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Journal of Micropalaeontology An open-access journal of The Micropalaeontological Society
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Volume 27, issue 2
J. Micropalaeontol., 27, 135–146, 2008
https://doi.org/10.1144/jm.27.2.135
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 4.0 License.
J. Micropalaeontol., 27, 135–146, 2008
https://doi.org/10.1144/jm.27.2.135
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 4.0 License.

  01 Nov 2008

01 Nov 2008

Taxonomy and palaeobiogeographical significance of four new species of Semicytherura (Ostracoda, Crustacea) from the Early Pleistocene Omma Formation of the Japan Sea coast

Hirokazu Ozawa1 and Takahiro Kamiya2 Hirokazu Ozawa and Takahiro Kamiya
  • 1Department of Geology, National Museum of Nature and Science, Tokyo, 3-23-1 Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan (e-mail: )
  • 2School of Natural System, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan

Keywords: ostracods, Semicytherura, Japan Sea, Plio-Pleistocene, extinction

Abstract. The genus Semicytherura (Ostracoda, Crustacea) is distributed widely in shallow-sea areas of the Northern Hemisphere and occurs commonly in Pliocene and Pleistocene strata along the Japan Sea coasts. Four new species -Semicytherura robustundata sp. nov., Semicytherura subslipperi sp. nov., Semicytherura leptosubundata sp. nov. and Semicytherura tanimurai sp. nov. - are described from the Early Pleistocene Omma Formation, central Japan. These species are palaeobiogeographically significant in the history of species diversity changes in Japan Sea benthic fauna during the Late Cenozoic. The geological and geographical occurrences suggest that these four species originated within the Japan Sea from the Late Pliocene, including one species that diversified by heterochronic evolution, and were endemic to the Japan Sea. They became extinct within this sea during the Early Pleistocene.

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