Incisor fossils of Aprotodon (Perissodactyla, Rhinocerotidae) from the Early Miocene Shangzhuang Formation of the Linxia Basin in Gansu, China
Abstract Lower incisor fossils of Aprotodon lanzhouensis collected from the Early Miocene deposits in the Linxia Basin, are described in this paper. Characteristically, they are relatively robust and strongly curved. The discovery of the new specimens causes the occurrence of Aprotodon across the Oligo-Miocene boundary in the Linxia Basin to be completely confirmed. The chronological and geographical distribution of Aprotodon was essentially coincident with that of giant rhinos, but the localities and numbers of individuals recording Aprotodon were relatively rare. The mandibular morphological function of Aprotodon suggests that this form lived in sparse riparian mosaics within the arid part of northwestern China, and South and Central Asia from the Late Eocene to the Early Miocene. Aprotodon experienced total extinction before the Middle Miocene, which possibly resulted from climatic changes. The pattern of occurrence of Aprotodon also indicates that the climatic and environmental conditions of the Linxia Basin during the Early Miocene were similar to relatively open woodlands of the Late Oligocene, in contrast to dense forests of the Middle Miocene.
Key words Linxia Basin, Gansu, China; Early Miocene; Rhinocerotidae, Aprotodon