東京都あきる野市産Stegodon臼歯化石の再検討と日本の鮮新統産大型Stegodonの種名について

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The fossil tooth of Stegodon from Ajiro, Akiruno-shi, which was originally reported by Naora (1955) and later described by Mishima & Miyazaki (1985) under the name of S. orientalis, is now preserved in Kanagawa Prefectural Museum of Natural History (#KPM-NNV000008). Although the fossil tooth has been believed to be derived from the Pleistocene terrace deposits, we were able to confirm its exact locality, 200m downstream from the Ajiro Bridge in the Akigawa River, where the Lower Member of the Kasumi Formation (Late Pliocene) crops out. The reexamination of KPM-NNV000008 indicates that it evidently belongs to the large type Stegodon in Japan, showing the following characters; 1) number of ridges: 7; 2) width of crown: 79.2mm; 3) ridge frequency 3-4.5 ridges/10cm; 4) enamel folding: coarse and irregular; 5) enamel thickness: 5.6-6.5mm; 6) tooth class: Lower Right M2 and 7) stratigraphic horizon: Lower member of the Kasumi Formation (Late Pliocene). The large type Stegodon found in Japan was initially described by Matsumoto (1941) as Stegodon clifti miensis from Mie Prefecture, central Japan. Afterward, Sawamura et al. (1979) described Stegolophodon shinshuensis as a new species from Nagano Prefecture, central Japan. Taruno (1991) allocated the latter species to the genus Stegodon and regarded it the available name to the large type Stegodon in Japan. We agree that the large type Stegodon in Japan is distinctly a species and the former is identical with the latter. However, Matsumoto's S. c. miensis is doubtless valid according to the Code of Zoological Nomenclature (Article 45.1). Therefore S. shinshuensis should be regarded as a junior synonym of Stegodon miensis (new combination), of which the holotype is a lowerjaw with M3 (NSM-PV2193: National Science Museum, Japan).
国立科学博物館の論文
2002-12-25

東京都あきる野市産Stegodon臼歯化石の再検討と日本の鮮新統産大型Stegodonの種名について

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