东亚中更新世古人类在头骨、下颌骨、牙齿等解剖部位表现出不同程度的形态多样性,中期成员代表为直立人,而晚期成员的演化地位具有较大争议。为进一步了解东亚中更新世古人类内部的形态变异特点和为东亚中更新世晚期古人类分类提供依据,本文使用微分同胚的表面匹配（Diffeomorphic Surface Matching, DSM）和形态测量图（Morphometric map）对下颌第二臼齿（M₂）釉质-齿质连接面的形状和齿冠侧面釉质厚度分布模式进行了量化分析。结果显示：1）东亚中更新世古人类与晚期人属成员（尼安德特人和现代人）存在较明显的形态差别;2）该时段晚期的东亚古人类相对中期直立人在侧面釉质厚度分布规律上具有独特性,并在釉质-齿质连接面的三维形状上与晚期人属成员更加接近。本文在以往对东亚中更新世古人类牙齿内外结构单个性状研究的基础上,使用三维形态测量方法进一步量化了M₂釉质-齿质连接面三维形状和侧面釉质厚度分布模式两项重要特征的变异特点,这对未来该时段同类型牙齿的形态鉴定以及解决东亚中更新世晚期古人类的分类地位具有一定意义。

Morphological diversity has been revealed in the cranial, mandibular, and dental materials of East Asian Middle Pleistocene hominins, and the taxonomy of later members is uncertain. In order to further apprehend the morphological variability of East Asian Middle Pleistocene hominins and provide evidence for the taxonomy of the later members, the present study conducted three-dimensional morphometric analyses, including morphometric map of lateral enamel thickness and diffeomorphic surface matching of enamel-dentine junction (EDJ), on the lower second molars. The results indicate that: 1) East Asian Middle Pleistocene hominins could be distinguished from both Neanderthals and modern human; 2) East Asian late Middle Pleistocene hominins displayed special distribution pattern of lateral enamel thickness and a more progressive EDJ shape relative to mid-Middle Pleistocene Homo erectus. The present study quantifies two important morphologies and their variability, i.e., distribution pattern of enamel thickness and EDJ shape, in addition to the individual dental traits studied by previous works. It will provide further insight into the taxonomies of East Asian late Middle Pleistocene hominins and help designating isolated teeth from the same period into their correct morphological groups.