Evolution of the sabertooth mandible: A deadly ecomorphological specialization

Saber-toothed cats were armed with formidable weapons. They evolved a number of highly derived morphological features, most notably a pair of extremely long upper canines, which makes them unique within the felid family. Although the sabertooth character evolved several times among carnivorous mammals, sabertooth clades mostly had disjunctive occurrences both in space and time, and no sabertooth is alive today. We studied the rates of phenotypic and taxonomic diversification in the mandible of sabertooths, as compared to the rates calculated for both extinct and extant conical toothed cats. We found that the mandible's shape and physical properties in sabertooth clades evolved at distinctly higher rates than the rest of the felid tree. In addition, sabertooths had similar speciation rate to conical toothed cats, but statistically higher extinction rate. The wealth of morphological specializations required to be a sabertooth, and their tendency to focus on large-sized species as prey, was likely responsible for such high extinction rate, and for the peculiar, disjunctive patterns of sabertooth clade occurrence in the fossil record. •Sabertoothness evolved at least seven times among carnivorous mammals and mammal-like reptiles.•Sabertooths show highly derived cranial morphology and probably had narrow feeding niches.•Specialization is usually linked to high extinction risk in living and fossil species.•We demonstrated sabertooth evolved at different rates and had higher extinction risk than other members of the cat family.