A Jurassic Tibetan theropod tooth reveals dental convergency and its implication for identifying fragmentary fossils

Abstract

<p><b>The Tibetan Plateau is among the least explored areas in terms of dinosaur paleontology in the world. Here, we report a dromaeosaurid-like tooth from the Middle Jurassic Dongdaqiao Formation at the eastern part of the plateau. The tooth exhibits dromaeosaurid dental features such as the absence of constriction at the cervix, a relatively small crown-to-base ratio, a strongly recurved apex, and it lacks large transverse and marginal undulations. Parsimonious phylogenetic analyses using both dentition-based and complete morphological matrices support a dromaeosaurid affinity for this tooth and place this Tibetan theropod as the sister taxon to</b> <i><b>Velociraptor</b></i><b>. However, Bayesian tip dating analyses based on the velociraptorine affinity of the Tibetan tooth place the majority of the diversifications of early-diverging Paravian within �C or earlier than �C the Middle Jurassic, which conflicts with the paravian fossil record. Furthermore, our discriminant analysis based on morphometric data places the Tibetan theropod within Metriacanthosauridae. These results may suggest that the broad resemblance between the Tibetan specimen and velociraptorine teeth is due to convergent evolution. Based on our results, other dromaeosaurid-like teeth reported from the Middle and Late Jurassic deposits throughout Eurasia could potentially be from non-dromaeosaurids. This study suggests the presence of an early diverged theropod lineage with a wide geographical distribution and potentially a dromaeosaurid-like dietary niche. This study also highlights the importance of using multiple lines of data to identify fragmentary fossils.</b></p>