The evolution of the bone-cracking model in carnivorans: cranial functional morphology of the Plio-Pleistocene cursorial hyaenid Chasmaporthetes lunensis (Mammalia: Carnivora)

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The evolution of the bone-cracking model in carnivorans: cranial functional morphology of the Plio-Pleistocene cursorial hyaenid Chasmaporthetes lunensis (Mammalia: Carnivora) Powered By Docstoc
					The evolution of the
				
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Description: Fossil species of the family Hyaenidae represent a wide range of ecomorphological diversity not observed in living representatives of this carnivoran group. Among them, the cursorial meat-and-bone specialists are of particular interest not only because they were the most cursorial of the hyaenids, but also because they were the only members of this family to spread into the New World. Here we conduct a functional morphological analysis of the cranium of the cursorial meat-and-bone specialist Chasmaporthetes lunensis by using finite element modeling to compare it with the living Crocuta crocuta, a well-known bone-cracking carnivoran. As found with previous finite element studies on hyaenid crania, the cranium of C. lunensis is not differentially adapted for stress dissipation between the bone-cracking and meat-shearing teeth. A smaller occlusal surface on the more slender P3 cusp of C. lunensis allowed this species to use less bite force to crack a comparably-sized bone relative to C. crocuta, but higher muscle masses in the latter probably allow it to process larger food items. We use two indices, the stress slope and the bone-cracking index, to show that C. lunensis has a well-adapted cranium for stress dissipation given its size, but the main stresses placed on its cranium might have been more from subduing prey and less from cracking bones. Throughout the Cenozoic, other carnivores besides hyaenids convergently evolved similar morphologies, including domed frontal regions, suggesting an adaptive value for a repetitive mosaic of features. Our analyses add support to the hypothesis that bone-cracking adaptations are a complex model that has evolved convergently several times across different carnivoran families, and these predictable morphologies may evolve along a common gradient of functionality that is likely to be under strong adaptive control. [PUBLICATION ABSTRACT]
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