New discovery of Early Pleistocene orangutan fossils from Sanhe Cave in Chongzuo, Guangxi, southern China

Twenty-eight (28) isolated orangutan fossil teeth are reported in this paper, which are newly discovered from Sanhe Cave in Chongzuo Ecological Park of Guangxi in southern China. The geological age is Early Pleistocene, approximately 1.2 Ma, based on the mammal fauna and paleomagnetic stratigraphy. The tooth crown areas are within the range of extant orangutans and subfossil orangutans from Indonesia. However, by comparing the distribution of the crown areas, the sample from Sanhe has crown areas that fall above the mean value of extant orangutans and Holocene orangutans. Morphological differences between the Sanhe, subfossil and extant orangutans are difficult to discern, although the occlusal wrinkles of the postcanine teeth of the fossil orangutans from Sanhe are less numerous but coarser than that of extant orangutans. The fossil orangutans from Sanhe are smaller than those from other caves from Chongzuo Ecological Park, and are slightly larger than samples from Mulanshan Cave. We conclude that the fossil orangutan teeth from the Early Pleistocene of Sanhe Cave are provisionally classified as Pongo pygmaeus weidenreichi, and better evidence is needed to interpret the evolution and taxonomy of the fossil orangutans in southern China.