinoidae Saidova, 1981 Subfamily Siphogenerinoidinae Saidova, 1981 Genus Rectobolivina Cushman, 1927 Rectobolivina asanoi Murata, 1951 Figures 4.1a-c, 4.2a-c; 10.1, 10.2; 13.1a, b Rectobolivina asanoi Murata, 1951, p. 96, pl. 1, text-figs. 2a, b; Asano, 1952, p. 13, figs. 70, 71; Kawagata, 2001, p. 88, figs. 8-13a, b. Rectobolivina bifrons striatula (Cushman) (non Siphogenerina bifrons (Brady) var. striatula Cushman, 1917). Asano, 1950, p. 12, figs. 48, 49; Matsunaga, 1963, pl. 41, figs. 9a, b. Material. —-IGUT14488, sample MKO7(Figure 4.la-c); IGUT14489, sample MKO7(Figure 4.2a-c); IGUT14490, sample MK07 (Figure 10.1); IGUT14491, sample MK07 (Figure 10.2). Remarks.—Since Murata (1951) described Rectobolivina asanoi from the Miocene part of the Miyazaki Group, this species has been reported only from the late Neogene Shimajiri Group in Kume-jima Island, southwestern Japan (Kawagata, 2001). Comparing the original figure of R. asanoi Murata, 1951 (Figure 11.1a) to other costate Rectobolivina species, the former species is characterized in having a much wider test, and being elliptically rounded in cross section. À. bifrons var. striatula (Cushman, 1917) of Suzuki (1987) from the lower part of the Miyazaki Group, south of the present study area, of Asano (1950) from the Pliocene Kakegawa Group, central Japan, and of Matsunaga (1963) from the Pliocene in Niigata Prefecture, northeastern Japan, are all probably identical to R. asanoi. The specimens treated here resemble those described as R. striatula (Cushman, 1917) from the late Neogene of New Zealand (Hornibrook, 1968; Hayward and Buzas, 1979) and from the Miocene of Victoria, Australia (Carter, 1964), and those described as R. striatula (Cushman, 1913) of Kennett (1966) from the late Neogene of New Zealand. However, these Southern Ocean species show cylindrical tests with numerous fine longitudinal striations (Carter, 1964; Kennett, 1966) or with fewer costae (Hornibrook, 1968; Hayward and Buzas, 1979), in contrast to the rather compressed test with a number of raised longitudinal costae in R. asanoi. The megalospheric form of R. asanoi shows a bluntly rounded initial end and approximately four to five pairs of chambers in the biserial stage (Figure 4.1a, c), whereas the microspheric form has a rather tapered initial end and more chamber pairs in the earlier stage (Figure 4.2a, c). There is no distinct size difference between the forms. Rectobolivina bifrons (Brady, 1881) Figures 4.3a-c, 4.4a-c; 8.2-8.5; 9.1-9.6; 13.2-13.4b Sagrina bifrons Brady, 1881, p. 64; Brady, 1884, p. 582, pl. 75, figs. 18-20. Siphogenerina bifrons (Brady). Cushman, 1913, p. 103, pl. 45, figs. la-2, 5-7; Cushman, 1921, p. 277, pl. 56, figs. 2, 3; Cushman, 1926, p. 16, pl. 3, figs. 7-9, pl. 4, fig. 4. Rectobolivina bifrons (Brady). Cushman, 1927, p. 68, pl. 14, fig. 11; Cushman, 1937, p. 204, pl. 23, figs. 13, 14a, b; Asano, 1938, p. 606, pl. 16, figs. 11a, b; Asano, 1950, p. 11, figs. 46, 47; Asano, 1958, p. 28, pl. 5, figs. 10, 11; Kuwano, 1962, pl. 21, fig. 6; Huang, 1964, pl. 2, fig. 28; Ishiwada, 1964, pl. 4, fig. 68; Kikuchi, 1964, pl. 3, fig. 23; Belford, 1966, p. 45, pl. 9, figs. 13, 14; Inoue, 1989, pl. 28, fig. 6. ? Siphogenerina (Sagrina) bifrons (Brady). Egger, 1893, p. 317, pl. 4, figs. 25, 26, 29. ? Rectobolivina bifrons (Brady). Matsunaga, 1963, pl. 41, figs. 8a, b; Saidova, 1975, pl. 86, figs. 9, 10. not Rectobolivina bifrons (Brady). LeRoy, 1964, p. F34, pl. 3, figs. 1, 2; Loeblich and Tappan, 1964, p. C553, fig. 438, nos. 2a-5b. not Rectobolivina cf. bifrons (Brady). McCulloch, 1977, p. 259, pl. 107, figs. 17a, b. Material. -IGUT14492, sample MK19 (Figure 4.3a-c); IGUT14493, sample MK19 (Figure 4.4a-c); IGUT14494, sample MK19 (Figure 8.2); IGUT14495, sample MK19 ner ee he Shungo Kawagata and Akio Hatta Internal test morphology of Rectobolivina 225 Foraminiferal Zones Geologic Age Planktonic Formation Member Lithology 07 (2.74.56 58% 0 2 4 6% 0 0.2 0.4% Legend Takanabe M. EI terrace deposits sandy siltstone E— siltstone PTT. - HE fine-grained sandstone R. discontinuosa sp. nov. alternation of siltstone & sandstone © 8 = = Q cps ° 5 a 3 5 midium-grained sandstone SQ © & < Fm. Formation S = Ss = M. Member Q Q (7) x x x x X > O = ro (7) RB e > 8 x = o = . j X 10 20 30% 2 4 6% 0 5 10 15 20% Figure 5. Stratigraphic occurrence and percentage abundance of six Rectobolivina species in the study section of the Miyazaki Group. @ Figure 4. la-c. Megalospheric form of Rectobolivina asanoi (Murata), IGUT14488, la: side, 1b: apertural views, x60. Ic: Optical micro- photograph of la, x60. 2a-c. Microspheric form of Rectobolivina asanoi (Murata), IGUT 14489, 2a: side, 2b: apertural views, x60. 2c: Optical mi- crophotograph of 2a, x60. 3a-c. Megalospheric form of Rectobolivina bifrons (Brady), IGUT 14492, 3a: side, 3b: apertural views, x60. 3c: Optical microphotograph of 3a, x60. 4a-c. Microspheric form of Rectobolivina bifrons (Brady), IGUT14493, 4a: side, 4b: apertural views, x60. 4c: Optical microphotograph of 4a, x60. 5a-c (holotype), IGUT14499, and 6a-c (paratype), IGUT14500. Megalospheric form of Rectobolivina clavata sp. nov., 5a: side, 5b: apertural views, x60. Sc: Optical microphotograph of 5a, x60; 6a: side, 6b: apertural views, x50. 6c: Optical microphotograph of 6a, x50. 7a-c. Microspheric form of Rectobolivina clavata 2p. nov, IGUT14501, 7a: side, 7b: apertural views, x50. 7c: Optical microphotograph of 7a, x50. 8a-c. Megalospheric form of Rectobolivina discontinuosa sp. nov. (holotype), IGUT14504, 8a: side, 8b: apertural views, x50. 8c: Optical microphotograph of 8a, x50. 9a-c. Microspheric form of Rectobolivina discontinuosa sp. nov. (paratype), IGUT14505, 9a: side, 9b: apertural views, x50. 9c: Optical microphotograph of 9a, x50. 10a-c and 11a-c. Megalospheric form of Rectobolivina raphana (Parker and Jones), IGUT 14508 and IGUT 14509, 10a: side, 10b: apertural views, x50. 10c: Optical microphotograph of 10a, x50; 11a, IGUT14509: side, 11b: apertural views, x50. 1 1c: Optical microphotograph of 11a, x50. 12a-c. Megalospheric form of Rectobolivina striatula (Cushman), IGUT14513, 12a: side, 12b: apertural views, x50. 12c: Optical microphotograph of 12a, x50. 226 Shungo Kawagata and Akio Hatta Section A Section B Figure 6. Diagram showing the two sections of a foramini- feral test used in this study. (Figure 8.3); IGUT14496, sample MK19 (Figure 8.4); IGUT14497, sample MK19 (Figures 8.5, 9.1-9.2); IGUT 14498, sample MK19 (Figures 9.4-9.5). Remarks.—This species was first described by Brady (1881) from off the Pacific coast of central Japan, and the original figures by Brady (1884) are reproduced in Figure 13.2-13.4b. Cushman (1913) examined both megalo- spheric and microspheric forms of the species and pointed out that all Brady’s original figures represent megalospheric forms. Many specimens treated here are megalospheric forms (e.g. Figure 4.3a-c), which compare well with Brady’s original figures. The megalospheric form is much shorter than the microspheric one, because of the reduced chamber number at the biserial stage. Rectobolivina clavata sp. nov. Figures 4.5a-c, 4.6a-c, 4.7a-c; 10.3, 10.4 ? Rectobolivina bifrons (Brady). LeRoy, 1964 (non Sagrina | aperture | QT A (foramen) toothplate relict foramen Figure 7. A schematic sketch of the Rectobolivina species showing the relationship among toothplate, foramina and chamber lumina in the uniserial stage. Terms follow Revets (1989, 1993). bifrons Brady, 1881), p. F34, pl. 3, figs. 1, 2. Diagnosis.—A species of Rectobolivina with a clavate- shaped and inornate test. Description. — Test free, moderate size, approximately four times as long as broad, straight, clavate in shape, ellip- tical in being laterally depressed in cross section, initial end bluntly rounded in megalospheric form, whereas initial end pointed in microspheric form; chambers numerous, breadth twice the height, gradually increasing in size added chang- ing from uniserial to biserial, after the third chamber in megalospheric form or after the tenth chamber in micro- spheric form; wall calcareous, optically radial, transparent or semitransparent, finely perforate, rather thick, sometimes very weakly striate in later part of test; sutures distinct, moderately thick, slightly depressed; aperture terminal, nearly circular to elliptical opening, with a distinct but slightly protruding lip; intercameral septa thick as well as the wall, parallel to slightly arched; toothplate folded at the lateral edge, extending into the preceding aperture (fora- men), its folded face arranged alternately in planes 180° apart. Material.—Holotype: IGUT14499 (1.03 mm in length, Internal test morphology of Rectobolivina 227 Figure 8. Sections of the microspheric form of Rectobolivina raphana (Parker and Jones) (8.1) and the megalospheric forms of Rectobolivina bifrons (Brady) (8.2-8.5), IGUT14494- IGUT14497. 1. Overall view of Section B (Figure 6). Arrows indicate the attached portion of the toothplates, which never continuously extend from the preceding toothplate or septa, x143. 2. Overall view of Section A. Concave side of trough shaped plate (tc) which rotates 180° between chambers, x180. 3. A part of the uniserial stage in Section B. Foramen (f) opens alternately along toothplate (tp). Toothplate always runs along the centre of chamber lumen, x350. 4. Oblique section showing relationship between foramen and toothplate, x250. 5. A part of test wall showing lamellar development of test wall according to test growth. Final chamber wall (fw) covers wall of penultimate chamber (pw), and pw covers over the pre-penultimate chamber wall (ppw), x500 228 Shungo Kawagata and Akio Hatta Figure 9. Megalospheric forms of Rectobolivina bifrons (Brady). 9.1, 9.2, IGUT14497. 1. Oblique view of later part of test of the same specimen shown in Figure 8.5, x450. 2, 3. Close-up photograph and its sketch, showing lamellar structure of toothplate (tp) in the penultimate cham- ber. A thick outer lamella (ol) is intercalated with two inner lamellae (il), and attaches to pre-penultimate chamber wall (ppw) composed of previous outer (pol) and inner layers (pil), x800. 4, 5. IGUT14498, 4. A part of the uniserial stage in Section B (Figure 6), x180. 5, 6. Close-up photograph and its sketch, are showing the attachment portion of toothplate (tp). Toothplate (tp), a part of chamber wall (w), is separated from next toothplate (ntp) which is a part of next chamber wall (nw), x700. 299 Internal test morphology of Rectobolivina Figure 10. All dissected specimens are the megz 1, 2. Sections A and B (see Figure 6) of Rectobolivina asanoi (Murata). IGUT 14490 and IGUT14491. x150 and 200. 3, 4. Sections A and B of Rectobolivina clavata Sp. nov., respectively, IGUT14502 and x150 and 200 5. 6. Sections A and B of Rectobolivina discontinuosa p. nov., respectively, IGUT14506 and IGUT14507. x120 ig the relationship among toothplate (tp), foramen (f) and relict foramen (rf). x250 Shungo Kawagata and Akio Hatta Internal test morphology of Rectobolivina 23] final chamber penultimate chamber pre-penultimate chamber Figure 12. A schematic figure of the lamellar structure of the test wall and the toothplate in Section B (see Figure 6), showing fora- men (f), toothplate (tp), outer lamella (ol), inner lamella (il), and relict foramen (rf). The terms used in the figure mostly follow Revets (1989, 1993). 0.36 mm in maximum breadth), sample MK48 (Figure 4.5a-c). Paratypes: IGUT14500 (0.92 mm in length, 0.32 mm in maximum breadth), sample MK48 (Figure 4.6a-c); IGUT14501 (1.08 mm in length, 0.34 mm in maximum breadth), sample MK48 (Figure 4.7a-c); IGUT 14502, sam- ple MK48 (Figure 10.3); IGUT14503, sample MK48 (Figure 10.4). Etymology.—The specific name, clavata, is derived from the clavate-shape of the test. Remarks.—This new species has a more slender and more clavate-shaped test than R. bifrons (Brady). According to measurements of the test width (TW) in megalospheric forms of R. bifrons and R. clavata (Figure 14), the test width of R. clavata becomes narrowest at the fourth chamber, whereas that of R. bifrons constantly in- creases (Figure 15). Furthermore, the former has a single pair of biserial chambers, whereas the latter has several pairs of biserial chambers. À. clavata differs from Rectobolivina columellaris (Brady, 1881) in having a more compressed test, in contrast to the cylindrical test of the latter species. An Australian Rectobolivina species, des- cribed as Sagrina sydneyensis by Goddard and Jensen (1907), differs from R. clavata in having ornamentation with minute spines and some large pores. Rectobolivina striatula (Cushman, 1913) Figures 4.12a-c; 11.6, 11.7; 13.11a, b Siphogenerina striatula Cushman, 1913, p. 108, pl. 47, fig. 1. Rectobolivina bifrons (Brady) var. striatula (Cushman, 1917). LeRoy, 1964 (non Siphogenerina bifrons (Brady) var. striatula Cushman, 1917, nomen nudum), p. F34, pl. 3, figs. 510: ? Rectobolivina bifrons (Brady) var. striatula (Cushman, 1917). LeRoy, 194la (non Siphogenerina bifrons (Brady) var. striatula Cushman, 1917, nomen nudum), p. 35, pl. 2, figs. 7, 8. not Rectobolivina striatula (Cushman, 1917) (non Siphogenerina 1917, nomen nudum). Carter, 1964, p. 69, pl. 2, figs. 35, 36; Hornibrook, 1968, p.73, fig. 13 (part), Hayward and Buzas, 1979, p. 72, pl. 26, figs. 320, 321. not Rectobolivina striatula (Cushman, 1913). Kennett, 1966 (non Siphogenerina striatula Cushman, 1913), p. 47, fig. 59. bifrons (Brady) var. striatula Cushman, Material. —IGUT14513, sample MK19 (Figure 4.12a- c); IGUT14514, sample MK19 (Figure 11.6); IGUT14515, sample MK19(Figure 11.7). Remarks.—All specimens of the present species from the Miyazaki Group are regarded as megalospheric forms be- cause they are characterized in having a bluntly rounded initial end (Figure 4.12a, c) and three pairs of biserial chambers at the earliest part (Figure 11.6). This species is distinguished from the other Rectobolivina species in hav- ing numerous, fine, and longitudinal striations covering the test surface (Figure 4.12a). Compared with Cushman’s (1913) original figure of the type specimen (here repro- duced in Figure 13.11a, b), our specimens have a slightly rhomboidal outline in section and an elliptically rounded aperture, in contrast to the rounded outline and rather nar- row slit-like aperture in the type specimen. + Figure 11. All dissected specimens are megalospheric forms. 1, 2. Sections A and B (see Figure 6) of Rectobolivina raphana, respectively, IGUT14510 and IGUT14511, x120 and 150. 500. ol: outer layer, il: inner layer Rectobolivina striatula (Cushman), IGUT14514, «180. tends into the chamber lumen the tube-like structure, x180 3. Section A of R. raphana, IGUT14512, x120. 5. Close-up view of the biserial part in R. raphana, x400, f: foramen, tp: toothplate, |: lip. 6. Section A of 7. Oblique view of foramen and toothplate in R. striatula, IGUT14515. 4. Close-up of final chamber wall of figure 3, x1, The toothplate ex- Its lateral edges strongly fold towards the opposite side of the preceding foramenal opening (f), but it never shows S 5 Ss ue) € Le < TD =. 3 3 = S N) 3 > S V2 © on =| 3 = un Internal test morphology of Rectobolivina 233 R. bifrons R. clavata sp. nov. TW: Test width in- Figure 14. Definition of measurements. cluding the distal chambers, n: Number of chambers from the initial to final chamber. Rectobolivina clavatostriatula nom. nov. Figure 13.5 Siphogenerina bifrons (Brady) var. striatula Cushman, 1917, p. 662 (nomen nudum); Cushman, 1919, p. 620; Cushman, 1921, p. 278, pl. 56, fig. 4; Cushman, 1926, p. 18, pl. 2, fig. 6, pl. 4, figs. 1-3. Rectobolivina bifrons (Brady) var. striatula (Cushman, 1917). Cushman, 1937, p. 205, pl. 23, figs. 17, 18. Diagnosis.—A species of Rectobolivina with a clavate- shaped test covered by distinct longitudinal striations. Etymology.—The new specific name, clavatostriatula, represents clavate test shape and distinct striations of this species. Remarks.—Cushman (1917) reported this species from the Sogod Bay (~1,000 m water depth), Philippines, under the name of Siphogenerina bifrons (Brady) var. striatula Cushman. Later, Cushman (1921, pl.56, fig.4) illustrated it (here reproduced in Figure 13.5). However, S. bifrons var. striatula Cushman, 1917 is a junior primary homonym of Siphogenerina striatula Cushman, 1913 (the original fig- ure of the holotype is reproduced in Figure 13.11a, b), re- ported from the western Pacific Ocean. The former can clearly be distinguished from the latter in having a clavate- shaped test with fewer but more raised striations on the test surface. Consequently, Rectobolivina clavatostriatula is proposed as a new name to replace S. bifrons var. striatula Cushman, 1917. Rectobolivina discontinuosa sp. nov. Figures 4.8a-c, 9a-c; 10.5-10.7; 13.6a, 13.7b Rectobolivina bifrons (Brady) (non Sagrina bifrons Brady, 1881). Loeblich and Tappan, 1964, p. C553, fig. 438, nos. 2a-5b; Loeblich and Tappan, 1987, p. 517, pl. 567, figs. 11-14 (not figs. 15-17). ? Rectobolivina bifrons (Brady) var. striatula (Cushman). Le- Roy, 1941b (non Siphogenerina bifrons (Brady) var. striatula Cushman, 1917, nomen nudum), p. 80, pl.1, fig. 9. Diagnosis.—A species with a clavate-shaped test, whose surface is covered by numerous and discontinuous stria- tions mainly on the later portion of the test. Description.—Test free, moderate size, approximately four times as long as broad, straight, clavate-shaped, ellip- tical in being laterally depressed in cross section, initial end bluntly rounded in megalospheric form, pointed in microspheric form; chambers numerous, breadth twice the height, gradually increasing in size, changing from biserial to uniserial after the seventh chamber in megalospheric forms or after the thirteenth chamber in microspheric forms; wall calcareous, optically radial, transparent or semitransparent, finely perforate, rather thick, striae numer- ous in the later part of the test but much sparser in the ear- lier part of the test; sutures distinct, moderately thick, slightly depressed or flush; aperture terminal, nearly circu- lar to elliptical, with a distinct lip; intercameral septa thick as well as the wall, parallel to slightly arched; toothplate folded at the side edge, extending into the preceding aper- ture (foramen), its folded face arranged alternately in posi- tion in planes 180° apart. @ Figure 13. Reproduction of original figures of the studied species. la. b. Rectobolivina asanoi Murata, 1951, x135. 2-4b. Rectobolivina bifrons (Brady, 1881), after Brady (1884), x71. Rectobolivina clavatostriatula nom. nov., x66. 5. Siphogenerina bifrons (Brady) var. striatula Cushman, 1917, after Cushman (1921) = 6a-7b. Rectobolivina bifrons (Brady, 1881) of Loeblich and Tappan (1964) = Rectobolivina discontinuosa sp. nov., x66. 6a, b: megalospheric, 7a, b: microspheric forms. 8a-10b. Rectobolivina raphana (Parker and Jones, 1865) of Loeblich and Tappan (1964), x55. lla, b. Siphogenerina striatula Cushman, 1913, x75. 234 Shungo Kawagata and Akio Hatta o_O — —©—©—7© ¥ -V- Vv ON NN ¥-¥ -¥-¥ OV A VTT — 7 Æ RR A OK —x— % # —K —X— N —X —X hh ttt ttt © + —+—+— + +—- =-E-#--B-2-#-E-0- u @--@---@--@---@-- @---# -- 0---e --0---e--© be à —A— À ah A À A A A A —4— à —41 specimens test width (mm) 1 289 4 5 GO 7 8 9 10 11 12 13 14 15 number of chambers 11 1 1 07 o} SRE 4 = nd suewioeds biserial part uniserial part (ww) yıpım Is} R. clavata sp. nov. (megalospheric) b 9 10 11 12 13 14 15 1 289 490807 8 number of chambers Figure 15. Test width changes in the megalospheric forms of Rectobolivina clavata sp. nov. (n = 5) and R. bifrons (n = 11) through ontogeny. Arrow indicates the position where the test width of R. clavata becomes the narrowest. Material.—Holotype: IGUT14504 (0.98 mm in length, 0.31 mm in maximum breadth), sample MK57 (Figure 4.8a-c). Paratypes: IGUT14505 (1.05 mm in length, 0.31 mm in maximum breadth), sample MK57 (Figure 4.9a-c); IGUT14506, sample MK57 (Figure 10.5); IGUT14507, sample MK57 (Figure 10.6, 10.7). Etymology.— The new specific name, discontinuosa, comes from the discontinuous striations of the test. Remarks.—The specimens treated here (Figures 4.8a-c, 9a-c) are compared well with those of Loeblich and Tappan’s (1964, 1987) Rectobolivina bifrons (here repro- duced in Figures 13.6a-7b) in having a clavate-shaped test ornamented by distinct, discontinuous striations. This dis- continuous striation is clearly distinguished from the com- pletely continuous striation in typical Rectobolivina clavatostriatula (Figure 13.5) and from the inornate test of Rectobolivina clavata (Figure 4.5a-c, 4.6a-c, 4.7a-c). Therefore, we judge our specimens to belong to a new spe- cies and not to either of the latter two species. This new species differs from Rectobolivina asanoi Murata, 1951 by its more slender and clavate-shaped test with less raised striations on the test surface. Rectobolivina raphana (Parker and Jones, 1865) Figures 4.10a-c, 4.11a-c; 8.1; 11.1-11.5; 13.8a-13.10b Uvigerina (Sagrina) raphanus Parker and Jones, 1865, p. 364, pl. 18, figs. 16, 17. Sagrina raphanus (Parker and Jones). Brady, 1884, p. 585, pl. 75, figs. 21-24. Siphogenerina (Sagrina) raphanus (Parker and Jones). Cushman, 1913, p. 108, pl. 46, figs. 1-5. Siphogenerina raphanus (Parker and Jones). Cushman, 1921, p. 280, pl. 56, fig. 7; Cushman, 1926, p. 4, pl. 1, figs. 3, 4 (? figs. 1, 2), pl. 2, figs. 1-3, 10, pl. 5, figs. 1, 2; Cushman, 1942, p. 55, pl. 15, figs. 8, 9 (not figs. 6, 7); Hofker, 1951a, p. 233, figs. 155, 156; LeRoy, 1964, p. F35, pl. 3, fig. 35. Siphogenerina raphana (Parker and Jones). Hada, 1931, p. 134, text-figs. 91a, b; Asano, 1950, p. 14, figs. 56, 57; Asano, 1958, p. 30, pl. 7, figs. 8-10; Kuwano, 1962, pl. 22, fig. 5; Ishiwada, 1964, pl. 5, fig. 81. Rectobolivina raphana (Parker and Jones). Loeblich and Tappan, 1964, p. 533, fig. 438-9-11; Matoba, 1970, p. 60, pl. 3, fig. 31; Whittaker and Hodgkinson, 1979, p. 56, fig. 8; Matoba and Honma, 1986, pl.4, figs.6a, b; Matoba and Fukusawa, Internal test morphology of Rectobolivina 23 1992, p. 218, fig. 9-6. ? Siphogenerina (Sagrina) raphanus (Parker and Jones). Egger, 1893, p. 317, pl. 9, fig. 36. Material. —IGUT14508, sample MK56 (Figure 4.10a- c); IGUT14509, sample MK56 (Figure 4.1la—c); sample MKS56 (Figure 8.1); IGUT14510, sample MK56 (Figure 11.1); IGUT14511, sample MK56 (Figure 11.2, 11.5); IGUT14512, sample MKS56 (Figure 11.3, 11.4). Remarks.—All specimens treated in this study are ellipti- cally rounded in section, and in this respect, they are distin- guished from the paratypes of this species designated by Loeblich and Tappan (1964) (here reproduced in Figure 13.8a-13.10b). Unfortunately, they did not show a figure of the lectotype. As was shown in many previous descrip- tions (see the above synonym list), strongly raised costae on the entire test surface are recognized in all specimens examined (e.g. Figure 4.10a-4.11c). Acknowledgments We express our deep gratitude to Hiroshi Ujiié, Takushoku University, for his critical reading of the manu- script and many useful taxonomic comments. We grate- fully acknowledge Stefan A. Revets, University of Western Australia and Johann Hohenegger, Geozentrum Universitat Wien for their kind pre-reviewing of the manuscript and constructive comments. We are sincerely indebted to Shuko Adachi of University of Tsukuba for her kind tech- nical support in making thin sections of foraminiferal tests. Reviews by George H. Scott of Institute of Geological and Nuclear Sciences, New Zealand, and an anonymous referee improved the manuscript. Parts of samples utilized in this study were collected by Yoshiaki Yoshimura and Hiroshi Oi, who are former students of A. Hatta. References Asano, K., 1938: On the Japanese species of Bolivina and its allied genera. Journal of the Geological Society of Japan, vol. 45, no. 538, p. 600-609. Asano, K.. 1950: Illustrated Catalogue of Japanese Tertiary Smaller Foraminifera, Part 2, Buliminidae. Hosokawa Print- ing Co., Tokyo, p. 1-19. Asano, K., 1952: Illustrated Catalogue of Japanese Tertiary Small- er Foraminifera, Supplement No. 1. Hosokawa Printing Co. Tokyo, p. 1-17. Asano, K.. 1958: The foraminifera from the adjacent seas of Japan, collected by the S. S. Soyo-maru, 1922-1930: Pt. 4, Buliminidae. 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Proceedings of the Geological Society of China, no. 7, p. 63-72. Inoue, Y., 1989: Northwest Pacific foraminifera as paleoenviron- mental indicators. Science Report, Institute of Geoscience, University of Tsukuba, Section B, vol. 10, p. 57-162. Ishiwada, Y., 1964: Benthonic foraminifera off the Pacific coast of Japan referred to biostratigraphy of Kazusa Group. Report of Geological Survey of Japan, no. 205, p. 1-45. Kawagata, S., 2001, Late Neogene benthic foraminifera from Kume-jima Island, central Ryukyu Islands, southwestern Japan. Science Report, Institute of Geoscience, University of Tsukuba, Section B, vol. 22, p 61-123. Kennett, J. P., 1966: Stratigraphy and fauna of the type section and neighboring sections of the Kapitean Stage, Greymouth, New Zealand. Transactions of the Royal Society of New Zealand, Geology, vol. 4, no. 1, p. 1-77. Kikuchi, Y., 1964: Biostratigraphy of the Neogene and Quaternary deposits based on the smaller foraminifera in the southern Kanto region. Contributions from the Institute of Geology and Paleontology, Tohoku University, no. 59, p. 1-36. (in Japanese with English abstract) Kuwano, Y., 1962: Foraminiferal biocoenoses of the seas around Japan: A survey of Pacific-side biocoenoses. Miscellaneous Reptorts of the Research Institute for Natural Resources, nos. 58-59, p. 116-138. LeRoy, L. W., 1941a: Smaller foraminifera from the Late Tertiary of the Nederlands East Indies. Pt. 1, Small foraminifera from the Late Tertiary of the Sangkoelirang Bay area, East Borneo, Nederlands East Indies. Colorado School of Mines Quarter- ly, vol. 36, no. 1, p. 11-62. LeRoy, L. W., 1941b: Smaller foraminifera from the Late Tertiary of the Nederlands East Indies. Pt. 2, Small foraminifera from the Late Tertiary of Siberoet Island, off the west coast of Sumatra, Nederlands East Indies. Colorado School of Mines Quarterly, vol. 36, no. 1, p. 63-105. LeRoy, L. W., 1964: Smaller foraminifera from the late Tertiary of southern Okinawa. U.S. Geological Survey Professional Paper, no. 454-F, p. 1-58. Loeblich, A. R., Jr. and Tappan, H., 1964: Sarcodina Chiefly “The camoebians” and Foraminiferida, vol. 1 and 2. Jn, Moore, R. C. ed., Treatise on Invertebrate Paleontology, Part C, Protista 2, p. C1-C900. Geological Society of America and University of Kansas Press. Loeblich, A. R., Jr. and Tappan, H., 1987: Foraminiferal genera and their classification. 970 p. and 847 pls. Van Nostrand Reinhold Company, New York. Matoba, Y. 1970: Distribution of Recent shallow water foraminifera of Matsushima Bay, Miyagi Prefecture, Northeast Japan. Science Report of Tohoku University, Series 2 (Geology), vol. 42, no. 1, p. 1-85. Matoba, Y. and Fukusawa, K., 1992: Depth distribution of Recent benthic foraminifera on the continental shelf and uppermost slope off southern Akita Prefecture, Northeast Japan (the east- ern Japan Sea). Jn, Ishizaki, K. and Saito, T. eds., Century of Japanese Micropaleontology, p. 207-226. Terra Scientific Publishing Company, Tokyo. Matoba, Y. and Honma, N.: 1986, Depth distribution of Recent benthic foraminifera off Nishitsugaru, eastern Sea of Japan. In Matoba, Y. and Kato, M. eds., Studies on Cenozoic benthic foraminifera in Japan, p. 53-78. Mining College, Akita University. Shungo Kawagata and Akio Hatta Matsunaga, T., 1963: Benthonic smaller foraminifera form the oil fields of Northern Japan. Science Report of Tohoku University, 2nd series. (Geology), vol. 35, no. 2, p. 67-122. McCulloch, I., 1977: Qualitative Observations on Recent Fora- miniferal Tests with Emphasis on the Eastern Pacific, Parts 1-3, 1079 p. University of Southern California, Los Angeles. Murata, S., 1951: On the paleo-ecological investigation of the fossil foraminiferal fauna in the Miyazaki Group, with description of new species. Bulletin of the Kyushu Institute of Technology, no. 1, p. 91-104. Natori, H., Fukuta, O. and Ishida, M., 1972: Younger Cenozoic planktonic foraminiferal biostratigraphy in Okinawa and Miyazaki Prefectures, Japan (Preliminary Report). Journal of the Japanese Association of Petroleum Technologists, vol. 37, no. 7, p. 416-421. (in Japanese) Nishida, S., 1980: Calcareous nannoplankton biostratigraphy of the Miyazaki Group, Southeast Kyüshü, Japan. Bulletin of Nara University of Education (Nature), vol. 29, no. 2, p. 65-79. (in Japanese with English abstract) Nomura, R., 1983: An embedding technique for observation of in- ternal microfossil structure by scanning electron microscopy. Micropaleontology, vol. 29, no. 1, p. 1-9. Parker, W. K. and Jones, T. R., 1865: On some foraminifera from the North Atlantic and Arctic Oceans, including Davis Straits and Baffin’s Bay. Philosophical Transactions of the Royal Society, vol. 155, p. 325-441. Revets, S. A., 1989: Structure and comparative anatomy of the toothplate in the Buliminacea (Foraminiferida). Journal of Micropalaeontology, vol. 8, no. 1, p. 23-36. Revets, S. A., 1993: The foraminiferal toothplate, a review. Journal of Micropalaeontology, vol. 12, no. 2, p. 155-168. Revets, S. A., 1996: The generic revision of the Bolivinitidae Cushman, 1927. Cushman Foundation for Foraminiferal Research, Special Publication, no. 2, p. 1-55. Saidova, Kh. M., 1975: Bentosnye Foraminifery Tikhogo Okeana (Benthic foraminifera of the Pacific Ocean). vols. 1-3, 875 p. Institut Okeanologii im P. P. Shirshova, Akademiya Nauk SSSR, Moscow. (in Russian) Saidova, Kh. M., 1981: O sovremennon sostoyanii sistemy nadvi- dovykh taksonov Kaynozoyskikh bentosnykh foraminifer (On an up-to-date system of supraspecific taxonomy of Cenozoic benthonic foraminifera). 73 p. Institut Okeanologi in P. P. Shirshova, Akademiya Nauk SSSR, Moscow. (in Russian) Shuto, T., 1952: Stratigraphic study of the Miyazaki Group. Memoirs Faculty of Science, Kyushu University, Series D, Geology, vol. 4, no. 1, p. 1-40. Suzuki, H., 1987: Stratigraphy of the Miyazaki Group in the south- eastern part of Miyazaki Prefecture, Kyushu, Japan. Contributions from the Institute of Geology and Paleontology, Tohoku University, no. 90, p. 1-24. (in Japanese with English abstract) Ujiié, H., Saito, T., Kent, D. vol., Thompson, P. R., Okada, H., Klein, G. D., Koizumi, I., Harper, H. E., Jr. and Sato, T., 1977: Biostratigraphy, Paleomagnetism, and Sedimentology of Late Cenozoic sediments in northwestern Hokkaido, Japan. Bulletin of the National Science Museum, Series C (Geology and Paleontology), vol. 3, no. 2, p. 49-102. Whittaker, J. E. and Hodgkinson, R. L., 1979: Foraminifera of the Togopi Formation, eastern Sabah, Malaysia. Bulletin of the British Museum (Natural History), London, (Geology), vol. 31, p. 1-120. 237 The Palaeontological Society of Japan has revitalized its journal. Now entitled Paleontological Research, and published in English, its scope and aims have entirely been redefined. 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The authors receive 50 free of charge offprints without covers. Additional copies and covers can be purchased and should be ordered when the proofs are returned. Charges. If a paper exceeds 24 printed pages, payment of page charges for the extra pages is a prerequisite for acceptance. Illustrations in color can also be published at the authors’ expense. For either case, the editors will provide infomation about current page charges. Return of published figures. The manuscripts of the papers published will not be returned to the authors. However, figures will be returned upon re- quest by the authors after the paper has been published. Ager, D. V., 1963: Principles of Paleoecology, 371p. McGraw-Hill Co., New York. Barron, J. A., 1983: Latest Oligocene through early Middle Miocene diatom biostratigraphy of the eastern tropical Pacific. Marine Micropaleontology, vol. 7, p. 487-515. Barron, J. A., 1989: Lower Miocene to Quaternary diatom biostrati- graphy of Leg 57, off northeastern Japan, Deep Sea Drilling Project. In, Scientific Party, Initial Reports of the Deep Sea Drilling Project, vols. 56 and 57, p. 641-685. U. S. Govt. Printing Office, Washington, D. C. Burckle, L. H., 1978: Marine diatoms. In, Haq, B. U. and Boersma, A. eds., Introduction to Marine Micropaleontology, p. 245-266. Elsevier, New York. Fenner, J. and Mikkelsen, N., 1990: Eocene-Oligocene diatoms in the westem Indian Ocean: Taxonomy, stratigraphy, and paleoecology. In, Duncan, R. A., Backman, J., Peterson, L. C., et al., eds.Proceedings of the Ocean Drilling Program, Scientific Results, vol. 115, p. 433-463. College Station, TX (Ocean Drilling Program). Kuramoto, S., 1996: Geophysical investigation for methane hydrates and the significance of BSR. Journal of the Geological Society of Japan, vol. 11, p. 951-958. (in Japanese with English abstract) Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey (A new find of an ammonoid jaw apparatus). Paleontologicheskii Zhurnal 1974, p. 127-129. (in Russian) nn FT ETF GP nn SS Sn 222222222 22 OF 1521 FIZi2, 200378 1 H24H (4)~26H (A) CERUXKÉHE AFP THIEO PET 3. 1 H24H (SB) YY RYDAELUT (ARE Fo A ABS IEE PG ld, ErIÄBSH (+4) ev vRYIA [he BERUF ROHR EHE — 7 L'— UHR MRO: HA TAR) SBkanzy. As BMHORLAAK HYD ld, 20027811 A 29H (2) TE. MBALUSOSRERBAN ORI LER CHAT ARS Gi OY x 97 7 —, OHP, 257% FRE) OBBleDW THZHLT FAN. O2003F FAKES It, 200386 A FAITH APRS ER CHER NED. YU RYO [ESS A EDP oBzA : HA tek Ae INRA ERE) CEP ECT. BHO LA A ff U] )(42003F 5 H 2H (4) OFETI. COlD, RiVDRAKCORSPERHSVELK 45, 2002 12A MWS TIITERE CHASE FEU, (Asi? VY RY ODLROMRLAAHE (AA BBO LIAS PRRs Fade TERBEH FAW. E-mail ? 7 7 » 7ATOMRLASA Id HEN ELTHUHUCHV ERA. ETS 2 BETT SHE HTERMTERH EHE CHB < es. T305-8571 OS (StH KEG 1-1-1 THRASHERS HEDFEATSHA) PEER PUR Tel: 0298-53-4302 (iii) Fax: 0298-51-9764 E-mail: ogasawar@arsia.geo.tsukuba.ac.jp A D HTERFE) T305-8571 2 dh KEG 1-1-1 RK FHKE SH Tel: 0298-53-4212 (f=) or 53-4465 (KR) Fax: 0298-51-9764 E-mail: isaomoto @ sakura.cc.tsukuba.ac.jp Ir III EI LD LDL DOD LD LD EPL PLD LD EDL OLDE DLP LD LOL DL DLO LDL DLO LOAD 2) TEILTE ET ET ET ET BOT ETC BOT BT GT BOT ET BT BT BOT BET BET BT BT BET BET GT ET BT BT GT BET BT BT BT BT RT RT ET 2 2 2 „= ee IE III EI III EEE EL GLEN EL LL EL EN EU EL PL EN AEOFTIRIZEHNK, ZADSEHEUNI, ÉD OLRÉDITENTUET. HÉHOËE SEX FiOË0 tT. HRNETERDE HREME INNTZHBAEEME MR Gath PA PR A 2 Amer 1 & M À À St HÉRVACLERO NME La I TAN -IRHEBREME (7 1 9 x # IA) % 7 À FA A FH EF WH F B 2002476H25H EM Bil 7113-8622 Kon AHpAS-16-9 2002F6H28H # ff HASAB Re y 7 — M BE 03-5814-5801 fn 2 GE WM — kh MEERE Ai SE EP aR EK ee AY EN HM AATF RRR aH #2 2,500) 7176-012 Wye KS EI201301 Ey 08 "3 99) 1. = 375) A ISSN 1342-8144 Paleontological Research 6% #25 AB = FE or i ii 0 ISSN 1342-8144 Paleontological Research Vol. 6, No. 2 June 28, 2002 CONTENTS 4 “aa a À Takashi Matsubara: Molluscan fauna of the “Miocene” Maéjima Formation in Maéjima Island, à Okayama Pretéètie SERRE epan 4: Ni SNS i k 1 Satoshi Hanagata: Eocene shallow marine foraminifera from subsurface sections in the Yufutsu- 4 Umaoi district, Hokkaido, Japan -- +++ terete tener nennen nennen 147 À Toshiyuki Kimura: Feeding strategy of an Early Miocene cetothere from the Toyama and Akeyo | 1 Formats, dental Japan i A a | Subhash Chandar Khosla and Madan Lal Nagori: Ostracodes from the Inter-trappean beds (Early À | Paleocene) of the east coast of India -:------::-::-.......................................... 191 4 Hisayoshi Kato: Fossil crabs (Crustacea: Decapoda: Brachyura) from the latest Miocene Senhata = Formation, Boso Peninsula, Japan PO lo DO DO DOI DEAN ateetiomenfattents 0 Didto 00.0 000,0 0 0 0 0 0 0 0 0 211 4 | Shungo Kawagata and Akio Hatta: Internal test morphology of the genus Aecfobolivina (Cushman, 1 1927) from the Late Cenozoic Miyazaki Group, southwestern Japan ::-:::-:::-:::--:::--+.... 219 ' = | : Sand an | | .leontological © = Cine Research hwnd Vol. 6 No. 3 September 2002 nn u - The Palaeontological Society of@apan Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Alan G. Beu (Institute .of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato (Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto University, Kyoto, Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain), Roger D. K. Thomas (Franklin and Marshall College, Lancaster, USA), Katsumi Ueno (Fukuoka University, Fukuoka, Japan), Wang Hongzhen (China University of Geosciences, Beijing, China), Yang Seong Young (Kyungpook National University, Taegu, Korea) Officers for 2001-2002 Honorary President: Tatsuro Matsumoto President: Hiromichi Hirano Councillors: Shuko Adachi, Kazutaka Amano, Yoshio Ando, Masatoshi Goto, Hiromichi Hirano, Yasuo Kondo, Noriyuki Ikeya, Tomoki Kase, Hiroshi Kitazato, Itaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Kei Mori, Hirotsugu Nishi, Hiroshi Noda, Kenshiro Ogasawara, Tatsuo Oji, Hisatake Okada, Tomowo Ozawa, Takeshi Setoguchi, Kazushige Tanabe, Yukimitsu Tomida, Kazuhiko Uemura, Akira Yao Members of Standing Committee: Makoto Manabe (General Affairs), Tatsuo Oji (Liaison Officer), Shuko Adachi (Finance), Kazushige Tanabe (Editor in Chief, PR), Tomoki Kase (Co-Editor, PR), Kenshiro Ogasawara (Planning), Yoshio Ando (Membership), Hiroshi Kitazato (Foreign Affairs), Haruyoshi Maeda (Publicity Officer), Ryuichi Majima (Editor, “Fossils”), Yukimitsu Tomida (Editor in Chief, Special Papers), Tamiko Ohana (Representative, Friends of Fossils), Secretaries: Fumihisa Kawabe, Naoki Kohno, Shin’ichi Sato, Masanori Shimamoto (General Affairs), Isao Motoyama (Planning), Hajime Naruse (Publicity officer) Kazuyoshi Endo, Yasunari Shigeta, Takenori Sasaki (Editors of PR), Hajime Taru (Editor of “Fossils”), Yoshihiro Tanimura (Editor of Special Papers) Auditor: Yukio Yanagisawa Notice about photocopying: In order to photocopy any work from this publication, you or your organization must obtain permission from the following organization which has been delegated for copyright for clearance by the copyright owner of this publication. Except in the USA, Japan Academic Association for Copyright Clearance (JAACC), Nogizaka Bild., 6-41 Akasaka 9-chome, Minato-ku, Tokyo 107-0052, Japan. Phone: 81-3-3475-5618, Fax: 81-3-3475-5619, E-mail: kammori@msh.biglobe.ne.jp In the USA, Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. Phone: (978)750— 8400, Fax: (978)750-4744, www.copyright.com Cover: Typical Pleistocene fossils from the Japanese Islands. Front cover: Sinomegaceros yabei (Shikama). Back cover: Paliurus nipponicum Miki, Mizuhopecten tokyoensis (Tokunaga), Neodenticula seminae (Simonsen and Kanaya) Akiba and Yanagisawa and Emiliania huxleyi (Lohmann) Hay and Mohler. All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16-9, Bunkyo-ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp/palaeont/ Paleontological Research, vol. 6, no. 3, pp. 239-258, September 30, 2002 © by the Palaeontological Society of Japan Enamel microstructure of some fossil and extant murid rodents of India RAJEEV PATNAIK Centre of Advanced Study in Geology Panjab University, Chandigarh-160014, India (e-mail: rajeevpatnaik @ mailcity.com) Received July 7, 2000; Revised manuscript accepted April 9, 2002 Abstract. Spatial arrangement of various enamel types (schmelzmuster) present in the incisors and molars of some fossil and extant murid rodents of India was studied from both the functional and phylogenetic points of view. Hunter-schreger bands (HSBs) along with radial enamel (RE) in mice molars have been found to oc- cupy the entire height of the enamel crown (from the base to the top) on the anterior and the posterior por- tions. These HSBs tend to be horizontal around the base and inclined apically around the top. A clear distinction between the leading and the trailing edges of chewing surfaces based on the difference in the ori- entation of prisms has been observed in hypsodont murid molars. On the leading edges, the long axes of prisms originating from the enamel-dentine junction tend to be oriented towards the load, whereas those on the trailing edges turn away from the load. The schmelzmuster in molars of Mus, indicate an omnivorous diet, whereas that in Golunda, Millardia, and Bandicota points to adaptation for an abrasive diet. The Indian bandicoot rat (Bandicota) with its large, hypsodont molars has developed horizontally oriented (relative to the occlusal surface) HSBs at the base of the enamel crown. These HSBs have been found in enamel layers ori- ented both almost parallel and perpendicular to the occlusal surface, an observation that corroborates the presence of horizontal tension at the base of the tooth due to vertical load on the occlusal surface. In the light of the observations made here, a model depicting changes in schmelzmuster in murid rodents through Late Miocene and Plio-Pleistocene times is suggested. Key words: enamel microstructure, functional morphology, India, Muridae, phylogeny, rodent Introduction The enamel microstructure can be studied at various hierarchical levels (Koenigswald and Clemens, 1992; Carlson, 1990). Dental enamel in all mammals is made up of hydroxyapatite ‘crystallites’. These fiber-like crystal- lites are arranged almost parallel to each other to form bun- dles called ‘prisms’ and these in turn are surrounded by an ‘interprismatic matrix’ (IPM) which is also made up of crystallites (Wahlert and Koenigswald, 1985). The crys- tallites of IPM may or may not run parallel to the prism they surround (Martin, 1990). Because of the difference in the orientation of prism and interprismatic crystallites, dis- tinct prism boundaries called as ‘prism sheathes’ are formed. The path of a prism can be traced from the enamel-dentine junction (EDJ), through the entire thickness of the enamel, terminating at the outer surface. ‘Enamel types’ are defined by the spatial arrangement of groups of prisms. The part of the enamel in which prisms run paral- lel to each other is termed ‘radial enamel’ (RE) (Koenigswald, 1977). In many mammals, prisms are arranged in layers or zones, and when prisms of alternate layers run in different directions, a decussating structure is produced called ‘Hunter-Schreger bands’ (HSBs) (Korven- kontio, 1934). Complexly interwoven bundles of prisms that are not arranged in discrete layers are called ‘irregular enamel’ (Koenigswald and Clemens, 1992; Koenigswald, 1997) and prisms with a strong lateral deviation relative to the enamel surface are termed ‘tangential enamel’ (Koenigswald, 1977). The three-dimensional arrangement of different enamel types within a tooth define its ‘schmelzmuster’ (Koenigswald, 1980) and the variation of schmelzmuster from tooth to tooth defines the ‘dentition’ level of the enamel microstructure hierarchy. The enamel microstructure of rodent incisors is quite different from that of their molars due to their special functional requirements (Koenigswald er al., 1987, 1994). Rodent incisors are ever-growing, and their main function is to cut and dig. In the majority of rodents, incisor enamel, which covers only the labial portion, is made up of outer radial enamel and inner HSBs oriented transversely to the long axis. Usually HSBs occupy at least 50% of the 240 Rajeev Patnaik enamel thickness of rodent incisors, but in murid and many caviomorph rodents HSBs can occupy up to 80% (Martin, 1992). The thickness of individual bands of prisms also differs among taxa. A uniserial HSB is 1-2 prism thick, pauciserial 2-4 prisms thick, and multiserial more than 4 prisms thick (Korvenkontio, 1934; Martin, 1993). Murid rodents have only uniserial HSBs. The main objectives of the present work are 1) to docu- ment the complexity of the enamel microstructure in some of the Plio-Pleistocene murids and their extant counterparts collected from India, and 2) to trace the functional adapta- tion back in time based on comparison of fossil and Recent forms. There are certain morphological characters (such as hypsodonty, relative width of molars and orientation of transverse crests) in murid molars which can be correlated with a grazing diet (Crabb, 1976; Meulen and Musser, 1999). This grazing property of mammalian molars is also reflected at the enamel microstructure level (Rensberger, 1973 1975; Pfretzchner, 1994; Janis, 1988; Fortelius, 1985; Weijs, 1994). Therefore, an attempt has been made here to discover the dietary adaptations (grazing or browsing) of extinct murids from their schmelzmuster, a determination which has important implications for palaeoclimatic recon- struction. Material and methods Specimens examined include fossil and Recent murid ro- dents housed at the Vertebrate Palaeontology Laboratory, Centre of Advanced Study in Geology, Panjab University, Chandigarh, India; around one hundred Recent mice speci- mens were provided by T. Sharma, BHU, Varanasi, India and Megacricetodon specimens were provided by T. Bolliger, Palaeontological Institute, Zurich. Genus: Mus. Species: M. booduga, M. dunni, M. musculus musculus, M. m. domesticus, M. m. tytelri, M. saxicola. M. flynni, M. linnaeusi and Mus sp. Material: Upper and lower first left molars and incisors of M. m. tytelri (specimen numbers HMD-13, 12, 5, 10, 6, 9, MMt - 1&4); M. m. musculus (MMCI, 2, 3 from Czechoslovakia, Mdwsb 4, 5 WSB strain European, HMV-4, 6 from Varanasi); M. musculus bactrianus (JP-2, 3, 4 house mouse from Jodhpur); M. m. casteneus (NKM-20 from Kathmandu, Nepal; HMNG-2, house mouse from Narpat Ganj, HMMD, from Madras, HMMM -3 from Mysore, HMGW-1, 3, 8, 9, HMGI-1, 3 from Gangtok wild and indoors respectively); M. booduga/ M. dunni (MBV-1, 2, 3 from Varanasi MBY-1, 3, 4 from Mysore, MDV3, 1-Type I, MDMS5, 6-Type II, MDM1, 3-Type III); M. saxicola (upper molar and lower incisor, MS-33); M. flynni (upper and lower incisors and first mo- lars, MFI-1, 2, MFM-1, 2,SM-6, 25, Late Pliocene Siwaliks around 2.5 m.y.); M. linnaeusi (lower jaw, Transverse section AUS) EX KA 74 NH —section parallel CC De, to the occlusal mA al surface Transverse section aac | angle of inclination Longitudinal Section C 2 Figure 1. Schematic diagram showing sections in this study. A. Transverse and longitudinal sections of incisor. B. Longitudinal section and section parallel to occlusal surface of molar. €. Model of incisor enamel microstructure showing prism orientation. Abbreviations: D = dentine; EDJ = enamel dentine junction; HSB = Hunter-Schreger bands; PI = portio interna; OPE = outer portio externa; IPE = inner portio externa. PI with HSBs (portio interna with Hunter-Schreger bands) and angle of inclination of HSBs. VPL/RP-GII, 2 m.y.); Mus sp. (upper and lower incisors (MS-1, 2). Genus: Bandicota. Species: B. sp. cf. B. bengalensis, B. indica, B. sivalensis. Material: B. sp. cf. B. bengalensis in- cisors from Pleistocene Narmada valley deposits. B. sivalensis upper jaw (VPL/RP-SM-78) from Tatrot Formation (Late Pliocene). B. indica (extant form). Genus: Golunda. Species: G. tatroticus, G. kelleri, G. sp., G. ellioti. Material: Upper and lower incisors and sec- ond lower molar (VPL/RP-M2A). Genus: Millardia. Species: M. meltada (extant), cf. Millardia. Material: Incisors and molars of the Recent form and those collected from Late Pliocene Siwalik deposits. Genus: Parapelomys. Species: Parapelomys robertsi. Material: Lower jaw (VPL/RP-SM-58, Late Pliocene Siwalik deposits). A cricetid, Megacricetodon gregarius (15-13 m.y.) from La Grive (France). Fifteen to 20 speci- mens (including molars and incisors) of each extant species mentioned were studied. In the case of fossil taxa, only a few specimens (2 to 5) were used in the present study. Isolated fossil incisors were identified by comparisons Enamel microstructure of murid rodents 241 Al, 088 Figure 2. of upper incisor of Mus musculus tytelri in transverse section. Enamel microstructure in the incisors of some extant Mus. B. Longitudinal section of upper incisor (tip on left-hand side) of Mus musculus tytelri showing only part of radial enamel. D. Transverse section of upper incisor of Mus (Pyromys) saxicola. A. Transverse section of upper incisor of Mus musculus tytelri. C. Outer radial enamel Abbreviations: PL = plex; P = prism; IPM = interprismatic matrix; other abbreviations as same as in Figure 1. with those of their closest extant relatives. For enamel mi- crostructure studies, the molars and incisors were embed- ded in polyester resin. Based on the area of investigation, sections (longitudinal, transverse, tangential and sections parallel to the occlusal surface of the dentition) were made (Figure 1) and studied both under stereoscopic and scan- ning electron microscopes. Some of the molars were sec- tioned parallel to the occlusal surface at particular (approximately 0.25-0.5 mm) intervals of depth (serial sec- tioning method) for mapping of the schmelzmuster (spatial arrangement of various enamel types in the whole tooth). In order to view the same part of the enamel of the same molar position of different Mus species, all the teeth were aligned and oriented inside one slab of polyester resin and sectioned at the same depth. Sections were polished and etched with mild acid, 5% HCl. Mapping of enamel types was carried out initially by using a light microscope and later the polished surfaces were coated with gold in order to study them under the scanning electron microscope (SEM). The scheme proposed by Koenigswald and Clemens (1992) 242 Rajeev Patnaik Figure 3. Enamel microstructure in incisors of some fossil Mus. Siwalik sediments). on left-hand side) of Mus flynni. to study enamel microstructure including various structural complexities and murid dental terminology proposed by Jacobs (1978) has been followed here. Observations Upper incisors of all the Mus species studied, including the fossil specimens in transverse section, contain uniserial HSBs (portio interna or inner enamel) that are apically in- clined and occupy more than 70% of the total thickness of the enamel layer. The typical uniserial HSBs are arranged transversely to the long axis of the incisor. Outer enamel (portio externa) is divided into two parts: an inner part of radial enamel consisting of apically oriented prisms and vertical IPM, and an outer part consisting of dense prisms and IPM (etched prismless external layer or PLEX) (Figure 2A-D). This differentiation of the portio externa is not found on fossil upper and lower incisors, where the portio externa consists only of radial enamel (Figure 3A-C). Prisms have a lensoid shape in cross section. Crystallites of interprismatic matrix (IPM) run perpendicular to those of prisms, providing a strong interlocking system (Figure 2B). 20K ¥ A. Transverse section of upper incisor of Mus flynni (from Late Pliocene B. Longitudinal section of upper incisor (tip on right-hand side) of Mus flynni. Abbreviations as same as in Figures 1 and 2. C. Longitudinal section of lower incisor (tip HSBs (portio interna) on lower incisors occupy a greater portion of the enamel and are inclined less steeply than those on the upper incisors. Therefore, in transverse sec- tion more bands are encountered on the lower incisors. On the upper and lower molars of mice, the occlusal sur- face is covered by occlusally oriented prisms of radial enamel (Figure 4A, B). On leading edges of cusps, these prisms converge with their long axis pointing towards the cutting edge (Figures 5, 6D, 7). On trailing edges, radial enamel with interrow sheets emerges from the EDJ with prisms oriented towards the cutting edge. Often in sec- tions parallel to the occlusal surface or on slightly ground lower molars, HSBs emerging from the EDJ are inclined towards the occlusal surface (Figures 4, 6D, E). As we move towards the base of the molar, they tend to become horizontal and parallel to the occlusal surface (Figures 4, 7A, C, D). At the very base, the HSBs occupy almost the total thickness of the enamel running from the EDJ to the outer part (Figure 7C). Prisms of alternate bands decus- sate at a high angle and crystallites of IPM are at right an- gles to those of the prisms (Figure 6E). This layer is followed by radial enamel containing prisms oriented Enamel microstructure of murid rodents 243 First Lower Molar A Figure 4. Schematic diagrams showing sections of first upper and lower molars of Mus musculus. A. Occlusion of first upper and lower molars of Mus musculus showing prism orientation. B. Model showing prism orientation at tip and base of anterior most cusp on first lower molar. trailing Al leading leading Bl trailing Figure 5. and first lower molars. first upper molar and B, occlusal; E, labial; F, lingual views of first lower molar of Mus musculus with approximate distribution of HSBs. Blowups of A (Al) and B (Bl) showing differentiation of leading and Schematic diagrams of Mus musculus first upper A, occlusal; C, labial; D, lingual views of trailing edge. Arrows indicating load direction. Abbreviation same as in Figures 1 and 2. occlusally. In longitudinal sections of upper and lower molars, the HSBs run from the base to the tip of the ante- rior and posteriormost cusps, a structure similar to that seen on incisors (Figures 6A, 7C, D). These horizontal HSBs are also found on the labial and lingual walls but are con- centrated around the roots. Therefore, HSBs cover the an- terior, posterior and lingual sides of the upper first molars where major roots are found (Figure 5). Enamel on trans- verse cusps apart from the anterior ones (anterostyle, lin- gual and labial anterocones on the upper first molars and labial and lingual anteroconids on the lower first molars) and posterior ones (hypocone and metacone on the upper molars and posterior cingulum on the lower) lack HSBs (Figures 6A, B, F, 7B). Where a prestyle is present on the lingual anterocone, HSBs are developed on it, running per- pendicular to the cusp axis away from the EDJ (Figure 6C). Upper and lower molars of fossil mice (Pliocene, Siwaliks) also show HSBs running from the root to the crown (Figure 8A-G). At the base of the tooth these HSBs are horizontal, but near the cap they incline occlusally. In Megacricetodon gregarius (from the Mid- dle Miocene deposits of Switzerland) the HSBs occupy more than half (from the root-crown junction) of the upper molar crown (Figure 8H). In Bandicota sp. cf. B. bengalensis, the longitudinal sec- tion of the upper incisor shows uniserial HSBs inclined apically at an angle of around 40°. The crystallites of IPM are at right angles to those of the prisms. The prisms of al- ternate bands decussate at an angle less than 90°. At the EDJ, the IPM crystallites run vertically (relative to the EDJ) and then they change course to run perpendicular to the prisms. At the outer enamel, the crystallites of IPM again become almost vertical as the prisms bend apically. The outer radial enamel is around 25% of the total thick- ness (Figure 9A). The HSBs of lower incisors are inclined at around 45° to the long axis of the tooth. Prisms of alter- nating bands decussate very strongly (around 90°). Crystallites of IPM are at a right angle to those of the prisms. The outer radial enamel occupies only 15% of the total thickness. IPM crystallites of the outer enamel run vertically. Prisms of the radial enamel in the lower inci- sors have a higher inclination towards the outer surface than those of the upper incisors (Figure 10). On the molars of extant species of Bandicota, except for the very minor portion of the base, the entire enamel, in- cluding the grinding edges of the occlusal surface, is com- posed of radial enamel. At the base of the anterior portion the enamel curves beneath the molar and becomes almost parallel to the occlusal surface (Figure 11A). In contrast to incisors, where the outer layer consists of radial enamel and the inner layer of HSB, here the outer enamel contains HSBs and the inner enamel is radial which is modified and appears similar to an interrow sheet (layers of IPM between rows of prisms) (Figure 11B, C). A small portion of the enamel at the base on the posterior margin, which is verti- cally oriented (relative to the occlusal surface), is also oc- cupied by HSBs (Figure 11E). In the first lower molar the leading and trailing edge differentiation is quite clear 244 Rajeev Patnaik Tamm 1013 Figure 6. Enamel microstructure in molars of some extant Mus. A. Longitudinal sections of first upper (M') and lower (Mı) molars of Mus musculus tytelri. B. Trailing edge in longitudinal section of first upper molar of Mus musculus tytelri (another specimen). C. Longitudinal section of first upper molar of Mus saxicola showing prestyle and lingual anterocone. D. Longitudinal section of first upper molar of Mus musculus tytelri showing leading edge. E. Section parallel to occlusal surface of first upper molar of Mus musculus tytelri, showing leading edge. F. Section parallel to occlusal surface of first upper molar of Mus musculus tytelri, showing trailing edge. Abbreviations same as in Figures 1 and 2. Enamel microstructure of murid rodents 245 Figure 7. Enamel microstructure in first lower molars of Mus musculus tytelri. A. Longitudinal sections showing anterior part. B. Trailing edge in longitudinal section (magnified portion of A). C. Lower part of leading edge in longitudinal section (magnified portion of A). D. Upper part of leading edge in longitudinal section (magnified portion of A). Abbreviations same as in Figures l and 2. 246 Rajeev Patnaik Figure 8. Enamel microstructure in molars of some fossil muroid rodents. A-G. Mus flynni (from Pliocene Siwalik deposits of India). A. Longitudinal section of first upper molar of Mus flynni. B. Anterior part of first upper molar in longitudinal section (magnified portion of A, in- dicated by Bon A). C. Posterior part of first upper molar in longitudinal section ( magnified portion of A, indicated by C on A). D. Tip of posterior part of first upper molar in longitudinal section (magnified portion of C). E. Anterior part of first lower molar in longitudinal section. F. Tip of leading edge in longitudinal section (magnified portion of E). G. Tip of trailing edge in longitudinal section (magnified portion of E). H. Megacricetodon gregarious (from Miocene deposits at La Grive, France). Oblique section (parallel to probable jaw movement direction) of first upper molar of Megacricetodon gregarius. Abbreviations same as in Figures 1 and 2. Enamel microstructure of murid rodents 247 Figure 9. Enamel microstructure in upper incisor of Bandicota sp. cf. B. bengalensis (Upper Pleistocene, Narmada Valley). section of upper incisor (tip on left-hand side). Figures 1 and 2. (Figure 11F, G). Here the prisms in the leading edge originating from the EDJ initially bend forward (their c- axis) occlusally and later turn in the same direction as the load (Figure 11F). Those in the trailing edge run away from the load occlusally (towards the worn surface, Figure 11G). All the species of Bandicota studied here show similar patterns. Upper incisors of Golunda kelleri and G. tatroticus (fos- B and C. Close-up of lower and upper parts of longitudinal section. A. Longitudinal Abbreviations same as in sils) have thick outer enamel (radial enamel) occupying around 30% of the total thickness of enamel (Figure 12A, B). The transversely arranged HSBs are inclined apically by 25°. Prisms of alternate bands decussate at right an- gles, and the crystallites of IPM are at right angles to the prisms in the third dimension (Figure 12E). HSBs on lower incisors have an inclination of around 35° (Figure 12F). 248 Rajeev Patnaik Figure 10. Enamel microstructure in incisors of Bandicota sp. cf. B. bengalensis (Upper Pleistocene Narmada Valley). A. Transverse section of upper incisor. of A and B, respectively. Abbreviations same as in Figures 1 and 2. Serial sectioning parallel to the occlusal surface on a G. tatroticus lower second molar reveals the differentiation of the schmelzmuster at different levels. Slight grinding and etching led to the exposure of the metaconid, which shows presence of radial enamel with interrow sheets at the EDJ with prisms oriented towards the cutting edge. The outer B. Longitudinal section of lower incisor (tip on right-hand side). C and D. Upper and lower parts of longitudinal section, close-up radial enamel has prisms running occlusally at a higher angle (Figure 13A-D). Further grinding reveals the pres- ence of HSBs (Figure 14A-D) with the leading edge hav- ing radial enamel on the push (compression) side and HSB on the pull (extension) side (Figure 14A). But the trailing edge of the metaconid still retains the same pattern of radial Enamel microstructure of murid rodents 249 Figure 11. Enamel microstructure in molars of Bandicota bengalensis as seen in longitudinal section. A. Longitudinal section of first upper molar. B. HSBs as seen at base of first upper molar (magnified portion of A, indicated by B on A). C. HSBs at base of first upper molar, further magnified from a portion on B (indicated by C on B). D. Enamel fold as seen on first upper molar (magnified portion of A). E. HSBs as seen at posterior end of base of first upper molar (magnified portion of A, indicated by Eon A). F. Longitudinal section of leading edge of first lower molar. G. Longitudinal section of trailing edge of first lower molar. Arrow indicates load direction. Abbreviations same as in Figures 1 and 2. 250 Rajeev Patnaik Figure 12. Enamel microstructure in incisors of Golunda kelleri and G. tatroticus. A. Transverse section of upper incisor of Golunda kelleri (Late Pliocene Siwaliks). B. Longitudinal section of upper incisor (tip on left-hand side) of Golunda kelleri. C. Transverse section of upper incisor of Golunda tatroticus (Late Pliocene Siwaliks). D. Longitudinal section of upper incisor (tip on left-hand side) of Golunda tatroticus. E. HSBs in longitudinal section (magnified portion of HSBs as seen on D). F. Longitudinal section of lower incisor (tip on right-hand side) of Golunda tatroticus. Abbreviations same as in Figures land 2. Enamel microstructure of murid rodents 251 Figure 13. tion of A). C. Outer part of enamel (magnified portion of A). in Figures 1 and 2. enamel as seen before (Figure 14E, F). At the base of the crown and around the roots, more of the area of the enamel is occupied by horizontal HSBs (Figure 15A-D). The rest of the upper and lower molars show a very similar pattern. The lower incisor of the extinct Parapelomys robertsi shows less inclined HSBs (several bands can be seen) in transverse section (Figure 16E). A very thin outer radial enamel with IPM running vertically (Figure 16F) to the Enamel microstructure in second lower molar of Golunda tatroticus, in sections parallel to occlusal surface. microstrcuture in metaconid (as seen after removal of ~.5 mm of enamel and dentine from occlusal surface). A. Enamel B. Inner part of enamel (magnified por- D. Radial enamel further magnified from a portion of B. Abbreviations same as enamel surface from the EDJ has been observed. As com- pared to Golunda, to which it is closely related (Patnaik, 1997), it has less inclined HSBs. In cf. Millardia (from Late Pliocene Siwalik sediments) upper incisors have HSBs apically inclined (50°). A lower incisor of the fossil form (Figure 16D) has thicker outer ra- dial enamel than its extant counterpart, M. meltada (Figure 16C). Molars of Milladia (both fossil and extant) show a 252 Rajeev Patnaik Figure 14. Enamel microstructure in second lower molar of Golunda tatroticus, sections parallel to occlusal surface. A. Magnified part of leading edge (indicated by A on C). B. Magnified part of labial side (indicated by B on C). C. Second lower molar. D. Magnified part of leading edge (indicated by D on E). E. Second lower molar, further polished. F. Magnified part of trailing edge (indicated by F on E). Abbreviations same as in Figures 1 and 2. Enamel microstructure of murid rodents 253 uz Figure 15. Enamel microstructure in second lower molar of Golunda tatroticus, sections parallel to occlusal surface. A. A part of HSBs as seen at base of second lower molar (magnified portion of B, indicated by A on B). B, Second lower molar polished up to base. C and D. HSBs at base of molar (magnified portions of B, indicated by C and D on B). Abbreviations same as in Figures 1 and 2. 254 Rajeev Patnaik Figure 16. Enamel microstructure in incisors of Millardia and Parapelomys. A. Transverse section of upper incisor of cf. Millardia. B. Longitudinal section of upper incisor (tip on right-hand side) of cf. Millardia. C. Longitudinal section of lower incisor (tip on left-hand side) of Millardia meltada. D. Longitudinal section of lower incisor (tip on right-hand side) of cf. Millardia. E. Transverse section of lower incisor of Parapelomys robertsi. F. HSBs, further magnified from E. Abbreviation same as in Figures | and 2. very similar structure to that of Golunda, i.e., the lower half incisors studied here seems to be an etching artifact that of the crown contains inner HSBs and outer radial enamel, could have been produced due to a slight compositional dif- and the rest of the crown is occupied by radial enamel. ference between inner and outer radial enamel. Presence of dense outer radial enamel underlain by inner radial Discussion enamel and HSBs (which are less resistant to abrasive forces) may facilitate the maintenance of a sharp incisor. The outer prismless enamel found in all the extant Mus This is the first report of brachydont rodent molars show- Enamel microstructure of murid rodents 255 ing HSBs running from the base to the occlusal surface, al- though on the lingual and labial walls, HSBs occupy only a part of the crown height from the base. Prior to this study only hypsodont and rootless rodent molars have been found to show HSB extending from the base to the top of the crown (Koenigswald, 1980; Koenigswald er al., 1994), although the presence of lamellar enamel with uniserial HSBs covering the base of brachydont molars, such as that of Cricetus cricetus, has been noted earlier (Koenigswald and Clemens, 1992; Koenigswald, 1993). Models of stress distribution and prism orientation suggest that horizontal HSBs surround the low-crowned molars in order to provide reinforcement against vertical load and crack propagation (Koenigswald er al., 1987; Pfretzschner, 1988; Pfretz- schner, 1994). According to this model, vertical loads on the occlusal surfaces of the upper and lower teeth of mice (Figure 17A) produce horizontal tension in the enamel, which would be at a maximum at the base around the roots. These tensile stresses may lead to expansion of vertical cracks around the walls of the molars. As radial enamel with prisms oriented in one direction is vulnerable to these crack-generating forces, reinforcement of the structure with horizontal HSBs surrounding the base of the molars would inhibit such a development (al in Figure 17). It is possible that the HSBs are developed at the base of the crown to re- inforce the thin enamel. But if we look at the HSBs in Mus (Figure 7), where they occupy the entire enamel crown of varying thickness, this conjecture does not hold strongly. Another example supporting this view is that of Megacricetodon, which has molar enamel comparable in thickness to that of mice, but in which the HSBs occupy only half of the crown height (Figure 8H). In mice, the effective jaw movement is ‘proal’ (forward stroke). Except for the posterior portion of the hypocone, all the cusps of the first upper molar point their arcuate and concave end posteriorly. In contrast, except for the ante- rior portions of the lingual and labial anteroconids on the first lower molar, all the cusps of lower molars point anteriorly. During occlusion, the valleys between lingual and medial cusps and those between the medial and labial cusps of the first upper molars are occupied by the lingual and labial rows of cusps of the first lower molars, respec- tively. The row containing the hypoconid and the entoconid occupies the space between the second and last row of the first upper molar. During a proal jaw move- ment with the lower jaw moving forward, sharp cutting edges are formed at the anterior margin by lingual and la- bial anteroconids. The cutting edge formed in this manner on the molars shows a resemblance to the cutting edge of an incisor, where one can see prisms with their long axis pointing towards the occlusal surface in the outer radial enamel and HSBs inclined apically in the inner part of the enamel. Such cutting edges are also formed at the poste- a vertical load à mon load ID EN QQ inferred crack tensile stress v ertical. plane of cracks = N 1 orientation ‘a N Nur ER UN SEES N 1 plane of vertical cracks B Figure 17. Hypothetical schematic diagram, showing arrange- ment of HSBs in response to vertical load in molars of mice. A. Sketches of skull and lower jaw of mice; a, first lower molar en- larged; al, schematic model of portion of enamel at base of crown. B. Generalised model showing orientation of HSBs, plane of decussation and plane of vertical cracks in response to vertical load on low-crowned molar (adapted from Pfretzschner, 1988). rior end of the first upper and lower molars. The cusps and valleys that contain outer radial enamel and inner radial enamel with very thick interrow sheets are resistant to abra- sion and may help to grind efficiently when in contact. Differentiation of the leading and trailing edges of enamel microstructure previously has been observed only in hypsodont rodent molars (both with and without roots). In rodents, hypsodonty has led to lamination of the cusp rows, which has simplified the morphology. In hypsodont rodents the radial enamel has invariably been found on the push sides of the cutting edges (Koenigswald, 1980; Koenigswald er al., 1994). This study shows that the brachydont cuspidate dentition in mice also exhibits such differentiation between leading- and trailing -edge enamel. It is even more conspicuous in heavily worn dentitions where cusps are lost and only enamel folds remain. The presence of radial enamel on the push sides of the leading and trailing edges in mice molars justifies their (radial enamel) abrasion-resisting properties. The cutting and grinding ability of mice molars reflects a rather omnivorous diet, which may include browsing shrubs, eating insects and grazing grasses (Dieterlen, 1972). In hypsodont Bandicota, horizontal HSBs probably serve as a crack-stopping mechanism. These horizontal HSBs have been noticed in both vertically and parallelly oriented enamel relative to the occlusal surface. This may indicate that regardless of the orientation of the enamel, horizontal HSBs are present to counter vertical forces. Also noted is 256 Rajeev Patnaik all other hypsodont muroids PLIO-PLEISTOCENE 2) LATE MIOCENE Figure 18. m [A] 8] €] py e| Low crowned Relationship of molar morphology and scmelzmuster in some muroid rodents. Arvicolidae only Rootless Aes] FO Hypsodont Low crowned A. Ontogenetic phases of morphology and schmelzmuster of low-crowned muroid molars. B. Difference in heterochrony of morphology (m) and schmelzmuster (s) during evolution from low- crowned (1) to hypsodont (2 and 3) and rootless (4 and 5) molars of muroid rodents. A and B adapted from Koenigswald (1993). €. 1) Low- crowned Late Miocene murids with dominant Y phase (pattern similar to that of Mus); 2) Plio-Pleistocene murids such as Golunda and Millardia with both X and Y phases equally developed; 3) Plio-Pleistocene murids such as Bandicota with Y phase reduced and X phase considerably prolonged; 4) Plio-Pleistocene murids such as Mus, with dominant Y phase. Explanation of various phases in molar morphology and schmelzmuster: A and B, formation of occlusal surface; C, formation of side walls; D, formation of base of crown; E, formation of roots; X, upper part with radial enamel; Y, circumferential band of lamellar enamel at crown base. that the development of HSBs takes place from the radial enamel (Koenigswald et al., 1987). Presence of radial enamel (with prisms in leading edges pointing their long axes towards the load) on the occlusal surface would help in resisting abrasion. This feature suggests an adaptation for an abrasive diet. In brachydont Golunda molars, radial enamel is domi- nant on the occlusal surface. Only after considerable abra- sion can one observe differentiation of leading and trailing edges. Radial enamel is found on the push side and HSBs on the pull side of the leading edge. Radial enamel with interrow sheets has been noticed on the push side and radial enamel on the pull side of the trailing edge. Again pres- ence of horizontal HSBs at the base probably strengthens the tooth against progress of vertical cracks. The predomi- nant radial enamel on the occlusal surface points towards a grazing habit. Koenigswald (1993) studied the evolution of schmelz- muster in molars of low-crowned and hypsodont rodents (both with and without roots) from the perspective of heterochrony. He argued that low-crowned molars of muroid rodents with a large portion of their crown occupied by radial and a smaller portion by lamellar (uniserial HSB) enamel evolved into hypsodont molars either lacking lamellar enamel altogether (e.g., Microtia magna) and/or retaining this small amount of lamellar enamel on the other (e.g., Nesokia indica). He observed that in rootless hypsodont molars the radial enamel extends from the base to the top in some species (e.g., gerbil, Rhombomys opimus) and that lamellar plus radial enamel extends from the base to the top in others (e.g., arvicolids). Further, he suggested that, in most muroid rodents (except for arvicolids), morphology and schmelzmuster follow the same heterochronic modifications. The base of a low- crowned cricetid molar has lamellar (uniserial HSBs) and radial enamel occupying the inner and outer enamel, re- spectively (Figures 18A, the “Y’ phase, corresponding to D phase of morphology). The rest of the crown of a cricetid Enamel microstructure of murid rodents 257 molar is occupied by radial enamel ( Figure 18 A, the ‘X’ phase, corresponding to A, B and C phases of morphology). According to Koenigswald (1993), the structure seen on low-crowned cricetids gave rise to those observed on hypsodont and rootless muroid rodents; 1) with the entire crown occupied by the ‘X’ phase and 2) with the entire crown occupied by ‘Y’ phase (arvicolids). In arvicolids, acquisition of the ‘X’ phase is accelerated and gives way to the “Y” phase (Figure 18B). In the context of the present observations, the heterochrony hypothesis of Koenigswald (1993) is not strongly supported for murids, although it could still be ap- plicable to other muroids, for example, cricetids and arvicolids. In the Indian murids, the ‘Y’ phase in brachydont mice occupies the whole crown (Figure 18C, 1). Taking into account the temporal and spatial dis- tribution of this structure it is suggested here that this should be regarded as the basic structure for the family Muridae. It extends up to the Recent with the Progonomys-Mus lineage. Mus originated from Progono- mys in the Late Miocene (around 5.7 m.y. ago, Jacobs and Downs, 1994). In fact, Progonomys, which had a wide distribution during the Miocene (Indo-Pakistan, China, Africa, Europe), is the basic stock that gave rise to all the fossil and extant murids, which includes more than 500 ex- tant species and 120 genera. In contrast to the Mus pattern, where the “Y” phase dominates, brachydont Golunda and Millardia, which are phylogenetically related to the Karnimata group (Patnaik, 1997, 2001) of Late Miocene time, have the “Y’ phase restricted to the lower half of the crown and the ‘X’ phase occupying the rest of the crown (Figure 18C, 4). This structure also extends to the Recent. A different pattern is seen in hypsodont murids. Hypsodonty in murids is first noted in Dilatomys of the Pliocene Siwaliks and Late Miocene deposits of Afghanistan (see Sen, 1983; Patnaik ,1997), which appears after the emergence of C4 grasslands in the subcontinent (Cerling et al., 1993). In spite of being hypsodont, cusp patterns of Dilatomys are similar to those seen on Parapelomys-Saidomys (again related to Karnimata) and it has been placed in one group with Bandicota and Hadromys (Patnaik, 1997). Here, the phase ‘X’ extends to cover the occlusal surface, and the phase ‘Y’ is reduced considerably to occupy only a small portion of the base around the roots (Figure 18C, 3). In this study the genera Mus, Golunda, Millardia, and Bandicota can be distinguished broadly by variation in schmelzmuster (angle of inclination of HSBs, percentage of HSBs and RE in incisors; extent of distribution of HSBs and prism orientation in molars, etc.). In the genus Mus, it was found that closely related species (here belonging to the subgenus Mus) do not show any considerable difference at the microstructural level. However, Mus (Pyromys) saxicola differs from all the other Mus species at the schmelzmuster level, as it shows a slight difference in the shape of the first upper molars (Figure 6C). Nevertheless, it appears that, given similar shape and size of dentition and dietary habits, it is difficult to distinguish closely related species of Mus based on enamel microstructure alone. Conclusions 1. The molars of Mus show some sort of specialisation at the microstructure level by having a kind of ‘incisor- like’ arrangement of HSBs and radial enamel running from the base to the top of the crown, which could be useful in maintaining sharp cutting edges to break down leaves and insects. In addition to this, the low- crowned Mus molars also show grinding ability. 2. Predominance of radial enamel on the occlusal surface of molars of Golunda, Millardia and Bandicota might be indicative of their adaptation for a grassy diet. 3. The results of this paper are in accordance with the hy- pothesis that the presence of horizontal HSBs counters vertical forces. In Bandicota, the HSBs in the enamel are horizontal in spite of the enamel being almost hori- zontal and parallel to the occlusal surface. Another unique feature of Bandicota molars is that HSBs in the enamel layer orientated almost parallel to the occlusal surface occupy the outer part of the enamel whereas the inner part has tangentially oriented radial enamel. 4. For murid rodents a schmelzmuster similar to that of Mus should be taken as the basic pattern which could have given rise to patterns similar to the low-crowned Golunda/Millardia and hypsodont Bandicota. Acknowledgements I would like to thank Ashok Sahni (Panjab University, India) for introducing me to the world of enamel micro- structure studies, and for his constant encouragement and useful suggestions on the manuscript. I am grateful to W. v. Koenigswald (Institute of Palaeontology, University of Bonn, Germany), who provided the idea to study rodent molars and also helped in carrying out a preliminary study. I extend my thanks to T. Sharma (Banaras Hindu University, India) and T. Bolliger (University of Zurich) for providing some samples used in the present research. I would also like to thank N. Sahni, M. L. Sharma, D. Kranz, G. Olechensky and Navtej Singh for their help in micro- photography. I would like to thank Mary Maas and an anonymous reviewer for improving this manuscript with critical comments and useful suggestions. Financial assistance at various stages by DAAD, Bonn, Department of Science and Technology and Council of Scientific and Industrial Research, New Delhi is thankfully acknowl- 258 edged. References Carlson, S.J., 1990: Vertebrate dental structure. Jn, Carter, J.G. ed., Skeletal Biomineralisation: Patterns, Processes and Evolutio- nary Trends, Volume 1, p. 531-556. Van Nostrand Reinhold, New York. Cerling, T.E., Wang, Y. and Quade, J., 1993: Expansion of C4 eco- system as an indicator of global ecological change in the Late Miocene. Nature, vol. 361, p. 344-345. Crabb, P.L., 1976: Fossil mammals of the lower Pleistocene Moorna Sand, southwest New South Wales, Australia, with an analysis of the Australian pseudomyine murid molars. Ph.D. Thesis, Monash University, Melbourne. Dieterlen, F., 1972: Mouse-like rodents. Jn, Grzimek, H.C.B. ed, Grzimek’s Animal Life Encyclopedia, Volume II, p. 296-388. Van Nostrand Reinhold, New York. Fortelius, M., 1985: Ungulate cheek teeth: developmental, functional, and evolutionary interrelations. Acta Zoologica Fennica, vol. 180, p. 1-76. Jacobs, L.L., 1978: Fossil rodents (Rhizomyidae & Muridae) from Neogene Siwalik deposits, Pakistan. Museum of North Arizona, Bulletin, vol. 52, p. 1-103. Jacobs, L.L. and Downs, W.R., 1994: The evolution of murine ro- dents in Asia in rodents and lagomorph families of Asian ori- gins and diversification. In, Tomida, Y., Li, C. and Setoguchi, T. eds., Proceedings of 29th International Geological Congress, Kyoto, Japan, vol. 8, p. 149-156. Janis, C.M., 1988: An estimation of tooth volume and hypsodonty indices in ungulate mammals, and the correlation of these fac- tors with dietary preferences. Mémoires du Muséum National d Histoire Naturelle, série C, vol. 53, p. 367-387. Koenigswald, W.v., 1977: Mimomys cf. reidi aus der villa- franchischen Spaltenfüllung Schambach bei Treuchtlingen. Mitteilungen der Bayerischen Staatssammlung fiir Paläontolo- gie und historische Geologie, vol. 17, p.197-212. Koenigswald, W.v., 1980: Schmelzmuster und Morphologie in den Molaren der Arvicolidae (Rodentia). Abhandlungen der Senckenbergischen naturforschenden Gesellschaft, vol. 539, p. 1-129. Koenigswald, W.v., 1993: Heterochronies in morphology and Schmelzmuster of hypsodont molars in the Muroidea (Rodentia). Quaternary International, vol. 119, p. 57-61. Koenigswald, W.v., 1997: Brief survey of enamel diversity at the schmelzmuster level in Cenozoic placental mammals. In, Koenigswald, W.v. and Sander, P.M. eds., Tooth Enamel Microstructure, p. 137-161. Balkema, Rotterdam. Koenigswald, W.v., Rensberger, J.M. and Pfretzschner, H.U., 1987: Change in tooth enamel of early Palaeocene mammals allowing increased diet diversity. Nature, vol. 328, p. 150-152. Koenigswald, W.v. and Clemens, W.A., 1992: Levels of complexity in the microstructure of mammalian enamel and their applica- Rajeev Patnaik tion in studies of systematics. Scanning Microscopy, vol. 6, p. 195-218. Koenigswald, W.v., Sander, P.M., Leite, F.L.S., Mors,T. and Santel, W., 1994: Functional symmetries in schmelzmuster and mor- phology of rootless rodent molars. Zoological Journal of the Linnean Society, vol. 110, p. 141-179. Korvenkontio, V.A., 1934: Mikroskopische Untersuchungen an Nagerincisiven unter Hinweis auf die Schmelzstruktur der Backenzähne. Annales Zoologici Societatis Zoologicae- Botanicae Fennicae Vanamo, vol. 2, p. 1-274, pls. 1-47. Martin, T., 1990: Origin of the caviomorphs: evidence from incisor enamel. Journal of Vertebrate Palaeontology, vol. 10, p. 126. Martin, T., 1992: Schmelzstruktur in den Inzisiven alt-und neuweltlicher hystricognather Nagetiere. Palaeovertebrata, Mémoire extraordinaire, p, 1-168. Martin, T., 1993: Early rodent incisor enamel evolution: Phylogenetic implications. Journal of Mammalian Evolution, vol. 1, p. 227-254. Meulen, A.J.van der and Musser, G.G., 1999: New paleontological data from the continental Plio-Pleistocene of Java. In, Reumer, J.W.F. and Vos, J.D. eds., Elephants Have a Snorkel}, p. 361-368. Deinsea-Annual of the Natural History Museum, Rotterdam. Patnaik, R., 1997: New murids and gerbillids (Rodentia, Mammalia) from Pliocene Siwalik sediments of India. Palaeovertebrata, vol. 26, p. 129-165. Patnaik, R., 2001: Late Pliocene micromammals from Tatrot Formation (Upper Siwaliks) exposed near Village Saketi, Himachal Pradesh, India. Palaeontographica, Abteilung A, vol. 216, p. 55-81, pls. 1-2.. Pfretzschner, H.U., 1988: Structural reinforcement and crack propa- gation in enamel. In, Russel, D.E., Santoro, J.P. and Sigogneau-Russel, D. eds., Teeth Revisited. Proceedings of the VIIth International Symposium on Dental Morphology, Muséum d’ Histoire Naturelle, Paris 1986, vol. 53, p. 133-143. Pfretzschner, H.U., 1994: Biomechanik der Schmelzmikrostruktur in den Backenzahnen von Grosssaugern. Palaeontographica, Abteilung A, vol. 234, p.1-88, pls. 1-15. Rensberger, J.M., 1973: An occlusion model for mastication and dental wear in herbivorous mammals. Journal of Paleontology, vol. 47, p. 515-528. Rensberger, J.M., 1975: Function in the cheek tooth evolution of some hypsodont geomyoid rodents. Journal of Paleontology, vol. 49, p. 10-22. Sen, S., 1983: Rongeurs et Lagomorph du gisement Pliocene de Pul- e-Charkhi, bassin de Kabul, Afghanistan. Bulletin du Museum National d’Histoire Naturelle, Paris, serie 5, section C, 1, p. 33-74. Wahlert, J. H. and Koenigswald, W. v., 1985: Specialized enamel in incisors of eomyid rodents. American Museum Novitates, no. 2832, p. 1-12. Weijs, W.A., 1994: Evolutionary approach of masticatory motor patterns in mammals. Advances in Comparative and Environmental Physiology, vol. 18, p. 270-318. Paleontological Research, vol. 6, no. 3, pp. 259-263, September 30, 2002 © by the Palaeontological Society of Japan Paleobiogeographic significance of Trominina hokkaidoensis (Hayasaka and Uozumi) (Gastropoda: Buccinidae) from the basal part of the Tanami Formation (Oligocene) of the Kii Peninsula, southern Japan YUTAKA HONDA Department of Earth Sciences, Faculty of Education, Mie University, Tsu, 514-8507, Japan (e-mail: eoshonda@ edu.mie-u.ac.jp) Received January 10, 2002; Revised manuscript accepted April 30, 2002 Abstract. The basal part of the Tanami Formation, in the southern part of the Kii Peninsula, southwest Honshu, southern Japan, contains elements of the Asagai-Poronai fauna (late Eocene to early Oligocene age) of northern Japan. These include Malletia poronaica (Yokoyama), Portlandia (Portlandella) watasei (Kanehara), and Trominina hokkaidoensis (Hayasaka and Uozumi). The combination of late Eocene to early Oligocene Asagai-Poronai mollusks and previously known Oligocene to early Miocene mollusks from the Tanami Formation implies that the localities discussed here are of Oligocene age. The presence of Trominina, which was widespread in the northern Pacific during Paleogene time, suggests that it migrated from northern Japan and northward to southern Japan, in accordance with the Eocene-Oligocene transition global cooling trend. Key words: migration, mollusks, Paleogene, Trominina Introduction The Kumano Group crops out in the southern part of the Kii Peninsula in southwest Honshu, Japan (Figure 1A), and has been assigned to the lower to middle Miocene, on the basis of mollusks and foraminifers (Hisatomi, 1981). However, Katto et al. (1976) previously studied mollusks of the Kumano Group in the Tanami area of the Kii Peninsula (Figure 1B) and erected the Tanami and Uematsu Formations (Figure 2), which they assigned to the Oligocene and lower Miocene, respectively, on the basis of mollusks. The basal part of the Tanami Formation yields many spe- cies of the Asagai-Poronai fauna that occurs in the upper Eocene to lower Oligocene of Hokkaido and northeast Honshu, northern Japan (Honda, 1994). The Asagai- Poronai mollusks are Portlandia (Portlandella) watasei (Kanehara), Ampullina asagaiensis Makiyama, Beringius hobetsuensis (Matsui), Trominina cf. T. ishikariensis (Hayasaka and Matsui), and Fulgoraria cf. F. (Musashia) antiquior (Takeda) (Katto and Masuda, 1978). I obtained numerous, but rather poorly preserved molluscan fossils from low cliffs exposed on a wave-cut terrace at Tanosaki, in the basal part of the Tanami Formation (Figure 1B). These are identified as Malletia poronaica (Yokoyama), Portlandia watasei, Acila (Acila) kiiensis Masuda and Katto, “Teredo” sp., Turritella sp., and Trominina hokkaidoensis (Hayasaka and Uozumi) (Table 1). Trominina, which is one of the earliest evolved buccinid genera, appeared in the region including Sakhalin and Kamchatka during late Eocene time (Titova, 1994). It has been widely recorded from upper Eocene to lower Miocene strata in the North Pacific: Japan, Sakhalin, Kamchatka, the Koryak Upland, Alaska, and Washington (Titova, 1994). In this paper, I document T. hokkaidoensis from the basal part of the Tanami Formation and discuss the paleobiogeographic significance of Trominina in Japan, as well as the age of the formation based on mollusks. Geological setting The Tanami Formation largely consists of pale grey, fine-grained sandstone, grey siltstone, and alternating beds of sandstone and siltstone, and is approximately 1500 m thick (Katto et al., 1976). Its basal granule conglomerate, some 30 cm thick, is unconformably underlain by black mudstone of the Eocene to Oligocene Shimotsuyu Formation in the upper part of the Muro Group. The Tanami Formation is in fault contact with the overlying 260 Yutaka Honda @ 5 KYUSHU a = PACIFIC 7 et OCEAN 135° 45'E A Le Ü al Ki yt Ni LA mi Vz [2] Alluvium ay =v, — CE] Terracedeposits TANOSAKI\T3 T2 7 ES Tanami Formation @ 1 Bat] ShimotsuyuF. strike & dip SER EN 7 nn — 7 130° 140° 150°E Figure 1. A. Map showing the location of the Kii Peninsula, southwest Honshu, Japan. B. Geologic sketch map of the Tanami area (simplified from Tateishi et al., 1979). T1-T3, fossil localities. Uematsu Formation (Katto et al., 1976), which contains the Kadonosawa fauna (earliest middle Miocene age; Ogasawara, 2001) (Figure 2). The upper part of the Muro Group largely contains the Asagai-Poronai fauna, within the Tanami Formation, which includes characteristic elements of this fauna such as Malletia poronaica, Yoldia (Yoldia) laudabilis Yokoyama, Y. (Tepidoleda) sobrina Takeda, Portlandia watasei, P. (Megayoldia) yotsukurensis Uozumi, Acila (Acila) elongata Nagao and Huzioka, A. (Acila) kusiroensis Nagao and Huzioka, Cyclocardia akagii (Kanehara), C. tokunagai (Yokoyama), Orectospira wadana (Yokoyama), and Turritella tokunagai Yokoyama (Mizuno, 1973). Discussion Trominina has been recorded from the Paleogene strata bearing the Asagai-Poronai fauna in Hokkaido, northern Japan. Matsui (1957) recorded T. japonica (Takeda) from HISATOMI KATTO ETAL. | MOLLUSCAN (1981) (1976) FAUNA MITSUNO FORMATION SHIKIYA FORMATION AKEYO SHIMOSATO EAU KUMANO GROUP ASAGAI- PORONAI MURO GROUP FAUNA Muro and Figure 2. Kumano Groups, in association with the molluscan faunal succession. Stratigraphic classification of the Table 1. Occurrences of fossil mollusks in the Tanami Formation. A, abundant (10 or more individuals); C, common (5 to 9 individuals); F, few (2 to 4 individuals); R, rare (one individual). One individual is defined herein as consisting of more than half of a separated valve or an articu- lated pair of bivalves, and more than half of a gastropod specimen. Locality Species nn — Ti. NT TE) Bivalvia: Malletia poronaica (Yokoyama) R Portlandia (Portlandella) watasei (Kanehara) C C C Acila (Acila) kiiensis Masuda et Katto R Acila sp. R Caryocorbula? sp. R “Teredo” sp. A Gastropoda: Turritella sp. C Trominina hokkaidoensis (Hayasaka et Uozumi) F R the upper Eocene Poronai Formation in the Ishikari coal- field, central Hokkaido. The lower Oligocene Momijiyama Formation in the Ishikari coalfield has yielded several species, including 7. hokkaidoensis, T. onnaica (Yokoyama), T. ishikariensis (Hayasaka and Matsui), T. yubariensis (Hayasaka and Uozumi), and T. umbelliformis (Hayasaka and Uozumi) (Hayasaka and Matsui, 1951; Hayasaka and Uozumi, 1954). In addition, Honda (1989) recorded T. japonica, T. hokkaidoensis, T. ishikariensis, T. umbelliformis, and T. dispar (Takeda) from the lower Oligocene Ombetsu Group Paleobiogeography of Trominina hokkaidoensis 261 Figure 3. Loc. T3, MES 1035. 3a, b. Turritella sp. x1.6, Loc. T2, MES 1036. 4, 5. Trominina hokkaidoensis (Hayasaka and Uozumi). T2, MES 1037. Sa, b; x1.5, Loc. T1, MES 1038. in the Kushiro coalfield, eastern Hokkaido. The southern- most record of Trominina is T. japonica from the upper lower Oligocene Yamaga Formation in the Ashiya Group of Kyushu, southern Japan (Tomita and Ishibashi, 1990). This suggests that Trominina migrated from Hokkaido and further northward to the Kii Peninsula and Kyushu, south- ern Japan, in accordance with the Eocene-Oligocene transi- tion global cooling trend. In contrast to these Paleogene records, T. bicordata (Hatai and Koike, 1957) from the lower Miocene Hota Group in the Boso Peninsula, central Honshu, is the youngest record of Trominina in Japan. Based on these records of Trominina, the presence of 1. Portlandia (Portlandella) watasei (Kanehara). x1.4, Loc. T2, MES” 1034. 2a-c. Acila (Acila) kiiensis Masuda and Katto. x1.4, 4a, b; x1.5, Loc. “Abbreviation for the Department of Earth Sciences, Faculty of Education, Mie University. Trominina in the Tanami Formation suggests that the basal part of the Tanami Formation, which also contains the Asagai-Poronai fauna, is of Oligocene rather than Miocene age. Honda ef al. (1998) recorded the Akeyo fauna (Itoigawa, 1987; early Miocene, ca. 18 to 16 Ma; Figure 2) from the Shimosato Formation of the Ukui area in the southeastern Kii Peninsula. The basal part of the Tanami Formation contains an older fauna than does the partly coe- val Shimosato Formation. The Tanami Formation as a whole is assigned to the Oligocene to early Miocene age (Figure 2). The presence of Asagai-Poronai mollusks in the upper 262 part of the Muro Group first implied an Oligocene to early Miocene age for these strata (Mizuno, 1973). This is the southernmost record of the Asagai-Poronai fauna; however, it is now known to range from the late Eocene to early Oligocene in Hokkaido and northeast Honshu, northern Japan (Honda, 1994). In addition, Suzuki (1988) assigned the Aikawa Formation, in the upper part of the Muro Group, to the early to earliest middle Eocene age, based on radiolarians. Accordingly, the Shimotsuyu Formation, which is correlative with the Aikawa Formation (Tateishi et al., 1979), is tentatively treated here as an Eocene to Oligocene unit (Figure 2). Systematic description Family Buccinidae Rafinesque, 1815 Genus Trominina Oyama and Mizuno, 1958 Type species.—Ancistrolepis japonicus Takeda, 1953. Trominina hokkaidoensis (Hayasaka et Uozumi, 1954) Figure 3.4, 3.5 Ancistrolepis yudaensis Otuka var. ishikariensis Hayasaka and Matsui, 1951, p. 334, pl. 1, fig. 3 (non fig. 4). Ancistrolepis hokkaidoensis Hayasaka and Uozumi, 1954, p. 402, pl. 25, fig. 8, pl. 26, fig. 5. Trominina hokkaidoensis (Hayasaka and Uozumi). Oyama et al., 1960, p. 63, pl. 10, fig. 2 (reproduced from Hayasaka and Uozumi, 1954); Kanno and Ogawa, 1964, p. 291, pl. 4, fig. 3; Honda, 1989, p. 100, pl. 10, fig. 11. Neptunea dispar Takeda. Katto and Masuda, 1978, pl. 1. fig. 5. Material examined.—Three specimens (MES coll. cat. nos. 1037, 1038, 1039). Remarks.—This species is characterized by a high spire ornamented with one relatively weak but acutely expanded keel on the middle part of the whorl. Hayasaka and Matsui (1951, p. 334, pl. 1, figs. 3, 4) erected Ancistrolepis yudaensis Otuka var. ishikariensis from the Momijiyama Formation (lower Oligocene) of the Ishikari coalfield, cen- tral Hokkaido. Hayasaka and Uozumi (1954) later pro- posed Ancistrolepis hokkaidoensis from the Momijiyama Formation, and they doubtfully cited a specimen (Hayasaka and Matsui, 1951, pl. 1, fig. 3) as A. hokkaidoensis. Trominina hokkaidoensis differs from T. ishikariensis in having a weaker keel on the middle part of the whorl. Gladenkov et al. (1988) synonymized T. onnaica (Yokoyama), T. yubariensis, T. japonica, T. ishikariensis, T. hokkaidoensis, T. umbelliformis, and T. bicordata with T. angasiana (Yokoyama) after studying the Eocene to Oligocene buccinids in Kamchatka. Trominina yubarien- sis and T. umbelliformis are characterized by a clearly ex- Yutaka Honda panded keel on the middle part of the whorl, as is T. angasiana. However, Trominina onnaica, T. japonica, T. ishikariensis, T. hokkaidoensis, and T. bicordata all bear a relatively weak keel, which differentiates them from T. angasiana. Although the taxonomy of the above listed species should be further studied, they are considered here to differ from one another by the surface ornamentation and the outline of whorls. Trominina hokkaidoensis most closely resembles T. Japonica, known from the middle Eocene to upper Oligocene ‘Maoka’ Group in southern Sakhalin, Russia (Takeda, 1953; Kano et al., 2000). However, T. hokkaidoensis has a more distinctly expanded body whorl than does T. japonica. Katto and Masuda (1978, pl. 1, fig. 5) illustrated Neptunea dispar from the Tanami Formation, which is assigned here to T. hokkaidoensis based on its more acutely elevated spire. Associated fauna.—The present species is associated with such sublittoral to bathyal dwellers as Portlandia watasei and Turritella sp. (Table 1). Occurrence.—Loc. T1, T2. Acknowledgments I express my deep gratitude to Kenshiro Ogasawara (University of Tsukuba) for helpful suggestions and critical reading of the manuscript, and to Louie Marincovich, Jr. (California Academy of Sciences), for critical review of the manuscript. I also express my gratitude to Yukio Sako (Kushimoto-cho, Wakayama Prefecture) for his assistance during the field work. 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(in Japanese with English abstract) 263 Paleontological Research, vol. 6, no. 3, pp. 265-284, September 30, 2002 © by the Palaeontological Society of Japan Migration and speciation of the Loxoconcha japonica species group (Ostracoda) in East Asia GENGO TANAKA AND NORIYUKI IKEYA Department of Life and Earth Sciences, Shizuoka University, Shizuoka 422-8529, Japan (e-mail: gengo@po2.across.or.jp; senikeya@ms.ipc.shizuoka.ac.jp) Received October 4, 2001; Revised manuscript accepted May 13, 2002 Abstract. Eighty-five fossil and Recent species of the genus Loxoconcha (Crustacea: Ostracoda) from East Asia are systematically reexamined. On the basis of carapace morphology, the genus Loxoconcha from East Asia is divided into five species groups: L. pulchra, L. optima, L. japonica, L. uranouchiensis and L. japonica species groups. The migration and speciation patterns of four species of the L. japonica species group are as follows. In Late Miocene, L. lilljeborgii and L. tumulosa were distributed over the Paleo-Indian Ocean. In Early Pliocene time, these species migrated to the Western Pacific and L. japonica evolved from populations of L. tumulosa by peramorphic evolution. In the Middle Pleistocene, L. shanhaiensis evolved from popula- tions of L. japonica in the Ryukyu Islands by paedomorphic evolution. Key words: East Asia, Loxoconcha, Ostracoda, paedomorphic evolution, paleobiogeography, peramorphic evolution, Introduction The genus Loxoconcha was proposed by Sars (1866) with the type species Cythere rhomboidea Fischer (1855), based on a Recent specimen from Lervig (= Larvik), South Norway. Since then, about 550 species belonging to this genus have been identified from around the world (Kempf, 1986). The oldest fossil record is from the Eutaw Formation (late Cretaceous) of northwest Selma, Dallas City, Alabama, North America (Crane, 1965). This genus is reported from the Paleogene of four continents: North America (Hazel et al., 1980; Howe, 1963; Carrefio and Cronin, 1993), Australia (Mckenzie et al., 1991, 1993), Africa (Cronin and Khalifa, 1979; Ahmad et al., 1991) and Europe (Keij, 1957); thus its distribution had already be- come worldwide. Today, it is widely distributed in littoral, sublittoral and brackish-water environments throughout the world except for the polar regions (Athersuch and Horne, 1984). The genus Loxoconcha is an evolutionarily successful group, with one of the highest species diversity of all ostracod genera. Its species have adapted to various habi- tats, often developing morphological characters in adapting to microhabitats. In East Asia, 85 species of Loxoconcha have been de- scribed since 1868 when Brady reported two Recent spe- cies from Batavia, Java, present-day Indonesia (Brady, 1868). Based on carapace outlines, surface ornamentation patterns, hinge structures and muscle scar patterns, Loxoconcha can be classified into five species groups (Figure 1). Morphological similarity among Loxoconcha species is affected either by the genotype or environmental interactions or both. It is possible to estimate the relative importance of each by investigating intraspecific morpho- logical variants and their geographical, stratigraphical and ontogenetical variability. In this study, we focus on the neritic L. japonica species group. We compare morpho- logical characters among species and evaluate the pre- sumed phylogenetic relationships among species based on inter-specific morphological similarities. Finally, we con- sider geographic dispersal processes and mechanisms of adaptation to local environments. Material This study is based mainly on Recent and fossil faunal- slides housed at Shizuoka University. Collections of Loxoconcha come from 35 localities (23 Recent; 12 fossil) which range geographically from Suttsu Bay (Hokkaido, Japan) to Taiwan (Figure 2 and Table I). All figured specimens have been deposited at the Shizuoka University Museum, Japan (SUM-CO-Number). 266 Gengo Tanaka and Noriyuki Ikeya + [| Lpuichre à > ¥ Me ee > + 5 nu © — © 2 Q fe) ial a) D = =E Oo pee © 16) 19) A O D 5 = Figure 1. Morphological classifications of genus Loxoconcha from East Asia Loxoconcha, which includes 85 species from the East Asia, is divided into the following five species groups on the basis of carapace morphology (Figure 1). They in- clude those species which have not been given species names (indicated by L. sp.) and those referred to in quotes in the literature. Loxoconcha pulchra species group. — Carapace subrhomboidal in lateral view. Surface ornamentation of the carapace consists of concentrically-arranged pits or weak reticulation, except for the dorsal area. In dorsal view, ornamentation not developed. In ventral view, five pairs of ridges diverge toward anterior. Posterior element of hingement is ball-shaped. Prominent fulcral point. A total of six species are included: L. pulchra, L. sub- circulata, L. subpulchra, L. sp. (Hou et al., 1982), L. sp. C (Ikeya et al., 1985), “L. pulchra” (in Gou et al., 1981). Loxoconcha optima species group.—Carapace subrhom- boidal in lateral view. Surface ornament of the carapace consists of concentrically-arranged ridges or pits as located Five species groups of Loxoconcha in the East Asia, defined on the basis of their carapace morphology. Not to scale. around the position of the muscle scar, except for the dorsal area. In dorsal view, ornamentation not developed. In ventral view, five pairs of ridges run parallel from anterior to posterior. Posterior element of hingement is composed of three teeth. Prominent fulcral point. A total of sixteen species are included: L. chinzeii, L. hemicrenulata, L. ikeyai, L. medioconvexa, L. optima, L. orientarica, L. pleistocenica, L. taiwanensis, L. tamakazura, L. tarda, L. sp. (Hu, 1978), L. sp. (Ishizaki, 1984), L. sp. (Yajima, 1988), “L. pulchra” (in Yajima, 1988), “L. sinensis” (in Gou et al., 1981), “L. sinensis” (in Zhao et al., 1985). Loxoconcha japonica species group.—Carapace sub- rhomboidal in lateral view. Surface ornament of the cara- pace consists of concentrically- arranged pits or coarse reticulation centered around the muscle scars. In dorsal view, a pair of ridges converges toward the anterior. In ventral view, five pairs of ridges developed that run paral- lel from anterior to posterior. Posterior element of hingement is ball-shaped. Fulcral point not prominent. The following four species are included: L. japonica, L. lilljeborgii, L. shanhaiensis, L. tumulosa. Loxoconcha uranouchiensis species group. — Carapace Migration and speciation of Loxoconcha 267 Table 1. Sample localities for L. japonica species group from East Asia. Sample numbers corresponds to those in Figure 2. Abbreviations: Alg. Algae; M. = Mud; St. = Silt; Sd = Sand; R. = Rock; f. = fine; m. = medium; c. = coarse; mdy. = muddy; sdy. = sandy; gry. = gravelly; L. = late; M. middle; E. = early; Ls. = Limestone; Pref. = Prefecture; Penin. = Peninsula; Is. = Island; Ja = L. japonica ; Sh = L. shanhaiensis ; Tu = L. tumulosa ; Li = L. lilljeborgii. Recent matenals Sample number Localities Latitude (N) Longitude (E) Depth (m) Remarks Species la Suttu Bay 42°48.9° 140°18.0° 22 R. Ja Ib ” 42°47.8° 140°16.2° 34 f.-Sd. Ja Ic 4 42°47.2° 140°18.7° 9 R. Ja Id ” 42°47.2° 140°15.6° 26 f.-Sd. Ja le " 42°46.7° 140° 17.9° 11 f.-Sd. Ja If „ 42°46.7° 140°15.6° 17 f.-Sd. Ja lg ” 42°46.2° 140°16.5° 7 c.-Sd. Ja Ih ” 42°46.2° 140°15.0° 5 c.-Sd. Ja 2 Otsuchi Bay 39°19.6° 141°55.0° 15 c.-Sd. Ja 3 Imagawa 38°24.6° 139°28.1° 0 Alg. Ja + Aikawa 38°02.4° 138°14.3° 0 Alg. Ja 5 Hayase 35°37.0° 135°54.7° I Alg. Ja 6 Kagoshima 3539/57 134°46.8° 0 Alg. Ja 7 Off Shimane 36°13.9° 133°06.0° 96 mdy., f.-m.-Sd Ja 8 Misaki 35°09.5° 139°37.0° 0 Sea glass Ja 9 Osezaki 35°06.3° 138°47.4° l Alg. Ja 10 Ago Bay 34°57.1° 136°40.5° 7 f.-Sd. Ja 11 Hanesaki 33°22.0° 134°02.4° 0 Alg. Ja 12 Uwajima Bay 33°10.8° 132°29.9° 5 v. c.-Sd. Ja 13 Tsuyasaki 33°47.4° 130°27.7° 2 m.-Sd. Ja 14 Danjyo Islands 32°01.9° 128°23.1° 86 f.-Sd. Ja 15 Okawa-minato 31°14.6° 130°24.8° 0 Alg. Ja 16 Tanega-shima Is. 30°10.3° 130°52.7° 96 c. shelly-Sd. Ja 17 Amami-o-shima Is. 28°07.5° 129°22.0° 4 coral Sd. Ja, Sh 18 Tokuno-shima Is. 27°51.6° 128°57.7° 0 Alg. Ja, Tu 19 Yoron Is. 27°02.9° 128°27.3° 0 Alg. Ja, Sh, Tu, Li 20a Nago Bay 26°34.1° 127°56.4° 38 m.-St. Sh 20b Lf 26°39.3° 127251.3: 59 m.-Sd. Ja, Sh 20c u 26237516 12755225 22 m.-Sd. Ja, Sh 20d Li 26°36.1° 127°53.5° 40 c.-Sd Ja, Sh 20e Nakagusuku Bay 2219.27 127°52.0° 4 sdy.-M. Ja, Li 20f a 26° 16.87 127°50.3° 6 gry.-Sd. Sh, Li 20g ” 26219195 127°54.3° 21 Sd. Ja, Sh, Tu, Li 20h 1 2641573 12725314 4 gry.-Sd. Ja, Sh 20i Mt 26°15.0° 127°52.3° 20 Sd. Ja, Sh 20) ” 26°12.8° 127°55.0° 48 Sd.,-M. Ja, Sh, Li 20k Mt 26°12.5° 127°52.9° 28 mdy.-Sd. Ja, Sh, Li 201 „ 26°10.1° 127°52.8° 22 Sd. Ja, Sh 20m „ 26°07.8° 127°53.9° 70 gry.-Sd. Ja, Sh, Li 21 Off Miyako Is. 24°47.9° 127°37.4° 124 c.-Sd. Sh 22 Sekisei-sho 24°27.4° 124°03.3° 167 f.-Sd. Ja, Sh 23 Hengchun Penin. 21°56.0° 120°49.0° 0 Alg. Sh, Tu Fossil materials Sample number Formation (age) Localities Latitude (N) Longitude (E) Remarks Species a Hamada (L. Pleistocene) Shimokita Penin. 41°10.3° 141°16.4° Ja bi Sawane (Pliocene) Sado Is. 37°59.6° 138°15.6° Ja b2 Sawane (Pliocene) 7 37°59.3° 138°15.9° Ja cl Hiradoko (L. Pleistocene) Noto Penin. 37°27.0° 137°18.2° Ja c2 Miyainu (L. Pleistocene) 4 37°20.2° 137°13.8° Ja c3 Numashiro (L. Pleistocene) 7 35°19.4° 139°15.4° Ja di Ninomiya (L. Pleistocene) Oiso Hill 35°18.9° 13915714 Ja d2 (4 7 35°18.4° 139°15.4° Ja d3 „ Z 35°18.2° 139215775 Ja e Takahama (Holocene) Fukui Pref. 35°29.2° 135°33.3° Ja f Hamamatsu (Holocene) Hamana-ko 34°44.8° 137°36.5° Ja £ Ananai (Plio-Pleistocene) Shikoku 33°29.4° 133°56.7° Ja h Shimo-jiro (M. Pleistocene) Okino-erabu Is. 27°24.5° 128°38,3° Sh i Maja (E. Pliocene) Kume Is. 26°22.6° 126°47.4° Ja jl Yonabaru (L. Pliocene) Okinawa Is. 26°09.7° 127°46.7° Ja j2 Chinen Sand (E. Pleistocene) Okinawa Is. 26°07.3° 127°43.8° Ja k Tungshiao (L. Pleistocene) Taiwan 24°36.0° 120°43.0° Sh ll Hengchun Ls. (L. Pleistocene) Taiwan 21°59.0° 120°43.0° Ja, Sh, Li 12 Hengchun Ls. (L. Pleistocene) Taiwan 21°55.0° 120°51.0° Sh, Tu 268 Gengo Tanaka and Noriyuki Ikeya Pacific Ocean Figure 2. Map showing sampling localities. Numbers and lower case letters correspond to the sample numbers in Table 1. subrhomboidal to oblong in lateral view. Surface orna- ment of the carapace consists of reticulation. In dorsal view, the carapace is covered with irregular reticulation. In ventral view, three- or four-pairs of ridges run parallel from anterior to posterior, the most ventral pair being de- veloped only in the anterior region. Posterior element of hingement is ball-shaped. Prominent fulcral point. A total of forty-three species are included: L. bispinosa, L. bizenensis, L. brevia, L. crassela, L. crispatum, L. epeterseni, L. hanachirusato, L. harimensis, L. hattorii, L. kattoi, L. kitanipponica, L. malayensis, L. nozokiensis, L. paiki, L. pashihaiensis, L. prolaeta, L. sinensis, L. tata, L. tosaensis, L. tosamodesta, L. triconicula, L. uranouchien- sis, L. ventispina, L. viva, L. xuwenensis, L. yinggehaiensis, L. zamia, L. zhejiangensis, L. sp. A (Huh, 1992), L. sp. B (Ishizaki, 1968), L. sp. B (Lee, 1990), L. sp. C (Huh, 1992), L. sp. 2 (Yamane, 1998), “L. hattorii” (in Cai, 1982), “L. hattorii” (in Wang and Zhang, 1987), “L. kattoi” (in Ruan and Hao, 1988), “L. sinensis” (in Gou et al., 1981), “L. sinensis” (in Ruan and Hao, 1988), “L. uranouchiensis’ (in Cai and Chen, 1987), “L. cf. uranouchiensis” (in Gou et al., 1983), “L. uranouchiensis” (in Tabuki et al., 1987), “L. uranouchiensis” (in Yamane, 1998), “L. viva” (in Wang et al., 1988). Loxoconcha ozawai species group.—Carapace subrhom- boidal to oblong in lateral view. Surface ornamentation of the carapace consists of weak reticulation. In dorsal view, the carapace is covered with weak, irregular reticulation. In ventral view, two pairs of weak ridges converge toward anterior. Posterior element of hingement is ball-shaped. Prominent fulcral point. The following sixteen species are included: L. binhaiensis, L. elliptica, L. fujianensis, L. gigantea, L. hataii, L. ocellata, L. ozawai, L. subkotora- forma, L. sp. (Ikeya et al., 1992), L. sp. (Tsukagoshi and Kamiya, 1996), L. sp. B (Huh, 1992), L. sp. B (Ishizaki, 1971), L. sp. D (Huh, 1992), L. sp. 1 (Ozawa, 1996), L. sp. 1 (Yamane, 1998), “L. sinensis” (in Zhao and Wang, 1988). Natural history of Loxoconcha japonica species group Morphological characters In order to characterize the L. japonica species group, four species of the group were compared in terms of cara- pace morphology (Figures 3, 4), pore system (Figure 5), ap- pendages (Figure 6) and male copulatory organ (Figure 7). The following summarizes the morphology of this species group. Carapace outline.—Carapace subrhomboidal in lateral view. Dorsal margin straight and sloped toward anterior or arched dorsally; anterior margin with an oblique curva- ture; ventral margin slightly concave at mid-anterior area; posterior margin curved toward the dorsal. Caudal process protrudes prominently toward posterodorsal. In dorsal and ventral view, carapace diamond- to wedge-shaped. In pos- terior view, carapace elliptical to egg-shaped. Large sex- ual dimorphism; in lateral view, male more elongate. Carapace ornamentation.—Surface of the carapace is entirely ornamented with pits or coarse reticulation in lat- eral view. The ornamentation is concentrically arranged, consisting of eight rings centered around the position of the muscle scar. Posteroventral alate ridge and/or postero- dorsal protuberance are/is sometimes developed. In ventral view, five pairs of ridges run parallel from the ante- rior to posterior margins. In dorsal view, a pair of ridges converges toward the anterior. In posterior view, on the ventral side of the posterior margin, four pairs of short ridges are developed that consist of reticulations arranged parallel to the posterior margin. On the dorsal side of the posterior margin, on the other hand, radially-developed ridges centered near the position of the caudal process in- tersect ridges that parallel the posterior margin. Hinge.—Gongylodont. In left valve, anterior element is Migration and speciation of Loxoconcha 269 Figure 3. 1-3, 6. Loxoconcha japonica Ishizaki, 1968. 4,5, 7. Loxoconcha lilljeborgii Brady, 1868. 1. A male carapace of the same speci- men in external left lateral view (a), posterior view (b), right lateral view (c) and dorsal view (d) from sample no. 8 (SUM-CO-1269). 2. A female carapace of the same specimen in external view (a-d) from sample no. 8 (SUM-CO-1270). 3. A female carapace of the same specimen with alate ridge at the posteroventral area in external view (a-d) from sample no. 17 (SUM-CO-1271). 4. A male carapace of the same specimen in external view (a-d) from sample no. 19 (SUM-CO-1305). 5. A female carapace of the same specimen in external view (a-d) from sample no. 19 (SUM-CO-1306). 6. Hingement of female right (a) (SUM-CO-1272) and left (b) (SUM-CO-1273) valves from sample no. 19. 7. Hingement of female right (a) (SUM-CO-1307) and left (b) (SUM-CO-1308) valves from sample no. 19. Scale bars = 100 um (A for 1-5; B for 6, 7). Gengo Tanaka and Noriyuki Ikeya TE a DA BRL Se ER Pr i = m er + pide 7,3 Mokisipeth Pompe, ml, Le 1, 2, 5. Loxoconcha shanhaiensis Hu, 1981. 3, 4, 6. Loxoconcha tumulosa (Hu, 1979). 1. A male carapace of the same specimen in external left lateral view (a), posterior view (b), right lateral view (c), dorsal view (d) and ventral view (e) from sample no. 17 (SUM-CO-1284). 2. A female carapace of the same specimen in external view (a-e) from sample no. 17 (SUM-CO-1285). 3. A male carapace of the same specimen in external view (a-d) from sample no. 23 (SUM-CO-1294). 4. A female carapace of the same specimen in external view (a-d) from sample no. 23 (SUM-CO-1295). 5. Hingement and muscle scars of female right (a) (SUM-CO-1286) and left (b) (SUM-CO-1287) valves from sample no. 20h. 6. Hingement of female right (a) (SUM-CO-1296) and left (b) (SUM-CO-1297) valves from sample no. 23. Scale bars = 100 um (A for 1-4; B for 5, 6). Figure 4. Migration and speciation of Loxoconcha 271 a down-turned claw, median element with 25-51 teeth, and posterior element is ball-shaped. Ocular sinus.—In all four species, nipple-like projection develops at the dorsoposterior portion in internal view. Muscle scars.—Four adductor muscle scars in an arcuate row, concave anterior. The upper of the two middle ones is larger than the rest. A bean-shaped frontal scar of oc- curs in front of the lower two adductor muscle scars. Two mandibular scars in front and below the lowest adductor muscle scar. Fulcral point absent. Pore system.—In all species, 83 sieve-type pores are dis- tributed in each adult valve, and each pore opening location resembles among four species (left side of Figure 5). Distribution of radial pores falls into two patterns (right side of Figure 5), depending on numbers of pores extending to marginal area: a), 11 in anterior area and 5 in posterior area: L. japonica, L. shanhaiensis and L. tumulosa; b), 10 and 5, respectively: L. lilljeborgii. Moreover, L. lillje- borgii is differentiated from the other three species, in that Figure 5. The pattern of distribution pores in external view (A-D) and the radiation of radial pores in internal view (a-d) on four species of the Loxoconcha japonica species group (all specimens are female left valves). A, a. Loxoconcha japonica Ishizaki, 1968 (A, SUM-CO-1262; a, SUM-CO-1263). B, b. Loxoconcha shanhaiensis Hu, 1981 (B, SUM-CO-1274; b, SUM-CO-1275). C, c. Loxocon- cha tumulosa (Hu, 1979) (C, SUM-CO-1288; c, SUM-CO-1289). D, d. Loxoconcha lilljeborgii Brady, 1868 (D, SUM-CO-1298; d, SUM-CO-1299). Scale bar = 100 um. Figure 6. Chitinous parts of Loxoconcha shanhaiensis Hu, 1981 from sample no. 20f. A, antennule; B, antenna (SUM-CO-1277); C, man- dible; D, maxilla (SUM-CO-1278); E, first thoracic leg; F, second thoracic leg; G, third thoracic leg (SUM-CO-1279). Scale bar = 50 um. 272 Gengo Tanaka and Noriyuki Ikeya Figure 7. Male copulatory organs of three species of Loxoconcha japonica species group. A. Loxoconcha japonica Ishizaki, 1968 from sample no. 8 (SUM-CO-1264). B. Loxoconcha shanhaiensis Hu, 1981 from sample no. 20f (SUM-CO- 1276). C. Loxoconcha lilljeborgii Brady, 1868 from sample no. 19 (SUM- CO-1300). Scale bar = 50 um. the upper two pores of at the posterior margin branch in the middle of the marginal infoldment. Appendages.—No significant differences are observed among the four species. Male copulatory organ.—Except for L. tumulosa, outline of the basal capsule is trapezoidal and costa are developed in three species. In detail, however, several differences are observed among the three species in morphology of the copulatory organ. Distal corner rounded in L. lilljeborgii but tapered in L. japonica and L. shanhaiensis, ductus ejaculatorius curved in L. lilljeborgii but shoehorn-shaped in L. japonica and L. shanhaiensis; clasping apparatus ab- sent in L. japonica, triangular in L. shanhaiensis and square in L. lilljeborgii. Ontogenetic differentiation in carapace morphology For the carapace morphologies of the four species, the ontogenetic differentiation from the A-2 instar to the adult were compared. Carapace outline (Figure 8).—The position of the maxi- mum height shifts toward the posterior from the A-2 instar to the adult. The time of shift is at the A-1 instar for L. ja- ponica and L. lilljeborgii and at the adult for L. shanhaiensis and L. tumulosa. The position of the maximum width is stationary from the A-2 instar to the adult (L. shanhaiensis and L. tumulosa) or shifts to the anterior at the adult (L. lilljeborgii and the male of L. japonica). Carapace ornamentation (Figure 8).—The concentric ar- rangement of reticulation or pits is fixed from the A-2 instar to the adult. From the A-2 instar to the adult, the developmental state of reticulation or pits, however, differs from species to species. Namely, L. japonica already has adult-like coarse reticulation in the A-2 instar, but L. shanhaiensis and L. tumulosa only attain coarse reticulation in the A-1 instar. L. lilljeborgii has pits in the A-2 and A-1 instars, and is smoothly reticulate in the adult. The posteroventral alate ridge is well developed in the A-2 and A-1 instars of all four species. In the adult, this character is retained in L. shanhaiensis and L. tumulosa, but disappears in L. lilljeborgii and the male of L. japonica. In the female of L. japonica, however, some specimens keep and others lose this character. The posterodorsal protuberance does not appear during ontogenetic development in L. japonica and L. shanhaiensis, whereas, it appears from the A-1 instar on- ward in L. tumulosa and L. lilljeborgii. Hinge (Figure 9).—Although development of the ante- rior element of the hinge is weak in the A-2 instar, these species clearly possess a gongylodont hinge after the A-1 instar. The number of teeth in the median element could not be counted in the A-2 instar, since it is smooth, how- ever, from the A-1 instar onward the number of teeth is: 42-51 in L. japonica, 39-40 in L. shanhaiensis, 31-40 in L. tumulosa, and 25-31 in L. lilljeborgii. Ocular sinus (Figure 9).—The nipple-like projection in the dorsoposterior area on the internal side appears after the A-2 instar for L. japonica, L. shanhaiensis and L. tumulosa and after the A-1 instar for L. lilljeborgii. Muscle scars (Figure 4).—After the A-2 instar, the four species have four adductor muscle scars in an arcuate row; with no morphological variation in this feature among the species. Pore system (Figure 8).—The total number of sieve-type pores per valve is the same in all four species: 54 in the A-2 instar, 73 in the A-1 instar and 83 in the adult. From the carapace characters described above, it is thought that L. japonica, L. lilljeborgii and an ancestor of L. shanhaiensis-L. tumulosa differentiated at the A-2 instar, and that L. shanhaiensis and L. tumulosa differenti- ated in the A-1 instar (Figure 10). Migration and speciation of Loxoconcha Max. height ac 1/2 1/5 GIE | Max. width = BE. |. |... a ee a ae | 273 ace omamentation ar Lin i ae L. tumulosa er al alu) ow | m nl ul mw | à | ow | » | os | een Beer L. tumulosa 83 L lillebora Figure 8. Schematic diagram of ontogenetic differentiation of carapace morphology. Abbreviations: AC = anterior cardinal angle, H = maxi- mum height, W = maximum width on dorsal view, W’ = maximum width on posterior view, CR = coarse reticulation, FR = fine reticulation, P = pit, AR = alate ridge, PT = protuberance. Paleobiogeography On the basis of our materials and published reports, we considered the paleobiogeographic distributions of the four species. Fossil distribution (Figure 11).—The oldest specimens of L. lilljeborgii and L. tumulosa occur in the Late Miocene Round Chalk and Silt Formation from the Andaman Islands of the Indian Ocean (Loc. A: Guha, 1968). Two species are also reported from the Pliocene Guiter Formation from the same region (Loc. A’: Guha, 1968). These two spe- cies, however, occur also in the Late Pleistocene in the West Pacific region. Namely, L. lilljeborgii occurs from the Late Pleistocene Hengchun Limestone from Taiwan (Loc. E: Figure 2, 11) and in the Late Pleistocene Gundurimba Clay from Australia (Loc. C: McKenzie and Pickett, 1984), and L. tumulosa occurs from the Late Pleistocene Hengchun Limestone from Taiwan (Loc. D: Figure 2, loc. 12). The oldest specimen of L. japonica comes from the Early Pliocene Maja Formation from Kume Island of the Ryukyus (Loc. G: Figure 2, loc. i). This species also oc- curs in thirteen post-Pliocene formations ranging from Taiwan to the northern part of Honshu (Locs. D, H and J-S) and in Holocene sediments from Hong Kong (Loc. B: Cao, 1998). The oldest fossil occurrence of L. shanhaiensis is known one fase Élus à À pe (ao) > © Ev — ae 3 > 5 © zZ a) =! Ss = S| a Fr © 2) = ay 6) cr: Ts Pr Ve Dan do es Poe. tm en eS secs om y Nope Migration and speciation of Loxoconcha 275 L. japonica L. shanhaiensis L. tumulosa L. lilljeborgii Figure 10. Ontogenetic differentiation of four species based on carapace characters. © L japonica @ L. shanhaiensis À L.tumulosa . hill ii en Pacific Ocean ©) oe East China Sea ‘ cob foe x : BO E Ne Figure 11. Geographic distribution of four species of Loxoconcha japonica species group (fossil). A and A’ (Late Miocene Round Chalk and Silt Formation and Pliocene Guiter Formation; Guha, 1968); B (Holocene Hang Hau Formation; Cao, 1998); C (Late Pleistocene Gundurimba Clay; McKenzie and Pickett, 1984); D (Late Pleistocene Hengchun Limestone; Hu, 1979); E (Late Pleistocene Hengchun Limestone; Hu, 1981); F (Late Pleistocene Tungshiao Formation; Hu, 1986); G (Early Pliocene Maja Formation); H (Early Pleistocene Chinen Sand); I (Middle Pleistocene Shimo- jiro Formation); J (Early Pleistocene Sogwipo Formation and Middle Pleistocene Shinyangri Formation; Lee, 1990); K (Plio-Pleistocene Ananai Formation); L (Holocene Takahama shell bed); M (Holocene Hamamatsu Formation); O (Holocene bore hole core samples; Irizuki er al., 1998); P (Plio-Pleistocene Omma Formation; Ozawa, 1996); Q (Late Pleistocene Miyainu and Numashiro formations); R (Pliocene Sawane Formation); S (Late Pleistocene Hamada Formation). @ Figure 9. Juvenile specimens of Loxoconcha japonica species group. 1, 2. Loxoconcha japonica Ishizaki, 1968. 3, 4. Loxoconcha shanhaiensis Hu, 1981. 5, 6. Loxoconcha tumulosa (Hu, 1979). 7, 8. Loxoconcha lilljeborgii Brady, 1868. 1. A-1 stage carapace of same speci- men in external left lateral view (a), dorsal view (b) and posterior view (c) from sample no. 8 (SUM-CO-1265), and hingement of the same stage of left valve (d) from sample no. 8 (SUM-CO-1266). 2. A-2 stage carapace of same specimen in external view (a-c) from sample no. 8 (SUM- CO-1267), and hingement of the same stage of left valve (d) from sample no. 8 (SUM-CO-1268). 3. A-1 stage carapace of same specimen in ex- ternal view (a-c) from sample no. 20h (SUM-CO-1280), and hingement of the same stage of left valve (d) from sample no. 20h (SUM-CO-1281). 4. A-2 stage carapace of same specimen in external view (a-c) from sample no. 20h (SUM-CO-1282), and hingement of the same stage of left valve (d) from sample no.20h (SUM-CO-1283). 5. A-1 stage carapace of same specimen in external view (a-c) from sample no. 23 (SUM-CO-1290), and hingement of the same stage of left valve (d) from sample no. 23 (SUM-CO-1291). 6. A-2 stage carapace of same specimen in external view (a-c) from sample no. 23 (SUM-CO-1292), and hingement of the same stage of left valve (d) from sample no. 23 (SUM-CO-1293). 7. A-1 stage carapace of same specimen in external view (a-c) from sample no. 19 (SUM-CO-1301), and hingement of the same stage of left valve (d) from sam- ple no. 19 (SUM-CO-1302). 8. A-2 stage carapace of same specimen in external view (a-c) from sample no. 19 (SUM-CO-1303), and hingement of the same stage of left valve (d) from sample no. 19 (SUM-CO-1304). Scale bars = 100 pm. (A for a-c; B for d) 276 Gengo Tanaka and Noriyuki Ikeya (er N © L. japonica | 40" @ L. shanhaiensis A L. tumulosa @ L. lilljeborgii Indian Ocean 160°E EEL ia Geographic distributions of four species of Loxoconcha japonica species group (Recent). a (Mauritius; Brady, 1868), b (Burma; Figure 12. Gramann, 1975); c (Sunda Shelf; Mostafawi, 1992); d (Hainan Island; Gou, 1990); e (Hong Kong); f (Manila Bay; Keij, 1954); g (Cebu Island); h (West Australian Coast; Hartmann and Hartmann, 1978); i (Lizard Island; Behrens, 1991); j (Guam); k (Truk); I (Marshall Islands); m (Gilbert Islands); n (Samoa); o (Tuamotu Islands; Hartmann, 1984); p (South Taiwan); q (Sekisei-sho); r (Miyako Island); s (Okinawa); t (Yoron Island); u (Tokuno-shima Island); v (Amami-o-shima Island); w (southern part of Korean Peninsula; Choe, 1984MS); x 1-17 (Japan coast; x6 = Uranouchi Bay; Ishizaki, 1968). e, g, and j-n (R. Ross, pers. comm., 2002). from the Middle Pleistocene Shimo-jiro Formation from the Okino-erabu Island of the Ryukyus (Loc. I: Figure 2, loc. h). This species also occurs in two Late Pleistocene formations from Taiwan, the Hengchun Limestone (Locs. D and E: Figure 2, locs. 11 and 12) and the Tungshiao Formation (Loc. F: Figure 2, loc. k). Recent distribution (Figure 12).—L. lilljeborgii is widely distributed over lower latitude coastal regions of the Indian Ocean (Locs. a and b), the South China Sea (Locs. d and f), the northern part of Australia (Locs. h and 1) and the Ryukyus (Locs. s, t and v: Figure 2, locs. 17, 19 and 20). L. tumulosa is distributed over lower latitudes in the West Pacific coastal regions of the South China Sea (Locs. c, d and g), the northeastern part of Australia (Loc. 1), many is- lands of the West Pacific (Locs. j-o), Taiwan (Loc. p: Figure 2, loc. 23), and the Ryukyus (Locs. s-u: Figure 2, locs. 18-20). L. japonica is distributed over lower-to mid- dle latitude coastal regions from Hong Kong to Japan (Locs. e, q, s, t, u, v, w and x1-17: Figure 2, locs. 1-20 and 22). L. shanhaiensis is only distributed over the lower lati- tude coastal regions of Hainan Island (Loc. d), Taiwan (Loc. p: Figure 2, loc. 23) and the Ryukyus (Locs. q-t: Figure 2, locs. 17 and 19-22). The dispersal and evolution of the four species can be in- Pacific Ocean Japan Sea xt East China se / AI .Z—@AEK)s Hog £ 160 W ferred from these data (Figure 13). Firstly, L. lilljeborgii and L. tumulosa were distributed over the Indian Ocean in the Late Miocene. Secondly, these species migrated from the Indian Ocean to the West Pacific Ocean during the Early Pliocene. Based on morphological and ontogenetic information, together with biogeographic data, L. japonica evolved from the northern population of L. tumulosa. Finally, L. shanhaiensis evolved from the southern population of L. japonica in the Middle Pleistocene. These inferences are discussed in greater detail below. Discussion Paleobiogeographic and ontogenetic changes in the cara- pace morphology of the L. japonica species group from East Asia are the key to interpreting the phylogeny of the group. In the preceding section, we deduced that L. japon- ica evolved from L. tumulosa in the Early Pliocene. In L. japonica, the lateral outline and the surface ornamentation change in the A-1 instar and the A-2 instar, respectively. In contrast, in L. tumulosa, the lateral outline and the sur- face ornamentation change in the adult and the A-1 instar, respectively. Futhermore, in L. japonica, the alate ridge, which is a common character among the juvenile stages of 277 Migration and speciation of Loxoconcha (a) about 7 Ma (b) 2- 1.7 Ma Figure 13. Paleobiogeographic distribution of Loxoconcha japonica species group around the Ryukyus. (c) 1.7-1Ma 2 ci ba | D O © © V (f) Recent Shaded zones are land areas. Loxoconcha japonica Ishizaki, 1968 (open diamond shapes), Loxoconcha shanhaiensis Hu, 1981 (solid squares), L. tumulosa (Hu, 1979) (solid trian- gles) and L. lilljeborgii (solid circles). (1996). all four species, disappears in most adult specimens. From this evidence, the carapace characters of L. japonica are considered to have developed by peramorphosis. Moreover, it was deduced that L. shanhaiensis differenti- ated from L. japonica in the Middle Pleistocene. In L. shanhaiensis, ontogenetic changes of the lateral outline and Paleogeographic reconstructions are after (a), Ujiié (1986); (b)-(d), Kimura (1996); (e), Ujiié and Nakamura the surface ornamentation are delayed by one stage, and the adult stage retains the alate ridge. These data indicate that the carapace characters of L. shanhaiensis are derived from L. japonica by paedomorphosis. A heterochronic process results from the modification of the relationships among three parameters-age, size and 278 Gengo Tanaka and Noriyuki Ikeya shape-which are assumed to be independent (Gould, 1977). Peramorphosis and paedomorphosis are each subdivided into three processes, and heterochronic evolution is de- scribed by one or more of these six processes (Kluge, 1988). In many taxa, it is generally assumed that age is equivalent to size when dealing with fossils, but in fact the relationship between age and size is not always correlative. In the case of ostracods, each instar can be compared in relative age, but relative age does not always correspond to absolute age. If it is assumed that the relative age equals the absolute age, we can consider age and size to be inde- pendent of each other. We cannot decide which of the six processes can be applied to the heterochronic evolution of the L. japonica species group, because we lack information on the earliest ontogenetic stage of each species. Nonetheless, we can state that either peramorphosis or paedomorphosis has occurred. If the number of moltings is the same among the four species, then it is likely that L. japonica became differentiated from L. tumulosa by pre- displacement and L. shanhaiensis was derived from L. japonica by post-displacement. To solve these phylo- genetic problems, it is essential to clarify the life history of the species in culturing experiments (Ikeya and Kato, 2000). Systematic descriptions Order Podocopida G. W. Miiller, 1894 Suborder Podocopina Sars, 1866 Superfamily Cytheracea Baird, 1850 Family Loxoconchidae Sars, 1925 Subfamily Loxoconchinae Sars, 1925 Genus Loxoconcha Sars, 1866 Loxoconcha japonica Ishizaki, 1968 Figures 3.1-3.3, 3.6; 5A, 5a; 7A; 9.1, 9.2 Loxoconcha japonica Ishizaki, 1968, p. 28, 29, pl. 2, fig. 1, pl. 6, figs. 10-12; Ishizaki, 1971, p. 86, pl. 3, fig. 21; Okubo, 1980, p. 416-418, figs. 12, 13, 18a-d; Hu, 1981, p. 77, pl. 3, fig. 7; Kamiya, 1988a, pl. 1, figs. 1-7, text-figs. 4, 5, 7, 8, 10, 11, 13; Kamiya, 1988b, pl. 1, figs. 1-6; Kamiya, 1988c, pl. 1, figs. 9-16; Kamiya, 1989a, pl. 1, figs. 1-8, 13, 14, 17, pl. 2, figs. 1-3, 10, text-figs. 1-8; Kamiya, 1989b, figs. 3, 4, 6, 7, 9, 11, 12; Ruan and Hao, 1988, p. 323, pl. 57, figs. 11-13; Lee, 1990, p. 358, pl. 34, figs. 3, 4; Ikeya and Suzuki, 1992, pl. 5, fig. 9; Kamiya and Hazel, 1992, figs. 1, 3, 4, pl. 1; Kamiya and Nakagawa, 1993, pl. 5, figs. 11, 12; Ozawa, 1996, pl. 6, fig. 5; Cao, 1998, pl. 3, figs. 16-19; Inzuki et al., 1998, fig. 3-5; Yamane, 1998, pl. 6, fig. 2; Yasuhara and Irizuki, 2001, pl. 6, fig. 12. Loxoconcha impressa (Baird). Kajiyama, 1913, p. 9, pl. 1, figs. 50, 51. Table 2. Measurements of valve of Loxoconcha japonica Ishizaki, 1969 from sample nos. 1, 6, 8 and 17. Abbreviations: Av = average; OR = observation range; N = number of specimens; M = male; F = fe- male; R = right; L = left. Length (mm) Height (mm) Sample (No.) Sex Valve Av. OR AV. OR Suttu Bay (1) M R 0.65 0.63-0.67 0.45 043-046 15 M L 0.66 0.64-0.69 0.44 041-046 14 F R 0.58 0.55-0.62 0.42 0.40-0.45 27 F L 0.59 055-064 0.43 0.40-0.45 29 Kagoshima (6) F L 0.54 0.49-0.60 0.40 0.38-0.44 24 Misaki (8) M R 0.59 0.56-0.64 0.40 0.38-0.43 30 M L 0.60 0.57-0.64 0.40 0.37-0.44 36 F R 0.54 0.51-0.61 0.39 0.36-0.43 42 F L 0.55 0.52-0.61 0.40 0.37-0.44 46 Amami Is. (17) M R 0.59 0.55-0.64 0.40 0.37-0.43 30 M L 0.59 0.56-0.64 0.41 0.37-0.43 29 F R 0.54 0.49-0.58 0.38 0.35-0.41 58 F L 0.54 0.50-0.59 0.39 0.35-0.43 64 Loxoconcha sp. Hanai, 1961, p. 371, text-fig. 12, figs. 4a, b; Igo and Ikeya, 1971, p. 204, fig. 13. Loxoconcha sp. A. Ishizaki, 1968, p. 34, pl. 7, figs. 4, 5; Ishizaki, 1971, p. 88, pl. 3, fig. 16. ? Loxoconcha japonica Ishizaki. Hu, 1979, p. 69-70, pl. 2, figs. 32-37, text-fig. 8; Hu, 1984, pl. 4, figs. 24-26; Cai, 1982, pl. 3, fig. 21. Non Loxoconcha japonica Ishizaki. Hu, 1981, pl. 3, figs. 1-4, 8, text-fig. 14; Hu, 1983, pl. 2, figs. 3, 4, 6; Hu, 1986, pl. 4, figs. 22, 28, 30, 31; Nohara and Ohshiro, 1992, fig. 6. Types.—Holotype, a male left valve, IGPS coll. cat. no. 90260; paratypes, a male right valve, IGPS coll. cat. no. 90261, a female left valve, IGPS coll. cat. no. 90262. Type locality.—St. 303 (33°24.6'N. 133°26.5 E), Urano- uchi Bay, Kochi Prefecture, Shikoku, Japan, Recent, coarse sand, depth 25 m (x6 in Figure 12). _ Diagnosis.—Large sexual dimorphism, in lateral view, male more elongate and highest more posteriorly than the other three species described here from the L. japonica group. Carapace subrhomboidal in lateral view. Dorsal margin straight and sloped toward anterior in male, arched dorsally in female; anterior margin with an oblique infracurvature; ventral margin concave at mid-anterior portion; posterior margin broadly rounded at posteroventral portion. No prominent caudal process. In dorsal view, carapace diamond-shaped, often wedge-shaped in some fe- males. In posterior view, carapace generally elliptical, often egg-shaped in female. Ornamentation consists of concentrically arranged reticulation. Boot-shaped male copulatory organ has trapezoidal basal capsule, triangular distal lobe and basally inflated L-shaped ductus ejaculatorius. Dimensions.—Length and height of adult males and fe- Migration and speciation of Loxoconcha 279 |Sutteu: x ee + Y?/ Le =1 Misaki: X / (0.048) + Y/(0.060f = 1 (Kagoshima: X (0.0587 + Y?/ (0.078) = 1 Amami-o-shima: X/ (0.056) + Y7/ (0.084) = 1 0.6 Kagoshima(o) 0.3 0.5 0.6 X (mm) Figure 14. Geographic variation in posterior view of females of Loxoconcha japonica Ishizaki, 1968. Symbols refer to Suttsu popu- lation (open circles; n = 29), Misaki population (open triangles; n = 76), Kagoshima population (open squares; n = 24) and Amami-o- shima population (solid squares; n = 63). Plot of the distance from the base of ventral margin to the point on the marginal line of the maximum width (yl)/height (y2) on the posterior view of left valve (Y = yl/y2) versus length in the lateral view (X), with series of rejec- tion ellipses with 95% confidence intervals. males from the sample nos. 1, 6, 8 and 17 are listed in Table 2. Occurrences.—Fossil (Figure 11): Early Pliocene Maja Formation from Kume Island; Pliocene Sawane Formation from Sado Island; Late Pliocene Yonabaru Formation from Okinawa Island; Pleistocene formations and Holocene de- posits and boring core samples from Honshu to Cheju Island, southern Taiwan and Hong Kong. Recent (Figure 12): Japan (Hokkaido-Iriomote Island), southern coast of Korean Peninsula and Hong Kong. Remarks.—Some specimens from Recent material from the Ryukyus and fossils from the Ryukyus to Taiwan, have an alate ridge on the posteroventral area (see Ruan and Hao, 1988, pl. 57, fig. 13). The alate ridge is especially developed in southern female specimens with an egg- shaped outline in posterior view (Figure 14); this ridge is not developed in males. L. impressa reported by Kajiyama (1913) belongs to this species, based on carapace outline, surface ornamentation and the shape of the male copulatory organ. In the illustration of the male copulatory organ by Okubo (1980) it appears that the distal part of the ductus ejaculatorius extends beyond from the illustrated figure. However, we think that his specimen has been crushed and modified in shape. Loxoconcha shanhaiensis Hu, 1981 Figures 4.1, 4.2, 4.5; 5B, 5b; 6; 7B; 9.3, 9.4 Loxoconcha shanhaiensis Hu, 1981, p. 76, 77, pl. 3, figs. 5, 9, 11, text-figs. 13a, b; Hu, 1982, p. 180, 182, pl. 2, fig. 23; Hu, 1984, pl. 4, figs. 21-23, 27. Loxoconcha japonica Ishizaki. Hu, 1981, pl. 3, figs. 1-4, 8, text- fig. 14; Hu, 1983, pl. 2, figs. 3, 4, 6; Hu, 1986, pl. 4, figs. 22, 28, 30, 31; Nohara and Ohshiro, 1992, fig. 6. Types. — Holotype, TNUM. 4148; paratypes, TNUM. 4151, 4153 and 4150. Type locality.—The west margin of the Hengchun Table land, near Shanhai-li, 80-90 m above sea level, about 3 km west of Hengchun City, southern Taiwan (E in Figure 11). Diagnosis.—In lateral view, carapace subtrapezoidal and ornamented by concentric coarse reticulations. Boot- shaped male copulatory organ has trapezoidal basal capsule, subtriangular distal lobe, a shoehorn-shaped ductus ejaculatorius and a triangular clasping apparatus. Description. — Carapace: Strong sexual dimorphism. Carapace subtrapezoidal, highest at posterior cardinal angle in lateral view. Dorsal margin straight and sloped toward anterior; anterior margin with an oblique curvature and well developed denticulations; ventral margin straight; posterior margin with broad flat zone, broadly rounded in posteroventral area, with several strong spines. Short but prominent caudal process. In dorsal view, carapace wedge-shaped with maximum width about one-third of length from posterior end. Ornamentation consists of con- centrically arranged coarse reticulation. Prominent alate ridge developed in posteroventral area extended toward posterior. Pore system: (a) Lateral (sieve-type) pore sys- tem. 67 pores distributed on each valve in adult speci- mens. (b) Marginal pore system includes 16 pores (Figure 5b). Hinge (Figure 4.5a, b): Gongylodont. Hinge-line nearly straight. In left valve, anterior element is a downturned claw, median element has 39-42 teeth, and posterior element is a ball-like knob. The hinge of the right valve is complementary. Muscle scars (Figure 4.5a, b): Row of 4 adductor muscle scars curved anteriorly at in- side of median to slightly anterior of ventromedian of cara- pace. The upper of the two middle ones elliptical with hollows at middle, the other three scars bean-shaped. Elliptical frontal scar inclines anteroventrally in front of middle two scars. Two divided mandibular scars in front 280 of lowest adductor muscle scars. Fulcral point absent. Marginal infoldment (Figure 5b): Widest in anteroventral region, twisted in middle of ventral region and narrowed posterodorsally. Appendages: Antennule (Figure 6A). Five segments (there are six segments, but 4th and 5th are fused). Length ratio between distal segments is 26:19:8:29:19. Costae well developed in 2nd, 3rd and 4th segments. Second segment has numerous short hairs on the anterior margin and a short seta on the posterior margin. Third segment has a short seta on the anterior distal end. Fourth segment has two short and three long setae. Fifth segment with four long setae on the distal end. Antenna (Figure 6B): Four articulated segments (there are five seg- ments actually, but the 3rd and 4th are fused). Length ratio between distal segments is 26:11:46:4. Costae well developed, especially broad in the anterior margin of 3rd segment. Second segment has a long two-segmented exopodite and a seta on the posterior margin. Third seg- ment has a pair of unequal long setae and numerous hairs on the anterior margin one-sixth of the distance from the proximal end. Along the posterior margin of the 3rd seg- ment, three unequal-sized long setae and numerous hairs are developed in the middle of the ledge and one-third of the distance from the distal end. Furthermore, the third segment bears a seta on the posterior distal end. Fourth segment has two very well developed terminal claws with numerous serrations. Mandible (Figure 6C): Five- segmented. Length ratio between two propodite segments and three endopodite segments is 25+: 16:8:12:5. Basal segment (coxa) with eight teeth and a seta on anterior distal margin. Second segment of protopodite (basis) bears an exopodite reduced to a seta. First and 2nd segments of endopodite almost fused. First segment of endopodite with two long setae on the ventral distal end. Second seg- ment of endopodite with a pair of setae on the proximal and ventral distal ends, respectively. Furthermore, the 2nd segment has two setae on the anterior dorsal margin and a seta on the anterior distal margin. Third segment of endopodite with three pairs of setae on the distal end. Maxilla (Figure 6D): Extremely thin branchial plate (exopodite) with 16 setae. Basal segment bears a palp and three masticatory processes. Palp indistinctly two- segmented. The proximal segment bears 4 setae on its an- terior distal end. Distal segment with three setae on the distal end and one seta on the ledge in the posterior proxi- mal end. Outer, middle and inner masticatory processes bear 5, 4 and 5 setae, respectively, on each distal end. Thoracic legs (Figure 6E, F and G): All three legs are 4- segmented, similar in shape. Length ratio between distal segments is 24:20:8:13 in 3rd thoracic leg. Costae devel- oped on both margins. First segment having a seta on the anterior proximal end and two setae on the anterior proxi- mal end. The segment has a seta on the posterior proximal Gengo Tanaka and Noriyuki Ikeya Table 3. Measurements of valve of Loxoconcha shanhaiensis Hu, 1981 from sample nos. 17 and 20. Abbreviations same as Table 2. Length (mm) Height (mm) Sample (No.) Sex Valve Av. OR Av. OR Amami Is. (17) M R 0.48 0.45-0.51 0.33 0.31-0.37 29 M L 0.49 0.46-0.54 0.33 0.31-0.36 27 F R 0.48 0.46-0.52 0.34 0.32-0.36 26 F L 0.48 0.44-0.53 0.34 0.31-0.37 42 Okinawa Is. (20) M L 0.50 0.44-0.52 0.33 0.32-0.34 12 F L 0.49 0.46-0.53 0.34 0.32-0.38 40 end. Second segment bearing numerous hairs along the anterior margin and a seta on the anterior distal end. Third and 4th segments bearing numerous hairs along the anterior margin. Copulatory organ (Figure 7B): The basal cap- sule, with costae in the margin, is trapezoidal. A large subtriangular distal lobe and a small clasping apparatus are developed on the distal end of the basal capsule. Small shoehorn-shaped ductus ejaculatorius. Dimensions.—Length and height of adult males and fe- males from the sample nos. 17 and 20 are given in Table 3. Occurrences.—Fossil (Figure 11): Middle Pleistocene Shimo-jiro Formation from Okino-erabu Island; Late Pleistocene Tungshiao Formation and Hengchun Limestone from Taiwan. Recent (Figure 12): Ryukyus (Amami Island to Iriomote Island), Taiwan and Hainan Island. Remarks. — Specimens reported by Hu (1981, 1983, 1986) and Nohara and Ohshiro (1992) as L. japonica have coarse reticulation, straight dorsal margin sloped toward the anterior, posterior margin with broad flat zone and several strongly developed spines, so these specimens are identi- fied as L. shanhaiensis. Loxoconcha tumulosa (Hu, 1979) Figures 4.3, 4.4, 4.6; 5C, 5c; 9.5, 9.6 Loxocorniculum tumulosum Hu, 1979, p. 71, 72, pl. 2, figs. 17, 21, 22, 26, 27, 30, 31, text-fig. 10. Loxoconcha tumulosa (Hu). Hu, 1981, p. 78, pl. 3, figs. 6, 7; Hu, 1984, pl. 4, figs. 17, 18, 20; Zhao er al., 1985, pl. 20, fig. 11; Gou, 1990, p. 25, pl. 3, figs. 45-47. Loxoconcha alata Brady. Guha, 1968, p. 61, pl. 4, figs. 5, 13. Loxoconcha heronislandensis Hartmann. Hartmann, 1984, p. 128, pl. 7, figs. 1-6, text-figs. 47, 48; Whatley and Zhao, 1987, p. 350, pl. 5, fig. 12; Behrens, 1991, pl. 5, figs. 5, 6. Loxoconcha sp. Hartmann and Hartmann, 1978, pl. 10, fig. 6. Non Loxoconcha tumulosa (Hu). Zhao and Wang, 1988, pl. 2, fig. 27. Types.—Holotype, TUM. 4033; paratypes, TUM. 4034- 4036, 4065, 4066. Type locality.—A road cut from Hengchun to Oluanpi, 15-20 m above sea level, about 1 km east of Nanwan, Migration and speciation of Loxoconcha 281 Table 4. Measurements of valve of Loxoconcha tumulosa (Hu, 1979) from sample no. 23. Abbreviations same as Table 2. Length (mm) Height (mm) Sample (No.) Sex Valve Av. OR Av. OR Taiwan (23) F R 0.51 0.50-0.53 0.33 0.33-0.34 10 F L 0.52 0.50-0.54 0.35 0.34-036 7 Pingtung Prefecture, southern Taiwan (D in Figure 11). Diagnosis.—Large sexual dimorphism; in lateral view, male more elongate. Carapace rhomboidal in lateral view. Dorsal and ventral margins nearly parallel; anterior margin with an oblique infracurvature, and developed denticulations; posterior margin broadly rounded in posteroventral area. Prominent caudal process. In dorsal view, carapace wedge-shaped. In posterior view, carapace egg-shaped. Ornamentation consists of very coarse oncentrically arranged reticulation. Prominent alate ridge developed at postero-ventral area, and protuberance devel- oped in posterodorsal area. Dimensions.—Length and height of adult males and fe- males from the locality sample no. 23 is listed in Table 4. Occurrences.—Fossil (Figure 11): Late Miocene Round Chalk and Silt Formation, Pliocene Guiter Formation from the Andaman Islands of the Indian Ocean and Late Pleistocene Hengchun Limestone from Taiwan. Recent (Figure 12): Ryukyus (Tokuno-shima to Okinawa), Taiwan, Hainan, Cebu Island, Lizard Island, Guam, Truk, Marshall Islands, Gilbert Islands, Samoa and Tuamotu Islands from Southwest Pacific. Remarks.—Specimens reported by Guha (1968) from the Late Miocene and the Pliocene sediments of Interview Island and Guiter Island as L. alata are identified as L. tumulosa. L. heronislandensis reported by Behrens (1991) also belongs to this species. A specimen reported by Zhao and Wang (1988) as L. tumulosa differs from this species, because it has a protruded anterior margin and does not have a posterodorsal protuberance. Loxoconcha lilljeborgii Brady, 1868 Figures 3.4, 3.5, 3.7; 5D, 5d; 7C; 9.7, 9.8 Loxoconcha lilljeborgii Brady, 1868, p. 183, pl. 13, figs. 11-15; Mostafawi, 1992, p. 151, pl. 5, fig. 102. Loxoconcha lilljeborgii Brady? Whatley and Zhao, 1987, p. 351, pl. 5, fig. 13. Loxoconcha lilljeborchi Brady. Keij, 1954, p. 358, pl. 3, fig. 4; Guha, 1968, p. 61, pl. 4, fig. 20; Gramann, 1975, pl. 5, figs. 6-8; Zhao et al., 1985, pl. 20, fig. 12; Zhao and Wang, 1988, pl. 2, fig. 26. Loxoconcha georgei Hartmann and Hartmann, 1978, p. 105, pl. 9, figs. 15, 16, text-figs. 259-268, (non) pl. 9, figs. 13, 14; Howe and Mckenzie, 1989, p. 24, figs. 8, 84, 85, 154; Table 5. Measurements of valve of Loxoconcha lilljeborgii Brady, 1868 from sample no. 17. Abbreviations same as Table 2. Length (mm) Height (mm) Sample (No.) Sex Valve Av. OR Av. OR Amami Is. (17) M R 0.51 0.47-0.54 0.34 0.32-0.36 78 M L 0.52 0.49-0.55 0.34 0.32-0.36 69 F R 0.50 0.46-0.54 0.34 0.32-0.39 95 F L 0.50 0.45-0.54 0.35 0.31-0.37 97 Behrens, 1991, p. 116, 117, pl. 4, figs. 6-9. Loxoconcha broomensis Hartmann and Hartmann, 1978, p. 106, pl. 10, fig. 1, text-figs. 272, 279, (non) pl. 10, figs. 2-4, text- figs. 269, 280. Loxocorniculum sp. 1, Tabuki et al., 1987, pl. 2, fig. 11; Tabuki and Nohara, 1990, pl. 2, fig. 11; Tabuki, 1992, pl. 1, fig. 15. Loxocorniculum sp. A. Tabuki and Nohara, 1988, pl. 1, figs. 13, 14. Loxocorniculum cf. (Loxoconcha) georgei Hartmann. and Nohara, 1995, fig. 4-8. Loxocorniculum georgei (Hartmann). figs. 43, 44. Tabuki Gou, 1990, p. 26, pl. 3, Types.—Not defined. Type locality.—Mauritius, Indian Ocean (a in Figure 12). Diagnosis.—Strong sexual dimorphism; in lateral view, male more elongate. Carapace subrhomboidal in lateral view. Dorsal margin nearly straight in male, arched dor- sally in female; anterior margin with an oblique infracurvature; ventral margin concaved in mid-anterior area; posterior margin broadly rounded in posteroventral area. Caudal process not prominent. In dorsal view, carapace elongate arrowhead-shaped. In posterior view, egg-shaped. Ornamentation consists of concentrically ar- ranged oblong pits. Prominent protuberance developed in posterodorsal area. Pear-shaped male copulatory organ has inflated trapezoidal basal capsule, subtriangular distal lobe, a leaf-shaped clasping apparatus and elongate ductus ejaculatorius. Dimensions.—Length and height of adult males and fe- males from the sample No. 17 is given in Table 5. Occurrences.—Fossil (Figure 11): Late Miocene Round Chalk and Silt Formation, Pliocene Guiter Formation from the Andaman Islands of the Indian Ocean, and Late Pleistocene Hengchun Limestone from Taiwan. Recent (Figure 12): Ryukyus (Tokuno-shima to Okinawa), Taiwan, Hainan, and Lizard Island from Southwest Pacific. Remarks.— Specimens reported from the Ryukyus as Loxocorniculum sp. 1 (by Tabuki et al., 1987; Tabuki and Nohara, 1990; Tabuki, 1992), Loxocorniculum sp. A (by Tabuki and Nohara, 1988) and Loxocorniculum cf. (Loxoconcha) georgei (Tabuki and Nohara, 1995) are iden- tified as L. lilljeborgii, with its carapace outline, concentri- 282 Gengo Tanaka and Noriyuki Ikeya cally arranged oblong pits and postero-dorsal alate ridge. Hartmann and Hartmann (1978) described Loxoconcha georgei as a new species, and figured carapaces of both sexes and male soft parts, but a type specimen was not des- ignated. Judging from the carapace ornamentation, we think the figured male and female specimens belong to dif- ferent species. The male specimens we identify as L. lilljeborgii, with its concentrically arranged oblong pits, nearly straight dorsal margin, developed posterodorsal alate ridge and identically shaped of male copulatory organ. On the other hand, the female specimens are Loxoconcha broomensis, which was described in the same paper. This specimen has two strong anterior ridges. Carapaces of both sexes and the male soft parts of L. broomensis were also figured by Hartmann and Hartmann (1978), but a type specimen was not designated. Judging from the carapace outline and ornamentation, the female specimen should be identified as L. lilljeborgii. Acknowledgements We wish to express our sincere thanks to T. M. Cronin (U. S. Geological Survey) for his critical readings of the manuscript, and to A. Tsukagoshi (Shizuoka University) for his valuable discussions. We are also greatly indebted to H. Ujiié (Takushoku University) and T. Ono (Ryukyu University) for kindly loaning many Recent marine sam- ples that they collected from the Ryukyus. T. Kamiya (Kanazawa University) gave us living specimens from Misaki, Kanagawa Prefecture. T.-Y. Huang (Geological Survey of Taiwan) encouraged and helped us in the course of sampling in Taiwan. Q.-H. Zhao (Tongji University), B.-C. Zhou (Shanghai Museum) R. M. Ross (Paleon- tological Research Institution, New York) and T. Kase (National Science Museum, Tokyo) gave us much informa- tion about Loxoconcha in the Southwest Pacific. References Ahmad, M., Neale, J.W. and Siddiqui, Q.A., 1991: Tertiary Ostracoda from the Lindi area, Tanzania. Bulletin of the British Museum (Natural History), Geology, Supplement, vol. 46, no. 2, p. 175-270, pls. 1-35. Athersuch, J. and Horne, D.J., 1984: A review of some European genera of the family Loxoconchidae (Crustacea: Ostracoda). Zoological Journal of the Linnean Society, vol. 81, p. 1-22. Baird, W., 1850: 2. Description of a new crustacean. 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Bulletin of College of Education, University of the Ryukyus, no. 31, pt. 2, p. 323-335, pls. 1-2. (in Japanese with English ab- stract) Tabuki, R. and Nohara, T., 1988: Preliminary study on the ecology Gengo Tanaka and Noriyuki Ikeya Tabuki, R. and Nohara, T., 1990: The Ostracoda of the Sekisei-sho area, Ryukyu Islands, Japan: a preliminary report on the ostracods from coral reefs in the Ryukyu Islands. Jn, Whatley, R. and Maybury, C. eds., Ostracoda and Global Events, p. 365-377, pls. 1-2. Chapman and Hall, London. Tabuki, R. and Nohara, T., 1995: Seasonal distribution of intertidal ostracodes on gravels from the moat behind a coral reef off Sesoko Island, Ryukyu Islands, Japan. In, Riha, J. ed., Ostracoda and Biostratigraphy, p. 343-349. Balkema, Rotterdam. Tsukagoshi, A. and Kamiya, T., 1996: Heterochrony of the ostracod hingement and its significance for taxonomy. Biological Journal of the Linnean Society, vol. 57, p. 343-370. Ujiié, H., 1986: The Bottom of the Sea of the Ryukyu Island Arc. Sediments and Geology, 120 p. Shinsei-tosho, Naha. (in Japanese) Ujiié, H. and Nakamura, T., 1996: The Kuroshio current changes into Okinawa Trough after the last glacial period. Earth Monthly (Gekkan Chikyu), vol. 18, no. 8, p. 524-530. (in Japanese) Wang, P.-X., Zhang, J.-J., Zhao, Q.-H., Min, Q.-B., Bian, Y.-H., Zheng, L.-F., Cheng, X.-R. and Chen, R.-H., 1988: Foraminifera and Ostracoda in bottom sediments of the East China Sea, p. 1-438, pls. 1-58. Ocean Press, Beijing. (in Chinese with English abstract) Wang, Q.-Q. and Zhang, L.-F., 1987: Holocene Ostracoda fauna and paleoenvironment in the sea region around Hong Kong. Acta Oceanologica Sinica, vol. 6, p. 281-291, pls. 1-2. Whatley, R. and Zhao, Q.-H., 1987: Recent Ostracoda of the Malacca Straits, Part 1. Revista Espanola de Micropaleon- tologia, vol. 19, no. 3, p. 327-366, pls. 1-5. Yajima, M., 1988: Preliminary notes on the Japanese Miocene Ostracoda. Jn, Hanai, T., Ikeya, N. and Ishizaki, K. eds., Evolutionary Biology of Ostracoda, its Fundamentals and Applications, p. 1073-1085, pls. 1-3. Kodansha, Tokyo. Yamane, K., 1998: Recent ostracode assemblages from Hiuchi-nada Bay, Seto Inland Sea of Japan. Bulletin of the Ehime Prefectural Science Museum, no. 3, p. 19-59, pls. 1-12. (in Japanese with English abstract) Yasuhara, M. and Irizuki, T., 2001: Recent Ostracoda from the northeastern part of Osaka Bay, southwestern Japan. Journal of Geosciences, Osaka City University, vol. 44, art. 4, p. 57-95, pls. 1-12. Zhao, Q.-H., Wang, P.-X. and Zhang, Q.-L., 1985: Ostracoda in bot- tom sediments of the South China Sea off Guangdong Province, China: their taxonomy and distribution. Jn, Wang, P.-X. et al. eds., Marine Micropaleontology of China, p. 196-217, pls. 19-23. China Ocean Press, Beijing. Zhao, Q.-H. and Wang. P.-X., 1988: Distribution of Modern Ostracoda in the Shelf Seas off China. Jn, Hanai, T., Ikeya, N. and Ishizaki, K. eds., Evolutionary Biology of Ostracoda, its Fundamentals and Applications, p. 805-821, pls. 1-2. Kodansha, Tokyo. Note added in proof.—After the acceptance of the manuscript, T. of ostracods from the moat of a coral reef off Sesoko Island, Okinawa, Japan. In, Hanai, T., Ikeya, N. and Ishizaki, K. eds., Evolutionary Biology of Ostracoda, its Fundamentals and Applications, p. 429-437, pls. 1-2. Kodansha, Tokyo. Kase (National Science Museum, Tokyo) kindly provided us specimens of Loxoconcha lilljeborgii from the Tartaro Formation (Late Miocene) of Luzon Island, Philippines. The fossil record of L. lilljeborgii in East Asia, therefore, dates back from the Pleistocene to the Late Miocene. Paleontological Research, vol. 6, no. 3, pp. 285-297, September 30, 2002 © by the Palaeontological Society of Japan Middle Permian (Guadalupian) brachiopods from the Xiujimgingi area, Inner Mongolia, northeast China, and their palaeobiogeographical and palaeogeographical significance GUANG R. SHI', SHUZHONG SHEN’ AND JUN-ICHI TAZAWA’ ‘School of Ecology and Environment, Deakin University, Melbourne Campus, 221 Burwood Highway, Burwood, Victoria 3125, Australia (e-mail: grshi@deakin.edu.au) *Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing, Jiangsu Province 210008, China (e-mail: szshen@nigpas.ac.cn) ‘Department of Geology, Faculty of Science, Niigata University, Niigata, 950-2181, Japan (e-mail: tazawa@ geo.sc.niigata-u.ac.jp) Received December 12, 2001; Revised manuscript accepted June 11, 2002 Abstract. A small brachiopod fauna is described from the lower part of the Xiujimqingi Formation of the Xiujimgingi area in central-east Inner Mongolia, northeast China. The age of this fauna is regarded as Wordian (Middle Guadalupian, Middle Permian) by comparison with a similar brachiopod fauna from the Zhesi area of central Inner Mongolia, and by constraints from fusulinaceans associated with the Zhesi fauna. The Xiujimgingi fauna is typical of mixed Boreal/Palaeoequatorial Middle Permian brachiopod faunas of East Asia. The mixed nature of these faunas is interpreted to have resulted from the combined effects of a middle palaeolatitudinal position, intensified plate convergence between Sino-Korea and Mongolia, and sea surface current connections with both the Arctic Sea in the north and eastern Palaeo-Tethys to the south. Possible Kaninospirifer is reported for the first time from China. Key words: brachiopods, Middle Permian, northeast China, palaeobiogeography, transitional fauna, Xiujimgingi Introduction Permian marine sedimentary rocks are common in Inner Mongolia and contain abundant and varied marine inverte- brate faunas. Generally, these faunas show a consistent palaeobiogeographical pattern, in that those from northern Inner Mongolia appear to be dominated by elements char- acteristic of the cool- to cold-water Boreal Realm, while faunas in central and southern Inner Mongolia tend to be more characteristic of the warm-water Palaeoequatorial Realm, but at the same time contain some taxa common to, or characteristic of, the Boreal or Gondwanan Realms (Tazawa, 1991; Shi et al, 1995; Shi and Zhan, 1996). As such, the Permian marine faunas of central and southern Inner Mongolia typify a transitional biogeographical zone between the Boreal Realm to the north and the Palaeoequatorial Realm to the south, as defined and dis- cussed by Shi et al. (1995). Despite their ubiquity and abundance in the Permian ma- rine sediments in Inner Mongolia and hence great signifi- cance for dating and correlation, only a few brachiopod faunas have been systematically described in detail. One of the better studied areas is the Xiujimqinqi area in cen- tral-eastern Inner Mongolia (Figure 1), where Permian brachiopods are common throughout the entire Lower and Middle Permian marine volcaniclastic, bioclastic and terrigenous sediments, well over 4,000 m in total thickness (Figure 2). Permian brachiopod faunas from various lo- calities of this area have been studied by Lee et al. (1982, 1983, 1985) and Liu and Waterhouse (1985), and have fur- nished the basic premise for the Permian biostratigraphical zonation schemes of this area (Lee er al., 1982, 1983; Liu and Waterhouse, 1985; BGMNG, 1991). However, with the exception of Liu and Waterhouse’s (1985) work, which described five brachiopod assemblages but did not give specific details on the exact location of 286 Guang R. Shi et al. © Xingmiao Dong Ujimgingi Index Map 0 720 KM p Hogengshan Figure 1. Map showing the study area, as well as the Zhesi area also referred to in the text. The enlarged map shows the detailed location of the area of study (Yuejin Coal Mine) in the Xiujimgingi area. The shaded area in the index map is the Nei Mongol (Inner Mongolia) Autonomous Region. their measured sections other than the general Xiujimgingi area, the other earlier studies (Lee et al., 1982, 1983, 1985) dealt only with certain taxa instead of the entire faunas. These latter investigations demonstrate that there are at least 10 relatively well exposed sections/localities in the general Xiujimgingi area where Permian marine sequences with abundant brachiopods crop out. Lee er al. (1982) provided a detailed list of all the Permian brachiopod spe- cies then known to occur in this area, which they used as the basis for the erection of their brachiopod-based stratigraphical assemblages. The present study is based on a small collection from the Yuejin Coal Mine, about 10 km southwest of Xiujimgingi Township (Figure 1). This collection was originally made by the officers of the Bureau of Geology and Mineral Resources of Nei Mongol (Inner Mongolia) during the 1950s-1970s and was entrusted to Zhan Li-Pei, Chinese Academy of Geological Sciences (Beijing), for age deter- mination. Zhan Li-Pei subsequently fulfilled this request by providing a list of his identified species and a broad age indication [“Early Permian”, which, in terms of Jin’s et al. (1997) proposed Permian timescale, includes both Early and Middle Permian]. Up to the present, this collection has not yet been systematically described. As will be documented below, this collection provides additional and new records to what is currently known about the Middle Permian brachiopod faunas of the Xiujimgingi area. Moreover, this collection also affords important material to document Kaninospirifer from China for the first time. Specimens described and illustrated in this paper are housed in the Museum of Victoria, Melbourne, Australia, with registration numbers prefixed with NMVP. Stratigraphy Over the last 2 decades, there has been a significant in- crease of lithostratigraphical names applied to the Permian rocks of the Xiujimgingi area. In the two latest attempts to rationalize the stratigraphical nomenclature for the Permian System for the broad Inner Mongolian province (BGMNM, 1991; Jin et al., 2000), many of the previously used names have been abandoned or treated as synonyms of others. In this study, we follow the stratigraphical framework recommended by BGMNM (1991) for the Xiujimgingi area, which was also adopted in Jin et al. (2000). According to this scheme, the Permian sequence in the Xiujimqingi area comprises, in ascending order, the Gegenaobao, Xiujimqinqi and Linxi formations (Figure 2). The Gegenaobao Formation is a sequence of acidic to inter- mediate volcanics, volcaniclastics and a minor amount of carbonate rocks. Both shallow marine and nonmarine fos- sils occur in this formation, indicating a volcanically active continental marginal marine setting. Among the marine fossils, brachiopods are most common and notably include species of Jakutoproductus and Licharewia (or Tumarinia). The cooccurrence of these two genera in this formation would indicate a relatively broad age range for the forma- tion, from probably Artinskian (Early Permian) to as high as Roadian (early Middle Permian). The Gegenaobao Formation in the Xiujimgingi area is conformably overlain by the Xiujimgingi Formation. The latter is dominated by andesite in the lower part, limestone and mudstone in the middle part, and siltstone in the upper part (Figure 2). Brachiopods occur throughout the forma- tion but are mainly concentrated in several major horizons, each of which appears to form a distinct assemblage (Figure 2). By reference to the lithology and overall spe- cies composition, the brachiopod collection described below is considered to have come from the lower portion of the middle part of the formation. Plant fossils have also been reported from the siltstone beds in the upper part (BGMNM, 1991). As will be detailed below, the age of this formation is regarded as Wordian by correlation with faunas elsewhere. Upwards, the Xiujimgingi Formation grades to sandstone and conglomerate of the Linxi Formation without distinct disconcordance. The latter contains abundant Late Permian (Lopingian) mixed Cathaysia/Angara type flora Permian brachiopods from Xiujimgingi 287 Xiujimgingi area EI un gs => Te ? Fallaxoproductus- Neospirifer Assemblage Licharewia- Neospirifer Assemblage Richthefonia-Leptodus- Waagenoconcha- Enteletes Assemblage Liosotella Assemblage Spiriferella- Yakovlevia Assemblage 0 I \ Xiujimgingi Formation (>2237 m) Ww Yakovlevia- Anidanthus Assemblage Zhesi Formation (1219 m) + Fault contact Spiriferella- Kochiproductus- = = Yakovlevia Assemblage n ™ oO’ A ~— = = = Monodiexodina © = fauna / en =A 8) = © ar oo = > =) S El mM 5 ES & Jakutoproductus sp. © 200 m = E = ee © & Licharewia sp. BE = ne 5 or Tumarinia sp. ge ‘aa re Ein D Le lms 0 es à Volcanic Shale or Top or base Andesite [v2] Conglomerate = mudstone DA] not complete Chert or Rhyolite Siltstone with Brachiopod 7 _ cherty mudstone coal seams horizons Andesitic Micnte or ; Ar porphynte muddy limestone E =] Siltstone [o 9] Conglomerate “yee Sandstone with Volcanic Bioclastic [ ] bol] Prec FRÈRE Sandstone conglomerate Figure 2. Permian stratigraphical sequences of the Xiujimgingi and Zhesi areas, Inner Mongolia, northeast China. The stratigraphic columns and biozones are based on data from BGMNM (1991). 288 Guang R. Shi et al. (Zhang, 1988). Correlation and age The present collection comprises 10 species, of which several are species indeterminate and two genera and spe- cies indeterminate. At first glance, the assemblage cannot be readily correlated with any of the five assemblages originally established by Lee et al. (1982, 1983, 1985) and elaborated by BGMNM (1991) (see Figure 2) because of the lack of key zonal species in our collection; neither can it be matched with certainty with any of the five Early and Middle Permian brachiopod assemblages recognized by Liu and Waterhouse (1985). The closest assemblage among the established schemes is the Spiriferella-Yakovlevia as- semblage of Lee et al. (1982), which occurs in the lower portion of the middle part of the Xiujimqingi Formation (Figure 2). This assemblage was originally recognized based on the brachiopod fauna from a limestone quarry about 7 km northwest of the present Yuejin Coal Mine (Lee et al., 1982), and is characterized by abundant occurrence of Spiriferella and Yakovlevia, the former being represented by two species and the latter by four (Lee et al., 1982). Other characteristic species of this assemblage include Liosotella septentrionalis (Tschernyshew), Marginifera gobiensis Chao, Paramarginifera zhesiensis Lee and Gu, Waagenoconcha permocarbonica Ustritskiy, W. xiugiensis Lee, Gu and Li, Strophalosia paradoxa Fredericks, S. pulchra Lee, Gu and Li, Linoproductus cora (d’Orbigny), Leptodus sp., Neospirifer xiujumgingiensis Lee, Gu and Li, N. ravana (Diener), N. moosakhailensis (Davidson), and Paeckelmanella laevis Lee and Gu. Although lacking many of these species, the present collection nevertheless con- tains relatively abundant Spiriferella and neospiriferids (Neospirifer and Kaninospirifer), hence suggesting a sig- nificant degree of correlation. On the other hand, we note that some other factors, for example, insufficient sampling in the present collection and/or localized specialization of biofacies, may have also contributed to the apparent differ- ence in species composition between the present collection and the Spiriferella-Yakovlevia assemblage. The age of the above Spiriferella-Yakovlevia assemblage has been considered to be either late Early Permian (Lee et al., 1982) or middle Early Permian (BGMNM, 1991) in the traditional twofold Permian chronostratigraphical timescale of China (e.g., Zhan and Li, 1984). A more spe- cific age determination for the Spiriferella-Yakovlevia as- semblage is possible by correlation with the classic Permian brachiopod faunas of the Zhesi area in central Mongolia (see index map in Figure 1 for location), where brachiopods are associated with fusulinaceans. Here, the Permian is divided into three formations: the Xilimiao Formation, Baogete Formation and Zhesi Formation, in as- cending order (BGMNM, 1991) (Figure 2). The brachio- pod-bearing horizons that are comparable with those of the Xiujimgingi area lie in the Baogete and Zhesi formations. Permian brachiopods are very rich in this area and have been the subject of two major monographical studies (Grabau, 1931; Duan and Li, 1985). According to them, the Permian brachiopods in this section can be divided into two broad assemblages: the Spiriferella-Kochiproductus- Yakovlevia assemblage (or SKY assemblage, as called by Duan and Li, 1985), followed by the Richthofenia- Leptodus-Enteletes assemblage (or RLE assemblage). Of these, the SKY assemblage is well correlated with the Spiriferella-Yakovlevia assemblage of the Xiujimgingi area as both assemblages contain abundant Boreal-type genera such as Neospirifer, Spiriferella and Yakovlevia, and are similarly characterized by an admixture of Boreal and Palaeoequatorial taxa. The RLE assemblage of the Zhesi area, on the other hand, is dominated by Palaeoequatorial or Cathaysian-type genera and bears no significant similari- ties with any of the Xiujimqinqi assemblages. The age of the SKY assemblage of the Zhesi section is well constrained by the associated fusulinaceans of the Monodiexodina sutchanica Zone in its lower part, and the fusulinaceans of the Codonofusiella Zone and corals of the Waggenophyllum-Wentzella Zone that directly and con- formably overly the SKY assemblage and are associated with the brachiopods of the RLE assemblage (Duan and Li, 1985; BGMNM, 1991) (Figure 2). The Monodiexodina sutchanica Zone is generally regarded as of early Midian or Wordian age (Kotlyar et al., 1999; Shi and Tazawa, 2001), and the Codonofusiella and Waagenophyllum-Wentzella zones of Capitanian age (Jin et al., 1997). Thus, the SKY assemblage can be safely assigned to the Wordian in age. This implies that the Spiriferella-Yakovlevia assemblage, and hence, by correlation, the present collection from the Yuejin Coal Mine under discussion, is also Wordian in age. Palaeobiogeographical and palaeogeographical implications In spite of its small species composition, the present col- lection demonstrates aspects of a mixed Boreal/Cathaysian palaeobiogeographical fauna. The cool-water Boreal as- pect of the fauna is represented by two characteristic north- ern Eurasian genera: Anemonaria and Kaninospirifer. Anemonaria is primarily restricted to the Arctic region (Arctic Russia, Spitsbergen, Greenland, and Arctic Canada) (Sarytcheva, 1977), although some occurrences from Australia (Briggs, 1998) and middle-latitudinal regions are also known, such as Japan (Tazawa and Niigata Pre- Tertiary Research Group, 1999; Tazawa, 2001) and the Russian Far East (Likharev and Kotlyar, 1978). The only exception to this essentially high-to middle-palaeolatitu- Permian brachiopods from Xiujimgingi 289 r— Continental shelves or — cratonic basins b = i i= [2] Occurrences of Kaninospirifer ‘© Occurrences of Anemonaria 10 1e — Se os a Occurrences of Compressoproductus 10 Occurrences of Echinauris | | | | À Warm-water currents (| | VA coié-vater currents Figure 3. the inferred palaeo-position (indicated by star) of Xiujimgingi during the Middle Permian (base map from Ziegler er al., 1998). SQ Realm — ino-Mongolian-Japanese \ Province \ Palaeo- equatorial Realm wy <— Sibumasu Province / Vic ae A Permian reconstruction map showing the distribution of Anemonaria, Compressoproductus, Echinauris, and Kaninospirifer, and Locations of the oc- currences of Anemonaria, Compressoproductus, Echinauris, and Kaninospirifer are as follows: 1, Kolyma Block, Russia; 2, northern Verkhoyansk, Russia; 3, Yukon Territory, Canada; 4 Sverdrup Basin, Canada; 5, Kanin Peninsula, Russia; 6, Pechora Basin, Russia; 8, Phosphoria Basin, western USA; 9, Xiujimgingi and adjacent areas in northeast China; 10, Texas, USA and central America; 11, SW Japan and South Primorye of Far Eastern Russia; 12, South Kitakami, northeast Japan; 12, South China 14, northwest Iran and Armenia; 15, Shan-Thai (Sibumasu) block; 16, Indochina; 17, southeast Pamir, Karakorum and central Afghanistan; 18, southern Tibet; 19 northwest Nepal, 20, Salt Range, Pakistan. Explanations of main tec- tonic blocks: Q, Qiangtang Block; I, Indochina Block; M, Mongolia Block; S, South China Block; SK, Sino-Korea Block; T, Shan-Thai (Sibumasu) Block. dinal distributional pattern is a record of the genus from Texas, southern U.S.A. (Cooper and Grant, 1969, 1975) and Venezuela (Hoover, 1981). These two “outlying” oc- currences may be explained by the possible effect of a California-type cold current that might have intermittently operated off the western coast of northern Pangea during the Permian, bringing cold-water Boreal faunal elements to palaeoequatorial Texas and South America (Shi, 1995; Shi and Tazawa, 2001). By contrast, the palaeogeographical distribution of Kaninospirifer is much more restricted, with occurrences known only from the northern part of the Russian Platform, Arctic Canada, Greenland, and Spitsbergen (Kalashnikov, 1996), Mongolia (Pavlova, 1991), northeast China (this re- port) and Japan (Tazawa, 2000; see discussion below) (Figure 3). The warm-water palaeoequatorial aspect of the Xiujimgingi brachiopod fauna is signaled by Compressoproductus and Echinauris. These two genera have essentially concordant palaeogeographical distribu- tions, with occurrences restricted to the Tethys and south- west U.S.A. and have never been recorded from either the Gondwanan Realm or the Boreal Realm proper (Figure 3). In addition to the four genera noted above, the palaeogeographical distribution of Spiriferella is also of great interest. Unlike Anemonaria, Kaninospirifer, Echinauris and Compressoproductus, which, as noted above, have either restricted high palaeolatitudinal Boreal occurrences or low palaeolatitudinal Tethyan occurrences, the palaeogeographical distribution of Spiriferella is typi- cally bipolar and bitemperate (terms as defined in Shi and Grunt, 2000), in that it occurred only in the middle and high palaeolatitudinal regions of both hemispheres (Shi and Grunt, 2000). The mixed nature of the Xiujimgingi brachiopod assem- blage, as outlined above, is consistent with several other Middle Permian brachiopod faunas reported from northeast China, southeast Mongolia, South Primorye of the Russian Far East, and Japan, as already summarized and discussed by Tazawa (1991), Shi et al. (1995) and Shi and Zhan (1996). A refined scenario to interpret the origin of these mixed Middle Permian brachiopod faunas has recently been put forth by Shi and Tazawa (2001). In this interpre- tation, it is suggested that all the mixed Middle Permian Guang R. Shi et al. 290 Permian brachiopods from Xiujimgingi faunas in eastern Asia (NE China, parts of Japan, Mongolia, and South Primorye of the Russian Far East) are referable to characterize the same single palaeobiogeo- graphical unit, the Sino-Mongolian-Japanese Province (= Inner Mongolia-Japanese Transitional Zone of Tazawa, 1991). This province has a distinct transitional biogeo- graphical nature characterized by intermingling genera typical of both the palaeoequatorial Cathaysian Province in the south and the Boreal Realm to the north. The origin of this biogeographical mixing, apparently limited to the Wordian interval, is thought to have resulted from the inter- play of three main factors: (1) a middle palaeolatitudinal position for the Sino-Mongolian-Japanese Province; (2) in- tensified plate convergence between the Sino-Korea and Mongolia blocks during the Permian; and (3) sea surface current connections with both the warm-water eastern Palaeo-Tethys to the south and the temperate to polar Arctic sea to the north (Figure 3). A middle palaeo- latitudinal position for the Sino-Mongolian-Japanese Province, estimated to be 25°-40° N, is suggested by the mixed nature of the faunas which, in analogy to modern latitude-dependent biogeographical zonation patterns (see Yin, 1989), would indicate a mesothermal setting compara- ble to a middle-latitudinal position or temperate zone. A phase of intensified plate convergence between Sino-Korea and Mongolia through the Permian, especially the Early and Middle Permian is assumed because this would have resulted in the shrinking and progressive shallowing of the Sino-Mongolian seaway that harbored the Sino-Mongolian- Japanese Province. This in turn would have facilitated and enhanced the intermingling of Boreal faunas that originally prevailed on the shelves of the Mongolian block and the eastern Palaeo-Tethyan faunas that dominated the northern shelves of the Sino-Korea block. The inferred sea surface current connections of the Sino-Mongolian-Japanese Province to both the Boreal Realm and the eastern Palaeo- Tethys is important because these currents would have brought their prospective faunal elements to the Sino- Mongolian seaway where they were eventually intermin- gled. Therefore, in light of these considerations we propose that the Xiujimqingi area was probably located within the eastern end of the Sino-Mongolian seaway, in an intermediate position between Sino-Korea and Mongolia 291 (Figure 3). Systematic palaeontology Order Chonetida Nalivkin, 1979 Suborder Chonetidina Muir-Wood, 1955 Superfamily Chonetoidea Bronn, 1862 Family Rugosochonetidae Muir-Wood, 1962 Rugosochonetidae gen. and sp. indet. Figure 4.1 Remarks.— An incomplete internal mould of a dorsal valve (NMV P308012) represents a species most likely of Rugosochonetidae in view of its prominent fold, finely papillose inner surface and about 20 coarse costellae each with scores of capillae. The specimen is badly worn, therefore the internal structures are not preserved, rendering even its generic status open. Order Productida Waagen, 1883 Suborder Productidina Waagen, 1883 Superfamily Productoidea Gray, 1840 Family Productellidae Schuchert in Schuchert and LeVene, 1929 Subfamily Marginiferinae Stehli, 1954 Genus Echinauris Muir-Wood and Cooper, 1960 Type species. — Echinauris lateralis Muir-Wood and Cooper, 1960. Echinauris sp. Figure 4.5 Remarks. — An incomplete ventral valve (NMV P308016) is referable to Echinauris. The ventral valve is more than 25 mm long, 29 mm wide, and more than 20 mm thick, has a moderately convex profile and is ornamented with numerous fine spine bases, but appears to have no evi- dent internal ridge. This specimen is much larger than E. jisuensis (Chao, 1927; also described and figured by Duan and Li, 1985, p. 112, pl. 35, figs. 7-13) from the Zhesi Formation in the Zhesi area of Inner Mongolia. + Figure 4. (King, 1931). 1. Rugosochonetidae gen. et sp. indet. Internal mold of a dorsal valve, NMV P308012, x2.5. 2. Ventral view of a ventral valve, NMV P308020, x2; 3, 7. Posterior and anterior views of a ventral valve, NMV P308017, x2; 4, 2-4, 6-8. Anemonaria sublaevis 8. Ventral and lateral views of a ventral valve, NMV P308018, x2; 6. Posterior view of a ventral valve, NMV P308019, x2. 5. Echinauris sp., ventral view of a ventral valve, NMV P308016, x1.3. x1.6. 1931). Ventral view of a ventral valve, NMV P308037. unless otherwise indicated. 20. Kaninospirifer sp. Ventral view of a ventral valve, NMV P308035. 9. Compressoproductus corniformis (Chao, 1927), ventral view of a ventral valve, NMV P308026, 10. Cancrinella? cancrini (de Verneuil, 1845), ventral view of a ventral valve, NMV P308024, x2. 11-13. Lateral, dorsal, and ventral views of a conjoined shell, NMV P308029; 14. Ventral view of a ventral valve, NMV P308030, x1.5. 15, 18, 21. Neospirifer sp. Anterior, dorsal, and ventral views of a conjoined shell, NMV P308036. 16. Ventral view of a ventral valve, NMV P308033; 17. Ventral view of a ventral valve, NMV P308034. 11-14. Spiriferella persaranae (Grabau, 16-17. Spiriferella keilhavii (von Buch, 1846). 19. Neospiriferinae gen. and sp. indet. All figures are natural size 292 Guang R. Shi er al. Subfamily Paucispiniferinae Muir-Wood and Cooper, 1960 Genus Anemonaria Cooper and Grant, 1969 Type species. —Marginifera sublaevis King, 1931. Anemonaria sublaevis (King, 1931) Figure 4.2-4.4, 4.6-4.8 Marginifera sublaevis King, 1931, p. 89, pl. 23, figs. 15a-c, ?16a, b, 19 (non figs. 13, 14). Anemonaria inflata Cooper and Grant, 1969, p. 8, pl. 5, figs. 28, 29. Anemonaria sublaevis (King). pl. 408, figs. 1-26. Cooper and Grant, 1975, p. 1103, Material. — Three conjoined shells (NMV P308017- 308019) and a nearly complete ventral valve (NMV P308020). Description.—Shell of medium size, subrectangular out- line, strongly concavo-convex in profile; widest at hinge; anterior margin slightly emarginated medially; ears alate and acute, triangular in shape, well demarcated from vis- ceral region. Ventral valve strongly but unevenly convex, strongly geniculated; umbonal region swollen; umbonal slopes sharply inclined; sulcus shallow and broad, originat- ing from anterior to umbo, becoming prominent on trail. Dorsal valve deeply concave; fold broad and round on trail. Surface of both valves largely smooth; occasionally with some inconspicuous costae near margin; halteroid spines in row overhanging usually smooth ears; spines rare on body and trail. Remarks.—King (1931) first named this species, but the type was selected by Cooper and Grant (1975). This spe- cies is characterized by subrectangular outline, broad and shallow sulcus, and small triangular ears. This species dif- fers from A. pseudohorrida (Wiman, 1914, p. 74, pl. 17, figs. 1-11) from the Kungurian to Guadalupian Kapp Starostin Formation of Spitsbergen and A. auriculata Shi and Waterhouse (1996, p. 68, pl. 6, figs. 10-28; text-figs. 22-24) from the Artinskian Jungle Creek Formation in the Yukon Territory of Canada by its deeper and broader sulcus. A. pinegensis (Likharev, 1931, p. 26, pl. 3, figs. 24, 25; Sarytcheva, 1977, p. 123, pl. 18, figs. 5-14) from the Kungurian strata in Kanin Peninsula, northwestern Russia, could be conspecific with the present species in terms of its outline, and shallow and broad sulcus, but ap- pears to have more subquadrate ears. Superfamily Linoproductoidea Stehli, 1954 Family Linoproductidae Stehli, 1954 Subfamily Linoproductidae Stehli, 1954 Genus Cancrinella Fredericks, 1928 Type species.—Productus cancrini de Verneuil, 1845. Cancrinella? cancrini (de Verneuil, 1845) Figure 4.10 Productus cancrini de Verneuil, 1845, p. 273, pl. 16, figs. 8a-c; pl. 18, fig. 7; Likharev, 1931, p. 319, pl. 1, figs. 11-13; Miloradovich, 1935, p. 131, pl. 5, figs. 4, 5. Cancrinella cancrini (de Verneuil). Sarytcheva and Sokolskaja, 1952, p. 112, pl. 20; Grigorjeva, 1962, p. 50, pl. 11, figs. 1-10; pl. 15, fig. 1; pl. 16, figs. 1, 2; Grigorjeva et al., 1977, p. 129, pl. 19, figs. 1-9, text-figs. 75, 76. Material.—A complete ventral valve (NMV P308024) and an incomplete external mould of a dorsal valve (NMV P308025). Description.—Shell small, subquadrate in outline, hinge slightly narrower than greatest width; with broadly rounded anterior and lateral margins; ventral visceral disc strongly convex, somewhat triangular; beak pointed; ears small; car- dinal extremities obtuse; umbonal slopes sharply inclined; sulcus absent; surface marked by strong concentric wrin- kles and fine costellae; costellae numbering 7 in 2 mm near the anterior margin; spines thin and delicate; spine bases elongated, widely scattered. Dorsal valve deeply concave; strongly geniculated; surface also with distinct wrinkles and fine costellae; spines unknown. Remarks.—The small size, subquadrate outline and very fine costellae of the present specimens are generally identi- cal with the type figured by de Verneuil (1845). However, the unknown dorsal spines renders the generic status of the present material open. Many previously recognized spe- cies of Cancrinella have been attributed to Costatumulus Waterhouse (see Archbold, 1993), which differs from Cancrinella in possessing dorsal spines. Therefore, it is also possible that the Xiujimqinqi specimens could belong to Costatumulus. Genus Compressoproductus Sarytcheva in Sarytcheva, Likharev and Sokolskaja, 1960 Type species.—Productus compressus Waagen, 1884. Compressoproductus corniformis (Chao, 1927) Figure 4.9 Striatifera compressa var. corniformis Chao, 1927, p. 101, pl. 15, figs. 6-9. Productus (Striatifera) var. corniformis Chao. 291, pl. 29, figs. 6-9. Compressoproductus compressa vat. corniformis (Chao). et al., 1964, p. 334, pl. 53, figs. 12, 13. Grabau, 1931, p. Wang Permian brachiopods from Xiujimgingi 295 Remarks. — The occurrence of this species in the Xiujimgingi collection is shown by a single specimen (NMV P308026). This species has been documented from the Zhesi Formation in Zhesi, Inner Mongolia, by Grabau (1931). The characteristic elongate outline, finely costellate surface and strongly laterally compressed nature of the shell of the present specimen fit very well with the type from the Longtan Formation in Guangxi, South China, as figured by Chao (1927). This species differs from all other species in the genus by the laterally compressed na- ture of its shell, hence warranting the recognition of Chao’s variety as a separate species. Order Spiriferida Waagen, 1883 Suborder Spiriferidina Waagen, 1883 Superfamily Spiriferoidea King, 1846 Family Spiriferellidae Waterhouse, 1968 Genus Spiriferella Tschernyschew, 1902 Type species. —Spirifer saranae de Verneuil, 1845. Spiriferella persaranae (Grabau, 1931) Figure 4.11-4.14 Spirifer persaranae Grabau, 1931, p. 156, pl. 19, fig. 4. Spiriferella persaranae Grabau. Wang et al., 1964, p. 595, pl. 114, figs. 15, 16; Li and Gu, 1976, p. 295, pl. 172, figs. 1-6; Li et al., 1980, p. 418, pl. 178, fig. 5; Duan and Li, 1985, p. 121, pl. 1, figs. 1-11, 17, 18. Material.—A slightly crushed conjoined shell (NMV P308029) and three incomplete ventral valves (NMV P308030-308032). Description.—Shell medium in size, elongate in outline, unequally biconvex in profile, hinge narrower than greatest width at slightly anterior to midvalve; ventral beak strongly incurved; interarea very high, strongly concave, delthyrium about one-third of the hinge line; beak ridges angular; ven- tral sulcus narrow and shallow, commencing from beak, with several inconspicuous costae; boundary costae coarser than other costae; each flank with 4-6 costae; costae com- monly bifurcating 1-2 times, producing some small costae beside the main costa; dorsal valve less convex than ventral valve; fold low, with a prominent median groove; each flank with 4-5 costae. Remarks.—S. saranae (de Verneuil, 1845, p. 169, pl. 6, fig. 15a, b) is closest to this species. The original descrip- tion of S. saranae by de Verneuil (1845) from the upper Artinskian of the Ufa River mentioned that this species is characterized by a high interarea, five to six smaller, equally spaced costae in the sulcus and a prominent median groove in the fold. S. persaranae differs from S. saranae in its more simple costae and less conspicuous and proba- bly fewer and smaller costae in the sulcus. S. praesaranae (Stepanov,1948, p. 43, pl. 10, figs. 3-8) is probably synonymous with the present species as indicated by their similar costation, size and outline, but it is from the Upper Carboniferous. Spiriferella keilhavii (von Buch, 1846) Figure 4.16, 4.17 Spirifer keilhavii von Buch, 1846, p. 74, pl. 1, figs. 2a, b: Frech, 1901, p. 499, pl. 57c, figs. 1b-c. Spirifer draschei Toula, 1875, p. 239, pl. 7, figs. 4a-c. Spirifer parryanus Toula, 1875, p. 232, pl. 7, figs. 8a-d. Spiriferella keilhavii (von Buch). Tschernyschew, 1902, p. 527, pl. 40, figs. 1-4; Wiman, 1914, p. 36, pl. 2, figs. 25-30, pl. 3, fig. 1; Tschernyschew and Stepanov, 1916, p. 79, pl. 11, figs. 2a-c, 3a-c; Frebold, 1931, p. 28, pl. 5, figs. 7-9; 1937, p. 46, pl. 11, fig. 9; Dunbar, 1955, p. 139, pl. 25, figs. 1-9; pl. 26, figs. 1-11; pl. 27, figs. 1-14; Gobbett, 1964, p. 154, pl. 20, fig. 7; Nelson and Johnson, 1968, p. 736, pl. 96, figs. 7, 8, 12; text-figs. 3e, 8a, 9, 13b; Brabb and Grant, 1971, p. 17, pl. 2, figs. 26-28, 34, 35; Duan and Li, 1985, p. 122, pl. 206 IL, Sy Se Spiriferella draschei (Toula). 11597, ?Spiriferella keilhavii (von Buch). Waterhouse and Waddington, 1982, p. 28, pl. 4, fig. 15; pl. 6, figs. 3-14; text-figs. 16e, 21, 19. Wiman (partim), 1914, p. 38, pl. 3, Remarks.—As noted by Likharev and Einor (1939, p. 218) and Dunbar (1955, p. 152), von Buch’s original figure of S. keilhavii is a drawing constructed from a number of specimens, two of which (a dorsal and a ventral) were later figured by Frech (1901, pl. 57c, figs. 1b-c). Likharev and Einor (1939) selected the dorsal valve of Frech’s figured material (Frech, 1901, pl. 57c, fig. 1b) as the ‘holotype’ (lectotype) of S. keilhavii on the ground that the features of the dorsal valve match better with von Buch’s original de- scription of the species. Since our material consists only of two ventral valves (NMV P308033, 308034), no com- parison can be made with the lectotype of the species, but the observed features of the ventral valves, especially the large and wide valves with a hinge line nearly as wide as the greatest shell width and strongly fasciculated costae, are characteristic of the ventral valve of S. keilhavii as figured by Tschernyschew (1902), Dunbar (1955) and Gobbett (1963). Spirifer parryanus Toula (1875) from Spitzbergen was erected based on several incomplete specimens, and has been referred to S. keilhavii (Dunbar, 1955, p. 145). Specimens figured by Waterhouse and Waddington (1982) from Yukon Territory of Canada have flat, coarse and unbranched costae and a relatively narrower hinge, suggest- 294 Guang R. Shi et al. ing that they are probably different from the type material of S. keilhavii as described and figured by Dunbar (1955, pl. 27, figs. 8, 9). Family Spiriferidae King, 1846 Subfamily Kaninospiriferinae Kalashnikov, 1996 Genus Kaninospirifer Kulikov and Stepanov in Stepanov et al., 1975 Types species.—Spirifer kaninensis Likharev, 1943. Remarks.—When proposing Kaninospiriferinae, Kalash- nikov (1996) included two genera in this new subfamily: Kaninospirifer and Imperiospira Archbold and Thomas, 1994. The former is distinguished from the latter by its transverse outline, ill-defined fasciculation if present at all, and lack of adminicula within the ventral interior. On the other hand, both genera are readily distinguished from members of the Neospiriferinae by fine and equidi- mensional costae, generally weak fasciculation and absent to weakly developed adminicula. As already noted, Kaninospirifer has very limited stratigraphical and geographical distributions. Kalash- nikov (1996) has listed the genus occurring mainly in the Arctic region (Arctic Canada, Greenland, Spitsbergen, Arctic Russia) and East Asia (South Primorye of Far East of Russia, southeast Mongolia, northeast China). Pavlova (1991, p. 130) also listed some previously reported species from Timor and the Salt Range as possible representatives of the genus, but the true identities of these species have not yet been confirmed. On the other hand, Gypospirifer sp. from the Middle Permian of the Hida Gaien Belt of cen- tral Japan (Tazawa, 2000, figs. 3.12, 3.13) appears referable to Kaninospirifer judging by its shape and costation pat- tern. In all of its confirmed occurrences, Kaninospirifer is known to be associated with Kazanian (or Wordian) faunas. Kaninospirifer sp. Figure 4.20 Remarks. — An incomplete ventral valve (NMV P308035) in the collection indicates Kaninospirifer. The specimen is characterized by a transverse outline, very weak fasciculation that is visible only on the umbo, fine and equidimensional costae numbering about 15 per cm at about 2 cm from the beak, and a broad and well defined sulcus. This specimen appears to be closest to Kaninospirifer kaninensis (Likharev, 1943, p. 279, figs. 1-4), type species of the genus, from the Kazanian (Wordian) of the Kanin Peninsula, Russia. The two forms share a transverse outline, weak fasciculations that do not form prominent bundles, fine and even costae, and a well developed sulcus, but further comparison is hampered be- cause of insufficient material in our collection, especially the total lack of knowledge of the interior. Pavlova (1991) assigned several species from the Middle Permian of Mongolia, South Primorye of Russian Far East, and northeast China to Kaninospirifer. Both K. incertiplicatus Pavlova (1991, p. 131, pl. 29, figs 5, 6; see also Fredericks, 1925, p. 27, pl. 4, figs. 111, 112) and K. adpressum (Liu and Waterhouse, 1985, p. 36, pl. 12, figs. 5-10; see also Pavlova, 1991, p. 132, pl. 29, figs. 7, 8) are larger than the present specimen, less transverse and more subquadrate in outline, and possess variably developed plicae on the shell surfaces. Gypospirifer sp., from the Middle Permian Moribu Formation of the Hida Gaien Belt of central Japan (Tazawa, 2000, figs. 3.12, 3.13), is likely a representative of Kaninospirifer, judging by its transverse outline, relatively fine and even costae and ill-defined fasciculation, but the ventral valve (Tazawa, 2000, fig. 3.12) seems to display slightly coarser costae than the present specimen. Subfamily Neospiriferinae Waterhouse 1968 Genus Neospirifer Fredericks 1923 Type species.—Spirifer fasciger von Keyserling, 1846. Neospirifer sp. Figure 4.15, 4.18, 4.21 Remarks. — An incomplete conjoined shell (NMV P308036) has a deeply V-shaped sulcus in the ventral valve and a highly elevated fold in the dorsal valve. The crests of the plicae that bound the sulcus are sharp. Costae on flanks are fascicostellate and fine, numbering about 10 per cm near the anterior margin. Each fascicle consists of 6-8 costae. This species differs from any known species of Neospirifer by its fine costae on both valves and the deep, V-shaped sulcus. N. fasciger (von Keyserling, 1846) is somewhat similar to this species in terms of its outline and general fasciculation pattern, but differs by its shal- lower and U-shaped sulcus and coarser costae. Neospiriferinae gen. and sp. indet. Figure 4.19 Remarks. — An incomplete ventral valve (NMV P308037) indicates possibly another species of Neospirifer or a related genus. The specimen has a subquadrate out- line, weak fasciculation, coarse and somewhat flattened costae which are grouped into bundles of two to four (gen- erally three), and a relatively broad and shallow sulcus. No known species of Neospirifer seems to resemble this specimen very closely. On the other hand, Cratispirifer nuraensis Archbold and Thomas (1985, p. 280, figs. 8A-F) Permian brachiopods from Xiujimgingi 295 from the Sakmarian of Western Australia appears comparable in general terms, especially on account of their coarse, flattened and equidimensional costae that are grouped into bundles of no more than four (usually three), but the latter species is clearly distinguishable by its trans- verse outline, a proportionally high ventral interarea, and flattened costae. Spirifer? sp. from the Kungurian Talatinsk Formation of the Kozhim River section of the Pechora Basin, Russia (Kalashnikov, 1998), shares a similar outline and costation pattern with the present specimen, but it has a deeper sulcus and a more convex umbonal region. Acknowledgements This paper is supported by the Australian Research Council (GRS), CAS Hundred Talents Program and the Major Basic Research Projects of MST (G200077700) of People’s Republic of China (SZS), and Deakin University (GRS). We are grateful to Zhan Li-Pei, Chinese Academy of Geological Sciences (Beijing), for his encouragement and discussions on matters related to this study. References Archbold, N.W., 1993: Studies on Western Australian Permian brachiopods 11. New genera, species and records. Proceedings of the Royal Society of Victoria, vol. 105, no. 1, p. 1-29. Archbold, N.W. and Thomas, G.A., 1985: New genera of Western Australian Permian Spiriferidae (Brachiopoda). Alcheringa, vol. 9, nos. 3-4, p. 269-292. 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Proceedings of the Royal Society of Victoria, vol. 110, no. 1/2, p. 323-343. 297 Paleontological Research, vol. 6, no. 3, pp. 299-319, September 30, 2002 © by the Palaeontological Society of Japan The Recent rhynchonellide brachiopod Parasphenarina cavernicola gen. et sp. nov. from the submarine caves of Okinawa, Japan NEDA MOTCHUROVA-DEKOVA', MICHIKO SAITO* AND KAZUYOSHI ENDO’ ‘National Museum of Natural History, 1 Tzar Osvoboditel Blvd., Sofia, 1000, Bulgaria (e-mail: dekov @ gea.uni-sofia.bg) *Department of Earth and Planetary Sciences, University of Tokyo, 7-3-1 Hongo, Tokyo, 113-0033, Japan (e-mail: michiko @ gbs.eps.s.u-tokyo.ac.jp) ‘Institute of Geoscience, the University of Tsukuba, 1-1-1 Tennodai, Tsukuba, 305-8571, Japan (e-mail: endo @arsia.geo.tsukuba.ac.jp) Received 2 August 2001; Revised manuscript accepted 5 July 2002 Abstract. A new micromorphic rhynchonellide brachiopod Parasphenarina cavernicola gen. et sp. nov. is de- scribed from submarine caves on the outer slopes of coral reefs in the Ryukyu Islands, Japan. Based on the presence of spinuliform crura, the new genus is included in the Family Frieleiidae Cooper, the diagnosis of which is emended. Detailed morphological observations of different-sized shells and intraspecific variability have shown that the morphology of the hinge plates changes considerably during ontogeny. It is suggested that the new genus Parasphenarina could have evolved from forms close to the extremely rare bathyal Pliocene genus Sphenarina Cooper. The diagnostic characteristics of Parasphenarina such as diminutive adult size and lack of septalium and median septum may represent paedomorphic evolution. Key words: Brachiopoda, Japan, Okinawa, ontogenetic variability, paedomorphic process, Parasphenarina cavernicola gen. et sp. nov., Recent, submarine cave Introduction Studies on the benthic fauna from more than thirty sub- marine caves on the outer slopes of coral reefs in the Ryukyu Islands and adjacent areas have been conducted since 1989. Thanks to the SCUBA diving technique it was possible to explore in detail the caves and collect a large amount of sediment samples. The samples turned out to be rich in many interesting organisms characteristic of cryptic habitats, such as bivalves, gastropods, chitons, polychaetes, crustaceans, brachiopods, bryozoans, echinoids, ahermatypic corals, sponges and _ benthic foraminifers. A number of taxonomic studies have been subsequently published: on molluscs (Hayami and Kase, 1992, 1993, 1996; Kase and Hayami, 1992; Kase and Kinjo, 1996) and ostracodes (Tabuki and Hanai, 1999). They report many unusual characteristics of the fauna, such as reduced adult size, anachronistic shell forms and life styles, paedomorphic forms in comparison with supposed ancestors, and unique taxonomic assemblages including many typical bathyal and abyssal genera. Some apparent ‘living fossils’ inhabiting the sheltered environment of the submarine caves were also discovered. The fauna as a whole is almost entirely different from that found in adja- cent seas outside the caves. The brachiopods collected from the submarine caves of the Ryukyu Islands include several species as yet undescribed. Among the brachiopod assemblage, a single rhynchonellide species was found. This paper describes this new, micromorphic, thin, transparent-shelled rhyn- chonellide species. Initially the new species was assigned with a query to the Pliocene genus Sphenarina Cooper, 1959 (Saito et al., 2000). Based on detailed morphological observations, study of the ontogeny, and comparison with the type species of the genus Sphenarina, we found enough evidence to propose a new genus for the rhynchonellides from the Okinawa submarine caves, herein named Parasphenarina cavernicola gen. et sp. nov. The closest taxon to the new species is Sphenarina ezogremena Zezina (Zezina, 1981) known from a single specimen from the Flores Sea. We include the species $. ezogremena in the new genus Parasphenarina. The new genus could 300 Neda Motchurova-Dekova et al. le Islet .. Kume Island, . J ’ 4 Okinawa Ryukyu Shimoji and Irabu Islets „x Miyako Taiwan @.” Yaeyama Figure 1. of submarine caves of Ie Islet. Islands. have evolved from forms morphologically close to the ex- tremely rare bathyal Pliocene genus Sphenarina from Sicily (cf. Cooper, 1959; Gaetani and Sacca, 1984). It is sug- gested that the diagnostic characteristics of Parasphenarina such as diminutive adult size and lack of septalium and me- dian septum may have resulted from paedomorphic evolu- tion. Study area and methods of investigation The submarine caves of Okinawa vary in size and topog- raphy, although they have many common characteristics. The caves are open to the forereef slopes, and their mor- phology is complicated, winding and bifurcating, with nu- merous crevices. The caves are in the Pleistocene Ryukyu Limestone, and generally have entrances at about 15 to 40 m water depth and horizontal lengths ranging from several meters to more than 70 m. Sediments on the cave floors are composed of calcareous mud and bioclasts. They are almost free of coarse terrigenous material (Hayami and Kase, 1996). The caves were probably formed by ground water during some lower sea level stages in the Pleistocene and finally drowned during the postglacial rise of sea level (Kase and Hayami, 1992; Hayami and Kase, 1993, 1996). Twelve submarine caves of the Ryukyu Islands (one is lo- Daidokutsu Che Devil's Palace | Fool'sPalace—>® : Witch's House>@ Toriike 702) Black Hole Shimoji Islet Ke Q Locality maps (after Hayami and Kase, 1993). A.Index map. B. Detail of A showing Ie, Irabu and Shimoji Islands. C. Localities D. Localities of submarine cave of Kume Island. E. Submarine caves of Shimoji Islet and Irabu Islet in Miyako cated in Kume Island, two in Ie Islet, seven in Shimoji Islet, and two in Irabu Islet, Miyako Islands (Figure 1) yielded specimens of Parasphenarina cavernicola for this study. Sessile benthic biota were collected by brushing the sur- faces of walls, ceilings and undersides of boulders or large shells of dead bivalves such as Pycnodonte taniguchii, with the assistance of divers. Boulders and dead bivalves that could be brought to the surface, as well as sediments in the caves, were also collected to look for live and dead indi- viduals under the binocular microscope. The morphology of the specimens was examined both under the binocular and scanning electron microscopes (SEM). For observing the microstructure of the primary layer surface, selected shells of Parasphenarina cavernicola were treated with do- mestic-grade bleach (sodium hypochlorite: approximately 5% (v/w)) for 12 to 18 hours to remove surface debris and the periostracum, then washed, dried, and mounted on stubs for SEM. Other shells were dried and embedded in epoxy resin, transversely cut at the maximum shell width, pol- ished with a set of diamond powders and subsequently etched with 5% (v/v) HCl for 5 seconds. Other specimens after drying were broken to observe the uneven natural fracture of the primary calcitic layer. All samples were then coated with Pt-Pd alloy, and photographed by a Hitachi S-2400S scanning electron microscope. The New brachiopod genus from submarine caves 301 Figure 2. Island. measurements of Parasphenarina cavernicola were taken using the Nikon profile projector V-12BDC. The specimens of Sphenarina sicula Davidson from the Pliocene of Messina, (Sicily, Italy), borrowed for compari- son from the Smithsonian Institution, National Museum of Natural History (USNM 549381a, b; Cooper, 1959), were photographed with a Hitachi S-2250N natural SEM with- out coating. One of the borrowed specimens (USNM 549381b) was embedded in epoxy and transversely sec- tioned to compare with the sections of the new species P. cavernicola. Systematic description Class Rhynchonellata Williams et al., 1996 Order Rhynchonellida Kuhn, 1949 Family Frieleiidae Cooper, 1959 Emended diagnosis.—Capillate to costellate or smooth rhynchonellides with subtriangular to teardrop outline and spinuliform crura. Remarks. — The family Frieleiidae was created by Cooper (1959) for capillate to costellate rhynchonellide genera with triangular outline, strong dental plates and spinuliform crura, supported by short plates uniting with the septum of the dorsal valve to form a septalium. At the same time Cooper (1959) introduced the family Hispanirhynchiidae for rhynchonellides having spinuliform crura, low or no median ridge but no septalium in the dorsal valve. In the first edition of the brachiopod volumes of the Treatise on Invertebrate Paleontology (Ager, 1965) the hispanirhynchiids were included in the family Frieleiidae, Holotype of Parasphenarina cavernicola gen. et sp. nov., 1 mm UMUT RB28220-MNOl-a, ‘Nakanoshima Hole’, Shimoji Islet, Miyako even though the hispanirhynchiid genera Hispanirhynchia Thomson and Sphenarina Cooper do not possess or have only a low median ridge in the dorsal valve and do not have a septalium by original diagnosis. However, according to our new observations (see below) on the type material of Sphenarina, this genus does possess an incipient septalium in the adult dorsal valve. This feature brings Sphenarina closer to the frieleiid genera with a septalium. Thus the separation of the hispanirhynchiid species into a family or subfamily seems not to be justifiable now, until a reap- praisal of other genera like Hispanirhynchia, Manithyris Foster and Abyssorhynchia Zezina demonstrates the lack of a septalium in the adult forms. The new genus Parasphenarina lacks a septalium and a typical median septum. In the present state of knowledge we prefer to emend the diagnosis of the family Frieleiidae to exclude the presence of a septalium from the diagnosis and to include smooth-shelled genera like Parasphenarina into the family. Frieleiidae ranges from Pliocene to Recent. Genus Parasphenarina gen. nov. Type species. — Parasphenarina cavernicola sp. nov., Recent, Okinawa Islands, Japan. Derivation of name.—From Greek para = near, close to, referring to the similarity to the genus Sphenarina and sug- gesting that Parasphenarina could have evolved from forms close to Sphenarina. Diagnosis.—Diminutive smooth teardrop-shaped to tri- angularly oval rhynchonellides with smooth semitranspar- ent shell; subequivalve, rectimarginate anterior commis- sure; suberect to straight beak, hypothyrid auriculate = S + Ÿ (a) > © 4 ® A (a) > © = = Be) 3) —_— = Le) T © zZ — 4 New brachiopod genus from submarine caves 303 foramen, disjunct deltidial plates. Dorsal valve lacks a median ridge, though a shallow groove between two low ridges may be present instead. Crura spinuliform; cardinal process and septalium absent. Hinge plates and inner socket ridges do not meet together in posterior part of dor- sal valve. Species assigned.—Besides the type species Parasphe- narina cavernicola sp. nov., only one more species based on a single specimen and referred previously to the genus Sphenarina, is here included in the new genus—the Recent Sphenarina ezogremena Zezina, found in the Flores Sea, north of Bali Island. Thus, the new combination Parasphenarina ezogremena (Zezina) is adopted below. Remarks.—Parasphenarina is most similar to the genus Sphenarina Cooper, 1959 from the Pliocene of Sicily, Italy. Initially we tentatively assigned the new cave rhynchonel- lide species to the genus Sphenarina (Saito et al., 2000) based on similar shape, spinuliform crura, rectimarginate anterior commissure, well developed hinge plates and lack of a median septum and septalium. According to the origi- nal diagnosis, Sphenarina does not possess a median sep- tum. We examined the type material of Sphenarina used by Cooper, deposited at the National Museum of Natural History, Smithsonian Institution, Washington. Additio- nally we borrowed for comparison and serially sectioned one of the topotype specimens from the Pliocene of Messina (Sicily, Italy). In contrast to Cooper’s diagnosis (1959, p. 63) we discovered a low median septum and a small incipient septalium in the umbonal part of the dorsal valve of the sectioned specimen of Sphenarina sicula (Davidson). The sectioned specimen with septalium (Figure 14.2) was larger (L = 15.60 mm, W = 15.10 mm, T = 8.40 mm) than the one figured by Cooper (1959, PI. 8-A7) and in this paper on Figure 14.1 (L = 12.55 mm, W = 10.50 mm, T = 6.60 mm). It is possible that the septalium in Sphenarina develops in the late adult stage only and is not present in juvenile individuals. Since Sphenarina is an extremely rare genus (Gaetani and Sacca, 1984; personal communication, 2001) it is not possible to section further material to check the development of a septalium in other adult shells. However, a similar exam- ple of presence of a better developed septalium in a large specimen of Burmirhynchia turgida Buckman from the Bathonian of Laz, Yugoslavia is figured by Raduloviè (1991, figs 4, 5). From our data, we can assert that the new genus Parasphenarina differs from the Pliocene genus Sphenarina in the lack of a median septum and septalium in the adult stage. The hinge plates and the inner socket ridges of the new genus do not meet at the top of the dorsal valve, and remain separated (Figures 5.1, 5.3, 5.5, 6.3). In contrast, the hinge plates and the inner socket ridges of Sphenarina meet together at the top of the dorsal valve. Additionally, an incipient cardinal process was noted in the specimen dissected by Cooper (Figure 14.1). Parasphe- narina is micromorphic in size and has completely smooth shells, disjunct auriculate deltidial plates, poorly developed dental plates, delimiting narrow umbonal cavities and an elaborate pedicle collar, while Sphenarina is larger in size, finely capillate, with deltidial plates that can be conjunct (towards later ontogenetic stages), and has well developed dental plates and a shorter pedicle collar. The revision of the genus Sphenarina will be discussed elsewhere. Parasphenarina is externally similar to Cryptopora Jeffreys and Tethyrhynchia Logan. However the three genera can be easily distinguished by their internal mor- phology, especially by the development of three different types of crura: spinuliform, maniculiform and luniform re- spectively, which places them in three different families. Parasphenarina cavernicola sp. nov. Figures 2-12 Sphenarina? sp., Saito et al., 2000, p. 77; Saito et al., 2001, p. 131, 132. Derivation of name. —From Latin caverna = cave plus the Latin suffix -cola = dweller, inhabitant, after its occur- rence in submarine caves. Holotype.—The holotype specimen (UMUT RB28220- MNO1-a) (Figure 2) and 19 paratypes (UMUT RB28220- MNOI-b) were collected at 27 m depth from the bottom of the cave ‘Nakanoshima Hole’, Shimoji Islet, Miyako Island. The holotype and all the paratypes are deposited at the University Museum, the University of Tokyo (UMUT). Material and occurrence.—Twenty-one living speci- mens and more than 80 intact dead shells, many separated valves and fragments from 12 submarine caves in coral reefs of the Ryukyu Islands (Figure 1). The material is de- posited at the University Museum, the University of Tokyo (UMUT RB28210-28222). One complete specimen, two ventral and two dorsal valves are housed at the National Museum of Natural History, Sofia (NMNHS 31068). Brief descriptions, the location of the caves and sample numbers are given below. The appended data on the geo- graphical position, length, bottom depth and description of these caves are from Hayami and Kase (1993) with two ad- @ Figure 3. Parasphenarina cavernicola gen. et sp. nov., Shimoji Islet, Miyako Island. 1. Umbonal part of specimen UMUT RB28220-R1-7, ‘Nakanoshima hole’. 2. Detail of 1 showing the fine capillation anterior to the protegular node. 3. Umbonal part of specimen UMUT RB28220- R1-6, ‘Nakanoshima hole’. 4. Ventral beak showing the teeth and disjunct deltidial plates UMUT RB28220-R5-8, ‘Nakanoshima hole’. 5. Sub- circular juvenile specimen UMUT RB28219-R4-1, ‘Coral hole’. 6. Detail of 5 showing the umbonal part. > S + v 3 > © nA oO A (as) > © S =) de oO S s Ss T o Z New brachiopod genus from submarine caves 305 ditional caves (‘Umagai’ and ‘Nakanoshima Hole’) not mentioned by them. The bottom depth data are given for the entrances and the innermost parts of the caves: Kume Island: 1. ‘Umagai’ cave (26° 21.3° N, 126° 53.3° E), more than 25 m long, curved tunnel, innermost part is totally dark (-28.3 m to 26 m deep), UMUT RB28210-KU05. Ie Island: 2. ‘Shodokutsu’ (26° 42.9° N, 127° 50.1° E), more than 30 m long, totally dark, winding and branching tunnel (-20 to -7 m deep), UMUT RB28211-IS01, IS 02, ISO5, IS23; 3. ‘Daidokutsu’ (26°42.9° N, 127°50.1° E), about 10 m long, very dark, cathedral-like wide cave (-20 m deep), UMUT RB28212-ID07, ID11, ID14, ID17, ID18; a mixed sample UMUT RB28213-ISDO1 from ‘Shodokutsu’ and ‘Daidokutsu’ caves. Shimoji Island. 4. ‘Devil’s Palace’ (24° 49.6° N, 125° 08.2° E), about 15 m long, dark tunnel (-25 m deep) with some narrow openings on the ceiling, UMUT RB28214-MD02, MD03; 5. ‘Fool’s Palace’ (24° 49.6° N, 125°08.2° E), about 10 m long, almost totally dark tunnel (-35 to -32 m deep), #UMUT RB28215-MFOI, MF02, MF04, MFO5; 6. “Witch’s House’ (24° 49.3° N, 125° 08.3° E), more than 10 m long, totally dark tunnel (-37 to -35 m deep), UMUT RB28216-MM06, MMO7, MM09; 7. ‘Toriike’ (24° 49.1° N, 125° 08.3° E), a famous diving point, about 30 m long, large dark tunnel connected with two large side tunnels (-40 to -12 m deep), UMUT RB28217-MT06; 8. ‘Black Hole’ (24° 49.1” N, 125° 08.3° E), about 70 m long, totally dark stepwise tunnel with an air pocket in the innermost part (-35 to 0 m deep), UMUT RB28218-MB06; 9. ‘Coral Hole’ (24° 48.0° N, 125° 09.0° E), about 5 m long, dark hole and tunnel (-35 m deep), UMUT RB28219-MS01, MS02, MS03, MS05, MS06, MS07, MS08, MS09, MS10, MS12, MS13, MS16, MS17; 10. ‘Nakanoshima Hole’ (24° 48.47° N, 125°08.65° E), a submarine cave totally dark inside, entrance about 20 m deep, UMUT RB28220-MNOl (including the holotype and paratype), MNO2, MNO3. Irabu Island. 11. ‘W-arch’ (24° 51.7° N, 125° 09.7°E), double dark caves with an opening on the ceiling (-15 to -13 m deep), UMUT RB28221-MWOl, MW05; 12. ‘Cross Hole’ (24° 51.67’ N, 125° 09.5° E), 20 m long, dark hole with complicated mor- phology (-25 to -20 m deep), UMUT RB28222-MC13. Ecology and associated brachiopods.—Live individuals of Parasphenarina cavernicola were mainly found attached to the undersides of hard substrates lying on the cave floor near the entrance, and were occasionally found on the cave wall at the middle of dark tunnels (such as ‘Coral Hole’) as a member of a cryptic brachiopod-sclerosponge commu- nity, but never found from the innermost part of the closed cave that does not have sufficient water movement. So far, fresh empty shells of P. cavernicola are limited to the sediments from within the caves and only a single fragmen- tary shell was collected from sediments outside the caves. Thus, P. cavernicola should be regarded as typically a cave-dweller. Brachiopods associated with P. cavernicola include: Craniscus cf. japonicus, Terebratulina sp., Argyrotheca Sp.l, Argyrotheca sp.2, Frenulina sanguinolenta, ‘Frenulina’ sp., ‘Amphithyris’ sp., Theci- dellina sp. and Lacazella sp. (Saito et al., 2000). Dead shells of P. cavernicola were most abundant in ‘Nakano- shima Hole’ cave, where the holotype was collected. In this cave P. cavernicola represents 11.2% of the total (N = 116) of the brachiopod dead shell assemblage. Corresponding figures for other brachiopods in the same cave are: Craniscus -11.2%, Argyrotheca sp.1 -14.7%, Argyrotheca sp.2 -0.9%, Frenulina sanguinolenta -1.7%, ‘Frenulina’ sp. -47.4%, Thecidellina sp. -1.7% and Lacazella sp. -11.2%. All those cave brachiopods are characterized by a minute adult shell size, usually less than 5mm in length, which could have resulted from employ- ment of the same adaptive strategy to the dark and oligotrophic environment as advocated for other cave- dwelling brachiopods, including the rhynchonellide Tethyrhynchia from the Mediterranean caves (Logan and Zibrowius, 1994; Simon and Willems, 1999), and cave molluscs (Kase and Hayami, 1992; Hayami and Kase, 1996). Diagnosis.—Parasphenarina with abraded rounded ven- tral beak and poorly defined dental plates; teeth and dental sockets not corrugated. During ontogeny inner hinge plates appear in juveniles but are almost completely resorbed in adult individuals. Outer hinge plates appear in mid-sized specimens and develop gradually during ontogeny to reach their maximum size in adult and gerontic specimens. Description.—Shell diminutive, impunctate, translucent, delicate, teardrop-shaped to rarely oval in outline, longer than wide, equibiconvex or dorsibiconvex. Maximum ob- served length (L) -6.20 mm, width (W) -5.51 mm, and thickness (T) -3.54 mm. Maximum width and thickness at midvalve; anterior commissure rectimarginate; lateral commissures straight. Surface smooth, with well defined growth lines; in adult specimens better developed anteriorly @ Figure 4. Parasphenarina cavernicola gen. et sp. nov. Shimoji Islet, collar and heart-shaped muscle field, specimen UMUT RB28220-R5-11, ‘ pedicle collar, teeth and dental plates, specimen UMUT RB28219-R2-3, ‘Coral Hole’. Miyako Island. 1. Interior of a ventral valve to show the sessile pedicle Nakanoshima Hole’. 2. Interior of a ventral valve showing the sessile 3. Detail of 2 showing the left tooth, dental plate and the narrow umbonal cavity. 4. Detail of 2 showing the right tooth, dental plate and the narrow umbonal cavity. 5. Umbonal part of a large ventral valve showing close disjunct deltidial plates, UMUT RB28220-R2-9. 6. The same valve from 5, inclined to show the large teeth and pedicle collar lying on the valve floor. ES is] + Ÿ (ao) > © 4 oO A Ss > © = =) = o — = 3S T o Z New brachiopod genus from submarine caves 307 with slight imbrication laterally. In many specimens umbonal part of shell, just anterior to smooth protegular node, finely capillate (Figure 3.1-3.3). Beak almost straight, foramen hypothyrid, large, deltidial plates disjunct, auriculate (Figure 3.1, 3.4, 3.6). Ventral beak abraded, due to migration of pedicle towards ventral valve; foramen thus has a rounded tip (Figure 3.1, 3.3, 3.4, 3.6). Beak ridges not defined. Ventral valve interior with short but elongate, uncorrugated, large teeth (Figure 3.4), supported by incipi- ent, short, divergent dental plates, developed close to shell wall, forming shallow, narrow umbonal cavities (Figure 4.1, 4.3, 4.4). Pedicle collar large, elevated above valve floor forming a chamber beneath, with well defined growth lines (Figure 4.1-4.4). Muscle field large, heart-shaped (Figure 4.1, 4.2), occupying 1/4 to 1/3 of shell length. No pallial markings. Dorsal valve interior with uncorrugated dental sockets, bounded by well developed socket ridges. Inner socket ridges thick; no cardinal process. Crura of spinuliform type, short blade-like (Figure 5.3-5.6), often widening like a spade at their distal ends (Figure 6.2, 6.4). Juvenile specimens have inner hinge plates (Figures 5.1, 11.1); adult specimens develop outer hinge plates, inclined dorsally to shell floor (Figure 5.3, 5.5). Relatively large circular mus- cle field defined by distinct slopes laterally. In this field there is a shallow median groove bounded by two low ridges from sides (Figure 5.2). No pallial markings visi- ble. Compared to muscle field of other frieleiid genera musculature of this genus is feeble, correlating closely with reduced size. Serial sections of an adult specimen embedded in epoxy show clearly divergent plates, narrow umbonal cavities, close to lateral wall and strong teeth (Figure 7). In dorsal valve, outer high plates dorsally inclined and spinuliform crura arise from dorsal side of hinge plates. Anteriorly, crura with weak crescent shape sections (convex outward). Median groove very weak and sinuated in centre between two low ridges in muscle field, outlined by lateral slopes. Majority of living individuals juvenile. Lophophore rarely preserved, of a schizolophous type in a specimen 1.8 mm long with long setae present (Figure 8.1). Largest liv- ing specimen (L = 5.45 mm) with a spirolophous-type lophophore, but its shape, number of volutions and orienta- tion unknown due to mechanical distortion. Mature go- nads observed in posterior part of mantle in same specimen (Figure 8.2). Measurements.—Length (L), width (W) and thickness (T) of all the intact specimens (except the living ones) were measured. The living individuals were measured for length and width only. Scatter graphs for L/W and L/T show more or less linear relationships (Figure 9A). Slopes of the regression lines for double-logarithmic scatter plots (Figure 9B) based on reduced major axis (Kermack and Haldane, 1950) were 0.99 and 1.12 for L/W (N = 126) and L/T (N = 70), respectively, and both were not significantly different from the slope of 1 (isometry) at the 95% confi- dence level. Intraspecific variability. — The majority of the adult specimens have a teardrop outline (Figure 2), but some specimens are oval. The growth lines are well expressed in the majority of individuals, but some have weaker growth lines. Some individuals have well defined capillae just anterior to the smooth protegular node. This is better expressed in the dorsal valves (Figure 3.1-3.3). Some shells do not have well defined muscle fields in both valves, while others do. The cross sections of the crura are quite variable. Usually they represent straight thin vertical lamina or have slight crescent-shaped sections convex outward (Figures 5.1, 6.2, 7). In some specimens the crura are curved longitudinally, similar to falciform (Figure 6.5) or are gently sigmoidal anteriorly (Figure 5.6). Ontogeny.— The smallest individual collected is 0.88 mm long and 0.73 mm wide. The variability of the cardinalia was studied in a sequence of 17 dorsal valves of different size, representing different ontogenetic stages (Table 1). The smallest dorsal valve is 0.92 mm long and 0.92 mm wide, and the largest one examined is 5.51 mm long and 5.37 mm wide. It was noticed that the smallest specimens (early juveniles) have slight or no inner hinge plates and no outer hinge plates (Figure 6.1, 6.3). The ju- venile specimens between 1.4 and 2.7 mm length have well defined inner hinge plates but no outer hinge plates (Figures 5.1, 11.1), the crural bases being directly attached to the inner socket ridges. In juvenile and mid-sized speci- mens the inner socket ridges are swollen posteriorly. With increasing age the socket ridges decrease relatively in size and remain well defined, but not swollen. Dorsal valves, more than 3 mm in length, already have incipient outer hinge plates, inclined to the shell floor. The larger the valve is, the longer and better expressed the outer hinge plates are, and they become inclined to the shell floor @ Figure 5. dorsal valves. For dimensions of the valves see Table 1. plates, UMUT RB28220-R1-12. showing well developed outer hinge plates, UMUT RB28220-R1-3. anterolaterally. Parasphenarina cavernicola gen. et sp. nov. Shimoji Islet, Miyako Island, ‘Nakanoshima hole’. 4. The same specimen as on 3 showing lateral view of the crura. of large specimen showing well developed outer hinge plates, UMUT RB28220-RI -8. Cardinalia of three different-sized 1. Interior of middle-sized dorsal valve showing crura and well developed inner hinge 2. The same valve from 1 showing the median groove between two ridges. 3. Cardinalia of a larger specimen 5. Cardinalia 6. The same specimen from 5 showing the crura Neda Motchurova-Dekova et al. New brachiopod genus from submarine caves 309 4? III .65 0.7 0.75 0.8 0.9 -_ <_ Am 4 13 1. Un Figure 7. Sixteen quasitransverse serial sections through the umbo of Parasphenarina cavernicola gen. et sp. nov. Specimen UMUT RB28220-MNOI-c, ‘Nakanoshima hole’ Shimoji Islet, Miyako Island. L = 4.5 mm, W = 4.1 mm; T = 2.3 mm. Distance from ventral umbo given in mm. The asymmetry of the sections is due to the slight lateral inclination of the minute shell during sectioning. @ Figure 6. Parasphenarina cavernicola gen. et sp. nov. For dimensions of the dorsal valves see Table 1. 1-5 Specimens from Shimoji Islet, Miyako Island, ‘Nakanoshima hole”. 1. Juvenile crus, swollen inner socket ridge and incipient inner hinge plate seen in the commissural plane, UMUT RB28220-R5-4. 2. The same crus as on 1, seen laterally to show the spadelike shape. 3. Cardinalia of juvenile specimen, UMUT RB28220-R5-9. 4. The same valve from 3 seen laterally. 5. Cardinalia of a middle-sized specimen with crescent-shaped crura and inner hinge plates, UMUT RB28220-R1-10. 6. Cardinalia of adult or gerontic specimen showing the ventral curving of the distal ends of the crura, specimen from a mixed sample UMUT RB28213-R9 from ‘Shodokutsu’ and ‘Daidokutsu’ caves, le Islet, Okinawa Islands. 310 Neda Motchurova-Dekova et al. Figure 8. Parasphenarina cavernicola gen. et sp. nov. 1. Setae and schizolophous lophophore in juvenile specimen seen through the transparent shell. a, ventral side. 1b, dorsal side. Specimen UMUT RB28214-MD03-a, “Devil’s Palace’, Shimoji Islet, Miyako Island. 2. Distorted spirolophous lophophore in larger speci- men. Mature gonads are seen in the posterior part of the mantle. Specimen UMUT RB28212-ID11-a, ‘Daidokutsu’ cave, Ie Islet, Okinawa Islands. (Figures 5.3, 5.5, 7). The crura in the juvenile specimens are shorter and slightly curved ventrally with spadelike anterior tips (Figure 6.2, 6.4). As pointed out by Dagys (1974), during ontogeny spinulifer crura simply increase in size. However, some larger specimens show characteristic stronger ventral bending of the distal ends of the crura (Figures 5.6, 6.6). The median dorsal groove between two low ridges is present in all stages except the early juvenile and with age it becomes better defined. The juvenile ventral valves do not have dental plates de- tached from the shell wall, so the umbonal cavities are still not developed. The teeth are relatively large in juvenile specimens. During growth dental plates appear and start detaching from the lateral wall of the umbo. In adults they are well defined, but remain close to the wall, delimiting narrow umbonal chambers (Figure 4.1-4.4). With age the teeth become elongate in the commissural plane, but re- main low perpendicular to this direction (Figure 4.5, 4.6). The juvenile individuals have well developed winglike deltidial plates (Figure 3.1, 3.6). In adults the deltidial plates are sometimes resorbed, but some specimens show excessive growth. In the largest ventral valve (L = 5.7 mm), the deltidial plates are very close to each other and the pedicle collar lies on the valve floor (Figure 4.5, 4.6). Shell ultrastructure.—The shell ultrastructure of Para- sphenarina cavernicola was observed using SEM by differ- ent preparation methods. The shell is very thin: maximum 300 um in the centroanterior part. Laterally it is thinner and reaches 20 um. It consists of two calcite layers, primary and secondary. In some cases the periostracum was preserved on the shell surface, but for examining the microstructure of the external surface of the primary layer it was removed using domestic grade bleach as described in the previous section. Thus, its negative impressions on the external surface of the primary layer were revealed (Figure 10). They represent subparallel labyrinthine trenches normal to the growth lines of the shell. Such casts have been observed in different or- ders of brachiopods and were recently reappraised by Williams (1997, in Kaesler, 1997, p. 269-271). The primary layer is 5 to 10 um thick. It is built up of parallel rodlike calcite aggregates normal to the shell sur- face, which according to the method of treatment of the sample and the angle of observation can have different as- pects, some of them illusory. The most typical texture of the primary layer observed is the vertical (normal to the bounding surfaces of the primary layer) (Figures 11.3, 11.4, 11.6, 12.2-12.4). It reflects the orientation of the parallel rodlike aggregates of calcite crystallites. The tips of the individual rodlike crystallites are better seen after etching the external surface of the layer (Figure 10.3, 10.4). The growth of the crystallites starts from the boundary between New brachiopod genus from submarine caves Table 1. 311 Ontogenetic variability of the cardinalia in Parasphenarina cavernicola gen. et sp. nov. Ld, length of the dorsal valve; Wd, width of the dorsal valve; Ler, length of the crura = distance from the posteriormost point of attach- ment of the hinge plate to the anteriormost part of the crura tip, measured in the commissural plane; all in mm). AS ur Figure Ld No. 5 RB28220-R5-9 6.3, 6.4 0.92 RB28220-R5-1 0.97 RB28215-R5-2 ? RB28220-R5-4 6.1, 6.2 1.02 RB28220-R5-6 1.03 RB28215-R3-6 1.4 RB28219-R2-2 1.47 RB28220-R5-10 Eu le) 1.9 RB28219-R4-4 2.71 RB28220-R1-12 51152 2.71 RB28220-R1-10 6.5 2.89 RB28215-R3-5 ? RB28215-R3-2 3.67 RB28220-R1-3 5.3, 5.4 3.74 RB28219-R2-1 ? RB28220-R1-8 D255) 5:0 4.59 RB28213-R9 6.6 5.51? T, W (mm) L (mm) wd eee Inner hinge Outer hinge plates plates 0.92 0.18 ? no 0.95 0.26 slight no ? 0.23 slight no 1.01 0.23 slight no 1.05 0.22 slight no 1.4 0.36 strong no 1.82 0.41 strong no 1.85 0.47 strong no 2.76 0.62 strong no 2.67 0.67 strong no 2.88 0.61 strong no ? 0.73 slight yes 3.92 0.79 slight yes 4.34 0.84 ve well developed ? 0.97 slight short 4.69 1.22 ? well developed 5.37 1.02 slight well developed 10 W-le W-Miyako W-Kume T-le T-Miyako T-Kume T, W (mm) i 1 10 L (mm) Figure 9. Shell measurements of Parasphenarina cavernicola gen. et sp. nov. Scatter plots (A) and double logarithmic scatter plots (B) of shell length (L) versus maximum shell width (W) and thickness (T). dicated separately. the periostracum and primary layer, where the crystallites are finer and not well defined, and advances towards the boundary between the primary and secondary layer. Some micrographs taken at different angles and higher magnifica- tion reveal a horizontal texture, which shows a fine Jamina- tion parallel to the shell surface and the boundary primary/secondary layer (Figures 11.4, 12.1, 12.2, 12.6). These are surfaces of synchronous growth of the crystal ag- Specimens from Ie, Miyako (Irabu and Shimoji islands), and Kume Islands are in- gregates (induction faces of common growth), which give a laminated aspect to the layer at high magnification. Parasphenarina cavernicola differs from Notosaria nigricans (Sowerby) in the parallel orientation of the syn- chronous growth surfaces. Notosaria nigricans develops its synchronous surfaces oblique to the two boundaries (Williams, 1971). An unusual pseudo-porcelain appear- ance, probably an artifact due to over coating with Pt-Pd 312 Neda Motchurova-Dekova et al. Figure 10. Islet, Miyako Island. 5% HCl for 5sec. top right corner the primary layer is broken off and the underlying fibres are visible. * À Views of the external surface of the primary layer of Parasphenarina cavernicola gen. et sp. nov., “Nakanoshima Hole’, Shimoji 1, 3, and 4 specimen UMUT RB28220-ss3-vv, fragment of a dorsal valve, treated with 5% v/w bleach for 13h and etched with 1. General view of the external surface of the shell (respectively of the primary layer). Three growth lines are visible. In the The trenches perpendicular to the growth lines represent nega- tive casts of periostraca dissolved by bleach. 2. Specimen UMUT RB28220-ss4-vv, fragment of a ventral valve, treated with 5% v/w bleach for about 3h and over etched with 5% HCI for longer period-15sec. Labyrinthine trenches are overetched impressions of periostraca casts in the primary layer. 3. Detail of 1. 4. Detail of 3. alloy, was observed on some spots of the primary layer (Figure 12.5). The large fibres of the secondary shell, arranged in or- thodox fashion, form a mosaic on the internal part of the valves (Figure 11.2). The fibres are usually rhombic in cross section. They are extraordinarily large: 50-100 um in width and 20-40 um in thickness. Near their origin (the boundary with the primary layer) the fibres are smaller (40-60 um wide and 15-25 um thick) and represent well Tips of spiky calcite crystallites. shaped rhombi. They expand rapidly towards the interior of the shell (80-140 um wide and 30-40 um thick), losing their regular rhombic shape and becoming irregular rhombi, polygons, or anvil-shaped and sometimes have rounded margins (Figure 11.3, 11.5, 11.6). Among other genera with spinuliform crura, scanty data on the shell ultrastructure are illustrated on Manithyris rosii Foster, Compsothyris racovitzae (Joubin) and Compsothy- ris ballenyi Foster (Foster, 1974, pl. 9). The width of the New brachiopod genus from submarine caves fibres on the internal surface of the ventral valve is 50 um in Manithyris rosii and 40 um in Compsothyris. Compared to the fibres of Parasphenarina cavernicola, the fibres in Manithyris and Compsothyris are narrower and the mosaic they form is different. Popov (1978) published 3 micro- graphs from different parts of the internal surface of the shell of Frieleia halli Dall showing fibres differing in size and morphology. Two of the micrographs show peculiar terminal faces of the fibres wrinkled parallel to the long axes (Popov, 1978, figs 1b-d). A. Williams provided for comparative study five micrographs showing the shell ultrastructure of two frag- ments of Frieleia halli. In addition he commented (per- sonal communication, 2000) on the peculiarities of the ultrastructure of this species: The external surface of the primary layer is sporadically pitted, probably by the im- prints of the mucin-filled vesicles within the infrastructure of the periostracum (Figure 13.2). The primary layer seems finely laminated at high magnification (Figure 13.3), as described above for Parasphenarina cavernicola. At lower magnification the primary layer is crossed by nearly vertical planes, which are also comparable to the edges of the aggregates of parallel rodlike crystallites described above (Figure 13.2). The shell mosaic is somewhat differ- ent (Figure 13.1). The fibres are 40-50 um wide, ex- tremely flat and unusual in the way the apices of the terminal faces appear to be wrinkled parallel to the long axes of the faces (Figure 13.1), similar to that figured by Popov (1978). Thus, the shell ultrastructure in the family Frieleiidae ap- pears coarsely fibrous although more data are needed to draw conclusions about the taxonomic importance of ultrastructure in frieleiids in particular, and in the Norelloidea as a whole (cf. Mancenido and Owen, 2001 for a new rhynchonellid classification). It is noteworthy that a similar coarse-fibrous fabric has been already reported in Cretaceous Pugnacoidea, in contrast to the fine-fibrous ultrastructure in Cretaceous Rhynchonelloidea and Hemithyridoidea (Mochurova-Dekova, 2001). However, it should be noted that shell ultrastructure might be influ- enced by water temperature and other environmental fac- tors as well. The coarseness of the mosaic and other ultrastructure features are probably largely genetically de- termined phenotypic changes favoured by natural selection in a particular environment over a long period of time but may also be evoked somatically (without change of geno- type) by the same environmental conditions in the short term (M. Foster, personal communication, 2002). It is necessary to make quantitative studies of a large number of specimens of many different species from a wide variety of habitats to make sound observations and conclusions. DNA sequence data. — Mitochondrial cytochrome c oxidase subunit I (coxl) gene sequence, DDBJ accession 313 number AB053201 (Saito et al., 2001). Comparison.— Parasphenarina cavernicola closely re- sembles P. ezogremena (Zezina) in size, shape of the shell and crura and in having a shallow median groove bounded by low ridges in the dorsal valve instead of a typical me- dian septum. Parasphenarina ezogremena differs from P. cavernicola in having a well defined larger triangular fora- men with pointed acute beak. It lacks the characteristic abraded rounded ventral beak of Parasphenarina caver- nicola. P. ezogremena has corrugated socket ridges and teeth, supported by stronger dental plates, while socket ridges and teeth are smooth and dental plates are poorly de- veloped in Parasphenarina cavernicola. After examining several specimens of the new rhynchonellide from the Okinawa submarine caves, Zezina (personal communica- tion, 2000) also suggested they be placed in a new species to distinguish them from Parasphenarina ezogremena (Zezina). Parasphenarina cavernicola sp. nov. resembles Sphe- narina sicula Davidson in the shape of the shell and crura (Figure 14.1) and the rectimarginate anterior commissures. The umbonal part of P. cavernicola, just anterior to the smooth protegular node, is finely capillate, which is reminiscent of the fine capillation of the entire shell of S. sicula. The main differences are given in the comparison between the two genera. Parasphenarina cavernicola dif- fers from Sphenarina sicula in being smaller in size, com- pletely smooth, with well developed growth lines, a larger foramen, consistently disjunct deltidial plates, relatively larger teeth, and very narrow umbonal chambers in the ven- tral valve, limited by slightly developed divergent dental plates. These are differences that could be also of specific importance. The most important difference between the two species (and genera) is in the cardinalia The cardinalia of Sphenarina sicula are relatively more mas- sive, have an incipient cardinal process, the hinge plates and inner socket ridges join together posteriorly (Figure 14.1), and a small septalium is present in the sectioned adult shell (Figure 14.2). In Parasphenarina cavernicola the hinge plates and socket ridges remain separate (Figures 5.1, 5.3, 5.5, 6.3) and touch the valve floor, which together with the lack of a median septum totally excludes the pos- sible formation of a septalium. In S. sicula the crural bases project more ventrally than dorsally in adult shells (Figure 14.3), while in Parasphenarina cavernicola the crural bases project dorsally only (Figures 5.3-5.6, 7). Discussion The abundance of material, representing populations of Parasphenarina cavernicola inhabiting different caves, al- lows us to study in detail the intraspecific variability and the ontogeny of the shells. Such studies aid in preventing Neda Motchurova-Dekova et al. New brachiopod genus from submarine caves 315 undue the taxonomical splitting that often arises when new species and genera are erected only on the basis of scarce material. As pointed out by Foster (1974), genera have customarily been too narrowly defined in the rhynchonellides. Some of the genera were monospecific when they were erected. Thus, their diagnoses coincided with the diagnoses of the type species. Including new spe- cies in such monospecific genera is always difficult. In the case of Parasphenarina cavernicola we have preferred to introduce a new genus rather than to emend the diagnosis of the closest genus Sphenarina, based on the absence of a septalium in the new genus. Another hampering factor was the lack of previous ontogenetic observations on the known species belonging to the Frieleiidae, except for Foster (1974), where he commented on the ontogeny of Compsothyris racovitzae (Joubin). As a whole, the rhynchonellides are considered as a group with primitive cardinalia and their possible ontogenetic changes were nor- mally neglected. Several authors in the past have drawn attention to the need to include in taxonomic descriptions detailed accounts of growth stages (Surlyk, 1972; Lee and Wilson, 1979). A detailed account of the growth stages in Notosaria nigricans was given by Lee and Wilson (1979). Mancen ido and Walley (1979) point out the inadequacy of a classi- fication based on the mere presence or absence of a mor- phological feature in the adult stage. They recommend erection of new taxa on the basis of both juvenile and adult morphology and inclusion of this in the diagnosis. One important discovery resulting from this study was that the morphology of the hinge plates changes considera- bly during ontogeny. The morphology and the lack or presence of inner and outer hinge plates are often taken as a diagnostic generic character. After a careful examina- tion of dorsal valves of different size of Parasphenarina cavernicola, it turned out that the inner hinge plates are present only in juvenile shells, later being resorbed or trans- formed. The outer hinge plates develop later and are well defined only in the adult shells. Thus, examining scarce material, not representing all the stages, may lead to mis- identification or overestimation of some of the cardinalia features in rhynchonellides. In this instance we consider that too many genera were introduced on the basis of insuf- ficient material. In this case we suggest that genera estab- lished on presence/absence of inner/outer hinge plates or absence of septalium (for instance Sphenarina) should be carefully revised. According to Dagys (1974) spinuliform crura appeared in different groups of rhynchonellides as a result of ‘fetali- zation’ (i.e. paedomorphosis). Genera having spinuliform crura retain some juvenile aspects in the adult stage. Dagys (1974) noted that such genera are characterised by a triangular outline, weak to moderate convexity, lack of a sinus, and unisulcate to rectimarginate anterior commissures, which are indicative of juvenile characters in rhynchonellides. Cooper (1959) also noted that the rectimarginate anterior commissure is a youthful character. The adult individuals of Parasphenarina cavernicola are micromorphic and bear all of the above-mentioned juvenile characters. On the other hand, Parasphenarina has one of the simplest arrangements of cardinalia among rhynchonellides, lacking a septalium and median septum. Thus the occurrence of Parasphenarina cavernicola sup- ports Dagys’ hypothesis about the paedomorphic nature of the spinuliform crura. Parasphenarina can reach sexual maturity at a length of 5.45 mm (Figure 8.2). All these data support the hypothesis that Parasphenarina cavernicola can be regarded as a paedomorphically devel- oped form in the submarine caves of Okinawa. The rarity of the new genus in Recent seas is also noteworthy, the only other species, Parasphenarina ezogremena, being re- corded from a single specimen in the Flores Sea on the upper continental slope (Zezina, 1981). Taking into ac- count the morphologic similarities with the genus Sphenarina from Sicily it can be suggested that the new genus could have evolved from forms morphologically close to the extremely rare bathyal Pliocene genus Sphenarina through paedomorphosis. Heterochronic proc- esses have probably played an important role in the origina- tion of major new taxa and evolutionary novelties in post- Palaeozoic rhynchonellides. Frieleiids were interpreted as end-members of lineages, which become adaptively anach- ronistic in high-energy environments and eventually occu- pied refugia in deeper and darker low-energy habitats (Ma ncenido and Owen, 1996; Mancenido, 1997; Mancenido and Owen, 2001). Considering also the occurrence of as- sociated taxa from other phyla, the new frieleiid Parasphenarina cavernicola may be cited as yet another example of an anachronistic taxon with closest bathyal an- cestors, which has found refuge in the peculiar low- @ Figure 11. Parasphenarina cavernicola gen. et sp. nov, ‘Nakanoshima Hole’, Shimoji Islet, Miyako Islands. 1. Juvenile dorsal valve with well developed inner hinge plates and swollen inner socket ridges, specimen UMUT RB28220-R5-10. 2. Anterior of the dorsal valve of the same specimen as on 1 to show the study surface for the mosaic of the fibres (compare to Figure 13-1). tral umbo of a ventral valve of the same specimen as on Figure 7. 3-6. Transverse sections at 1.7 mm from the ven- Section thoroughly polished and subsequently etched with 5% HCI for 2-3 sec. 3. Secondary fibrous layer (above) and primary layer (below). 4. Detail of 3 to show the primary layer with the vertical edges of aggregates of calcite and fine horizontal lamination parallel to the shell surface. below. 5. The whole shell thickness showing the secondary fibrous layer and the primary layer 6. Detail of 5 showing the rhombic fibres and the primary layer. Neda Motchurova-Dekova et al. New brachiopod genus from submarine caves competition, sheltered microenvironment of the dark, oligotrophic submarine caves of Okinawa. 100 um | dt a ” = = = 10 um get 317 Acknowledgements We thank T. Kase (National Science Musueum, Tokyo), I. Hayami (Kanagawa Univ.), R. Tabuki (Univ. of Ryukyus) and T. Hanai (Tokyo) for the fruitful fieldwork we conducted together. We are also grateful to the coope- rative and skilled divers, S. Ohashi, S. Kinjo (Okinawa) and M. Taniguchi (Miyako Island). ©. Zezina (P.P. Shirshov Institute of Oceanology, RAS, Moscow) is thanked for kindly examining specimens of the new rhynchonellide and giving advice. A. Williams (Univ. of Glasgow) kindly commented on shell ultrastucture problems and placed at our disposal micrographs of Frieleia. D. Lee (Univ. of Dunedin), E. Owen (Natural History Museum, London), V. Raduloviè (Univ. of Belgrade), M. Foster (Bradley University, Peoria) gave valuable advice on an earlier version of the paper. We are grateful to the reviewers M. Mancenido (La Plata Natural Sciences Museum) and A. Logan (University of New Brunswick, Saint John) for the insightful and helpful com- ments. T. Dutro and J. Thompson (Smithsonian Institution, US National Museum) provided us with speci- mens of S. sicula for comparison. M. Gaetani (Univ. of Milan) and D. Sacca (Univ. of Messina) provided valuable information on S. sicula. R. Gatto (Univ. of Padua) sug- gested the new generic name Parasphenarina. Zh. Damyanov (Central Laboratory of Mineralogy and Crystallography, Sofia) helped with interpretation of the shell ultrastructure. Special thanks go to K. Moriya, I. Sarashina, T. Sasaki (Tokyo University), M. Ivanov (National Institute of Advanced Industrial Science and Technology, Tsukuba), T. Kodera (Nippon Marine Enterprises, Ltd., Yokohama) and V. Dekov (Univ. of Sofia) for their continuous technical help. N. Motchurova- Dekova gratefully acknowledges the Japan Society for the Promotion of Sciences for her postdoctoral scholarship at Tokyo University. She thanks K. Tanabe for the invitation Figure 13. Ultrastructure of two fragments of Frieleia halli Dall shell from the Smithsonian wet collection, USNM 421367, 550 m depth, 32° 40.7’ N, 117° 35.5° W, San Diego Trough. 1. Internal surface of the shell with orthodoxly stacked flat fibres, the apices of the terminal faces of which are wrinkled. 2. External surface of the shell sporadically pitted. Nearly vertical planes-edges of aggregated of parallel rodlike calcite crystallites. 3. Finely laminated primary layer, lamination parallel to bounding surfaces at higher magnifica- tion. @ Figure 12. layer according to the way of treatment of the sample, the angle of observation and the magnification. #UMUT RB28220-ss1-dv, treated with 5% v/w bleach for 13h, not etched. treated with 5% v/w bleach for 13h and etched with 5% HCI for 5sec. 3. Vertical texture. 4. Vertical texture. lamination. Parasphenarina cavernicola gen. et sp. nov., ‘Nakanoshima Hole’, Shimoji Islet, Miyako Island. Different textures of the primary 1. Finely laminated (horizontal) texture. Stub 2-6. Specimen UMUT RB28220-ss3-dv, fragment of a dorsal valve, 2. Horizontal (parallel to the shell surface) lamination and vertical texture. 5. Pseudo-porcelain appearance, probably an artifact due to overcoating with Pt-Pd alloy. 6. Horizontal 318 1 mm Il mm Figure 14. Sphenarina sicula Cooper. Pliocene, Milazzo (labelled as Milasso), Messina, Sicily. 1. Cardinalia of specimen USNM 549381a, the same figured by Cooper (1959, p. 8-A, fig.7). Dimensions: L = 12.55 mm, W = 10.50 mm, T = 6.60 mm. Note the incipient cardinal process. 2, 3. Two acetate peels showing selected serial sections of the interior of a larger specimen #549381b USNM. L = 15.60 mm, W = 15.10 mm, T = 8.40 mm. 2. Section 2.3 mm from the top of the ventral valve showing well developed divergent dental plates and incipient septalium. 3. Section 2.9 mm from the top of the ventral valve showing strong teeth, outer hinge plates, crural bases directed ventrally and low septum. Neda Motchurova-Dekova et al. to work at the Paleobiological Laboratory and for gener- ously making available all its facilities. This work was also supported by grants from the Ministry of Education, Science and Culture of Japan (nos. 11691196, 11833018), a JSPS Research fellowship (no. 3713 in 1998 for M.S.), the Fujiwara Natural History Foundation and a Sasakawa Scientific Research Grant from the Japan Society (M.S.), and a Sys-resource Grant (N.M.-D.). References Ager, D.V., 1965: Mesozoic and Cenozoic Rhynchonellacea. In, Moore, R.C. ed., Treatise on Invertebrate Paleontology, Part H, Brachiopoda, no. 2, pp. H597-H632, The Geological Society of America; New York, and University of Kansas Press, Lawrence. Cooper, G.A., 1959: Genera of Tertiary and Recent rhynchonelloid brachiopods. Smithsonian Miscellaneous Collections, vol. 139, no. 5, p. 1-90. Dagys, A., 1974: Triasovye brakhiopody (Triassic Brachiopods), 387 p. Nauka, Novosibirsk. (in Russian) Foster, M.W., 1974: Recent Antarctic and Subantarctic Brachiopods. Antarctic Research Series (Washington), vol. 21, 10 + 184 p. Gaetani, M. and Sacca, D., 1984: Brachiopodi batiali nel Pliocene e Pleistocene di Sicilia e Calabria. Rivista Italiana di Paleontologia e Stratigrafia, vol. 90, no. 3, p. 407-458. Hayami, I. and Kase, T., 1992: A new cryptic species of Pycnodonte from Ryukyu Islands: a living fossil oyster. Transactions and Proceedings of the Palaeontological Society of Japan, New Series., vol. 165, p. 1070-1089. Hayami, I. and Kase, T., 1993: Submarine cave Bivalvia from the Ryukyu Islands: systematics and evolutionary significance. The University Museum, The University of Tokyo, Bulletin, vol. 35, 133 p. Hayami, I. and Kase, T., 1996: Characteristics of submarine cave bi- valves in the northwestern Pacific. American Malacological Bulletin, vol. 12, nos. 1/2, p. 59-65. Kase, T. and Hayami, I., 1992: Unique submarine cave mollusc fauna: composition, origin and adaptation. Journal of Molluscan Studies, vol. 58, part 4, p. 446-449. Kase, T. and Kinjo, H., 1996. A nassariid gastropod from the sub- marine caves of Okinawa, Japan and Bohol, Philippines: taxo- nomic status of Nassa cinnamomea A. Adams, 1852. Venus (Japan Journal of Malacology), vol. 55, no. 3, p. 199-205. Kermack, K.A. and Haldane, J.B.S. 1950. Organic correlation and allometry. Biometrika, vol. 37, p. 30-41. Kuhn, O., 1949: Lehrbuch der Paldozoologie, 326 p. E. Schweizer- bart, Stuttgart. Lee, D.E. and Wilson, J.B., 1979: Cenozoic and Recent rhynchonellide brachiopods of New Zealand: Systematics and variation in the genus Notosaria. Journal of the Royal Society of New Zealand, vol. 9, no. 4, p. 437-463. Logan, A. and Zibrowius, H., 1994: A new genus and species of thynchonellid (Brachiopoda, Recent) from submarine caves in the Mediterranean Sea. Marine Ecology, vol. 15, no. 1, p. 71-88. Manceñido, M.O., 1997: Mesozoic brachiopods, living fossils and deep sea refuges. Ameghiniana, vol. 34, no. 1, p. 123. Mancenido, M.O. and Owen, E.F., 1996: Post-Paleozoic rhyncho- nellides: an overview. In, Copper, P. and Jin, J. eds., New brachiopod genus from submarine caves Brachiopods, Proceedings of the Third International Brachiopod Congress, Sudbury, Canada 1995, p. 368. A.A. Balkema, Rotterdam, Brookfield. Mancenido, M.O. and Owen, E.F., 2000: Post-Paleozoic Rhyncho- nellida (Brachiopoda): classification and evolutionary back- ground. /n, Brunton, H., Cocks, R. and Long, S. eds., Brachiopods: Past and Present: Proceedings of the Millennium Brachiopod Congress, p. 189-200. Systematics Association, Special Volumes. Taylor and Francis, London. Mancenido, M.O. and Walley, C.D., 1979: Functional morphology and ontogenetic variation in the Callovian brachiopod Septirhynchia from Tunisia. Palaeontology, vol. 22, no. 2, p. 317-337. Motchurova-Dekova, N., 2001: Taxonomic and phylogenetic as- pects of the shell ultrastructure of nine Cretaceous rhynchonellide brachiopod genera. Paleontological Research, vol. 5, no. 4, p. 319-330. Popoy, A.M., 1978: On the technique of skeletal structure investiga- tions in marine shell-bearing invertebrates and calcareous algae. Biologia Morya, vol. 4, p. 87-89. (in Russian) Raduloviè, V., 1991: Middle Jurassic brachiopods of Laz (Yugoslav part of of the Carpatho-Balkan arch). Paleontologia Jugosla- vica, vol. 40, p. 1-36. Saito, M., Endo, K. and Cohen, B.L., 2001: Molecular phylogenetics and evolution of long-looped brachiopods. Jn, Brunton, H., Cocks, R. and Long, S. eds., Brachiopods: Past and Present: Proceedings of the Millennium Brachiopod Congress, p. 129-138. Systematics Association, Special Volumes. Taylor and Francis, London. Saito, M., Motchurova-Dekova, N. and Endo, K. 2000: Recent brachiopod fauna from the submarine caves of Okinawa, Japan. In, Brunton, H., ed., The Millennium Brachiopod Congress, Abstracts, 10-14 July 2000, p. 77. The Natural History Museum, London. Simon, E. and Willems, G., 1999: Gwynia capsula (Jeffreys, 1859) and other Recent brachiopods from submarine caves in Croatia. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Biologie, vol. 69, p. 15-21. Surlyk, F., 1972: Morphological adaptations and population struc- tures of the Danish Chalk brachiopods. Biologiske Skrifter, K. Danske Videnskabernes Selskab, vol. 19, p. 1-57. Tabuki, R. and Hanai, T., 1999: A new sigillid ostracod from sub- marine caves of the Ryukyu islands, Japan. Palaeontology, vol. 42, no. 4, p. 569-593. Williams, A., 1971: Comments on the growth of the shell of articu- late brachiopods. /n, Dutro, J. T., Jr., ed., A Paleontological Tribute to A.G. Arthur Cooper. Smithsonian Contributions to Paleobiology, no. 3, p. 47-67. Williams, A., 1997: Shell structure. Jn, Kaesler, R. L. ed., Treatise on Invertebrate Paleontology. Part H. Brachiopoda, vol. 1, p. 267-320, The Geological Society of America, New York, and University of Kansas Press, Lawrence. Williams, A., Carlson, S.J., Brunton, C.H.C., Holmer, L.E. and Popov, L.E., 1996: A supra-ordinal classification of the Brachiopoda. Philosophical Transactions of the Royal Society of London, Series B, vol. 351, p. 1171-1193. Zezina, O.N., 1981: Recent deep-sea Brachiopoda from the Western Pacific. Galathea Report (Scientific Results of the Danish Deep-Sea Expedition Round the World 1950-52), Copenhagen, vol. 15, p. 7-20. 319 Paleontological Research, vol. 6, no. 3, pp. 321-327, September 30, 2002 © by the Palaeontological Society of Japan First finding of an articulated actinopterygian skeleton from the Upper Devonian of Siberia and a reappraisal of the family Moythomasiidae Kazantseva, 1971 (Osteichthyes) ARTEM M. PROKOFIEV Department of Fishes and Fish-like Vertebrates, Paleontological Institute (PIN), Russian Academy of Science, Profsoyuznaya Street, 123, Moscow 117997, Russia (e-mail: alopat@paleo.ru) Received January 31, 2002; Revised manuscript accepted July 5, 2002 Abstract. Krasnoyarichthys jesseni gen. et sp. nov. is described from the Upper Devonian (Famennian) of Western Siberia. It is the first finding of a Devonian actinopterygian in Siberia. This new genus is closely related to Moythomasia, Mimia and Kentuckia, but differs from those genera in the relative position of the fins, longer pelvic fin base and other dermal roof bones and scales characters in combination. The family Moythomasiidae with the above-mentioned genera and possibly Orvikuina is re-diagnosed and compared. Key words: Actinopterygii, Moythomasiidae, systematics, Upper Devonian, Western Siberia. Introduction Actinopterygian remains from the Devonian are known usually by isolated scales and disarticulated bones, or by highly incomplete fragments of skeletons; more or less completely articulated specimens are rare. Such remains are known from Western Europe and the Baltic region of Central Europe, Spitzbergen, Afghanistan, North and South America and Australia (Agassiz, 1833-1844; Woodward and White, 1926; Gross, 1942, 1950, 1953; Lehman, 1947; Casier, 1952, 1954; Gardiner, 1963; Berg er al, 1964; Jessen, 1968; Schultze, 1968; Gardiner and Bartram, 1977; Pearson and Westoll, 1979; Blieck er al., 1982; Janvier and De Melo, 1987; Long, 1988; Gagnier er al., 1989; Taverne, 1997). Only isolated scales identified as cf. Moythomasia sp. were found in Afghanistan (Blieck er al., 1982) and no more or less completely articulated specimens of Devonian actinopterygians were described from Asia. However, a collection of the Paleontological Institute (PIN) in Moscow includes a single nearly complete skeleton from the Upper Devonian deposits of the Krasnoyarski Krai in Western Siberia. This specimen shares many similarities with the genus Moythomasia Gross but differs from the latter in sev- eral other respects (see below). In the present paper it is described as a new genus and species, Krasnoyarichthys jesseni. The family Moythomasiidae Kazantseva, 1971 is reappraised as a consequence of the description of the new taxon. Notes on geography and stratigraphy The fossil site is situated 150 km westward from Krasnoyarsk close to Nazarovo City in the southwestern part of the Krasnoyarski Krai (Figure 1). In an abandoned quarry near the Atshinsk-Abakan railroad, brown sand- stones are exposed interrupted by calcareous alveolites with rare concretions. These layers belong to the Famennian Stage (Sidorenko, 1964). The specimen was found in a concretion. Systematic paleontology Order Cheirolepiformes (sensu Kazantseva-Selezneva, 1977) Family Moythomasiidae Kazantseva, 1971 Emended diagnosis. — Relatively small fishes with fusiform body. Frontal bones as long as or 1.7 times longer than parietals. Both intertemporal and supra- temporal present [intertemporal is not documented in Kentuckia, however, it might be present according to its re- construction (Rayner, 1951, p. 56)]. Supratemporal not contacting frontal. Antorbital and single supraorbito- infraorbital present. Postorbital portion of maxillary well 322 Artem M. Prokofiev Figure. 1. Map of a section of Western Siberia illustrating the location of the fossil site (A). Scale bar 75 km. developed. Mandibular suspension oblique. Both dermohyal and epipreopercle present, completely separat- ing opercle and preopercle. Preopercle with two branches. Opercle larger than subopercle. Skull roofing bones orna- mented with longitudinal ridges of ganoine. All fins with minute fringing fulcra and with rays articulated and distally bifurcating. Dorsal and anal fins completely or partially opposite to one another; anal fin originating on the same level as the dorsal fin origin or behind it. Pelvic fin base shorter than anal fin base. Caudal fin heterocercal. Dorsal and ventral ridge scutes present. Scales orna- mented with diagonal ridges which end on the posterior scale margins as a series of serrations; all body scales with peg-and-socket articulations. Included genera.—Moythomasia Gross, 1950 (Middle- Upper Devonian, Western and Central Europe, ?Afghanistan, Western Australia); Kentuckia Rayner 1951 (Lower Carboniferous, USA); Mimia Gardiner and Bartram 1977 (Upper Devonian, Western Australia); Krasno- yarichthys, gen. nov. (Upper Devonian, Western Siberia); possibly also Orvikuina Gross, 1953 (Middle Devonian, Central Europe), which is known only by isolated scales. Krasnoyarichthys gen. nov. Type species. — Krasnoyarichthys jesseni, sp. nov; monotypic genus. Etymology.—From the Krasnoyarsky Krai, and-ichthys (Greek), fish; masculine. Diagnosis.—Same as that of the type species. Krasnoyarichthys jesseni sp. nov. Holotype.—PIN, nr. 4890-1, nearly complete skeleton lacking snout, anterior parts of the skull roof and of the cheek, and caudal fin, with poorly preserved cephalic sen- sory canals and limits of scales on the caudal peduncle; sin- gle plate (Figure 2a); Western Siberia, Krasnoyarski Krai, vicinity of Nazarovo City, Preobrazhensky Village, quarry near railroad; Upper Devonian (Famennian). Species is known only by the holotype. Ethymology.—Species named in honour of Hans Jessen for his great contribution to palaeoichthyology. Diagnosis. — Relatively small fishes reaching a total length of about 10 cm. Maximum body depth contained A Devonian articulated actinopterygian 323 clav Figure. 2. Krasnoyarichthys jesseni gen. et sp. nov., Upper Devonian (Famennian) of Krasnoyarski Krai (Siberia). a. Holotype, PIN, nr. 4890-1 (natural size). b. Reconstruction of the lateral view. c. Reconstruction of the postorbital part of the skull and of the pectoral girdle (as the cephalic sensory canals are poorly preserved they are omitted in figure). d. Isolated scale from left side of body. Scale bars 1 mm. Abbreviations: br, branchiostegal rays; cl, cleithrum; clav, clavicle; dhy, dermohyal; epop, epipreopercle; ext, extrascapular; fr, frontal; it, intertemporal; mx, maxil- lary; op, opercle; pa, parietal; pop, preopercle; ptt, posttemporal; scl, supracleithrum; sop, subopercle; st, supratemporal. 324 Artem M. Prokofiev approximately 3.5 times in the total length. Extrascapular single on each side of skull, two times larger than long. Postorbital portion of maxillary deep. Opercle 1.5 times deeper than long. Subopercle 1.5 times smaller than opercle. Pelvic fin originating equidistantly from the pec- toral and anal fin origins; pelvic base only 1.5 times shorter than anal fin base. Dorsal fin origin in front of that of anal fin; posterior edge of anal fin noticeably behind that of dorsal fin. Approximate numbers of fin-rays: dorsal 40, anal 40, pelvic 30, pectoral 30. Roofing bone ornament consisting of coarse longitudinal and diagonal ridges of ganoine. Scales rhomboidal, ornamented by up to 10 di- agonal ridges which end on posterior scale margins as se- ries of serrations. Middle trunk scales approximately twice, or less, deeper than long. Dorsal and ventral ridge scutes weakly developed. Description (Figure 2).—Besides the characters given in the diagnosis there are several additional features. The es- timated standard length of the holotype is approximately 100 mm. Measurements in mm: length from the posterior border of the cleithrum to the caudal base 76, length from the posterior border of the cleithrum to the dorsal fin origin 41, the same length to the anal fin origin 46, the same length to the pelvic fin origin 24, distance between the pec- toral and pelvic fin origins 26, distance between the pelvic and anal fin origins 26, maximum body depth 32, caudal peduncle depth 8, dorsal fin base length 16, anal fin base length 16, pelvic base length 11, dorsal fin height 20, anal fin height 18, pelvic fin height 9, pectoral fin height 11. The transverse rows of scales on the body are approxi- mately 50 in number. There are 16 longitudinal rows of scales on the body. The dorsal ridge scutes are continuous from the occiput to the dorsal fin origin, and between the dorsal and caudal fins. The ventral ridge scutes are be- tween pectoral and pelvic fins, and between anal and caudal fins; at least three slightly enlarged ventral scales are pre- sent before anal fin origin. Discussion Based on its similar body form, position of the fins, cra- nial roofing bones and structure of the scales Krasnoyarichthys undoubtedly belongs to the family Moythomasiidae. However, the new genus differs from both Moythomasia and Mimia in the relative position of the dorsal and anal fins (dorsal fin origin and ending in front of those of anal fin vs. dorsal and anal fins opposite one an- other in the compared genera) and in the slightly longer pelvic fins (1.5 times in the length of the anal fin base vs. twice in the compared genera). It further differs from Moythomasia in the presence of a single extrascapular on each side of the skull (vs. two in Moythomasia), which is noticeably larger than long (the extrascapulars are approxi- mately as large as long in Moythomasia). Krasno- yarichthys is distinguished from Mimia in the middle trunk scales being no more than twice times deeper than long (vs. 3-4 times deeper than long in Mimia) and in the much less prominent ridge scutes. The new genus differs from Kentuckia, which is known only by the skull, in the opercle 1.5 times (vs. 2.5 times) deeper than long and 1.5 times (vs. twice) larger than the subopercle, and in the deep postorbital portion of the maxillary. The new genus is dis- tinct from Orvikuina, which is known only by isolated scales, in having scales deeper than long (vs. much longer than deep), bearing up to 10 serrations (vs. 2-3 in Orvikuina). The family Moythomasiidae is neglected in the literature. The genus Moythomasia together with Kentuckia Rayner and Stegotrachelus Woodward and White were placed by Gardiner (1963) in the family Stegotrachelidae. Later, Gardiner and Bartram (1977) added the genus Mimia to this family. However, the subsequent reconstruction of Moythomasia published by Jessen (1968) shows numerous distinctions between the latter and Stegotrachelus. Kazantseva (1971) indicated the principal differences be- tween Stegotrachelus and Moythomasia were in the struc- ture of the bones of the cheek region (both dermohyal and epipreopercle are absent in Stegotrachelus) and transferred Moythomasia and Kentuckia to another family, the Moythomasiidae. Unfortunately, this decision was never discussed by other authors (Gardiner, 1984; Gardiner and Schaeffer, 1989; Taverne, 1997). In their phylogenetic analysis of the basal actinopterygians, Gardiner and Schaeffer (1989) placed Mimia and Tegeolepis into a «Mimia group», and Moythomasia, Howqualepis and Stegotrachelus into a «Moythomasia group»; the «Mimia group» was considered as a sister taxon for the «Moythomasia group» plus other actinopterygians excluding Cheirolepis and the polypterids. Unfortunately, this analysis is based on many characters not preserved in numerous paleoniscoid groups known to date (i.e. characters of the neurocranium, pectoral and pel- vic girdles, axial skeleton, etc.), and their phylogenetic sig- nificance therefore needs further elucidation. In our opinion, the structure of the dermal skull bones provides the most important data for elucidation of paleoniscoid re- lationships, because they are always preserved in fossils and indicate the different evolutionary trends (Kazantseva- Selezneva, 1981). The only dermal bone character men- tioned by Gardiner and Schaeffer (1989) as common to Stegotrachelus and Moythomasia is the absence of a true dermopterotic. The Cheirolepis, Mimia and Moythomasia groups of Gardiner and Schaeffer (1989) have no dermopterotic but two bones (intertemporal and supratemporal) in this region of the skull. However, in Gardiner’s (1963: 296, fig. 12) reconstruction of the A Devonian articulated actinopterygian 325 Stegotrachelus skull the intertemporal is not figured. The other dermal skull characters of Stegotrachelus [absence of accessory opercular bones, long supratemporal (or dermopterotic) contacting frontal, small parietals, very nar- row extrascapulars, numerous suborbitals] clearly distin- guish the latter from the other members of the above- mentioned groups. According to Kazantseva-Selezneva (1981), the family Moythomasiidae seems to be closely related to the Cheirolepididae and Cosmoptychiidae rather than to the Stegotrachelidae. On the other hand, Taverne (1997) considered all the Devonian genera, Cheirolepis and Dialipina excluded, as the sister group of «polypteri- forms». This opinion is doubtful judging from the close relationships between the Polypteridae and the peculiar Triassic Scanilepiformes (Sytchevskaya, 1999), and Lund’s (2000) cladistic analysis of the polypteriforms which has specified sister relationships between the polypterids plus guildayichthyiforms and the platysomiforms. According to Kazantseva (1971, 1974a, 1974b, 1977, 1981), the presence or absence of the dermohyal and epipreopercle is highly significant for the higher classifica- tion of the paleoniscoid fishes and indicates different types of breathing. Kazantseva-Selezneva (1977, 1981) divided the order Palaeonisciformes into three separate orders (Cheirolepiformes, Elonichthyiformes and Palaeonisci- formes s. str.), of which both the dermohyal and epipreopercle are present only in the Cheirolepiformes. Among the Cheirolepiformes, the structure of the cranial roofing bones of the Moythomasiidae is similar to that in the Cheirolepididae. Both families have a single supraorbito-infraorbital, large parietals, the supratemporal lacking contact with the frontal bone, and the preopercle and opercle completely separated by the dermohyal and epipreopercle. However, the Cheirolepididae sharply dif- fer from the Moythomasiidae in the structure of their scales, which are minute, square, not overlapping, with an internal boss, and quite similar to those of the acanthodians in the Cheirolepididae (contrary to the typical palaeoniscoid scales of the Moythomasiidae). The other distinctions include the presence of a separate antorbital in the Moythomasiidae [vs. completely fused with the premaxillary into the rostro-premaxillo-antorbital bone (Gardiner, 1963; Pearson and Westoll, 1979)], the anal fin origin opposite the dorsal fin origin or just behind it in the Moythomasiidae (vs. in advance of the dorsal fin origin in the Cheirolepididae), the pelvic base shorter than the anal base, and the ridge scutes present in the Moythomasiidae (in contrast to the reverse conditions in the Cheirolepidi- dae) and the body form less elongate in the Moythomasii- dae. In our opinion, the family Moythomasiidae is valid and closely related to the Cheirolepididae. Such cranial char- acters as long parietals, presence of intertemporals, supratemporals lacking contact with frontal bones, single infraorbito-suborbital, and dermohyal and epipreopercle completely separating the preopercle from the opercle characterising both these families seem to be primitive, ac- cording to the undoubted position of Cheirolepis as the most primitive actinopterygian (Berg er al., 1964; Pearson and Westoll, 1979; Patterson, 1982; Lauder and Liem, 1983; Gardiner and Schaeffer, 1989; etc.). The orbit relatively larger with regard to the overall body size, the shorter body, the short-based pelvic fins, the presence of peg-and-socket scale articulations on the body scales and ridge scutes on the body contours indicate the advanced status of the Moythomasiidae. The peculiar Australian genus Howqualepis has small orbits, a long body, and long- based pelvic fins, and it lacks dorsal and ventral ridge scutes, which establishes its similarity to Cheirolepis; how- ever, the supratemporal has contact with the frontal and the parietals are two times shorter than the frontals in Howqualepis (Long, 1988). All these characters undoubt- edly exclude Howqualepis from the Moythomasiidae. The other Devonian genera (Dialipina and Ligulalepis, which are known only by isolated scales; Osorioichthys and Tegeolepis) sharply differ from the Moythomasiidae in the cranial and scale characters and the two latter belong to other families (Osorioichthyidae and Tegeolepididae, re- spectively) (Schultze, 1968; Gardiner, 1963, 1967; Kazantseva-Selezneva, 1977, 1981). Conclusion Krasnoyarichthys jesseni gen. et sp. nov. from the Upper Devonian (Famennian) of Western Siberia belongs to the family Moythomasiidae, and differs from the other mem- bers of this family in the following combination of charac- ters: single extrascapular on each side of the skull, which is noticeably larger than long; deep postorbital portion of maxillary; opercle 1.5 times deeper than long and 1.5 times larger than the subopercle; dorsal fin origin in front of that of anal fin; posterior edge of anal fin noticeably behind that of the dorsal fin; pelvic fin base 1.5 times in the anal fin base length, and middle trunk scales no more than twice deeper than long. The family Moythomasiidae presently is recognized as distinct and closely related to the Cheirolepididae, on the basis of their similar cranial roofing bone characters. However, the moythomasiids seem to be more advanced than the cheirolepidids judging from their relatively larger orbit with regard to the overall body size, shorter body, short-based pelvic fins, the presence of peg- and-socket scale articulations on the body scales and ridge scutes on the body contours. The moythomasiids and other Devonian actinopterygians are recorded in marine sediments only (Jessen, 1968; Schultze, 1968; Gardiner, 1984; Janvier and De Melo, 326 Artem M. Prokofiev 1987; etc.), and Sidorenko (1964) noted a marine origin for the deposits, in which the holotype of Krasnoyarichthys subsequently was found. This taxon is the first finding of the Moythomasiidae in Siberia. Further investigations of the Preobrazhensky fossil site are needed since they have special interest for the morphology, taxonomy and paleobiogeography of Devonian actinopterygians. Acknowledgements I wish to thank Cecile Poplin (Museum National d’ Histoire Naturelle, Paris) for helpful criticism of an earlier version of the manuscript. References Agassiz, L., 1833-1844: Recherches sur les Poissons Fossiles. Petitpierre, Neuchätel et Soleure, 5 vols, 1420 pp., with supple- ments. Berg, L.S., Kazantseva, A.A. and Obruchev, D.V., 1964: Nadotryad Palaeonisci. Paleoniski [Supraorder Palaeonisci]. In, Orlov, Yu.A. (ed.) Osnovy paleontologii. Beschelyustnye i ryby [Principles of Paleontology. Agnathans and Fishes], p. 336-370. Nauka, Moscow. (in Russian) Blieck, A., Janvier, P., Lelièvre, H., Mistiaen, B. and Montenat, C., 1982: Vertébrés du Dévonien supérieur d’ Afghanistan. Bulletin du Muséum National d Histoire Naturelle, série 4, sec- tion C, vol. 4, nos. 1-2, p. 3-19. Casier, E., 1952: Contributions à l’étude des poissons fossiles de la Belgique. X. Un palaeoniscoide du Famennien inférieur de la Fagne: Stereolepis marginis n. gen., n. sp. Bulletin de l’Institut Royal des Sciences Naturelle de Belgique, vol. 28, no. 47, p. 1-17. Casier, E., 1954: Contributions à l’étude des poissons fossiles de la Belgique. XI. Note additionelle relative 4 «Stereolepis» (= Osorioichthys nov. nom.) et à l’origine de l’interoperculaire. Bulletin de l’Institut Royal des Sciences Naturelle de Belgique, vol. 30, no. 2, p. 1-12. Gagnier, P.Y., Paris, F., Rachebœuf, P., Janvier, P. and Suarez- Riglos, M., 1989: Les vertébrés dévoniens de Bolivie: donnée biostratigraphiques et anatomiques complémentaires. Bulletin de I’ Institute Français d’ Etudes Andines, vol. 176, p. 269-297. Gardiner, B.G., 1963: Certain palaeoniscoid fishes and the evolution of the snout in actinopterygians. Bulletin of the British Museum (Natural History), Geology Series, vol. 8, no. 6, p. 257-325, 2 pls. Gardiner, B.G., 1967: Further notes on palaeoniscoid fishes with a classification of the Chondrostei. Bulletin of the British Museum (Natural History), Geology Series, vol. 14, no. 5, p. 146-206. Gardiner, B.G., 1984: The relationships of the palaeoniscid fishes, a review based on new specimens of Mimia and Moythomasia from the Upper Devonian of Western Australia. Bulletin of the British Museum (Natural History) Geology Series, vol. 37, no. 4, p. 173-428. Gardiner, B.G. and Bartram, A.W.H., 1977: The homologies of ven- tral cranial fissures in osteichthyans. In, Andrews, SM, Miles, R.S. and Walker, A.D. eds., Problems in Vertebrate Evolution, p. 227-245. Academic Press, London. Gardiner, B.G. and Schaeffer, B., 1989: Interrelationships of lower actinopterygian fishes. Zoological Journal of the Linnean Society of London, vol. 97, no. 2, p. 135-187. Gross, W., 1942: Die Fischfaunen des baltischem Devons und ihre biostratigraphische Bedeutung. Korrespondenzblatt des Naturforscher-Vereins zu Riga, vol. 64, p. 373-436. Gross, W., 1950: Umbenennung von Aldingeria Gross (Palaeoniscidae; Oberdevon) in Moythomasia n. nom. Neues Jahrbuch für Mineralogie, Geologie und Paläontologie, Monatshefte, 1950 (5), p. 145. Gross, W., 1953: Devonische Palaeonisciden-Reste in Mittel- und Osteuropa. Paläontologische Zeitschrift, vol. 27, nos. 1-3, p. 85-112, pls. 4-7. Janvier, P. and De Melo, J.H.G., 1987: Late Devonian actinopterygian scales from the Upper Amazon Basin, Northwestern Brazil. Anais da Academia Brasileira de Ciencias, vol. 59, no. 3, p. 213-218. Jessen, H., 1968: Moythomasia nitida Gross und M. cf. striata Gross, devonische Palaeonisciden aus dem oberen Plattenkalk der Bergisch-Gladbach-Paffrather Mulde (Rheinisches Schiefergebirge). Palaeontographica Abteilung A, Paläozoo- logie-Stratigraphie, vol. 128, nos. 4-6, p. 87-114, pls. 11-17. Kazantseva, A.A., 1971: K sistematike Palaeonisciformes [On the systematics of Palaeonisciformes]. Trudy Paleontologic- heskogo Instituta Akademii Nauk SSSR, vol. 130, p. 160-167. (in Russian) Kazantseva, A.A., 1974a: Mekhanizm dychaniya paleoniscov i ego evolyutsia v podklasse Actinopterygii [Mechanism of breathing of the paleoniscoids and its evolution in the subclass Actinopterygii]. Voprosy Ikhtiologii, vol. 14, no. 1, p. 3-19. (in Russian) Kazantseva, A.A., 1974b: O morfofunktsionalnych osobennostyach dychatelnogo apparata Palaeonisci [On the morphofunctional peculiarities of the breathing apparatus of the Palaeonisci]. Paleontologicheskij Zhurnal, 1974, no. 4, p. 74-85. (in Russian) Kazantseva-Selezneva, A.A., 1977: K sistematike i filogenii otryada Palaeonisciformes [On the systematics and phylogeny of the order Palaeonisciformes]. Jn, Menner, V.V. ed., Ocherki po filogenii i sistematike beschelyustnych i ryb [Essays on the Phylogeny and Systematics of the Agnathans and Fishes], p. 98-115. Nauka, Moscow. (in Russian) Kazantseva-Selezneva, A.A., 1981: Phylogeniya nizschich lucheperych [Phylogeny of the lower actinopterygians]. Voprosy Ikhtiologii, vol. 21, no. 4, p. 579-594. (in Russian) Lauder, G.V. and Liem, K.F., 1983: The evolution and interrelation- ships of the actinopterygian fishes. Bulletin of the Museum of Comparative Zoology, Harvard University (Cambridge), vol. 150, no. 3, p. 95-194. Lehman, J.-P., 1947: Description de quelques exemplaires de Cheirolepis canadensis (Whiteaves). Kungliga Svenska Vetenskapsakademiens Handlingar, Stockholm, vol. 24, no. 4, p. 1-40, pls. 1-9. Long, J., 1988: New palaeoniscoid fishes from the Late Devonian and Early Carboniferous of Victoria. Memoirs of the Association of Australasian Palaeontologists, vol. 12, p. 1-64. Lund, R., 2000: The new actinopterygian order Guildayichthyiformes from the Lower Carboniferous of Montana (USA). Geodiversitas, vol. 22, no. 2, p. 171-206. Patterson, C., 1982: Morphology and interrelationships of primitive actinopterygian fishes. American Zoologist, vol. 22, no. 2, p. 241-259. Pearson, D.M. and Westoll, T.S., 1979: The Devonian actinopterygian Cheirolepis Agassiz. Transactions of the A Devonian articulated actinopterygian Royal Society of Edinburgh, vol. 70, nos. 13-14, p. 337-399. Rayner, D.H., 1951: On the cranial structure of an early palaeoniscid, Kentuckia gen. nov. Transactions of the Royal Society of Edinburgh, vol. 62, pt. 1, no. 3, p. 55-83. Sidorenko, A.V. ed., 1964: Geologiya SSSR. T. XLIV. Zapadno- Sibirskaya Nizmennost. Ch. I. Geologicheskoye opisaniye [Geology of the USSR. Vol. XLIV. Western Siberian Lowland. Pt. I. Geological Description], 550 p. Nedra, Moskow. (in Russian) Schultze, H.-P., 1968: Palaeoniscoidea-Schuppen aus dem Unterdevon Australiens und Kanadas und aus dem Mitteldevon Spitzbergens. Bulletin of the British Museum (Natural History), Geology Series, vol. 16, no. 7, p. 343-368. Sytchevskaya, E.K., 1999: Freshwater fish fauna from the Triassic of Northern Asia. /n, Arratia, G. and Schultze, H.-P. eds., Mesozoic Fishes 2-Systematics and Fossil Record, p. 445-468. Taverne, L., 1997: Osorioichthys marginis, «Paléonisciforme» du Famennien de Belgique, et la phylogénie des Actioptérygiens devoniens (Pisces). Bulletin de l'Institut Royal des Sciences Naturelle de Belgique, Sciences de la Terre, vol. 67, p. 57-78. Woodward, A.S. and White, E.I., 1926: The fossil fishes of the Old Red Sandstones of the Shetland Islands. Transactions of the Royal Society of Edinburgh, vol. 54, pt. 3, no. 12, p. 567-572, pl. 3. 327 Errata 329 In the article by Takashi Matsubara (Paleontological Research, Vol. 6, No. 2, pp. 127-145), the following corrections should be made: page 130 130 130 130 130 130 130 141 141 142 143 144 144 144 table/column line read Table 1 9 Acila (Truncacila) cf. nagaoi Table 1 11 Glycymeris (Glycymeris) sp. Table 1 15 Chlamys (Leochlamys) namigataensis Table 1 16 Crassostrea sp. Table 1 17 Lucinidae gen. et sp. indet. Table 1 18 Cyclocardia sp. Table 1 20 Megangulus maximus (Nagao) Left at [delete] Left 45 Formation Left 4 Activities, Hyogo/Himeji Institute Right 7 Editio duodecima Right 21 siciliale Right 23 Tome 2 Right 30 Pars secunda, viii+199 p. for Acila (Truncacila) cf. nagaoi Glycymeris (glycymeris) sp. Chlamys (leochlamys) namigataensis Crassastrea sp. Luchinidae gen. et sp. indet. Cyclocardin sp. Megangulus maximus (Nagano) Fo rmation Activities, Hyogo Himeji Institute Editio decima Siciliale Tom 2 Pars Secunda, viii-199p. 330 A GUIDE FOR PREPARING MANUSCRIPTS PALEONTOLOGICAL RESEARCH is decicated to serving the interna- tional community through the dissemination of knowledge in all areas of paleontological research. The journal publishes original and unpublished articles, normally not exceeding 24 pages, and short notes, normally less than 4 pages, without abstract. 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(in Russian) r070700000..00.0000000000000700.000.00000.00 00.000, DDS OSD SDS OSCO LO LO STO SSDS 0110000000000 LOL LOLOL OLE LOL LLL LLL LLL LLL LLL LLL LLL LLL LL LL LLL LLL ELL LLL LLL LLL LLL ELLE LLL LLL LLL LO LE LOLOL Z a OF 1521 FIZiz, 2003 1 H24H (4)~26H8 (A) CRRA SARE APE THIEO PETC 3. 1248 (@) YY RVYODAELUT | BCR SHO RAR: tha A CPs dt 2f° PR il À, £10258 +) Cy vy tY9A [che BERUF TOHR EIKE — 7 L'— UR Hekofm- : HA FEHB) DHHANES. KS, BHO LASHYH) id, 20027F11H 29H (4) Cd. MMHPLUASOPSRERBANORICMERCHHT ZARA Cie 7 0 © 2 7 9 —, OHP, 354 FRE) OAI DUTEHAELT FEU. ©2008 F FREI, 2003 6 A FORMATER CHES NET. VY RYO [EMS EMFERDSEIA:HEN BR À -INRE - EVR) 2ABÉTECS. HO LAS] D 112003Æ 5 H 2H (4) OFETS. COlD, RES E LOREFENE 0 & LD, 20027 12A MAE CLTÉÈRETHAHIDE FEU, AmB: VY RYDABOMRLASHE (HABBO LAA li TERRE Padé TERSEH FAW. E-mail ? 7 7 » 7A COM LIAS IIIA ELTEUHUTHOERA. 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SMITHSONIAN INSTITUTION LIB 3 9088 01429 0 NL! wl 191 ISSN 1342-8144 Paleontological Research Vol. 6, No. 3 September 30, 2002 CONTENTS Rajeev Patnaik: Enamel microstructure of some fossil and extant murid rodents of India»: - Yutaka Honda: Paleobiogeographic significance of Trominina hokkaidoensis (Hayasaka and Uozumi) (Gastropoda: Buccinidae) from the basal part of the Tanami Formation (Oligocene) of the Kii Peninsula, southern Japan ::-:-:----:::.......................4M 0... Gengo Tanaka and Noriyuki Ikeya: Migration and speciation of the Loxoconcha japonica species group (Ostracoda) in East Asia -----------............. "ANT... Guang R. Shi, Shuzhong Shen and Jun-ichi Tazawa: Middle Permian (Guadalupian) brachiopods from the Xiujimgingi area, Inner Mongolia, northeast China, and their palaeobiogeographical and palaeogeographical significance :-:--------.........................:......... nun Neda Motchurova-Dekova, Michiko Saito and Kazuyoshi Endo: The Recent rhynchonellide brachiopod Parasphenarina cavernicola gen. et sp. nov. from the submarine caves of Okinawa, Artém M. Prokofiev: First finding of an articulated actinopterygian skelton from the Upper Devonian of Siberia and a reappraisal of the family Moythomasiidae Kazantseva, 1971 (Osteichthyes):-:----- Errata: Article by Takashi Matsubara in Vol. 6, No. 2 hoc Oar: Ci Oo RUN OO DD. DO ro A Ola 0000 | Figure 3. Carthaginites yamashitai sp. nov. Stutures on the flank of three successive whorls of GK. H8539 (holotype), x8. because it has a small and feebly ornamented shell and abnormal configuration of the suture. N. bayardense Cobban, Hook and Kennedy (1989, p. 60, figs. 95R, 96R) from the same zone may be another species of Carthagi- nites, although its suture was not illustrated. Occurrence.—The holotype and the two paratypes of this species came from Loc. Ik 1103 (for the location see Carthaginites yamashitai sp. nov. Lateral views (A-E anticlockwise turned) and basal view (F) of GK. H8539 (holotype), x3. Matsumoto and Takahashi, 2001, fig. 4), where the middle Cenomanian Zone of Calycoceras (Newboldiceras) asiaticum Zone is exposed. Carthaginites yamashitai sp. nov. Figures 2 and 3 Material.—Holotype is GK. H8539 (Figure 2) collected by Minoru Yamashita from a cutting, SE of Poronai, Mikasa district and later donated to the Kyushu University Museum. This is well preserved, but no other specimens are available. Diagnosis. —Small flat-sided turricone, with estimated apical angle of 18°. Young whorls look almost smooth, but for faint spiral depression at midflank and numerous minute tubercles aligned immediately above the lower whorl seam. In later growth stages blunt major tubercles developed above the spiral depression and minor ones along the lower whorl seam. The latters are pointed at their top immediately above the lower whorl seam but 360 Tatsuro Matsumoto clavate at their base, forming a wavy spiral line. Thus, a kind of double feature is shown. Configuration of the sutural elements abnormal in showing the entire L and parts of the saddles E/L and L/U on the exposed whorl face; E almost entirely unexposed on the flank (Figure 3). Description.—This single available specimen consists of 9 whorls, without the youngest part and the destroyed last portion of the body chamber. It is 27 mm in total height, and the diameter of the last whorl is 10 mm. Each whorl is trapezoidal in lateral view, with the larger dimension along the lower row of small tubercles. For instance, the ratio of height to lower diameter is 0.45 and of height to upper diameter 0.50. The shallow spiral depression is better discernible on the internal mould. It is at about the midflank in young whorls and gradually shifted downward with growth. I notice a questionable feature that several minutely pointed upper tu- bercles are discernible in a part of the preserved first whorl (see Figure 2C, D). Whether this is a constant character or merely accidental cannot be decided without examining more specimens. In later growth stages major tubercles of the upper row may be somewhat bullate upward. The tubercles of the lower row are small but fairly distinctly pointed and slightly bullate upward. They are twice as numerous as the nodes of the upper row; for instance 30 against 15 in the whorl of the middle growth stage. They rest on a wavy spiral ridge which forms an edge between the flank and the lower face of the whorl. On the basal face of the pre- served last whorl a radial rib runs from each wave of the ridge toward the umbilicus with gentle curvature (Figure 2F). The suture on the flank of the successive three whorls is illustrated in Figure 3. Comparison. —This species is undoubtedly referred to Carthaginites on account of its small size, faint ornamenta- tion with a shallow spiral groove at about the midflank and the deviation of the siphuncle from the upper edge of the whorl flank inward below the upper whorl face as shown by the particular configuration of the sutural elements. The estimated apical angle of C. yamashitai is larger than that in C. kerimensis and C. asiaticus. As to the de- gree of minor sutural incisions, there is no significant dif- ference between C. yamashitai and C. krorzaensis or C. asiaticus, if the gradual change with growth is taken into consideration. The gradual change of ornamentation with growth in this species is analogous to that of C. asiaticus. The two species are distinguished by the difference in the whorl shape and the style of ornamentation. Occurrence.—The holotype was collected from the mid- dle Cenomanian Calycoceras (Newboldiceras) asiaticum Zone exposed at a cutting of a forestry road, about 3500 m S60° E from the Poronai colliery, Mikasa district. This fossil locality is marked in the official geological map “Iwamizawa” (Matsuno et al., 1964). I went there later but failed to obtain additional material. The fossiliferous bed is referred to the Mikasa Formation which consists mainly of sandy sediments of shallow sea facies. Concluding remarks (1) The genus Carthaginites Pervinquiere, 1907 was pre- viously represented by small and more or less incompletely preserved specimens of rare occurrence from Tunisia and Algeria. In addition to the original works of Pervinquiére (1907) and Dubourdieu (1953) the better preserved speci- mens from Hokkaido are taken into cosideration, and thus the diagnosis of the genus Carthaginites is given clearly in this paper. (2) The species previously called Neostlingoceras asiati- cum Matsumoto and Takahashi, 2000 is revised in this paper to Carthaginites asiaticus (Matsumoto and Takahashi, 2000) and redescribed with necessary amend- ment. Furthermore, Carthaginites yamashitai sp. nov. is established on a fine specimen collected by M. Yamashita. The above two species occurred in the middle Cenomanian Calycoceras (Newboldiceras) asiaticum Zone in the Mikasa district of central Hokkaido. (3) Morphologically and stratigraphically Carthaginites is intimately related to Neostlingoceras but differs in its smaller size, weaker ornamentation and especially by the deviated position of the siphuncle to the inner part of the whorl. (4) In view of the peculiar characters as mentioned above, Carthaginites is presumed to have had a peculiar mode of life, but this ecological problem is not treated in this paper and left for further investigation. Acknowledgements I am indebted to Minoru Yamashita for his supply of the valuable specimen of his collection to this study and also to Takemi Takahashi for his help in various aspects. W.A. Cobban kindly read the first draft of the paper with helpful suggestions. Photos are by courtesy of Tamio Nishida. Two anonymous referees helped me to improve the manu- script. References Cobban, W.A., Hook, S.C. and Kennedy, W.J., 1989: Upper Cretaceous rocks and ammonite faunas of southwestern New Mexico. New Mexico Bureau of Mines and Mineral Resources, Memoir 45, p. 1-137. Collignon, M., 1932: Les ammonites pyriteux de Il’ Albien superieur de Mont Raynaud à Madagascar. Annales Géologiques du Service de Mines, Madagascar, vol. 2, p. 2-36, pls. 1-4. Carthaginites from Hokkaido Dubourdieu, G., 1953: Ammonites nouvelles des Monts du Mellégue. Bulletin du Service de la Carte Geologique de l'Algérie (serie 1, Paléontologie), no. 16, p. 1-74, pls. 1-4. Gill, T., 1871: Arrangements of the families of Mollusks. Smithsonian Miscellaneous Collections, no. 227, p. i-xvi, 1- 49. Klinger, H.C. and Kennedy, W.J., 1978: Turrilitidae (Cretaceous Ammonoidea) from South Africa, with a discussion of the evo- lution and limits of the family. Journal of Molluscan Studies, vol. 44, p. 1-48. Lamarck, J.B.P.A. de Monet de, 1801: Systeme des animaux sans vertebres, 432 p. Paris. Matheron, P., 1842: Catalogue methodique et descriptif des corps organises fossiles du Departement des Bouches-du-Rhöne et lieux circonvoisins, 269 p. 41 pls., Marseille. Matsumoto, T. and Takahashi, T., 2000: Further notes on the turrilitid ammonoids from Hokkaido—Part 1. Paleontological Research, vol. 4, no. 4, p. 261-273. Matsumoto, T. and Takahashi, T., 2001: A study of Hypoturrilites (Ammonoidea) from Hokkaido. Paleontological Research, vol. 5, no. 4, p. 229-240. Matsuno, K., Tanaka, K., Mizuno, A. and Ishida, M., 1964: Iwamizawa. Explanatory Text of the Geological Map of Japan, Scale 1:50,000, p. 1-168 + 1-11. (in Japanese with English abstract) Pervinquiere, L., 1907: Etudes de paléontologie tunisienne, 1. Céphalopodes des terrains secondaires. Carte Géologique de la Tunisie, 430 p., atlas (27 pls.). Rudeval, Paris. Wiedmann, J., 1966: Stammesgeschichte und System der posttriadischen Ammonoideen, ein Uberblick, 1 Teil. Neues Jahrbuch fiir Geologie und Paldontologie, Abhandlungen, vol. 125, p. 49-79, pls. 1-2. Wright, C.W. and Kennedy, W.J., 1996: The Ammonoidea of the Lower Chalk, part 5. Monograph of the Palaeontographical Society, London, no. 601, p. 320-403, pls. 95-24. Zittel, K.A. von, 1884: Cephalopoda, /n, Zittel, K.A., Handbuch der Paldontologie, vol. 1, p. 329-522, Oldenbourg, Miinchen and Leipzig. 361 Paleontological Research, vol. 6, no. 4, pp. 363-384, December 31, 2002 © by the Palaeontological Society of Japan The Anthracotheriidae (Mammalia; Artiodactyla) from the Eocene Pondaung Formation (Myanmar) and comments on some other anthracotheres from the Eocene of Asia TAKEHISA TSUBAMOTO', MASANARU TAKAI', NAOKO EGI', NOBUO SHIGEHARA', SOE THURA TUN’, AYE KO AUNG’, AUNG NAING SOE’ AND TIN THEIN* ‘Primate Research Institute, Kyoto University, Inuyama, Aichi, 484-8506, Japan (e-mail: tsuba@pri.kyoto-u.ac.jp) "Department of Geology, University of Pathein, Pathein, Myanmar "Department of Geology, Dagon University, Yangon, Myanmar “Department of Geology, University of Yangon, Yangon, Myanmar Received May 9, 2002; Revised manuscript accepted October 7, 2002 Abstract. We reevaluate the classifications of the anthracotheres (Mammalia; Artiodactyla) from the latest middle Eocene Pondaung Formation (central Myanmar), mentioning other anthracotheres from the Eocene of Asia. The three anthracotheriid genera previously known from the Pondaung Formation, Anthra- cothema, Anthracokeryx, and Anthracohyus, are synonymized into Anthracotherium. As many as 13 species had been recognized in the Pondaung anthracotheres, but they are summarized into four species (Anthracotherium pangan, Anthracotherium crassum, Anthracotherium birmanicum, and Anthracotherium tenuis), based on the difference of M, size ( body size). Dental morphology in each species indicates high variation, and the four species are not separable based on their dental morphology. The dental morphology of the Pondaung Anthracotherium species is distinct from that of other species and is the most primitive. In addition, the Pondaung Anthracotherium species are the oldest of the genus. The genus Anthracotherium might have originated and rapidly radiated around the Pondaung area during the latest middle Eocene. Siamotherium pondaungensis described from the Pondaung Formation as an anthracotheriid is synonymized to Pakkokuhyus lahirii (Artiodactyla; Helohyidae). Key words: Anthracotheriidae, Anthracotherium, Eocene, Myanmar, Pondaung Formation, systematics Introduction The Anthracotheriidae is an extinct group of browsing suiform artiodactyls that achieved wide distribution across Eurasia, parts of Africa, and North America from the Eocene to Plio-Pleistocene periods (Black, 1978; Ducrocq, 1997; Kron and Manning, 1998). Their body size ranges from small, terrier-sized animals to beasts approaching the size of a hippopotamus (Black, 1978). Typical early anthracotheres have complete dentition and bunodont or bunoselenodont molars, five cusped upper molars without hypocone and four cusped lower molars without paraconid (Ducrocg et al., 1996). Their low-crowned teeth and fre- quent occurrence in paleochannel deposits suggest habits and habitat similar to those of modern hippos (Kron and Manning, 1998). The fossil record of anthracotheres is abundant and di- verse throughout the world. In East Asia, they appeared from the middle Eocene and survived until the Plio- Pleistocene (Colbert, 1938; Ducrocq, 1997). In Europe, they appeared during the late Eocene and became extinct in the Miocene. In Africa, they evolved from the late Eocene to the Plio-Pleistocene (Black, 1978; Ducrocq, 1994a, 1997). In North America, they are recorded from the late middle Eocene to the early Miocene, but the fossil record of North American anthracotheres is neither particularly abundant nor very diverse (Kron and Manning, 1998). In regard to the anthracotheres’ phyletic relationships, traditionally, most researchers have considered that anthracotheres might have originated from a helohyid stock (Pilgrim, 1928, 1940, Coombs and Coombs, 1977; Ducrocq et al., 1997) or from diacodexoid forms (Ducrocq, 1994b), 364 Takehisa Tsubamoto et al. and that they might have been the ancestors of extant hip- pos because some types of anthracotheres are considered to have had a hippopotamid mode of life and a body structure similar to hippos (Black, 1978; Colbert, 1935; Gentry and Hooker, 1988; Thewissen et al., 2001). According to mo- lecular data (e.g., Nikaido et al., 1999), hippopotamids comprise a monophyletic clade with cetaceans, so that anthracotheres might have originated from a stock of the [Cetacea + Hippopotamidae] clade (Rose, 2001). On the other hand, a few researchers (Pickford, 1983; but see Ducrocq, 1994b for discussion) suggested that hippopot- amids could have originated not from an anthracothere stock but from a peccary one (Ducrocq, 1997). In regard to regional origin, many researchers have con- sidered that anthracotheres might have originated in East Asia during the Eocene (e.g., Pilgrim, 1928; Suteethorn et al., 1988; Ducrocq, 1994a, 1999), because Eocene anthracotheres of East Asia are abundant and well diversi- fied and because they show a primitive bunodont condition (Ducrocq, 1999). The anthracotheres from the Eocene Pondaung Formation (Myanmar) are the first mammalian taxa in this formation to have been described (Pilgrim and Cotter, 1916). They are among the oldest anthracotheres in East Asia and consist of three genera and as many as 13 species (Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, 1938). Therefore, many studies have viewed the Pondaung anthracotheres in relation to the origin and early radiation of this group (e.g., Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, 1938; Coombs and Coombs, 1977; Ducrocq, 1999). Despite the richness of the fossil collections, the classifi- cation of the Pondaung anthracotheres has been problem- atic (Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, 1938; Holroyd and Ciochon, 1991). The taxonomic confu- sion on the Pondaung anthracotheres is likely to be due to their highly varied and primitive dental morphology. In this paper, we reevaluate the classification of the Pondaung anthracotheres based on previously described fossil materials (Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, 1938) and new collections. We then also discuss classifications of some other Eocene anthracotheres of East Asia in relation to the revision of the classification of the Pondaung anthracotheres. Institutional abbreviations AMNH = American Museum of Natural History, New York, USA; CM = Carnegie Museum of Natural History, Pittsburgh, USA; BMNH = The Natural History Museum (formerly British Museum of Natural History), London, United Kingdom; DMR = Department of Mineral Re- sources, Bangkok, Thailand; GSI = Geological Survey of India, Kolkata, India; IVPP = Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China; NSM = National Science Museum, Tokyo, Japan; UCMP = Museum of Paleontology, University of California, Berkeley, USA. Materials The new collections of Pondaung anthracotheres used here were discovered in 1997 by Myanmar researchers (Pondaung Fossil Expedition Team, 1997; Takai et al., 1999), and in 1998 (November) and 1999 (November) by Myanmar-Japan joint team (Takai et al., 2000, 2001; Egi and Tsubamoto, 2000; Tsubamoto et al., 2000a, b, 2001, 2002; Shigehara et al., 2002; Gebo et al., in press). These new fossil materials are stored in the National Museum of the Union of Myanmar (Yangon, Myanmar). They are se- rially catalogued under NMMP-KU specimen numbers. NMMP stands for National Museum, Myanmar, Paleontology; and KU for Kyoto University (Japan). The dental measurements used here are listed in the Appendix. Geologic setting The Pondaung Formation is distributed in the western part of central Myanmar (Figure 1). The Pondaung Formation overlies and partially interfingers with the mid- dle Eocene Tabyin Formation, and is conformably overlain by the late Eocene Yaw Formation (Stamp, 1922; Bender, 1983; Aye Ko Aung, 1999). The Pondaung Formation consists of alternating mudstone, sandstone, and conglom- erate, and is subdivided into the “Lower” and “Upper” Members (Aye Ko Aung, 1999). The “Lower Member” is dominated by greenish pebbly sandstone and mudstone and contains only a few fossil leaf fragments in its upper part (Aye Ko Aung, 1999). The “Upper Member” is domi- nated by fine- to medium-grained sandstone and variegated mudstone and contains many terrestrial mammalian and other vertebrate fossils that indicate a freshwater environ- ment (Colbert, 1938; Bender, 1983; Aye Ko Aung, 1999; Aung Naing Soe, 1999; Aung Naing Soe et al., 2002). Its mammalian fauna and the fission-track age of the “Upper Member” (37.2 + 1.3 Ma) indicate a latest middle Eocene age (Tsubamoto et al., 2002). Previous studies on Pondaung anthracotheres Pilgrim and Cotter (1916) first described three genera (Anthracohyus, Anthracotherium, and Anthracokeryx) and seven species of anthracotheres from the Pondaung Formation. Pilgrim (1928) revised the Pondaung anthra- cotheres into three genera (Anthracohyus, Anthracothema, and Anthracokeryx) and 13 species, describing new Anthracotheriidae from Myanmar 365 Pondaung AS MYANM Sy D AR } \ NX N À = \ Yangon’® Figure 1. main regions of fossil localities. materials. Colbert (1938) reviewed the Pondaung anthra- cotheres, and recognized the same three genera as Pilgrim (1928) and seven to nine species, also describing new ma- terials. Thus, in the Pondaung Formation, the three anthracothere genera Anthracohyus, Anthracothema, and Anthracokeryx have been traditionally recognized. All these three genera were established based on the material from the Pondaung Formation. Most of the anthracothere materials collected from the Pondaung Formation have been assigned to Anthracothema or Anthracokeryx, whereas remains of Anthracohyus have been very rare. Anthracohyus was established by Pilgrim and Cotter (1916) and was characterized particularly by the absence or very feeble development of the styles on the upper molars. Originally, this genus included three species, that is, Anthracohyus choeroides, Anthracohyus rubricae, and Anthracohyus palustris. Subsequently, the latter two spe- cies were moved to a new genus Anthracothema as deter- mined by Pilgrim (1928). This classification is followed by Colbert (1938). The only remaining species in the genus Anthracohyus, A. choeroides, was characterized by the conical cusps on its molars, by the absence or very fee- ble development of the molar styles, and by the mesiodistal diameter of the upper molar being shorter on the buccal side than on the lingual side (Colbert, 1938). Anthracothema was established by Pilgrim (1928). Four species of the Pondaung anthracotheres described by Pilgrim and Cotter (1916) were referred to this genus: Anthracohyus rubricae, Anthracohyus palustris, Anthra- cotherium pangan, and Anthracotherium crassum. All Mogaung area A. Map of Myanmar showing the location of the Pondaung area. 95°R @ Major cities B B. Map of the Pondaung area showing the location of the three these species were renamed by Pilgrim (1928) as Anthracothema rubricae, Anthracothema palustre, Anthra- cothema pangan, and Anthracothema crassum, respec- tively. Afterwards, A. palustre and (questionably) A. crassum were synonymized to A. pangan by Colbert (1938). Therefore, two (or three) species of the Pondaung Anthracothema were still recognized by him. The genus Anthracothema was characterized by its larger size, weaker molar styles, and its more conical molar cusps than those of Anthracokeryx from the Pondaung Formation (Pilgrim, 1928; Colbert, 1938). Recently, Anthracothema was synonymized to Anthracotherium by Ducrocq (1999). Anthracokeryx was erected by Pilgrim and Cotter (1916). They described two species of Anthracokeryx, Anthra- cokeryx birmanicus and Anthracokeryx tenuis. Pilgrim (1928) then described six more species of this genus, namely Anthracokeryx hospes, Anthracokeryx bambusae, Anthracokeryx myaingensis, Anthracokeryx ulnifer, Anthracokeryx moriturus, and Anthracokeryx? lahirii. Colbert (1938) later on recognized four to six species of the Pondaung Anthracokeryx. The genus Anthracokeryx was characterized by its smaller size, better marked molar styles, and its more crescentic (selenodont) molar cusps than Anthracothema and Anthracohyus from the Pondaung Formation (Pilgrim, 1928; Colbert, 1938). On the other hand, the taxonomic validity of keeping Anthracokeryx? lahirii in the Anthracotheriidae was discussed by both Pilgrim (1928) and Colbert (1938). Recently, this species was referred to the Helohyidae (Artiodactyla) and renamed Pakkokuhyus lahirii by Holroyd and Ciochon (1995). 366 Takehisa Tsubamoto et al. lcm Figure 2. Comparison of Siamotherium pondaungensis and Pakkokuhyus lahirii. A. M of the type of Siamotherium pondaun- gensis [NMMP-KU 0039 (Kdw 6): a right maxillary fragment with M] in occlusal view (reversed). B. M; of the type of Pakkokuhyus lahirii (GSI B-766: a right mandibular fragment with M.) in occlusal view. On Siamotherium pondaungensis Based on a right maxillary fragment with M~* (Kdw 6 = NMMP-KU 0039; Figure 2A) from the Pondaung Formation, Siamotherium pondaungensis was described by Ducrocq et al. (2000) as a new species of Siamotherium (Anthracotheriidae). Siamotherium was known only from the Krabi basin, the late Eocene of Thailand (Suteethorn et al., 1988; Ducrocq, 1999). However, the dentition dis- played by the unique material of S. pondaungensis matches that of Pakkokuhyus lahirii (Helohyidae) (Figure 2B) de- scribed from the Pondaung Formation by Pilgrim (1928) and Holroyd and Ciochon (1995) based on a right mandibular fragment with Mis. Ducrocq et al. (2000) did not compare S. pondaungensis with P. lahirii. Although the upper dentition of P. lahirii has never been described, we believe that this upper dental material described as S. pondaungensis should be referred to P. lahirii rather than to another taxon because (1) the upper molars of S. pondaungensis are conical, bunodont, and brachyodont mo- lars, like the lower molars of P. lahirii; (2) the sizes and cusp configurations of M’ and M’ of S. pondaungensis well match those of M: and M; of the type of P. lahirii (GSI B- 766), respectively (e.g., M° protocone, M° protocone, and M’ metaconule match M talonid basin, M; talonid basin, and M; hypoconulid basin, respectively) (Figure 2); (3) the upper dental morphology of S. pondaungensis is similar to that of helohyids, such as Helohyus, in having similar dent- al size, bunodont and conical cusps with enlarged metaconule, and no or vestigial styles; and additionally, (4) both S. pondaungensis and P. lahirii have been found only in the Pondaung Formation. Further discoveries of better materials are necessary to settle the classification, but fol- lowing our observations on the dental materials, we treat Siamotherium pondaungensis as a junior synonym of Pakkokuhyus lahirii (Helohyidae) in this paper. Dental morphology and size variation of Pondaung anthracotheres and their classification Generic status of Anthracothema and Anthracokeryx As mentioned above, after the review of Colbert (1938), the Pondaung anthracotheres have been classified into three genera, Anthracohyus, Anthracothema, and Anthracokeryx, and into as many as 13 species. This is because Colbert (1938) and earlier researchers (Pilgrim and Cotter, 1916; Pilgrim, 1928) recognized various dental morphologies among the Pondaung anthracotheres. However, the differences in dental morphologies between two of the genera, Anthracothema and Anthra- cokeryx, in the Pondaung Formation are very subtle com- pared to other anthracotheriid taxa. In addition, these two genera have variations in selenodonty (crista development) and style development on the upper molars, which were the diagnostic characters for distinguishing them (Figures 3-5; Pilgrim and Cotter, 1916, plates 2-5; Pilgrim, 1928, plates 1-4; Colbert, 1938, figs. 41-52). Although Anthra- cokeryx, the smaller anthracothere group, generally has rather selenodont molars with better developed molar styles compared to Anthracothema, and although Anthracothema, the larger anthracothere group, generally has rather bunodont molars with less-developed styles compared to Anthracokeryx, the development of selenodonty and styles is variable. We examined all previously described materi- als of the Pondaung anthracotheres stored in AMNH and GSI, and recently collected materials in the National = Figure 3. New upper dental materials of the Pondaung anthracotheres (Anthracotherium) in occlusal view (1). A, A’. NMMP-KU 0053, an right upper jaw with P’-M? (stereo pair). B. NMMP-KU 0455, a right maxillary fragment with P™“. C. NMMP-KU 0327, a right mandibular frag- ment with dP*. D. NMMP-KU 0056, a right maxillary fragment with M. E. NMMP-KU 0404, a right M’. F.NMMP-KU 0411, a left maxillary fragment with M. G. NMMP-KU 0070, a right M’. right maxillary fragment with M’“®. J. NMMP-KU 0379, a left M”. H. NMMP-KU 0382, a left maxillary fragment with M (or M”). I. NMMP-KU 0326, a K. NMMP-KU 0384, a right M'“”. Scale bars = 2 cm (left middle scale corresponds to A, A’, central upper scale corresponds to B-C, and right lower scale corresponds to D-K). 367 Anthracotheriidae from Myanmar 368 Takehisa Tsubamoto et al. Figure 4. New upper dental materials of the Pondaung anthracotheres (Anthracotherium) in occlusal view (2). A. NMMP-KU 0413, a right maxillary fragment with PM. B. NMMP-KU 0216, a right maxillary fragment with M. C. NMMP-KU 0329, a left maxillary fragment with M'”. Scale bars = 2 cm. Museum of Myanmar. We did not find any critical differ- ences in selenodonty and style development between the Pondaung Anthracothema and Anthracokeryx. Further- more, we did not recognize any dental characteristics sepa- rating these two Pondaung anthracotheriid genera. For example, NMMP-KU 0056, a right maxillary fragment with M” (Figure 3D), has large dental size suggesting that it is referable to Anthracothema. However, the molar styles of this material are developed as well as or more than the small molar materials in Figure 3G-K, which may be referable to Anthracokeryx. Therefore, we conclude that the two genera are identical to each other. = Figure 5. New lower dental materials of the Pondaung anthracotheres (Anthracotherium). A, A’, B-C. NMMP-KU 0052, a right mandibular fragment with P,P;-Ms: A, A’, occlusal view (stereo pair); B, lingual view; C, buccal view. D, D’, E-F. NMMP-KU 0086, a left P:: E, E’, occlusal view (stereo pair); F, lingual view; G, buccal view. G. NMMP-KU 0330, a left mandibular fragment with M, in occlusal view. H. NMMP-KU 0419, a talonid part of left Ms, in occlusal view. I. NMMP-KU 0332, a right mandibular fragment with Ms, in occlusal view. J, K. NMMP-KU 0433, a right P,; J, lingual view; K, occlusal view. Scale bars = 2 cm (left middle scale corresponds to A-C, A’, and left lower scale corresponds to D-K, D’, and right lower scale corresponds to J-K). Anthracotheriidae from Myanmar 370 Takehisa Tsubamoto et al. Anthracotherium Anthracotherium Anthracotherium from Pondaung chaimanei magnum Upper left P° occlusal view Lower right P, occlusal view ad pad med Rn mei med lingual view u MD Figure 6. magnum. Abbreviations: pad, paraconid; med, metaconid. Furthermore, these two genera, Anthracothema and Anthracokeryx, are also similar to the genus Anthra- cotherium in regard to dental morphology (Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, 1938). Describing a new species of Anthracotherium from the late Eocene Krabi basin of Thailand, Ducrocq (1999) synonymized Anthracothema to Anthracotherium. He mentioned that the graduation observed in the style development of P*- M’, in the robustness and orientation of P’, and in the devel- opment of the lingual crests on the lower premolars among Anthracothema pangan from Pondaung, Anthracotherium chaimanei from Krabi, and Anthracotherium monsvialense from Europe probably indicates a direct relationship among these three taxa. We concur with Ducrocq’s (1999) con- clusion. In addition, we also synonymize Anthracokeryx to Anthracotherium in this paper because Anthracokeryx and Anthracothema are not separable from each other, as men- tioned above. All these three genera have bunodont denti- tion, quite similar upper and lower molar morphologies to one another, and mesiodistally elongated simple P;. No distinct characteristics of dental morphology distinguish the three genera. Specific identification Among the species of the genus Anthracotherium, defini- tive characteristics in upper and lower posterior premolars distinguish the Pondaung Anthracotherium species from AS Schematic drawings of left P’ and right P, of the Pondaung Anthracotherium, Anthracotherium chaimanei, and Anthracotherium more progressive Anthracotherium species, such as Anthracotherium chaimanei from the late Eocene Krabi basin of Thailand and European Anthracotherium (e.g., Anthracotherium magnum from the Oligocene). These premolar characteristics indicate that the Pondaung Anthracotherium species resemble each other in their dent- al morphology more than they do any other species of this genus (Figures 3, 5, 6). The P° in all materials of the Pondaung Anthracotherium has a mesiodistally elongated triangular outline in occlusal view with pre- and postprotocrista extending mesiodistally; whereas the P° of A. chaimanei has a more mesiodistally compressed trianglar outline with the pre- and postprotocrista running more diagonally, and that of A. magnum has a trapezoidal outline in occlusal view with pre- and postprotocrista run- ning more diagonally (Figure 6; Ducrocq, 1999). The Ps in all materials of the Pondaung Anthracotherium has a vestigial metaconid but does not have any trace of paraconid, whereas A. chaimanei and A. magnum have both tiny paraconid and metaconid (Figure 6). The P° in all ma- terials of the Pondaung Anthracotherium is less selenodont and has much weaker styles than those in the P* of A. mag- num and A. chaimanei, as mentioned by Ducrocq (1999). Also, the development of the lingual crests on the lower premolars of the Pondaung Anthracotherium is weaker (Ducrocq, 1999). In such premolar morphologies, there are no critical characteristics that distinguish any group Anthracotheriidae from Myanmar —+— GSI B751 —e— GSI B617 ass 8 8 —8— AMNH 20011 (right) 3 —k— GSI B605 8 Crown area (length X width) (mm?) —=— GSI B755 —<— AMNH 20017 (left) À —e— NMMP-KU 0052 M, M; M; Figure 7. among the Pondaung Anthracotherium. In addition, al- though there are individual variations, the Pondaung Anthracotherium species are distinct from other Anthracotherium species in having such molar morpholo- gies as weaker selenodonty and weaker development of styles (Figures 3-5). These characteristics indicate that the Pondaung Anthracotherium species possess the most primitive dentition within the genus (Ducrocq, 1999). Similar to the case of the dental morphology, the dental sizes of the Pondaung anthracotheres are highly variable. Figure 7 shows the line chart of the molar areas (width X length) in individuals of the Pondaung anthracotheres. The size of M'/; relative to M’/. and M’7; relative to M’/; in a single individual is not constant among the Pondaung anthracotheres. For example, M, in GSI B751 is much smaller than in GSI B617, while M; in the former is rather larger than in the latter. This kind of variation shown in Figures 7 can be explained by individual variation and can- not be attributed to specific differences, as mentioned below. The dental sizes of each tooth class of all the Pondaung anthracothere materials are also highly variable (Figures 8, 9). For example, the size of smallest M’ is about 15 mm in width and 14 mm in length, while that of largest M’ is about 45 mm in width and 39 mm in length (Figure 8). Such size differences do not support the idea that the Pondaung anthracotheres consist of one species. How- ever, this distributional pattern of the dental size supports the argument that these animals belong to the same taxo- nomic category (that is, genus) because the scatter plots of the mesiodistal length and buccolingual width of P’/;- M’/; are easily fitted to a straight-line by simple regression Crown area (length X width) (mm?) —a— AMNH 20017 (right) 371 800 —k— AMNH 20027 700 600 —#— AMNH 20011 ei 500 400 —e— NMMP-KU 0053 —e— GSI B621 2 > > (=) —+— GSI B756 (right) —— AMNH 20017 (left) —a— AMNH 20017 (right) N 4 = =] 100 ge=— M! M2 13 Size change (line chart) of upper and lower molars of the Pondaung anthracotheres in each individual. (Figures 8, 9). Among the dental size distributions (Figures 8, 9), it is noteworthy that the Mı size can be more readily divided into four groups than the other tooth classes. In general, the first molars are the first of the adult dentition to erupt and express less size variation among the adult dentition. A number of extant herbivores, including both browsing and grazing forms and certain species of hippos and suids, compensate for tooth wear by sequential or delayed tooth eruption (Kron and Manning, 1998). As the anterior teeth (and/or teeth erupting earlier) wear out, the emerging last molars (typically enlarged) take a progressively greater role in food comminution, resulting in no net loss of feeding ef- ficiency (Kron and Manning, 1998). Thus, the teeth erupt- ing later (posterior molars and premolars) are considered to express much wider dental size variations than do first mo- lars in each species. In particular, lower first molars (Mı) have been considered to express less size variation com- pared to upper first molars (M'), and to correlate very closely to the body size of mammals compared to other tooth classes (Gingerich, 1974; Gingerich and Schoeninger, 1979; Legendre, 1986, 1989; Conroy, 1987; Legendre and Roth, 1988; Dagosto and Terranova, 1992; Bown et al., 1994). Therefore, the distributional pattern of M, size (~ body size) in the Pondaung anthracotheres (Figure 9) suggests that the Pondaung anthracotheres can be divided into four subgroups within a single taxonomic group, that is, four species within a single genus, although a very high degree of size variation exists particularly in the posterior molars. In relation to the specific classification of the Pondaung anthracotheres, we should mention here one dental charac- 372 Takehisa Tsubamoto et al. i) un = 25 E Mi = 20 3” x x aS) x = x gb 15 x oO 510 10 Rog d= = = > 5 5 10 15 20 25 5 10 15 20 5 10 15 20 Length (mm) 10 15 20 25 30 35 40 Figure 8. Size distribution of P°‘ and upper molars of the Pondaung anthracotheres. an E Ps x = x SU x x a x = < % 3 es 0 0 10 20 30 Length (mm) 30 38 = M M3 x x 25 x xx x x XX x x 20 x x % xx x 15 x ” x 10 x DK 1 5) L 1 = 30 40 10 20 30 40 50 60 Figure 9. Size distribution of Ps, and lower molars of the Pondaung anthracotheres. Anthracotheriidae from Myanmar 373 Figure 10. choeroides), a left M°. a left maxillary fragment with P**. B. NMMP-KU 0432, a left M’. F. NMMP-KU 0475, a right Ms. teristic of M;. Pilgrim (1928) distinguished the two small Pondaung anthracotheres, Anthracokeryx ulnifer and Anthracokeryx myaingensis, from one another on the basis of the morphology of the hypoconulid on M;; the former has a single cusp at the hypoconulid region on M;, whereas the latter has a double cusp. Although most of the Pondaung anthracotheres have a double cusp at the hypoconulid region on Ms, the buccal of which is always larger and more distinct than the lingual one, the develop- ment of the lingual one is highly variable among all the ex- amples of M; in the Pondaung anthracotheres. For ex- ample, the lingual cusp in the hypoconulid on M; is almost as large as the buccal one in NMMP-KU 0330 (Figure 5G), whereas it is very small and faint in NMMP-KU 0419 (Figure 5H). We consider this difference to be individual variation, not a specific characteristic. Status of Anthracohyus We also synonymize the remaining genus among the Pondaung anthracotheres, Anthra- cotherium. Although Anthracohyus has unique dental structures in the upper molars (GSI B603, Figure 10A) (Pilgrim and Cotter, 1916; Pilgrim, 1938; Colbert, 1938), Anthracohyus, to The Pondaung anthracothere materials of Anthracohyus-type in occlusal view. C. NMMP-KU 0454, a left M’. Scale bar = 2 cm. A. GSI B603 (holotype of Anthracohyus D. NMMP-KU 0453, a right M. E. NMMP-KU 0500, the basic structures of its upper molars are referable to those of the Pondaung Anthracotherium (Figures 3, 4). Furthermore, the lower dental material of Anthracohyus choeroides, GSI B605 (a right mandibular fragment with complete dentition) (Pilgrim and Cotter, 1916, pl. 2, figs. 3, 3a-e, 4, 4a-e), is identical to that of Anthracokeryx birmanicus from the Pondaung Formation (Pilgrim, 1928, pl. 4, fig. 5; Colbert, 1938, fig. 45); there is no morphologi- cal or size distinction among the lower dental materials of the two species. On the other hand, there are a few new specimens whose dental morphologies seem to be identical to that of Anthracohyus (Figure 10B-F): NMMP-KU 0452 (a left M’), 0453 (a right M’), 0454 (a left M’), 0475 (a right M;), and 0500 (a left maxillary fragment with P**) [the latter four specimens (NMMP-KU 0453, 0454, 0475, and 0500) probably belong to the same individual]. The upper mo- lars amomg these (NMMP-KU 0452, 0453, 0454) have characteristics of Anthracohyus: very conical cusps, no or very upper dentition, and mesiodistally shorter buccal margins than the lingual one on the upper molars. The three examples of M’, GSI B603 (type of Anthracohyus choeroides) (length: 21.2 mm; vestigial styles on the 374 width: 25.4 mm), NMMP-KU 0452 (length: 27.9 mm; width: 33.0 mm), and NMMP-KU 0453 (length: 19.6 mm; width: 21.8 mm), are separately scattered in the same linear size-distributional pattern prevalent among the Pondaung anthracotheres (Figure 6). Although these three specimens are not M, and are considered to have relatively great size variation, they may be referred to the second largest, larg- est, and second smallest groups among the four groups of the Pondaung anthracotheres mentioned above, respec- tively, according to their sizes. Therefore, this size- distributional pattern also suggests that these Anthracohyus -type materials express one of the variations among the Pondaung anthracotheres, that is, species of Anthra- cotherium. In conclusion, taking the variations of molar morphology (particularly development of upper molar styles) and size of the Pondaung anthracotheres into consideration (Figures 3-5), we interpret the dental morphology of Anthracohyus as one of the unusual individual variations of the Pondaung Anthracotherium. Otherwise, a multiplicity of species (of Anthracothema, Anthracokeryx, and Anthracohyus) which are morphologically and phyletically very close to one an- other, have to be maintained in a single fossil fauna (the Pondaung fauna). Such a situation seems unreasonable. Classification To review, we synonymize all the genera of the Pondaung anthracotheres (Anthracothema Pilgrim, 1928, Anthracokeryx Pilgrim and Cotter, 1916, and Anthracohyus Pilgrim and Cotter, 1916) to Anthracotherium Cuvier, 1822. We group the Pondaung Anthracotherium materials into four species on the basis of M, size (~ body size). Materials lacking Mi are tentatively assigned to one of the four species based on the sizes of available teeth (Appendix). There is a possibility that the larger two and smaller two of the four species might in fact be sexual dimorphic pairs as implied by Holroyd and Ciochon (1991). Most anthracotheres show a moderate amount of sexual dimor- phism, but it is expressed by the canines: the individuals adjudged to have been male have larger canines than do the females (Kron and Manning, 1998). However, the fossil materials of the Pondaung anthracotheres are too poor to evaluate distribution of canine size, so there is no evidence to confirm that the larger two and smaller two represent male-and-female of sexually dimorphic species. Also, no critical difference in canine size relative to M, is observed among the currently available materials. Therefore, we treat these four groups of the Pondaung Anthracotherium as four species in this paper. Although the specific nomenclature of the Pondaung anthracotheres has been very complicated as mentioned above (Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, Takehisa Tsubamoto et al. 1938), the following four species names can be retained based on the rule of priority: largest species, Anthra- cotherium pangan Pilgrim and Cotter, 1916; second largest species, Anthracotherium crassum Pilgrim and Cotter, 1916; second smallest species, Anthracotherium birmani- cum (Pilgrim and Cotter, 1916); and smallest species, Anthracotherium tenuis (Pilgrim and Cotter, 1916). The possibility remains that the larger two (A. pangan and A. crassum) and smaller two (A. birmanicum and A. tenuis) might each be combinable as a sexually dimorphic species. Concluding remarks The dental morphological comparisons in this study indi- cate that the Pondaung anthracotheres consist of four species of one genus (Anthracotherium). Their dental morphology, such as selenodonty, development of styles, and premolar shapes, suggest that the four species are much more similar to one another than to any other species of Anthracotherium from other deposits, although the dental morphology trend seems to be highly variable within the Pondaung Anthracotherium. In addition, the group of Pondaung Anthracotherium species has the other following features: (1) it is the oldest among the genus; (2) in basic dental morphology, the Pondaung Anthracotherium are likely to be the most primitive among the genus; and (3) their fossil materials predominate in collections of the Pondaung mammal fauna, suggesting a dominant popula- tion size (Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, 1938; Tsubamoto, 2001). Therefore, it is suggested that: (1) the genus Anthracotherium originated and rapidly radi- ated around the Pondaung area during the latest middle Eocene, and (2) Anthracotherium migrated from southern East Asia to Europe during the latest middle to late Eocene (Ducrocq, 1995). Systematic paleontology Order Artiodactyla Owen Family Anthracotheriidae Leidy Genus Anthracotherium Cuvier, 1822 Synonyms.— Anthracohyus Pilgrim and Cotter, 1916; Anthracokeryx Pilgrim and Cotter, 1916; Anthracothema Pilgrim, 1928. Type species.—Anthracotherium magnum Cuvier, 1822. Included species from Europe. — Anthracotherium monsvialense De Zigno, 1888; Anthracotherium alsaticum Cuvier, 1822; Anthracotherium seckbachense Kinkelin, 1884; Anthracotherium illyricum Teller, 1886; Anthracotherium bumbachense Stehlin, 1910; Anthracotherium cuvieri Gaudry, 1873; Anthracotherium hippoideum Rütimeyer, 1857; Anthracotherium valdense Anthracotheriidae from Myanmar 373 Kowalevski, 1876; Anthracotherium dalmatinum von Meyer, 1854. (after Ducrocq, 1999) Included species from Asia.—Anthracotherium bugtiense Pilgrim, 1907 (sensu Pickford, 1987); Anthracotherium silistrense Pentland, 1828 (sensu Pickford, 1987); Anthra- cotherium changlingensis Zhao, 1993; Anthracotherium chaimanei Ducrocq, 1999; Anthracotherium thailandicus (Ducrocq, 1999) new combination; Anthracotherium gungkangensis (Qiu, 1977) new combination; Anthra- cotherium verhoeveni (von Koenigswald, 1967); Anthra- cotherium pangan Pilgrim and Cotter, 1916; Anthra- cotherium crassum Pilgrim and Cotter, 1916; Anthra- cotherium birmanicum (Pilgrim and Cotter, 1916) new combination; Anthracotherium tenuis (Pilgrim and Cotter, 1916) new combination. Revised diagnosis.—Large- to small-sized bunodont and primitive anthracothere. Differs from selenodont and bunoselenodont anthracotheres, such as Elomeryx and Bothriogenys, in having much simpler premolars and less developed selenodonty. Differs from Siamotherium in having double premetacristid on the lower molars (there is no distinct outer metacristid on those of Siamotherium), much better developed molar styles, less lingually located molar metacone in relation to paracone, much less mesiodistally compressed M”, and much better developed protocone compared to paracone on P**. Differs from Anthracosenex in having mesially or mesiobuccally ori- ented outer premetacristid rather than buccally oriented in Anthracosenex. Differs from Heptacodon in having less developed P: cristids, and in lacking such strongly devel- oped and prominent styles on the upper molars as in Heptacodon, and molar postentocristid that runs distobuccally and links to posthypocristid making a V- shaped notch. Differs from Microbunodon in having more bunodont cusps, less developed cingulum, rather straight (not V-shaped) ectoloph on P**, and mesiodistally longer PA Anthracotherium pangan Pilgrim and Cotter, 1916 Anthracotherium pangan Pilgrim and Cotter, 1916, p. 59-60, pl. 4, figs. 1-3. Anthracothema pangan (Pilgrim and Cotter, 1916). Pilgrim, 1928, p. 10-13, pl. 1, figs. 1-7; Colbert, 1938, p. 353-355, figs. 41-22. Anthracohyus rubricae Pilgrim and Cotter, 1916 (in part), p. 55-57, pl. 2, fig. 5-6, pl. 3, fig. 1-2. Anthracothema rubricae (Pilgrim and Cotter, 1916) (in part). Pilgrim, 1928, p. 14; Colbert, 1983, p. 356-358. Anthracotherium crassum Pilgrim and Cotter, 1916 (in part), p. 60-61, pl. 4, fig. 4-5, 5a. Anthracothema crassum (Pilgrim and Cotter, 1916) (in part). Pilgrim, 1928, p. 16-18; Colbert, 1938, p. 355-356. Anthracohyus palustris Pilgrim and Cotter, 1916, p. 58, pl. 3, figs. 7-9. Anthracothema palustre (Pilgrim and Cotter, 1916). Pilgrim, 1928, p. 14-16, pl. 2, figs. 8-10; Colbert, 1938, p. 355. Lectotype.—GSI B619, a left maxillary fragment with M** (Colbert, 1938). Revised diagnosis. —Large-sized and one of the most primitive Anthracotherium species. The dental morphol- ogy is almost identical to other Pondaung Anthracotherium species (i.e., A. crassum, A. birmanicum, and A. tenuis). Differs from the other Pondaung Anthracotherium species in having larger Mı. Differs from more progressive Anthracotherium, such as A. magnum, A. monsvialense, A. bugtiense, and A. chaimanei, in having slightly less selenodont cusps, less developed styles, mesiodistally elon- gated triangular outline of P’ in occlusal view having mesiodistally (not diagonal to the tooth row) extending paracrista, less developed lower premolar cristids, and less molariform P; lacking a trace of paraconid. Differs from A. thailandicus in having slightly lower tooth crown in the lower dentition, less selenodonty, and metaconid on Ps, and lacking paraconid on P;. Differs from A. silistrense in having larger size and slightly lower P34. Differs from A. gungkangensis in having larger size, slightly less developed selenodonty and styles, more rounded outline of upper mo- lars in occlusal view, and slightly wider and shorter upper molars. Differs from A. verhoeveni in lacking hypertro- phied metastyle on the distal face of M’. Differs from A. changlingensis in being smaller. Anthracotherium crassum Pilgrim and Cotter, 1916 Anthracotherium crassum Pilgrim and Cotter, 1916 (in part), p. 60-61, pl. 5, fig. 1. Anthracothema crassum (Pilgrim and Cotter, 1916) (in part). Pilgrim, 1928, p. 16-18; Colbert, 1938, p. 355-356. Anthracohyus rubricae Pilgrim and Cotter, 1916 (in part), p. 55-57, pl. 2, fig. 7, pl. 3, figs. 3-6, 5a. Anthracothema rubricae (Pilgrim and Cotter, 1916) (in part). Pilgrim, 1928, p. 14, pl. 2, figs. 1-7; Colbert, 1983, p. 356-358, figs. 43-44. Anthracohyus choeroides Pilgrim and Cotter, 1916 (in part), p. 32-55, pl. 2, figs. 1=2: Anthracokeryx moriturus Pilgrim, 1928, p. 32, pl. 4, figs. 1-3; Colbert, 1938, p. 376-379, figs. 51-52. Holotype.—GSI B615, a left maxillary fragment with M”. Revised diagnosis. — Second largest (medium-sized) Pondaung Anthracotherium. Differs from A. pangan in having smaller M;. Differs from A. birmanicum and A. tenuis in having larger M.. 376 Takehisa Tsubamoto et al. Anthracotherium birmanicum (Pilgrim and Cotter, 1916) Anthracokeryx birmanicus Pilgrim and Cotter, 1916 (in part), p. 61-62, pl. 5, figs. 2, 4; Pilgrim, 1928, p. 18-19, pl. 4, figs, 5, 5a; Colbert, 1938, p. 360-362, fig. 45. Anthracokeryx hospes Pilgrim, 1928, p. 29-30; Colbert, 1938, p. 362-363. Anthracohyus choeroides Pilgrim and Cotter, 1916 (in part), p. 52-55, pl. 2, figs. 3-4, 3a-3e, 4a—4e. Holotype.—GSI B621, a right maxillary fragment with P°-M°. Revised diagnosis. — Second smallest (medium-sized) Pondaung Anthracotherium. Differs from A. pangan and A. crassum in having smaller M.. Differs from A. tenuis in having larger M.. Anthracotherium tenuis (Pilgrim and Cotter, 1916) Anthracokeryx tenuis Pilgrim and Cotter, 1916, p. 62-63, pl. 5, figs. 6-8; Colbert, 1938, p. 364. Anthracokeryx birmanicus Pilgrim and Cotter, 1916 (in part), p. 61-62, pl. 5, figs. 3, 5. Anthracokeryx bambusae Pilgrim, 1928, p. 29; Colbert, 1938, p. 363. Anthracokeryx myaingensis Pilgrim, 1928, p. 30-31, pl. 3, figs. 4-7; Colbert, 1938, p. 364-365. Anthracokeryx ulnifer Pilgrim, 1928, p. 19-29, pl. 3, figs. 1-3, pl. 4, fig. 6; Colbert, 1938, p. 365-375, figs. 46-50. Holotype.—GSI B625 (a left maxillary fragment with M'’) and GSI B626 (a left mandibular fragment with M; and posterior part of dP.). Revised diagnosis. — Smallest (small-sized) Pondaung Anthracotherium. Differs from other Pondaung Anthra- cotherium species in having smaller M,. Further differs from A. thailandicus in lacking the high and ventrally sa- lient mandibular symphysis under P:, and in having longer diastema between P: and P;. Further differs from A. silistrense in having longer diastema in the anterior premo- lar dentition. Family Helohyidae Marsh Genus Pakkokuhyus Holroyd and Ciochon, 1995 Pakkokuhyus lahirii (Pilgrim, 1928) Anthracokeryx? lahirii Pilgrim, 1928, p. 32-33, pl. 4, figs 4, 4a; Colbert, 1938, p. 379. Pakkokuhyus lahirii (Pilgrim, 1928). 1995, p. 178-180, fig. 1A, B. Siamotherium pondaungensis Ducrocq et al., 2000, p. 756, fig. 2. Holroyd and Ciochon, Holotype.—GSI B766, right mandibular fragment with Mi. Revised diagnosis.—A helohyid having bunodont and conical cusps, lacking hypocone at least on M* and paraconid at least on M::. Differs from Gobiohyus and Helohyus in having more bunodont and conical cusps, a basally inflated crown, larger metaconule on M’, entoconid slightly posterior to hypoconid and less pronounced ectoflexid on the lower molars, a continuous labial cingulid on Ms, shorter and less distinct hypoconulid loop on Ms, stronger labial cingulids on Mi, and absolutely and rela- tively greater mandibular depth, and in lacking trace of molar hypocone, lingual cingulum and stylar cusps on the upper molars, and molar paraconid. Further differs from Gobiohyus in having relatively higher crowns and from Helohyus in having a stronger hypoconulid on the distal cingulid and in lacking accessory cuspulids on the hypoconulid loop. Differs from Progenitohyus in having smaller dental size, larger hypoconulid on Ms, and labial cingulid on Ms, and in lacking paraconid on Mb. Differs from the possible raoellid Haqueina in having entoconid slightly posterior to hypoconid, a stronger hypoconulid on the distal cingulid, and weaker hypolophid and cristid obliqua, a weaker and less constricted hypoconulid loop and a single hypoconulid on M. Differs from anthracotheriids in having smaller dental size, more conical (less selenodont) cusps, straight hypolophid on the lower molars, and shorter hypoconulid loop on M3, and in lacking a double premetacristid on the lower molars. Comments on some other Eocene anthracotheres from Asia We reappraise several Eocene anthracotheres from Asia in relation to the revision of the Pondaung anthracotheres. Anthracothema and Anthracokeryx have been also reported from other deposits in the Eocene of Asia. Because the Pondaung Anthracothema and Anthracokeryx are the types of the two genera and the two were referred to Anthracotherium, all species of Anthracothema and Anthracokeryx are referred to Anthracotherium, except for Anthracokeryx sinensis (including Anthracokeryx dawsoni and Anthracothema minima), Anthracokeryx litangensis, and Anthracothema lijiangensis. Anthracokeryx birmanicus, Anthracokeryx moriturus, Anthracokeryx sp. (= Anthracokeryx sp. cf. bumbusae), and Anthracothema rubricae, which are conspecific with one or another of the Pondaung anthracotheres, are recorded from the late Eocene Naduo Formation, Bose and Yongle basins, Guangxi, southern China (Chow, 1957; Tang et al., 1974; Qiu, 1977; Russell and Zhai, 1987). The materials of these species are poor, so that for the time being we tenta- tively refer these materials to the same species as Anthracotheriidae from Myanmar 377 Anthracotherium from the Pondaung Formation. We refer Anthracothema rubricae and Anthracokeryx moriturus to Anthracotherium crassum, Anthracokeryx birmanicus to Anthracotherium birmanicum, and Anthracokeryx sp. to Anthracotherium sp. Anthracokeryx gungkangensis and Anthracokeryx kwangsiensis are recorded from the late Eocene Gongkang Formation, which overlies the Naduo Formation (Qiu, 1977). Anthracokeryx kwangsiensis is also recorded from the Naduo Formation (Zhao, 1993). Ducrocg (1999) men- tioned that these two species likely correspond to only one form in terms of their very similar morphology and dimen- sions. Following his suggestion, we treat Anthracokeryx kwangsiensis as a junior synonym of Anthracokeryx gungkangensis. Therefore, both of these species are re- ferred to Anthracotherium gungkangensis. Anthracokeryx sinensis is recorded from the Heti (Yuanchu basin), Xiangshan (Lijiang basin, Yunnan), and Huangzhuang (Qufu, Shandong) formations of the middle Eocene of China (Zdansky, 1930; Xu, 1962; Shi, 1989; Zhong et al., 1996). We think that Anthracokeryx sinensis is not a bunodont but a primitive bunoselenodont anthra- cothere, so that this species is not referable to Anthra- cotherium (bunodont anthracothere). Hem PA OF Anthracokeryx sinensis (Zdansky, 1930, pl. 1, fig. 18; Xu, 1962, p. 241, fig. 1-3a) is much more molarized than that of progressive Anthracotherium species, such as Anthracotherium magnum. It has a somewhat triangle- shaped trigonid in occlusal view and resembles that of bunoselenodont or selenodont anthracotheres. Also, the upper molars of Anthracokeryx sinensis reveal stronger selenodonty than those of Anthracotherium. In particular, the paraconule of the upper molars of A. sinensis is much more selenodont than that of Anthracotherium. The selenodonty of the upper molars of A. sinensis also appears similar to that of bunoselenodont anthracotheres, such as Bothriogenys. Therefore, we consider that it is better to establish a new genus for Anthracokeryx sinensis. We suspect that it is better to synonymize both Anthracokeryx dawsoni and Anthracothema minima to Anthracokeryx sinensis. First, Anthracokeryx dawsoni was described by Wang (1985) from the late middle Eocene Zhaili Member of the Heti Formation (Yuanchu basin, cen- tral China), which also yields Anthracokeryx sinensis. The material of Anthracokeryx dawsoni consists of a skull with upper dentition. This material (IVPP V7915) has very similar dental morphology and size to Anthracokeryx sinensis except for a few dental differences (Xu, 1962, pl. 1, fig. 2-3, 8, 2A-3A, pl. 2, fig. 2, 2A; Wang, 1985, p. 58, pl., 1); such subtle differences seem to be within the range of intraspecific variation. Second, Anthracothema minima was described by Xu (1962, p. 233, 244, pl. 1, fig. 1, 1A) from the late middle Eocene Rencun Member of the Heti Formation, which also yields Anthracokeryx sinensis. Anthracothema minima consists of only one upper molar (IVPP V2661), which has conical cusps like that of the Pondaung Anthracothema and Anthracohyus. However, its overall dental morphology and size are similar to that of Anthracokeryx sinensis. Taking the case of the Pondaung anthracotheres mentioned above into consideration, it may be better to consider that Anthracothema minima is also not a distinct species but one of the variations of Anthracokeryx sinensis. Anthracokeryx litangensis was described from the late Eocene to early Oligocene Gemusi basin of Litang County (Sichuan, China), based on a right mandibular fragment with PM, and an astragalus by Zhong et al. (1996). Although its only preserved lower molar (Mı) is heavily worn (Zhong et al., 1996, p. 265, pl. 21, fig. 3), the lower molar is rather selenodont than bunodont, having more lingually oriented preparacristid and cristid obliqua than Anthracotherium and Anthracokeryx sinensis. Its Ps is mesiodistally elongated and with well-developed cristids, suggesting it is referable neither to Anthracotherium nor to Anthracokeryx sinensis. The dental morphology of Anthracokeryx litangensis is rather similar to that of selenodont anthracotheres, such as Bothriodon. _ Anthracokeryx thailandicus was described from the late Eocene Krabi basin of Thailand by Ducrocq (1999). We refer this species to the genus Anthracotherium and intro- duce for it the new combination Anthracotherium thailandicus. Ducrocq (1999, p. 125, pl. 14G) described an anthracotheriid left M’ (DMR TF2662) from the Krabi basin as Anthracotheriinae gen. et sp. indet. This material is morphologically similar to that of Anthracohyus from the Pondaung Formation (Ducrocq, 1999) and is similar to Anthracotherium thailandicus in size. Thus, DMR TF2662 might be one of the individual variations of A. thailandicus. Anthracokeryx sp. from the middle Eocene Lizhuang Formation (Henan, central China) was described by Wang and Zhou (1982) based on a broken right upper molar. Although this material was not illustrated, Wang and Zhou (1982) mentioned its morphological similarity to upper mo- lars of Anthracokeryx sinensis. Here, we tentatively refer this material to cf. Anthracokeryx sinensis. Cf. Anthracokeryx sp. was cited in the early to early mid- dle Eocene Kuldana Formation (Indo-Pakistan) by Gingerich et al. (1979) and Russell and Zhai (1987). It is only represented by BMNH 32168, a left M;, which was re- ferred to Lammidhania wardi (Anthracobunidae) by Gingerich (1977). However, the dental morphology of BMNH 32168 is identical M; of bunoselenodont anthra- cotheres, such as Bothriogenys, and is definitely not refer- able to Anthracokeryx (= Anthracotherium). Besides, 378 Takehisa Tsubamoto et al. BMNH 32168 may be from the overlying Murree Formation (Russell and Zhai, 1987). Therefore, the exis- tence of an Anthracokeryx (Anthracotherium)-like anthra- cothere in the Kuldana Formation is highly doubtful. Cf. Anthracokeryx sp. was cited also in the late middle Eocene Shara Murun Formation (Inner Mongolia, northern China) by Russell and Zhai (1987). The sole specimen of this form, AMNH 22090 (a right mandibular fragment with M;), was originally described as Gobiohyus robustus (Helohyidae) by Matthew and Granger (1925). The Ms; of the specimen has three large and distinct cusps at the hypoconulid region and reveals a bilophodont structure, which have never been seen in anthracotheres. Therefore, the existence of an Anthracokeryx (Anthracotherium)-like anthracothere in the Shara Murun Formation is also highly doubtful. Anthracothema lijiangensis was described from the mid- dle Eocene Xiangshan Formation (Lijiang basin, Yunnan, southern China) by Zong et al. (1996). This species dif- fers from Anthracotherium in having straight (not V- shaped) hypolophid, mesiodistally rather than mesio- lingually oriented cristid obliqua, and no buccal premetacristid directed mesiobuccally on the lower molars (Zong et al., 1996, p.279, pl. 35, fig. 2). These character- istics demand rejection of a reference of Anthracothema lijiangensis to Anthracotherium. It may be better to estab- lish a new genus for this species (Anthracothema lijiangensis is distinguished from Anthracokeryx sinensis). On the other hand, although the material of Anthracothema lijiangensis was referred to the Anthracotheriidae by Zong et al. (1996) and Huang (1999), this familial position of A. lijiangensis is also doubtful because the species have straight hypolophid and no trace of mesiobuccally-directed premetacristid on the lower molars, both which are not ap- propriate to the anthracotheriid diagnosis (Holroyd and Ciochon, 1995). Anthracotherium chaimanei was originally reported as Anthracothema sp. cf. A. pangan from the Krabi basin of Thailand by Ducrocq er al. (1992). It was formally de- scribed by Ducrocq (1999). Anthracotherium verhoeveni was originally described from Timor (Indonesia) (but see Ducrocq, 1996, p.765) as Anthracothema verhoeveni by von Koenigswald (1967). It was referred to the genus Anthracotherium by Ducrocq (1999). Anthracotherium? spp. were cited in the middle middle Eocene Lushi Formation (Henan, central China) by Chow et al. (1973). However, this report contained no illustra- tion of their material. In addition, the mammalian fauna of the Lushi Formation, which was referred to the middle mid- dle Eocene (Irdinmanhan East Asian Land Mammal Age) (Russell and Zhai, 1987), is much older than the latest mid- dle Eocene Pondaung Formation including the oldest posi- tive Anthracotherium species. Therefore, the presence of the genus Anthracotherium in the Lushi Formation is doubtful (Russell and Zhai, 1987). Heothema is recorded from the late Eocene Naduo and Gongkang Formations (Bose and Yongle basins, Guangxi) and lower part of Yongning Formation (late Eocene or early Oligocene; Nanning basin, Guangxi) of southern China (Tang, 1978; Zhao, 1981, 1983, 1993). Although the genus Heothema was synonymized to Anthracotherium by Ducrocq (1999), this genus may be valid because: (1) the molars and P* of Heothema are more selenodont than those of Anthracotherium; (2) crests on the lingual face of lower premolars in Heothema (Tang, 1978, pl. 3, fig. 1, 1A) are stronger than those in Anthracotherium; and (3) P: of Heothema seems to be more molariform than that of Anthracotherium, having a somewhat triangularly-shaped trigonid outline in occlusal view (Tang, 1978, pl. 3, fig. 1). Judging from these morphological points, Heothema might be one of the primitive bunoselenodont anthracotheres. For specific division of Heothema, we follow the grouping by Ducrocq (1999, p. 121), who recognized two species, Heothema bellia and Heothema chengbiensis. Huananothema imparilica was described as a new genus and species of the Anthracotheriidae by Tang (1978) based on an upper molariform tooth from the late Eocene Naduo Formation, which also yields Heothema. According to Tang (1978), the type and unique material of Huananothema imparilica (IVPP V4964) is an upper molar, and therefore this species is identified by its upper molar having an anterior buccolingual width less than its posterior buccolingual width, in contrast to other anthracotheres (in the upper molars of all other anthracotheres, the anterior buccolingual width is greater than the posterior buccolingual width). However, this fea- ture in IVPP V4964 is a typical dP* morphology of large anthracotheres as seen in DMR TF 2901, a right dP* of Anthracotherium chaimanei from the Krabi basin of Thailand (Ducrocq, 1999, pl. 5, fig. B), and also in NMMP- KU 0327, an upper dental specimen of the Pondaung Anthracotherium (Figure 3C). Therefore, [VPP V4964 is dP’, so that the diagnosis of Huananothema imparilica by Tang (1978) is invalid. By comparing its size and mor- phology with those of anthracotheres from the Naduo Formation, we consider that IVPP V4964 is a dP* of Heothema chengbiensis. Therefore, we synonymize both the genus Huananothema and species Huananothema imparilica to genus Heothema and species Heothema chengbiensis, respectively. The materials of Probrachyodus are poor. Russell and Zhai (1987, p. 130) mentioned that this genus may be in- separable from Anthracokeryx (that is, Anthracotherium or the same genus as Anthracokeryx sinensis). However, the upper molars of Probrachyodus show bunoselenodonty, so Anthracotheriidae from Myanmar 379 that this species differs from Anthracotherium, which com- prises bunodont anthracotheres. Probrachyodus is distinct from Anthracokeryx sinensis and also further from Anthracotherium in having more lingually procumbent molar paracone and metacone. Therefore, we consider this genus a valid one. Probrachyodus panchiaoensis was de- scribed from the middle Eocene Lumeiyi Formation (Yunnan, Lunan basin, southern China) by Xu (1962). Probrachyodus? sp. nov. was cited in the middle Eocene Dongjun Formation (Guangxi, southern China) by Ding et al. (1977). Acknowledgments We would like to express our sincere gratitude to Brigadier General Than Tun, Major Bo Bo and other per- sonnel of the Office of the Chief of Military Intelligence (formerly Office of Strategic Studies), Ministry of Defence, Union of Myanmar for their guidance and help in the field and museum. Thanks are also due to the curators of the National Museum of the Union of Myanmar who helped us in working at that institution. P. A. Holroyd (UCMP), M. C. McKenna (AMNH), J. Alexander (AMNH), K. C. Beard (CM), D. Haldar (GSI), and Y. Chaimanee (DMR) helped us in working at their respective institutions, and offered comments. The following people also helped us with criti- cal discussions: J.-J. Jaeger and S. Ducrocq (University of Montpellier, France); and T. Setoguchi, F. Masuda, A. Yamaji, H. Kamiya, H. Matsuoka, H. Maeda, and T. Sakai (Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Japan). Y. Tomida (NSM) helped us in collecting references. This manuscript was improved by two referees, S. Ting (Louisiana State University) and P. A. Holroyd. This research was sup- ported by Overseas Scientific Research Funds (No. 14405019 to N. Shigehara) and the Grants-in-Aid for COE Research (No. 10CE2005) and for JSPS Fellows (No. 9714 to T. Tsubamoto) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. References Aung Naing Soe, 1999: Sedimentary facies of the upper part of the Pondaung Formation (in central Myanmar) bearing late Middle Eocene anthropoid primates. Jn, Pondaung Fossil Expedition Team ed., Proceedings of the Pondaung Fossil Expedition Team, p. 152-178. Office of Strategic Studies, Ministry of Defence, Yangon. 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Vertebrata PalAsiatica, vol. 19, no. 3, p. 218-227, pls. 1-2. (in Chinese with English abstract) Zhao, Z., 1983: A new species of anthracothere from Nanning basin, Guangxi. Vertebrata PalAsiatica, vol. 21, no. 3, p. 266-270, pl. 1. (in Chinese with English abstract) Zhao, Z., 1993: New anthracothere materials from the Paleogene of Guangxi. Vertebrata PalAsiatica, vol. 31, no. 3, p. 183-190, pl. 1. (in Chinese with English summary) Zong, G., Chen, W., Huang, X. and Xu, Q., 1996: Cenozoic Mammals and Environment of Hengduan Mountains Region, 279 p. China Ocean Press, Beijing. (in Chinese with English abstract) 381 382 Takehisa Tsubamoto et al. Appendix. Dental measurements (in mm) of the Pondaung Anthracotherium used in this paper (Figures 7-9). Abbreviations: L, anteroposterior length; W, buccolingual width; *, estimate; [ ] (square bracket), the data are from the literature (Pilgrim and Cotter, 1916; Pilgrim, 1928; Colbert, 1938). Upper dentition Specimen TAKA P3/ P3/ P4/ P4/ M1/ M1/ M2/ M2/ M3/ M3/ number L W L W L W L W L W NMMP-KU 0053 A. birmanicum 14.1 10.1 10.4 12.5 13.8 15.0 17.7 19.8 19.2 21.6 NMMP-KU 0056 A. sp. cf. A. crassum 23.0 26.6 28.1 31.2 NMMP-KU 0066 A. tenuis 10.8 11.4 NMMP-KU 0067 A. sp. cf. A. crassum 12.1 16.1 NMMP-KU 0070 A. birmanicum 20.2 23.2 NMMP-KU 0071 A. sp. cf. A. crassum 15.1 16.4 NMMP-KU 0074 A. sp. cf. A. pangan 13.9 18.3 NMMP-KU 0081 A. birmanicum 19.2 23.4 NMMP-KU 0082 A. birmanicum 19.4 22.6 NMMP-KU 0083 A. birmanicum 19.1 23.3 NMMP-KU 0103 A. pangan 15.9 21.2 NMMP-KU 0105 A. sp. cf. A. crassum 11.0 15.0 NMMP-KU 0106 A. sp. cf. A. birmanicum 13.7 9.9 NMMP-KU 0122 A. sp. cf. A. birmanicum 17.1° 12.2 12.5 16.6 15.2 16.5 NMMP-KU 0128 A. sp. cf. A. birmanicum 21.9 221 NMMP-KU 0215 A. sp. cf. À. birmanicum 14.9 11.6 NMMP-KU 0216 A. sp. cf. À. crassum 24.1 28.0 NMMP-KU 0275 À. pangan 38.3 45.0 NMMP-KU 0284 A. sp. cf. À. birmanicum 23.3 25.3 NMMP-KU 0325 A. tenuis 10.5 10.7 NMMP-KU 0328 A. pangan 35.6 37.0 NMMP-KU 0329 A. pangan 27.7 31.6 36.2 41.8 NMMP-KU 0379 A. tenuis 13.7 15.3 NMMP-KU 0380 A. tenuis 8.5 9.7 NMMP-KU 0385 A. tenuis 8.4 9.8 NMMP-KU 0387 A. tenuis 9.5 10.0 NMMP-KU 0388 A. tenuis 10.0 10.0 NMMP-KU 0389 A. tenuis 10.5 10.7 NMMP-KU 0401 A. sp. cf. A. birmanicum 22.8 25.8 NMMP-KU 0403 A. sp. cf. A. crassum 29.1 30.9 NMMP-KU 0404 A. sp. cf. A. pangan 34.2 36.4 NMMP-KU 0407 A. sp. cf. A. pangan 34.1 36.5 NMMP-KU 0408 A. pangan 28.1 30.0 NMMP-KU 0409 A. sp. cf. A. crassum 27.4 32.9 NMMP-KU 0410 A. sp. cf. A. crassum 20.2 25.1° 24.0 29.6 NMMP-KU 0411 A. sp. cf. A. crassum 29.8 31.7 NMMP-KU 0412 A. pangan 35.3 38.9 NMMP-KU 0413 A. crassum 12.6 15.7 16.8 17.7 21.0 23.6 NMMP-KU 0414 A. sp. cf. A. crassum 17.4 19.1 25.7 28.0 NMMP-KU 0452 A. sp. cf. A. crassum 27.9 33.0 NMMP-KU 0453 A. birmanicum 19.2 22.1 NMMP-KU 0454 A. birmanicum 19.6 21.8 NMMP-KU 0455 A. tenuis 9.3 7.0 6.7 8.5 NMMP-KU 0459 A. sp. cf. A. crassum 25.6 29.9 NMMP-KU 0463 A. sp. cf. A. birmanicum 22.3 24.5° NMMP-KU 0476 A. sp. cf. À. pangan 15.4 18.4 NMMP-KU 0480 À. pangan 17.3 21 NMMP-KU 0500 A. birmanicum 12.2 9.7 10.1 13.1 AMNH 20011 A. crassum 16.5" 11.3 11.3 14.5 16.0 17.3 20.0 23.3 23.7 24.8 AMNH 20015 A. birmanicum 20.0 23.3 AMNH 20017 (right) A. tenuis 8.4 10.0 12.0 13.5 14.7 16.3 AMNH 20017 (left) A. tenuis 10.8 7.6 8.2° 9.6 8.8 10.2 11.9 13.5 14.9 16.1 AMNH 20024 A. crassum 2007 7257 7291000255 AMNH 20027 A. crassum 12.5" 17.6 16.0 18.9 19.9 24.9 26.3 28.4 AMNH 32525 A. crassum 13.0 16.2 17.3° 18.9 AMNH 32526 A. pangan [24] [29] 32.3 36.5 Anthracotheriidae from Myanmar 383 Specimen Taxa P3/ P3/ P4/ P4/ M1/ M1/ M2/ M2/ M3/ M3/ number iL W L W L W L W L W GSI B603 À. crassum 21.2 25.4 GSI B604 A. crassum 15.6 11.2 GSI B608 A. pangan 24.6 20.4 GSI B609 A. pangan 32.8 34.8 GSI B610 A. pangan 26.3 30.3 GSI B6ll A. crassum 14.4 18.8 GSI B615 A. crassum (type) 21.7 25.1 27.6 31.2 GSI B616 A. pangan 15.9 19.9 GSI B618 A. pangan 24.2 19.3 GSI B619 A. pangan (type) DAL 30.0° 34.0 36.4 GSI B621 A. birmanicum (type) 14.6 9.6 9.3° 11.8 13.0° 14.0° 15.0 16.8 16.7 19.0 GSI B622 A. tenuis 12.1 12.9 14.6 15.6 GSI B625 A. tenuis (type) 9.7 9.5 GSI B748 A. pangan 215% 21725 16.2 22.3 GSI B750 A. pangan [28.1] [30.8] 36.4 38.4 GSI B752 A. pangan 33.4 39.8 GSI B756 (right) A. tenuis 11.6 7172 8.9 10.4 8.5 10.7 11.9 13.5 15.6 17.0 GSI B756 (left) A. tenuis 92 10.4 8.9 10.7 12.3 13.5 GSI B763 A. crassum 27.6 30.0° Lower dentition Specimen Taxa P/3 P/3 P/4 P/4 M/1 M/1 M/2 M/2 M/3 M/3 number L W IL W L W L W L W NMMP-KU 0052 A. tenuis 10.6 5.1 9.1 5.8 12.0 7.3 19.0 8.3 NMMP-KU 0062 A. sp. cf. A. crassum Dip 19.8 NMMP-KU 0063 A. tenuis 9.1 5.9 NMMP-KU 0077 A. sp. cf. A. crassum 43.1 23.5 NMMP-KU 0079 A. sp. cf. A. birmanicum 16.2 7.0 NMMP-KU 0086 A. sp. cf. A. crassum 15.5 8.2 NMMP-KU 0087 A. sp. cf. A. crassum 38.8° 22.3 NMMP-KU 0093 A. tenuis 18.2 8.7 NMMP-KU 0107 A. tenuis 11.5 5.0 NMMP-KU 0113 A. tenuis 10.5 5.3 NMMP-KU 0116 A. sp. cf. A. birmanicum 14.8 7.8 18.2° 12.9 NMMP-KU 0125 A. birmanicum 15.5 Si 13.5 7.4 17.9 12.6 NMMP-KU 0263 A. tenuis 20.1 10.1 NMMP-KU 0267 A. tenuis 9.2 5.9 11.2 119 NMMP-KU 0274 A. crassum 19.9 97 18.5 11.5 1797 1255 NMMP-KU 0306 A. sp. cf. A. pangan 22.8 9.6 NMMP-KU 0307 A. sp. cf. A. pangan 18.3 11.3 NMMP-KU 0330 A. crassum 24.3 18.2 39.2 21.5 NMMP-KU 0331 A. crassum 24.4 17.3 NMMP-KU 0332 A. birmanicum 28.2 14.5 NMMP-KU 0399 A. tenuis 19.3 8.2 NMMP-KU 0415 A. sp. cf. A. crassum 42.4 23.8 NMMP-KU 0417 A. sp. cf. A. crassum 40° 21.7 NMMP-KU 0418 A. pangan 31.2 26.3 NMMP-KU 0421 A. crassum 17.3 11.9 NMMP-KU 0422 A. tenuis 11.7 8.2 20.0° 10.4 NMMP-KU 0423 A. tenuis 18.3 9.0 NMMP-KU 0424 A. crassum 38.5 19.9 NMMP-KU 0426 A. crassum 233% 18.2° 39.5° 21.0° NMMP-KU 0427 A. sp. cf. A. crassum 41.6 22.4 NMMP-KU 0429 A. crassum 24.3 16.3 Bl, 20.0 NMMP-KU 0430 A. birmanicum 16.5 6.6 14.3 7.8 NMMP-KU 0432 A. sp. cf. A. crassum 15.7 8.2 NMMP-KU 0433 A. pangan 11.3 19.9 384 Specimen number NMMP-KU 0434 NMMP-KU 0435 NMMP-KU 0457 NMMP-KU 0458 NMMP-KU 0465 NMMP-KU 0466 NMMP-KU 0468 NMMP-KU 0470 NMMP-KU 0478 NMMP-KU 0505 AMNH 20006 AMNH 20011 (right) AMNH 20011 (left) AMNH 20015 (right) AMNH 20015 (left) AMNH 20017 (right) AMNH 20017 (left) AMNH 20028 AMNH 20029 AMNH 32522 GSI B605 GSI B607 GSI B612 GSI B613 GSI B614 GSI B617 GSI B620 GSI B626 GSI B627 GSI B745 GSI B751 GSI B755 GSI B760 GSI B761 GSI B767 a ee ee ee R DER DDR DDD D Takehisa Tsubamoto et al. Taxa P/3 P/3 P/4 P/4 M/1 L W L W L . pangan 17.7 12.6 . crassum 16.8 9.1 crassum tenuis 9,9° tenuis tenuis . CTassum 18.4 tenuis birmanicum 10.3 sp. cf. À. crassum 15.8 8.6 pangan . crassum 16.7 7.2 16.5 9.2 16.8° crassum birmanicum birmanicum tenuis 10.5° 4.9 10.2° 55 8.4 tenuis 10.6 4.8 10.0 5.5 8.6 crassum 18.6 8.2 17.2 9.8 crassum crassum 18.7 birmanicum [14.9] [5.8] 14.3 Us 14.0 pangan crassum [10.8] [16.7] crassum crassum 21.3 9.8 pangan 19.3 12.4 19.5° pangan tenuis 9.2 tenuis pangan 24.1 12.7 21.7 14.1 21.5° crassum 19.8 9.9 19.7 11.3 16.8 tenuis [11.7] [4.3] 11.3 5.6 9.3 . tenuis [9.1] . tenuis 11.9 3.9 . birmanicum 12.9 7.0 12.9 6.3 12.5 6.4 12.2 6.1 6.0 13.2 9.5 [11.8] 16.5° 6.0 15.0° 12.9 6.4 [5.2] 99 15.5 15.5° 13.4 [17.4] 21.9 22.6 20.5 49.5" 31.9 32.4 29.0” 28.4 20.0 19.7 37.9 29.7 527 38.2 36.7 41.7 18.0 39.2 21.0 11.2 9.4 27.0 17.3 17.3 14.9 15.0 9.0 9.3 19.9 16.0 29.7 20.5 22.2 24.5 8.7 21.8 9.4 Paleontological Research, vol. 6, no. 4, pp. 385-389, December 31, 2002 © by the Palaeontological Society of Japan SHORT NOTES Permian orthoconic cephalopods of the Ochiai Formation in the Southern Kitakami Mountains, Northeast Japan SHUJI NIKO' AND MASAYUKI EHIRO* Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, 739-8521, Japan (e-mail: niko @hiroshima-u.ac.jp) *The Tohoku University Museum, Tohoku University, Sendai, 980-8578, Japan (e-mail: ehiro@mail.cc.tohoku.ac.jp) Received May 9, 2002; Revised manuscript accepted September 10, 2002 Key words: Brachycycloceras, Lopingoceras, Middle Permian, Ochiai Formation, Orthocerida, Southern Kitakami Mountains Introduction and geologic setting Middle to Upper Permian strata in the Southern Kitakami Mountains, Northeast Japan, contain a relatively diverse orthoconic cephalopod assemblage. Although they were the subject of investigations by Hayasaka (1924), Shimizu and Obata (1936), Ouchi (1971) and Koizumi (1975), infor- mation from the Southern Kitakami Mountains has been ig- nored in modern cephalopod taxonomy owing to a lack of adequate illustrations and descriptions. Knowledge of Middle to Late Permian orthoconic cephalopods is very limited and comes mainly from the Peri-Gondwana region that includes Iran (e.g., Teichert and Kummel, 1973), Oman (Niko et al., 1996), the Salt Range (Waagen, 1879), Timor (Haniel, 1915), and the South China region (e.g., Zhao et al., 1978). Revision of the Kitakami fauna, there- fore, may be of phylogenetic and paleobiogeographic im- portance. In view of this, the present study focuses on orthocerid species from the Kamiyasse area, Miyagi Prefecture, and an adjoining area to the north in Iwate Prefecture (Figure 1). The repository for these specimens is the University Museum of the University of Tokyo (UMUT). In an earlier geologic study, Tazawa (1973) investigated the Kamiyasse area, and elucidated the detailed litho- stratigraphy of the Permian deposits as the Sakamotozawa, Kanokura and Toyoma series. With the exception of the lowest, carbonate-rich strata assigned to the Nakadaira Formation, most of these series were synthesized and as- signed in the subsequent works of Ehiro (1974, 1977) to the Ochiai Formation (Onuki, 1969), from which the present cephalopod specimens were collected. The Ochiai Formation is divisible into three members: the Toyazawa Member (Ehiro, 1977), consisting of sandstone interbedded with calcareous shale and impure limestone layers, repre- sents the middle part of the formation, whereas the un- named lower and upper members are mainly massive shale with minor amounts of conglomerate, sandstone and lime- stone. Systematic paleontology Order Orthocerida Kuhn, 1940 Superfamily Orthoceratoidea M’Coy, 1844 Family Brachycycloceratidae Furnish, Glenister and Hansman, 1962 Genus Brachycycloceras Miller, Dunbar and Condra, 1933 normale Type species. — Brachycycloceras Miller, Dunbar and Condra, 1933. Brachycycloceras sp. Figure 2.1, 2.2 Description.—Single, deformed orthocone, 56 mm in length, consisting of annulated, apical phragmocone with gently curved (exogastric?) apical shell; shell expansion rapid for orthoceratids. Prominent annulations form rounded to bluntly pointed crests and deep interspaces that appear as rounded concavities in longitudinal profile; annulations quite oblique, slope toward dorsal (?) side. Except for weak dorsal (?) sinus, sutures run roughly paral- lel to annulations. Discussion.—No siphuncular structure is preserved in this specimen. However, its rapidly expanded shell with 386 Shuji Niko and Masayuki Ehiro NORTHEAST JAPAN Sendai Figure 1. Index map of fossil localities in the Southern Kitakami Mountains (inset), using the 1:25,000 map of “Shishiori” published by the Geographical Survey Institution. gently curved apical part and strongly prominent annula- tions warrant generic assignment to Brachycycloceras. In addition to Brachycycloceras sp. from the Early Permian of western Australia (Teichert, 1951) and B. rustagense Niko, Pillevuit and Nishida, 1996, from the Wordian (Middle Permian in a three-fold division) of the central Oman Mountains, this discovery represents the third Permian oc- currence of the genus. Material examined and occurrence.—UMUT PM 28065. This specimen was recovered as float from shale in the Funaochi-zawa Valley at locality KA-1 (Figure 1). Judging from the lithofacies of the matrix, the geology around this locality, and the associated ammonoid fauna, it was probably derived from the middle-upper portion (Roadian-Wordian; Middle Permian) of the lower member of the Ochiai Formation. Family Geisonoceratidae Zhuravleva, 1959 cf. Geisonoceratid, genus and species uncertain Figure 2.4, 2.7 Discussion. —A deformed body chamber of an ortho- conic shell, 115 mm in length, is available for this study. This specimen is tentatively considered to be a geisono- ceratid, because of the characteristic ornamentation of its transverse ridges that indicates asymmetrical (steep side to- wards aperture) longitudinal profiles, and because of the absence of a shell constriction. Similar ornamentation is also known to occur in some Carboniferous bactritoids, such as Ctenobactrites isogramma (Meek, 1871; Sturgeon et al., 1997, pl. 1-1, figs. 8-11, pl. 1-42, fig. 3) and Bactrites peytonensis Mapes (1979, pl. 8, figs. 7, 11), al- though characteristic dorsal carina and/or well-developed wrinkle-layer of ornamented bactritoids are not recognized in this specimen. Material examined and occurrence.—UMUT PM 28066. This specimen was recovered as float in talus deposits of shale located on a tributary of the Kuro-sawa Valley (local- ity KA-2), where the upper member is exclusively distrib- uted. Based on ammonoids collected near this locality, Ehiro and Araki (1997) inferred a late Capitanian (Middle Permian) age for the cephalopod-bearing shale of the lower part of the upper member of the Ochiai Formation. Superfamily Pseudorthoceratoidea Flower and Caster, 1935 Family Pseudorthoceratidae Flower and Caster, 1935 Subfamily Spyroceratinae Shimizu and Obata, 1935 Genus Lopingoceras Shimanskiy in Ruzhentsev, 1962 Type species.—Orthoceras lopingense Stoyanow, 1909. Other included species.—Lopingoceras acutanolatum Zhao, Liang and Zheng, 1978; L. cf. acutanolatum (this report); L. bicinctum (Abich, 1878); L. cyclophorum (Waagen, 1879); L. guangdeense Zhao, Liang and Zheng, 1978; L. hayasakai Niko and Ozawa, 1997; L. margarita- tum (Abich, 1878); L. maubesiense (Haniel, 1915); L. ? obliqueannulatum (Waagen, 1879); L. sp. (Teichert et al., 1973), and L. sp. (Zheng, 1984). Range.—Known from the late Gzhelian (Late Carbon- iferous)-early Asselian (Early Permian) boundary through the Changhsingian (Late Permian). Diagnosis.—Early juvenile shell gently curved, nonan- nulated with transverse surface lirae. See Shimanskty in Ruzhentsev (1962, p. 90) for diagnosis of adult shell, which we accept. Discussion.—The distinction between Lopingoceras and the Early Carboniferous genus Cycloceras (M’Coy, 1844; type and only reliably included species, Orthoceras laevigatum M’Coy, 1844, see Histon, 1991, and BZN 50, 1993, opinion 1720) has long been plagued by an inade- quate description of the latter’s type species. Except for dif- ferences in age range, the former differs from the latter only in the shape of annulations, i.e., Cycloceras having Permian cephalopods from Kitakami Mountains 387 Figure 2. 1,2. Brachycycloceras sp., UMUT PM 23065. 1, lateral view of silicone rubber cast, venter on left (?), x2; 2, external mold with steinkern of apical shell, note gently curved shell and sutures, venter on right (?), x3. 3. Orthocerid, superfamily, family, genus and species uncer- tain, UMUT PM 28068, side view, x2. 4, 7. Cf. geisonoceratid, genus and species uncertain, UMUT PM 28066. 4, details of surface ornamenta- tion, silicone rubber cast, x2; 7, steinkern, side view, xl. 5, 6, 8, 9. Lopingoceras cf. acutanolatum Zhao, Liang and Zheng, 1978, UMUT PM 28067, silicone rubber cast. 5, details of early juvenile shell, x4; 6, details of ornamentation of nonannulated part, x5; 8, side view, x2; 9, details of annulations, note triangular longitudinal profiles, x5. contiguous annulations with equally rounded crests and rank seems questionable in modern taxonomy. The interspaces, whereas in Lopingoceras the annulations are Kitakami material described herein includes the first known more or less distant in spacing and have triangular profiles. example of an early juvenile shell of Lopingoceras, whose Whether these external differences are of supraspecific characters add to the generic concept. The taxonomic 388 Shuji Niko and Masayuki Ehiro problem will be solved when the apical shell morphology and internal structure of Cycloceras laevigatum are known well enough for comparison with the newly refined diagno- sis of Lopingoceras. Lopingoceras cf. acutanolatum Zhao, Liang and Zheng, 1978 Figure 2.5, 2.6, 2.8, 2.9 Compare with. — Lopingoceras acutanolatum Zhao, Liang and Zheng, 1978, p. 63, 64, pl. 31, figs. 11, 12, pl. 33, figs. 3, 4. Description.—This species represented by a single exter- nal mold of gradually expanded shell, 65 mm in length, whose adoral part is strongly deformed, with no internal structure preserved; adoral end attains approximately 4 mm (reconstructed as circular cross section) in shell diameter. Nonannulated early juvenile shell gently curved, with cir- cular cross section and transverse lirae; this nonannulated part, approximately 21.5 mm in length, followed by mo- notonously annulated shell where lirae disappear; embry- onic shell may be cone-shaped; annulations may be roughly transverse with wide spacing for genus, with triangular longitudinal profiles and pointed crests; there are 1-2 annulations in corresponding reconstructed shell diameter; interspaces probably weakly depressed. Discussion.—The annulation shape and spacing of the present specimen strongly resemble Lopingoceras acutanolatum from the Wuchiapingian (Late Permian) Laoshan Shale in South China. Nevertheless, since L. acutanolatum is described from fragmentary specimens and its apical shell morphology is unknown, the Kitakami specimen is only provisionally assigned to this species. Comparison between Lopingoceras cf. acutanolatum and figured specimens from the Ochiai Formation cited as Lopingoceras ? sp. by Koizumi (1975) is impossible. Judging from his illustrations (Koizumi, 1975, pl. 4, figs. 4, 5), the specimens are inadequate for systematic treatment because of poor preservation. Material examined and occurrence.—UMUT PM 28067. This specimen was collected from a float block of shale in the riverbed of the Nidano-sawa Valley at locality KA-4. The exact stratigraphic horizon from which this block was derived is unknown, but it is highly likely that this block came from the middle part of the Toyazawa Member of the Ochiai Formation, based on its lithofacies and collected lo- cality. Thus, this specimen is considered to be of Wordian (or Capitanian) age. Superfamily, family, genus and species uncertain Figure 2.3 Discussion.—A fragmentary specimen of a deformed orthoconic shell, 22 mm in length, shows transverse lirae that consist of alternating strongly prominent and less prominent ridges. Similar ornamentation occurs in several post-Carboniferous orthocerid genera; such as the orthoceratid Trematoceras (Eichwald, 1851), the geisonoceratid Pseudotemperoceras (Stschastlivtseva, 1986), and the pseudorthoceratid Dolorthoceras (Miller, 1931). No internal structures are preserved in the present specimen, so it cannot be identified even to the superfamily level. Material examined and occurrence.—UMUT PM 28068. Same as the specimen above assigned to cf. geisonoceratid, genus and species uncertain. Acknowledgments We thank Yukihiro Takaizumi and Akihiro Misaki for collecting the present cephalopods. Helpful comments pro- vided by Royal H. Mapes and an anonymous reviewer are also appreciated. References Abich, H., 1878: Geologische Forschungen in den Kaukasischen Ländern. I. Theil., Eine Bergkalkfauna aus der Araxesenge bei Djoulfa in Armenien, 126 p., 11 pls. Alfred Holder, Wien. Ehiro, M., 1974: Geological and structural studies of the area along the Hizume-Kesennuma Tectonic Line, in Southern Kitakami Massif. Journal of the Geological Society of Japan, vol. 80, p. 457-474. (in Japanese with English abstract) Ehiro, M., 1977: The Hizume-Kesennuma Fault—with special refer- ence to its character and significance on the geologic develop- ment. Contributions from the Institute of Geology and Paleon- tology, Tohoku University, no. 77, p. 1-37. (in Japanese with English abstract) Ehiro, M. and Araki, H., 1997: Permian cephalopods of Kurosawa, Kesennuma City in the Southern Kitakami Massif, Northeast Japan. Paleontological Research, vol. 1, p. 55-66. Eichwald, E. von, 1851: Naturhistorische Bemerkungen, als Beitrag zur vergleichenden Geognosie, auf einer Reise durch die Eifel, Tyrol, Italien, Sizilien und Algier gesammelt. Nouveaux Mémoires de la Société Impériale des Naturalistes de Moscou, vol. 9, p. 1-464, pls. 1-4. (not seen) Flower, R.H. and Caster, K.E., 1935: The stratigraphy and paleon- tology of northeastern Pennsylvania. Part II: Paleontology. Section A: The cephalopod fauna of the Conewango Series of the Upper Devonian in New York and Pennsylvania. Bulletins of American Paleontology, vol. 22, p. 199-271. Furnish, W.M., Glenister, B.F. and Hansman, R.H., 1962: Brachy- cycloceratidae, novum, deciduous Pennsylvanian nautiloids. Journal of Paleontology, vol. 36, p. 1341-1356, pls. 179-180. Haniel, C.A., 1915: Die Cephalopoden der Dyas von Timor. Paläontologie von Timor, Lieferung 3, p. 1-153, pls. 46-56. Hayasaka, I., 1924: Fossils in the roofing slate of Ogachi, Prov. Rikuzen. Japanese Journal of Geology and Geography, vol. 3, p. 45-53, pl. 6. Histon, K., 1991: Cycloceras M’Coy, 1844 (Mollusca, Nautiloidea): Permian cephalopods from Kitakami Mountains 389 proposed designation of C. laevigatum M'Coy, 1844 as the type species, and proposed designation of a neotype for C. laevigatum. Bulletin of Zoological Nomenclature, vol. 48, p. 97-99. Koizumi, H., 1975: Paleozoic Cephalopods of Japan, 149 p. Teiseki Bunko, Tokyo. (in Japanese) Kuhn, O., 1940: Paldozoologie in Tabellen, 50 p. Fischer, Jena. Mapes, R.H., 1979: Carboniferous and Permian Bactritoidea (Cephalopoda) in North America. The University of Kansas Paleontological Contributions, Article 64, p. 1-75, pls. 1-41. M Coy, F., 1844: A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland, 274 p. Privately published. (reis- sued by Williams and Norgate, London, 1862) Meek, F.B., 1871: Descriptions of new species of fossils from Ohio and other western states and territories. Proceedings of the Academy of Natural Sciences of Philadelphia, 1871, p. 159- 184. Miller, A.K., 1931: Two new genera of Late Paleozoic cephalopods from Central Asia. American Journal of Science, Fifth Series, vol. 22, p. 417-425. Miller, A.K., Dunbar, C.O. and Condra, G.E., 1933: The nautiloid cephalopods of the Pennsylvanian system in the Mid-Continent region. Nebraska Geological Survey, Bulletin 9, Second Series, p. 1-240, pls. 1-24. Niko, S. and Ozawa, T., 1997: Late Gzhelian (Carboniferous) to early Asselian (Permian) non-ammonoid cephalopods from the Taishaku Limestone Group, Southwest Japan. Paleontological Research, vol. 1, p. 47-54. Niko, S., Pillevuit, A. and Nishida, T., 1996: Early Late Permian (Wordian) non-ammonoid cephalopods from the Hamrat Duru Group, central Oman Mountains. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 183, p. 522-527. Ouchi, K., 1971: Some Permian orthoconic cephalopods from the Abukuma and the Kitakami Massif. Chigakukenkyu, vol. 22, p. 133-141. (in Japanese) Onuki, Y., 1969: Geology of the Kitakami Massif, Northeast Japan. Contributions from the Institute of Geology and Paleontology, Tohoku University, no. 69, p.1-239. (in Japanese with English abstract) Ruzhentsev, V.E., 1962: Fundamentals of Paleontology (Osnovy Paleontologii). Volume V. Mollusca-Cephalopoda I. 425 p., 32 pls. Izdatel’stvo Akademii Nauk SSSR, Moskva. (translated from Russian, Israel Program for Scientific Translations, Jerusalem, 1974) Shimizu, S. and Obata, T., 1935: New genera of Gotlandian and Ordovician nautiloids. Journal of the Shanghai Science Institute, Section 2, Geology, Palaeontology, Mineralogy and Petrology, vol. 2, p. 1-10. Shimizu, S. and Obata, T., 1936: Remarks on Hayasaka’s Protocycloceras cfr. cyclophorum and the Permian and Carboniferous orthoconic nautiloids of Asia. (Résumé.). Journal of the Geological Society of Japan, vol. 43, p. 11-29. (in Japanese with English abstract) Stoyanow, A.A., 1909: On the character of the boundary of Paleozoic and Mesozoic near Djulfa. The Diary of the XIIth Congress of Russian Naturalists and Physicians in Moscow, no. 4, p. 142. (not seen) Stschastlivtseva, N.P., 1986: Nekotorye Triasovye ortotseratidy i nautilidy Severo-Vostoka SSSR (Some Triassic orthoceratids and nautilids from North-East USSR). Biulleten Moskovskogo Obshchestva Ispytatelei Prirody Otdel Geologicheskii, Novaia Seriia, vol. 61, p. 122-129. (in Russian with English abstract) Sturgeon, M.T., Windle, D.L., Mapes, R.H. and Hoare, R.D., 1997: Part 1, nautiloid and bactritoid cephalopods. Ohio Division of Geological Survey, Bulletin 71 (Pennsylvanian cephalopods of Ohio), p. 1-191. Tazawa, J., 1973: Geology of the Kamiyasse area, Southern Kitakami Mountains. Journal of the Geological Society of Japan, vol. 79, p. 677-686. (in Japanese with English abstract) Teichert, C., 1951: The marine Permian faunas of western Australia (an interim review). Paldontologische Zeitschrift, vol. 24, p. 76-90. Teichert, C., and Kummel, B., 1973: Nautiloid cephalopods from the Julfa beds, Upper Permian, Northwest Iran. Bulletin Museum of Comparative Zoology, vol. 144, p. 409-434. Teichert, C., Kummel, B. and Sweet, W., 1973: Permian-Triassic strata, Kuh-e-Ali Bashi, northwestern Iran. Bulletin Museum of Comparative Zoology, vol. 145, p. 359-472. Waagen, W., 1879: Salt-range fossils. .—Productus-Limestone fos- sils. I.-Pisces-Cephalopoda. Memoirs of the Geological Survey of India. Palaeontologia Indica, Series 13, pt. 1, p. 1-72, pls. 1-6. Zhao, J., Liang, X. and Zheng, Z., 1978: Late Permian cephalopods of South China. Palaeontologia Sinica, New Series B, no. 12, 194 p., 34 pls. (in Chinese with English abstract) Zheng, Z., 1984: Late Permian nautiloids from western Guizhou. Acta Palaeontologica Sinica, vol. 23, p. 239-253, pls. 1-4. (in Chinese with English abstract) Zhuravleva, F.A., 1959: O semeistve Michelinoceratidae Flower, 1945 (On the family Michelinoceratidae Flower, 1945). Materialy k “Osnovam Paleontologii’, part 3, p. 47-48. (in Russian) 391 The Palaeontological Society of Japan has revitalized its journal. Now entitled Paleontological Research, and published in English, its scope and aims have entirely been redefined. The journal now ac- cepts and publishes any international manuscript meeting the Society’s scientific and editorial standards. In Keeping with the journal’s new target audience the Society has established a new category of member- ship (Subscribing Membership) which, hopefully, will be especially attractive to new and existing overseas members. The Society looks forward to receiving your applications. Thank you. 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However, figures will be returned upon re- quest by the authors after the paper has been published. Ager, D. V., 1963: Principles of Paleoecology, 371p. McGraw-Hill Co., New York. Barron, J. A., 1983: Latest Oligocene through early Middle Miocene diatom biostratigraphy of the eastern tropical Pacific. Marine Micropaleontology, vol. 7, p. 487-515. Barron, J. A., 1989: Lower Miocene to Quaternary diatom biostrati- graphy of Leg 57, off northeastern Japan, Deep Sea Drilling Project. Jn, Scientific Party, Initial Reports of the Deep Sea Drilling Project, vols. 56 and 57, p. 641-685. U. S. Govt. Printing Office, Washington, D. C. Burckle, L. H., 1978: Marine diatoms. Jn, Haq, B. U. and Boersma, A. eds., Introduction to Marine Micropaleontology, p. 245-266. Elsevier, New York. Fenner, J. and Mikkelsen, N., 1990: Eocene-Oligocene diatoms in the westem Indian Ocean: Taxonomy, stratigraphy, and paleoecology. In, Duncan, R. A., Backman, J., Peterson, L. C., et al., eds.Proceedings of the Ocean Drilling Program, Scientific Results, vol. 115, p. 433-463. College Station, TX (Ocean Drilling Program). Kuramoto, S., 1996: Geophysical investigation for methane hydrates and the significance of BSR. Journal of the Geological Society of Japan, vol. 11, p. 951-958. (in Japanese with English abstract) Zakharov, Yu. D., 1974: Novaya nakhodka chelyustnogo apparata ammonoidey (A new find of an ammonoid jaw apparatus). Paleontologicheskii Zhurnal 1974, p. 127-129. (in Russian) List of reviewers 393 The co-editors are indebted to the following persons who acted as reviewers during the editing of volumes 5-6 of Paleontological Research: Ahlberg, P. E. Archbold, N. W. Clayton, G. Feldmann, R. M. Holroya, P. Ishizaki, K. Kato, H. Kitazato, H. Landman, N. H. Maeda, H. Marincovich, L. Mclay, C. Ogasawara, K. Poplin, C. Reyment, R. A. Schlirf, M. Spears, T. Takeda, M. Titova, L. Ueno, T. Yajima, M. Amano, K. Boletzky, S. von Cohen, B. L. Hayami, I. Hori, R. Kamiya, T. Kennedy, W. J. Kohno, N. Logan, A. Majima, R. Martens, K. Mori, K. Ohno, T. Popov, A. M. Ross, R. M. Scott, G. Steiner, G. Tanabe, T. Toshimitsu, S. Utting, J. Yancey, T. E. Anderson, R. O. Boltovskoy, D. Cronin, T. M. Hirano, H. Hunt, A. P. Karasawa, K. Kidwell, S. M. Kondo, Y. Maas, M. C. Mancenido, M. O. Martin, T. Murray, J. W. Okamoto, T. Popov, L. Sandy, M. Shigeta, Y. Suzuki, S. Tazawa, J. Ubukata, T. Vermeij, G. Yar, > Ss Ando, H. Chatterton, B. Engeser, T. Holmer, L. Igo, H. Kase, T. Kitamura, A. Kulicki, C. MacKinnon, D. I Mapes, R. H. Matoba, Y. Nishida, T. Padian, K. Reisz, R. R. Savazzi, E. Siddiqui, Q. A. Tabuki, R. Thomas, R. Ueno, K. Warren, A. 394 INDEX OF GENERA AND SPECIES (vol. 5, no. 1-vol. 6, no. 4: 2001-2002 ) Genera and species described in volumes 5-6 of Paleontological Research are listed in alphabetical order. The volume number, part number (in parentheses), page numbers, and figure numbers are given for each taxon. Newly proposed taxa are in bold type. A vol. (no.), page, fig (s) Abadehella'sp: 2... RE 6(4), ?, fig. 9 Acanthocythereis dunelmensis............ 6(1), 10, fig. 7 Acanthocythereis fujinaensis .......... 6(1), 5, figs. 5, 7 Acanthocythereis izumoensis .......... 6(1), 5, figs. 5, 8 Acanthocythereis koreana .............. 6(1), 10, fig. 7 Acanthocythereis tsurugasakensis ........ 6(1), 14, fig. 8 “Acanthotriletes” menendeZii............ 6(1), 27, fig. 3 Acila(Acila)ikiren'siseon sae eee 6(3), 261, fig. 3 Acila (Truncacila) cf. nagaoi .......... 6(2), 136, fig. 5 Agathammina cf. pusilla ................ 6(4), ?, fig. 9 Agathamminalasprrs ECC CE CERTES COTE 6(4), ?, fig. 9 INH ONE ATED WIROGITE 5606060000000000 5(3), 207, fig. 6 Alispiriferella japonica................ 5(4), 300, fig. 8 Alispiriferella ordinaria .............. 5(4), 300, fig. 8 Almerarhun¢hia 322 mean eee 5(4), 326 Almerarhynchia pocoviana ............ 5(4), 328, fig. 5 Alveolophragmium sp. ................ 6(2), 162, fig. 9 Ambtoniavobaids ee Soe a ee 6(1), 88, fig. 3 Ambtonia shimanensis .................. 6(1), 5, fig. 5 Ambtoniattakayasui ae ae eee 6(1), 5, fig. 5 AMMObDACUILESISD EE EE CRE tate: 6(2), 162, fig. 9 Ammodiscus' SD ee ers ee 6(2), 158, fig. 7 Amphileberis nipponica ................ 6(1), 90, fig. 5 Ancistrolepis fragilis var............... 5(3), 220, fig. 3 Anemonaria sublaevis ................ 6(3), 290, fig. 4 Angulogerina hannai ................ 6(2), 164, fig. 10 ANBUIUSEMAXINUS EEE EE CEE CETTE 6(1), 108, figs. 7, 9 Anodonta woodiana ................ 5(1), 34, figs. 1-2 Anthracohyus choeroides................ 6(4), ? fig. 10 Anthracotherium .................... 6(4), ? figs. 3-6 Arca (Arca) uedai.................... 6(2), 136, fig. 5 INA OGIO (MOVANT 6 60050000000900500 5(3), 204, fig. 3 INIA THOT, 5.0560600506000004060 6(1), 90, fig. 5 Aunilassp. serene LE CR TRES 5(4), 247, fig. 5 Aurilatspiniferaios, u 2 SU ee 6(1), 88, fig. 3 Australimoosella tomokoae.............. 6(1), 90, fig. 5 B BacıntesinagaloensWsa 6007.0606006000006 5(2), 117, fig. 2 Baectrites:sp. ss nee 5(2), 117, fig. 2 Bairdia beraguaensis.................. 6(2), 198, fig. 2 Bandicota bengalensis................ 6(3), 249, fig. 11 Bandicota sp. cf. B. bengalensis .. . .6(3), 247, figs. 9, 10 Barbatia mytiloides.................... SL) 70511239 Bathysiphon eocenica ................ 6(2), 158, fig. 7 Bathysiphon vernoni.................. 6(2), 158, fig. 7 Belbekellan. areas MAS RR Oe 5(4), 326 Belbekella mutabilis .................. 5(4), 325, fig. 4 Blasispinigenichnneedi "PRE ae eee 5(4), 300, fig. 8 Bogoslovskya omiensis................ 5(2), 116, fig. 1 Botula hortensis ...................... 5(1), 59, fig. 1 Brachyeyclocerasisp: >... Ser 6(4), ? fig. 2 Brazileabseissaslss..u.n le NEL 6(1), 34, fig. 7 Brevitriletes levis...................... 6(1), 27, fig. 3 Bseptatoechiaäinjlata 222222. 2 Er 5(4), 325, fig. 4 Buccinum aomoriensis ................ 5(3), 220, fig. 3 Buccinum bulimiloideum .............. SG) Ailes, ge, 2 Buceinumainebytum 227. 2 CREER 5(3), 220, fig. 3 Buccinum middendorffi ............ 5(3), 218, figs. 2, 3 Buccinum ochotense .................. 5(3), 218, fig. 2 Buccinum rhodium.................... 5(3), 220, fig. 3 Buccinum saitoi .................... 5(3), 218, fig. 2 Buccinum shibatense ................ 5(3), 218, fig. 2 Buccinum sinanoense ................ 5(3), 220, fig. 3 Buccinum striatissimum. . .............. 5(3), 218, fig. 2 Buccinum tsubai .................... 5(3), 218, fig. 2 Buccinum unuscarinatum . ............. 5(3), 220, fig. 3 Budashevaella sp. aff. B. multicamerata . .6(2), 158, fig. 7 Budashevaella symmetrica ............ 6(2), 158, fig. 7 Buettneria howardensis................ 6(1), 55, fig. 13 Buettneria maleriensis.............. 6(1), 43, figs. 1-16 Bulimina schwageri.................. 6(2), 164, fig. 10 Burrirhunchia®: ESS TINTIN RR EEE 5(4), 326 Burrirhynchia leightonensis.......... 5(4), 322, figs. 2, 5 C Calamospora sp. cf. C. sinuosa.......... 6(1), 27, fig. 3 @allistoeytherelalataW ar CREER 6(1), 88, fig. 3 Callistocythere asiatica ................ 6(1), 88, fig. 3 Callistocythere hatatatensis ............ 5(4), 247, fig. 5 Callistocythere hayamensis.............. 6(1), 88, fig. 3 Callistocythere japonica ................ 6(1), 6, fig. 6 Callistocythere kotorai................ 5(4), 247, fig. 5 Callistocythere kyongjuensis.............. 6(1), 6, fig. 6 Gallistocyihere sp eee eee 5(4), 247, fig. 5 Callistocyihere’ spy = 2222 22 ea ere 6(1), 88, fig. 3 Callistocythere undata ................ 6(1), 88, fig. 3 LT ITA TS ED Ree ae a Ra 6(2), 136, fig. 5 Cameleolopha (Hyotissocameleo) tissoti .............. 2 SU ee ee 5@)n783figse2; 3,3, 7 TIER ee 5(2), 90, fig. 3 Cancrinella cf. spinosa................ 5(4), 290, fig. 6 énennellat/cancrint. «isis iss (sieeve aie we os 6(3), 290, fig. 4 Cannanoropollis densus ................ 6(1), 34, fig. 7 Cannanoropollis korbaensis ............ 6(1), 32, fig. 6 Banıllomesolobus Sp.--....-:.......... 5(4), 290, fig. 6 aus see oo 6(4), ? Barlhapımnites asiaticus --............... 6(4), ? fig. 1 Carthaginites yamashitai.............. 6(4), ? figs. 2-3 SD St eee a 6(1), 90, fig. 5 Cetotheriidae gen. et sp. indet. ....6(2), 180, figs. 1, 2, 5 Chasmagnathus convexus.............. 5(4), 264, fig. 2 Chilostomella ovoidea ................ 5(3), 194, fig. 1 Chlamys (Leochlamys) namigataensis ................ N. een 6(2), 136, figs. 5, 6 ms aGroporicola: ee à 5(1), 65, fig. 5 2 2 8 Se neues oo 60 à 6(1), 107, figs. 6, 7 @ubrenlesselamaensis. -..-......:...2.: 6(2), 155, fig. 11 NER nn. re 6(2), 155, fig. 11 Cibicidoides pseudoungerianus.......... 5(3), 194, fig. 1 Brbalnsıtes molenaari: =<. <= - .. Mt. 5(1), 46, fig. 1 Cinnalepeta pulchella.................. 5(1), 27, fig. 6 Cirbroelphidium wakkanabense........ 6(2), 168, fig. 12 Cistecephaloides boonstrai............ 5(3), 187, fig. 11 Cistecephalus microrhinus........ 5(3), 179, figs. 2, 8-11 ur 6(2), 162, fig. 9 SD D... oe EN alate 6(1), 88, fig. 3 ES UDIADOnICA............... 6(1), 5, figs. 5, 6 SEIMMEMATIUEYUCTISIS ...-.... see 6(1), 5, figs. 5, 6 DA Le... RER). 6(4), ?, fig. 8 Collignoniceras praecox................ 5(1), 46, fig. 1 Collignoniceras woollgari regulare ...... 5(1), 46, fig. 1 Collignoniceras woollgari woollgari...... 5(1), 46, fig. 1 Compressoproductus corniformis........ 6(3), 290, fig. 4 Comucoquimba moniwensis ............ 5(4), 247, fig. 5 Comucoquimba saitoi ................ 5(4), 247, fig. 5 EMIRATE SAIN 520s cis vin ov sn: 5(4), 247, fig. 5 ON TIS DTA een 5(2), 90, figs. 3, 8,9 Gamumba cf ishizakii ................ 5(4), 247, fig. 5 LL LL ELU TI ES LS PPT RER A 5(4), 247, fig. 5 Cornucoquimba moniwensis............ 5(4), 247, fig. 5 Cornucoquimba saitoi ................ 5(4), 247, fig. 5 Cornucoquimba tosaensis .............. 6(1), 90, fig. 5 Costabuntonia hartmanni.............. 6(2), 200, fig. 3 Dosiatascyclus crenatus ..,............ 6(1), 32, fig. 6 EMEA DER sondes sud 6(1), 108, fig. 7, 9 LEON OPERA PET ET TE PEER 6(2), 138, fig. 6 Cravenoceras ncisum .............22. 5(3), 205, fig. 4 Erenatula nakayamai .............: 5(1), 63, fig. 4 395 Cretirhunchia bohemica .............. 5(4), 325, fig. 4 CRA CTIN IG TILL Ae Sab Ree eee Ie cg 5(4), 323 Cretirhynchia aff. cuneiformis.......... 5(4), 324, fig. 3 Cretirhynchia bohemica .............. 5(4), 325, fig. 4 Grekrhynchiasexseulptan. EN 5(4), 324, fig. 3 Gretirhynchia MINOR. slereseneeinse MMS 5(4), 324, fig. 3 Gretirhynchia,plicatilisen sun cnunan: 34) 53225 hig.2 CRATAN LAUT J pado eee eco 5(4), 324, fig. 3 Crée eee er 5(4), 324, fig. 3 Cribroelphidium ishikariense.......... 6(2), 155, fig. 11 Cribroelphidium sorachiense .......... 6(2), 155, fig. 11 Gribroelphidiumisp rennen 6(2), 168, fig. 12 Cribrostomoides sp. cf. C. cretacea...... 6(2), 158, fig. 7 GrimuesesuUbkKrOlOWIESSS re ee 5(3), 207, fig. 6 Cristatisporites inconstans .............. 6(1), 30, fig. 5 CR DIOS PLCS Pa 0.0000 0 6(4), ?, fig. 9 Gulteliustizumoensisimerien ite 6(1), 108, figs. 7, 9 Gurvemysellapaula@.r. 2.083320 ets «) ores 5(1), 67, fig. 7 Gushmanideaibhatiaiznee- ge 6(2), 200, fig. 3 GYCIAMMINAVEZOCNSIS | ser. ere 6(2), 162, fig. 9 @yclammınalpacijica sen miter aire item Ned 6(2), 162, fig. 9 GY CLAM GES rake aot rs repee evene Te 6(2), 162, fig. 9 Cyclammina sp. aff. C. pusilla.......... 6(2), 162, fig. 9 @Gyclocardiatspracer te. TE ere 6(2), 138, fig. 6 Cyclogranisporites minutus.............. 6(1), 27, fig. 3 Cyclograpsus intermedius .......... 5(4), 263, figs. 1, 2 CYCLO TISME IIS an ENTE ANNE 5(4), 323 Gyclothyristatle dyjormisı ee... eons 5(4), 321, fig. 1 Cyclothyris antidichotoma.............. 5(4), 322, fig. 2 @yelothyrissdljormise een ann ee 5(4), 321, fig. 1 Cycothyris antidichotoma.............. 5(4), 322, fig. 2 Cythere omotenipponica .............. 5(4), 247, fig. 5 GY Heel AAONANU NE ne 6(2), 198, fig. 2 (OMNB TAIT S06 5 00006500 DOO hoireteretene a 6(2), 198, fig. 2 @ytherelloidealbhatial sn). sx: o's ke 6(2), 198, fig. 2 Cytheromorpha acupunctata ............ 6(1), 88, fig. 3 Cytheromorpha godavariensis.......... 6(2), 198, fig. 2 Cytheropteron cf. sawanense .......... 5(4), 247, fig. 5 Cytheropteron RUMI tee 6(1), 94, fig. 8 Cytheropteron miurense .............. 5(4), 247, fig. 5 Cytheropteron subuchioi .............. 5(4), 247, fig. 5 Cytherura duddukuruensis Sp. nov. ...... 6(2), 202, fig. 4 CRETE tvs: ae 6(1), 90, fig. 5 D DATES CITATION ententes NE 5(3), 204, fig. 3 DAYWIIUGISDIBREAUENB nn. PNR 6(1), 94, fig. 8 DEJIERIDPEGIETUSD 4 eine Sate ss sienne 6(2), 136, fig. 5 DER ODOM A tus sh ae ee Sl) popes 2 Dendropoma annulatum ................ 5(1), 4, fig. 1 DAO VOMA SPH. + sun san. 5(1), 4, figs. 1, 3-6 Dentalina sp. cf. D. subsoluta ........ 6(2), 164, fig. 10 396 Derbyia sp. KM... 5(4), 294, fig. 7 Dielasma:sp: - =....2 000 ae nr 5(4), 300, fig. 8 Diplösphaeras Wo. u... SSSR ere 5(2), 138 Diplosphaera hexagonalis.............. 5(2), 133, fig. 2 Durrirhynchia leightonensis............ 5(4), 322, fig. 2 Dzhulfocerasick Jurnmishi ee 5(2), 113, fig. 2 Dzhulfocerasasp Wa. ee 5(2), 113, fig. 2 E Echigoceras 2... Secs eds 3. UR OO 6(4), ? Echigoceras sasakii.................. 6(4), ?, figs. 1-4 Echinauris' spe... RME ET ee 6(3), 290, fig. 4 EGRHOMIOSG SP. ze Oe OR ee 5(2), 90, fig. 3 Elphidium advenum .................. 5(3), 194, fig. 1 LEED DSTO 0 EI: 5(3), 184, fig. 7 Emydopstplatycepsiy. Er 5(3), 179, figs. 2, 5-7 EntcletestSpeian ota IT CR CT 5(4), 294, fig. 7 Entolium inequivalve.................. 5(2), 125, fig. 4 ÉOlaSiodisCUSISD (asi E ee 6(4), ?, fig. 8 Epicanites loeblichi RE. CEE EP EEE 5(3), 205, fig. 4 Eucythertraieoalae PEER EEE 5(4), 247, fig. 5 Evolutinella subamakusaensis .......... 6(2), 160, fig. 8 F Fallaxoproductus moribuensis ........ 5(4), 294, fig. 7 Falsobuntonia hayamii.............. 6(1), 88, figs. 3, 5 Falsocythere elongata ................ 6(2), 202, fig. 4 Finmarchinella japonica .............. 5(4), 247, fig. 5 Fissurina sp. cf. F. marginata ........ 6(2), 164, fig. 10 Elorinitestocculius ER EEE CEE 6(1), 32, fig. 6 Bloninitesäispin EE eter ee ons once 6(1), 30, fig. 5 Frenuling: eee Sci ee re 5(2), 92, fig. 5 Frenulina sanguinolenta .......... 5(2), 90, figs. 3, 8, 9 Fricleiaunally Aus oes ce oe Se 6(3), 317, fig. 13 Fursenkoina pauciloculata ............ 5(3), 196, fig. 2 G Galeommar ci politaye eee 5(1), 66, fig. 6 Girtyoceras meslerianum .............. 5(3), 205, fig. 4 Glandulina laevigata ovata............ 6(2), 164, fig. 10 GlobobuliminalS D 6(2), 164, fig. 10 Globocassidulina globosa ............ 6(2), 164, fig. 10 Globotruncana Arca .................. 5(4), 280, fig. 4 Globotruncana arca .................. 5(4), 280, fig. 4 Globotruncana linneiana .............. 5(4), 280, fig. 4 Gloinospira Spits CCE EE EE 6(2), 158, fig. 7 Glycymeris (Glycymeris) sp............. 6(2), 136, fig. 5 Glycymeris cisshuensis ................ 6(1), 108, fig. 7 Colas (PUIG 0000000000000000000¢ 6(3), 250, fig. 12 Golunda tatroticus .............. 6(3), 250, figs. 12-15 GONLOMYA SPAS sone poses COTE 5(2), 125, fig. 4 Granulatisporites austroamericanus....6(1), 27, figs. 3, 4 Grapsus albolineatus .............. 5(4), 264, figs. 1, 2 Grapsus tenuicrustatus ................ 5(4), 264, fig. 2 Grasishunchial EEE RCE EEE wh ee 5(4), 326 Grasirhynchia grasiana................ 5(4), 328, fig. 5 Grtapsus albolineatus ................ 5(4), 263, fig. 1 Guttulina takyanagii ................ 6(2), 164, fig. 10 Gÿpospirnifenvolalilis PAPE PEORE PEER 5(4), 300, fig. 8 H Hanaiborchella triangularis............ 5(4), 247, fig. 5 Haplophragmoides crassiformis ........ 6(2), 160, fig. 8 Haplophragmoides rugosus soyaensis . .. .6(2), 160, fig. 8 Haplophragmoides tanaii.............. 6(2), 160, fig. 8 Haplophragmoides yokoyamai.......... 6(2), 160, fig. 8 Haplophragmoidjes spp. .............. 6(2), 160, fig. 8 Hapsicytheridea undulata ............ 6(2), 202, fig. 4 Haraiborchella triangularis ............ 5(4), 247, fig. 5 IG(AUCE led o0000500000000050000 5(4), 264, figs. 1, 2 Hemicythere kitanipponica ............ 5(4), 249, fig. 6 Hemicytherura cuneata................ 5(4), 249, fig. 6 Hemicythenunaspp: 2 CCC PETER 6(1), 90, fig. 5 Hemigrapsus sanguinensis .......... 5(4), 264, figs. 1, 2 Hermanites posterocostatus ............ 5(4), 249, fig. 6 ISAAVA OOS. GOMIDYs 6050556500000000038 6(2), 202, fig. 4 Heterolepa poronaiensis.............. 6(2), 155, fig. 11 Heterolepa subhaidingeri.............. 5(3), 194, fig. 1 Holcopocythere bassiporosa............ 6(2), 200, fig. 3 Hornibrookella tewarii................ 6(2), 202, fig. 4 Horriditriletes ie smic TER 6(1), 31 Horriditriletes ramosus ................ 6(1), 27, fig. 3 Horriditriletes ramosus ................ 6(1), 28, fig. 4 Horriditriletes uruguaiensis ............ 6(1), 27, fig. 3 Horriditriletes uruguayensis ............ 6(1), 28, fig. 4 Hourcgquia RAA EEE 1er 5(2), 105, figs. 6-8 Hourequianıngens PPT 5(2), 103, figs. 2-5 Hourcquia kawashitai ............ 5(2), 107, figs. 9-12 Hustedia ratburiensis ................ 5(4), 300, fig. 8 Hyotissocameleo .......................... 5(2), 83 Hypoturrilites On AN Ben toe 5(4), 229 Hypoturrilites gravesianus ............ 5(4), 230, fig. 1 Hypoturrilites komotai ................ 5(4), 232, fig. 3 Hypoturrilites nodiferus ............ 5(4), 236, figs. 6-7 Hypoturrilites wrighti.............. 5(4), 230, figs. 1-2 Hypoturrilites yabei .................. 5(4), 235, fig. 5 I UTES. Mae: 0 0000000000005 00000800 6(1), 34, fig. 7 Inoceramus teshioensis................ 5(2), 105, fig. 6 Ishizakiella miurensis................ 6(1), 88, figs. 3, 5 Isognomon (Hippochaeta) hataii...... 6(2), 136, figs. 5, 6 Isognomon (Hippochaeta) maxilatus ...... 5(1), 70, fig. 9 Ityophorus undulatus................ 6(1), 76, figs. 3, 4 J Jolonica nipponica................ 5(2), 90, figs. 3, 8, 9 Juresania cf. juresanensis.............. 5(4), 290, fig. 6 K A SD ee ee ce ee dt wie cue tee 6(4), ?, fig. 9 SEE SD coc, caine sac eo wid cee hla 6(3), 290, fig. 4 Kawingasaurus fossilis .............. 5(3), 187, fig. 11 Kixicibcga bizijuebsus ................ 5(4), 248, fig. 6 Kobayashiina donghaiensis.............. 6(1), 90, fig. 5 Kotoracythere abnorma................ 5(4), 249, fig. 6 Kotoracythere tsukagoshii ............ 6(1), 5, figs. 5, 6 NS RME eo to 6(3), 322 Krasnoyarichthys jesseni.............. 6(3), 323, fig. 2 ALL LOTO TT AREAS Sat oo 6(2), 200, fig. 3 EE ES 6(1), 90, fig. 5 L Laevigatosporites vulgaris .............. 6(1), 30, fig. 5 (lee UE 7 EEE TER 6(2), 164, fig. 10 Lahirites segmentatus .............. 6(1), 35, figs. 8, 9 Lamellaerhunchia geokderensis ........ 5(4), 328, fig. 5 ET 222 NON TEL a ete, ESS 5(4), 326 Laperousecythere ikeyai.............. EPS es SN 7, ELLE ON. ie PE SEELEN AT a cess swe wes tba 5(2), 90, fig. 3 ERBE ac 5(2), 96, figs. 8, 9 LS aE Ge rae 61), 27) fig. 3 ID SY A 4420.00. oh oe «NATION 6(2), 164, fig. 10 MPRMMMUSIIODIS ER 5(4), 294, fig. 7 PMMA ETES OO STOO oink wore 5(2), 125, fig. 4 AU 2 ccc cvstscwecess 5(1), 67, figs. 7, 8 Linoproductus lineatus ................ 5(4), 290, fig. 6 PPDA SDL eu: LU Ut 5(1), 65, fig. 5 Lopingoceras cf. acutanolatum............ 6(4), ? fig. 2 Loxoconcha japonica........ 6(3), 266, figs. 1, 3, 5, 7, 9 Loxoconcha lilljeborgii ........ 6(3), 269, figs. 3, 5, 7, 9 Loxoconcha nozokiensis .............. 5(4), 249, fig. 6 BPACONENG DDIMUL . ner de ee 00 te 6(1), 88, figs. 3, 5 ERSDCONCNG Optima, wiesen ser ex 00e 6(3), 266, fig. 1 PRAROCONICNA DOM AD cls een see 6(3), 266, fig. 1 DOLOCONCNA DUICHTA tr, 620s vies owe de 6(1), 88, figs. 3, 5 ERP ONCI DUR sun a nes een nee 6(3), 266, fig. 1 Loxoconcha shanhaiensis ........ 6(3), 270, figs. 4-7. 9 ERA OEIL IE BID: Ananas ann hl ehe 6(1), 90, fig. 5 Loxoconcha tosaensis .............. 6(1), 88, figs. 3, 5 397 Loxoconcha tumulosa............ 6(3), 270, figs. 4, 5, 9 Loxoconcha uranouchiensis ............ 6(1), 90, fig. 5 Loxoconcha uranouchiensis ............ 6(3), 266, fig. 1 WOXOCONCHANV VAE ee nee ec 6(1), 88, figs. 3, 5 BOXGCOINICWIUMESPE ne sense 5(4), 249, fig. 6 Lunucammina cf. palmata................ 6(4), ?, fig. 8 M RER SON obs 6(2), 138, fig. 6 Nine sde a 8 A ARI ee Pe IRRE RR 6(2), 213 MOI OMR ES os ee 6(2), 214, figs. 3, 4, 5 Malleus anatinus (Gmelin).............. 5(1), 60, fig. 2 Malleus malleus (Linnaeus) ............ 5(1), 60, fig. 2 Mantellicera japonicum................ 5(4), 234, fig. 4 Marathonites invariabilis .............. 5(3), 206, fig. 5 MariellanMariella) FAC RE 5(3), 173 Mariella (Mariella) aff. circumtaeniata. .5(3), 175, fig. 11 Mariella (Mariella) cenomanensis...... 5(3), 174, fig. 10 WAT LIRIGISD RS. ee Mars anna str nt 5(4), 300, fig. 8 IVIGyEIRTODSISUSDE SS rennen ke 5(4), 300, fig. 8 Mawsonia brasiliensis................ 6(4), ?, figs. 1-4 Megacricetodon gregarious ............ 6(3), 246, fig. 8 Megalodon (Megalodon) yanceyi...... 6(1), 70, figs. 3-4 Mesangulus Maximus 3-2-6 6(2), 138, fig. 6 WBGONSTIS DS 85 SEUSS ee tere 5(4), 290, fig. 6 MELON STATE serie ee ete ees 6(2), 155, fig. 11 Melonisypompilioideses 12 2.2 2332: 6(2), 155, fig. 11 Meristocorpus explicatus................ 6(1), 35, fig. 8 Meristocorpus ostentus ................ 6(1), 34, fig. 7 WH AXOUMB IGS MD ae eee celle ee 5(3), 171 Mesoturrilites aff. corrugatus .......... 5(4), 238, fig. 8 Mesoturrilites cf. aumalensis .......... 5(3), 166, fig. 3 Mesoturrilites pombetsensis ........ 5(3), 172, figs. 8, 9 Metaplaxserenulataseen sonen... 5(4), 264, figs. 1, 2 Metoposaurus diagnosticus ............ Sl Sl 1) Metoposaurus ouazzouri .............. 6(1), 55, fig. 13 Dillardtanmellad EE PE 6(3), 254, fig. 16 Miosesarma japonicum................ 5(4), 269, fig. 4 Miosesarma naguraense .............. 5(4), 269, fig. 4 Modiolusimaedaeau ee 00e 5(2), 124, figs. 3-5 IMDNABSPSAMNe em ee ame a, An 6(1), 108, fig. 7 Munseyella hatatatensis .............. 5(4), 248, fig. 6 Munseyella hatatatensis ................ 6(1), 6, fig. 6 Munseyella hatatatensis .............. 5(4), 249, fig. 6 MANS EYE LMI eee ee Shane 6(2), 198, fig. 2 Muricidae? gen. and sp. indet........... 6(2), 136, fig. 5 Mus (Pyromys) saxicola .............. 6(3), 241, fig. 2 MASSE Vapi Sosa) PANNE Ut 6(3), 242, figs. 3, 8 IMUS ANUS CHIUST en taie ere cy en ee see 6(3), 243, figs. 4, 5 Mus musculus tytelri ............ 6(3), 241, figs. 2, 6, 7 MVILUSESAMICOLD EMA ae een ee 6(3), 244, fig. 6 Myalina (Myalina) cf. wyomingensis......6(1), 71, fig. 4 398 Mysellarnss KEN: Me ee Pee 5(1), 68, fig. 8 Mysellaispel 88.60.0556 <5 ae ee 5(1), 67, fig. 7 N INGnkinellaysps es ARNO 6(4), ?, fig. 8 Nanlingella cf. meridionalis.............. 6(4), ?, fig. 8 Naticidae? gen. and sp. indet. .......... 6(2), 136, fig. 5 INeocyprideisyrao nr 6(2), 198, fig. 2 Neomonoceratina paraoertlü .......... 6(2), 200, fig. 3 Neonesidea oligodentata................ 6(1), 90, fig. 5 Neopellucistoma inflatum .............. 6(1), 88, fig. 3 Neopronorites skvorzovi .............. 5(3), 204, fig. 3 INGOSDIN EC AS CIRE RE EEE RCE 5(4), 300, fig. 8 INGOSDUVET So ocococ00o 0 00%coovo0vo 6(3), 290, fig. 4 Neospiriferinae gen. and sp. indet. ...... 6(3), 290, fig. 4 Nerita (Theliostyla) albicilla.......... 5(1), 22, figs. 1-5 Nipponocythere bicarinata.............. 6(1), 90, fig. 5 IN@OUOMPANOTIA SEE 0 00 000000000000 6(4), ?, fig. 9 Nonionella japonica ................ 6(2), 155, fig. 11 Nordophiceras jacksoni................ 5(3), 208, fig. 7 Nucleolina diluta .................... 6(2), 202, fig. 4 INUGUIGIS D5 Meise RER ARTS 6(1), 108, fig. 7 O Orbiculoidea cf. jangarensis............ 5(4), 290, fig. 6 Orbirhynchia rss oxic axe UPTO 5(4), 320 Orbirhynchia aff. boussensis .......... 5(4), 322, fig. 2 Orbirhynchia reedensis................ 5(4), 322, fig. 2 Oridorsalis umbonatus ................ 5(3), 197, fig. 3 Oxylomalelonens 2.22.22, EEE 5(2), 125, fig. 4 P PATATE EE EE beccocoode 6(4), ?, fig. 9 Paijenborchella cf. tsurugasakensis ...... 6(1), 10, fig. 7 Paijenborchellina indica .............. 6(2), 204, fig. 5 Paijenborchellini gen. et sp. indet. ...... 6(2), 200, fig. 3 Bakkokunyusulahinii 5000000e000000000000 6(4), ? fig. 2 POlaCOJUSUINAISDE SE EL 6(4), ?, fig. 8 Palmenella limicola .................. 5(4), 249, fig. 6 Palmenella limicola.................... 6(1), 10, fig. 7 Palmoconcha irizukii.................... 6(1), 5, fig. 5 JHA PUCORET WOH 650000000000000006 6(2), 202, fig. 4 Paracandona andhraensis ............ 6(2), 204, fig. 5 Paraceltitesyelegansy. 1... rannte: 5(3), 208, fig. 7 Paracypris khuialaensis .............. 6(2), 204, fig. 5 Paracytheridea neolongicaudata ........ 5(4), 249, fig. 6 Paradoxostomatidae spp. .............. 6(1), 90, fig. 5 Parakrithella pseudodonta .............. 6(1), 88, fig. 3 Parapelomys robertsi ................ 6(3), 254, fig. 16 Parasphenarina cavernicola........ 6(3), 301, figs. 2-12 Parasphenarina. 2... CM seine ee 6(3), 301 Battalophyllialsp rn. 5(1), 59, fig. 1 Pedum spondyloideum.................. 5(1), 65, fig. 5 Peppersitesyellipticusper.. ttre oe 6(1), 32, fig. 6 Percnon planissimum .............. 5(4), 263, figs. 1, 2 Perissocytheridea japonica.............. 6(1), 90, fig. 5 Perissocytheridea sp................. 6(1), 88, figs. 3, 5 Permundaria asiatica ................ 5(4), 294, fig. 7 Phacosoma chikuzenensis.............. 6(1), 108, fig. 7 Phlyctocythere japonica ................ 6(1), 88, fig. 3 IAT HOUP IAS [NIG 6500669000050000000006 5(2), 90, fig. 3 Pistothyrisispa. Sees see eee 5(2), 96, figs. 8, 9 Binctadalmaeulatan m 22.22.22 2 5(1), 35, fig. 2 [PitarımatsumotoV. 2222 6(1), 108, fig. 7 Placentamminaisp 2.22. De 6(2), 158, fig. 7 Plagusiaidentipes 222.2, 5(4), 263, figs. 1, 2 Pleuromya hidensis .................. 5(2), 125, fig. 4 Plicatipollenites gondwanensis .......... 6(1), 34, fig. 7 Blieifuseusichnplieatusen.n 2.22 CREER 56) 22022 Popanoceras annae .................. 5(3), 206, fig. 5 Poronaia poronaiensis ................ 6(2), 162, fig. 9 Portlandia (Portlandella) watasei ...... 6(3), 261, fig. 3 Potonieisporites brasiliensis ............ 6(1), 32, fig. 6 Potonieisporites densus ................ 6(1), 32, fig. 6 Potonieisporites elegans................ 6(1), 32, fig. 6 Potonieisporites novicus................ 6(1), 32, fig. 6 Potonieisporites ovatus ................ 6(1), 32, fig. 6 Potonieisporites simplex................ 6(1), 32, fig. 6 Potonieisporites Sp..................... 6(1), 34, fig. 7 Potonieisporites triangulatus ............ 6(1), 32, fig. 6 Praeglobobulimina pyrula ............ 6(2), 164, fig. 10 Prionocyclusyeermanl 2... eee 5(1), 48, fig. 2 PrionocyclUSNh ati 22. eee 5(1), 48, fig. 2 Prionocyclus macombi 2.22... 5(1), 48, figs. 2, 4 Prionocyclus novimexicanus ............ 5(1), 48, fig. 2 Prionocyclus wyomingensis.............. 5(1), 49, fig. 3 Pristerodon mackayi ............ 5(3), 179, figs. 2-4, 7 Procerolagena sp. cf. P. gracilima ....6(2), 164, fig. 10 Protocar SPECTRE 5(2), 125, fig. 4 Protohaploxypinus amplus .............. 6(1), 35, fig. 8 Protohaploxypinus bharadwajii ...... 6(1), 34, figs. 7, 8 Protohaploxypinus sp. cf. Striatopodocarpites MARUI CUS) sa en ee IO 6(1), 35, fig. 8 Pseudoaunilayjaponicaserr 1 eee 6(1), 90, fig. 5 Pseudonodosaria sp. cf. P. conica...... 6(2), 164, fig. 10 Pseudopolymorphina sp............... 6(2), 164, fig. 10 Pseudovidalinayspos 2 eee 6(4), ?, fig. 9 Pterelectroma zebra .................. 5(1), 63, fig. 4 Ptychognathus sp. aff. P. ishii.......... 5(4), 264, fig. 2 Pullenia eocenica .................. 6(2), 155, fig. 11 Izulleniansalisbunyin 2... 17.22 nee 6(2), 155, fig. 11 Punctatisporites gretensis .............. 6(1), 27, fig. 3 Punctatisporitessspacnt cia eee 6(1), 27, fig. 3 Q Quinqueloculina seminula compacta . . . .6(2), 164, fig. 10 R Raistrickia cephalata................ 61); 27, fies. 3,9 Raistrickia sp. cf. R. saetosa ............ 6(1), 27, fig. 3 LET RETTIG Ty ee a cree eue 6(4), ?, fig. 9 Rectobolivina asanoi .......... 6(2), 224, figs. 4, 10, 13 Rectobolivina bifrons.......... 6(2), 224, figs. 4, 8, 9, 13 Rectobolivina clavata ............ 6(2), 224, figs. 4, 10 Rectobolivina clavatostriatula ........ 6(2), 232, fig. 13 Rectobolivina distontinuosa ....6(2), 224, figs. 4, 10, 13 Rectobolivina raphana........ 6(2), 224, figs. 4, 8, 11, 13 Rectobolivina striatula ............ 6(2), 224, figs. 4, 11 Recurvoidella sp. cf. R. lamella ........ 6(2), 160, fig. 8 II HAYS DS SCR Eee eee 6(2), 160, fig. 8 ES TMS © (cco memes nase 5(4), 234, fig. 4 Reichelina changhsingensis .............. 6(4), ?, fig. 8 AID DETTES IS dm nie si mte mere os ne sie 6(2), 158, fig. 7 LUE TE UTP SORA 5(4), 290, fig. 6 Reticulophragmium amakusaensis ...... 6(2), 162, fig. 9 SD roe ec Se ace cee ee ee 5(4), 300, fig. 8 WSO ST eG eg Sa IE 5(1), 61, fig. 3 Robertsonites cf. tuberculatus............ 6(1), 14, fig. 8 Robertsonites japonicus ................ 6(1), 14, fig. 8 Robertsonites reticuliformus ............ 6(1), 14, fig. 8 PES SD Nels cic ccc 2222200 5(4), 249, fig. 6 Robertsonites yatsukanus.............. 6(1), 5, figs. 5, 8 228 SETS Te ane an Pe 6(1), 90, fig. 5 MASINI ONTHCTUG Se 2 ne ones ee © euere 5(4), 280, fig. 4 RAA LE LIOIMUS - 2220202222200. 5(4), 280, fig. 4 BEBUGERGESIMETE? SD... ceases 5(4), 249, fig. 6 Rugosochonetidae gen. et sp. indet....... 6(3), 290, fig. 4 S EHRE a foo ne PP PRE 6(1), 108, fig. 7 LUE DU IT EP P] 01 ORNE RER 6(1), 69, fig. 2 Schizocythere hatatatensis.............. 5(4), 249, fig. 6 Schizocythere kishinouyei.............. 5(4), 249, fig. 6 TN no Dunes oo do ce à 5(1), 66, fig. 6 RE DNS Be dame 6(1), 90, fig. 5 Semicytherura diluta ................ 6(2), 204, fig. 5 Semicytherura henryhowei ............ 5(4), 249, fig. 6 TRE DENT ADD ec den mms moe 6(1), 90, fig. 5 Le LEE DT Die RP EE oe ars ears, ER we 5(4), 326 Septatoechia aff. Rhynchonella baugasii. .5(4), 325, fig. 4 Septatoechia amudariensis ............ 5(4), 325, fig. 4 BEUIHDECHURHHUNG nee réeeenns es 5(4), 325, fig. 4 Septifer (Mytilisepta) sp. .............. 6(2), 136, fig. 5 Sesarma (Parasesarma) pictum ........ 5(4), 264, fig. 2 399 Sesarma (Perisesarma) bidens.......... 5(4), 263, fig. 1 Sesarmops intermedium ............ 5(4), 263, figs. 1, 2 Shimodaia pterygiota.............. 5(2), 90, figs. 3, 8, 9 Siamotherium pondaungensis.............. 6(4), ? fig. 2 Sıemoidellaapatijiean se. 6(2), 164, fig. 10 Siphogenerina striatula .............. 6(2), 232, fig. 13 SKGLLEROSISDIE develo CRE eee eee eee 5(2), 127, fig. 6 Solemya SUDTAIUTETSIS ee eee ec ee clone 5(2), 125, fig. 4 SPEIREOWIIETESERT ee esse seen 6(1), 33 Spelaeotriletes arenaceus .............. 6(1), 30, fig. 5 Spelaeotriletes triangulus .............. 60) 30075 SPIRHEBerISITUTAyReNSISE eee ACID), OÙ, TS SBINTIEbErISIHUICHTaM ee ce ce 6(1), 90, fig. 5 Spinileberis quadriaculeata.............. 6(1), 88, fig. 3 D DIE OLTISESD Eee ec ee ee ene 5(4), 249, fig. 6 SDI AAA AREA) RE ST ee 6(3), 290, fig. 4 SDA IRA LIZ Een ee Sees 5(4), 300, fig. 8 SPU CLEUGSDETSANANGC eile nn: 6(3), 290, fig. 4 SPURELCDEL ISHS a.m cere eee mers cls een‘ 5(4), 248, fig. 6 SDITODIYEUNSAISD RC ee ee eee ae 5(2), 127, fig. 6 SIEJANINIENANCOLOSUN eee ere: SU) Seh iy, 1 Stenoscisma margaritovi .............. 5(4), 300, fig. 8 Striatoabieites sp. cf. S. anaverrucosus....6(1), 35, fig. 8 SITIAIOHDAGCATDUESISPE ee ee ce Gi) Hoa ies Striatopodocarpites sp. cf. S. phaleratus ..6(1), 34, fig. 7 SUTIGIOSOTITESWNEVICTI ee ee oe ee cle: 6(1), 30, fig. 5 Striomonosaccites ovatus ............ 6(1), 34, figs. 7, 9 SHODOLINGSDS tec somes cee ee ehe 6(2), 168, fig. 12 Subprinocyclus minimus .............. 5(2), 104, fig. 3 SUDPTINOGYCIUS| NEPLUM os. ie es 5(2), 105, fig. 6 Subprionocyclus minimus .............. SC) 103 mince T TGCHNASPOTITESISD eto ee een 6(1), 35, fig. 8 URAN ERA AM RE dre à 6(2), 138, fig. 6 Terebratalia coreanica............ 5(2), 90, figs. 3, 8,9 HCIOVIMY AICATINGD ee 5(2), 124, figs. 3-5 Thalassoceras gemmellaroi ............ 5(3), 207, fig. 6 Dhraciasshokawensis: Ca 5(2), 125, fig. 4 Trachyleberis ishizakü 7.055. 6(1), 92, fig. 7 Trachyleberis scabrocuneata ............ 6(1), 88, fig. 3 TraeNyleberssispn mann aes + 5(4), 247, fig. 5 Iransennana grafiosa sas ese ee hs on os 5(4), 290, fig. 6 UT EPLOCETAS) YOKOVAIIGY. Seen 6(1), 123, fig. 1 Trochammina sp. cf. T. asagaiensis ....6(2), 164, fig. 10 Trominina hokkaidoensis .............. 6(3), 261, fig. 3 MOTTE S TRE er diese sat à 5(3), 163 COTON COWS 556600000005 00040 5(3), 166, figs. 3, 5, 6 LATTES AECOS OMS te ee ee een 5(3), 166, fig. 3 Turrilites complexus .............. 5(3), 164, figs. 1-4 IMMER) GOS en 5(3), 166, figs. 3, 4 DUTT BLES WOK seen nen IS) Oe, 7) 400 Turrilites scheuchzerianus .......... 5(3), 166, figs. 3, Turritella:sp..>- cisions S25 Sm Sem ae 6(3), 261, fig. U Uraloceras Spa x os. acc ont ve eee ae. 5(3), 206, fig. Urocythereis pohangensis .............. 6(1), 10, fig. Uroleberis rasilis .................... 6(2), 204, fig. Urushtenoidea crenulata .............. 5(4), 294, fig. V VallatisponitesunussoW rer 6(1), 30, fig. Vallatisporitesusps ore er 6(1), 30, fig. Vellatisporites arcuatus Venericardia subnipponica . Verrucosisporites andersonü ............ 6(1), 30, fig. Verrucosisporites sp. cf. V. morulatus ....6(1), 27, fig. Vervilleina:sps 22. 2542525 see een 6(4), ?, fig. ee RE 6(1), 30, fig. ..-6(1), 107, figs. 6, 7, 9, 10 4 3 SN D 5 5 5 5 3 9 Vidrioceras’spe „22222200 ee 5(1), 15, figs. 1- Vulsellasvulsella zn 5(1), 59, fig. W Waagenoconcha cf. imperfecta.......... 5(4), 294, fig. Waagenoconcha permocarbonica........ 5(4), 294, fig. xX Xestoleberis opalescenta................ 6(1), 88, fig. Xestoleberis Sppi. - -- 2... 0 02 0 SE 6(1), 90, fig. Xestoleberis subglobosa .............. 6(2), 204, fig. Y Yakovlevia kaluzinensis................ 5(4), 290, fig. Yezocythere gorokuensis SAT RD RE CRIER 5(4), 247, fig. Yoldid SP} ln Seas an 6(1), 108, fig. 3 1 ~ Nn Nn CONTENTS Vol. 5 No. 1 (April 30, 2001) Takao Ubukata: Morphological approaches in paleobiology .................................. Enrico Savazzi: Morphodynamics of an endolithic vermetid gastropod .......................... Kazushige Tanabe, Cyprian Kulicki, Neil H. Landman and Royal H. Mapes: External features of embry- onic and early postembryonic shells of a Carboniferous goniatite Vidrioceras from Kansas Takenori Sasaki: Macro- and microstructure of shell and operculum in two Recent gastropod species, Nerita (Theliostyla) albicilla and Cinnalepeta pulchella (Neritopsina: Neritoidea) ............ Takao Ubukata: Geometric pattern and growth rate of prismatic shell structures in Bivalvia ........ Richard A. Reyment and W. James Kennedy: Evolution in morphometric traits in North American Saliononicemunae (Ammonoidea, Cephalopoda) ES MR me ess eo 0 cess esos Enrico Savazzi: A review of symbiosis in the Bivalvia, with special attention to macrosymbiosis .. Erratum: Article by Takashi Hasegawa and Takayuki Hatsugai in Vol. 4, Nos. 2 and 4 ............ Vol. 5 No. 2 (June, 29, 2001) Mohamed Zakhera, Ahmed Kassab and Kiyotaka Chinzei: Hyotissocameleo, a new Cretaceous oyster subgenus and its shell microstructure, from Wadi Tarfa, Eastern Desert of Egypt ............ Michiko Saito and Kazuyoshi Endo: Molecular phylogeny and morphological evolution of laqueoid DM EMETIIS 2: cp oosadestise. HOee See dt SCOR UE OO EE He Conca Gil Iai Sei rain Fumihisa Kawabe and Yasunari Shigeta: The genus Hourcquia (Ammonoidea, Pseudotissotiidae) from the Upper Cretaceous of Hokkaido, Japan: biostratigraphic and biogeographic implications ...... Masayuki Ehiro: Some additional Wuchiapingian (Late Permian) ammonoids from the Southern LAER ARGS INR AS A DATE EE AN = gO ministres ea Shuji Niko: Middle Carboniferous orthoconic cephalopods from the Omi Limestone Group, Central Chiu of na TUT cie aus ma on do ne chu ein ie Pees 0e Toshifumi Komatsu, Ryo Saito and Franz T. Fürsich: Mode of occurrence and composition of bivalves of the Middle Jurassic Mitarai Formation, Tetori Group, Japan ............................ Noritoshi Suzuki and Kazuhiro Sugiyama: Regular axopodial activity of Diplosphaera hexagonalis CRC S PRET OT AUIS UNE AN RATIOIATIA) 2e en eee dec cu RTE BEIN Ss nn oye ee ie Dies eiete echo che ct lieu: Bes iaueese.s Vol. 5 No. 3 (September 28, 2001) Keiichi Hayashi: Ostracode biostratigraphy of the Lower Cretaceous Wakino Subgroup in northern JOINT TENT A less Do MALE DR RO CO ITO Dé CE ICE Tatsuro Matsumoto and Takemi Takahashi: Further notes on the turrilitid ammonoids from Hokkaido- Part 2 (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XC) .............. Sanghamitra Ray: Small Permain dicynodonts from India .................................... Ritsuo Nomura: Quantification of optically granular texture of benthic foraminiferal walls ........ Yasunari Shigeta, Yuri D. Zakharov and Royal H. Mapes: Origin of the Ceratitida (Ammonoidea) in- Éd RONDE CAE IHICHTEAISHEN. ICAEUTES en Kazutaka Amano and Mikiko Watanabe: Taxonomy and distribution of Plio-Pleistocene Buccinum (uastzopoda, DCE) un tortheast JAPAN) Zee een none HUN RAG ed Ba Sees se ne cies ER ASIA HR 401 Page Figures 77-86 87-100 101-109 111-114 115-120 1211722) 131-140 141-142 143-162 163-176 Won 193-200 201-213 2192/26 227-228 402 Vol. 5 No. 4 (December 31, 2001) Tatsuro Matsumoto and Takemi Takahashi: A study of Hypoturrilites (Ammonoidea) from Hokkaido (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin-XCI) .................. Tatsuhiko Yamaguchi and Hiroki Hayashi: Late Miocene ostracodes from the Kubota Formation, Higashi-Tanagura Group, Northeast Japan, and their implications for bottom environments Hiroaki Karasawa and Hisayoshi Kato: The systematic status of the genus Miosesarma Karasawa, 1989 with a phylogenetic analysis within the family Grapsidae and a review of fossil records (Crustacea: Decapoda: Brachyura) Sean. sg So ee erie ea terre Kazuyoshi Moriya, Hiroshi Nishi and Kazushige Tanabe: Age calibration of megafossil biochronology based on Early Campanian planktonic foraminifera from Hokkaido, Japan .................. Jun-ichi Tazawa: Middle Permian brachiopods from the Moribu area, Hida Gaien Belt, central Japan Kazushige Tanabe, Royal H. Mapes and David L. Kidder: A phosphatized cephalopod mouthpart from the Upper Rennsylyanianvofi@klahomas US Agari reise nena sie ee Neda Motchurova-Dekova: Taxonomic and phylogenetic aspects of the shell ultrastructure of nine Cretaceous rhynchonellide brachiopod) senerakee cee ei eee ei ee ec eee PROCEEDINGS ......:: 0 Gn ste 08224. +0.- te Sores ae Be eine eR oe ee ET ieee Vol. 6 No. 1 (April 30, 2002) Gengo Tanaka, Koji Seto, Takao Mukuda and Yusuke Nakano: Middle Miocene ostracods from the Fujina Formation, Shimane Prefecture, Southwest Japan and their paleoenvironmental signifi- CANCE 2.04 soft dass ace. ie ke doc be as “aster Ieee RE Rodolfo Dino and Geoffrey Playford: Stratigraphic and palaeoenvironmental significance of a Pennsylvanian (Upper Carboniferous) palynoflora from the Piaui Formation, Parnaiba Basin, north- easter Brazil :.:2.:.:.54.4%4.0 0er CR ce Cri nek ies ko KR LE CCE Dhurjati Prasad Sengupta: Indian metoposaurid amphibians revised ............................ Keiji Nakazawa: Permian bivalves from the H. S. Lee Formation, Malaysia...................... Yutaro Suzuki: Systematic position and palaeoecology of a cavity-dwelling trilobite, /tyophorus undulatus Warburg, 1925, from the Upper Ordovician Boda Limestone, Sweden.............. Moriaki Yasuhara, Toshiaki Irizuki, Shusaku, Yoshikawa and Futoshi Nanayama: Changes in Holocene ostracode faunas and depositional environments in the Kitan Strait, southwestern Japan ........ Norihiko Sakakura: Taphonomy of the bivalve assemblages in the upper part of the Paleogene Ashiya Group; southwestern Japan =... sieve ccs Eee role DORE CCR ELLE LE SHORT NOTES Shuji Niko: Revison of an Ordovician cephalopod Ormoceras yokoyamai (Kobayashi, 1927)........ PROCEEDINGS: .....4 uses non eee ee Dee eee Vol. 6 No. 2 (June 28, 2002) Takashi Matsubara: Molluscan fauna of the “Miocene” Maéjima Formation in Maéjima Island, Okayama Prefecture southwest Japan) 2 eee eee eek aii eee eee eee Satoshi Hanagata: Eocene shallow marine foraminifera from subsurface sections in the Yufutsu-Umaoi district, Hokkaido, Japan 1.41: 3.00 ne OCR EE Seep ger EE Toshiyuki Kimura: Feeding strategy of an Early Miocene cetothere from the Toyama and Akeyo Formations, central Japan, 92... nee Eh OO Sues yea CR CI CEO EE. Subhash Chandar Khosla and Madan Lal Nagori: Ostracodes from the Intertrappean beds (Early Paleocene) lof theveast:coastiof Indiana N EE ET ere Hisayoshi Kato: Fossil crabs (Crustacea: Decapoda: Brachyura) from the latest Miocene Senhata Formation, Boso Peninsula, Japan 2... a. ec aes coe ete el EE CT CRE 229-240 . 241-257 259-275 277-282 283-310 311-318 319-330 331332 1-22 23-40 41-65 67-72 73-83 85-99 101-120 121-124 125-126 127-145 147-178 179-189 191-210 AAI) 15 \=3 1-18 Shungo Kawagata and Akio Hatta: Internal test morphology of the genus Rectobolivina (Cushman, 1927) from the Late Cenozoic Miyazaki Group, southwestern Japan ........................ DROCBEDINES 205 5 a cere coco 0 OC ADS DEO een Rense Vol. 6 No. 3 (September 30, 2002) Rajeev Patnaik: Enamel microstructure of some fossil and extant murid rodents of India .......... Yutaka Honda: Paleobiogeographic significance of Trominina hokkaidoensis (Hayasaka and Uozumi) (Gastropoda: Buccinidae) from the basal part of the Tanami Formation (Oligocene) of the Kii ERREUR Coe SRG EU SRE 6 hd CS Gs COG CSU rO OID RS PE ciara Gengo Tanaka and Noriyuki Ikeya: Migration and speciation of the Loxoconcha japonica species group DOS RAC OA) TM IBIAS: | oo ucldion dob ers ers UO a ale range tir ak ee Guang R. Shi, Shuzhong Shen and Jun-ichi Tazawa: Middle Permian (Guadalupian) brachiopods from the Xiujimgingi area, Inner Mongolia, northesat China, and their palaeobiogeographical and RS CAO EE see OOO GOO COCO coo Eon eine nen sic Neda Motchurova- Dekova, Michiko Saito and Kazuyoshi Endo: The Recent rhynchonellide brachiopod Parasphenarina cavernicola gen. et sp. nov. from the submarine caves of Okinawa, Japan Artem M. Prokofiev: First finding of an articulated actinopterygian skeleton from the Upper Devonian 219-236 237-238 239-258 259-263 265-284 285-297 299-319 of Siberia and a reappraisal of the family Moythomasiidae Kazantseva, 1971 (Osteichthyes) .... 321-327 CIE by Ra SMS bara in VOIMGNNO 2... ee os romeo ses es ee 329 2. DIENEN oc 5855 - $56 5586656 Re 330 Vol. 6 No. 4 (December 31, 2002) Fumio Kobayashi: Lithology and foraminiferal fauna of allochthonous limestones (Changhsingian) in the upper part of the Toyoma Formation in the South Kitakami Belt, Northeast Japan ........ Yoshikata Yabumoto: A new coelacanth from the Early Cretaceous of Brazil (Sarcopterygii, Actinistia) Shuji Niko: Echigoceras sasakii, a new Middle Carboniferous nautilid from the Omi Limestone Group, Jewel BAAD scscsssescod sco Sen ee Tatsuro Matsumoto: Turrilitid ammonoid Carthaginites from Hokkaido (Studies of the Cretaceous HN HES MONT HOKKAIGO anid SAKNAlIN—X CLV) vu var ee sea een eat Takehisa Tsubamoto, Masanaru Takai, Naoko Egi, Nobuo Shigehara, Soe Thura Tun, Aye Ko Aung, Aung Naing Soe and Tin Thein: The Anthracotheriidae (Mammalia; Artiodactyla) from the Eocene Pondaung Formation (Myanmar) and comments on some other anthracotheres from the Eocene of RSR ce al ED EE LC soos Pals) aKa OR ER Shuji Niko and Masayuki Ehiro: Permian orthoconic cephalopods of the Ochiai Formation in the BEREIT RAA IVA ONENLECAUTIS, Nentleast JAPAN)... oa ein 6 we 6.6 etaiaiets ais else Wersleidve'wie(e aig mes à1a 4 à 331-342 343-350 331-355 357-361 363-384 385-389 391-392 394-403 403 EEE LLC DEE DE DT DE DT DE DT DE DT DE DE DE DE DT DE DL DT DT DE DE DL DL DT DE DL DL DL DT DE ST SE SE SE TE | pss Zu . 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EXHBARICMT 45H Ade 6TSROTSRHSE CEA < Sy, 7305-8571 2 ld KEG 1-1-1 AREAFHRAFR GEMFSTER) PER BIER Tel: 0298-53-4302 (I:1#4) Fax: 0298-51-9764 E-mail: ogasawar @ arsia.geo.tsukuba.ac.jp Al I (TERRES) 7305-8571 >< ld TH KEG 1-1-1 TK FHKE Tel: 0298-53-4212 (3) or 53-4465 (HERS) Fax: 0298-51-9764 E-mail: isaomoto @ sakura.cc.tsukuba.ac.jp PPL PLD LOLOL OOD PANE TEROR .HÉBYÉ IEANHTZBAFEME HRK HARAS HWmARRMARKKAAH FAA HRA Ae AEAINEHBADBEMEE Sa-Y7LN-7RRERRAME (7 1 © LANA) HOT 8 z GG HO & ACL. 7113-8622 KEESCHAHHAS-16-9 2002 12 A 31 H a {T HAMAR He Y 4 - BK ISSN 1342-8144 Be a 03-5814 5 80: 1 À À M #4 — hk in MR & Paleontological Research tés fete oe RE MM: ee KE Al fll À Facets BH Bw 2,500F9 7176-0012 RRMA BKEE201301 BH 03-3991-3754 B6Æ, #45 - .-.— rn PPP r r 01 rer er rer rer PPO POP OPO PLP LPO ee nr er sr er ee ern ren M M ABORT IETS 24H, 2GBOSRVAK, EHZBMSOSENYTENTUEF. HEoEh Bld FÉOË0 tT. NNN 3 9088 01429 0209 | ISSN 1342-8144 Paleontological Research Vol. 6, No. 4 December 31, 2002 CONTENTS ARTICLES Fumio Kobayashi: Lithology and foraminiferal fauna of allochthonous limestones (Changhsingian) in the upper part of the Toyoma Formation in the South Kitakami Belt, Northeast Japan: +» Sai Yoshitaka Yabumoto: A new coelacanth from the Early Cretaceous of Brazil (Sarcopterygii, Actinistia) --- +--+. 222 etter ene nett eee eect teen nese ees 343 Shuji Niko: Echigoceras sasakii, a new Middle Carboniferous nautilid from the Omi Limestone Group, Central Japan - +++ +c tree etre nent teen ete e neces 351 Tatsuro Matsumoto: Turrilitid ammonoid Carthaginites from Hokkaido (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin—XCIV) ----:-----:--................................. 357 Takehisa Tsubamoto, Masanaru Takai, Naoko Egi, Nobuo Shigehara, Soe Thura Tun, Aye Ko Aung, Aung Naing Soe and Tin Thein: The Anthracotheriidae (Mammalia; Artiodactyla) from the Eocene Pondaung Formation (Myanmar) and comments on some other anthracotheres from the Eocene of Asia air N De on sci re ee 363 SHORT NOTES Shuji Niko and Masayuki Ehiro: Permian orthoconic cephalopods of the Ochiai Formation in the Southern Kitakami Mountains, Northeast Japan EEE ne = ieleleiele ee = em = tee lola (allele) (shiek diese: © cle else ei. scie 385 PROCEEDINGS = dr elle es see 0.6 VO es ale) Me aie =Uh=le ete He claiehe Welle ele delist she on wi 2,910 eee se ee ae je = ee oies «1e re) eUeuele 391 List of reviewerrs ne el ale helle ele chante = ele im ie! aia) a Malle (ole eee ce es.) eMails; opis! ie à eo ae e =. sn eee le se ele sie se sels ie ses ess © «ee 393 INDEX OF GENERA AND SPECIES seein oi dfelee elite teleiielelels eee cela ee lole arelalalle à o mean ae en) /a\/\a) ahi (1 1s] (el ee oo eee 394 IN TITI | 7) = z < z [e] 7) x = = o — — — —— —— DRE EE ans ande ats rei ree OF Fie we RD yay dee AF DA PA Nay oe 4 09 34 Toe Id byt ele oo paces Oe DCE CL wat Adal PTS PTIT TS wu. en ee rene: