Abstract

We analyze evolutionary tempo and mode of biting performance in living and fossil cats. This topic remains poorly understood to date, and is the subject of considerable speculation. Did cats experience a gradual or a rapid change in biting performance? Were canine and carnassial tooth functions decoupled? What evolutionary models best account for the observed distribution of biting-related traits? And how are such models affected by fossil data? To address these questions, we employ phylogenetic comparative methods applied to a time-calibraed phylogeny of extant and extinct cats. We use a variety of biting performance metrics to quantify the functional roles of the canines and carnassials, as well as the temporal and masseter muscles. Using a model selection approach, we find that Brownian motion with a directional trend is the best evolutionary model for the majority of biting performance metrics. Furthermore, we see a strong decrease in trait values for several metrics near the initial radiation of extant felids. A particularly rapid decrease in trait values characterized the root of the saber-toothed cat clade. The saber-toothed cats show adaptations towards maximizing jaw gape, while retaining functional advantages for performing an efficient carnassial slicing action. In contrast, their carnassial biting performance is only slightly reduced and comparable to that of several extant, small-bodied, conical-toothed cats. The shift from a jaw adduction-driven to a neck flexion-driven canine biting probably occurred earlier in felid history, and during a shorter interval than previously hypothesized. In addition, we find evidence for a weak decoupling between the evolution of canine and carnassial biting performances.