A few lower cheek teeth of rhinocerotid, probably belonging to the same individual, from the upper Pliocene Tsubusagawa Formation in Ajimu, Oita Prefecture, southwestern Japan, are described. Morphologically, the Ajimu specimen is obviously distinguished from the subtribe Teleoceratina (Brachypotherium), Elasmotheriina (Elasmotherium) and a species of subtribe Rhinocerotina, Coelodonta, but it is similar to the Late Miocene species of tribe Aceratheriini and Miocene to Pleistocene species of Rhinocerotina. The Ajimu specimen is metrically similar to the lower cheek teeth of several species of Rhinocerotina, such as species of genus Diceros, Dicerorhinus, Dihoplus, Rhinoceros and Stephanorhinus. Therefore, the Ajimu specimen is identified as Rhinocerotina gen. et sp. indet. The previous works and present result reveal that this group was presented in Japan during mid-Pliocene. We also briefly summarize fossil records of the Japanese Pliocene rhinocerotid including footprints, suggesting that Pliocene rhinocerotid distributed in Japan through about 4.2 Ma to the end of the Pliocene. Japanese Pliocene rhinocerotids would be migrated from the Asian continent during the Early Pliocene or early Late Miocene when the proto-Japan connected with the Asian continent. However, more Japanese Pliocene specimens and detailed comparison with Asian species are needed to discuss this issue.

描述了一些来自日本西南部大分县阿治木上新世Tsubasagawa组的犀牛角下颌牙齿，可能属于同一个体。在形态上，阿吉姆标本明显区别于Teleoceratina亚种（Brachypotherium），Elasmotheriina亚种（Elasmotherium）和Rhinocerotina亚种，Coelodonta亚种，但它与Aceratheriini和中新世晚期中新世的Rhinocerotina亚种相似。Ajimu标本在尺度上类似于几种犀牛的下颊齿，例如Diceros属，Dicerorhinus属，Dihoplus属，犀牛和Stephanorhinus。因此，Ajimu标本被确定为Rhinoocerotina gen。等。indet。先前的工作和目前的结果表明，该小组是在上新世中期在日本提出的。我们还简要总结了日本上新世犀牛的化石记录，包括足迹，这表明上新世犀牛在日本分布到大约上新世末期约4.2 Ma。日本上新世与亚洲大陆相联系时，日本上新世犀牛将在上新世早期或中新世晚期从亚洲大陆迁移。但是，需要更多的日本上新世标本以及与亚洲物种的详细比较来讨论这个问题。