: EHE A ERHEBEN ENGEN, ss
MOINE
HE a Alls bd i if 7 4; f in ‘aa 1 fiat # I BE e i een er) ie TE,
HI KE 4 4 ; H ñ A i ; - ACTE G PEST ers
Seats eet es 3; Re RARES
are
bie ur ; pri i oe NON =) | Bar LE
Fr rl jie - tal wd vr
1
Paleontological
Research
QE ISSN 1342-8144
Formerly Transactions and Proceedings of the Palaeontological Society of Japan
Vol. 3 No.1
April 1999
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), Satoru 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, ltaru Hayami, Hiromichi Hirano, Noriyuki Ikeya, Junji Itoigawa, Tomoki Kase, Hiroshi Kitazato, Itaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Hiroshi Noda, Ikuo 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 (Laison 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 (Editors of PR), Akira Tsukagoshi (Editor of “Fossils”), Naoki Kohno (Editor of Special Papers)
Auditor : Nobuhiro Kotake
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), 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
Paleontological Research, vol. 3, no. 1, pp. 1-17, 6 Figs., April 30, 1999
© by the Palaeontological Society of Japan
Permian bivalves from West Spitsbergen,
Svalbard Islands, Norway
KEWUI NAKAZAWA
28-2, Koyama Shimouchikawara-cho, Kita-ku, Kyoto 603-8132, Japan
Received 6 June 1998; Revised manuscript accepted 27 December 1998
Abstract. The bivalve fossils collected by Japanese-Norwegian research groups from the Kapp Starostin Formation in west Spitsbergen are described. They comprise fourteen species belonging to the Pterioida and two species of the Arcoida. Among them, six species, including two that are indeterminate, are newly described. They are Grammatodon (Cosmetodon) ? suzuki, G. (C.)? sp. ind., Streblochondria win- snesi, Vorkutopecten svalbardensis, Deltopecten sp. ind., and Palaeolima nakamurai. The fauna belongs to the Boreal bioprovince, but a single species, Cassianoides sexcostatus (Stuckenberg) has also been reported from the Central Rocky Mountains of the United States. The bivalve fauna suggests an Artinskian-Kungurian age for the Kapp Starostin Formation. This is somewhat earlier than the age deduced from brachiopods and bryozoans, but it is not decisive because the materials are poor. The Kapp Starostin Formation is conformably overlain by the Otoceras-bearing, earliest Triassic Vardebukta Formation, so a time-gap corresponding at least to the Dorashamian and Dzhulfian (= Tatarian) is inferred
between the two formations.
Key words: Kapp Starostin Formation, Permian bivalves, Spitsbergen
Introduction
The study materials were collected by Nakamura et al. in 1984 and 1990, and by Nakazawa et al. in 1986 from the Permian Kapp Starostin Formation of west Spitsbergen, in the Svalbard Islands, Norway. Brachiopods and bryozoans are most abundant among the macrofossils. Many species of brachiopods have been described by various authors, notably, Frebold (1937) and Gobbet (1963). Bivalves are found rather rarely and the descriptive studies are few. Toula (1873, 1875a, b) first described the following species, collected from “Carboniferous-Permian” strata on Sdérkapp Island off the southerntip of Spitsbergen, and Axel Island in Bellsund and on Hornsund, on the west coast of Spitsber- gen:
Pecten (Aviculopecten) bouei Verneuil, Pecten (Aviculopecten) kokscharofi Verneuil, Pecten (Aviculopecten) cf. ellipticus Phillips, Pecten (Aviculopecten) cf. dissimilis Fleming, Pecten (Aviculopecten) wilczeki Toula, Gervillia cf. antiqua Münster, Aviculopecten draschei Toula and Gervillia sp.
Frebold (1937) described the following species, mostly from the upper part of the Kapp Starostin Formation in the Festningen section, located on the southern coast of Spits- bergen at the entrance to Isfjorden and from Sorkapp Island :
Aviculopecten (Deltopecten) cf. mutabilis Licharew and A. (D.) cf. hiemalis Salter, Aviculopecten? sp. indet., Pecten
(Aequipecten) ? keyserlingiformis Licharew, Pecten (Aequi- pecten) keyserlingi Stuckenberg, Pecten (Pseudamusium) cf. ufaensis Tschernyschew, Pecten (Pseudamusium) ex aff. sericeus Verneuil, Parallelodon sp. ind, genus | =Paral- lelodon ?] et sp. ind., Clidophorus ? sp. ind., Pecten wilc- zeki Toula, and Leda sp. ind.
Among the species described by Toula, Aviculopecten bouei was referred to Aviculopecten (Deltopecten) mutabilis by Licharew (1927). Pecten cf. ellipticus was identified as Pecten (Pseudamusium) ex aff. sericeus Verneuil, and Pecten (Aviculopecten) cf. dissimilis was compared to Aviculopecten netschajewi Licharew and reported as Aviculopecten ? sp. ind. by Frebold (1937). Aviculopecten kokscharofi reported by Toula (1873) is probably identical with Aviculopecten cf. hiemalis illustrated by Licharew (1927, especially pl. 5, fig. 20), and is referred to Etheripecten cf. mutabilis Licharew in the present paper.
Among the species reported by Frebold, Aequipecten keyserlingi was considered to belong to the genus Mor- rispecten Muromtseva and Guskov by Muromtseva (1984, p. 75). Morrispecten is, however, a junior synonym of Undo- pecten Waterhouse, 1982 (Newell and Boyd, 1995). Pecten (Aequipecten) ? keyserlingiformis and Aviculopecten (Deltopecten) cf. mutabilis and A. (D.) cf. hiemalis of Frebold are referred to Etheripecten keyserlingiformis and E. ci. mutabilis ?, respectively. Pseudamusium cf. ufaensis and Parallelodon sp. ind. are identified as Streblochondria win- snesi sp. nov. and Grammatodon (Cosmetodon) ? suzuki sp.
i)
nov., respectively, in the present paper. Sixteen species including four new species and two indeterminable ones are described. All the materials are kept at the Department of Geology and Mineralogy, Faculty of Science, Kyoto Univer- sity.
Stratigraphy
The fossils were collected at four localities in west Spits- bergen, namely, the Festningen section along the southern coast of the entrance to Isfjorden, the Skansbukta section at Billfiorden, and the Reinodden and Ahlstrandodden sections along the southern coast near the entrance of Van Keulenf- jorden, in Bellsund (Figure 1). Faunas from the first and second localities were collected on Nakamura’s expedition in 1984 and in 1990. The stratigraphy of these sections was published by Nakamura et al. in 1990 and, in more detail, by the Japanese-Norwegian Research Group (1992). The other two localities were examined by Nakazawa's party in 1986 and the results were published by Nakazawa et al. (1990). All the materials are from the Permian Kapp Staros- tin Formation which was defined by Cutbill and Challinor (1965). The formation corresponds to the Brachiopod Cherts (including the Spirifer Limestone at the base) of previous authors (e.g., Gee et al., 1953). At the type locality, Festnin- gen, the formation is divided into three members, the Vo- ringen, Svenskeegga, and Hovtinden Members in ascending order (Cutbill and Challinor, 1965).
(1) Festningen section (Figure 2A)
At Festningen the Kapp Starostin Formation is 385 m in thickness and divided into twelve units (Nakamura et al. 1990 ; Japanese-Norwegian Research Group, 1992). Unit 1, about 20 m thick, is represented by brachiopod-rich, bioclas- tic limestone beds corresponding to the Voringen Member. Units 2 to 5, about 140 m thick, constitute the Svenskeegga Member, each represented mainly by siliceous shale, spicularite, spicularite and shale, and bioclastic limestone, respectively.
rt D Ay rms for \>2°___/ Longyearbyen
Bellsund \~_
En A
Hornsund ~ 2
Figure 1. Map of southern Spitsbergen showing fossil localities. a: Skansbukta, b: Festningen, c: Reinodden, d: Ahlstrandodden.
Keiji Nakazawa
The Hovtinden Member, about 225 m thick, consists of seven units, 6 to 12, each composed mainly of spicularite, alternation of spicularite and spicularitic shale, bioclastic limestone, spicularite, bioclastic limestone (partly silicified), alternation of siltstone and paper shales, and quartzose sandy shale or siltstone, respectively, in ascending order. Bivalve fossils have been obtained from Units 5, 7, 8,9 and ats (2) Reinodden section (Figure 2B)
At Reinodden the formation reaches more than 300 m in thickness. It is classified into eight units, A to H, in ascend- ing order (Nakazawa et al., 1990). Unit A, less than 5m thick, is the Voringen Member consisting of fossiliferous bioclastic limestone. Units B and C are referred to the Svenskeegga Member. Unit B, about 40 m thick, is sub- divided into three beds or subunits, 2 to 4. Beds 2 and 4 are represented by nodular or irregularly bedded, alternating spicularitic chert and thin mudstone. Bed3 consists of black laminated shale and siltstone. Unit C, about 80m thick, includes bedded black shale (Bed 5), and alternations of calcareous sandstone and limestone (Beds 6 and 7).
The Hovtinden Member (Units D to H), about 180 m thick, is characterized by coarse-grained sandstone and spicula- rite. It is subdivided into fourteen beds, Beds 8 to 21, as shown in Figure 2B. Glauconite is commonly found in the sandstones. Macrofossils have been collected from ten horizons (RP 1~10) in the Kapp Starostin Formation, among which RP 3, 7 and 9 contain bivalve fossils.
(3) Ahlstrandodden section (Figure 2C)
At Ahlstrandodden the formation is about 250 m thick. It is divided into eight units, 1 to 8 (Nakazawa et al., 1990). Unit1, 7.6m thick, consists of brachiopod-rich bioclastic wackestone of the Voringen Member. Units 2 and 3, which are 40 m and 58 m thick, respectively, are correlated to the Svenskeegga Member. Units4 to 8, about 140m thick altogether, correspond to the Hovtinden Member. They are composed mainly of spicularitic chert or spicularite, siliceous shale and a minor amount of limestone. Glauconite grains are commonly found in siliceous sandstones throughout the Hovtinden Member.
Among nine fossiliferous horizons (AP 1~9) within the formation, five horizons, AP 1,2,6,7 and 8, yield bivalve shells. The fossiliferous horizons AP 8 and 9 of the upper part of the Hovtinden Member can be correlated with hori- zons RP 9 and 10 in the Reinodden section. They are considered to correspond to horizon F 8 of the Festningen section.
Fossil occurrence and age assignment
Sixteen species in nine genera are identified from three sections mentioned above, plus one species, Acanthopecten licharewi (Fredericks), from Skansbukta (SA 7), as shown in Figures 3. The localities and stratigraphic horizons are shown in Figure 2.
Nakamura et al. (1987, 1992) distinguished five brachiopod assemblage zones in the Kapp Starostin Formation of the Isfiorden area. They compared these faunas to those of Russia, Arctic Canada, Greenland, and Alaska, all belonging
Permian bivalves from West Spitsbergen 3
A, FESTNINGEN
400 350 ERS B. REINODDEN 300 250 & = = = > fo) [e] | = = 200 E [o} mw
150
Starostin
Kapp
Svenskeegga Member
100
on [=]
Bi H FE —— MN
Her 10 6 RP fees
C, AHLSTRANDODDEN es
(OF She D ID OO DIAOlODEIENO
1 AP 1(9,10)
Figure 2. Geological columnar sections of the Kapp Starostin Formation at three localities showing horizons
of macrofossils.
a: chert or spicularite, b: shale or mudstone, b’: siliceous or spicularitic, c: sandstone, Cc’ :
siliceous, d: limestone, d’: siliceous, e: dolostone, e’ : dolostone nodule, f: calcareous, g: muddy. Numbers in parentheses correspond to those of bivalve species in Figure3. A: simplified from Japanese-Norwegian Research Group (1992, fig. 2), B and C: from Nakazawa et al. (1990, fig. 2).
to the Boreal bioprovince. From the correlation of these faunas, they concluded that the Kapp Starostin Formation ranges in age from Kungurian up to Midian or early Dzhulfian (Tatarian). Sakagami (1992) studied the bryozoans and pointed out the similarity of the fauna from the Voringen Member with the Kungurian fauna in the Timan-Pechora region. Faunas of the Svenskeegga and Hovtinden Mem- bers resemble Ufimian faunas of Arctic Canada and the Russian Far East, the Kazanian fauna of the southern Urals, and the Late Permian fauna of British Columbia. These comparisons are consistent with the age range inferred from the brachiopods, except that there is no positive evidence, from the bryozoans, of the presence of Dzhulfian strata. These observations support previous views on the age of the Kapp Starostin Formation, for example, Forbes et al. (1958) and Flood et al. (1971).
The ranges of the bivalve species are shown in Figure 3. Only two species, Vorkutopecten svalbardensis and V. aff. svalbardensis have been found in the Voringen Member. The overlying Svenskeegga Member is also poor in bivalves.
Five species have been collected there, namely, Ether- ipecten cf. mutabilis, Etheripecten wilczeki, Vorkutopecten svalbardensis, Acanthopecten licharewi, and Deltopecten sp. All infrequently occur and their ranges extend up into the Hovtinden Member. Accordingly, the fauna is not essen- tially different from that of the Hovtinden Member.
Eight and ten species could be identified from the lower and upper parts of the Hovtinden Member, respectively. In addition to species ranging up from the Svenskeegga Member, Streblopteria cf. eichwaldi, Streblopteria ? sp. and Palaeolima nakamurai appear from the lower part, but they have not been found from the upper part. The upper part is relatively rich in bivalve fossils. Grammatodon (Cos- metodon) ? suzukii, G. (C.) ? sp., Etheripecten keyserlingi- formis, E. aff. sichuanensis, E.? alatus, Streblochondria winsnesi and Cassianoides sexcostatus appear here.
The intimate relationship of the Spitsbergen fauna with that of the Russian Arctic region (Ural, Pechora, Russian Platform, Verkhoyansk) is shown by the occurrence of the following species :
ety
. Grammatodon (Cosmetodon)? sp. ind.
. Acanthopecten licharewt (Fredericks)
. Etheripecten cf. mutabilis (Licharew)
. Etheripecten wilezeki (Toula)
Vorkutopecten svalbardensts sp. nov.
2 3 4 5 6. a 8. 9% 0.
1
Rone
. Streblochondria winsnest sp. nov.
wo
. Deltopecten sp. ind.
PAs wn
. Streblopteria? sp. ind.
N a
. Palaeolima nakamurat sp. nov.
Figure 3. Compiled range-chart of bivalve fossils. Skansbukta.
Acanthopecten licharewi (Asselian-Artinskian of the Urals, Kungurian of Pechora, Lower Permian of Verkhoyansk), Etheripecten keyserlingiformis (Upper Carboniferous ?-Lower Permian of the Urals and Pechora), E. cf. mutabilis (Upper Carboniferous-Lower Permian of the Urals, Timan, Siberia), E.? alatus (Lower Permian of Pai Khoi in Siberia), Streblopteria cf. eichwaldi (Artinskian of the Urals and Russian Platform), and Cassianoides sexcostatus (Artinskian of the Urals and Russian Platform). Cassianoides sexcostatus is also report- ed from the Guadalupian of the United States (Branson, 1930 ; Ciriacks, 1963) and Etheripecten sichuanensis occurs in the Upper Permian of South China (Cheng et al., 1974).
The stratigraphic occurrences of these species suggest that the Kapp Starostin Formation ranges in age from Artinskian to Kungurian. This is somewhat earlier than the age range inferred from the brachiopods and bryozoans, but the materials are poor and the conclusion is not definitive.
The Kapp Starostin Formation is conformably overlain by the Lower Triassic Vardebukta Formation of the Sassendalen Group (Nakazawa et al., 1990 ; Nakamura et al., 1990). The earliest Triassic age of the basal part of this formation is indicated by the occurrence of Otoceras boreale Spath together with Claraia stachei (Bittner) (Kortshinskaya, 1986 ; Nakazawa et al., 1987). Hence, a time-gap corresponding at least to Dzhulfian-Dorashamian ages is indicated between the Permian and the Triassic beds.
. Cassianoides sexcostatus (Stuckenberg)
*: Festningen,
Keiji Nakazawa
Hovtinden Svenkeegga Member
Member
Vèringen
. Grammatodon (Cosmetodon)? suzukii sp. nov.
. Etheripecten keyserlingiformis (Licharew)
Ethertpecten aff. sichuanensis (Chen et al.)
Etheripecten? cf. alatus (Lyutkevich and Lobanova)
Vorkutopecten aff. svalbardensis sp. nov.
. Streblopterta cf. eichwaldi (Stuckenberg)
“: Reinodden, *: Ahlstrandodden, ~ :
Acknowledgments
| am very grateful to T.S. Winsnes, formerly of the Norsk Polarinstitutt, for his critical reading of the manuscript. V. Kotlyar (VSEGEI) and B.A. Muromtseva (VNIGRI) in Russia, T. Ishibashi of Kyushu University, and J. Tazawa of Niigata University, Japan gave me useful information and valuable references to the literature. K.Nakamura of Hokkaido University kindly made his collection available for study. H. Suzuki of Doshisha University, F. Kumon of Shinshu Univer- sity and E.H. Siggerud from Norway cooperated with me in the field. T.Setoguchi, F. Masuda, and T.lrino of Kyoto University made various facilities available for preparation of the manuscript. | wish to thank all these people very much.
Systematic description
Order Arcoida Stoliczka, 1871 Family Parallelodontidae Dall, 1890 Subfamily Grammatodontinae Branson, 1942 Genus Grammatodon Meek and Hayden, 1861 Subgenus Cosmetodon Branson, 1942
Grammatodon (Cosmetodon) ? suzukii sp. nov. Figures 4-1a, b Parallelodon sp. ind. Frebold, 1937, p. 55, pl. 1, figs. 8, 9.
Materials —A pair of left and right external molds.
Permian bivalves from West Spitsbergen
Holotype, Reg. no. HP 100050.
Etymology.—Dedicated to Dr. Hiroyuki Suzuki of Doshisha University, who worked in the field with the author.
Diagnosis.—Permian Grammatodon characterized by well developed, fine radial ribs and a little arcuate ventral margin.
Description.—Shell moderate in size, a little inflated, elon- gated subquadrate with subparallel dorsal and ventral mar- gins, rounded anterior and truncated posterior margins ; ventral margin slightly arcuate ; 41 mm long and 19 mm high ; umbo broad and low, raised above the hinge margin, situated at anterior one-fifth of shell length ; bluntly rounded umbonal ridge running from the umbo to the posteroventral extremity ; surface covered by numerous, weak radial striae, wider than the interstices, approximately fifteen per centimetre width on the medial surface of the shell, one centimetre from the umbo ; densely spaced concentric growth lines form cancel- late sculpture with the radials (Figure 4-1b) ; hinge and inter- nal characters not observable.
Comparison.—Two incomplete specimens illustrated by Frebold (1937) from near the same horizon at Festung (= Festningen) are identical with the present species. Based on Permian material from Malaysia, Yancey (1985) pointed out the possibility that most of the Paleozoic species de- scribed as Parallelodon should be referred to Grammatodon (Cosmetodon). Although the present species does not show its hinge characters, it is identified with that genus on the basis of its external shape and ornament. It is similar to the Guadalupian Cosmetodon multistriatus (Girty, 1908, p. 423, pl. 31, figs. 13, 14) in its shape and weak radial ornament, but it differs from that species in having less numerous radial striae, a little arcuate ventral margin and a larger size.
Occurrence.—Rare in black shale of the uppermost fossil horizon, in the Hovtinden Member (F11) at Festningen.
Grammatodon (Cosmetodon) ? sp. ind. Figures 4-2a, b
Genus (Parallelodon) ? et sp. ind. Frebold, 1937, p. 56, pl. 2, fig. 4.
Material—One incomplete, right external cast. Reg. no. HP 100051. Description.—Posterodorsal marginal part is missing.
Preserved part of the specimen is 30 mm long and 18.5 mm high. His twice as long as high judging from the growth line. Surface is covered by numerous, close-set radial striae and
Table 1.
Measurements of Acanthopecten licharewi (Fredericks).
in
growth lines which are very weak, but visible under the magnifying glass. The radials reach about forty per centimetre width on the medial part of the shell, one centimetre from the umbo (Figure 4-2b).
Discussion.—The present material most probably belongs to the species doubtfully referred to Parallelodon by Frebold (1937) from Festningen. It is similar to G. (C.)? suzuki in shape, but differs from it in more densely spaced and more irregular radial ornament. In its numerous radial striae it is similar to Grammatodon multistriatus (Girty), but it has a different shape with a more convex ventral margin than the latter species. Evidence is not adequate to support a new species for this specimen.
Occurrence.—Locality and horizon are identical with those for the preceding species.
Order Pterioida Newell, 1965 Superfamily Pectinacea Rafinesque, 1815 Family Aviculopectinidae Meek and Hayden, 1864 Subfamily Aviculopectininae Meek and Hayden, 1864 Genus Acanthopecten Girty, 1903
Acanthopecten licharewi (Fredericks, 1915) Figures 4-3—5
Pterinopecten Licharewi Fredericks, 1915, p. 28, pl. 1, fig. 14.
Aviculopecten (Acanthopecten ?) licharewi (Fredericks). Lichar- ew, 1927, p. 91, pl. 6, fig. 24.
Acanthopecten licharewi (Fredericks). Muromtseva, 1984, p. 66, pl. 25, fig. 26; pl. 28, figs. 7, 8, 11, 12.
Materials.—One nearly complete and one incomplete external cast of left valves, an incomplete external mold of a left ? valve, and an incomplete external mold of a right valve. Reg. nos. HP 100052~55.
Description.—All the specimens are incomplete internal molds or somewhat abraded external casts, and the details of the ornament are imperfectly preserved.
Shell small, subequivalve, subcircular in shape ; left valve a little inflated ; right valve nearly flat ; anterior auricle of left valve trigonal and sharply defined ; posterior auricle relative- ly large, flat, alate and protruding posterodorsally, but not sharply defined from the disc. Shape variable, probably due to secondary deformation; one left valve of nearly equal height and length, with an apical angle of 100° (Figure 4-3) and another left valve more elongate (L/H ratio of 1.34) with
Abbreviations and notation of Tables
1-8. L: length, H: height, U: distance of umbo from the anterior end of the shell, |: hinge length, r:
total number of radial ribs, r,, :
number of primary and secondary radials, respectively, ro_, : secondary to fourth-order radials between primary radials, r3., :
number of number of third- and fourth-order radials
between primary and secondary radials, c: number of comarginal lamellae or costae, a: apical angle (in
degrees), V: valve (R: right, L: left), *:
estimated value, linear dimensions in mm, Hor. : horizon.
Reg. no. L H H/L a r c V Hor. HP 100052 23.0 19.5* 0.85 100 13 11 L AP 6 HP 100055 20.5. — — 120 17 94 R AP 6 HP 100054 28.5 22, — — 14, 6. R AP 6 HP 100053 14. 14.8 = = 8, 7 L SA 7
Keiji Nakazawa
Permian bivalves from West Spitsbergen 7
a larger apical angle, 120°; radial ribs narrow and widely spaced varying in number from 13 to 17; interspaces between radials slightly concave or nearly flat; lamellose comarginal sculpture widely disposed, becoming wider later in growth stage with distally oriented spines in the middle of the interspaces of the radial ribs (Figure 4-5).
Discussion.—This species is similar to the Lower Permian Acanthopecten licharewi (Fredericks, 1915) from the Urals, Pechora and Verkhoyansk, and to the Upper Carboniferous Acanthopecten carbonarius (Stevens) reported from the United States (e.g., Newell, 1938), China (Chao, 1927), and the Donetz Basin (Jakowlew, 1903) in its small size and relatively small number of radial ribs. According to Muromtseva (1984), A. licharewi is distinguished from A. carbonarius in having less numerous radial ribs and completely flat interspaces between the radials. In these respects, the present material is identical with A. licharewi.
Occurrence.—Rare in calcareous shale or muddy siliceous limestone of Unit5 (lower part of Hovtinden Member) at Ahlstrandodden (AP 6), and in black shale of Unit 7 (upper part of Svenskeegga Member) at Skansbukta (SA 7). According to Thore S.Winsnes (personal communication, 1995) it also occurs in Permian strata in the valley north of Stensiöfjellet, inner Sassendalen.
Subfamily Etheripectininae Waterhouse, 1982 Genus Etheripecten Waterhouse, 1963
Discussion. —This genus was introduced by Waterhouse (1963) based on Etheripecten striatura Waterhouse from the Upper Permian of New Zealand. The ornament of the left valve resembles that of “Aviculopecten” with radial ribs increasing in number by insertion and differentiated into more than two orders. The radial ribs of the right valve of this species also increase in number by insertion, but are usually weaker and less differentiated than those of the left valve. In “Aviculopecten”, the number of radial ribs of the right valve increases by bifurcation or ramification. In this respect, Etheripecten is similar to Limipecten, but according to Waterhouse (1969) the concentric lamellae between radial ribs of Etheripecten point dorsally, while those of Limipecten point ventrally as in the case of Aviculopecten planoradiatus M'Coy, the type species. Recently, Newell and Boyd (1995) reexamined the Late Paleozoic pectinoids. They defined Aviculopecten and Aviculopectinidae as bivalves with equiconvex shells, provided with simple plicae in both valves. On the other hand, the family Etheripectinidae is character- ized by inequiconvex and paradiscordant shells, with multi-
costate ornament. Newell and Boyd stressed the variability of multiplicated ribbing and concentric sculpture in this family, treating the genera Aviculopecten and Deltopecten of authors, Etheripecten Waterhouse, Paradoxipecten Zhang, Corrugopecten Waterhouse, Fletcheripecten Waterhouse and Squamuliferipecten Waterhouse as synonyms of Heter- opecten Kegel and Costa. In this case, Heteropecten contains a vast number of species with various kinds of ornamentation. In this paper, Etheripecten is treated as a distinct genus from Heteropecten, the type species of which, Aviculopecten catharinae Reed, has broad and bifurcated radial ribs in the right valve. Fletcheripecten and Paradox- ipecten are here considered to be synonyms of Etheripecten.
Etheripecten keyserlingiformis (Licharew, 1927) Figures 4-6, 7a, b
Pecten (Aequipecten) ? keyserlingiformis Licharew, 1927, p. 33, pl. 3, figs. 1-3; Frebold, 1937, p. 52, pl. 7, fig. 7.
Aviculopecten keyserlingiformis (Licharew). Muromtseva, 1984, p. 60, pl. 28, fig. 10.
Materials.—One nearly complete, left semiexternal cast (HP 100056) and one incomplete, left internal mold (HP 100057).
Description.—Shell medium in size, pectiniform, a little inflated, prosocline, extended posteroventrally ; disc fan-like in shape with slightly arcuate anterodorsal, nearly straight posterodorsal, and rounded ventral margins ; anterior auricle trigonal with slightly convex anterior margin; posterior auri- cle a little larger than anterior one, sinuated posteriorly ; hinge margin straight, shorter than shelllength ; ligament area narrow, nearly smooth, provided with a trigonal alivin- cular ligament pit beneath the umbo (Figure 4-7b) ; umbo not prominent, slightly salient above the hinge margin, situ- ated at about anterior two-fifths of shell length; surface ornamented with nine or ten slender primary radial ribs alternating with secondaries, some of which become as strong as the primaries; two or three radial riblets of third and fourth order inserted in each interspace ; strong con- centric folds developed over the whole surface of the disc, more widely spaced in later growth stage ; three radial ribs observable on anterior auricle, and obsolete ones on poste- rior auricle.
Discussion.—These specimens are identical with Pecten (Aequipecten) keyserlingiformis reported by Licharew (1927) and Frebold (1937), in its characteristic ornamentation. Probably due to secondary deformation, one specimen (Fig-
Figure 4. 1a,b. Grammatodon (Cosmetodon) ? suzukii sp. nov., 1a: a pair of external molds of left and right valves, holotype (HP 100050), 1b: enlarged figure showing details of sculpture, x 2.5. 2a,b. Grammatodon (Cosmetodon) ? sp. 2a: right external cast (HP 100051), 2b: enlarged figure showing details of sculpture, x4. 3-5. Acanthopecten licharewi (Fredericks), 3,4: left semiexternal casts (HP 100052 and 53), «2 and 1.5, 5: right external mold (HP 100054), «1.5. 6, 7a, b. Etheripecten keyserlingiformis (Licharew), 6: left semiexternal cast (HP 100056), 7a: left semiexternal cast (HP 100057), 7b: enlarged figure showing alivincular ligament pit (arrow), «2.5. 8,9. Etheripecten wilczeki (Toula), 8: gypsum
cast of left external mold (HP 100058), «1.5, 9: left external mold (HP 100059), x 2. (Chen et al.), gypsum cast of left external mold (HP 100060). cast of left external mold (HP 100062), 12: left semiexternal cast (HP 100071).
indicated.
10. Etheripecten sp. aff. E. sichuanensis
11,12. Etheripecten sp. cf. E. mutabilis (Licharew), 11: gypsum
All are in natural size unless otherwise
8 Keiji Nakazawa
Table 2. Measurements of Etheripecten keyserlingiformis (Licharew).
Reg. no. E H H/L Nee Ia44 a G Hor. HP 100056 45.5 40.0 0.89 18 3 115 15 F11 HP 100057 = 17.6 — 15, 1~2 90 11 F11
ure 4-6) is extended posteroventrally and has a more elon- gated shape than the previously described species, but another (Figure 4-7a) has a shape and ornamentation similar to the type specimen. Although the right valve of this species has not been reported, the shape and ornamentation of its left valve are very similar to those of Etheripecten Striatura Waterhouse, the type species of the genus, so the species is here included in Etheripecten. Occurrence.—Rare in black shale of the uppermost fossil horizon of the Hovtinden Member at Festningen (F11).
Etheripecten wilczeki (Toula, 1875) Figures 4-8, 9
Pecten (Aviculopecten) Wilczeki Toula, 1875a, p. 152, pl. 1, fig. 12. Pecten wilczeki Toula. Frebold, 1937, p. 54.
Materials. —One nearly complete, left external mold and several fragmental molds of left valves. Reg. nos. HP 100058, 59.
Description.—Shell relatively small, pectiniform, a little inflated ; fan-like in shape, with nearly straight anterodorsal, slightly dorsally arcuate posterodorsal, and rounded ventral margins ; prosocline, extended posteroventrally; umbo not prominent, slightly salient above the hinge margin, lying at about anterior two-fifths of shell length; apical angle 95- 110° ; anterior auricle small, trigonal ; posterior auricle a little larger than the posterior one, alate with arcuate posterior margin ; both auricles sharply distinct from disc ; surface of the shell ornamented with nine primary radial ribs; wide, nearly flat interspaces are sculptured by 8-12 weak, radial threads, some a little stronger than the rest referred to as secondary ribs, but not alternating with the primaries ; um- bonal part of the shell, to 16 mm, ornamented with concentric wrinkles, which later fade away; two or three radial striae discernible on both auricles ; ligament unknown.
Comparison.—The type specimen described by Toula has seven strong, slender radial ribs, and smooth interspaces without finer radial ribs. Pecten (Aequipecten) ? wilczekifor- mis Licharew (1927, p. 35, pl. 3, figs. 4, 6, 7) is distinguished from E. wilczeki in its development of interstitial radial riblets.
According to Frebold (1937) the type specimen of E. wilczeki is not well preserved. He recognized the presence of finer radial ribs in the marginal area of his specimen, where the shell is preserved, and regarded the two species as being conspecific. However, the finer interstitial radial ribs of the specimen described here are very weak, numer- ous and subequal in strength, whereas those of P.(A.) ? wilczekiformis are differentiated into second, third or even fourth orders. Both species are considered to belong to Etheripecten. E. wilczekiformis is more closely allied to E. keyserlingiformis than to E. wilczeki. E. wilczeki is most similar to Euchondria cancellata Gu and Liu (1976, p. 171, pl. 12,
figs. 17, 18), from the Lower Permian Kufeng Series of South China, in shape and ornament. It differs only a little from the latter species in its lesser development of concentric folds and greater height relative to length. The genus Euchondria is characterized by a costate left valve, a nearly smooth right valve, and a series of ligament pits perpendicular to the hinge margin, in addition to a large, central ligament pit. In E. cancellata only left valves are known and the hinge character is unknown. Therefore, its generic position is uncertain.
Occurrence.—Rare in calcareous shale of the uppermost horizon of the Svenskeegga Member at Festningen (F5); rare in muddy limestone of the upper part of the Hovtinden Member at Ahlstrandodden (AP 7, 8) and Reinodden (RP 9).
Etheripecten sp. aff. E. sichuanensis Chen, Zhang and Xu, 1974
Figures 4-10
Resembles.— Etheripecten sichuanensis Chen, Zhang and Xu, 1974, p. 302, pl. 158, figs. 14,17 ; Fang, 1987, p. 373, pl. 2, figs. 1-6. ? Etheripecten sichuanensis Liu, 1976, p.179, pl. 13, figs. 10-13 ; Gan and Yin, 1978, p. 336, pl. 14, figs. 17, 20. Etheripecten hunanensis Zhang, 1981, p. 261, pl. 2, figs. 6-8.
Material.—One incomplete left external mold obtained by dissolving away shell material. Reg. no. HP 100060.
Description.—Shell relatively large, a little inflated, longer than high, estimated to be 65mm long and 58mm high; disc fan-like in shape with straight antero- and posterodor- sal margins and a broadly rounded ventral margin; hinge margin straight, a little shorter than shell length; anterior auricle small, subtrigonal, a little inlated, clearly separated from the disc by a sulcus; posterior auricle large, flat, sinuated posteriorly, protruding posterodorsally ; umbo sub- dued, slightly salient above hinge margin; apical angle 110° ; surface ornamented with radial ribs of three orders; pri- maries seven in number, strong and round-topped, alternat- ing with weaker secondaries ; five to six, thread-like rdial riblets of third order inserted in each interspace ; auricles with radial and concentric sculpture making a lattice orna- ment ; hinge not preserved.
Discussion.—The external shape and the ornamentation indicate a close relationship of this species with Etheripecten sichuanensis Chen, Zhang and Xu (1974) and E. hunanensis Zhang (1981), both from the Upper Permian Luntang Series in South China. The former species was later illustrated as ? E. sichuanensis sp. nov. by Liu (1976) based on the same specimens. Zhang distinguished E. hunanensis from E. si- chuanensis by the presence of striations and spinose pro- jections on the primary ribs. According to Fang (1987), however, these differences represent infraspecific variation.
Permian bivalves from West Spitsbergen 9
The specimen described here differs from sichuanensis in its more elongate shape with larger apical angle and larger size.
Occurrence.—Arenaceous limestone of the upper part of the Hovtinden Member at Festningen (F8).
Etheripecten sp. cf. E. mutabilis (Licharew, 1927) Figures 4-11,12; Figures 5-1—4
Pecten (Aequipecten) Kokscharofi Toula (non Verneuil), 1873, p. 20, pl. 5, fig. 6.
Aviculopecten cf. hiemalis Salter. figs. 18-21 ; pl. 6, fig. 1.
? Aviculopecten (Deltopecten) cf. mutabilis Licharew and A. cf. hiemalis Salter. Frebold, 1937, p. 51, pl. 1, figs. 2, 3.
Compared with.—
Pecten (Aequipecten) Bouei Toula, 1873, p. 19, pl. 5, fig. 8.
Aviculopecten mutabilis Licharew, 1927, p. 72, pl. 5, figs. 7-10, 12, 14-17.
Aviculopecten (Deltopecten) ? mutabilis Licharew. Lyutkevich and Lobanova, 1960, p. 102, pl. 15, figs. 1-6.
Licharew, 1927, p. 76, pl.5,
Material.—Eight incomplete left valves, one complete and two incomplete right valves. Reg. nos. HP 100061~68, 100070, 71.
Description.—Shell moderate in size, inequivalve, in- equilateral, prosocline, nearly as long as high, apical angle 90-100°. Left valve moderately inflated ; umbo not promi- nent, a little salient above the hinge margin ; beak situated at about anterior one-third of shell length ; disc fan-like in shape with slightly Concave anterodorsal, nearly straight posterodorsal, and well rounded ventral margins ; anterior auricle subtrigonal, with a rounded anterior margin, demar- cated from the disc by a sulcus ; posterior auricle only partly preserved ; surface covered with many radial ribs differ- entiated into three or four orders; primary ribs 7 to 9 in number, strong, round-topped, a little projected at ventral margin ; second- and third- order radials alternating regular- ly with lower-order radials ; some tertiary radials as strong as secondaries ; fourth-order radials very weak, sporadically inserted near the margin; growth lines close-set, curving ventrally on radial ribs and dorsally on interspaces, showing scaly or spinose projections on the primary ribs (Figures 5-1b, 2). Right valve nearly flat; anterior auricle deeply incised below ; posterior auricle subtrigonal, nearly equal in length to the anterior auricle, a little sinuated posteriorly ; numerous radial ribs increasing in number by insertion; first- and second-order radials becoming subequal in strength; a
Table 3. Measurements of Etheripecten sp. cf. E. mutabilis (Licharew).
radial ribs, #: total number of radial ribs.
small number of third-order radials, very weak and thread- like ; total number of radials, 34 ; close-set, weak concen- tric sculpture, making a lattice ornament with the radials ; alivincular ligament pit partly seen in one left internal mold.
Remarks and comparison.—In this material, the number of radial ribs increases by insertion in both the left and right valves. The comarginal sculpture curves ventrally on the radial ribs and dorsally on the interspaces. Therefore, these specimens are referred to Etheripecten Waterhosue (1969). In their well differentiated radial ornament and robust primary radial ribs, these shells are identical with Pecten (Ae- quipecten) kokscharofi as described by Toula (1873), Aviculopecten cf. hiemalis Licharew (1927), and probably Aviculopecten (Deltopecten) cf. mutabilis and A. (D.) cf. hiemalis Frebold (1937). They are very similar to Aviculopecten mutabilis Licharew (1927). According to Licharew (1927) the latter species is distinguished from Aviculopecten cf. hiemalis by its more pointed posterior auricle, the sharper restriction of auricles from the disc, the weaker bend of antero- and posterodorsal margins of the disc, and less regularity in the appearence of ribs. These differences, though, are not distinctive, as noted by Licharew himself. A. cf. hiemalis of Licharew has generally more robust primary radials than A. mutabilis. It is clearly distin- guished from the original A. hiemalis reported from the Himalayas (cf. Diener, 1897, p. 9, pl. 5, figs. 10a, b, 11) in taller shape and smaller posterior auricle and is more closely related to A. mutabilis. Lyutkevich and Lobanova (1960) illustrated the right valve of A. mutabilis (pl. 15, figs. 2, 5), which shows inserted radial ribs. Therefore, A. mutabilis is considered to belong to the genus Etheripecten. The right valve of Etheripecten mutabilis has less uniform radial orna- ment than the present species.
Occurrence.—Common in the Hovtinden Member at Fest- ningen, Reinodden, and Ahlstrandodden; rare in Svens- keegga Member at Reinodden.
Etheripecten ? sp. cf. E. alatus (Lyutkevich and Lobanova, 1960)
Figures 5-5
Compared with.— Pseudomonotis alata Lyutkevich and Lobanova, 1960, p. 116, pl. 17, fig. 9.
Description.—Only one incomplete, semiexternal cast of a
“x : Total number of primary and secondary
Reg. no. ik H H/L U U/L ia 1253 a V Hor. HP 100060 60. 58. = = = le 4~6 100 L F9 HP 100062 21.5 22.8 1.06 = = 7 3 85 L RP 3 HP 100063 22.3 21.5 0.96 8.0 0.36 26% 90 R F 11 HP 100064 30. ei). _ _ = 6, 3~4 — E F 9 HP 100065 83.5 35.0 1.04 12.5 0.37 9 3~5 90 E F 11 HP 100066 21.0 — = = = 244 85 R F 11 HP 100067 25.0 25.0 1.00 165 0.30 8 3~4 90 (Es F 11 HP 100071 25.3 257 1.02 10.5 0.42 th 3 90 L F 7p
10
Keiji Nakazawa
Permian bivalves from West Spitsbergen 11
left? valve is available (Reg. no. HP 100069). More than posterior one-third of the shell is not preserved. Shell 38 mm high and more than 30 mm long, nearly flat; disc in- ferred to be fan-like in shape ; anterodorsal margin straight ; anterior auricle trigonal, flat, clearly marked off from the disc ; surface ornamented with six strong, round-topped primary radial ribs ; broad, flat or slightly concave interspaces with weak secondary and tertiary radials five to eight in number ; close-set weak concentric striae partly preserved.
Discussion.—The present material is quite similar in shape and sculpture to Pseudomonotis alata, described on the basis of a right valve by Lyutkevich and Lobanova (1960) from the Lower Permian at Pai Khoi of the northern coast of Siberia. It differs slightly from that species in taller outline. The well differentiated, straight radial ornament of these Siberian and Spitsbergen species suggests that they belong to Etheri- pecten rather than to Pseudomonotis.
Occurrence.—Dark grey calcareous shale of Unit G of the Hovtinden Member at Reinodden (RP 9).
Family Streblochondriidae Newell, 1938 Genus Streblochondria Newell, 1938
Streblochondria winsnesi sp. nov. Figures 6-2a, b—4
Pecten (Pseudamusium) cf. ufaensis Tschernyschew. Frebold, 1937, p. 53, pl.1, fig. 3-5.
Material —One complete right valve (external and internal molds, holotype, Reg. no. HP 100094a, b) and a nearly complete right valve (internal and external molds, Reg. no. HP100095a, b). Holotype specimen occurs in black shale of Unit 11 of the Hovtinden Member at Festningen.
Etymology.—Dedicated to Thore S. Winsnes for his contri- bution to the geological understanding of West Spitsbergen.
Diagnosis.—Permian Streblochondria characterized by a broad shape and very fine cancellate ornament composed of numerous radial and concentric striae.
Description.—Shell medium in size, a little inflated, and subcircular in shape, with well rounded ventral, slightly convex posterodorsal, and slightly concave anterodorsal margins; as long as high; opisthocline ; umbo subdued, not salient above the hinge margin; apical angle varying from 90° to 110° ; posterior auricle very small, obtuse-triangu- lar, truncated posteriorly; anterior auricle relatively large, rounded trigonal, and marked below by deep slit-like byssal notch ; surface covered with numerous, uniform radial striae increasing in number by insertion, 70 per cm in the medial area 1cm away from the umbo; dense concentric fila
Table 4. Measurements of Streblochondria winsnesi sp. nov.
Reg. no. EE H H/L | a Hor. HP 100094 33.5 ca33 099 95 90-110 F11 HP 100095 20.0 20.0 1.00 = 90-110 APQ
making a cancellate ornament with the radials, slightly raised scales on the radials ; anterior auricle ornamented with five distinct radial ribs and growth lines; hinge characters un- known.
Discussion.—Frebold (1937) illustrated three right valves identified as Pecten (Pseudamusium) cf. ufaensis Tscherny- schew from the upper part of the Kapp Starostin Formation at Festningen. One of them shows a distinct sculpture, very similar to that described here, so it is considered to be conspecific with this species. It is similar to Streblochondria sculptilis (Muller), the type of the genus, from the Carbonifer- ous of the United States (cf. Newell, 1938, p. 38, pl. 16, figs. 5a-c, 7, 9a, b). However, the present new species has a larger apical angle, a lower outline, and finer ornament than that species. It is more closely allied to S. ufaensis (Tscher- nyschew) (Licharew, 1927, p. 30, pl. 2, figs. 7,8; Lyutkevich and Lobanova, 1960, p. 131, pl. 21, fig. 1), but differs from that species in the finer radial sculpture as noticed by Frebold and, furthermore, in its longer outline.
Occurrence.—Rare in siliceous limestone of the upper part of the Hovtinden Member at Ahlstrandodden (AP 9), and the uppermost horizon of the Hovtinden Member at Festningen (F11).
Genus Streblopteria M'Coy, 1851
Streblopteria sp. cf. S. eichwaldi (Stuckenberg, 1898)
Figures 6-6, 7a, b, c
Pecten (Aviculopecten) cf. ellipticus Toula, 1873, p. 20, pl. 5, fig. 1. Pecten (Pseudamusium) sp. ind. ex aff. sericeus Frebold, 1937, p. 54. Compared with.— Pecten Eichwaldianus Stuckenberg, 1898, p. 208, pl. 1, figs. 25a, b.
Materials.—A pair of valves, two internal molds, and two incomplete external molds. Reg. nos. HP 100087~90.
Description.—Shell small, nearly equivalve, subcircular in shape, opisthocline, a little extended anteriorly ; left valve gently inflated; right valve slightly less convex than left; anterodorsal margin of the disc a little concave, ventral and posterior margins well rounded ; umbo lying a little posterior to the middle of the shell, not salient above the hinge
Figure 5. 1-4. Etheripecten sp. cf. E. mutabilis (Licharew), 1a: gypsum cast of left external mold (HP 100061), 1b: enlarged figure showing details of sculpture, «3, 2: gypsum cast of left external mold (HP 100064), 3: silicon rubber cast
of right external mold (HP 100066), 4: gypsum cast of right external mold (HP 100063). (Lyutkevich and Lobanova), left? semiexternal cast (HP 100069).
5. Etheripecten ? sp. cf. E. alatus 6-10. Vorkutopecten svalbardensis sp. nov., 6: gypsum
cast of right external mold, holotype (HP 100072), 7 : semiinternal mold of left valve, paratype (HP 100076), 8: gypsum cast of right external mold (HP 100075) «1.2,9: gypsum cast of right external mold (HP 100077), 10: gypsum cast of right external
mold (HP 100078), x 1.4. cast of external mold of right valve (HP 100086).
11,12. Deltopecten sp., 11: semiexternal cast of left valve (HP 100085), 1.1. All are natural size unless otherwise indicated.
12: silicon rubber
Keiji Nakazawa
12
Permian bivalves from West Spitsbergen 13
margin ; apical angle 90° in umbonal portion and 110-120" in later growth stages ; posterior auricle small, obtuse-triangu- lar; anterior auricle larger, obtuse-triangular in left valve, and deeply incised below in the right valve ; surface almost smooth, weak concentric sculpture discernible in the internal mold and partly preserved external cast ; no radial ornament observed.
Discussion and comparison.—The genus Streblopteria was established by McCoy (1851). The Carboniferous Meleagrina laevigata McCoy from Ireland was designated as type species by Meek and Worthen (1866). The genus is char- acterized by smooth shells of acline to opisthocline pectinoid form, and is distinguished from Streblochondria Newell (1938) which has cancellate sculptures. The posterior auricle of the type species is much larger than the anterior auricle, poorly distinguished from the disc. However, the forms with a small, obtuse-triangular, more or less clearly defined posterior auricle are also included in Streblopteria or referred to Pseudamusium Verrill by many authors.
According to Cox et al. (1969) Pseudamusium is a junior synonym of the Cenozoic genus, Palliolum Monterosato. Several small Pseudamusium species, such as P. eichwaldi (Stuckenberg), P. pusillus (Schlotheim), and P. ellipticum (Phil- lips), have very weak radial ribs or cancellate ornament on a limited part of the shell. They were doubtfully assigned to Streblochondria by Newell (1938). However, they have a longer shape than Streblochondria and are more similar to smooth forms of Streblopteria or “Pseudamusium”. This hardly warrants recognition as a different genus. In this paper, all these species are treated as Streblopteria, although they differ somewhat from the type species. The species described here is most similar to S. eichwaldi (Stuckenberg, 1898) in shape, but the surface ornament is insufficiently known for specific identification. Pecten cf. ellipticus reported by Toula (1873) from the south point of Spitsbergen was referred to Pecten (Pseudamusium) aff. sericeus Verneuil by Frebold (1937). However, P. sericeus has a more opisthocline shell that is extended more anterior- ly. It is probably identical with the present species.
Occurrence.—Siliceous limestone of the lower part of the Hovtinden Member at Ahlstrandodden (AP 6).
Streblopteria ? sp. ind. Figures 6-8
Discussion.—One incomplete right internal mold (Reg. no. HP 100092), estimated at 24 mm long and a little more than 24 mm high, is at hand. The shell is subcircular in outline and provided with a concave anterodorsal margin. The surface is covered by a weak concentric sculpture. The auricular part of the shell is not preserved. It probably belongs to Streblopteria, but is too imperfectly preserved to be certain.
Occurrence.—Siliceous shale of the lower part of the Hovtinden Member at Ahlstrandodden (AP 6).
Family Deltopectinidae Dickins, 1957 Genus Vorkutopecten Guskov, 1984
Vorkutopecten svalbardensis sp. nov. Figures 5-6—10
Material.—Eight right external and internal molds and three left external and internal molds. Reg. nos. HP 10007283 (holotype HP 100072). Holotype from Unit 9 of the Hovtin- den Member at Festningen.
Etymology.—Derived from Svalbard Islands, where the species occurs.
Diagnosis.—Shell is higher than long ; ornamentation of both left and right valves consists of numerous radial ribs differentiated into three orders, increasing in number by insertion. Concentric costae arch ventrally in the inter- spaces of radial ribs.
Description.—Shell inequivalve, inequilateral, suborbicular in shape, a little higher than long ; right valve moderately to weakly inflated ; left valve more inflated than right; umbo situated a little anterior to the middle of shell, nearly acline and slightly salient above the hinge margin in the left valve, but not in the right valve; apical angle about 90°; anterior and posterior auricles nearly equal in length; posterior one trigonal and sinuated posteriorly ; right anterior auricle deep- ly incised below; surface of disc covered with numerous, slender radial ribs narrower than interstices, increasing in
Table 5. Measurements of Streblopteria sp. cf. S. eichwaldi (Stuckenberg).
Reg. no. [E H H/L | YL U U/L a V Hor. HP 100087a 8.0 TS 0.94 4.0 0.50 4.0 0.50 ~110 L AP 6 HP 100087b 8.0 78 0.98 ST 0.46 4.5 0.56 90-120 R AP 6 HP 100088 12.7 11.6 0.91 5 0.45 7.2 0.56 90-120 R AP 6 HP 100089 13.0* 12.5 0.96 = — 7.5 0.57 ~120 R AP 6 Figure 6. 1. Vorkutopecten sp. aff. V. svalbardensis sp. nov., gypsum cast of right external mold (HP100084). 2-4.
Streblochondria winsnesi sp. nov., 2a: right external mold, holotype (HP 100094), «1.4, 2b: gypsum cast, 3: right internal
mold of the same, 4: right external mold (HP 100095).
5. Cassianoides sexcostatus (Stuckenberg), left external mold (HP 100093), X 2.4. 6, 7a-c. Streblopteria sp. cf. S. eichwaldi (Stuckenberg), 6 :
right internal mold (HP 100088), «1.5, 7a: a pair
of internal molds of left (L) and right (R) valves (HP 100087), «2, 7b-c: enlarged figures of right (b) and left (c) valves, <3.
8. Streblopteria ? sp., right external cast (HP 100092).
9,10. Palaeolima nakamurai sp. nov., 9: right external cast, paratype
(HP 100097), “1.5, 10: right external cast (R), holotype (HP 100096) and a part of left valve (L), x1.2. All are natural size
unless otherwise indicated.
14 Keiji Nakazawa
number by insertion; primary radial ribs varying in number from 12 to 17, with two or three radials of second and third orders in each interspace between the primaries ; total number of radials 35 to 50 or more; secondary radials of right valve become as strong as primaries ; lamellose con- centric sculpture developed on the whole surface, curving dorsally on radial ribs and ventrally in interstices; both auricles sculptured by radial ribs and concentric costae; a small, trigonal ligament pit partly preserved in one left internal mold.
Remarks and comparison.—The radial ribs of both left and right valves increase in number by insertion, as in Etheri- pecten, Limipecten, and Vorkutopecten. The concentric sculpture swings ventrally between radial ribs as in Limipecten, not Etheripecten. The shell length of Limipecten is usually equal to or larger than the height, and the radial ribs of the right valve are finer and more numerous than those of the left valve. Furthermore, the right valve is nearly flat. The present species has a greater height than length. The ornamentaion is similar in both valves, although secondary ribs of the right valve grow as strong as the primaries. The right valve is more or less inflated. In these respects, it can be identified with Vorkutopecten established by Guskov (in Muromtseva, 1984), based on Aviculopecten giganteus talis Lyutkevich and Lobanova (1960, p. 108, pl. 16, fig. 10; pl.17, fig. 1). Guskov included two species in the genus in addition to the type species, namely, Aviculopecten subclathratus (Keyserling) and A. netschajewi Licharew. However, the type specimen of the latter species has bran- ching radial ribs in the right valve and is excluded from Vorkutopecten. On the other hand, materials described as Vorkutopecten netschajewi by Guskov (Muromutseva, 1984, pl. 29, fig. 8) have inserted radial ribs and cannot be identified with this species, which is more similar to A. subclathratus. The Spitsbergen species is similar to A. subclathratus and A. netschajewi of Guskov, but differs in its more numerous primary radial ribs and larger posterior auricle. Vor- kutopecten, characterized by broad, alivincular ligament pit and a grooved ligament area, is included in Family Deltopectinidae. The present species has a relatively small ligament pit.
Occurrence.—Common in siliceous limestones of the Hovtinden Member at Festningen (F 7p, F 8 and 9), rare in limestone of the Voringen Member (AP 1), common in siliceous limestone of the Svenskeegga (AP 2) and the Hovtinden Member (AP 6, 7) at Ahlstrandodden, rare in cal- careous sandstone of the Hovtinden Member at Reinodden
(RP 7).
Vorkutopecten sp. aff. V. svalbardensis sp. nov. Figures 6-1
Discussion.—The species is represented by a single, large external mold of a right vaive (Reg. no. HP 100084). It is 86 mm long and 91mm high and has an apical angle of 100°. The shell is gently convex and sculptured with as many as 60 radial ribs. The radials are differentiated into three orders, but due to poor preservation distinction between primary and secondary ribs is difficult. This species is very similar to the preceding new species in shape and ornamen- tation, but its size is much larger and its apical angle is a little greater.
Occurrence.—Arenaceous limestone of Unit1 (Vgringen Member) at Ahlstrandodden (AP 1).
Genus Deltopecten Etheridge, Jr., 1892
Deltopecten sp. ind. Figures 5-11, 12
Material. —One incomplete left semiexternal cast, and one incomplete right valve represented by external and internal molds. Reg. nos. HP 100085, 86.
Description.—Shell moderate in size, subcircular in shape, nearly equiconvex and subequilateral ; umbo not prominent, located subcentrally ; apical angle 100-110" ; anterior auricle triangular, with slightly concave anterior margin in the left valve and byssate in the right valve ; left posterior auricle not preserved ; right posterior one partly preserved, obtuse-tri- angular and probably smaller than the anterior one ; surface of the left valve sculptured by relatively slender, rounded primary ribs, 18 in number, separated by wide interspaces and alternating with very weak, secondary radials; right valve ornamented with flat-topped primary radial ribs ; inter- vening flat interspaces of a width nearly equal to that of the radial ribs, with weak secondary radials inserted in the medial part of the shell; surface of both valves covered with close- set concentric fila swinging slightly ventrally, in the inter- spaces ; ligament not preserved.
Discussion.—Although the ligament cannot be observed, the present species can be referred to Deltopecten judging from the nearly equiconvex shell and relatively simple, flat- topped radial ribs. This species is somewhat similar to
Table 6. Measurements of Vorkutopecten svalbardensis sp. nov.
Reg. no. ie H H/L | U/L a r r Vv Hor. HP 100072 SILOF 30.5* 0.98 19. 0.48 88 16 54 R F9 HP 100074 29.0 31.5 1.09 20.0 0.38 90 11? 47 R F 7p HP 100075 35.0 38.0 1.09 35.0 0.46 88 17 46. R F9 HP 100076 24.0* 27.0 113 — 0.46 85 14 30. L AP 1 HP 100077 20.0 22.0 1.10 — 0.50 90 12 42 R F 7p HP 100078 27.0* 28.7 1.06 22.0 0.50 90 12 40 L AP 1 HP 100080 34.3 35.8 1.04 26.0 0.43 90 12 37 R AP 2 HP 100081 26.0* 30.3 dar 13.0 0.49 90 ? 35 R AP 7
Permian bivalves from West Spitsbergen 15
Table 7. Measurements of Deltopecten sp. ind.
Reg. no. L H H/L U/L a ri V Hor. HP 100085 35:5 33:5 0.94 16.7 0.47 105 18 [E RP 7 HP 100086 30+ 35.0 — 1725 0.50 110 15? R AP2
Deltopecten Iyonsensis Dickins (1957, p. 41, pl. 7, figs. 1-5 and 9; pl. 8, figs. 11-13; pl.9, fig. 12 ; pl. 10, figs. 3-4) from West Australia, but differs from that species in its less numerous primary radial ribs and the development of secondary radials in the left valve.
Occurrence.—Rare in calcareous sandstone of Unit E of the Hovtinden Member at Reinodden (RP 7) and in siliceous limestone of Unit 3 of the Svenskeegga Member at Ahlstran- dodden (AP 2).
Family Cassianoididae Newell and Boyd, 1995 Genus Cassianoides Newell and Boyd, 1995
Discussion.—The present family and genus were estab- lished by Newell and Boyd (1995) on the basis of a single species, Cassianoides kingorum Newell and Boyd of the Middle to Late Permian of West Texas. The genus is characterized by small, strongly inequivalve shells ; the left valve is strongly convex, ornamented with a few widely spaced, strong primary costae and a few comarginal, tubular hyote spines on the radial ribs ; the right valve is flat, sculp- tured by spineless, subdued radial ribs. Cyrtorostra sex- radiata Branson (1930, p. 45, pl. 11, figs. 13-15) from the Upper Permian Park City Formation was later shifted to the genus Cassianella of the Family Cassianellidae by Ciriacks (1963). This species was considered to be a junior synonym of Pseudomonotis sexcostatus Stuckenberg (1898, p. 207, pl. 1, fig. 40) from the Permian of Russia and to belong to Aviculopecten by Muromtseva (1984). The species is very similar to Cassianoides kingorum, not only in shell form but also in the characteristic ornamentation of both the left and right valves. It undoubtedly belongs to Cassianoides.
Aviculopecten crassispinosus Chronic, reported by Newell et al. (1953, p. 155, pl. 33, figs. 10-13) from the Lower Permian of Peru, is also referred to as a member of this genus. Cassianella rara described by Waterhouse (1987, p. 145, pl 3, figs. 1, 7,10) from the Middle Permian of East Australia is another example. Waterhouse noticed the close relation of this species to C. sexradiata and C. crassispinosus. His figs. 1 and 7, illustrated as a right valve, are quite similar to the left valve of A. crassispinosus (especially fig. 13a of Newell et al., 1953), and are believed to be a left valve. The genus Crassinoides is now known from the Permian of the United States, Peru, Australia, Russia, and Spitsbergen.
Cassianoides sexcostatus (Stuckenberg, 1898) Figure 6-5
Pseudomonotis sexcostatus Stuckenberg, 1898, p. 207, pl. 1, fig. 40.
Cyrtorostra sexradiata Branson, 1930, p. 45, pl. 2, figs. 13-15.
Cassianella sexradiata (Branson). Ciriacks, 1963, p. 45, pl. 5, figs. 5-7.
Aviculopecten sexcostatus (Stuckenberg). 61, pl. 27, fig. 6; pl. 33, figs. 10-13.
Muromtseva, 1984, p.
Material.—Only one external mold of a left valve. HP 100093.
Description.—Shell small, 14mm long and 14mm high, strongly inflated ; umbo narrow, orthogyrate, salient above the hinge margin and curving down over the hinge ; anterior auricle rounded-trigonal, a little inflated and marked off from the disc by a deep and wide sulcus ; posterior auricle imper- fectly preserved, relatively small, obtuse-triangular, with its posterior margin weakly sinuated and set off from the disc by a strong, posterior, radial marginal rib ; surface ornamented with nine slender but sharply raised radial ribs, projecting ventrally at ventral margin; interspaces between radials wide, slightly concave; distinct, regular concentric fila, closely spaced, curving dorsally in the interspaces, and with comarginal spinose projections on the radials ; hinge margin straight, shorter than shell length; hinge not preserved.
Remarks.—The present specimen differs from the type in its more numerous radial ribs, but this is considered to be due to infraspecific variation. Crassianoides sexcostatus can be distinguished from C. crassispinosus (Chronic) by its weaker radial ribs and less spinose concentric sculpture, and from C. rara (Waterhouse) by the absence of secondary radial riblets.
Occurrence.—Black siliceous shale of the uppermost fossil horizon of the Hovtinden Member at Festningen (F1).
Reg. no.
Superfamily Limacea Rafinesque, 1815 Family Limidae Rafinesque, 1815 Genus Palaeolima Hind, 1903
Palaeolima nakamurai sp. nov. Figures 6-9, 10
Materials.—External casts and molds of a complete right valve and an incomplete left valve, and a nearly complete external cast of a right valve. Reg. nos. HP 100096 (holotype) and 100097. Holotype specimen occurs in shale of Unit 7 of the Hovtinden Member at Festningen.
Diagnosis.—Broadly rounded Palaeolima ornamented with wide, rounded, branching radial ribs intercalated with narrow furrows.
Etymology.—Dedicated to Dr. K. Nakamura, who surveyed West Spitsbergen several times as a leader of the Japanese Expedition.
Description.—Shell equivalve, inequilateral, a little inflated, broad and oblique-oval in shape, opisthocline, extended anteroventrally ; umbo not prominent, a little salient above the hinge margin; apical angle about 110°; umbonal angle about 80°, no umbonal ridge ; umbo situated near the middle of the straight hinge margin; height slightly less than the length; both auricles obtuse-triangular, anterior one
Table 8. Measurements of Palaeolima nakamurai sp. nov.
longest axis of the shell)
Keiji Nakazawa
A: umbonal angle (angle between hinge line and
Reg. no. [a H H/L U U/L a A r th V Hor. HP 100096 31.0 29.7 0.96 18.8 1.65 80 110 33 15 R F 7-1 HP 100097 24, 24.5 80 110 30 16 R AP 6
depressed, obscurely defined from the main body ; posterior one marked off anteriorly by a steep umbonal slope ; surface ornamented with 15-16 broadly rounded, primary radial ribs wider than interstitials, increasing in number by bifurcation, reaching 30 or more in total; growth lines weak; anterior auricle nearly smooth; posterior one sculptured by weak radial costae ; hinge not preserved.
Comparison.—The species is similar in ornament to Palaeolima simplex Hind (1908, p. 39, pl. 39, figs. 24-27) from the Carboniferous of England, P. petaline Zhang (1981, p. 213, pl. 11, figs. 17) and P. fasciculicostata Liu (1976, p. 236, pl. 17, figs. 22, 24, 25), both from the lower Upper Permian of South China. It is distinguished from them by its larger size and more circular outline. Palaeolima krotowi (Stuckenberg, 1898, p. 336, pl.1, fig. 29) from the Upper Carboniferous of Russia has radial ribs narrower than its interstitial furrows and is easily distinguished from the present species. Specimens referred to P. krotowi by Licharew (1927, p. 37, pl. 3, figs. 8-12, 14) and Muromtseva (1984, p. 79, pl. 33, fig. 11), from the Lower Permian of the Urals and Pechora, have broader radials than interstices, so the specific identification is doubtful. These shells are more similar to the present new species than to P. krotowi, but they differ from it being more anteroventrally extended and more oblique in shape.
Occurrence.—Rare in black shale of the lower part of the Hovtinden Member at Festningen (F 7-1) and at Ahlstrandod- den (AP 6).
References
Branson, C.C., 1930: Paleontology and stratigraphy of the Phosphoria formation. Missouri University Studies, vol. 5, p.1-99.
Chao, Y., 1927: Fauna of the Taiyuan Formation of North China-Pelecypoda. Palaeontologia Sinica, ser. B, vol. 9, fasc. 3, p. 1-64. (in Chinese)
Chen, C.C., Zhang, ZM, and Xu, J.T., 1974: Permian Bivalvia. /n, Nanjing Institute of Geology and Palaeontology ed., A Handbook of Stratigraphy and Palaeontology in Southwest China, p. 302-303. (in Chinese)
Ciriacks, K.W., 1963: Permian and Eotriassic bivalves of the Middle Rockies. Bulletin American Museum of Natural History, vol. 125, 100 p., 16 pls.
Cox, L.R., 1969: Palliolum (Palliolum). In, Moor, R.C. ed., Treatise on Invertebrate Paleontology, Part N, vol. 1, Mollusca 6. Bivalvia, N354, The University of Kansas Press and the Geological Society of America.
Cutbill, J.L. and Challinor, A., 1965: Revision of the strati- graphical scheme for the Carboniferous and Permian rocks of Spitsbergen and Bjorngya. Geological Maga- zine, vol. 102, p. 418-435.
Dickins, J.M., 1957: Lower Permian pelecypods and gas-
tropods from the Carnavon Basin, Western Australia. Bureau of Mineral Resources, Geology and Geophysics, Commonwealth of Australia, Bulletin, vol. 41, 55 p., 10 pls.
Diener, C., 1897: The Permian fossils of the Productus Shales of Kumaon and Gurhwal. Memoir Geological Survey of India, Ser. XV Himalayan Fossils, vol. 1, pt. 4, 54 p., 5 pls.
Fang, Z.Z., 1987: Bivalves from the upper part of the Per- mian in Southern Hunan, China. Collection of Post- graduate Theses, Nanjing Institute of Geology and Palaeontology, Academia Sinica, no. 1, p. 349-411, pls. 1- 8. (in Chinese with English abstract)
Flood, B., Naggy, J. and Winsnes, T.S., 1971: Geological Map Svalbard 1: 500,000, sheet 1G, Spitsbergen South- ern Part. Norsk Polarinstitutt Skrifter, Nr. 154A.
Forbes, C.L., Harland, W.B. and Hughes, N.F., 1958: Palaeontological evidences for the age of the Carbonif- erous and Permian rocks of Central Vestspitsbergen. Geological Magazine, vol. 95, p. 465-489.
Frebold, H., 1937 : Das Festungsprofil auf Spitsbergen. IV Die Brachiopoden- und Lamellibranchiaten und die Strati- graphie des Oberkarbons und Unterperms. Skrifter Svalbard og Ishavet, vol. 69, p. 1-94, pls. 1-11.
Fredericks, G., 1915: Fauna verkhnepaleozoyskoy tolstshi okrestnosty g. Krasnoufimska Permskoy gubernii (Upper Paleozoic fauna of the environment of Krasnoufimsk). Mémoires du Comité Géologique, n. ser. vol.109, 117 p., 10 pls. (in Russian with French abstract)
Gan, X. and Yin, H., 1978: Lamellibranchiata. In, Working Team on Stratigraphy and Palaeontology of Guizhou Province ed., Palaeontological atlas of Southwest China, volume of Guizhou Province, pt. 2, p. 337-396, pls. 109- 126. (in Chinese)
Gee, E.R., Harland, W.B. and McWhale, J.R.H., 1953: Geol- ogy of Central Vestspitsbergen, Part Il. Carboniferous to Lower Permian of Billefjorden. Transactions Royal Society of Edinburgh, vol. 62, p. 299-356.
Girty, G.H., 1903 : The Carboniferous formations and faunas of Colorado. United States Geological Survey, Profes- sional Paper, vol. 16, 546 p.
Girty, G.H., 1908: The Guadalupian fauna. United States Geological Survey, Professional Paper, vol. 58, 626 p., 31 pls.
Gobbet, D.J., 1963 : Carboniferous and Permian brachiopods of Svalbard. Norsk Polarinstitutt Skrifter, vol.127, 201 p., 25 pls.
Gu, Z.W. and Liu, L., 1976: Euchondria cancellata, sp. nov. In, Nanjing Institute of Geology and Palaeontology, Academia Sinica ed., Monograph of bivalve fossils of China, p.171. Science Press. (in Chinese)
Guskov, B.A., 1984: Genus Vorkutopecten. In, Murom- tseva, V.A. ed., Permian marine deposits and bivalve molluscs of the Soviet Arctic, p.65. Ministry of Geol-
Permian bivalves from West Spitsbergen
ogy, USSR, Lenigrad, (Nedra). (in Russian)
Hind, W., 1901-1905 : Monograph of the British Carbonifer- ous Lamellibranchiata, vol.2, 222p., 25 pls. Palaeontological Society of London.
Jakowlew, N., 1903: Die Fauna der oberen Abteilung der paleozoischen Ablagerungen im Donetz-Bassin. |. Die Lamellibranchiata. Mémoires du Comité Geologique, n. ser. vol. 4, 44 p., 2 pls.
Japanese-Norwegian Research Group, 1992: Investigation on the Upper Carboniferous-Upper Permian succession of West Spitsbergen, 1981-1991, 134 p. Hokkaido Uni- versity.
Kortshinskaya, M.V., 1986: Biostratigraphy of Induan Stage of Spitsbergen. In, Krasilstshikov, A.A. and Mirzaev, M. N. eds., Geology of sedimentary cover of Spitsbergen Archipelago, p. 77-93, pls.1-7. Ministry of Geology, USSR, Leningrad. (in Russian)
Licharew, B.K., 1927: Upper Carboniferous Pelecypoda of Ural and Timan. Mémoires du Comité Geologique, n. ser., vol.164, 137 p., 4pls. (in Russian with English abstract)
Liu, L., 1976: Etheripecten sichuanensis, sp. nov. In, Nan- jing Institue of Geology and Palaeontology, Academia Sinica eds., Monograph of bivalve fossils of China, p. 179. Science Press. (in Chinese)
Lyutkevich, E.M. and Lobanova, O.V., 1960: Permian pelecypods from the Soviet sector of the Arctic. Transactions All-Union Petroleum Scientific-Research Geological-Prospecting Institute (VNIGRI), Bulletin, vol. 149, 218 p., 35 pls. (in Russian)
McCoy, F., 1851: Aviculopecten. Annals Magazine of Natu- ral History, vol. 2, p. 171.
Meek, F.B. and Worthen, A.H., 1866: Description of inverte- brates from the Carboniferous system. Illinois Geologi- cal Survey, vol. 2, Palaeontology, p. 143-411.
Muromtseva, A.V. ed., 1984: Permian marine deposits and bivalve molluscs of the Soviet Arctic, 154 p., 53 pls. Ministry of Geology, USSR, Leningrad (Nedra). (in Russian)
Nakamura, K., Kimura, G. and Winsnes, T.S., 1987: Bra- chiopod zonation and age of the Permian Kapp Staros- tin Formation (Central Spitsbergen). Polar Research, n. s. vol. 5, p. 207-219.
Nakamura, K., Kimura, G., Winsnes, T.S. and Lauritzen, O., 1990 : Permian and Permian-Triassic boundary in Cen- tral Spitsbergen. In, Tatsumi, T. ed., The Japanese Scientific Expedition to Svalbard 1983-1990, p. 137-153. Kyoikusha, Tokyo.
Nakamura, K., Tazawa, J. and Kumon, F., 1992: Permian brachiopods of the Kapp Starostin Formation. In, Japanese-Norwegian Research Group, Investigation on the Upper Carboniferous-Upper Permian succession of West Spitsbergen, 1989-1991, p. 77-95, pls. 1-5. Hok- kaido University.
Nakazawa, K., Nakamura, K. and Kimura, G., 1987 : Discov- ery of Otoceras boreale from West Spitsbergen. Pro- ceedings of Japan Academy, vol. 63, p. 171-174.
Nakazawa, K., Suzuki, H., Kumon, F. and Winsnes, T.S.,
1990: Japanese Geological Expedition to Svalbard in the summer of 1986. /n, Tatsumi, T. ed., The Japanese Scientific Expedition to Svalbard 1983-1990, p. 175-214. Kyoikusha, Tokyo.
Newell, N.D., 1938: Late Paleozoic pelecypods : Pectinacea. State Geological Survey of Kansas, vol. 10, 123 p., 20 pls.
Newell, N.D. and Boyd, D.W., 1995 : Pectinoid bivalves of the Permian-Triassic crisis. Bulletin of the American Museum of Natural History, no. 227, 95 p.
Newell, N.D., Chronic, J. and Roberts, T.G., 1953: Upper Paleozoic of Peru. Geological Society of America, Memoirs, vol. 58, 261 p., 34 pls.
Sakagami, S., 1992: Notes on the Permian bryozoans from Kapp Starostin Formation at Festningen route, Spitsber- gen. In, Japanese-Norwegian Research Group, Inves- tigation on the Upper Carboniferous-Upper Permian succession of West Spitsbergen, p. 40-57. Hokkaido University.
Stuckenberg, A., 1898: Allgemeine geologische Karte von Russland. Blatt 127. Mémoires du Comité Geologi- que, vol. 16, 361 p., 5 pls.
Toula, F., 1873: Kohlenkalk-Fossilien von der Sudspitze von Spitzbergen. Sitzungberichte der keyserlichen Akademie der Wissenschaften in Wien, Mathematisch- naturwissenschaftliche KI., vol. 68, pt. 1, p. 267-291.
Toula, F., 1875a: Kohlenkalk- und Zechstein-Fossilien aus dem Hornsund am der Süd-Westküste von Spitzbergen. Sitzungbericht der keyserlichen Akademie, Wien, Mathematisch-naturwissenschaftlich KI., vol. 70, pt.1, p. 133-157.
Toula, F., 1875b: Permo-Carbon-Fossilien von der West- küste von Spitzbergen. Neues Jahrbuch für Miner- alogie, Geologie und Paläontologie, 1875, p. 225-264, pls. 5-10.
Waterhouse, J.B., 1963: Etheripecten, a new Avicul- opectinid genus from the Permian. New Zealand Jour- nal of Geology and Geophysics, vol. 6, p. 193-196.
Waterhouse, J.B., 1969: Growth lamellae on the type species of the Upper Paleozoic bivalve Aviculopecten McCoy. Journal of Palaeontology, vol. 43, p. 1179-1183.
Waterhouse, J.B., 1982: Permian Pectinacea and Limacea (Bivalvia) from New Zealand. New Zealand Geological Survey, Palaeontological Bulletin, vol. 49, 75 p., 25 pls.
Waterhouse, J.B., 1987: Late Palaeozoic Mollusca and correlation from the south-east Bowen Basin, East Australia. Palaeontographica, Pal. A, vol. 198, p. 129- 233, pls. 1-14.
Yancey, T.E., 1985: Bivalvia of the H.S. Lee Formation (Permian) of Malaysia. Journal of Palaeontology, vol. 59, p. 1286-1297.
Zhang, R., 1977 : Class Bivalvia. In, Hubei Geological Insti- tute ed., Palaeontological Atlas of Central-South-China, Part 2, p. 470-533, pls. 189-202. Geological Press. (in Chinese)
Zhang, Y., 1981: Late Permian bivalves from Yunjia of Jahe, Hunan Province. Acta Palaeontologia Sinica, Vol. 20, no. 8, p. 260-265. (in Chinese with English abstract)
Paleontological Research, vol. 3, no. 1, pp. 18-28, 6 Figs., April 30, 1999
© by the Palaeontological Society of Japan
An early Late Cretaceous mammal from Japan, with reconsideration of the evolution of
tribosphenic molars
TAKESHI SETOGUCHI', TAKEHISA TSUBAMOTO’, HAJIME HANAMURA?’”’ and KIICHIRO HACHIY A’
‘Department of Geology and Mineralogy, Graduate School of Science, Kyoto University, Kitashirakawaoiwake-cho, Sakyo-ku,
Kyoto 606-8502, Japan
‘Department of Anatomy, School of Dentistry, Aichi-Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya 464-8650,
Japan
Division of Oral Aging, Resarch Institute of Advance Dental Science, Aichi-Gakuin University, 1-100 Kusumoto-cho, Chikusa-
ku, Nagoya 464-8650, Japan
Received 4 July 1998 ; Revised manuscript accepted 18 March 1999
Abstract.
The morphology of a mandibular fragment with a left lower molar discovered in the “Upper
Formation” (upper Cenomanian-lower Turonian) of the Mifune Group in central Kyushu, southwestern Japan, suggests that this fossil should be assigned to a new species of Late Cretaceous mammal, Sorlestes mifunensis sp. nov. (Infraclass Eutheria ; Order Proteutheria ; Family Zhelestidae). S. mifunen- sis is the oldest zhelestid yet recorded. Some workers suggest that the Zhelestidae have a close affinity with ungulates. A detailed comparison between the lower molar of the new species and those of ungulates supports this suggestion. The comparison also suggests that the Zhelestidae have a closer affinity with ungulates than the Zalambdalestidae and other contemporary mammals, and that S. mifunen- sis has a relatively primitive character within the Zhelestidae. This comparison leads us to revise the diagnoses of the family Zhelestidae and of the genus Sorlestes. The unique character of the entoconid- hypoconulid twinning seen in the Zhelestidae was probably caused by the movement of the hypoconid (the presumed first single talonid cusp seen in the first therian Kuehneotherium) to the buccal side, far away from the other talonid cusps. This twinning pattern is distinct from the twinning pattern seen in marsupials.
Key words: Japan, Late Cretaceous, Mesozoic mammal, Mifune Group, Sorlestes, tribosphenic molar
Introduction
It is generally believed that tribosphenic mammals first appeared around the Jurassic-Cretaceous boundary (Bown and Kraus, 1979; Kielan-Jaworowska et al, 1979b; Sigogneau-Russell, 1991). They are ancestors of the eu- therian and metatherian mammals which probably differ- entiated during the Neocomian (Early Cretaceous) (Kielan Jaworowska et al., 1979a ; Cifelli, 1993 ; Eaton, 1993 ; Wang et al., 1995). The eutherian orders radiated widely at the beginning of the Tertiary. However, recent fossil finds suggest that the eutherian orders may have originated and differentiated in the Late Cretaceous (Fox and Youzwyshyn, 1994 ; Archibald, 1996 ; Gheerbrant et al., 1996).
Until 20 years ago there were only very few reports of tribosphenic mammals from the early Late Cretaceous (Cenomanian-Santonian). This situation has, however,
changed and many such fossils are now known from this period (Cifelli and Eaton, 1987 ; Cifelli, 1993; Eaton, 1993 ; Nessov et al. 1994; Nessov et al., 1998). In particular, Nessov et al. (1994) report many early Late Cretaceous tribosphenic mammals from Middle Asia (Uzbekistan, Ka- zakhstan and Tajikistan).
In the present study, we document a mammal fossil specimen, which was first reported by Setoguchi (1992), from the “Upper Formation” (upper Cenomanian-lower Turonian ; lower Upper Cretaceous) of the Mifune Group in central Kyushu, southwestern Japan. The specimen is a small mandibular fragment with a tribosphenic lower molar. The new find is significant because it is the only known example of a mammal fossil from the Late Cretaceous eastern coastal lowlands of the Asian Continent. The other Asian Late Cretaceous mammal fossils, in contrast, come from either inland deposits or deposits along the Tethys sea and the
Late Cretaceous mammal from Japan 19
Turgai Strait of that time (Clemens et a/., 1979 ; Nessov et al., 1994).
The tooth nomenclature used in this contribution is that of Bown and Kraus (1979) and Nessov et al. (1998).
Geological setting
The present fossil material was discovered in the “Upper Formation” of the Mifune Group, which is distributed in the Mifune Town area of Kumamoto Prefecture, central Kyushu, southwestern Japan (Figure 1). The Mifune Group unconfor- mably overlies green schist associated with serpentinite in the northern area, and the Upper Permian Mizukoshi Forma- tion in the southern area (Matsumoto, 1939). The Mifune Group is, in turn, unconformably overlain by the Upper Cretaceous Gankaizan Formation (Tamura and Tashiro, 1966). The Mifune Group is considered to be early Late Cretaceous in age (see below), and to have formed in a sedimentary basin situated on the east coastal margin of the Late Cretaceous Asian Continent.
The Mifune Group has a total thickness of about 1,500 m and consists of “Basal”, “Lower” and “Upper” formations (Matsumoto, 1939). The lowermost or “Basal Formation” is
dominated by conglomerate and very coarse-grained sand- stone (Matsumoto, 1939), yielding fresh-water bivalves, such as Trigonioides, (Tamura, 1979; Matsumoto et al., 1982). The middle or “Lower Formation” is dominated by sandstone and sandy mudstone (Matsumoto, 1939), yielding brackish- water and shallow-marine molluscan fossils, such as /nocer- amus concentricus costatus and Eucalycoceras sp. cf. E. spathi of middle Cenomanian age (Tamura and Matsumura, 1974; Tamura, 1979; Matsumoto et al., 1982). The upper- most or “Upper Formation” is dominated by red mudstone (Matsumoto, 1939), yielding non-marine bivalves (Tamura, 1979) and several vertebrate fossils, such as dinosaurs, pterosaur, and the present specimen (Tamura et al., 1991; Setoguchi, 1992 ; Okazaki and Kitamura, 1996).
The Gankaizan Formation, which unconformably overlies the Mifune Group, consists of conglomerate, coarse-grained sandstone and red mudstone (Tamura and Tashiro, 1966 ; Matsumoto et al., 1982), yielding Inoceramus (Platyceramus) amakusensis, of lower Santonian age, in its upper part (Tamura and Tashiro, 1966 ; Matsumoto et al., 1982).
The present fossil material comes from the upper part of the “Upper Formation” near the Amagimi Dam, Mifune Town (Figure 1). The stratum where the fossil was discovered
AU
NE
OSSI
Figure 1. Topographic map showing the fossil locality, near the Amagimi Dam, Mifune Town, Kumamoto
Prefecture, Kyushu, southwestern Japan (a part of topographic map “Mifune”, 1 : 25,000 scale, Geographical Survey
Institute of Japan).
20 Takeshi Setoguchi et al.
Upper Formation (non-marine)
Mifune Group
(m., partly br.)
non-m.)
LL 5 a © a
Basement
Stratigraphy | T.(m)| Lithology Fossils
Inoogramus (Platyceramus) amakusenss ———® Lower Santonian
Sorlestes (KUJM 95002), Piicatounio, Gyraulus,
Pterodactyloidea, fam., gen. and sp. undetermined
Siragimelania Nipponicorbula mashikensis
Eucalycoceras sp. cf. E. spathh ——?® Middle Cenomanian Acanthotrigonia, Inoceramus, Septifer, Turritella Matsumotoa, Brachidontes, Crassostrea, Eomiodon, Tetoria, Pulsides ?Megalosauridae gen. et sp. indet.
Nipponicorbula mashikensis
Siragimelania
Trigonioides, Plicatounio
Figure 2. Stratigraphy of the Cretaceous deposits in the south of Kumamoto City, Kyushu, Japan (modified from Matsumoto, 1939 ; Tamura and Tashiro, 1966 ; Matsumoto et al., 1982 ; Tamura et al., 1991; Hasegawa et al.
1992 ; Okazaki and Kitamura, 1996). ss., sandstone ; cg., conglomerate.
consists of coarse-grained sandstone. The age of the “Upper Formation” is considered to be late Cenomanian to early Turonian on the basis of the ages of the Lower Formation and the Gankaizan Formation. A synthetic scheme of the stratigraphy of the Mifune Group is shown in Figure 2.
Systematic paleontology
Class Mammalia Linnaeus, 1758 Infraclass Eutheria Gill, 1872 Order Proteutheria (Romer, 1966) Butler, 1972 Family Zhelestidae (Nessov, 1985) Nessov, 1990
Revised diagnosis.—The upper and lower molars are typical tribosphenic types. The protocone is large and mesiodistally expanded. The stylar shelf is relatively narrow, but the parastylar region is wide and expanded mesially bearing two cusps. A small paraconid is displaced relatively lingually and relatively close to the metaconid. Compared with other proteutherians, the trigonid height is lower relative to talonid height. The talonid is about as wide as the trigonid and mesiodistally longer and lower than the trigonid.
Abbreviations : m., marine; br., brackish; T., thickness ; ms., mudstone ;
The talonid basin is deep and open lingually, so that the deepest part of the talonid basin is situated at its lingual margin. The entoconid and hypoconulid are markedly close to one another, and are quite clearly separated from the hypoconid.
The upper and lower last premolars are premolariform (sensu Krishtalka, 1976), but the upper one has a incipient metacone. In occlusal view, the upper one is somewhat mesiodistally constricted between the paracone and the protocone.
Genus Sorlestes Nessov, 1985
Type species.—Sorlestes budan Nessov, 1985.
Included species.—S. budan Nessov, 1985; S. kara Nes- sov, 1993; S. mifunensis sp. nov.
Revised diagnosis.—The paraconid is not strongly appres- sed to the metaconid. The protoconid is larger than in Aspanlestes (Zhelestidae). The entoconid is very markedly close to the hypoconulid (entoconid-hypoconulid twinning), and both are located at the distolingual corner of the talonid, opposite the hypoconid which is located at the distobuccal corner. The cristid obliqua extends just below the notch of
Late Cretaceous mammal from Japan
the protocristid between the protoconid and the metaconid.
Sorlestes mifunensis sp. nov. Figure 3
Holotype.—KUJM 95002, a left mandibular fragment with a molar. (KUJM means Kyoto University, Japan, Mesozoic)
Hypodigm.—The type specimen only.
Etymology.—Named after Mifune Town, where the type specimen was discovered.
Repository.—Department of Geology and Mineralogy, Division of Earth and Planetary Sciences, Graduate School of
[59]
Science, Kyoto University, Japan.
Locality.—Lat. 32°44’09” N ; Long. 130°50’32” E: Loc. 1 of Tamura et al. (1991, fig. 1; Figure 1), near the Amagimi Dam, Mifune Town, Kumamoto Prefecture, Kyushu, southwestern Japan.
Horizon. —Upper part of the “Upper Formation”, Mifune Group (Figure 2).
Age.—Late Cenomanian to early Turonian ; Late Cretaceous.
Diagnosis.— The lower molar of S. mifunensis is almost as large as S. budan, and larger than S. kara. Compared to S. budan, the paraconid is less appressed to the metaconid, and the entoconid and hypoconulid are closer together.
Figure 3. Sorlestes mifunensis sp. nov., KUJM 95002, holotype. A, A’, occlusal view (stereophotographic pair). B, lingual view. C, buccal view. D, D’, occlusal view of the preserved molar (stereophotographic pair). Scale bars=2 mm (left scale corresponds to A, A’, B, C, right scale corresponds to D, D’).
22 Takeshi Setoguchi et al.
Description —The type specimen (KUJM 95002) is a frag- mentary left mandible with a molar. The preserved part of the mandibular ramus is about 8 mm in length, and about 4 mm in height and about 2 mm in width below the preserved molar. Immediately mesial to the molar, there is a broken root, which is circular and not compressed anteroposteriorly in occlusal view (Figures 3-A, A’). Immediately distal to the molar, there is a broken alveolus. Mental foramen could not be identified in KUJM 95002.
The protoconid of the preserved molar is much larger and higher than the metaconid, and leans somewhat lingually. The metaconid is situated just lingual to the protoconid. Although badly broken at the base, it is clear that the paraconid is near the anteroposterior midline, and less anteriorly appressed than in S. budan. There is no crest joining the paraconid with the metaconid. A distinct precin- gulid runs downward from the mesiobuccal base of the paracristid notch, disappearing at the buccal base of the protoconid. The posterior trigonid wall is almost vertical, and nearly perpendicular to the mandibular extension.
The talonid is longer than wide. It is longer than, as wide as, and roughly half as tall as the trigonid. The hypoconid and entoconid are almost the same height, and somewhat higher than the hypoconulid. The hypoconulid is only very slightly projected posteriorly. The entoconid and hypoconulid are closer together than in S. budan, and are located at the distolingual corner of the talonid. A very weak postcingulid runs down buccally from the hypoconulid, disappearing at the buccal base of the hypoconid. The deepest part of the
vi AP >
k TALL % TRIL y I
TRIW
Figure 4. Orientations of the measurements of lower molars (modified from Nessov et a/., 1994). Buccal to top of page ; anterior to right. Abbreviations are shown in Table 1.
Table 1. sp. nov.
talonid basin is situated at its lingual margin, so that the deep talonid basin is open lingually, and inclined lingually as a whole. The cristid obliqua originates directly below the notch between the protoconid and the metaconid, and is much higher than the entocristid. The hypoflexid is well- formed and deep.
Wear facets can be observed from the tip of the protoconid to the tip of the metaconid through the proto- cristid. The tips of the hypoconid, hypoconulid and entoconid are slightly worn. The talonid basin is also worn (although the effects of secondary erosion are difficult to assess), which forms a U-shaped “wear facet”.
Dental measurements are given in Table 1 and Figure 4.
Discussion
Identification of the present lower molar
The tooth class of the molar preserved in KUJM 95002 can be identified as M., because the trigonid is as wide as the talonid which is the same as on M, of S. budan. The possibility that it should be identified as M, cannot, however, be immediately excluded. As Lillegraven (1976) pointed out, it is a usual therian condition that the paraconid is most buccally set on M, and becomes progressively more lingual on M.-M;. Furthermore, Cretaceous eutherians character- istically have a protoconid that leans somewhat more lin- gually on M, than that on M,, so the distance between the tip of the protoconid and that of the metaconid in occlusal view is shorter on M, than that on M,. These characters are also observed in the zhelestid Aspanlestes (Nessov et al., 1994, pl. 4, fig. 1). KUJM 95002 shows a combination of these M, characters.
In either case, KUJM 95002 and S. budan clearly have distinct lower molar structures (see diagnosis of S. mifunen- sis). S. kara, another species of Sorlestes, has much smaller molar size than KUJM 95002. We, therefore, consider KUJM 95002 to be a new species of Sorlestes.
Phyletic position of Sorlestes mifunensis
Phylogenetic relationships of the Zhelestidae have been discussed by various workers (Figure 5). Lillegraven (1976) described Gallolestes, which was subsequently classified as belonging to the Zhelestidae by Nessov et al. (1994), based on the lower molar morphology. Lillegraven (1976) favors eutherian affinities for Gallolestes, and points out the similar- ities between Gallolestes and hyopsodontid condylarths. Butler (1977), however, points out that Gallolestes shares some derived characters of the lower molars with Zalamb- dalestes (Proteutheria; Zalambdalestidae) and with Pur- gatorius (Primatomorpha), and he doesn't exclude the possi-
Measurements (in mm) of the preserved molars of the type specimens of Sorlestes mifunensis The measurements are oriented as shown in Nessov et al. (1994, fig.1; see Figure 4).
Abbreviations : AP, anteroposterior length; TRIL, trigonid length; TALL, talonid length; TRIW, trigonid
widt!
; TALW, talonid width. PTS Er [mm] AP
TRIL TALL TRIW TALW
KUJM 95002 (S. mifunensis) left lower molar (M, or M.)
1.15 1.45 1.75 | 1.70 | | |
Late Cretaceous mammal from Japan 23
Nessov (1985) Butler (1990) : based on the|/based on the Pt EME Kennalestidae Kennalestes Sorlestes Zhelestes Zhelestes Aspanlestes Taslestes Mixotheridia Gallolestes Pe Coreundulates’) close to ungulates Family u Sorlestes Aspanlestes close to Taslestes Zalambdalestidae ? Gallolestes Zalambdalestidae
Nessov et al. (1994) Archibald (1996) &
Nessov et al. (1998)
mainly based on
the morphology of the lower molars
mainly based on the morphology of
Proteutheria the upper molars
Kennalestidae
Mixotheridia Kennalestidae
("preungulates") Zalambdalestidae Zhelestidae
Zhelestes
Sorlestes Ungulato! Aspanlestes Zhelestidae
Taslestes
Ungulata Gallolestes
Zalambdalestidae
Figure 5. The classifications and phylogenetic relationships used in recent studies for the Zhelestidae.
bility of a relationship between Gallolestes and Protun- gulatum (Condylarthra). Clemens (1980) concludes that Gallolestes is possibly a representative of another lineage of metatherian-eutherian grade of dental evolution that cannot be assigned to either the Eutheria and Metatheria.
Based on the lower molar morphology, Nessov (1985) suggests that Tas/estes, Aspanlestes, Sorlestes and Gal- lolestes should be combined in the same taxonomic group, a group which was subsequently classified as belonging to the Zhelestidae in Nessov et al. (1994). Nessov (1985) proposed a new suborder Mixotheridia (Proteutheria) includ- ing both the above genera and the Zalambdalestidae, and suggested that this suborder was related to condylarths. In the same paper, he described a new genus Zhelestes, based on the upper dentition. He classified it into the new sub- family Zhelestinae (Proteutheria ; Kennalestidae), and at this time didn't include it in the Mixotheridia. Later, he raised this subfamily to the family level (Nessov, 1990). Butler (1990) points out that the zalambdalestids differ from Aspan- lestes, Sorlestes and Gallolestes in some molar features, suggesting that relationships of these genera to zalamb- dalestids is not impossible, but it needs to be substantiated. He also considers that Zhelestes might be an earlier repre- sentative of condylarths. According to Nessov et al. (1994), the Zhelestidae include Gallolestes, Taslestes, Aspanlestes and Sorlestes, and these are all included in the suborder Mixotheridia along with the Zalambdalestidae. They con- sider the Mixotheridia (both the Zhelestidae and the Zalamb- dalestidae) to be “preungulates”. In contrast, based mainly on the upper molars morphology, Archibald (1996) and Nessov et al. (1998) consider that the Zhelestidae are sister groups of ungulates, and the Zalambdalestidae are only distantly related to them.
In this paper, we follow the suggestions of Archibald (1996) and Nessov et al. (1998). The reasons for our preference are briefly summarized below.
On the basis of the lower molar structure, Nessov et dl. (1994) claimed that both the Zhelestidae and the Zalamb- dalestidae are closely related to ungulates. However, the two families show the following differences: (1) The Zhe- lestidae have more low-crowned lower molars with a trigonid that is less elevated to the talonid (Butler, 1990). (2) The paraconid and metaconid in the Zhelestidae are less closely appressed than in the Zalambdalestidae. (3) The Zhe- lestidae have a lingually open talonid, whereas the talonid is lingually closed in the Zalambdalestidae (see Kielan-Jawor- owska, 1984, pl. 14,15). In these features, the Zhelestidae are morphologically more similar to early ungulates than to the Zalambdalestidae. Most early ungulates (for instance, Protungulatum, Diacodexis, and so on) share the diagnostic characteristics of zhelestids, that is, the high, large, wide and lingually open talonid with the hypoconulid situated markedly close to the entoconid, and the rather lingually displaced paraconid with some appression to the metaconid (see McKenna, 1960, figs. 52, 53, 56, 57 ; Archibald, 1982, figs. 56, 60; Estravis and Russell, 1989, pl.1; Rose, 1996, fig. 1). This combination of characteristics is not seen in any other contemporary mammal. For example, in Purgatorius, an early primatomorphan, the talonid is large, wide and high, but is Closed lingually with the hypoconulid situated centrally (see Clemens, 1974, fig.2; Buckley, 1997, fig.1). In Gypsonictops, a Late Cretaceous insectivore, the talonid is large, wide and somewhat lingually open. However, the hypoconulid is centrally situated, and the paraconid is situ- ated rather centrally than lingually (see Clemens, 1973, figs. 1,4; Cifelli, 1990, fig. 2).
Based mainly on an analysis of upper molar morphology, Archibald (1996) and Nessov et al. (1998) suggest that the Zalambdalestidae does not have a close affinity with un- gulates. Similarly, a study of lower molar morphology indi- cates that the Zhelestidae most closely resemble early ungulates. The lingually closed talonid in the Zalambaa-
24 Takeshi Setoguchi et al.
lestidae, which is shared by many other eutherians, may be an apomorphic character which zhelestids and early un- gulates do not posses (see below). This would imply that the Zalambdalestidae should be excluded from a very close relationship with ungulates. In support of this idea, some workers (Van Valen, 1964; McKenna, 1975; Stucky and McKenna, 1993; Archibald, 1996) consider the Zalambda- lestidae to be more closely related to Anagale and rabbits.
Compared with the Zhelestidae, early ungulates have a relatively high talonid with robust cusps on the lower molars. Compared to the other representatives of the Zhelestidae, Sorlestes mifunensis shows a primitive characteristic in that the paraconid is less appressed to the metaconid.
Nessov (1993) created a new family Kulbeckiidae (consist- ing of a single new genus Kulbeckia) within the Mixotheridia. In the Kulbeckiidae, the hypoconulid is markedly close to the entoconid, and the paraconid is lingually situated with appression to the metaconid, similar to the Zhelestidae. Unfortunately, it is not clear whether the talonid is open or not in the Kulbeckiidae, so it is difficult to discuss any possible relationship between the Zhelestidae, Kulbeckiidae and other mammals.
Evolution of tribosphenic molars
The most characteristic feature of Sorlestes mifunensis is the lower molar with the hypoconulid situated markedly close to the entoconid, quite clearly opposed to the hypoconid. This twinning pattern is rarely seen in other Cretaceous eutherians, in which the hypoconulid is centrally-located between the hypoconid and the entoconid. The recognition of this character prompted us to reconsider the evolution of the talonid cusps. It seems that the talonid cusps devel- oped along with the occluding upper tooth and the adjacent lower tooth.
1. First cusp formed in the talonid of Kuehneotherium, the first therian mammal: The earliest therian mammal, Kuehneotherium, had already appeared by the Norian (Late Triassic) (Fraser et al., 1985). In the lower molars of Kueh- neotherium, the tallest and largest Cusp can be recognized as homologous with the protoconid of the later tribosphenic molars. The other two cusps, which are situated mesiolin- gually and distolingually from the protoconid, can likewise be identified as equivalents of the paraconid and metaconid, respectively (Kermack et a/., 1968). These homologies of the trigonid Cusps are now not really in debate (Slaughter, 1971).
In the lower molars of Kuehneotherium, there is, however, a unicuspid distal heel or talonid, posterior to the trigonid (Kermack et al., 1968, fig. 3). The homology of this cusp has been discussed by several workers (Slaughter, 1971; Clemens and Lillegraven, 1986), and the two main opinions are that it corresponds to either the hypoconid or hypoconulid.
Mills (1967) used the occlusal relationship between the upper and lower molars to propose that the single talonid cusp of Jurassic pantotheres corresponds to the hypoconid on the basis of the occlusal relationship between the upper and lower molars. The same conclusion was also reached by Freeman (1979) and Prothero (1981). In contrast, Kermack
(1967) interpreted the single talonid cusp in Welsh pantothere (Kuehneotherium) as the hypoconulid on the basis of the relationship between the talonid and its following tooth. Crompton (1971), Slaughter (1971) and Butler (1978) also correlated this cusp with the hypoconulid, although the latter didn't completely exclude the possibility that it could repre- sent the hypoconid.
The next stage in evolution toward the tribosphenic molar is seen in Amphitherium or Palaeoxonodon, whose talonid extends distobuccally from the base of the metaconid and bears a large single cusp at its distobuccal margin (Simpson, 1928, fig. 38 ; Freeman, 1979, pls. 16,17). In Palaeoxonodon, there is a small cuspule at the approximate median point of the oblique crest which links the metaconid and a large single talonid cusp (Freeman, 1979). Further development is seen in Peramus. In this genus the talonid bears two or three cusps, identified as the hypoconid, hypoconulid and entoconid of the tribosphenic molar (Clemens and Mills, 1971; Clemens and Lillegraven, 1986). The talonid basin is not fully basined and is open lingually (Clemens and Mills, 1971, pl. 3).
By comparing the molar morphology of the animal mentioned above with later tribosphenic mammals, we consider that the single talonid cusp seen in Kuehneother- jum corresponds to the hypoconid, as proposed by Mills (1967). This suggestion is also supported by the following arguments. (1) We would like to stress the occlusal relation- ship between the upper main cusp (paracone) and the first talonid cusp. The paracone is the largest cusp in the upper molar and is functionally very important for masticating foods. We, therefore, propose that the occlusal relationship between the paracone and the single talonid cusp, as well as between the paracone and the protoconid, is likely to be maintained in the therians. (2) In Amphitherium or Palae- oxonodon, the talonid extends distobuccally from the base of the metaconid and bears a large single cusp at its distobuc- cal margin, where the hypoconid of the tribosphenic molar is situated. (3) We propose, furthermore, that the groove separating the hypoconid and the hypoconulid in tribos- phenic molars is also significant. This groove is deeper and stronger than the groove separating the hypoconulid and the entoconid, so the hypoconulid and entoconid are likely to be related more closely to each other than to the hypoconid. (4) Freeman (1979) stated that in certain specimens of Palaeoxonodon there is an incipient development of the entoconid and hypoconulid in addition to the large talonid cusp situated distobuccally.
We, therefore, propose the following sequential develop- ment. The first talonid cusp seen in Kuehneotherium corre- sponds to the hypoconid, and the entoconid and hypoconulid appeared at some later stage, being more closely related to each other than to the hypoconid.
2. Entoconid-hypoconulid twinning: The primitive talonid for a tribosphenic molar envisaged by most workers is basined and lingually opened with a relatively large hypoconid, smaller hypoconulid and in some cases also an entoconid (Clemens and Lillegraven, 1986; Szalay, 1994). Examination of Early Cretaceous tribosphenic mammals suggests that the roughly centrally-placed hypoconulid
Late Cretaceous mammal from Japan
between the hypoconid and the entoconid may also be a primitive Characteristic.
In Late Cretaceous mammals, the lower molars of many eutherians have a centrally-placed hypoconulid. In con- trast, the molars of contemporary marsupials have a hypoconulid twinned with an entoconid. In this respect the molars of the eutherian Zhelestidae resemble those of marsupials. However, the twinning in the Zhelestidae is clearly distinct from that in marsupials (Figure 6).
In marsupials, the hypoconulid is distolingually displaced compared to the Zhelestidae. The twinning pattern seen in the Zhelestidae is associated with a primitive-type talonid as seen in the tribosphenic pattern. This association suggests that the twinning seen in the Zhelestidae is more primitive than in marsupials. The twinning pattern seen in the Zhelestidae is likely to have been caused by the movement of the hypoconid to the buccal side far away from the other talonid cusps, corresponding to the expansion of the protocone of the upper molars (Archibald, 1996 ; Nessov et al., 1998). The twinning pattern seen in marsupials is more likely to be a secondary feature (Cifelli, 1993), and could be functionally related to the early trend of the enlargement of the metacone and reduction of the paracone in this group (Clemens and Lillegraven, 1986).
The entoconid-hypoconulid twinning is also related to the position of the paraconid of the posterior molar. This is because the paraconid fits into the groove between the hypoconulid and the entoconid of the anterior tooth. In many eutherians, the paraconid is situated centrally,
Zhelestidae Other eutherians and ungulates sone hypoconulid
Nw Nn
because the hypoconulid of the anterior tooth is centrally- placed between the hypoconid and the entoconid, and the groove between the hypoconulid and the entoconid is situated more buccally. In the Zhelestidae, the paraconid is situated more lingually than centrally, because the hypoconulid is situated lingually and twinned with the entoconid, and the groove between the two cusps is situated more lingually than centrally. In marsupials, the paraconid is situated more mesiolingually than in eutherians (include the Zhelestidae), because the hypoconulid of the anterior tooth is situated more distolingually and twinned with the entoconid, and the groove between the two cusps is situated far more distolingually.
As mentioned above, the lingually open talonid with a hypoconulid markedly close to the entoconid as seen in the Zhelestidae is probably a reflection of the primitive state. This condition is also seen in early eutherian like Proken- nalestes (Kielan-Jaworowska and Dashzeveg, 1989, figs. 26, 27), but not seen in early metatherian, Kokopellia (Cifelli, 1998, fig. 1).
Co-evolution of mammals and plants
The age from the Albian to the Cenomanian was a very important period for the mammalian evolution. At this time the flora underwent a change from one dominated by ferns and gymnosperms to one with abundant angiosperms. Flowering angiosperms appeared at the beginning of the Cretaceous, and very rapidly became a major plant group (Crane, 1987 ; Collinson, 1990). Angiosperms have leaves,
Marsupials protoconid
entoconid paraconid metaconid deepest part of the talonid basin Primitive tribosphenic pattern buccal distal Eu mesial lingual
O O ee)
Figure 6. Comparisons of the lower molar patterns of tribosphenic mammals (occlusal view of the left lower
molars).
26 Takeshi Setoguchi et al.
flowers, fruit, pollen and honey. In other words, these plants have foods with high nutritive value. It was for this reason that insects began to evolve explosively at this time. It follows, therefore, that insectivorous mammals, whose staple foods were insects and/or larvae of insects, also began to increase in numbers and diversity. The mammals who began to diversify and radiate in this way are the Cretaceous tribosphenic mammals. The period when the Mifune Group was deposited is the very period when angiosperms had become a major plant group, and when insectivorous mam- mals like Sorlestes evolved rapidly.
Conclusions
Morphological studies of the mammalian remain discov- ered from the lower Upper Cretaceous Mifune Group in central Kyushu, southwestern Japan suggest that it should be assigned to a new species of the genus Sorlestes (Order Proteutheria ; Family Zhelestidae), and is here named S. mifunensis.
The lower molars of the Zhelestidae exhibit a series of ungulate-like characteristics. It suggests that the Zhe- lestidae and early ungulates are far more closely related to each other than to the Zalambdalestidae and other mam- mals. The twinning pattern of the hypoconulid and entoconid in the Zhelestidae, including Sorlestes mifunensis, shows a more primitive state than that of metatherians and most of the other eutherians.
Sorlestes mifunensis is the oldest known zhelestid yet recorded, and suggests that the origin of ungulates perhaps goes back even further to the early Late Cretaceous, or at least, that mammals having ungulate-like characters had already been differentiated by the late Cenomanian to early Turonian. The find of Sorlestes mifunensis also indicates that zhelestid existed not only in western Asia but also on the coastal plain of eastern Asia.
Acknowledgments
We are grateful to Kazuhiro Koyasu of Aichi-Gakuin University, who donated the specimen to Kyoto University. Our thanks also go to Naoki Ikegami of Mifune Board of Education, who gave us facilities in our field work. Thanks are also due to Hidetoshi Kamiya of Kyoto University, who gave the specimen number to the present material. We would like to express our sincere gratitude to Masanaru Takai of Kyoto University Primate Research Institute for his critical reading of the manuscript and taking the photographs of the specimen, to Naoki Kohno of National Science Museum and Simon R. Wallis of Kyoto University for their critical reading of the manuscript, and to Haruyoshi Maeda of Kyoto University for his advice about the construction of the manuscript. This manuscript was improved following con- structive reviews by two anonymous referees.
This research was partly supported by Grant-in-Aid for JSPS Fellows from the Ministry of Education, Science, Sports and Culture of Japan to Takehisa Tsubamoto (No. 9714).
References
Archibald, J.D., 1982: A study of Mammalia and geology across the Cretaceous-Tertiary boundary in Garfield County, Montana. University of California Publications in Geological Sciences, vol. 122, xvi+286 p.
Archibald, J.D., 1996 : Fossil evidence for a Late Cretaceous origin of “hoofed” mammals. Science, vol. 272, no. 5265, p. 1150-1153.
Bown, T.M. and Kraus, M.J., 1979 : Origin of the tribosphenic molar and metatherian and eutherian dental formulae. In, Lillegraven, J.A., Kielan-Jaworowska, Z. and Clemens, W.A. eds., Mesozoic Mammals: The First Two-Thirds of Mammalian History, p. 172-181. Univer- sity of California Press, Berkeley.
Buckley, G.A., 1997: A new species of Purgatorius (Mam- malia ; Primatomorpha) from the Lower Paleocene Bear Formation, Crazy Mountains Basin, south-central Montana. Journal of Paleontology, vol. 71, no. 1, p. 149- 155.
Butler, P.M., 1972: The problem of insectivore classification. In, Joysey, K.A. and Kemp, T.P. eds., Studies in Verte- brate Evolution, p. 253-265. Oliver and Boyd, Edin- burgh.
Butler, P.M., 1977 : Evolutionary radiation of the cheek teeth of Cretaceous placentals. Acta Palaeontologica Polonica, vol. 22, p. 241-271.
Butler, P.M., 1978: Molar cusp nomenclature and homology. In, Butler, P.M. and Joysey, K.A. eds., Development, Function and Evolution of Teeth, p. 439-453. Aca- demic Press, San Diego.
Butler, P.M., 1990: Early trends in the evolution of tribos- phenic molars. Biological Reviews of the Cambridge Philosophical Society, vol. 65, p. 529-552.
Cifelli, R.L., 1990: Cretaceous mammals of southern Utah. IV. Eutherian mammals from the Wahweap (Aquilan) and Kaiparowits (Judithian) Formations. Journal of Vertebrate Paleontology, vol. 10, no. 3, p. 345-360.
Cifelli, R.L., 1993: Early Cretaceous mammal from North America and the evolution of marsupial dental charac- ters. Proceedings of the National Academy of Sci- ences of the United States of America, vol. 90, no. 20, p. 9413-9416.
Cifelli, R.L. and Eaton, J.G., 1987: Marsupial from the ear- liest Late Cretaceous of Western US. Nature, vol. 325, no. 6104, p. 520-522.
Clemens, W.A., 1973: Fossil mammals of the type Lance Formation, Wyoming. Part3. Eutheria and summary. University of California Publications in Geological Sci- ences, vol. 94, vi+102 p.
Clemens, W. A., 1974: Purgatorius, an early Paromomyid primate (Mammalia). Science, vol.184, no. 4139, p. 903-905.
Clemens, W.A., 1980: Gallolestes pachymandibularis (Ther- ia, incertae sedis; Mammalia) from Late Cretaceous deposits in Baja California del Norte, Mexico. PaleoBios, no. 33, p. 1-10.
Clemens, W.A. and Lillegraven, J.A., 1986: New Late Cretaceous, North American advanced therian mam- mals that fit neither the marsupial nor eutherian molds. Contributions to Geology, University of Wyoming, Spe- cial Paper 3, p. 55-85.
Clemens, W.A., Lillegraven, J.A., Lindsay, E.H. and Simpson,
Late Cretaceous mammal from Japan 27
G.G., 1979: Where, when, and what —A survey of known Mesozoic mammal distribution. In, Lillegraven, J.A., Kielan-Jaworowska, Z. and Clemens, W.A. eds., Mesozoic Mammals: The First Two-Thirds of Mam- malian History, p. 7-58. University of California Press, Berkeley.
Clemens, W.A. and Mills, J.R.E., 1971: Review of Peramus tenuirostris Owen (Eupantotheria, Mammalia). Bulletin of British Museum (Natural History) Geology, vol. 20, no. 3, p. 87-113.
Collinson, M.E., 1990: Angiosperms. In, Briggs, D.E.G. and Crowther, P.R. eds., Palaeobiology : A Synthesis, p. 79- 84. Blackwell Science Ltd., Oxford.
Crane, P.R., 1987 : Vegetational consequences of the an- giosperm diversification. In, Friis, E.M., Chaloner, W.G. and Crane, P.R. eds., The origins of angiosperms and their biological consequences, p. 107-144. Cambridge University Press, New York.
Crompton, A.W., 1971: The origin of the tribosphenic molar. In, Kermack, D.M. and Kermack, K.A. eds., Early mam- mals, Supplement 1 to the Zoological Journal of the Linnean Society of London, vol. 50, p. 65-102, pls. 1-2. Academic Press, London.
Eaton, J.G., 1993: Therian mammals from the Cenomanian (Upper Cretaceous) Dakota Formation, southwestern Utah. Journal of Vertebrate Paleontology, vol. 13, no. 1, p. 105-124.
Estravis, C. and Russell, D.E., 1989: Decouverte d'un nouveau Diacodexis (Artiodactyla, Mammalia) dans l'Eocene inferieur de Silveirinha, Portugal. Palaeover- tebrata, Montpellier, vol. 19, fasc. 1, p. 29-44, pls. 1-2. (in French with English abstract)
Fox, R.C. and Youzwyshyn, G.P., 1994: New primitive car- nivorans (Mammalia) from the Paleocene of Western Canada, and their bearing on relationships of the order. Journal of Vertebrate Paleontology, vol. 14, no. 3, 382- 404.
Fraser, N.C., Walkden, G.M. and Stewart, V., 1985: The first pre-Rhaetic therian mammal. Nature, vol. 314, no. 6007, p. 161-163.
Freeman, E.F., 1979: A Middle Jurassic mammal bed from Oxfordshire. Palaeontology, vol. 22, part 1, p. 135-166.
Gheerbrant, E., Sudre, J. and Cappetta, H., 1996: A Palaeocene proboscidean from Morocco. Nature, vol. 383, no. 6595, p. 68-70.
Hasegawa, Y., Murata, M., Wasada, K. and Manabe, M., 1992 : The first carnosaur (Saurischia ; Theropoda) from Japan: A tooth from the Cenomanian Mifune Group of Kyushu. Science Reports of the Yokohama National University, Sec. Il, Biology and Geology, no. 39, p. 41- 49.
Kermack, D.M., Kermack, K.A. and Mussett, F., 1968: The Welsh pantothere Kuehneotherium praecursoris. ZOo- logical Journal of the Linnean Society of London, vol. 47, p. 407-423, pls. 1-3.
Kermack, K.A., 1967: Molar evolution in Mesozoic mam- mals. Journal of dental Research, vol. 46, Supplement to no. 5, part1, p. 792-795.
Kielan-Jaworowska, Z., 1984: Evolution of the therian mammals in the Late Cretaceous of Asia. Part V. Skull structure in Zalambdalestidae. Palaeontologia Polonica, no. 46. p. 107-117, pls. 14-17.
Kielan-Jaworowska, Z., Bown, T.M. and Lillegraven, J.A.,
1979a: Eutheria. In, Lillegraven, J.A., Kielan-Jawor- owska, Z. and Clemens, W.A. eds., Mesozoic Mammals : The First Two- Thirds of Mammalian History, p. 221-258. University of California Press, Berkeley.
Kielan-Jaworowska, Z. and Dashzeveg, 1989: Eutherian mammals from the Early Cretaceous of Mongolia. Zoologica Scripta, vol. 18, no. 2, p. 347-355.
Kielan-Jaworowska, Z., Eaton, J.G. and Bown, T.M., 1979b : Theria of metatherian-eutherian grade. In, Lillegraven, J.A., Kielan-Jaworowska, Z. and Clemens, W.A. eds., Mesozoic Mammals: The First Two-Thirds of Mam- malian History, p.182-191. University of California Press, Berkeley.
Krishtalka, L., 1976: Early Tertiary Adapisoricidae and Erinaceidae (Mammalia, Insectivora) of North America. Bulletin of Carnegie Museum of Natural History, no. 1, p. 1-40.
Lillegraven, J.A., 1976: A new genus of therian mammal from the Late Cretaceous “El Gallo Formation,” Baja California, Mexico. Journal of Paleontology, vol. 50, no. 3, p. 437-443.
Matsumoto, T., 1939 : Geology of Mifune distinct, Kumamoto Prefecture, Japan (with special reference to the Cretaceous System). Journal of the Geological Society of Japan, vol. 46, no. 544, p.1-12. (in Japanese with English abstract)
Matsumoto, T., Obata, |., Tashiro, M., Ohta, Y., Tamura, M. Matsukawa, M. and Tanaka, H., 1982: Correlation of marine and non-marine formations in the Cretaceous of Japan. Fossils (Palaeont. Soc. Japan), no. 31, p. 1-26. (in Japanese with English abstract)
McKenna, M.C., 1960: Fossil Mammalia from the early Wasatchian four mile fauna, Eocene of Northwest Colorado. University of California Publications in Geo- logical Sciences, vol. 37, vi+130 p.
McKenna, M.C., 1975: Toward a phylogenetic classification of the Mammalia. In, Luckett, W.P. and Szalay, F.S. eds., Phylogeny of the Primates : A Multidisciplinary Approach, p. 21-46. Plenum Press, New York.
Mills, J.R.E., 1967 : Development of the protocone during the Mesozoic. Journal of dental Research, vol. 46, Supple- ment to no. 5, part 1, p. 787-791.
Nessov, LA. 1985: New mammals from the Late Cretaceous of Kyzylkum. Vestnik Leningradskogo universiteta. Ser. 7, Geologiya, geografiya, no. 17, p. 8- 18. (in Russian with English summary)
Nessov, L.A., 1990: Ichthyornithiform birds and other bird remains from the Bissekty Formation (Upper Cretaceous) of the Central Kyzylkum Desert. Travaux de l'Institut zoologique de |’Academie des sciences de l'URSS, vol. 210, p. 56-62, pls.1,2. (in Russian with English summary)
Nessov, L.A., 1993 : New Mesozoic mammals of Middle Asia and Kazakhstan and comments about evolution of theriofaunas of Cretaceous coastal plains of ancient Asia. Travaux de l'Institut zoologique de |’Academie des sciences de l'URSS, vol. 249, p. 105-133, pls. 1-6. (in Russian with English summary)
Nessov, L.A., Archibald, J.D. and Kielan-Jaworowska, Z., 1998: Ungulate-like mammals from the Late Cretaceous of Uzbekistan and a phylogenetic analysis of Ungulatomorpha. Bulletin of Carnegie Museum of Natural History, vol. 34, p. 40-88.
28 Takeshi Setoguchi et al.
Nessov, L.A., Sigogneau-Russell, D. and Russell, D.E., 1994 : A survey of Cretaceous tribosphenic mammals from Middle Asia (Uzbekistan, Kazakhstan and Tajikistan), of their geological setting, age and faunal environment. Palaeovertebrata, Montpellier, vol. 23, fasc. 1-4, p. 51-92, pls. 1-9.
Okazaki, Y. and Kitamura, N., 1996: The first discovery of a pterosaur from the Cretaceous Mifune Group, Kyushu, Japan. Bulletin of the Kitakyushu Museum of National History, no. 15, p. 133-136.
Prothero, D.R., 1981: New Jurassic mammals from Como Bluff, Wyoming, and the interrelationships of non-tribos- phenic Theria. Bulletin of American Museum of Natu- ral History, vol. 167, p. 277-326.
Romer, A.S., 1966: Vertebrate Paleontology (Third Edition), ix+468 p. University of Chicago Press, Chicago. Rose, K.D., 1996: On the origin of the order Artiodactyla. Proceedings of the National Academy of Sciences of the United States of America, vol. 93, no. 4, p. 1705-
1709.
Setoguchi, T., 1992: Complete Mesozoic tribosphenic type of molar found in Japan. Dental Outlook, vol. 80, no. 4, p. 861-870. (in Japanese)
Sigogneau-Russell, D., 1991: Discovery of the first tribos- phenic mammal from the Mesozoic of Africa. Comptes Rendus de l'Academie des Sciences, t. 313, ser. Il, p. 1635-1640. (in French with abridged English version)
Simpson, G.G., 1928: A Catalogue of the Mesozoic Mam- malia in the Geological Department of the British Museum, 215p., 12 pls. The British Museum (Natural History), London.
Slaughter, B.H., 1971: Mid-Cretaceous (Albian) therians of the Butler Farm local fauna, Texas. /n, Kermack, D.M. and Kermack, K.A. eds., Early mammals, Supplement 1
to the Zoological Journal of the Linnean Society of London, vol. 50, p. 131-143. Academic Press, London.
Stucky, R.K. and McKenna, M.C., 1993: Mammalia. In, Benton, M.J. ed., The Fossil Record 2, p. 739-771. Chapman and Hall, London.
Szalay, F.S., 1994: Evolutionary History of the Marsupials and an Analysis of Osteological Characters, xii+ 481 p. Cambridge University Press, New York.
Tamura, M., 1979: Cenomanian bivalves from the Mifune Group, Japan. Part 3. Memoirs of the Faculty of Edu- cation, Kumamoto University, Natural Science, no. 28, p. 59-74.
Tamura, M., Okazaki, Y. and Ikegami, N., 1991 : Occurrence of carnosaurian and herbivorous dinosaurs from Upper Formation of Mifune Group, Japan. Memoirs of the Faculty of Education, Kumamoto University, Natural Science, no. 40, p. 31-45. (in Japanese with English abstract)
Tamura, M. and Matsumura, M., 1974: On the age of the Mifune Group, central Kyushu, Japan. Memoirs of the Faculty of Education, Kumamoto University, Natural Science, no. 23, p. 47-57.
Tamura, M. and Tashiro, M., 1966: Upper Cretaceous Sys- tem south of Kumamoto. Memoirs of the Faculty of Education, Kumamoto University, Natural Science, no. 14, p. 24-35. (in Japanese with English abstract)
Van Valen, L., 1964: A possible origin for rabbits. Evolu- tion, vol. 18, p. 484-491.
Wang, Y., Hu, Y., Zhou, M. and Li, C., 1995: Mesozoic mammal localities in western Liaoning, Northeast China. In, Sun, A. and Wang, Y. eds., Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers, p. 221-227. China Ocean Press, Beijing.
Paleontological Research, vol. 3, no. 1, pp. 29-35, 3 Figs., April 30, 1999
© by the Palaeontological Society of Japan
A new cheirolepidiaceous conifer from the Lower Cretaceous
(Albian) of Hokkaido, Japan
KEN'ICHI SAIKI
Department of Plant Science, Natural History Museum and Institute, Chiba 955-2, Aoba, Chuo-ku, Chiba 260-8682, Japan
Received 8 August 1998 ; Revised manuscript accepted 28 November 1998
Abstract. A new fossil conifer, Pseudofrenelopsis glabra sp. nov., (Cheirolepidiaceae) is described based on a single specimen obtained from the Lower Cretaceous Yezo Group (Albian) of Hokkaido, Japan. The new species is characterized by cuticle possessing thin periclinal walls, a well-developed hypodermis, and absence of trichomes on internode and outer leaf surface. Recently, the author described Frenelopsis pombetsuensis from the Lower Cretaceous Yezo Group (Albian) of Hokkaido. The family Cheiro- lepidiaceae is a diagnostic taxon of the Ryoseki-type element that is reported only from the Ryoseki- and the Mixed-type floras. Thus Pseudofrenelopsis glabrais the second evidence of the Ryoseki-type element
from Hokkaido.
Key words: Albian, conifer, Hokkaido, Middle Yezo Group, Pseudofrenelopsis glabra, Ryoseki-type floras.
Introduction
Jurassic and Early Cretaceous floras in eastern Eurasia have been classified by Kimura (1980, 1987) and Ohana and Kimura (1995) into three characteristic floras, the Ryoseki- and the Tetori-type floras, and the Mixed-type floras com- prising elements of both the Ryoseki- and the Tetori-type floras. According to these authors, the Ryoseki-type floras grew under tropical to subtropical conditions with an annual long arid season, while the Tetori-type floras grew under temperate and moderately humid conditions.
The genus Pseudofrenelopsis belongs to the extinct conifer family Cheirolepidiaceae. Although this family is a dominant group of Mesozoic conifers, its closer affinity remain equivocal. The members of the family have various kinds of shoot morphology ranging from Brachyphyllum- Pagiophyllum-type shoots bearing scale leaves to Frenelop- sis-Pseudofrenelopsis-type cylindrical segmented shoots bearing minute leaves. The single most reliable character of this family is possession of the pollen of the genus Classopollis Pflug (Watson, 1988). Although the plants yield- ing fossil remains attributed to the genus Pseudofrenelopsis were widely distributed during the Early Cretaceous (Ber- riasian-Albian) of North America, Europe, North Africa and Asia, they were apparently restricted to the Cretaceous (Table 1).
The frenelopsids, which include the genus Pseudo- frenelopsis and the closely related genus Frenelopsis, have been used as indicator taxa of tropical to subtropical arid climate (Alvin, 1982). In east Asia the occurrence of the frenelopsids in fossil floras is restricted to the Ryoseki- and the Mixed-type floras. Although Frenelopsis is known from
the Ryoseki-type floras of the Upper Jurassic to Lower Cretaceous in Japan, fossil remains assigned to Pseudo- frenelopsis have not been reported yet. In the present paper, the remains of shoot and associated cuticular fea- tures of Pseudofrenelopsis from Japan are described.
Mikasa City Museum
Katsurazawa Lake Xn |
Figure 1. Map of Hokkaido, Japan showing the location of the Pombetsu Valley.
Ken'ichi Saiki
30
Cheirolepidiaceous conifer from Lower Cretaceous of Hokkaido 31
Material and Methods
Material—A compressed conifer shoot was found in the Pombetsu Valley about 60 km northeast of Sapporo (Figure 1). The specimen was obtained from the mudstone bed of the so-called “Main part of Middle Yezo Group”. The locality is situated between Matsumoto's outcrops Ik 2025 and 2031, from where the Albian ammonite Ammonoceratites yezoensis Yabe has been reported (Matsumoto, 1965, fig. 3).
Methods.—Fossil remains were immersed in Schulze’s solution followed by diluted NaOH. The cuticle was mounted in Eukitt for light microscopy. For SEM observa- tion, cuticles were coated with Pt-Pd in a Hitachi E-1030 ion sputter and photographed with Hitachi S-800.
All specimens used in this study are deposited in the Mikasa City Museum (MCM), Ikushumbets-nishikicho, Mi- kasa, Hokkaido.
Systematic description
Order Coniferales Family Cheirolepidiaceae Takhtajan, 1963 Genus Pseudofrenelopsis Nathorst, 1893
Remarks of the genus.—The diagnosis originally based only on the type species was emended by Watson (1977) after studying specimens of Frenelopsis varians Fontaine, which is now placed in this genus. Recently, Srinivasan (1995) emended the diagnosis of Pseudofrenelopsis based on new morphological characters of Puddledock material. Srinivasan's concept is followed here.
Pseudofrenelopsis glabra sp. nov. Figures 2A-H, 3A-I
Material.—Holotype, MCM-PO30
Horizon.—Main part of the Middle Yezo Group (Albian).
Type locality —Pombetsu Valley, Mikasa, Hokkaido (Figure 1; ca. 4316°31”N, 141°59'20”E). The locality is about 80 m south of Matsumoto’s (1965) outcrop Ik 2031.
Diagnosis.—Segmented shoot bears a simple spiral of leaves, each leaf encircling the stem. Leaf margin having hairs ; outer surface of both abaxial and adaxial leaf cuticle smooth, without trichomes. Internode cuticle well devel- oped. Outer surface of cuticle smooth, nonpapillate. Stomata arranged in longitudinal rows. Stomatal complex consisting of a pair of guard cells and 7-9 subsidiary cells. Guard cells sunken below a ring of subsidiary cells with irregularly oriented apertures. Stomatal pit rounded in sur- face view. Outer surface of subsidiary cells forming a raised
rim bounded by a deep groove around stomatal pit. A well developed cutinized hypodermis of thin-walled cells cover- ing most of the internal surface of the cuticle.
Description.—A single compressed shoot was obtained (Figures 2A, B). The shoot is segmented, bearing a simple spiral of leaves. Each of the leaves encircles the stem. The internode is 6-9 mm long and 4 mm wide (Figures 2A, B). Triangular part of the leaf is up to 1.5 mm high at a node (Figures 2B, C; 3A). The leaf margin has hairs up to 40 um long (Figures 2E ; 3B, C). Outer surface of both abaxial and adaxial leaf cuticle is smooth, without trichomes (Figures 3B- D). The internode cuticle is well developed, about 8 um in total thickness. The cuticle consists of outer periclinal epidermal wall about 3 «m thick, anticlinal wall and thinly cutinized hypodermis (Figure 3E). No dorsiventrality is ob- served (Figure 2F). Stomata are about the same optical density as the rest of cuticle and are arranged in well marked longitudinal rows in 7-9 rows per mm. Each row of stomata is a single stoma wide. 70-100 per mm? in density. (Figures 2F, G; 3F, G). The bands of epidermal cells between the rows of stomata are 20-70 um (1-3 cells) wide, consist of longitudinally arranged epidermal cells. The epidermal cells are elongated rectangular to polygonal in shape, 25-50 um long and 10-25 um wide (Figures 2F,G; 3G). Outer surface of the cuticle is smooth, nonpapillate (Figure 3F).
The stomatal complex is 80-120 um in diameter, consists of a pair of guard cells and 7-9 subsidiary cells (Figure 3G). The guard cells are 40-70 uum long and 10 ~m wide and are sunken below a ring of subsidiary cells. The aperture of the stoma is irregularly oriented (Figure 3G). The stomatal pit is about 30 um in diameter and is rounded in surface view (Figures 3F, H). Outer surface of the subsidiary cells forms a raised rim bounded by a deep groove around stomatal pit. Each of the subsidiary cells has a single papilla projecting into the stomatal pit (Figures 2H ; SF, H, |).
A well developed cutinized hypodermis of thin-walled cells cover most of the internal surface of the cuticle except for the region immediately beneath each stomatal apparatus. The hypodermal cells are rectangular or polygonal under the stomatal zone and are axially elongate rectangular under the nonstomatal zone (Figures 3E, G).
Discussion.—Due to the fragmentary nature of the fossil specimen the arrangement of the branch system of Pseudo- frenelopsis glabra is uncertain. External and cuticular observations of the specimen clearly indicate the absence of a groove or suture separating the basal cushions, as seen in living species of the Cupressaceae.
Although the epidermal cells are clearly visible with light microscopy (Figure 2G), SEM microscopy of the inner surface of cuticle shows only hypodermis and stomatal complexes,
Figure 2. Pseudofrenelopsis glabra sp. nov. (MCM-P030).
holotype showing leaf margins (I).
A: Holotype (MCM-P030). B: Middle region of the
C, D: Opposite sides of the same shoot fragment showing the margin of a single leaf (I). E: Light microscope image of the leaf margin showing short hairs. region showing fold represented by central dark line, and cuticles of both sides of the compressed specimen. of stomata and epidermal cells show no siginificant difference on both sides of the cuticles. of cuticle from the internodal region showing longitudinally arranged stomata, light microscope. of stomata, focused through the stomatal pit showing the papillae.
F: Light microscope image of cuticle from internodal Arrangement G: Light microscope image H: Light microscope image Scale bars=5 mm in A-D; 100 um in E-H.
10} D
Ken’ichi Saiki
Figure 3. SEM micrographs of Pseudofrenelopsis glabra sp. nov. cuticle (MCM-P0O30). A: Triangular free part of leaf. B: Edge of a leaf, showing marginal hairs and outer surface of abaxial leaf cuticle. C: Enlarged photo of 3B showing the short marginal hairs and smooth outer surface of the abaxial (ab) and adaxial (ad) leaf cuticle. D: Surface view of adaxial leaf cuticle (ad) and inner view of cuticle from the internodal region (i). E: Section of cuticle showing cutinized epidermis (c) and hypodermis (h). F: Outer view of cuticle from the internodal region showing mouth of stomatal pit. G: Cuticle from the internodal region showing longitudinally arranged stomatal complexes. Inner view of stomatal complexes showing the guard cells (g), and subsidiary cells (s). H: Outer view of a stoma showing the rounded mouth of the stomatal pit with papillae. 1: Section of stoma showing guard cells (g), and papillae in throat of stoma (p). Scale bars=500 um in A, B; 50 um in C, D, F-H; 10 um in E, I.
Cheirolepidiaceous conifer from Lower Cretaceous of Hokkaido
G66L ‘nouz
2261 ‘uosjeM
G66L ‘NOUZ 6/6 ‘089 pue noyz 8/61 JE 18 UIAIY GGGL ‘UBSEAIULS G661 NOUZ //6l'08S] pue MOUD //6|'08S] pue MOYD 2261 ‘UAIY 2161 ‘UOSJeAA SOOQUSIBJOY edoinz ueder AUS) Bulyd BUIYD Bulyd “291H8UY YON eoruaWwy UHON UOHNGHISIq veigly UEIQ|Y-PIL-IMO] uelqiy-Uedy SN08921219 JBMO] snosde}eID JeEMO7] UeIgqIy-ueisenog ueiqiy-uendy eue: SIudeisirens ae||ided sejjıded UHM- : punol eellided eellIded jnouym UHM- :punol oO} jesıydılla 9ye||O1S eye}|O1S UNM- :punol Jo UUM- :punol sejjided UyM-— :punoi jid yeyewo}s jo LH SII89 8-9 (2-)9-G-+) (2-)9-S 9-S (8-)9-S(-p) (1-)9-S(-P) (6-)e-s(-p) Meipisqns jo JequnNn uw” o'g0L Alaıeı snyeiedde ww 02-08 Wr 29-79Xx 81-05 uw” 001-9°29 ur G6-GG ur G'z6-0+ ww?! 08-09 W77QOL-OL IEJEUOJS jo Jeysweig SMOI ww Jad 6-7 ww Jed 21-11 ww Jed (OL-)6-8 ww Jad (01-)8-/(-9) ww sad (6-)-9(-p) ww Jad 01-9 ww Jod 01-8 Jeyewojs jo Aysusq e}ewols UO} SMOI p819ye9S yum „Usdo, Ul SMOI ‘UO}
SMOI pauyop |jem peziunno |jem euou
wie
Sireu 1noyym ur Op 0} dn sie
ww G} auou WW +
ww g-9
pauyop ||! ARSOU euou
w7/ 002 0} dn wr QOL
sawoyol} ur O’GpL 0} dn surey
WW Q'} SoA
wu 0'2-0'1 wu 67-01
‘aou “ds eıgey6 ‘d
euensioyjeu ‘q SIsuaueysiay ‘qd —
SMOJ PSUIJEP [JOM 9u0U auou
wit G-€
sırey Jnoyym sırey NOUJIM
ww z euou WW ÿ-G'e ww 9-G
SMOJ pauyap |jem euou
ee||ided ete] um
wr/(gZ-)01-9'1(-9) surey
1noyym Ajjeuwlou sirey 1NOyuMm
ww Z auou
WLU g'g-& WLW OL-G'G
sisuazjejep ‘d
SMOJ jeulpnyBuo| euou
jussaud Ajjensn wi! G'2-G
juesaid sirey uw” O8 0} dn sie
WLU GL auou WWW G'/-€ wu LLG
esoyided ‘d
SMOJ peuljep [JOM
paziulynd em surey Buo Alan 0} euou
ur (€
juasaid surey uw” 08 0} dn sırey
WW Z UO} ‚uedo, SOS UI > WLU |
esoweJsao4ed ‘4
PES, ul peueyeos
suolysno
sseq-jes| ,uado,, ul
uw” 08 0} dn
ur” OLL-OS
juasaid suey uw” 09 0} dn surey
WW G'| auou
ww J-¢ wu /1-Gl SUBLIEA ‘d
‘saioads payejaı pue ‘aou ‘ds eiqe{6 sIsdojauaopnesd Jo saorawoydiow antpereduio9 Loge.
jueusBueie |eYEWO}S
sıwlspodAy paziuijing SI89 jewıopıdo uo SIIEU JO SAWOYOH | SSaUMOIU} a|o1n9 apouss}u| jee] JO aoeNs jeixepe uo siley JO SAWOYOU | ulBuew yea yes] 99 jo u}Bus] WNWIXeIN def 10 aunyns Jo aouasald UIPIM SpouIsqu] u}Bus| apousa}u|
saloadg/ SiJoBIeUN
34 Ken'ichi Saiki
because the epidermal cells are covered by cutinized hypodermis (Figure 3G).
Comparison.—Although the present specimen is fragmen- tary, both external and cuticular features of the specimen correspond well with the diagnosis of Pseudofrenelopsis Nathorst emended by Srinivasan (1995) in its segmented shoot bearing a simple spiral of leaves, smooth cylindrical internode, and guard cells sunken below ring of subsidiary cells.
Among the species of Pseudofrenelopsis previously de- scribed, the European P. varians (Fontaine) Watson and American P. parceramosa (Fontaine) Watson differ from P. glabra in possessing an extremely thick cuticle and having trichomes on the adaxial surface of the leaf cuticle (Watson, 1977).
Although various species of Pseudofrenelopsis have been reported from China, most are provided with brief descrip- tions (Zhou, 1995). Recently, Zhou (1995) reexamined and combined the Chinese Pseudofrenelopsis into the following three species : P. papillosa (Chow et Tsao) Zhou, P. dalatzen- sis (Chow et Tsao) Zhou, and P. heishanensis Zhou (Table 1). Pseudofrenelopsis glabra is similar to these Chinese species in possessing a thinner internode cuticle than the European and American species. Pseudofrenelopsis dalatzensis and P. heishanensis can be distinguished from P. glabra by the stellate rim of the stomatal pit and absence of hairs on their leaf margins.
The shape of the cells, smooth periclinal walls, and thin anticlinal walls of the hypodermis of Pseudofrenelopsis glabra (Figures 3G, E) are very similar to the “epidermal cells” of Pseudofrenelopsis heishanensis described by Zhou (1995). However, detailed light and SEM microscopy of P. hei- shanensis is required prior to meaningful comparison of P. heishanensis and P. glabra.
Pseudofrenelopsis papillosa, redescribed in detail by Zhou (1995), possesses the most similar cuticle to that of P. glabra in having hairs on the margin of the leaf, round stomatal pits, and a thin cuticle. These resemblances may indicate a close phylogenetic relationship between these two species. Pseudofrenelopsis glabra is however, clearly distinguished from P. papillosa by a smaller number of subsidiary cells and absence of trichomes on the outer surface of the leaf adaxial cuticle.
Paleophytogeography.—Since Kimura (1961,1975) has divided the Late Jurassic-Early Cretaceous floras of Japan and its adjacent areas into the Ryoseki-type and the Tetori type floras, this paleophytogeographical distinction has been extended to East Asia with some modification, and the Mixed-type flora that consist predominantly of the Ryoseki type element and subordinate Tetori-type element was added (Kimura, 1980, 1987 ; Kimura and Ohana, 1992 ; Cao, 1994 ; Ohana and Kimura, 1995).
Although the Mesozoic flora of Hokkaido is famous for its well preserved permineralized materials, the stratigraphic range of these materials is restricted to the Upper Cretaceous (Nishida, 1991). So far, the absence of Jurassic and Lower Cretaceous fossil plants from Hokkaido had prevented comparison of the Early Cretaceous flora of Hokkaido with the Ryoseki- and the Tetori-type floras.
Recently, Saiki (1997) described Frenelopsis pombetsuensis, from the Lower Cretaceous Yezo Group (Albian) of Hokkaido. The family Cheirolepidiaceae is a diagnostic taxon of the Ryoseki-type element reported only from the Ryoseki- and the Mixed-type floras (Ohana and Kimura, 1995). Thus, Pseudofrenelopsis glabra is the second evidence of the presence of Ryoseki-type element from Hokkaido.
Ohana and Kimura (1995) estimated that the Ryoseki-type floras flourished under tropical or subtropical conditions with an annual long arid season. Their idea is consistent with the thermophilous nature of frenelopsids proposed by Alvin (1982) based on the distribution of frenelopsids of the world and their possession of a thick cuticle. However, the two frenelopsids species from Hokkaido lack two of the xeromor- phic features observed in many other frenelopsids, namely, a thick cuticle and trichomes on the internode surface. The cuticle thickness of eight species listed in Alvin (1982) are 8- 110 um thick in their periclinal wall rather than 3 um and 3- 4 um thick as in Frenelopsis pombetsuensis and Pseudo- frenelopsis glabra respectively. The cuticular features of Frenelopsis pombetsuensis and Pseudofrenelopsis glabra may reflect the rather humid condition inferred for the Albian of Pombetsu, rather than the xeric conditions from other regions of the world where frenelopsids were distributed (Alvin, 1982). This assumption is consistent with recent palynological data indicating that the group inhabited a variety of ecological niches (Watson, 1988).
Acknowledgments
The author thanks T. Kimura, director of the Institute of Natural History, Tokyo, for his critical reading the manuscript and his helpful suggestions ; M. Futakami, |. Obata, M. Ma- tsukawa, Y. Taketani, M. Ito and H. Nagata for their encour- agement and helpful suggestions. Thanks are also extended to Ben A. LePage, University of Pennsylvania, for his kindness in critically reading the manuscript.
This study was supported by the Ishikari River Local Head Office, Hokkaido Development Bureau.
References cited
Alvin, K.L., 1977 : The conifer Frenelopsis and Manica in the Cretaceous of Portugal. Palaeontology, vol. 20, p. 387- 404.
Alvin, K.L., 1982 : Cheirolepidiaceae : Biology, structure and paleoecology, Review of Palaeobotany and Palynology, vol. 37, p. 71-98.
Alvin, K.L., Spicer, R.A. and Watson, J., 1978: A Classopol- lis-containing male cone associated with Pseudo- frenelopsis. Palaeontology, vol. 21, p. 847-856.
Cao, Z., 1994: Early Cretaceous floras in Circum-Pacific region of China. Cretaceous Research, vol. 15, p. 317- 332.
Chow, T.Y. and Tsao, C.Y. 1977: On eight new species of conifers from the Cretaceous of East China with refer- ence to their taxonomic positiion and phylogenetic relationship. Acta Palaeontologica Sinica, vol. 16, no. 2, p. 165-181. (in Chinese with English summary)
Kimura, T., 1961: Mesozoic plants from the Itoshiro Sub-
Cheirolepidiaceous conifer from Lower Cretaceous of Hokkaido
group, the Tetori Group, Central Honshu, Japan. part 2. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 41, p. 21-32.
Kimura, T., 1975: Notes on the Early Cretaceous floras of Japan. Bulletin of the Tokyo Gakugei University, Series 4, vol. 27, p. 217-257.
Kimura, T., 1980: The present status of the Mesozoic land floras of Japan. Professor Saburo Kanno Memorial Volume, p. 379-413. Tsukuba University.
Kimura, T., 1987: Geographical distribution of Palaeozoic and Mesozoic plants in East and Southeast Asia. In, Taira, A. and Tashiro, M. eds., Historical Biogeography and Plate Tectonic Evolution of Japan and Eastern Asia, p. 135-200. Terrapub, Tokyo.
Kimura, T. and Ohana, T., 1992: Cretaceous palaeobotany and phytogeography in Eastern Eurasia. Palaeontological Society of Korea, Special Publication, no. 1, p. 27-34.
Matsumoto, T., 1965: A monograph of the Collignoni- ceratidae from Hokkaido, part1. Memoirs of the Fac- ulty of Science, Kyushu University, Series D, no. 16, p. 1-80.
Nishida, H., 1991: Diversity and significance of Late Cretaceous permineralized plant remains from Hok- kaido, Japan. Botanical Magazine Tokyo, vol. 104, p. 253-273.
Ohana, T. and Kimura, T., 1995: Late Mesozoic phytoge- ography in eastern Eurasia, with special reference to the
ww
in
origin of angiosperms in time and site. Proceedings of 15th International Symposium of Kyungpook National University, p. 293-328.
Saiki, K., 1997 : Frenelopsis pombetsuensis : a new cheiro- lepidiaceous conifer from the Lower Cretaceous (Albian) of Hokkaido, Japan. Paleontological Research, vol. 1, no. 2, p. 126-131.
Srinivasan, V., 1995: Conifers from the Puddledock locality (Potomac Group, Early Cretaceous) in eastern North America. Review of Palaeobotany and Palynology, vol. 89, p. 257-286.
Watson, J., 1977: Some lower Cretaceous conifers of the Cheirolepidiaceae from the U.S.A. and England. Palaeontology, vol. 19, p. 715-749.
Watson, J., 1988: The Cheirolepidiaceae. In, Beck, C.B. ed., Origin and Evolution of Gymnosperms, p. 382-447. Columbia University Press, New York.
Zhou, Z., 1995: On some Cretaceous pseudofrenelopsids with a brief review of cheirolepidiaceous conifers in China. Review of Palaeobotany and Palynology, vol. 84, p. 419-438.
Zhou, Z. and Cao, Z., 1979: Some Cretaceous conifers from southern China and their stratigraphical significances. In, Institute of Vertebrate Palaeontology and Palaeoanthropology, and Nanjing Institute of Geology and Palaeontology, Academia Sinica eds, Mesozoic and Cenozoic Red Beds of Southern China, p. 218-222. Science Press, Beijing.
Ikushumbets-nishikicho #4 5/$#H), Mikasa =*, Pombetsu #1]
Paleontological Research, vol. 3, no. 1, pp. 36-40, 3 Figs., April 30, 1999
© by the Palaeontological Society of Japan
The first record of Mesoturrilites (Ammonoidea) from Hokkaido (Studies of the Cretaceous ammonites from Hokkaido and Sakhalin — LXXxXill)
TATSURO MATSUMOTO and AKITOSHI INOMA
c/o Faculty of Science, Kyushu University, Fukuoka 812-8581, Japan
6-29-19 Daida, Setagaya, Tokyo 155-0033, Japan
Received September 3 1998 ; Revised manuscript accepted 22 November 1998
Abstract.
Several small specimens collected years ago by A.l. from a locality in the Soeushinai area of Hokkaido are now identified as Mesoturrilites boerssumensis (Schlüter, 1876).
The species has been
reported from the Lower Cenomanian of western and central Europe and western Asia. Our material is also referred to the Lower Cenomanian on the biostratigraphic evidence. This may be the first record of
Mesoturrilites in the northern Pacific region.
Key words : Cenomanian, geographic distribution, Hokkaido, Mesoturrilites, Pacific region, Turrilitidae
Introduction
A number of species belonging to Mariella, Pseud- helicoceras, Ostlingoceras, Neostlingoceras, Turrilites and Hypoturrilites of the family Turrilitidae [Ammonoidea] show worldwide distribution. Some of them occur fairly commonly in the Upper Albian and Cenomanian strata in Japan, although many of them are waiting for complete descriptions. In this paper a species of Mesoturrilites from Hokkaido is described.
Stratigraphic setting
The area concerned, called “Soeushinai’, was geologically mapped by Hashimoto et al. (1965) and has been recently reinvestigated by Nishida et al. (1996, 1997, 1998a, b). According to these authors, a thick series of strata called the Middle Yezo Subgroup of late Albian through Turonian age, is extensively exposed in this area. The subgroup is sub- divided into Members My1 to My8 in a revised scheme of Nishida et al. (1996, fig. 10). The specimens described below were contained in a transported nodule obtained by A.l. in 1959. That nodule was collected in the upper reaches of the Sanjussen-zawa, a tributary of the River Uryu. The nodule is interpreted as a derivative from Member Mys. This member consists primarily of mudstones which have sometimes fine-grained sands or sandy laminae and contain commonly calcareous nodules. Ammonoids occur fairly abundantly in Member My3 together with inoceramids and other mollusks. Some of them were described by Matsu- moto and Inoma (1975, 1991) and Inoma (1980) and also amply listed by Nishida et a/. (1996, 1997). The fauna forms the Assemblage Zone of Graysonites adkinsi, indicating the lower part of the Lower Cenomanian.
The overlying Member My4 is composed of ill-sorted conglomerates in some parts and predominant sandstones with some mudstones and conglomerates in other parts. It is poor in fossils. The succeeding Member My5 consists mainly of mudstones which contain numerous inoceramids with some associated ammonoids, representing the rest of the Cenomanian.
The Inoma’s locality, numbered Al-72803, is concisely indicated in a map by Matsumoto and Inoma (1975, fig. 2) and more precisely in Figure1. A fossiliferous nodule contains small specimens of Algericeras proratum (Coquand) and Euhystrichoceras cf. nicaisei (Coquand) besides those of Mesoturrilites described herein. At another locality, R7239p, about 70m NEE of AI-72803, Y. Kawashita and N. Egashira obtained another ammonite which is identified by T.M. with Gabbioceras yezoense Shigeta. The three ammonite species indicate an early Cenomanian age and the mud- stones around the above localities are referable to Member My3. Incidentally, as a result of Y. Inoue’s examination of foraminifera, the strata exposed in the source area of the Sanjussen-zawa, including localities R7238, R7231, R7232, R7233 and R7234, have proved to be Member My5 (middle to upper part of the Cenomanian) (for details see Nishida et al., 1998a). The two members My3 and My5 are probably in fault contact (Figure 1).
Repository
The specimens described below have numbers with the prefix TKD, which is the abbreviation of “Tokyo Kyoiku Daigaku [Tokyo University of Education|”, where A.l. was a student. Since this university was closed, As collection of ammonoids from the Soeushinai area under TKD numbers has been temporarily stored in the Department of Geology,
Mesoturrilites from Hokkaido 37
i # My3
ara AI-72803 i VER) re
’ FH 45° S -
100m S|
Figure 1. Route map along the upper course of the Sanjussen-zawa, cited from Nishida et al., 1998a by permission. Inset is a map of Hokkaido in which the Soeushinai area is indicated by an arrow. Small solid circle : megafossil (in situ), cross : ditto (trantported nodule), solid square : microfossil sample, empty square: rock sample, tiny empty circle: conglomerate, dots: sandstone, grass: no outcrop, blank along the route: mudstone, broken line: fault (inferred), chain : boundary of lithostratigraphic units (members). All the locality
numbers should have prefix R, except for Al-72803.
Kyushu University in Fukuoka, but they should be eventually returned to the Deparrtment of Geosciences, Tsukuba University, Tsukuba, 305-0006 Japan, which is the new guise of the TKD.
Morphological terms
For the morphological terms used to describe the turrilitid ammonoids, we follow those of Wright and Kennedy (1996). Setting the apex of the turrical shell at the top, the terms upper and lower or adapical and adapertural | =adoral| are defined and the rows of tubercles or ribs on the face of each whorl are described in descending order as the first, the second and so on.
Palaeontological description
Order Ammonoidea Zittel, 1884 Suborder Ancyloceratina, Wiedmann, 1966 Family Turrilitidae Gill, 1871 Genus Mesoturrilites Breistroffer, 1953
Type species.—Turrilites aumalensis Coquand (1862, p. 323, pl. 35, fig. 5), by original designation of Breistroffer (1953, p. 1351).
Diagnosis.— Turrilitid ammonoid with four rows of tubercles
or ribs ; the upper row made up of ribs or rounded tubercles, the second and the third rows spirally elongated tubercles on semicontinuous, narrow ridges separated by a groove ; the fourth row of weak tubercles at the outer edge of the lower whorl surface ; faint ribs may be elongated from the fourth row of tubercles toward a narrow umbilicus.
Remarks.—The lectotype and paralectotypes of the type species have been photographically illustrated by Wright and Kennedy (1996, text-fig. 146A-G).
At present five species are known in Mesoturrilites. The distinction between species is based on the size of the apical angle, mode of ribbing and/or tuberculation, whorl shape etc. Atabekian (1985, p.75) referred Turrilites col- canapi Boule, Lemoine and Thevenin, 1907 to Mesoturrilites. However, we agree with Spath (1937, p. 523) and also Wright and Kennedy (1996, p. 323) on their assignment of T. col- canapi to Ostlingoceras.
The phylogenetic origin of Mesoturrilites is uncertain, but it can likely be sought in some form of Mariella. A sulcate variety of Mariella oehlerti (Pervinquiere) may be a candidate, as Pervinquiére (1910, p.55, pl.5, fig.17) has already mentioned its affinity to Mesoturrilites aumalensis. Wright and Kennedy (1996, p. 346) have suggested Mariella bicar- inata (Kner) as another allied form.
The type species and some other species of Mesoturrilites have been recorded from the Lower Cenomanian of both ine
38 Tatsuro Matsumoto and Akitoshi Inoma
Tethys and Boreal provinces.
Mesoturrilites boerssumensis (Schlüter, 1876) Figures 2 and 3
Turrilites börssumensis Schlüter, 1876, p. 129, pl. 38, figs, 6, 7.
Turrilites (Mesoturrilites) boerssumensis Schlüter. Immel, 1979, p. 636, pl. 4, fig. 4; Hiss, 1982, p. 190, pl. 7, figs. 11, 12 ; Atabekian, 1985, p. 75, pl. 27, figs. 3, 4.
Mesoturrilites boerssumensis (Schlüter). Wright and Ken-
Figure 2. Mesoturrilites boerssumensis (Schlüter). 1. TKD30089A, two lateral (a,b) and basal (c) views. 2. TKD30089B, two lateral (a, b) views. 3. TKD30089C, two lateral (a, b) views. All x 2.
Figure 3. Mesoturrilites boerssumensis (Schlüter). Suture of TKD30089C, showing relative position of the ribs and tubercles by dotted lines. Approximately x 8.
nedy, 1996, p. 347, pl. 105, figs. 4, 20 (with full synonymy) ; Lehmann, 1998, p. 36, pl. 5, fig. 5.
Lectotype.—The original of Schlüter, 1876, pl. 38, figs. 6, 7, from the Cenomanian Planer near Borssum, Germany, by subsequent designation of Juignet and Kennedy (1976, p. 67).
Material—Four specimens, TKD30089A (Figure 2-1), TKD30089B (Figure 2-2), TKD30089C (Figure 2-3 ; Figure 3) and TKD30089D (unillustrated). They were removed by Al. from a transported nodule at locality Al-72803 in the upper reaches of the Sanjussen-zawa of the Soeushinai area, northwestern Hokkaido (Figure 1).
Description.—TKD30089A consists of four whorls with estimated tower height 28.8 mm, apical angle about 19°, height and diameter of the preserved last whorl 5.4 mm and 11.2mm respectively. Other three are smaller than the above and incomplete, representing younger stages.
The main part of the exposed whorl face is flattened or slightly convex and the interwhorl junction is feebly im- pressed. The ornament is typical for Mesoturrilites. On the upper half of the exposed whorl face there are slightly prorsiradiate ribs of moderate breadth and density (Figure 2- 1). They number 21 per whorl at diameter of 11mm in TKD30089A and 16 or 15 at diameter 7 or 6mm in TKD30089B or TKD30089C. At about the middle of the whorl face the ribs terminate at tubercles of the first row. These tubercles are subrounded at the base and pointed at the top, as far as the test is well preserved. The tubercles of the second row are narrowly clavate and rest on a blunt spiral ridge. They correspond in number to the tubercles of the first row but are displaced adaperturally. The space between the first and the second rows of tubercles forms a smooth band and may appear to be slightly concave on the internal mould. The tubercles of the third row are narrowly clavate and aligned along the narrow ridge along the lower seam of the whorl. The narrow interspace between the second and the third rows of clavi is distinctly sulcate. As is shown by TKD30089A, the spiral groove between the second and third rows of semi-continuous ridges is immedi- ately above the interwhorl junction in early growth stages, but later it is covered by the shell layer of the succeeding whorl (Figure 2-1). The tubercles of the fourth row are close to those of the third row, but they are aligned on the outer margin of the lower whorl face. Weak ribs run from them toward a narrow umbilicus, showing slightly rursiradiate Curvature (Figure 2-1c).
A septal suture of a young stage is exposed on the whorl face of TKD30089C. As is shown in Figure 3, the saddle E/L is much broader than L/U. The relative disposition of the tubercles with respect to the sutural elements in shown is the same figure.
Discussion.—The specimens described above are un- doubtedly identified with Mesoturrilites boerssumensis (Schluter, 1876), redefined by Wright and Kennedy (1996, p. 347). In view of the variation of the rib density with growth and between individuals, the 17 ribs to a whorl specified in Schlüter's (1876, p. 636) description may not be incorrect. Hiss (1982, p.190) counted 20 ribs on an example from Westphalia. Wright and Kennedy (1996, p. 347) estimated
Mesoturrilites from Hokkaido 39
as many as 24-26 ribs per whorl in a specimen from England, but 9 or 10 ribs are shown on its illustrated face of slightly less than half a whorl (op. cit., pl. 105, fig. 4) as in our TKD30089A (Figure 2-1).
Hitherto described specimens, comprising those from Hokkaido, are more or less small, with diameters of the preserved last whorl less than 25mm. The small size may be, therefore, a diagnostic character of this species. How- ever, further investigation is required to search out a com- pletely preserved specimen with a rostrate peristome and also to examine the problem of dimorphism.
Occurrence.—As for material. M. boerssumensis has been reported from the Lower Cenomanian of Germany (Westphalia and Bavaria), England, Poland and southern Turkmenistan (see synonymy list). Now its distribution is extended to Hokkaido. This may be the first record of Mesoturrilites from the northern Pacific region.
Acknowledgements
We are much indebted to C.W. Wright and W.J. Kennedy for their kind help during this study. Thanks are extended to Tamio Nishida, Seiichi Toshimitsu and Kazuko Mori for practical support.
References cited
Atabekian, A.A., 1985: Turrilitids of the late Albian and Cenomanian of the southern part of the USSR. Acad- emy of Sciences of the USSR, Ministry of Geology of the USSR. Interdepartmental Stratigraphic Committee of the USSR, Transactions, vol. 14, p. 1-112, pls. 1-34. (in Russian)
Boule, M., Lemoine, P. and Thevenin, A., 1907 : Cepha- lopode crétacés des environs de Diego-Suarez. An- nales de Paléontologie, vol. 2, p. 1-56, pls. 1-8.
Breistroffer, M., 1953: L’evolution des Turrilitides albiens et cenomaniens. Comptes Rendus Hebdomadaires des Sciences de l'Académie des Sciences, vol. 237, p. 1349-1351.
Coquand, H., 1862: Géologie et paléontologie de la region sud de la Province de Constantine. Mémoires de la Société d’Emulation de la Provence, Marseille, vol. 2, p. 1-320, 321-341 (supplement), pls. 1-35.
Hashimoto, W., Nagao, S. and Kanno, S., 1965 Soeushinai. Explanatory Text of the Geological Map of Japan, scale 1: 50,000, p.1-92, quadrangle map. Geological Sur- vey of Hokkaido. (in Japanese with English abstract)
Hiss, M., 1982 : Ammoniten des Cenomans von Südrand der westfälischen Kreide zwischen Unna und Möhnesee. Paläontologische Zeitschrift, vol. 56, p. 177-208, pls. 7- 9.
Immel, H., 1979: Cenoman-Ammoniten aus den Losen- steiner Schichten der Bayerischen-Alpen. In, Wied- mann, |. ed., Aspekte der Kreide Europas. International Union of Geological Sciences, Ser. A, vol. 6, p. 607-644, 4 pls.
Inoma, A., 1980: Mid-Cretaceous ammonites from the Shumarinai-Soeushinai area, Hokkaido. Part2. Pro- fessor Saburo Kanno Memorial Volume, Tsukuba, p. 167-183, pls. 21-22.
Juignet, P. and Kennedy, W.J., 1976: Faunes d’ammonites et biostratigraphie comparee du Cenomanien du nord ouest de la France (Normandie) et du sud de l’Angleter- re. Bulletin trimestriel, Société Geologique Normandie Amis Muséum Havre, vol. 63, p. 1-193, pls. 1-34.
Lehmann, J., 1998: Systematic palaeontology of the ammo- nites of the Cenomanian-Lower Turonian (Upper Cretaceous) of northern Westphalia, north Germany. Tubingen Geowissenschaftliche Arbeiten (TGA), Reihe A, vol. 37, p. 1-58, pls. 1-5.
Matsumoto, T. and Inoma, A., 1975 : Mid-Cretaceous ammo- nites from the Shumarinai-Soeushinai area, Hokkaido. Part |. Memoirs of the Faculty of Science, Kyushu University, Series D, Geology, vol. 23, no. 2, p. 263-293, pls. 38-42.
Matsumoto, T. and Inoma, A., 1991: The mid-Cretaceous ammonites of the family Kossmaticeratidae from Japan. Part 3. Descriptions of the species from the Shuma- rinai-Soeushinai area of Hokkaido. Palaeontological Society of Japan, Special Papers, no. 33, p. 103-122, pls. 25-30.
Nishida, T., Matsumoto, T. and Inoue, Y., 1998a: For- aminifera from the Cretaceous System in the Shuma- rinai Valley of Hokkaido. Journal of the Faculoy of Culture and Education, Saga University, vol. 3, no.1, p. 301-331. (in Japanese with English abstract)
Nishida, T., Matsumoto, T., Kawashita, Y., Egashira, N., Aizawa, J. and Ikuji, Y., 1997: Biostratigraphy of the middle part of the Cretaceous Yezo Group in the Soeushinai area of Hokkaido—with special reference to the transitional 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)
Nishida, T., Matsumoto, T., Kawashita, Y., Egashira, N. and Aizawa, J., 1998b: Characteristics of the Cretaceous stratigraphy in the Shumarinai Valley of Hokkaido. Journal of the Faculty of Culture and Education, Saga University, vol.1, no. 2, p. 143-181. (in Japanese with English abstract)
Nishida, T., Matsumoto, T., Yokoi, K., Kawashita, Y., Kyuma, Y., Egashira, N., Aizawa, J., Maiya, S., Ikuji, Y. and Yao, A., 1996: Biostratigraphy of the Cretaceous Middle Yezo Group in the Soeushinai area of Hokkaido—with special reference to the transitional part from Lower to Upper Cretaceous—. Journal of the Faculty of Educa- tion, Saga University, vol.44, no.1, p.65-149. (in Japanese with English abstract)
Pervinquière, L., 1910: Sur quelques ammonites du Crétacé algérien. Mémoires de la Société Geologique de France, Paléontologie 17, memoir 42, p. 1-86, pls. 1-7.
Schlüter, C., 1876: Cephalopoden der oberen deutschen Kreide. Palaeontographica, vol. 24, p. 121-264, pls. 36- 55.
Spath, L.F., 1937 : A monograph of the Ammonoidea of the Gault, part 12. Monograph of the Palaeontographical Society, London, p. 49-540, pls. 57-58.
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. 95 124.
40
Tatsuro Matsumoto and Akitoshi Inoma
Hokkaido 4b#i8, Sanjussen-zawa =-+-# Ri, Shumarinai K##N, Soeushinai EN, Uryu N, Yezo thas
Paleontological Research, vol. 3, no. 1, pp. 41-48, 5 Figs., April 30, 1999
© by the Palaeontological Society of Japan
Early Silurian actinocerid and orthocerid cephalopods from the Kerman area, East-Central Iran
SHUJI NIKO’, YOSHITAKA KAKUWA’, DAISUKE WATANABE’ and RYO MATSUMOTO’
‘Department of Environmental Studies, Faculty of Integrated Arts and Sciences,
Hiroshima University, Higashihiroshima 739-8521, Japan
"Department of Earth Science and Astronomy, College of Arts and Sciences,
University of Tokyo, Komaba 153-0041, Japan
“Geological Institute, University of Tokyo, Hongo 113-0033, Japan
Received 23 September 1998 ; Revised manuscript accepted 22 February 1999
Abstract. Six species of uncoiled cephalopod, including the actinocerids Actinoceratidae, gen. and sp. indet., Armenoceras banestanense sp. nov., A. sp., Elrodoceras sp. and Huroniella iranica sp. nov., and an orthocerid Proteoceratidae ?, gen. and sp. indet., are present in collections made recently from an unnamed formation near Banestan village in the Kerman area of southern East-Central Iran. The cephalopod fauna contains forms closely related with those from Laurentia, and is considered to be of Early Silurian age. This discovery reveals that the geologic age of these cephalopod-bearing horizons should be revised from a vague late Ordovician or early Silurian one. These horizons are correlative with the Niur Formation in the Shirgesht area of northern East-Central Iran.
Key words: Actinocerida, cephalopods, Early Silurian, Iran, Orthocerida
Introduction and geologic setting
During the course of field work in February, 1996, several uncoiled cephalopods were discovered by two of us (Y.K. and D.W.) at three localities near Banestan village in the Kerman area of southern East-Central Iran (Figure 1). The purpose of this paper is to document the fauna and to discuss its implications. The specimens are deposited in the University Museum of the University of Tokyo (UMUT).
Until its separation and northward drifting at or near the Permian-Triassic boundary, the Iran terrane belonged to the Gondwana continent, and the Kerman area was part of a carbonate platform around the margin of Gondwana (e.g., Lensch et al., 1984). The geology of the Kerman area has been described by Huckriede et al. (1962), Zohrenbakhsh and Vahdati Daneshmand (1992) and Richards et al. (1994). These investigatiors discerned three units in the Lower to Middle Paleozoic strata: Upper Cambrian to Lower Or- dovician carbonates of the Mila Formation, the Arenig (upper Lower Ordovician) graptolite shale of the Katkoyeh Forma- tion, and an unnamed formation probably ranging from Upper Ordovician to Middle Devonian that mainly consists of clastics with subordinate carbonates. The cephalopods described herein occur in argillaceous and/or bioclastic limestone of the unnamed formation (Figure 2). The cephalopod-bearing horizons have been described as “orthoceras limestone” by Huckriede et al. (1962), and regard-
ed as being of late Ordovician or early Silurian age. How- ever, the exact biostratigraphic range of the cephalopod- bearing horizons has so far been a matter of debate.
Detailed analysis of morphologic features of the present cephalopods resulted in the identification of five Early Silurian actinocerid and one orthocerid species that provide insights into the precise age and paleobiogeographic affin- ities of the fauna. This is the first modern taxonomic treat- ment of Silurian cephalopods from the Iran terrane.
Systematic paleontology
Subclass Actinoceratoidea Teichert, 1933 Order Actinocerida Teichert, 1933 Family Actinoceratidae Saemann, 1853
Genus and species indeterminate
Figures 3-7, 5-5, 6
Discussion.—A single incomplete specimen of a gently cyrtoconic (?) phragmocone is assigned to the Actinocer- atidae, genus and species indeterminate, based on its rela- tively long and normal cyrtochoanitic septal necks and the high ratio (at least 3.2) of maximum diameter/length of its siphuncular segments.
The restricted development of the annulosiphonate
42 Shuji Niko et al.
=
N
\ \ \ 2 ~ by) © ise)
Figure 1. Index map of fossil localities (1-3) in the Ker- man area (Small arrow in inset), southern East-Central Iran.
deposits on the ventral siphuncular wall and the straight radial canals projecting to the vicinity of brims are an unusual diagnosis for the family and indicate a possibility that the species represents a new genus. Unfortunately the ventral shell is not preserved in the only specimen available. Until additional material is found, the present material is consid- ered too poor to justify naming it to the generic level.
Material and occurrence.—UMUT PM 27332, 72 mm in length, from locality 3.
Family Armenoceratidae Troedsson, 1926 Genus Armenoceras Foerste, 1924a
Type species.—Actinoceras hearsti Parks, 1913.
shale & siltstone
[= © Do Oosr0 = conglomerate E Di 5 == =
limestone T ® E 2 dolostone € 3
pillow lava & volcanic breccia
Inne ale | LI Tun | [hi]
Katkoyeh Formation
If | ; el is à 0 [0]
al
D le Al . oll: |
200m
(part) Oo
Formation
Mila
Figure 2. Generalized stratigraphic section of the Lower to Middle Paleozoic rocks near Banestan village in the Ker- man area. Stratigraphic horizons of each locality are indicat- ed.
Armenoceras banestanense sp. nov. Figures 3-1—6
Diagnosis.— Armenoceras with smaller ratio of maximum siphuncular diameter to shell diameter (approximately 0.3- 0.4), very narrow adnation areas in dorsal siphuncular wall ; cameral deposits well developed ; central canal situated on dorsal margin.
Description.—Orthoconic shells with circular cross sec- tions, moderate shell expansion for the genus, lacking
Figure 3. 1-6. Armenoceras banestanense sp. nov., 1-4,6: holotype, UMUT PM 27328, 1, dorsoventral thin section, venter on left, x2, 2, dorsoventral thin section, showing details of ventral wall of siphuncle, 14, 3, dorsoventral thin section, showing details of dorsal wall of siphuncle, note very narrow adnation area, 14, 4, dorsoventral thin section, showing details of ventral shell, x5, 6, transverse thin section of adoral end, venter down, x2, 5: paratype, UMUT PM 27327, weathered surface of dorsal side, coated with ammonium chloride, x2. 7. Actinoceratidae, gen. and sp. indet.,
UMUT PM 27332, dorsoventral thin section, venter on right,
x 2.
Early Silurian cephalopods from Iran
44
conspicuous surface ornamentation ; adoral end of imper- fect phragmocone of holotype attains approximately 25 mm (slightly deformed) in diameter. Septa closely spaced, moderately shallow; siphuncle large, ratio of maximum siphuncular diameter to shell diameter is small for genus, approximately 0.3-0.4, submarginal in position ; septal necks very short, 0.15-0.21 mm in length, strongly recurved cyrto- choanitic ; brims short for genus, 0.44 mm in well preserved dorsal brim of holotype, in contact with apical surface of septa; diameter of septal foramen 5.9-8.9 mm in holotype ; connecting rings broadly expanded ; adnation areas moder- ate to relatively narrow (their length in dorsoventral section approximately 0.9 mm) in ventral siphuncular wall, and very narrow (do. approximately 0.3 mm) in dorsal siphuncular wall ; maximum diameter/length ratio of siphuncular segments 3.5-4.0. Cameral deposits well developed, episeptal-mural and forming circumsiphuncular ridges, additional hyposeptal deposits recognized in ventral side of camerae; ventral endosiphuncular deposits fusing to form thick lining on siphuncular wall, differentiated into outer annuli and inner lining deposits ; profile of outer annuli laterally elongated elliptical in longitudinal section; development of endosi- phuncular deposits on dorsal siphuncular wall weak, sepa- rated annuli with semicircular profile in longitudinal section. Central canal situated on dorsal margin, branching off narrow radial canals, of which distal parts are curved adorally ; perispatia small, situated near adoral end of each connecting ring.
Discussion.—Armenoceras banestanense sp. nov. is most similar to A. hearsti (Parks, 1913 ; 1915, pl. 6, fig. 5; Foerste, 1924a, pl. 13, fig. 4) which has a siphuncular position and a form ratio of the siphuncular segments like the new species. Armenoceras hearsti was reported from “Limestone Rapids” on the Severn River, Ontario, Canada, and derived from the Ekwan River or Attawapiskat Formation of late Llandovery (Early Silurian) age (Jin et al., 1993). However the former is distinguishable from the latter by its smaller siphuncle (ratio of maximum siphuncular diameter to shell diameter approxi- mately 0.45 in A. hearsti versus 0.3-0.4 in A. banestanense), its somewhat weaker inflation of the connecting rings with the narrower adnation area, and the marginal position of its central canal.
The brims of Armenoceras banestanense and the cooc- curring A. sp. (this report) are frequently missing or obscured by diagenesis, thus they are apt to be incorrectly described as “achoanitic”.
Material and occurrence.—Holotype, UMUT PM 27328, an incomplete phragmocone, 51 mm in length ; paratype, UMUT PM 27327, an incomplete phragmocone, 42 mm in length. Both from locality 3.
Etymology.—The specific name is derived from the village
Shuji Niko et al.
named Banestan near the type locality.
Armenoceras sp. Figures 4-5,7,8
Description.—Orthoconic shells with gradual shell expan- sion, shell diameter reaches 20 mm at adoral end of largest specimen (UMUT PM 27329). Siphuncle subcentral in position, consisting of strongly recurved cyrtochoanitic septal necks and expanded connecting rings with relatively wide adnation area; brims in contact with septa; maximum diameter/length ratio of siphuncular segments approximately 2.5. Cameral deposits episeptal-mural and hyposeptal ; endosiphuncular deposits of annuli have elliptical profile in longitudinal section. Nearly straight radial canals connect with prespatia in apical shell.
Discussion.—This species is easily distinguished from Armenoceras banestanense sp. nov. by its subcentral siphun- cular position and the smaller form ratio of the siphuncular segments.
Material and occurrence.—Two incomplete phragmocones, UMUT PM 27329, 62 mm in length, and 27330, 61 mm in length, from locality 3.
Genus Elrodoceras Foerste, 1924b
Type species.—Cyrtoceras indianense Miller, 1892.
Elrodoceras sp. Figures 5-1—3
Description.—Siphuncle gently curved (?) and large, attains at least 15.5 mm in maximum diameter, with relatively low ratio of maximum diameter/length in siphuncular segment for armenoceratids, at approximately 2.5-2.7 ; siphuncular posi- tion submarginal (?). Septal necks bend adapically, thus septal foramen is funnel-shaped ; brims strongly recurved cyrtochoanitic, in contact with septa; connecting rings form very wide adnation area and moderately inflated free parts. Cameral deposits episeptal-mural and hyposeptal ; endosi- phuncular deposits well developed, annulosiphonate. Cen- tral canal surrounded by lining deposits that are darker in color than annulosiphonate deposits ; radial canal arched with branches.
Discussion.—Except for the deposit-filled siphuncle, the shell of this only known specimen is broken and weathered on the dorsum, thus accurate shell shape and siphuncular position can not be determined in the present material. Nevertheless, this species appears most similar to Elrodocer- as in its siphuncular morphology such as the funnel-shaped
Figure 4. venter on left, of ventral wall of siphuncle,
1-4, 6. Huroniella iranica sp. nov., holotype, UMUT PM 27326, isolated siphuncle, 1, dorsoventral thin section, <2, 2, transverse thin section of apical end, venter down, <2, 3, dorsoventral thin section, showing details <5, 4, dorsoventral thin section, showing details of dorsal wall of siphuncle,
<5, 6, dor-
soventral thin section, showing details of septal neck and radial canal in ventral wall of siphuncle, note contact layer and
depression on apical surface of septum, section, venter on right,
<14. 5,7,8. Armenoceras sp., 5,7: UMUT PM 27330, 5, dorsoventral thin <2, 7, dorsoventral thin section, showing details of ventral wall of siphuncle,
x14, 8: UMUT PM
27329, weathered surface of ventral side, coated with ammonium chloride, x 2.
Early Silurian cephalopods from Iran
46 Shuji Niko et al.
septal foramen, arched radial canals and relatively low form ratio of the siphuncular segments.
Material and occurrence.—UMUT PM 27331, 55 mm in length, from locality 3.
Family Huroniidae Foerste and Teichert, 1930 Genus Huroniella Foerste, 1924a
Type species.—Huronia inflecta Parks, 1915.
Huroniella iranica sp. nov.
Figures 4-1—4, 6
Diagnosis.—Huroniella with asymmetrical connecting rings ; siphuncular segments short ; adoral bending of septa lacking; width of septal foramen/distance of neighboring septal necks 2.3-3.0; perispatia wide, attain distal end of brim.
Description.—Large straight siphuncle, 20.5 mm in lateral diameter of apical end of holotype; septal necks short, approximately 0.5mm in length, strongly recurved cyrto- choanitic ; brims 0.63-0.68 mm in length, in contact with apical surface of septa; diameter of septal foramen 12.5-14. O mm; shape of connecting rings asymmetrical in dor- soventral section, ventral connecting rings strongly inflated, bluntly pointed arcs with obliquely adoral direction in longitu- dinal section ; adnation area in adoral surface of septa very wide, forming contact layer by thickening of connecting ring ; in contrast to adoral surface of septa, relatively narrow in apical surface, contact layer also recognized where septa are weakly depressed ; dorsal connecting rings semicircular with narrow adnation area lacking evident contact layer ; siphuncular segments short for huroniids, width of septal foramen/distance of neighboring septal necks 2.3-3.0. Endosiphuncular deposits of annuli well developed leaving large central canal in a position slightly shifted from axis ; radial canals curving adapically and branching, to join wide perispatia, which attain distal end of brim.
Discussion.—Huroniella iranica sp. nov. appears to be most like H. persiphonata (Billings, 1857 ; Foerste, 1927, pl. 44, fig. 1; Teichert, 1933, figs. 4, 20) from the upper Llandovery Jupiter Formation of Anticosti Island, Canada. The Lau- rentian species shares the asymmetrical profile of its con- necting rings with the present new species. The most obvious difference between these species is the septal morphology, i.e., a strong adoral bending of the septum is recognized in Huroniella persiphonata, but only a weak depression on the adoral septal surface is representative of H. iranica. In addition, the width of septal foramen/ distance of neighboring septal necks ratio (approximately 2 in H.
persiphonata versus 2.3-3.0 in H. iranica) is also a diagnostic feature.
Huroniella inflecta (Parks, 1915, pl. 6, fig. 4 ; Foerste, 1924a, pl. 16, figs. 2a, b; Teichert, 1933, fig.12), known from the “Limestone Rapids” in Ontario, is distinguished from the present species by having more strongly inflated dorsal connecting rings with a nearly symmetrical profile in dor- soventral section.
Material and occurrence.—Holotype, UMUT PM 27326, an isolated and incomplete siphuncle 65 mm in length, from locality 1.
Etymology.—The specific name in derived from Iran.
Subclass Nautiloidea Agassiz, 1847 Order Orthocerida Kuhn, 1940 Superfamily Pseudorthocerataceae Flower and Caster, 1935 ? Family Proteoceratidae Flower, 1962
Genus and species indeterminate
Figures 5-4, 7
Discussion.—The poorly preserved specimen consists of a gradually expanding orthoconic shell with relatively short camerae, subcentral siphuncle consisting of short cyrto- choanitic septal necks and inflated connecting rings. Its maximum diameter/length ratio of siphuncular segments is approximately 1.5, and cameral deposits are episeptal.
This species probably belongs to the Proteoceratidae, and its large siphuncular segment ratio for an orthocerid suggests a possible relationship with Ephippiorthoceras, although the material is insufficiently preserved to identify any further.
Material and occurrence.—Single incomplete phrag- mocone, UMUT PM 27333, 74 mm in length, from locality 2.
Stratigraphic and paleobiogeographic implications
The cephalopod species recognized at each locality are as follows : locality 1, Huroniella iranica sp. nov.; locality 2, Proteoceratidae ?, gen. and sp. indet.; and locality 3, Actinoceratidae, gen. and sp. indet., Armenoceras banes- tanense sp. nov., A. sp. and Elrodoceras sp. The most useful taxon for correlation is Huroniella, whose range is known with certainty from late Llandovery to early Wenlock strata in Laurentia and Baltica. Species similar to Huroniella iranica are found in the Anticosti Island and Hudson Bay areas and are of late Llandovery age. Flrodoceras is the only Silurian cephalopod previously known from Laurentia, Avalonia, Baltica and Siberia. Armenoceras banestanense sp. nov. is related to the late Llandovery species A. hearsti from the Hudson Bay area, and the genus is cosmopolitan
Figure 5. 1-3. Elrodoceras sp., UMUT PM 27331, 1, dorsoventral thin section, venter on right, x2, 2, dorsoventral thin section, showing details of ventral wall of siphuncle, 5, 3, dorsoventral thin section, showing details of septal necks, radial canal and connecting ring in ventral wall of siphuncle, note adapical bending of septal necks, «14. 4, 7. Proteoceratidae ?, gen. and sp. indet., UMUT PM 27333, 4, longitudinal thin section, x2, 7, longitudinal thin section, showing details of siphuncle, <8. 5,6. Actinoceratidae, gen. and sp. indet., UMUT PM 27332, 5, dorsoventral thin section, showing details
of ventral wall of siphuncle, arrows indicate septal necks, of siphuncle, 14.
<14, 6, dorsoventral thin section, showing details of dorsal wall
47
Early Silurian cephalopods from Iran
48 Shuji Niko et al.
and ranges from Middle Ordovician to Late Silurian in age. Besides cephalopods, the Wenlockian bryozoan species Trematopora beikhemensis is identified by S. Sakagami (per- sonal communication) from locality 1. Although locality 2 lacks a clear age indicator, lithologically the three horizons may belong to a stratigraphic unit without notable breaks. On the basis of this evidence, we infer that at least the cephalopod-bearing horizons in the unnamed formation indicate a late Llandovery (or early Wenlock) age, and are lithologically and chronostratigraphically correlative with the Niur Formation (Ruttner et al., 1968) in the Shirgesht area of northern East-Central Iran. On the other hand, the affinity of the cephalopod fauna is apparently with northeastern Laurentia. This new material suggests a faunal connection between Gondwana and Laurentia during Early Silurian times.
Acknowledgments
We with to thank Sumio Sakagami for providing unpub- lished data on a bryozoan associated with the present cephalopods. This research was supported by grant 0704194 from the Japanese Ministry of Education.
References
Billings, E., 1857: Report for the year 1856, of E. Billings Esq., palaeontologist, addressed to Sir William E. Logan, provincial geologist. Geological Survey of Canada. Report of Progress, for the years 1853-54-55-56, p. 247-345.
Flower, R.H., 1962 : Notes on the Michelinoceratida. New Mexico Bureau of Mines and Mineral Resources, Mem- oir 10, p. 21-42, pls. 1-6.
Flower, R.H. and Caster, K.E., 1985: The stratigraphy and paleontology of northwestern Pennsylvania. Part Il: 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.
Foerste, A.F., 1924a: Silurian cephalopods of northern Michigan. Contributions from the Museum of Geology, University of Michigan, vol. 2, p. 19-86, pls. 1-17.
Foerste, A.F., 1924b: Notes on American Paleozoic cephalopods. Denison University Bulletin, Journal of the Scientific Laboratories, vol. 20, p. 193-268, pls. 21
42.
Foerste, A.F., 1927 : Cephalopoda. In, Twenhofel, W.H. ed, Geology of Anticosti Island, p. 257-321, pls. 27-58. Canada Geological Survey, Memoir 154.
Foerste, A.F. and Teichert, C., 1930: The actinoceroids of
“ East-Central North America. Denison University Bulle- tin, Journal of the Scientific Laboratories, vol. 25, p. 201- 296, pls. 27-59.
Huckriede, R., Kürsten, M. and Venzlaff, H., 1962. Zur Geologie des Gebietes zwischen Kerman und Sagand (Iran). Beihefte zum Geologischen Jahrbuch, no. 51, p. 1-197.
Jin, J., Caldwell, W.G.E. and Norford, B.S., 1993: Early Silurian brachiopods and biostratigraphy of the Hudson Bay Lowlands, Manitoba, Ontario, and Quebec. Geo- logical Survey of Canada, Bulletin, vol. 457, p. 1-221.
Lensch, G., Schmidt, K. and Davoudzadeh, M., 1984 : Intro- duction to the geology of Iran. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, vol. 168, p. 155-164.
Miller, S.A., 1892 : Palaeontology. Annual report of Depart- ment of Geology and Natural Resources, Indiana, vol. 17, p. 611-705, pls. 1-20.
Parks, W.A., 1913: Notes on fossils. In, Tyrrell, J.B., Hudson Bay Exploring Expedition, 1912. Twenty-second Annual Report of the Ontario Bureau of Mines, part 1, p. 161-209.
Parks, W.A., 1915: Palaeozoic fossils from a region south- west of Hudson Bay. Transactions of the Royal Canadian Institute, vol. 11, p. 1-95, pls. 1-7.
Rickards, R.B., Hamedi, M.A. and Wright, A.J., 1994: A new Arenig (Ordovician) graptolite fauna from the Kerman district, East-Central Iran. Geological Magazine, vol. 131, p. 35-42.
Ruttner, A., Nabavi, M.H. and Hajian, J., 1968: Geology of the Shirgesht area (Tabas area, East Iran). Geological Survey of Iran, Report 4, p. 1-133.
Saemann, L., 1853: Ueber die Nautiliden. Palaeontogra- phica, vol. 3, p. 121-167, pls. 18-21.
Teichert, C., 1933: Der Bau der actinoceroiden Cephalopoden. Palaeontographica, Abteilung A, vol. 78, p. 111-230, pls. 8-15.
Troedsson, G.T., 1926 : On the Middle and Upper Ordovician faunas of northern Greenland, 1. Cephalopods. Med- delelser om Gronland, vol. 71, p. 1-157, pls. 1-65.
Zohrehbakhsh, A. and Vahdati Daneshmand, F., 1992: Geological Quadrangle Map of Iran 1: 250.000, sheet Rafsanjan. Geological Survey of Iran, Tehran.
Paleontological Research, vol. 3, no. 1, pp.49-56, 3 Figs., April 30, 1999
© by the Palaeontological Society of Japan
Occurrence of Carboniferous corals from the Geumcheon Formation of Danyang area, Korea
JEONG- YUL KIM’, HYO-NYONG LEE’ and CHANG- HI CHEONG’
‘Department of Earth Science Education, Korea National University of Education, Cheongwon, Chungbuk 363-791, Korea
"Department of Geological Sciences, Seoul National University, Seoul 151-749, Korea
Received 2 October 1998 ; Revised manuscript accepted 5 February 1999
Abstract. Two species of Carboniferous coral, Arachnastraea manchurica and Diphyphyllum delicatum, are described for the first time from the upper part of the Geumcheon Formation of the Danyang area, Korea. They were previously reported as Devonian corals, Disphyllum sp. and Phillipsastraea sp. Associated fossils are fusulinids, including Beedeina schellwieni, B. siviniensis, B. samarica, B. sp., Fusulina cylindrica, F. sp., Fusulinella mosquensis, Fusulinella provecta, Neostaffella sphaeroidea, and Ozawainella turgida. Occurrence of these corals and fusulinids suggests that the upper part of the Geumcheon
Formation is middle Moscovian in age.
Key words: Carboniferous, coral, Danyang area, Korea
Introduction
Yabe and Suzuki (1955) first reported specimens of corals from a limestone bed in Danyang area, Korea. They as- signed them in open nomenclature to colonial corals of Devonian type as Disphyllum sp. and Phillipsastraea sp. and suggested that Devonian deposits existed in Danyang area. Unfortunately, their specimens were lost. Furthermore, they figured only one weathered surface and one polished-slab figure of Disphyllum sp. and offered no systematic descrip- tions.
On the basis of a second discovery of coral specimens of Phacellophyllum sp.? (Disphyllum sp.) associated with fusulinids including Fusulina sp., Fusulinella sp., and Neostaf- fella sp. from nearly the same horizon as that of Yabe and Suzuki (1955), Cheong (1972) saw a problem in the Danyang area, with a Devonian dating. He mentioned that the lime- stone containing the coral is not Devonian but Moscovian (Late Carboniferous) in age and surmised that this coral, which had been known as a Devonian type, probably sur- vived into the Carboniferous.
Several months after Cheong’s report, Kato (1972) reex- amined the figures of Yabe and Suzuki (1955) and briefly documented that Disphyllum sp. and Phillipsastraea sp. re- ported from the Danyang area by Yabe and Suzuki (1955) are Diphyphyllum sp. and Arachnastraea sp. respectively.
Recently well preserved coral specimens, which are close- ly associated with abundant fusulinids, were discovered from a limestone bed of the Geumcheon Formation by the present authors. The purpose of this paper is to report an additional occurrence of Carboniferous coral specimens, which are described here as Diphyphyllum delicatum and Arachnastraea
manchurica, and to compare these with the Devonian corals Disphyllum sp. and Phillipsastraea sp. illustrated by Yabe and Suzuki (1955).
Geologic setting and fossil locality
General geological studies in the Danyang area have previously been carried out by many investigators (Kobatake, 1942 ; Brill, 1957; Lee and Kim, 1966; Son et al, 1967; Park and Cheong, 1975 ; Park et al., 1975; Kim, 1981). Kim (1971) studied the Paleozoic and Mesozoic paleocurrents of the Danyang Coalfield on the basis of sedimentary struc- tures. Structural analysis and tectonic studies of the Danyang area have been recently carried out by Cho et dl. (1986), Kim and Koh (1992), Kim et al. (1992a), Kim et al. (1992b), and Kim et al. (1994).
The Permo-Carboniferous sedimentary strata, the Pyeon- gan Supergroup, in southern Korea are widely distributed in the Danyang, Taebaeg, Yeongweol, Jeongseon, and Gang- neung areas. The sediments are shallow marine to fluvial in origin and consist predominantly of sandstone and shale with small amounts of carbonate.
Cheong (1973) subdivided the Pyeongan Supergroup into the Carboniferous Manhang and Geumcheon formations, the Permian Bamchi, Jangseong, Hambaegsan, Dosagok and Kohan formations, and Triassic Donggo Formation in ascending order.
In Danyang area, the Carboniferous strata disconformably cover the Ordovician strata and are divided into two forma- tions, namely, the Manhang and Geumcheon formations (Cheong, 1971) and are inturn unconformably overlain by the Jurassic deposits (Figure 1). Cheong (1971) firstly carried out
50 Jeong-Yul Kim et al.
biostratigraphic research on fusulinids in the Danyang area overlies the Ordovician strata. The formation, about 175 m and described 37 fusulinid species belonging to 11 genera. thick, is characterized by red to purple shale and greenish The Carboniferous Manhang Formation unconformably coarse sandstone, with the intercalation of nine white and
PO00000000. 7090000008 0099900008 9200099208 RAC 2222227 Ct. =
EA CCLOLLO0E.
36° 59' 30" N
Cece, Greene
228 2202
Sindanyang
128°22' 30" E
Geumcheon
Bansong Fm. Em:
@ Fossil locality Dosagog Fm. Manhang Fm.
Thrust fault | Hambaegsan
: Goseong Ls. A Geological boundary GQ” INEmM:
sss—- Local road number RE = Jangseong Fm. EF Om Maggol Fm.
Figure 1. Geological map and fossil localities of study area. (After Son et al., 1967 ; Lee and Kim, 1995)
Carboniferous corals from the Geumcheon Formation, Korea 5]
24
Arachnastraea manchurica Diphyphyllum delicatum Fusulina cylindrica Fusulina sp.
Fusulinella mosquensis Fusulinella provecta Ozawainella turgida
nN nN
Beedeina schellwieni edeina siviniensis Beedeina samarica Beedeina sp. Neostaffella sphaeroidea
Geumcheon Formation
Manhang Formation
CARBONIFEROUS (Moscovian) CARBONIFEROUS (Moscovian)
Limestone
Chert - bearing limestone Quartz porphyry Soil-coverd
Fossil horizon
Fault
Manhang Formation
125
Unconformity
OR.
Figure 2. Measured stratigraphic section of study area.
light gray limestone beds or lenses in the measured section The Geumcheon Formation from which the coral speci- (Figure 2). In the upper part, the formation contains gray to mens were collected is about 70 m thick and comformably bluish-gray limestone which bears white chert. covers the Manhang Formation. The formation comprises a
Jeong-Yul Kim et al.
52
WHOL. ur RN
oe N N “
< A TOY we, hy ae ¢ fh, N i
)
Carboniferous corals from the Geumcheon Formation, Korea
variety of terrigenous sediments intercalated with dark gray limestone lenses (Figure 2). The upper part of the formation is characterized by black shale and greenish sandstone. Abundant and diverse corals and fusulinids were only recor- ded from the limestone units in the formation. Lee and Kim (1995) also described Beedeina schellwieni, Fusulina sp. Neostaffella sphaeroidea, and Ozawainella turgida from the Geumcheon Formation near Gosu Pass in the Danyang area.
All of the specimens considered here were collected from a measured section of the Geumcheon Formation exposed in Gosu Pass along the local road 595, Danyang area (Figure 1). The fossil locality 1 is exposed near the top of Gosu Pass, about 1.2km north of the Sindanyang Bridge. The limestone bed of locality 1, which is 2m in thickness, is composed of abundant fusulinids and coral fragments which can not be used in the description. Many kinds of bioclasts, foraminifera, conodonts, brachiopods, and crinoids, were also found from the limestone bed.
The fossil locality 2 is about 800m northwest from the Sindanyang Bridge. Fossil specimens were collected from a 5m thick chert-bearing limestone bed which is stratigra- phically nearly 40m above the base of the Geumcheon Formation. The limestone is characterized by gray to dark gray color (Figure 2). Abundant corals together with fusulinids, brachiopods, bryozoa, and crinoid stems are cleary shown on the weathered surface of limestone bed.
Systematic description
The conventional treatment has been followed in the taxonomic hierarchy above the species level. The mor- phologic terminology used for systematic description fol- lowed is that of Hill (1935, 1956, 1981), the terminology of microstructural elements is that of Kato (1963, 1968). Speci- mens collected for the present study and described herein are housed in the Department of Earth Science Education, Korea National University of Education.
Phylum Cnidaria Hatschek, 1888 Class Anthozoa Ehrenberg, 1834 Order Rugosa Milne-Edwards and Haime, 1850 Suborder Streptelasmatina Wedekind, 1927 Family Lithostrotionidae d’Orbigny, 1851 Genus Arachnastraea Yabe and Hayasaka, 1916
Arachnastraea Yabe and Hayasaka, 1916, p. 69.
Type species.—Arachnastraea manchurica Yabe and Hayasaka, 1916, from the Lower Permian of South Manchur- ia.
Diagnosis.—Corallum compound, massive, typically cerioid or astraeoid. Septa numerous, of two orders. Septa thin, usually extending across tabularium to columella but partly
Nn LU)
discontinuous in dissepimentarium. Both major and minor septa are well developed. Tabulae conical, complete or incomplete, regular dissepimentarium (slightly modified after Hill, 1956).
Remarks.—In the typical species of the Devonian Phillips- astraea d'Orbigny, the septa never extend to the center of the corallites with horse-shoe dissepiments. The septa are dilated, especially at inner margin of dissepimentarium, and there is always a conspicuous inner wall formed by the abrupt thickening of all the septa. These characteristic features are not visible in Arachnastraea (Yabe and Hayasa- ka, 1916). Kato (1972) concluded that Yabe and Sugiyama (1940) misdescribed Arachnastraea as Phillipsastraea in an occurrence from Cheonseongri, Suncheongun, Pyeongan- namdo, Northwest Korea.
Arachnastraea manchurica Yabe and Hayasaka, 1916 Figures 3-1; 3-2 Arachnastraea manchurica Yabe and Hayasaka, 1916, p. 69.
Material.—KNUE 96201-96216 (KNUEDY Locality 2). Four specimens for this study were collected by the present authors from the measured stratigraphic section (see Figure 2).
Description.— Transverse section description : Corallum is astraeoid and composed of nearly equal-sized polygonal corallites which are 4.1-6.6 mm in diameter and have 9-11 major septa. Septa are thin, straight, alternately long and short, and fibronormal in terms of microstructure. Major septa reach the center of the corallite. Corallite walls are almost indistinguishable from septa and dissepiments. In most corallites, the major septa are 2.0-3.5 mm long and minor septa are 0.8-2.4mm long. Minor septa typically extend about 2/3 length of major septa to tabularium wall. Dissepimentarium is formed by 3-5 rows and is 0.3-2.7 mm. Tabularium has a diameter of on average 2.3 mm.
Longitudinal section description: Dissepiments are well developed in the peripheral part, elongate in form and not much inclined. Dissepimentarium rather wide, occupying about 2/3 of the diameter of the corallites and consisting of 3-5 rows of dissepiments which are an average of 2mm long. Axial tabellae and periaxial tabellae are similarly in- clined. Diameter of the tabularium varies around the aver- age of 2.2mm, from 1.8 to 3.0mm. In the tabularium, the tabulae adjacent to the dissepimentarium have a slope of 25°-40°.
Remarks.—One of the so-called ‘Devonian type corals’ from Cheonseongri described by Yabe and Sugiyama (1940) was reidentified by Kato (1972) as Arachnastraea kaipingensis (Grabau). It was the first record of occurrence of Arachna- straea in Korea. Arachnastraea manchurica differs from Arachnastraea kaipingensis in corallite walls, columella and
Figure 3. 1,2. Arachnastraea manchurica Yabe and Hayasaka ; 1, transverse section (7, KNUE 96201), 2, Longitudi-
nal section (x 7.5, KNUE 96215).
3-5. Diphyphyllum delicatum Minato and Kato ; 3, transverse section showing both the
early and mature stages («8, KNUE 96219), 4, slightly obliquely cut logitudinal section (x7, KNUE 96229), 5, slightly
obliquely cut transverse section (X 7, KNUE 96217). KNUE 96199).
6. association of Arachnastraea manchurica and Fusulinella sp. (10,
54 Jeong-Yul Kim et al.
dissepimentarium. In the latter the corallum is cerioid- astraeoid and corallite walls are well developed, sharply zigzag and partially depressed. The dissepimentarium of the latter consists of 3-4 rows of regular dissepiments.
Family Lithostrotionidae d’Orbigny, 1851 Subfamily Diphyphyllininae Dybowski, 1873 Genus Diphyphyllum Lonsdale, 1845
Diphyphyllum Lonsdale, Hill, 1956, p. 283 ; Hill, 1981, p. 383.
Type species.—Diphyphyllum concinnum Lonsdale, 1845.
Diagnosis.—Fasiculate corallum, typically without colum- ella. Septa short, continuous in dissepimentarium and amplexoid in tabularium. Columella absent or impersistent. Tabulae convex or flat, with downturned edges. Dis- sepimentarium narrow, composed of one or more rows of small dissepiments (slightly modified after Hill, 1956).
Remarks.—The species of Diphyphyllum may have a wide range of variability in terms of the structure, shape and mode of the tabulae. This genus has inner tabulae which are strongly arched, and each arch rests upon the arch below. In addition, Sando and Bamber (1985) mentioned that this genus is very similar to Siphonodenaron, from which it differs by having flat or convex tabulae and by lacking a columella or having a thin, vertically discontinuous one.
Armstrong (1970) regarded a smaller group of species, such as Diphyphyllum venosum, Diphyphyllum nasorakensis and Diphyphyllum klawockensis, as having complete tabulae with broad flat tops and downturned edges that extend to the dissepimentarium without touching the lower tabulae.
The majority of the descibed species of Diphyphyllum indicated a late Early Carboniferous age (Minato and Kato, 1975). This genus is common in North America and is found exclusively in the shallow-water carbonate lithofacies (Sando and Bamber, 1985).
Diphyphyllum delicatum Minato and Kato, 1957 Figures 3-3—3-5
Diphyphyllum delicatum Minato and Kato, 1957, p. 137, text-figs. A-C; Minato and Kato, 1974, p. 56-60.
Material.—KNUE 96217-96245 (KNUEDY Locality 2). Only two specimens for this study were collected by the present authors from the measured stratigraphic section (see Figure 2).
Description.— Transverse section description : Corallum is compound, fasciculate and dendritic rather than phaceloid. Corallites are circular to subcircular. Corallites are closely adjacent, and are often in contact. Mature corallites range from about 6.7 to 11.4 mm in diameter and possess 18 to 25 major septa. Both major and minor septa are thin, fibronor- mal in terms of microstructure. Major septa are 1.5-2.2 mm in length, protruding 0.2-0.9mm in tabularium, except for some major septa which are 0.9-1.1mm in length. Minor septa are usually confined to adaxial first row of dissepi- ments, rarely protruding into second row of dissepiments, and are 0.25 to 0.38mm in length. Dissepimentarium
ranges from 1.1 to 2.2 mm in width and consists of one to three rows of regular dissepiments. Tabularium varies from 41 to 6.4 mm in width and is open without any axial structure.
Longitudinal section description : Corallites are cylindrical and rather closely disposed. Dissepimentarium is 0.5 to 1.9 mm wide and consists of one to three rows of inclined, inflated to globose dissepiments. Tabulae are mostly com- plete, slightly concave in central part of the corallite, 4 to 9 in a vertical distance of 5mm. However, they turn down- ward at an average angle of 32° before joining the dissepi- ments.
Remarks.—Our specimens differ slightly from Minato and Kato's (1975, pl. 9, figs. 2-6, pl. 10, figs. 1-4) species Diphy- phyllum delicatum, which was described from the Upper Carboniferous Nagaiwa Series of northeast Japan, by having more numerous major septa, a wider dissepimentarium, and a more strongly developed row of dissepiments. Igo and Kobayashi (1980) described a new subspecies, Diphyphyllum delicatum nishitamensis, from the Itsukaichi District, Tokyo, Japan, which is similar to, but not conspecific with Diphy- phyllum delicatum illustrated by Minato and Kato (1975). Igo and Kobayashi (1980) noted that Diphyphyllum delicatum and Diphyphyllum delicatum nishitamensis differ noticeably in the length of major and minor septa. The former is character- ized by short major and minor septa, while the subspecies has longer septa compared with the size of the corallite.
As Minato and Kato (1957) mentioned, Diphyphyllum has a long stratigraphic range from the Lower Carboniferous to Permian, but this particular species is confined to the upper part of the Upper Carboniferous Geumcheon Formation in the Danyang area.
Discussion
One of the purposes of this study is to reexamine the Devonian corals mentioned by Yabe and Suzuki (1955). According to Kato (1972), Suzuki earlier collected several coral specimens in Gosuri, Danyang in 1944, but these materials are lost. Yabe and Suzuki (1955) reported the occurrence of the Devonian corals Disphyllum sp. and Phillipsastraea sp. Their figures 1 and 2 are index maps of the fossil locality, while figures 3 and 4 show the corals on the weathered surface of the limestone near Gosu Pass in Danyang area. The figures are not clear, but colony type and internal structure of corals were, however, distinguished.
On the basis of their figure 3, several clues to identification of the corals were found by the present authors. First of all, the corallites in figure 3 are compound, fasciculate and dendritic rather than phaceloid. Although Yabe and Suzuki (1955) identified them as Disphyllum sp., the branches of their coral specimens are too irregular to be those of Disphyllum. The second is that the septa are very short and the dis- sepimentarium are very narrow with one or two rows of small dissepiments. In longitudinal view, the tabulae are convex with downturned edges without columella. These are typi- cal characters of Diphyphyllum. It is considered that the coral specimens described by Yabe and Suzuki (1955) are not of the Devonian genus Disphyllum, but the Carboniferous Diphyphyllum. Disphyllum sp. is illustrated only in figure 3 of
Carboniferous corals from the Geumcheon Formation, Korea
Yabe and Suzuki (1955), but they did not provide any illustra- tions of Phillipsastraea sp.
Furthermore, fusulinids and conodonts occur abundantly from the Geumcheon Formation. A number of fusulinids are observed together with corals in the same thin sections (Figure 3-6). Because the Carboniferous corals have long ranges, both fusulinids and conodonts may provide a useful criteria for understanding the paleoecology and determining the geologic age of the Geumcheon Formation.
Conclusion
Two species of rugose corals from the Geumcheon For- mation in the Danyang area, Korea are described as Arach- nastraea manchurica and Diphyphyllum delicatum. The corals indicate that the age of the Geumcheon Formation is middle Moscovian, Late Carboniferous.
Coral specimens from the Danyang area once illustrated as the Devonian corals Disphyllum sp. and Phillipsastraea sp. (Yabe and Suzuki, 1955), are considered Carboniferous corals, Diphyphyllum sp. and Arachnastraea sp. respectively.
Acknowledgments
We wish to sincerely thank Makoto Kato, Professor Emeritus of Hokkaido University, and Hisayoshi Igo, Professor Emeritus of the University of Tsukuba for sending useful references and giving comments. We wish to express our thanks to E.W. Bamber, Geological Survey of Canada, Lin Baoyu, Institute of Geology, Chinese Academy of Geological Sciences, Lin Ying Dang, Changchum College of Geology, and Wang Xun Lian, China University of Geosciences, for kindly offering helpful comments and sending many copies of valuable references. Special thanks are given to two anonymous referees for critically reviewing the original manuscript and suggesting numerous useful comments and constructive revisions.
References
Armstrong, A.K., 1970: Mississippian rugose corals, Per- atrovich Formation, west coast, Prince of Wales Island, southeastern Alaska. U.S. Geological Survey Profes- sional Paper, no. 534, 44 p.
Brill, G., 1957 : Geology of Tanyang Coalfield of the Republic of Korea. Geological Report on Coalfields of Korea, vol. 1, p. 75-98.
Cheong, C.H., 1971: Stratigraphy and paleontology of the Danyang Coalfield, North Chungcheong-do, Korea. Journal of Geological Society of Korea, vol. 7, p. 63-88.
Cheong, C.H., 1972: On the Devonian problem in Korea. Journal of Geological Society of Korea, vol.8, p. 53-54.
Cheong, C.H., 1973: A paleontological study of the fusulinids from the Samcheog Coalfield, Korea. Jour- nal of Geological Society of Korea, vol. 9, p. 47-82.
Cho, M.J., Choi, Y.S., Kang, P.C. and Choi, K.H., 1986: A study on structural analysis for the southern part of Taebaegsan region. Researches on Coal Resources vol. 5 (KR-86-2-10), p. 239-279.
Hill, D., 1935: British terminology for rugose corals. Geo-
Un in
logical Magazine, vol. 72, p. 481-519.
Hill, D., 1956: Rugosa. In, Moore, R.C. ed., Treatise on Invertebrate Paleontology, Part F, Coelenterata, p. 233 324. Geological Society of America and University of Kansas Press, Lawrence.
Hill, D., 1981: Rugosa and Tabulata. In, Teichert, C. ed., Treatise on Invertebrate Paleontology, Part F, Coelen- terata, Supplement 1, 762p. Geological Society of America and University of Kansas Press, Lawrence.
Igo, H. and Kobayashi F., 1980: Carboniferous corals from the Itsukaichi district, Tokyo, Japan. Science Report, Institute of Geoscience, University of Tsukuba, Section B, vol.1, p. 149-162.
Kato, M., 1963: Fine skeletal structures in Rugosa. Journal of Faculty of Science, Hokkaido University, Series 4, vol. 11, p. 571-630.
Kato, M., 1968: Note on the fine skeletal structures in Scleractinia and Tabulata. Journal of the Faculty of Science, Hokkaido University, Series 4, vol. 14, p. 45-50.
Kato, M., 1972: Devonian of Korea. Journal of Geological Society of Japan, vol. 78, p. 541-544.
Kim, H.M., 1971: Paleozoic and Mesozoic paleocurrents of the Danyang Coalfield, Korea. Journal of Geological Society of Korea, vol. 7, p. 257-276.
Kim, J.H. and Koh, H.J., 1992: Structural analysis of the Danyang area, Danyang Coalfield, Korea. Journal of Korean Institute of Mining Geology, vol. 25, p. 61-73.
Kim, J.H., Lee, J.Y. and Nam, K.H., 1992a : Geological struc- tures of the Yeongchun area, Danyang Coalfield, Korea. Journal of Korean Institute of Mining Geology, vol. 25, p. 179-190.
Kim, J.H., Lee, J.Y., Nam, K.H. and Choi, B.Y., 1992b: Paleostress analysis within the thrust zone, Yeongchun, Danyang Coalfield, Korea. Journal of Geological Soci- ety of Korea, vol. 28, p. 184-195.
Kim, J.H., Lee, J.Y. and Nam, K.H., 1994 : Pre-Jurassic thrust movement in Danyang area, Danyang Coalfield, Korea. Journal of Geological Society of Korea, vol. 30, p. 35- 40.
Kim, J.S., 1981: Geology of the Danyang Coalfield. Journal of Geological Society of Korea, vol. 17, p. 131-133. Kobatake, N., 1942 : Geology of the Tanyo Coalfield and its environment in N. Chuseido. Science Report, Geologi-
cal Institute of Kyoto University, vol. 1, p. 1-20.
Lee, C.Z. and Kim, G.R., 1995: Fusulinids from the Geum- cheon Formation in Danyang Coalfield, Korea. Journal of Korean Earth Science Society, vol. 16, p. 144-151.
Lee, D.W. and Kim, D.S., 1966: Geology of northern part of Danyang Coalfield. Geological Report on Coalfield of Korea, vol. 7, p. 5-32.
Minato, M., 1975: Upper Carboniferous corals from the Nagaiwa Series, southern Kitakami Mountains, N.E. Japan. Journal of Faculty of Science, Hokkaido Uni- versity, vol. 16, p. 43-119.
Minato, M. and Kato, M., 1957: Two Carboniferous corals from the Kitakami Mountains, northeast Honshu, Japan. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, no. 28, p. 137-142.
Park, S.I. and Cheong, CH, 1975: A study on the Jurassic Sapyeongri Conglomerate in the vicinity of Danyang, N. Chungcheongdo, Korea. Journal of Geological Society of Korea, vol. 11, p. 24-37.
Park, J.S., Shin, M.S., Chung, C.S., Lee, M.H., Yoon, Y.D.,
Nn a
Kim, S.H. and Hwang, H.S., 1975 : Geological investiga- tion report of Danyang Coalfield. p. 54.
Sando, W.J. and Bamber, E.W., 1985: Coral zonation of the Mississippian System in the western interior province of North America. U.S. Geological Survey Professional Paper, no. 1334, 55 p.
Son, C.M., Cheong, C.H., Kim, B.K., Lee, S.M. and Kim, S.J., 1967 : Geology of the Danyang Coalfield. Geological Report on Coalfields of Korea, vol. 8, p. 73-94.
Jeong-Yul Kim et al.
Yabe, H. and Hayasaka, I, 1916: Paleozoic corals from
Japan, Korea and China. Journal of Geological Society of Tokyo, vol. 23, p. 9-22.
Yabe, H. and Sugiyama, T., 1940: Discovery of corals of
Devonian types from Tyosen (Korea). Proceedings of the Japan Academy, vol. 15, p. 305-310.
Yabe, H. and Suzuki, A., 1955: Second occurrence of
colonial coral of Devonian type in Tyosen (Korea). Proceedings of the Japan Academy, vol. 31, p. 355-359.
Cheonseongri KEH, Danyang Fi, Donggo Formation # Gangneung {1 {%, Geumcheon Formation 27)! |/e, Jangseong Formation EE, Jeongseon fig#=, Kohan Formation HE, Manhang Formation Hé
Gosu 5
tf}, Dosagok Formation 78-4 Hambaegsan Formation Jak All
le EI
TES, Pyeongan Supergroup FASIEÉ£, Sindanyang #1}, Taebaeg KH, Yeongweol Fk
Paleontological Research, vol. 3, no. 1, pp. 57-64, 6 Figs., April 30, 1999
© by the Palaeontological Society of Japan
Relation of growth rings to reproductive cycle in Cryptopecten vesiculosus, a dimorphic
pectinid bivalve
NAOKO TAKENAKA
Shinagawa Joshi Gakuin, 3-3-12 Kitashinagawa, Shinagawa-ku, Tokyo 140-8707, Japan
Received 30 October 1998 ; Revised manuscript accepted 23 February 1999
Abstract. The relation between growth rings and reproductive cycle in a dimorphic pectinid bivalve, Cryptopecten vesiculosus (Dunker, 1877) was examined histologically on the basis of semi-regularly collected samples from Sagami Bay. This pectinid is hermaphroditic. Male and female gonads ripen between June and September, and spawning occurs during July to November. A strong growth ring is formed just before spawning, and the first ring indicates that the specimens has reached the stage of sexual maturity. This means that growth rings are formed once a year after the individual reaches sexual maturity. No visual difference was detected in the gonad development between the two phenotypes ; their gonadal weight indices are statistically identical throughout the year. Therefore the previous interpretation that the dimorphism represents discontinous intrapopulational variation is upheld. The
results of this study are applicable to life history analysis in extant and fossil populations.
Key words: Dimorphism, growth rings, life history, pectinid bivalve, reproductive cycle
Introduction
The pectinid bivalve, Cryptopecten vesiculosus (Dunker, 1877) is characterized by a few prominent commarginal growth rings, which consist of periodic changes in the convexity of the disc surface. It has been judged that the growth rings are caused by a growth pause during the reproductive season. Furthermore, C. vesiculosus has been considered a dimorphic species, because two discrete phenotypes exist in every population. One phenotype has highly elevated and generally quadrate radial ribs, while the other has low and generally rounded radial ribs. They have been called “Phenotype Q” and “Phenotype R”, respectively. These two phenotypes are strictly sympatric, and their allozyme patterns show no statistical difference. Conse- quently it has been believed that the dimorphism is due to discontinous intrapopulational variation (Hayami, 1984 ; Sar- ashina, 1995).
Histological observations on the development of gonads through the year is vital to prove the assumptions mentioned above, as well as to trace a clear relation between growth rings and the reproductive cycle. The relation, if clarified, would become fundamental to analyses of life history (espe- cially, age, lifespan, growth rate and mortality rate) not only in extant but also in fossil populations.
Material and method
Cryptopecten vesiculosus (Dunker, 1877) is distributed from the central part of Japan to the East and South China Sea. It is a lower sublittoral species, living Commonly on sandy bottoms at the depth of 50-200 m (Hayami, 1984). Fossils of this species are also found abundantly in Early Pliocene and later marine deposits of Japan. Living individuals of C. vesiculosus were collected monthly to bimonthly between March 1997 and February 1998 almost at one and the same station, about 2 km west of the western end of Jögashima Islet in the eastern part of Sagami Bay [35°08’N, 139°35’E, 80-85 m]. Table1 shows the dates of dredging and the number of collected living individuals. The integrated rela- tive frequency of the two phenotypes is almost identical with the ratio indicated by Hayami (1984) in samples Jg (1-26) collected during 1974-1983 at nearby stations in Sagami Bay, and statistically there is no significant difference.
To clarify the reproductive cycle and the shell size at sexual maturity, | observed the process of gametogenesis and determined the gonad developmental phase for many individuals in each phenotype. Collected specimens were anesthetized with 0.01% 2-phenoxyethanol methylene glycol diluted with sea water, and then fixed for 48 hours in a solution of 10% formaldehyde. The dissected gonadal tis- sue of each specimen was excised and weighed after rinsing in water. It was dehydrated through a graded series of ethanol and benzol, and then embedded in paraffin (melting
58 Table 1. Collecting dates and the number of individuals of Cryptopecten vesiculosus.
Date Na Nea N P Op Mar. 25, 1997 9 14 23 0.61 0.10 May 1, 1997 42 30 72 0.42 0.06 Jun 4, 1997 26 25 51 0.49 0.07 Jul. 29, 1997 54 30 84 0.36 0.05 Sep. 30, 1997 79 67 146 0.46 0.04 Nov. 19, 1997 35 28 63 0.44 0.06 Dec. 18, 1997 44 31 75 0.41 0.06 Feb. 16, 1998 36 36 72 0.50 0.06
Total 325 261 586 0.45 0.02
N: Total number of individuals ; No: Number of individuals belonging to Phenotype Q; Nr: Number of individuals belonging to Phenotype R; P=Nr/N; op: Standard error.
point: 56~58'C). Thin transverse sections of the gonadal tissue were prepared at intervals of 8 um and stained with Lillie-Mayer's hematoxylin-eosin. The stained thin sections were observed and photographed using an Olympus model BX50 optical microscope. Based on histological examina- tion of the thin-sectioned gonadal tissue, each specimen was assigned to a specific gonad developmental phase : early active phase (EA), late active phase (LA), ripe phase (R), partially spawned phase (PS), or spent phase (S). Further, the mean gonad index [(gonad weight 100)/soft body weight] was calculated for sexually mature individuals to analyze the annual reproductive cycle of the population. The results were analysed to determine whether or not growth rings can be used as an index of age. Shell height from the umbo to each growth ring, normal to the hinge line, was measured in all the samples with a digimatic caliper (accuracy+0.02 mm). In addition, the numbers of growth rings was counted, and the mean shell height at each growth ring was calculated for individuals with more than three growth rings. The fit of these mean values to von Bertalanf- fy, Gompertz and logistic curves was examined. These Curves are expressed by the following formulae : H(B)=K(1— expla—Rt)) (von Bertalanffy curve) H(G)= Kexp(— aexpfRt) (Gompertz curve) H())=K /(1+ exp(a— Rt)) (logistic Curve) where H is the size of the animal (Shell height in this case) at age t, K is the upper limit of the curve, R is the specific growth rate, and a is a constant defined by the initial size (=H,) at t=0.
Naoko Takenaka
Results
1. The reproductive cycle of Cryptopecten vesiculosus
Spermatozoa were observed in the milky white proximal part of the crescentic gonad and oocytes in the orange distal part. In consequence, it was confirmed that Cryptopecten vesiculosus is hermaphroditic and that the shell dimorphism is never sexual. Histological examination of gonadal tissue revealed that gametogenesis in C. vesiculosus is essentially similar to that in the commercial scallop Azumapecten farreri nipponensis, which was analyzed by Kanno and Tanita (1961), though that species is dioecious. Following the general classification of gametogenetic phases in bivalves proposed by Ropes (1968) and Sato (1995), the reproductive cycle of C. vesiculosus is described below.
Early active phase (Figure 1A, B)
In the male gonad of this phase, many spermatogoniums about 8 um in diameter, each of which consists of a nucleus and thin nucleoplasm, appear along the inner periphery of the alveolar walls. Further, spermatocytes about 5 um in diameter proliferate towards the lumina from the alveolar walls. Oogoniums and oocytes which protrude inside the alveolar walls are seen in the female gonad. The oogoniums range from 15 to 20 um and the oocytes range from 20 to 30 um in diameter. Each oocyte has a nucleus about 15-20 4m, which contains a nucleolus approximately 4 um in diameter.
Late active phase (Figure 1C, D)
Many spermatocytes are seen in the male gonad of this phase. Spermatids about 4.5 um in diameter also are seen, and they form dense masses near the center of the alveoli. A transformation of the spermatids results in the appearance of sperm. They form weak columns toward the center of the alveoli. Oocytes in the late active phase are mostly rounded and larger than in the early active phase. Some oocytes are attached to the basement membrane of the alveoli, but most are free in the lumina. In this phase oogoniums and ripe oocytes coexist within one and the same female gonad.
Ripe phase (Figure 1E, F)
In this phase, spermatozoa or free oocytes occupy the major space in the gonadal tissue. The head of each sperm is corn-shaped and about 2 wm in length. Oocytes are free in the lumina of the alveoli. Each oocyte about 60 um in diameter contains a round or oval nucleus ranging from 30 to 35 um, and each nucleus possesses one small opaque basophilic nucleolus about 5 um in diameter. Ripe gonads typically have a dense appearance because the alveoli are crowded together and are filled with large oocytes or numer-
Figure 1. Optical photomicrographs of sections of male and female gonadal tissues in Cryptopecten vesiculosus in
each phase of the reproductive cycle.
The scale bar in A pertains as well to B-J. All specimens were collected from
Sagami Bay. A: Early active phase of a male collected on 16 February 1998. B: Early active phase of a female collected on 16 February 1998. C: Late active phase of a male collected on 25 March 1997. D: Late active phase of a female
collected on 25 March 1997.
E: Ripe phase of a male collected on 29 July 1997. F: Ripe phase of a female collected
on 29 July 1997. G: Partially spawned phase of a male collected on 19 November 1997. H: Partially spawned phase of
a female collected on 19 November 1997. a female collected on 18 December