Heterodonty in the teeth of the turiasaurian sauropod from Angeac-Charente (Early Cretaceous, southwestern France): Comparison of anatomical and geometric morphometric approaches.

Sauropod teeth are often described within a taxonomic framework, with few studies focusing on heterodonty or intraspecific morphological variation. The Lagerstätte of Angeac-Charente has yielded 167 heart-shaped isolated teeth from a single turiasaurian species. Observations of this material during its collection in the field, preparation, and recording in the collections suggest the presence of possible heterodonty in this species. In this study, we analyze this heterodonty using both comparative anatomy and 3D geometric morphometric analyses coupled with machine learning algorithms. Our principal objective is to determine whether one of the two approaches-quantitative or qualitative-is more effective than the other and whether they can be complementary studying heterodonty. The results confirm the presence of heterodonty, with five different morphotypes, which correspond to premaxillary, maxillary anterior, maxillary posterior, anterior dentary, and posterior dentary teeth. An anteroposteriorly decreasing size gradient in the jaw is observed. Qualitative comparative anatomy is the quickest method, with few conflicts in morphotyping, while quantitative approaches might resolve ambiguities through more precise and replicable analyses. Together, these methods provide complementary insights and allow retrospective positioning of teeth within the jaw. This study, therefore, allows for the reliable assignment of teeth to specific regions or positions in turiasaurian sauropods. Such assignment work is also necessary for many other taxa, and this method will, therefore, be useful for future research. Indeed, it is fully applicable to other sauropod taxa, theropods, or crocodilians.