Testing for the Effects of Locomotion on Intraspecific Variability in the Prosimian Skeleton

This study investigates intraspecific variability in the cranium and appendicular skeleton of eight prosimian species (Eulemur fulvus, Hapalemur griseus, Lemur catta, Varecia variegata, Galago senegalensis, Otolemur crassicaudatus, Nycticebus coucang, and Tarsius syrichta) to test the hypothesis that regions of the skeleton more subject to variable stresses in locomotion may be more morphologically variable. The impacts of muscular action on bone may be more apparent in the limbs than on the cranium, as the cranium is less directly involved in locomotion. Bone modelling may also be more important in determining the shape of the diaphyses of long bones than of the epiphyses. Developmental constraint is likely to minimize cranial and epiphyseal variability due to the requirements for precise matching at limb joints and cranial sutures. Due to the importance of hindlimb dominated vertical clinging and leaping in prosimians (in which G. senegalensis, H. griseus, and T. syrichta are often classified as specialists, and all but N. coucang practice occasionally), hindlimbs were hypothesized to be more variable than forelimbs in this sample, the reverse of the observed catarrhine pattern. It was found that postcrania were more variable than crania (Z = ­2.34, p < .05) and diaphyses more variable than epiphyses (Z = ­2.26, p < .05). This may indicate that common developmental processes characterize variation in these regions across primates. Forelimb and hindlimb variability were not significantly different, however. This may indicate that prosimian limb use is relatively undifferentiated.