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Paleontological Research Paleontological Research ISSN 1342-8144 Formerly Transactions and Proceedings of the Palaeontological Society of Japan Vol. 4 No.2 June 2000 The Palaeontological Society of Japan Co-Editors Kazushige Tanabe and Tomoki Kase Language Editor Martin Janal (New York, USA) Associate Editors Jan Bergstrom (Swedish Museum of Natural History, Stockholm, Sweden), Alan G. Beu (Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand), Satoshi Chiba (Tohoku University, Sendai, Japan), Yoichi Ezaki (Osaka City University, Osaka, Japan), James C. Ingle, Jr. (Stanford University, Stanford, USA), Kunio Kaiho (Tohoku University, Sendai, Japan), Susan M. Kidwell (University of Chicago, Chicago, USA), Hiroshi Kitazato (Shizuoka University, Shizuoka, Japan), Naoki Kohno (National Science Museum, Tokyo, Japan), Neil H. Landman (Amemican Museum of Natural History, New York, USA), Haruyoshi Maeda (Kyoto University, Kyoto, Japan), Atsushi Matsuoka (Niigata University, Niigata, Japan), Rihito Morita (Natural History Museum and Institute, Chiba, Japan), Harufumi Nishida (Chuo University, Tokyo, Japan), Kenshiro Ogasawara (University of Tsukuba, Tsukuba, Japan), Tatsuo Oji (University of Tokyo, Tokyo, Japan), Andrew B. Smith (Natural History Museum, London, Great Britain), Roger D. K. Thomas (Franklin and Marshall College, Lancaster, USA), Katsumi Ueno (Fukuoka University, Fukuoka, Japan), Wang Hongzhen (China University of Geosciences, Beijing, China), Yang Seong Young (Kyungpook National University, Taegu, Korea) Officers for 1999-2000 President: Kei Mori Councillors: Kiyotaka Chinzei, Takashi Hamada, Yoshikazu Hasegawa, Itaru Hayami, Hiromichi Hirano, Noriyuki Ikeya, Junji Itoigawa, Tomoki Kase, Hiroshi Kitazato, Itaru Koizumi, Haruyoshi Maeda, Ryuichi Majima, Makoto Manabe, Hiroshi Noda, Ikuwo Obata, Kenshiro Ogasawara, Terufumi Ohno, Tatsuo Oji, Tomowo Ozawa, Yukimitsu Tomida, Tsunemasa Saito, Takeshi Setoguchi, Kazushige Tanabe, Akira Yao ,;... Members of Standing Committee: Hiroshi Kitazato (General Affairs) , Tatsuo Oji ( aison Officer), Makoto Manabe (Finance), Kazushige Tanabe (Editor in Chief, PRJ, Tomoki Kase (Co- Editor, PRJ, RyUlchi Majima (Planning), Hiromichi Hirano (Membership), Kenshiro Ogasawara (Foreign Affairs) , Haruyoshi Maeda (Publicity Officer), Noriyuki Ikeya (Editor, "FoSSils"), Yukimitsu Tomida (Editor in Chief, Special Papers), Tamiko Ohana (Representative, Union of Natural History Societies). Secretaries: Masanori Shimamoto, Takao Ubukata (General Affairs) , Hajime Taru (Planning), Tokuji Mitsugi (Membership), Shuko Adachi (Foreign Affairs) , Kazuyoshi Endo, Yasunari Shigeta, Takenori Sasaki (Editors of PRJ , Akira Tsukagoshi (Editor of "Fossiles"), Naoki Kohno (Editor of Special Papers), Hidenori Tanaka (Publicity officer) 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: [email protected] In the USA, Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. Phone: (978)750-8400, Fax: (978)750- 4744, www.copyright.com Cover: Idealized sketch of Nipponites mirabilis Yabe, a Late Cretaceous (Turonian) nostoceratid ammonite. Various reconstructions of the mode of life of this species have been proposed, because of its curiously meandering shell form (after T. Okamoto, 1988). All communication relating to this journal should be addressed to the PALAEONTOLOGICAL SOCIETY OF JAPAN c/o Business Center for Academic Societies, Honkomagome 5-16- 9, Bunkyo- ku, Tokyo 113-8622, Japan Visit our society website at http://ammo.kueps.kyoto-u.ac.jp./palaeontlindex.html Paleontological Research, vol. 4, no. 2, pp. 83-88, June 30, 2000 © by the Palaeontological Society of Japan Orthoconic cephalopods from the Lower Permian Atahoc Formation in East Timor SHUJI NIKO\ TAMIO NISHIDA2 and KEIJI NAKAZAWA3 1 Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima 739-8521, Japan ([email protected]) 2Department of Earth Science, Faculty of Education, Saga University, Saga 840-0027, Japan ([email protected]) 328-2, Koyama Shimouchikawara-cho, Kitaku, Kyoto 603-8132, Japan Received 10 August 1999; Revised manuscript accepted 20 January 2000 Abstract. Three species of orthoconic cephalopods, Mooreoceras sp. and Atahococeras timorense gen. and sp. nov. of the Pseudorthoceratidae, and an indeterminate genus and species of the Bactritidae are described from the Lower Permian Atahoc Formation in the Cribas area, East Timor. Apparent changes in the surface ornamentation of Atahococeras are considered to be genus-level criteria that separate it from the most closely related genus, Bitaunioceras. This assemblage signi­ fies a non-ammonoid cephalopod fauna in the northern margin of Gondwana near the Sakmari­ an/Artinskian boundary. Key words: Atahococeras gen. nov., Bactritida, East Timor, Gondwana, Orthocerida, Sakma­ rian/Artinskian boundary Introduction reddish shale is considered to correspond to the ammonoid horizon of Audley-Charles (1968, p. 6, fig. 2, columnar sec­ Timor is the largest (maximum ca. 365 km long and 100 tion of the Cribas Anticline), about 150 m below the top of km wide) island in the Banda Arc of the Indonesian the Atahoc Formation. Since Grunau (1953, 1956) first as­ Archipelago, where corresponds toa collision zone between signed this formation to the Sakmarian (Lower Permian) the Indo-Australian and Asian Plates. Thus, the geology of based on ammonoids, a number of subsequent workers this island is structurally complex. Carter et al. (1976) have given support to this determination (e.g., Schouppe, stated that the older rocks on Timor consist of the 1957; Shimizu, 1966; Audley-Charles, 1968). More recent autochthonous Australian facies and overthrusting units .de­ and detailed paleontological research by Nishida et al. rived from the Asian island arc. The purpose of this study (1997) revealed co-occurrence of ammonoids with the pre­ is to document and describe an Early Permian orthocerid sent orthocerids and bactritid, namely Somoholites beluenis and bactritid cephalopod fauna of the Atahoc Formation, (Haniel), Agathiceras cf. sundaicum Haniel, Metapronorites which is part of the autochthonous facies. The materials timorensis (Haniel) and Atsabites weberi Haniel. They con­ were collected by one of us (K. N.) from the right bank of the cluded that the fossil horizon corresponds stratigraphically to River Sumasse, west of Cribas under cooperation with H. the boundary between the Somohole and Bitauni Suzuki and T. Takahashi during field work of 1961 in East Formations in West Timor, the age of which horizon is cor­ Timor (Figure 1). Other than "Orthoceres" that were re­ relative with near the Sterlitamakian (latest Sakmarian)/ ported by Gageonnet and Lemoine (1958), this is the first Aktastinskian (earliest Artinskian) boundary. description of non-ammonoid cephalopods from the Atahoc Blendinger et al. (1992) stated, on the basis of Formation. ammonoids, that a con specific middle Permian fauna flour­ The Lower Permian Atahoc Formation is made up of the ished from Timor to the western Mediterranean along the oldest exposed sediments in East Timor, and forms the northern margin of Gondwana. We shall not comment on Cribas Anticline together with the Upper? Permian Cribas, the paleobiogeographic implications of the present result, the Triassic Aitutu and the Triassic to Jurassic Wai Luli because knowledge concerning Permian nautiloids and Formations in the Cribas area (Audley-Charles, 1968; Figure bactritoids in this province is still sparse. Besides a record 1). It consists of more than 600 m of sandstone and shale of a Wordian (early Late Permian) fauna from Oman (Niko et with thin intercalated beds of limestone and basaltic lava. al., 1996), the present paper represents the only other docu­ The stratigraphic position of the present cephalopod-bearing mentation of non-ammonoid cephalopods with modern 84 Shuji Niko et at. STUDY AREA _ allochthonous un its ~post-JUraSSic fm D Wai Luli Fm. [m~mmJ A i t u t u F m. ~ Cribas Fm. Atahoc Fm. Figure 1. Map showing fossillocalily (arrow), and geology of the Cribas area, East Timor (modified from Audley-Charles, 1968). taxonomic treatment in the northern margin of Gondwana, diameter/length ratio approximately 3.4; septal curvature and therefore provides the base data for paleobiogeography shallow. Siphuncle subcentral, shifted dorsally from center, of nautiloids and bactritoids. consists of cyrtochoanitic septal necks, 0.70-0.99 mm in The specimens studied are deposited in the pale­ length, and inflated connecting rings that are subcylindrical ontological collections of the Department of Geology and to fusiform in shape; adnation area narrow. Cameral de­ Mineralogy, Faculty of Science, Kyoto University (KU). posits thin, episeptal-mural apically and mural adorally; endosiphuncular deposits weakly developed, form annuli Systematic paleontology that are unfused and restricted near septal foramina. Discussion.-Although the surface ornamentation of the Subclass Nautiloidea Agassiz, 1847 examined specimens is not observable, their oval shell cross Order Orthocerida
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