Differentiation between fore- and hindlimb bones and locomotor behaviour in primates

Primate appendicular limb bones were measured on the cross-sectional geometry at the mid-length of the humerus and femur and on the external dimensions of long bones of the same individuals. Cross sections were directly measured by means of computer tomography or direct sectioning. The morphometry of bones and locomotor behaviour is discussed from the viewpoint of the functional differentiation between the fore- and hindlimbs. The primate group which daily adopted a relatively terrestrial locomotor type demonstrates robust forelimb bones compared with the group which adopted a fully arboreal locomotor type. In contrast, the arboreal group showed relatively large and long hindlimb bones. The difference resembled the previously reported comparison between terrestrial and arboreal groups among wholly quadrupedal mammals. Humans were more similar to the arboreal group than to the terrestrial group. Parameters of the cross-sectional geometry showed a slightly positive allometry in total primate species. Slopes of the parameters were explained by the influence of muscle force.