Scaling pattern of the carnivoran hind limb: Main deviations from a conservative pattern.

The scaling pattern of the hind limb in Carnivora was determined using a sample of 13 variables measured on the femur, tibia, and calcaneus, of 429 specimens belonging to 141 species. Standardized major axis regressions on body mass were calculated for all variables, using both traditional regression methods and phylogenetically independent contrasts (PIC). Significant differences were found between the allometric slopes obtained with traditional and PIC regression methods, emphasizing the need to take into account phylogenetic relatedness in scaling studies. Overall, the scaling of the carnivoran hind limb conformed to geometric similarity, although some deviations from its predictions (including differential scaling) were detected, especially in relation with swimming adaptations. The scaling pattern of several phyletic lines and locomotor habits within Carnivora was also determined. Significant deviations from the scaling pattern of the order were found in some phyletic lines, but not in the locomotor habit subsamples. This suggests that the scaling of the carnivoran hind limb is both more heavily influenced by phylogenetic relatedness than by locomotor specializations, and more conservative than that of the forelimb. Finally, together with our previous work on the carnivoran forelimb, the results of the present study suggest that, in large non-aquatic carnivorans, size-related increases in bone stresses are compensated primarily by limb posture changes instead of by modifying limb bone scaling. However, increasing bone robusticity might also occur in the forelimb in response to the heavier stresses acting on the forelimbs due to asymmetrical body weight distribution.