The evolution of locomotor morphology in Rhoptropus (Squamata: Gekkonidae): Functional and phylogenetic considerations

Abstract

BAUER, A. M., A. P. RUSSELL and G. L. POWELL. 1996. The evolution of locomotor morphology in the genus Rhoptropus (Squamata: Gekkonidae). Afr. 1. Herpetol. 45(1): 8–30. Reduced major axis regressions of limb skeletal element length against occiput-vent length (OVL) indicate that there are significant differences in the scaling relationships among the five Namibian species of the genus Rhoptropus. R. afer differs from all other taxa in y-intercept and size of ordinate variable at smallest common OVL for almost all regressions. The proportional differences in limb morphology for this species are most notable for the metapodial elements and proximal phalanges. Distal phalanges do not show this pattern, perhaps reflecting functional constraint imposed by the hyperextensive scansorial system of the toes. Rhoptropus afer also typically has one fewer presacral vertebra than its congeners. There is no evidence that these features of R. afer are shared by its sister taxon, R. bradfieldi. It therefore seems likely that R. afer has evolved these locomotor characteristics, along with many other autapomorphies. since the divergence of the two taxa. The shorter body and longer limbs of R. afer are adaptations for locomotion on horizontal substrates.