Complex enamel ridges have evolved multiple times on the teeth of unrelated aquatic predators, including extinct marine reptiles, toothed whales, crocodilians, and aquatic-feeding dinosaurs. Their appearance in such a wide range of groups suggests that they are a specialized structure adapted to perform specific functions in the capture and/or processing of prey, although these functions are unknown. This study used computer modeling to apply bite force simulations to a set of digital tooth models in order to identify whether the ridges strengthened the tooth. These models enabled us to visualize how bite force stress is distributed around smooth teeth compared with ridged teeth, including a range of ridge types. Our results suggested that the ridges do not strengthen the tooth crown overall, indicating that they may instead serve another role in prey handling.

Apicobasal ridges are longitudinal ridges of enamel that are particularly common in several clades of aquatic-feeding predatory amniotes, 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 is debated. Hypothesized functions range from increasing tooth strength to improving 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 amniotes. Drawing on morphometric data from fossilized tooth crowns, a set of digital models was constructed to calculate the performance of smooth and ridged tooth variants under simulated bite force loadings. The similarities in overall stress distribution patterns across models of the same tooth shape, regardless of the presence or morphology of ridges, indicate that apicobasal ridges have little impact on stress reduction within the tooth crown. Ultimately, these findings suggest that apicobasal ridges have a minimal role in improving crown strength and form a framework for future research into the remaining hypotheses.