New material of Amphicyon zhanxiangi from laogou, linxia basin suggests a possible southern dispersal with increasing omnivory

The fossil records of large amphicyonids in Asia are rare and fragmentary, and their evolution and dispersal are also unclear. Here we present new dental material from Laogou, Linxia Basin, Gansu Province, belonging to the Hujialiang Formation, Middle Miocene. The new material is very similar to Amphicyon zhanxiangi from the Dingjia'ergou fauna of the Zhang'enbao Formation, Tongxin, Ningxia, and can be referred to this species. It is younger than the Tongxin material and differs from the latter by having better-distinguished cusps in upper molars, supporting this species is probably the ancestor to the omnivorous Arctamphicyon found in the Siwaliks, Yuanmou, and the Lower Irrawaddy. This lineage might immigrate to southern and southeastern Asia by the Late Miocene, and adapted to an increasing omnivorous diet due to more available plant material in tropical and subtropical regions.