Geometric morphometric analysis reveals cranial shape divergence and asymmetry in extinct and extant species of big cats (Carnivora: Felidae)

Abstract

Felidae, a family of the order Carnivora, includes extinct and extant species of cats spread across a wide ecological and geographical landscape. Cats are well-suited for predation due to various physical and behavioral characteristics, such as optimized limb length, skull shape, as well as enhanced hearing and vision. Morphological changes across Felidae species, particularly changes in skull shape, are likely explained by differences in predatory and feeding behaviors. Toward that end, cranial shape was analyzed across six different extant and extinct Felidae species using two-dimensional geometric morphometrics. From the lateral cranial view, we discovered that the cheetah (Acinonyx jubatus) and the North American Sabretooth (Smilodon) had the most significant shape divergence, specifically at the frontal bone and post orbital regions of the skull. Specifically, we found that the Sabretooth had a significantly shorter coronoid process compared to other Felids. We also observed a significant difference in post orbital shape in the cheetah dorsal cranium. Interestingly, we found that both the cheetah and the extinct North American Lion demonstrate significant shape asymmetry in the postorbital region from a ventral view of the skull. Shape divergence and asymmetry in select Felid skulls may arise from decreased genetic diversity. Taken together, we reasoned that morphological changes in skull shape likely evolved to support differences in predatory behavior across Felidae.