Biomechanical adaptations to predation in the carnivoran craniofacial skeleton.

摘要

Carnivorans (Carnivora, Mammalia) exhibit a wide range of skull shapes. In this dissertation, I quantified patterns of skull shape variation in dogs (Canidae), cats (Felidae) and extinct, cat-like carnivorans (Nimravidae) using traditional and geometric morphometric methods. I then used Finite Element Analysis (FEA) to investigate the biomechanical consequences of skull shape variation in canids and felids.;Canids are social pursuit predators, relying on their skulls and teeth to apprehend prey. Felids are solitary ambush predators that use suffocating bites to kill restrained prey. Patterns of skull shape variation in canids and felids are associated with these differences in predatory behavior. In canids, skull shape variation is associated with the size of prey taken. Canids that specialize on small, fast moving prey have long, narrow jaws for increased bite speed. Conversely, canids that specialize on large, thick-skinned prey have short, broad jaws for increasing bite force. The jaws of generalist canids fall intermediate to the two specialized types. Felids exhibit a different pattern of shape variation; small felids take small prey but have short jaws while large felids take large prey and have longer jaws. Prey size in felids is limited by what can be fit between the canine teeth. Longer jaws result in relatively larger gape distances, allowing large felids to access relatively larger prey than small felids.;FEA simulations of biting behavior show that the skulls of canids that take small or medium prey are similar in strength. Canids that take large prey have stronger skulls and are better able to resist additional forces, such as those incurred by large, struggling prey. FEA also reveals that large felids produce relatively smaller bite forces than small felids and that their skulls undergo more strain when biting. However, large felid skulls exhibit lower stress values, and are therefore stronger, during biting and prey-driven loads. While cranial strength in canids is increased by changes in skull shape, large felids achieve increased cranial strength by thickening the bones of their skulls. Independent evolution of large prey specialization in canids and felids results in similar biomechanical demands, which are met in different ways.