Uncovering the biomechanical disparity of Cretaceous marine reptile feeding via finite element analysis

During the Late Cretaceous, two marine reptile groups (mosasaurs and polycotylids plesiosaurs) regulated oceanic trophic chains, diversifying in the wake of the extinction of both ichthyosaurs and pliosaurids. Whereas a series of studies have analysed tooth morphology and guild structuration among marine reptiles, biomechanical performances have rarely been assessed. Such biomechanical analyses have the potential reveal the functional disparity of the main tetrapod predators of the Late Cretaceous. This study represents the first attempt to compare biomechanical performance of multiple marine reptile clades using Finite Element Analyses. We investigated biting mechanics of mandibles through two gape angles and two different biting points. Results from mechanical efficiency, Von Mises stress along the jaw, and internal energy reveal niche partitioning among sympatric marine reptile species. One ecomorphotype is occupied by polycotylids, which have a gracile snout, narrow rostrum, and low mechanical efficiency and high internal energy. Mosasaurs occupy at least two distinct ecomorphotypes, yet with more robust mandibles, higher mechanical efficiency, and lower internal energy values. These quantitative results confirm qualitative assessments of Late Cretaceous marine reptile palaeoecology.