Assessing the biomechanics of sabre teeth through the trade-off between puncture performance and breakage resistance

“Sabre teeth” – elongate blade-like canines – have evolved repeatedly throughout mammalian history. However, the functional underpinnings of this reoccurring morphology remains unclear. To effectively bite into prey, all canine teeth must strike a balance between being slender enough to reduce puncture force, while being robust enough to resist breakage. We explored this trade-off in sabretooth canines by comparing these against teeth from living carnivores, integrating three-dimensional shape data with mechanical performance metrics within a functional optimality framework. Canine shape was captured via 3D geometric morphometrics in a sample representing 67 non-sabre and 20 sabretooth species. We then quantified two mechanical performance metrics in a subset of teeth, applying finite element analysis to model tooth stress and undertaking physical puncture tests to quantify puncture force. These data were combined using a Pareto rank approach, constructing an adaptive landscape to assess optimality. Extreme sabretooth forms, like Smilodon, Barbourofelis, and Thylacosmilus, exhibit a combination of curvature and slenderness not found in our extant dataset, resulting in the highest stress values and lowest puncture forces of all teeth. Interestingly, these forms occupy a small peak of optimality in the adaptive landscape which is separated by a valley from another larger peak of straighter canines with varying robusticity. Our combined approach reveals new aspects of sabretooth biomechanics, providing fundamental insights into the adaptive bases for morphological diversity in pointed