重庆上二叠统龙潭组的海相地层中新发现一枚牙齿化石。该化石长9 mm, 呈扁尖锥状, 表面具有细沟槽, 横截面具有迷齿结构, 齿质折叠的程度很高。将其形态和迷齿结构与二叠、三叠纪的牙齿进行比对, 推测为早期四足类的獠牙, 很有可能属于离片椎类中的全椎类。本文总结了过去对迷齿的研究, 指出了早期四足类迷齿折叠程度的分布规律: 同一个体的獠牙折叠程度比非獠牙复杂; 在同一牙齿中, 折叠程度越靠近齿尖越简单; 爬行形类折叠程度较简单; 离片椎类折叠程度从简单到复杂都有, 其中部分全椎类极其复杂。另外, 对时代相近的标本HGM 41HIII0447的归属也进行了讨论, 认为其更可能是一枚离片椎类的獠牙。基于对我国二叠纪的四足类的回顾, 这枚在重庆发现的牙齿化石是四足动物在中国南方二叠纪的首次记录, 为二叠纪华北—华南的陆地连接提供了新的证据。

A fossil tooth is reported from the marine strata of the upper Permian Longtan Formation in Chongqing. The tooth, measuring 9 mm long, is flattened cone in shape, with striped grooves on its surface. A cross-sectional view reveals a labyrinthine structure with high degree of dentine folding. Based upon comparisons of its morphology and labyrinthine structure with those of known Permian and Triassic teeth of major lineages of early tetrapods, this specimen is likely a tusk of a stereospondyl of Temnospondyli. In this paper, we summarize previous works on labyrinthine teeth, and identify the following patterns on dentine folding among early tetrapods: (1) tusks exhibit more complex folding than other teeth within the same individual; (2) folding complexity decreases towards the tip of the tooth; (3) reptiliomorphs display simple folding; and (4) folding in temnospondyls ranges from simple to extremely complex particularly in some stereospondyls. Additionally, based on this study, a specimen (HGM 41HIII0447) of a similar age is more likely a tusk of a temnospondyl. Through comparisons with other Permian tetrapods from China, the tooth described here represents the first Permian tetrapod record in southern China. This discovery provides new evidence for a land connection between North China and South China during the Permian .

重庆市技术创新与应用发展专项重点项目(CSTB2023TIAD-KPX0098)资助