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Paleontological Research
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Abstract
Abstract.
We describe three well-preserved, articulated brittle stars from the Pliocene Hatsuzaki Formation, Hitachi Group of Ibaraki, central Japan, as a new species, Stegophiura takaisoensis. It differs from its congeners in having dorsal arm plates with a high ridge and large swollen disk scales. The only other previously described extinct species unambiguously assigned to Stegophiura is S. miyazakii from the Upper Cretaceous of Japan. The new species from the Pliocene significantly adds to the fossil record of the genus, representing the second extinct species known to date and filling part of the fossil record gap between the Upper Cretaceous and the Recent representatives. The specimens have the disk and arms in intact live position, without any signs of transportation before buried. We assume that they were buried alive in their original deep shelf to upper slope habitat by rapid channel fills.
We thank Yukio Yanagisawa (National Institute of Advanced Industrial Science and Technology) and Hisao Ando (Ibaraki University) for providing geological information of the fossil localities, and Yasunari Shigeta and Takuma Haga (National Museum of Nature and Science) for their kind help in preparation of fossils and taking photographs. We furthermore thank Christopher Mah (Smithsonian National Museum of Natural History), Sabine Stöhr (Swedish Museum of Natural History) and Benjamin T. Breeden III (National Museum of Nature and Science) for their helpful comments on an earlier version of this manuscript.
© by the Palaeontological Society of Japan
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