Hostname: page-component-cd9895bd7-gxg78 Total loading time: 0 Render date: 2024-12-26T04:30:26.506Z Has data issue: false hasContentIssue false
  • English
  • Français

Mosasaur remains from the Upper Cretaceous Izumi Group of southwest Japan

Published online by Cambridge University Press:  01 April 2016

M. Tanimoto
M. Tanimoto*
Affiliation:
Higashi 3–249, Yurigaoka, Nabari, Mie 518-0473, Japan. Email: [email protected]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Until recently, mosasaur remains from the Izumi Group (Upper Cretaceous) in southwest Japan comprised only scattered finds; now a richer material is available. From the upper Campanian Hiketa Formation in Kagawa Prefecture, Kourisodon sp. has just been recorded, on the basis of portions of skull and mandible which has small and laterally compressed teeth. A few teeth of the same or similar type have previously been described from the Maastrichtian Mutsuo Formation in Osaka Prefecture. A report of Mosasaurus sp. A, which resembles M. missouriensis and M. dekayi, is based on some cranial and mandible remains, inclusive of numerous teeth and a few well-preserved cervical and two incomplete dorsal vertebrae, from the Maastrichtian Mutsuo Formation in Osaka Prefecture. A slender tooth of Mosasaurus sp. from the Mutsuo Formation has since been reassigned to Platecarpus (Plioplatecarpinae); yet, this may indeed by a species of Mosasaurus, here listed as Mosasaurus sp. B. To date, smaller specimens of mosasaurids have been shown to be abundant in the Izumi Group, which suggests two possible explanations. Either most of these represent juveniles, or smaller-sized, Kourisodon-like animals flourished here. Finds of Kourisodon sp. from the upper Campanian Hiketa Formation and the Maastrichtian Mutsuo Formation suggests the second explanation is the more likely one.

Keywords

mosasaursUpper CretaceousIzumi Groupsouthwest Japan
Type
Research Article
Information
Netherlands Journal of Geosciences , Volume 84 , Special Issue 3: Proceedings of the First Mosasaur Meeting , September 2005 , pp. 373 - 378
Copyright
Copyright © Stichting Netherlands Journal of Geosciences 2005

References

Geological Club of Kinki (Kinki Chigakukai), 1991. Izumi-Sanmyaku no Hakuakei Kasekishu (Cretaceous Fossils from the Izumi Mountains). Geological Club of Kinki: 93 pp.Google Scholar
Itihara, M., Ichikawa, K. & Yantada, N., 1986. Geology of Kishiwada district; with geological map, 1:50,000. Geological Survey of Japan (Tokyo): 148 pp.Google Scholar
Iwaki, T. & Maeda, H., 1989. Mudstone facies and the fossil molluscan assemblages of the Upper Cretaceous Izumi Group in the southeastern Awaji Island, southwest Japan. Research Report of Kochi University 38: 187–201.Google Scholar
Kawakami, T., Terui, K., Hasegawa, Y. & Oishi, M., 1985. Upper Cretaceous mosasaurid teeth from the Kunitan Group, in the northeast of Kitakami Mountains, Japan. Bulletin of the Iwate Prefectural Museum 3: 133–142.Google Scholar
Morozumi, Y., 1985. Late Cretaceous (Campanian and Maastrichtian) ammonites from Awaji Island, southwest Japan. Bulletin of the Osaka Museum of Natural History 39: 1–58.Google Scholar
Nicholls, E. & Meckert, D., 2002. Marine reptiles from the Nanaimo Group (Upper Cretaceous) of Vancouver Island. Canadian Journal of Earth Sciences 39: 1591–1603.Google Scholar
Obata, I., Hasegawa, Y. & Otsuka, H., 1972. Preliminary report on the Cretaceous reptile fossils from Hokkaido. Memoirs of the National Science Museum 5: 213–222.Google Scholar
Ohara, M., 2004. Kyoryu Jidai in Wakayama (The age of dinosaurs in Wakayama). Wakayama Prefectural Museum of Natural History: 19 pp.Google Scholar
Sakurai, K., Chitoku, T. & Shibuya, N., 1999. A new species of Mosasaurus (Reptilia, Mosasauridae) from Hobetsu, Hokkaido, Japan. The Bulletin of the Hobetsu Museum 15: 53–66.Google Scholar
Suzuki, S., 1985a. Upper Cretaceous mosasaur remains from southern part of central Hokkaido, Japan: a preliminary report. The Bulletin of the Hobetsu Museum 2: 31–42.Google Scholar
Suzuki, S., 1985b. A new species of Mosasaurus (Reptilia, Squamata) from the Upper Cretaceous Hakobuchi Group in the Central Hokkaido, Japan. Monograph of the Association for Geological Collaboration in Japan 30: 45–66.Google Scholar
Takata, M., 2004. Posterior dorsal vertebra of Mosasauridae found in the Izumi Mountain range, southwest Japan (Upper Cretaceous Maastrichtian). Bulletin of the Natural History Museum Kishiwada 1: 31–38.Google Scholar
Tanimoto, M., 1993. Mosasaurid fossils from Izumi Group (Maastrichtian) of Osaka Prefecture, West Japan. Abstracts, 142nd Regular Meeting of the Palaeontological Society of Japan: 41.Google Scholar
Tanimoto, M., 1997a. A tentative skeletal restoration of Mosasaurus cf. conodon (Reptilia, Squamata) from the Upper Cretaceous Izumi Group in Southwest Japan. Chigakukenkyu 46: 87–91.Google Scholar
Tanimoto, M., 1997b. Vertebrate fossils of the Upper Cretaceous Izumi Group, southwest Japan. Natural History Museum, Kishiwada City: 28 pp.Google Scholar
Tanimoto, M. & Date, Y., 2000a. A small tooth of Mosasaurus from the Izumi Group (Upper Cretaceous Maastrichtian) of Kaizuka City, Osaka Prefecture, southwest Japan. Chigakukenkyu 48: 219–223.Google Scholar
Tanimoto, M. & Date, Y., 2000b. The first find of a mosasarid phalange from the Upper Cretaceous Izumi Group, southwest Japan. Chigakukenkyu 48: 225–229.Google Scholar
Tanimoto, M., Kamei, K. & Miyamoto, J., 1995. Osakahu Hannanshi Hakotsukuri no Izumisogun (koki hakuaki) yori sanshutushita sekitsuidobutsu kaseki - tokuni mosasaurusurui ni tsuite (Vertebrate fossils of Izumi Group (Late Cretaceous) from Hakotsukuri, Hannán City, Osaka Prefecture - especially on mosasaurs). Journal of Fossil Research 27: 79.Google Scholar
Tanimoto, M. & Kanazawa, Y., 2001. A mosasaurid fossil from the Upper Cretaceous Izumi Group (Upper Campanian) of Kagawa Prefecture, southwest Japan. Abstracts with Programs, 2001 Annual Meeting of the Palaeontological Society of Japan: 190.Google Scholar
Tanimoto, M., Kanazawa, Y. & Sato, M., 2004. Kourisodon sp. (Mosasauridae) from the Upper Cretaceous Izumi Group (Upper Cretaceous Campanian) of Kanewari, Tawa, Sanuki City, Kagawa Prefecture, southwest Japan. Chigakukenkyu 52: 21–25.Google Scholar
Tanimoto, M. & Kikyo, T., 2001a. Gillicus skeleton from the Upper Cretaceous Izumi Group (Lower Maastrichtian) of Yura-Cho, Sumoto City, Hyogo Prefecture, southwest Japan - the first find of a fossil of the family Ichthyodectidae in Japan. Chigakukenkyu 50: 41–43.Google Scholar
Tanimoto, M. & Kikyo, T., 2001b. Articulated posterior caudal vertebrae of the Mosasauridae from the Upper Cretaceous Izumi Group (Lower Maastrichtian) of Nandan-Cho, Mihara-Gun, Hyogo Prefecture, southwest Japan. Chigakukenkyu 50: 161–165.Google Scholar
Tanimoto, M. & Kishimoto, M., 2002. Big mosasaurid vertebrae from the Upper Cretaceous Izumi Group of Sumoto-City, Hyogo Prefecture, southwest Japan. Chigakukenkyu 51: 135–141.Google Scholar
Tanimoto, M. & Miyamoto, J., 1996. A mosasaurid fossil from Nagata, Midorimati, Hyogo Prefecture, southwest Japan. Konseki 19: 41, 42.Google Scholar
Tanimoto, M. & Nunoya, H., 2000. A mosasaurid tooth (Mosasaurus sp.) from the Upper Cretaceous Izumi Group of Showa-Ike, Sennan City, Osaka Prefecture, southwest Japan. Chigakukenkyu 49: 141–145.Google Scholar
Tanimoto, M. & Nunoya, H., 2003. Reexamination of a mosasaurid tooth from the Upper Cretaceous (Maastrichtian) Izumi Group of Showa-Ike, Sennan City, Osaka Prefecture, southwest Japan. Chigakukenkyu 52: 101–105.Google Scholar
Tanimoto, M., Sato, M. & Takata, M., 1994. ?Mosasaurus sp. (Reptilia, Squamata) from the Upper Cretaceous Izumi Group in Osaka Prefecture, West Japan. Monograph of the Association for Geological Collaboration in Japan 43: 25–32.Google Scholar
Tanimoto, M., Sato, M. & Takata, M., 2004. Reconsideration of a mosasaur lower jaw from Sobura, Kaizuka, Osaka Prefecture, southwest Japan. Chigakukenkyu 53: 99–103.Google Scholar
Tanimoto, M., Shinzyo, T. & Fujimoto, T., 2001. The first find of a mosasaurid tooth of the Upper Cretaceous Maastrichtian Izumi Group at Takinoike, Izumisano City, Osaka Prefecture, southwest Japan. Chigakukenkyu 50: 37–40.Google Scholar
Tanimoto, M. & Takata, M., 2002. A juvenile (?) tooth of Chlamydoselachus sp. from the Upper Cretaceous Maastrichtian Izumi Group of Hashiramoto, Hashimoto City, Wakayama Prefecture, southwest Japan. Chigakukenkyu 51: 131–134.Google Scholar
Tanimoto, M., Tani, M. & Minamino, M., 1998. Crocodilian-like teeth (? Mosäsauridae) from the Izumi Group (Upper Cretaceous Maastrichtian) of Sobura, Kaizuka-city, Osaka Prefecture, southwest Japan. Chigakukenkyu 47: 91–95.Google Scholar
Tanimoto, M. & Ueno, M., 2000. A small cervical vertebra of Mosasaurus sp. from the Upper Cretaceous Maastrichtian Izumi Group of Sobura, Kaizuka City, Osaka Prefecture, southwest Japan. Chigakukenkyu 49: 137–140.Google Scholar
Tanimoto, M. & Yokoi, T., 2005. A find of the dentary bone of a mosasaurid from Sobura, Kaizuka, Osaka Pref., southwest Japan and its significance. Chigakukenkyu 53: 207–212.Google Scholar
Tanimoto, M., Yokoi, , Takata, M., in press. A find of the fossil of the Mosasaurinae (Reptilia) from Izumi Group of Hakotsukuri, Hannan, Osaka Prefecture, Southwest Japan. Chigakukenkyu 54.Google Scholar
Tsujino, Y., 2004. Lithofacies and faunal assemblages of the Upper Cretaceous Izumi Group in Kanewari area, Kagawa Prefecture, Japan. Bulletin of the Tokushima Prefectural Museum 14: 1–13.Google Scholar