Vestigial structures in the appendicular skeletons of eight African skink species (Squamata, Scincidae)

Abstract

AbstractLimb reduction and loss, with reduction of limb and girdle skeletons to a vestigial state, has occurred several times independently within the skink family (Scincidae). The vestigial appendicular skeletons of most limbless skinks have not been described before now. Here we describe those of eight African skink species, all with a burrowing lifestyle: Acontias percivali, Acontias meleagris, Typhlosaurus cregoi, Typhlosaurus lineatus, Typhlacontias gracilis, Sepsina bayonii, Scelotes anguina and Scelotes arenicola. For all but two (A. meleagris and Sc. arenicola) the appendicular skeletons were previously undescribed. Limbs are absent in all specimens except for vestigial hindlimbs in Se. bayonii and vestigial femurs in one specimen of Sc. arenicola. In our sample, the pectoral girdle is reduced to a pair of tiny slivers in A. percivali, Ty. gracilis, Se. bayonii and Sc. anguina. It is absent in the other specimens. The pelvic girdle is absent in Ty. cregoi. In all the rest but Se. bayonii it is vestigial, retaining only the ilium in A. meleagris, Ty. lineatus and one specimen of Sc. arenicola. This study adds to the number of skink species with vestigial appendicular skeletons that have been described. It also adds to the range of documented intraspecific variation in the vestigial appendicular skeletons of A. meleagris, Sc. arenicola and the Australian skinks Lerista stylis and Lerista carpentariae. We observed asymmetry between the left and right sides in the vestigial appendicular skeletons of four of the African skink species: A. meleagris, Sc. anguina, Sc. arenicola and Se. bayonii.