New Material of Schizotheriine Chalicothere (Perissodactyla, Chalicotheriidae) from the Xianshuihe Formation (Early Miocene) of Lanzhou Basin, Northwest China

Abstract A new schizotheriine mandible from the early Miocene Xianshuihe Formation in Lanzhou Basin, Northwest China is described here. Compared with other contemporaneous taxa, lower jaw most similar to Borissiakia betpakdalensis Kazakhstan based on mandibular morphology and dental features, except for a much smaller body size which hardly explained by intraspecific variation suggests it represents body-sized species of . The type specimen Phyllotillon huangheensis , same strata shares characters cheek teeth tapered anterior horizontal ramus. Differences between both are reflected height ramus, especially level symphysis, may be an expression sexual dimorphism. Therefore, mandibles Basin regarded as taxon, recognized occurrence chalicothere large perissodactyls suggest that certain amount open woodland was distributed across basin paleoclimate might have been more humid during Miocene.