Abstract: As the only living great ape in Asia, the orangutan was ever widely distributed throughout Southeast Asia and southern China, but preserved fossil materials include mainly isolated teeth. Because of this limited data from external dental characteristics such as shape and size, classification and evolution of orangutans is controversial and not agreed upon by all the scientists. Many studies show that tooth growth and development is a potential tool for taxonomy and phylogeny. In this work, Pleistocene orangutan teeth from Guangxi, were used to create histological slides in order to measure enamel daily secretion rates (DSR). Our results showed that cuspal enamel daily secretion rates were in the range of 2.32-6.88μm/d, with the average DSR 4.61μm/d. These results were then compared with other living great apes and modern humans, all of which should help in determining orangutan phylogeny and taxonomy.

Key words: Orangutan; Pleistocene; Dentition; Secretion rate