Paleontological and paleogeographical studies of the first Tertiary small mammal fauna from Japan.

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The first Tertiary small mammal fauna in Japan (=Dota local fauna) from Dota, KaniCity, Gifu Prefecture was composed of 2 orders, 4 families, and 4 genera, when the present study started. Research and excavations by this study added one insectivore, two rodents, two carnivores, and one artiodactyl ; therefore, the Dota local fauna is now composed of 5 orders, 7 families, and 9 genera. They are, Plesiosorex sp. (Insectivora), cf. Amphilagus sp. (Lagomorpha), Youngofiber sinensis, Anchitheriomys n. sp., ? Pseudotheridomys sp. or Pentabuneomys sp., Eomyidae n. gen. et n. sp. (Rodentia), Ursoidea gen. et sp. indet., Musteroidea gen. et sp. indet. (Carnivora), and Traguridae gen. et sp. indet.(Artiodactyla).Although the new genus of Eomyidae is known only from Czech and Gifu Pref. and only by a single specimen from each locality, it is very important in order to study the paleobiogeographic relationship between Europe and Asia.Out of 6 genera of small mammals, 5 genera are common between Do … More ta and Europe, indicating that the faunal interchange between Europe and Asia was extensive. 3 genera are common between Dota and North America, indicating that the faunal interchange between North America and Asia was fairly successful. These facts suggest that faunal interchange among Europe, Asia, and NOrth America during the early to middle Miocene occurred more widely among wide variety of mammals.Dota local fauna is similar to "Merkur-Nord" fauna in Czech in the faunal composition. The age of the latter is MN3a of European land mammal age and is about 22 to 20 million years ago (MA). The Nakamura Formation that yielded the Dota local fauna does not yield proboscidean fossils, but the proboscideans have been commonly known from the overlying Hiramaki Formation. Proboscideans appear in MN4 (ca. 18 MA) in Europe. Thus, the Dota local fauna can be correlated with MN3 in Europe. Fission-track ages obtained from the Nakamura Fm. Suggest that the age of Dota local fauna is about 21 to 19 MA which is somewhat older than previously thought. Less