A review of the taxonomy, biostratigraphy and paleobiogeography of Plio-Pleistocene rhinoceroses in Japan

The Rhinocerotidae were distributed in Eurasia and Africa during the late Neogene. In particular, the subtribe Rhinocerotina which includes the living species, diversified during the Plio-Pleistocene in Eurasia. Japan, which is situated in Far East Asia, has also yielded Plio-Pleistocene rhinocerotids, but their taxonomic position has not been revised since their first descriptions. Considering recent taxonomic revisions of many Eurasian Rhinocerotidae, it is necessary to also revise the Japanese remains. Here, taxonomy and fossil records of the Plio-Pleistocene Japanese rhinocerotids are reviewed. A total of 16 bones and teeth remains have been found from the mid-Pliocene to the middle Middle Pleistocene. Three Pliocene rhinocerotids are identified as Rhinocerotina gen. et sp. indet. In the earliest Pliocene, the close relative of the Japanese Pliocene rhinocerotid migrated from continental Asia. Stephanorhinus kirchbergensis was distributed in central to southwestern Japan during the middle Middle Pleistocene. In addition, indeterminate species were also present in the Early to Middle Pleistocene. The Late Pleistocene fossil record is uncertain due to the lack of stratigraphic and chronological data. Japanese S. kirchbergensis immigrated from the continental Asia (middle part of China) at ca. 0.65 Ma with a species of Stegodon together.