Taxonomic identification of isolated theropod teeth: the case of the shed tooth crown associated with Aerosteon (Theropoda: Megaraptora) and the dentition of Abelisauridae

Abstract Shed teeth are usually the most abundant theropod material on a dinosaur fossil site and are constantly reported in the literature. Although new quantitative techniques have emerged to identify isolated theropod teeth with better accuracy, they remain difficult to assign to a certain family-level or genus-level taxon because of the presence of rampant homoplasy in their morphology and the lack of thorough descriptions. Here we test three methods to investigate the phylogenetic position of a tooth previously considered to be part of the holotype of the megaraptoran Aerosteon riocoloradensis (MCNA-PV-3137): a cladistic analysis performed on a dentition-based data matrix scored across 105 theropod species and using a backbone topology as constraint, as well as discriminant and cluster analyses conducted on a dataset of non-avian theropod crown measurements. Even though the cladistic technique appears to be the most reliable method to investigate the phylogenetic affinities of theropod teeth, we recommend using the three techniques conjointly to corroborate the identification of isolated dental material. The results of the cladistic and discriminant analyses support the assignment of the tooth associated with MCNA-PV-3137 to an abelisaurid theropod. It should therefore be excluded from the holotype of Aerosteon. A thorough description of the dental anatomy of Abelisauridae is also provided. The current study is the first to evaluate different methodological tools to identify isolated theropod teeth. With the added detailed description of the dental anatomy of Abelisauridae, it will also assist future authors to investigate the systematic palaeontology of isolated theropod teeth with more confidence.