Limb Abnormalities in Two Species ofLerista(Scincidae, Squamata)

Abstract

This article presents a survey of phenotypic variation in the limbs of two species of Lerista, a diverse clade of Australian scincid lizards widely considered to provide the best available model for studying squamate limb reduction and loss. Abnormalities were observed in 4.1% of forelimbs and 5.4% of hind limbs in the tetradactyl species L. dorsalis, and 4.5% of forelimbs and 2.4% of hind limbs in the tridactyl species L. timida. Substantial malformation of the manus or pes, involving the complete absence or severe reduction of all digits, accounts for a considerable proportion of anomalies in both species. Almost all remaining anomalies involve the absence or severe reduction of one or two digits. Despite the moderate frequency of limb abnormalities recorded, no cases of supernumerary digits were observed. Patterns of phenotypic variation in both species are consistent with the conventional perspective that substantial limb reduction is effectively irreversible, and provide support for the conclusion that structurally reduced limbs have not been re-elaborated in Lerista.