Going from small to large: mechanical implications of body size diversity in terrestrial mammals

摘要: An animal’s limb posture represents a characteristic feature of its body form, fundamentally influencing the manner in which it moves and the habitats it can exploit. These movements and the underlying biomechanical mechanisms have been studied since the time of Borelli and Marey (Borelli 1685; Marey 1901). Over the course of tetrapod evolution, changes in locomotor limb posture have followed a general trend from sprawling to more erect limb movement patterns (Gray 1968; Gregory 1912; Jenkins 1971a). This trend has been interpreted as reflecting, in part, selection for more economical and faster speeds of terrestrial locomotion. The lateral sprawling gaits of early tetrapods are commonly linked with lateral undulation of the body axis to enhance forward progression (eg, Gray 1968). Although lateral sprawling gaits have been associated with an added cost of body support and constraints on ventilation for aerobic endurance (Carrier 1987), mechanical constraints due to heightened musculoskeletal loading have been less apparent (Blob and Biewener 1999). Nevertheless, faster moving terrestrial vertebrates have generally evolved more erect limb postures, emphasizing parasagittal limb movement and dorso-ventral undulation of the vertebral column, in order to minimize lateral body sway, facilitate ventilation, and enhance forward progression and endurance capability (Gray 1968; Gregory 1912; Carrier 1987).