Scaling of limb proportions in monitor lizards (Squamata: Varanidae)

The lengths and diameters of the limb segments of 105 monitor lizards from 22 species were measured on preserved museum specimens in order to determine whether limb proportions vary in relation to snout-vent length (used as an indicator of overall body size). Scaling exponents (slopes of allometric equations) were estimated for log-transformed species' mean values, using both conventional nonphylogenetic statistics as well as the method of phylogenetically independent contrasts. Both methods gave essentially the same results. All limb segment lengths and diameters scale with exponents exceeding 1.0; thus, larger species of monitors tend to have larger limbs relative to their snout-vent length. Foot length, however, decreases relative to total hindlimb length in larger species. Measures of limb segment diameters scale with greater exponents than do limb lengths; thus, larger species also tend to have relatively thicker limbs. The empirical results on limb shape are consistent with predictions derived from biomechanical models.