Appendicular skeleton of the vestigial-limbed African skink Eumecia anchietae

Abstract

Abstract Within the lizard family Scincidae (the skinks) are numerous examples of species with vestigial limbs and girdles, but these vestigial structures remain undescribed for many such species. Here we seek to partially fill this gap in knowledge by describing the vestigial limb and girdle skeletons of Eumecia anchietae, an African skink for which the appendicular skeleton has not previously been described. Radiographs of 10 adult specimens reveal variation in the degree of ossification of the interclavicle and scapula and in the forelimb epiphyses; lengths of the humerus, forelimb and femur; and number of metacarpals, metatarsals and phalanges. The variation is unrelated to specimen size for most of these parameters. In all specimens the sternum is absent, the clavicle is ossified, ossification is greater in the humerus than in the more distal forelimb elements, ossification is greater in the tibia than the fibula, and the third toe has two phalanges. The results of this study suggest caution in the use of details of the morphology of vestigial limbs to diagnose lizard species, because of the variability present in such limbs.