Abstract: An isolated upper first premolar (P3) of Home erectus was recently recognized from the fossil collection excavated from the Hexian site, Anhui. The present work carried out studies on both size and morphology of this new tooth. After comparing it with related specimens, the new P3 was found to be significantly large in the crown size, and represent the largest one among fossil teeth found in mainland of China, except for another P3 discovered at the same site. The large crown indicated a relatively primitive state. Based on the shape of crown outline and the pattern of cusp arrangement, the new P3 did not discriminate from those of other H. erectus. However, the deeply-furrowed mesial vertical groove on the buccal face clustered the new P3 with those of Asian H. erectus. This type of tooth underwent clear evolutionary changes in its size, transverse crest, buccal vertical groove, root number, the shape of crown outline, and the pattern of cusp arrangement. These P3 of Chinese H. erectus varied obviously in these features. The size and morphologies of the new Hexian tooth were relatively primitive within the group of Chinese H. erectus. Previous studies assumed that the skull of the Hexian fossil hominin displayed some features more progressive than those of Zhoukoudian H. erectus. However, this assumption was not supported by the present study. On the contrary, some traits of these premolars of Hexian H. erectus were found to be more primitive than those of Zhoukoudian H. erectus. The new P3 of Hexian H. erectus will play a significant role in exploring the origin and territorial variation of Chinese H. erectus.

Key words: Hexian; H. erectus; Upper first premolar; Size; Morphology