Uniqueness of primate forelimb posture during quadrupedal locomotion

TLDR

Primate quadrupedal locomotion is distinguished by a more protracted limb posture and larger limb angular excursion, yet kinematic data are limited to few species, especially for forelimbs. This study quantified arm and forelimb posture during walking in 102 mammalian species, including 53 nonhuman primates and 49 nonprimate mammals. Primates consistently exhibit a more protracted arm at hand touchdown and greater total humeral angular excursion than other mammals, indicating functional adaptations for arboreal locomotion with grasping extremities. Am J Phys Anthropol 112:87–101, 2000; © 2000 Wiley‑Liss, Inc.

Abstract

Among the characteristics that are thought to set primate quadrupedal locomotion apart from that of nonprimate mammals are a more protracted limb posture and larger limb angular excursion. However, kinematic aspects of primate or nonprimate quadrupedal locomotion have been documented in only a handful of species, and more widely for the hind than the forelimb. This study presents data on arm (humerus) and forelimb posture during walking for 102 species of mammals, including 53 nonhuman primates and 49 nonprimate mammals. The results demonstrate that primates uniformly display a more protracted arm and forelimb at hand touchdown of a step than nearly all other mammals. Although primates tend to end a step with a less retracted humerus, their total humeral or forelimb angular excursion exceeds that of other mammals. It is suggested that these features are components of functional adaptations to locomotion in an arboreal habitat, using clawless, grasping extremities. Am J Phys Anthropol 112:87–101, 2000. © 2000 Wiley-Liss, Inc.