Functional anatomy of the adaptational strategy of locomotion and feeding systems in Ursidae phylogeny

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In this study, we examined the functional-morphological characters related to the tour-pedaled locomotion and the mastication in the Ursidae species.We ostelogically focused on the three adaptational strategies of arboreal, terrestrial and aquatic swimming species. The limbs were extended in arboreal and swimming species, whereas the terrestrial species possessed the short and robust limbs. These functional characters were consistent with the gross anatomical data of the muscular system. In the herbivorous species as Malayan bear and some other species the pronator-supinator function has been established in the complicated structure of the forearm. Especially the specific manipulation mechanism was controlled by the giant panda that required the locomotion system different from that in the original terrestrial species.The skull was rostro-caudally elongated in the carnivorous species and the cutting mechanism seemed highly-organized. In contrast the zygomatic arch was bilaterally enlarged in skull of the herbivorous species. The bundles of the masseter muscle were thick and the occlusion area of the molar teeth was enlarged to press and destroy crude plant foods in these species. The temporal muscle was well-developed in the carnivorous species, whereas the masseter muscle stronger in the carnivorous species in the data of CT and MRI scanning observations. The findings were also confirmed by the data of the dried-muscle weight.The morphological characters in the locomotion and mastication mechanisms were considered as results from the adaptation in various species within the monophyletic family, Ursidae. The family that contained only a few living species, will interest us as a target of the mammalian evolutionary biology in the future.