Abstract: The last excavation of the small Yanhuidong gallery, Tongzi district, Guizhou Province, South China, was conducted by the Guizhou Provincial Museum in 1988. Fossiliferous layer IV of the endokarstic fill provided again more than 2,000 teeth with a new hominin upper molar referenced as TZ-1 in 2014. This secondary deposit has been dated 240 ka by Uranium Series in 1991. The description of the molar was completed by an analysis of the enamel-dentine junction (EDJ) and the topography of the pulp cavity using high-resolution μCT (v|tome|x L240-180) of the AST-RX platform, National Museum of Natural History, Paris, France. The crown is characterized by a small hypocone without disto-lingual development, a trapezoidal shape of the occlusal contour, the bucco-lingual length slightly greater than the mesio-distal one, a large lingual cingulum on the protocone, and the cusps decrease in the order protocone, metacone, paracone and hypocone. The shape of the horns and of the bud horns from the pulp cavity are correlated with the morphology of the enamel-dentine junction (EDJ) and the outer enamel surface (OES). The tooth is a second primary molar (dm2) assigned to a mid-Middle Pleistocene lineage of H. erectus living only in China (north-south axis Shanxi, Hubei, Hunan, Guandong and Guizhou provinces). The morphology that predicts M1, does not match the two M1 collected in 1983 in the same layer. PA 875 is close to the oldest pattern Jianshi PA 1279 also found at Zhoukoudian (Hebei and Hubei provinces). The germ PA 874 with its protruding hypocone and a rhomboidal shape is similar to the Javanese pattern Sangiran NG 91-G10; these are derived features shared in a certain way with H. neanderthalensis, but the crown keeps the Asian cingulum and is classified as Homo incertae sedis. These three morphological patterns are not necessary contemporaneous but they lift a veil on human settlements in South China before the redeposited faunal assemblage.

Key words: Tongzi; Deciduous molar; Hominin; South China; Middle Pleistocene