The Anatomy of a Mamenchisaurid Tooth Informed by Digital Reconstruction

The detailed dental anatomy of sauropod mamenchisaurids remains largely unexplored. Here, we describe a well-preserved isolated sauropod tooth from the Upper Jurassic Qigu Formation of the Turpan-Hami Basin, Xinjiang, using high-resolution Micro-CT and three-dimensional reconstruction to investigate its internal anatomy. This tooth exhibits a diagnostic feature of Mamenchisauridae, specifically the presence of marginal denticles restricted to the mesial margin. CT scan data provide novel insights into mamenchisaurid dental anatomy and present the first three-dimensional enamel distribution in sauropod teeth. The lingual ridge forms from thickened enamel and dentine, whereas the lingual boss arises solely from dentine expansion. A labiolingual enamel thickness asymmetry appears in the apical region, convergent with certain neosauropods. The pulp cavity shows a distinct volumetric transition, expanding basally into a bulbous root canal and appearing as a labiolingually compressed lamina structure in the crown. Taxonomic comparison indicates that this tooth represents a mamenchisaurid lineage distinct from the previously only known sauropod tooth from the Qigu Formation. Our study supports diverse sauropod assemblages in the Qigu Formation and provides new anatomical evidence for understanding sauropod dental evolution.