A new molar from the Middle Pleistocene hominid assemblage of Yanhuidong, Tongzi, South China

1988年,贵州省博物馆对桐梓岩灰洞的支洞进行了最后一次发掘。2014年,在洞内第四层堆积物中鉴定出逾2000件的动物牙齿化石,以及一枚古人类上颊齿(编号:TZ-1)。1991年,铀系法测定这些次生堆积物的沉积年代约为距今24万年。本文运用高精度CT(巴黎自然历史博物馆)对TZ-1的釉质齿质界面(EDJ)和牙髓腔几何形态进行了分析。TZ-1的冠面形态有如下特征:次尖小且在远中舌侧不发育,咀嚼面轮廓呈四边形,颊舌径稍大过近中远中径,原尖舌侧齿带发育,齿尖从大到小依次为原尖、后尖、前尖和次尖。TZ-1牙髓腔的髓角与其釉质齿质界面以及釉质表面的形态都具有相关性。TZ-1的形态与M1虽有相似之处,但完全不同于1983年出土于同一层位的另两颗M1;其应被鉴定为dm2,并可被归入中中更新世的中国直立人支系。岩灰洞上臼齿PA 875的形态与建始龙骨洞PA 1279和周口店直立人等古老型直立人相似。岩灰洞另一枚刚萌发的臼齿PA 874具有凸出的次尖和长菱形的外廓,接近于爪哇型直立人Sangiran NG 91-G10;这也是智人和尼安德特人的共有衍征。但PA 874的冠面仍保留了亚洲型的齿带,因而被归入人属未定种。因出土自次生堆积,岩灰洞的三种古人类类型未必曾同时并存,但却揭示了华南地区人类演化进程中的多样面貌。

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 （vltome× 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 It. erectus living only in China （north-south axis Shanxi, Hubei, Hunan, Guandong and Guizhou provinces）. The morphology that predicts M~, does not match the two M~ 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.