A Comparative Analysis of the Post-Cranial Skeleton of Fossorial and Non-Fossorial Gymnophthalmid Lizards Juliana G. Roscito* and Miguel T. Rodrigues Departamento de Zoologia, Instituto de Biocie ˆncias, Universidade de Sa ˜o Paulo, Sa ˜ o Paulo, Brasil ABSTRACT Squamates are found in a wide range of habitats and show a corresponding diversity of morphol- ogies that can often be correlated with locomotor mode. The evolution of a snake-like body form, frequently asso- ciated with fossoriality, from a typical lacertiform mor- phology involves changes in the morphology of verte- brae, girdles, and limbs; the changes are mainly mani- fested by the reduction or loss of limbs and body elongation. In this study, we describe the axial and appendicular skeletons of six closely related gymnoph- thalmid species. Three of them show a lizard-like mor- phology, with a four-digit forelimb and a five-digit hind- limb, and the other three show a snake-like morphology associated with a burrowing habit, with reduced limbs and a longer body in comparison to the former three spe- cies. We show that vertebral morphology is similar among the six species, with the differences being accounted for by an increase in the number of vertebrae and by the structural reduction of girdles and limbs in the snake-like species. Skeletal morphology provides val- uable information on locomotion type, physiology, diet, and other biological features. The burrowing morphology usually involves accentuated reduction of girdle and limb elements, reflecting an undulating type of locomo- tion in which the limbs play little or no role in propel- ling the body; in contrast, well-developed limbs and gir- dles indicate a greater reliance on the limbs for body propulsion. Limb reduction is frequent among verte- brates, but many different phenotypes are found in spe- cies exhibiting some kind of reduction, indicating that different mechanisms and evolutionary pressures may be involved in generating the diverse morphologies. J. Morphol. 000:000–000, 2012. Ó 2012 Wiley Periodicals, Inc. KEY WORDS: Gymnophthalmidae; limb morphology; limb reduction; fossoriality INTRODUCTION The morphology of the axial and appendicular skeletons is quite variable among reptilian saurop- sids, and variation in form can often be correlated with lifestyle (Losos, 1992; Gans and Fusari, 1994; Losos et al., 1994, 1998; Benesch and Withers, 2002). Of especial interest is locomotor mode, which is the result of coordinated actions of both the axial and appendicular systems (Renous et al., 1998), and is ultimately related to the morphology of such sys- tems. The association between morphology and loco- motion is easily perceived when comparing lizard- like and snake-like species: the former morphotype, usually associated with a ground-dwelling habitat, is characterized by the presence of well-developed limbs that act as the main propelling elements for the body. However, in the snake-like morphotype, usually seen in burrowing species and characterized by reduced limbs often in association with an elon- gated body, locomotion is primarily the result of undulating movements generated by the axial skele- ton (Wiens et al., 2006; Shine and Wall, 2008). Fossoriality and the associated morphological changes for burrowing have evolved independently several times within squamates (lizards, ‘‘snakes’’ and ‘‘amphisbaenians’’; Wiens et al., 2006; Brand- ley et al., 2008), and different degrees of body elon- gation and limb/girdle reduction can be observed both in distantly-related groups as well as within the same genus (Lee, 1998; Wiens and Slingluff, 2001; Shapiro, 2002; Skinner et al., 2008). The South American Gymnophthalmidae (Estes et al., 1988) is an example of a clade where a snake-like morphology, i.e., an elongated body and reduced or absent limbs have evolved independ- ently in a few lineages (Pellegrino et al., 2001; Castoe et al., 2004). One such lineage is the Gym- nophthalmini, a monophyletic group comprised of nine genera, Tretioscincus, Micrablepharus, Gym- nophthalmus, Procellosaurinus, Vanzosaura, Psi- lophthalmus, Nothobachia, Scriptosaura, and Calyptommatus (Pellegrino et al., 2001; Castoe et al., 2004; Rodrigues and dos Santos, 2008). The Additional Supporting Information may be found in the online version of this article. Contract grant sponsor: Fundac ¸a ˜o de Amparo a ` Pesquisa do Estado de Sa ˜o Paulo (FAPESP); Contract grant sponsor: Conselho Nacional de Desenvolvimento Tecnolo ´gico (CNPq). JGR analyzed the data, conceptualized and drafted the manuscript; MTR participated in the coordination of the study and revised it critically giving important intellectual contributions. *Correspondence to: Juliana G. Roscito; Departamento de Zoo- logia, Instituto de Biocie ˆncias, Universidade de Sa ˜o Paulo, Rua do Mata ˜o, Sa ˜o Paulo, SP, Brasil. E-mail: juroscito@gmail.com Received 20 October 2012; Revised 17 December 2012; Accepted 18 January 2013 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/jmor.20139 JOURNAL OF MORPHOLOGY 000:000–000 (2013) Ó 2013 WILEY PERIODICALS, INC.