CRANIAL MORPHOLOGY IN SABERTOOTH CATS: ALLOMETRY, FUNCTION AND PHYLOGENY.

CRANIAL MORPHOLOGY IN SABERTOOTH CATS: ALLOMETRY, FUNCTION AND PHYLOGENY. Cranial morphology of felids and other sabre-toothed mammals has been studied using different approaches and methodologies. Recent studies used geometric morphometry analyses of the lateral view of the mandible and skull, and showed that derived sabretooth cats differ from recent felids by having a set of characters (e.g., small coronoid process, large chin and mastoid processes) associated with the presence of hypertrophied upper canines. In this study, we used geometric morphometrics to analyze the shape of the skull (dorsal and ventral views) and mandible (lateral view) in a large sample of extant felids (Felinae), extinct sabretooth fads (machairodontines), nimravids, creodonts, and the marsupial sabretooth Thylacosmilus Riggs. Results were congruent with those obtained using a lateral view of the skull: primitive sabretooth fell next to recent Felinae, but derived ones fell outside the range of Felinae, because they possessed larger mastoid process, larger and more procumbent upper incisors, and smaller temporal fossa, among other characters. However, sabretooth shared some features (e.g., large palate and canines) with larger Felinae (e.g., Panthera spp.), suggesting that they were able to hunt large mammals. The pattern of cranial variability of these groups is explained by ecological factors but also by phylogenetic constraints. The shape of the skull was correlated with the size and the length of the upper canines, two features that presented a clear correlation along the phylogeny of the group.