Multi-gape angle 3D biomechanical modelling of the cat-like mandible reveals nuances of sabertooth functional morphological evolution

peer reviewedThroughout geological times, multiple clades converged in craniodental morphology with true cats (Felidae), notably nimravids and thylacosmilids. In those groups, the so-called sabre-tooth phenotypes is a textbook example of convergent evolution often interpreted as an adaptation for subduing large prey. This conventional framework implies homogenous ecologies for all sabre-toothed clades, failing to consider the functional differences between scimitar-toothed, dirk-toothed and ‘mosaic’ taxa, as well as the numerous species that convergently evolved smaller, conical canines. This simplified interpretation of the seemingly unique saber-tooth condition is reinforced by a reduced taxonomic sampling in some studies, often focusing on a couple of well-known, highly derived taxa or using highly-simplified morphological models. Moreover, most biomechanical analyses focus on biting scenarios at small gapes (25 to 30°), a classical angle for modern carnivora that is however ill-suited to test for subduction of large prey by sabre-toothed taxa. Here, we thoroughly analyse the biting biomechanics of sabre-toothed and non-sabre-toothed taxa by applying Finite Element Analyses (FEA) on the largest dataset ever assembled of cat-like placental mandible 3D models, under a variety of gape scenarios. We performed muscle-induced biting simulations on 17 different taxa, at three different angles (30°, 60° and 90°), and on multiple biting points to evaluate their adaptation to bite at large angle; the total number of biting simulations we performed reaches 1,074. While our results show a clear adaptation of extreme sabre-toothed taxa to bite at larger angles in terms of Von Mises stress, other performance variables (mechanical efficiency and adjusted strain energy) display surprising similarities between sabertoothed and non-sabertoothed forms between the different angles tested, highlighting a continuous rather than bipolar spectrum of hunting methods in cat-like carnivorans