Functional optimality underpins the repeated evolution of the extreme “saber-tooth” morphology

• Published in: Current biology Vol. 35; no. 3; pp. 455 - 467.e6
• Main Authors: Pollock, Tahlia I., Deakin, William J., Chatar, Narimane, Milla Carmona, Pablo S., Rovinsky, Douglass S., Panagiotopoulou, Olga, Parker, William M.G., Adams, Justin W., Hocking, David P., Donoghue, Philip C.J., Rayfield, Emily J., Evans, Alistair R.
• Format: Journal Article Web Resource
• Language: English
• Published: England Elsevier Inc 03.02.2025; Elsevier BV
• Subjects: Animals; Biological Evolution; canine; Carnivora; Cuspid - anatomy & histology; Cuspid - physiology; form-function; functional morphology; Life sciences; mammal; optimality; puncture performance; saber-tooth; Sciences du vivant; Tooth - anatomy & histology; Tooth - physiology; tooth biomechanics; tooth morphology; functional morphology; Carnivora; optimality; mammal; puncture performance; tooth morphology; canine; saber-tooth; tooth biomechanics; form-function
• ISSN: 0960-9822; 1879-0445; 1879-0445
• DOI: 10.1016/j.cub.2024.11.059

“Saber teeth”—elongate, blade-like canines—are a classic example of convergence, having evolved repeatedly throughout mammalian history. Within canine teeth, there is a trade-off between the aspects of shape that improve food fracture and those that increase tooth strength. Optimal morphologies strike a balance between these antagonistic functional criteria. The extreme saber-tooth morphology is thought to confer functional advantage for more specialized predatory adaptations and optimization; however, the adaptive bases underpinning their evolution remain unclear. To determine whether saber-tooth shape reflects selection for functionally optimal morphologies, we generated a morphospace of the 3D shape of 70 non-saber and 25 saber-tooth species, a subset of which were used to quantify functional metrics of puncture performance and breakage resistance. These data were combined using a Pareto rank-ratio algorithm to evaluate optimality. We demonstrate that extreme saber-tooth morphologies are functionally optimal, occupying a localized peak in our optimality landscape. Unlike other optimal canine morphologies, extreme saber teeth optimize puncture performance at the expense of breakage resistance. This identifies functional optimality as a key driver underpinning the repeated evolution of this iconic tooth. [Display omitted] •There is continuous morphofunctional diversity in saber-tooth canines•Extreme saber teeth are optimal, enhancing puncture but reducing breakage resistance•Functional optimality drives convergent evolution of extreme saber-tooth morphology•Increased specialization of extreme saber forms may act as an evolutionary ratchet Saber teeth are a classic example of convergence, having evolved repeatedly throughout mammalian history. Using 3D morphometrics, biomechanical testing, and a Pareto optimality analysis, Pollock et al. identify functional optimality as a key driver underpinning the repeated evolution of extreme saber-tooth morphologies.