Musculoskeletal System and Locomotion

摘要: This chapter focuses on comparing and considering variations in the musculoskeletal anatomy of major marine mammal groups, especially as it relates to locomotion. Propulsion for swimming mammals is derived from paired flipper movements or vertical caudal flukes. Paired propulsion more efficient at low speeds when maneuverability critical. The evolution locomotion each groups also reviewed. Large orbits, a relatively short snout, constricted interorbital region, large orbital vacuities characterize pinniped skull. modern walrus skull easily distinguished that other pinnipeds by being foreshortened having maxillae accommodation upper canine tusks. axial skeleton differently developed among otariids, phocids, walrus. cetacean differs profoundly typical mammalian because telescoped—the result migration external narial opening dorsal position In cetaceans, vertebral column does not contain sacral region pelvic girdle absent. subdermal connective tissue sheath provides an enlarged surface anchor flexor extensor muscles fluke. elbow joint cetaceans uniquely immobile. sirenian its down-turned premaxilla. sharply inclined dugong than manatees. Terrestrial involves walking running, with paws helping weight distribution.