BIOMECHANICAL SCALING OF LIMB BONES AND DIFFERENTIAL LIMB USE IN CAVIOMORPH RODENTS

Cross-sectional geometric properties associated with the amount of cortical bone in a section (cross-sectional area) and mean bending and torsional rigidity (cross-sectional moments of area) were estimated for selected locations on femoral and humeral diaphyses of caviomorph rodents. Customary limb usages are reflected in the differential values of these properties. Femoral diaphyses of non-burrowing caviomorph rodents have greater capacities to withstand mechanical stresses compared with those of the humeri. This pattern is consistent with hind limb dominated activities, such as locomotor propulsion. Terrestrial quadrupeds that rely on speed and acceleration to escape predators have well-buttressed femoral shafts. Only ctenomyids are characterized by having rigid humeral diaphyses, presumably as an adaptation for burrowing. Cross-sectional geometric properties also can be used to detect more subtle differences in patterns of limb use.