Dental variability and distinguishability in Mosasaurus lemonnieri (Mosasauridae) from the Campanian and Maastrichtian of Belgium, and implications for taxonomic assessments of mosasaurid dentitions

Mosasaurus lemonnieri is a mosasaurine mosasaurid first unearthed from the lower Maastrichtian of the Mons Basin, southern Belgium. Even though numerous well-preserved specimens have been attributed to the taxon, the knowledge of its anatomy is surprisingly poor and merely limited to some general characteristics. Here I describe the morphology of the marginal dentition of M. lemonnieri based on the holotype and 14 referred individuals originating from the upper Campanian and Maastrichtian of Belgium. The dental variability is assessed through linear discriminant analyses aimed to appraise the tooth crown distinguishability between (1) individuals, (2) tooth-bearing elements (premaxillae, maxillae, and dentaries), and (3) within particular jaw regions (anterior, middle, and posterior). The overall dental distinguishability between individuals was, expectedly, poor though the rates of correctly classified teeth differed for particular specimens, which can have taxonomic implications. The premaxillary and maxillary teeth were inferred to be more distinguishable than the dentary teeth. The dental distinguishability of M. lemonnieri is further compared to that of other sympatric and potentially sympatric taxa. The use of mosasaurid dental measurements substantially facilitates the comparisons of mosasaurid teeth on both inter- and intraspecific scale, increasing the accuracy of the studies appraising the patterns of mosasaurid dental evolution.