Abstract
In the present study, 1212 isolated fossil microtine teeth from Ando Quarry at Ofukudai karst plateau, Yamaguchi Prefecture, Japan, were examined for identifictation. Among them 280 specimens were rootless molars, and the other 932 specimens were molars with root. The former were identified as Microtus epiratticeps YOUNG 1934, which is an element of the Choukoutien fossil fauna. The taxonomic validity of M. epiratticeps YOUNG 1934, was discussed in some detail. The molars with roots were referred to Clethrionomys sp. at the present stage of study. In the genus Clethrionomys, they belong to nageri group of HINTON (1926). More precise identification is an open problem.
By adding at least a new microtine fossil species of the Choukoutien fossil fauna, the present study gave more evidence to support the view already stated that the formation of the Ofukudai and the adjacent karst plateaus represents the boundary between the late-middle and early-upper Pleistocene in Japan, i. e., the age of Stegodon-Palaeoloxodon faunal transition.
