The function of apicobasal ridges in aquatic-feeding tetrapod dentition

Apicobasal ridges are longitudinal ridges of enamel present in several clades of aquatic-feeding predatory tetrapods, including Plesiosauria, Ichthyosauria, Mosasauridae, Crocodylia and Spinosauridae, as well as some early members of Cetacea. Although the repeated evolution of these dental ridges in unrelated clades suggests an adaptive benefit, their primary function in feeding remains unknown. Hypotheses range from increased tooth strength to improved prey puncture or removal efficiency, but these have never been quantitatively tested. This study utilizes Finite Element Analysis (FEA) to assess the impact of apicobasal ridges upon tooth crown strength in aquatic-feeding tetrapods. Drawing on morphometric data from fossilized tooth crowns, a set of digital models were constructed to calculate the performance of smooth and ridged tooth variants under simulated bite force loadings. The significant similarities in strain distribution patterns across models of the same tooth shape, regardless of the presence or morphology of ridges, indicates that apicobasal ridges have no impact on strain reduction within the tooth crown. Ultimately, these findings reject the improvement of crown strength as a potential function for apicobasal ridges in typical aquatic-feeding tetrapod dentition and form a framework for future research into the remaining hypotheses.