Comparative Cranial Osteology of Fossorial Lizards From the Tribe Gymnophthalmini (Squamata, Gymnophthalmidae) Juliana G. Roscito* and Miguel T. Rodrigues Departamento de Zoologia, Instituto de Biocie ˆncias, Universidade de Sa ˜o Paulo, Sa ˜o Paulo-SP, Brazil ABSTRACT Squamates (lizards, snakes and amphis- baenians) are represented by a large number of species distributed among a wide variety of habitats. Changes in body plan related to a fossorial habit are a frequent trend within the group and many morphological adaptations to this particular lifestyle evolved convergently in non- related species, reflecting adaptations to a similar habitat. The fossorial lifestyle requires an optimal morphological organization for an effective use of the available resour- ces. Skeleton arrangement in fossorial squamates reflects adaptations to the burrowing activity, and different degrees of fossoriality can be inferred through an analysis of skull morphology. Here, we provide a detailed descrip- tion of the skull morphology of three fossorial gymnoph- thalmid species: Calyptommatus nicterus, Scriptosaura catimbau, and Nothobachia ablephara. J. Morphol. 271: 1352–1365, 2010. Ó 2010 Wiley-Liss, Inc. KEY WORDS: body plan; fossoriality; gymnophthalmidae; skull morphology INTRODUCTION Squamates comprise approximately 8,400 spe- cies and represent a diverse group of animals, which exhibit several adaptative phenotypes related to the biogeographic context in which each group evolved. These adaptations range from dif- ferences in habitat use and diet to differences in size and body plans (Vitt et al., 2003). Convergent evolution of morphological traits is an often observed phenomena within the group (Wiens and Slingluff, 2001), the most obvious being the repeated evolution of a snake-like body plan related to fossorial habits, involving body lengthen- ing and limb reduction (Brandley et al., 2008; Gans, 1975; Greer, 1991; Wiens et al., 2006). According to Wiens et al. (2006), a snake-like body plan has evolved independently about 25 times, and even in the same family, (e.g., anguids, gymnophthalmids, and scincids) intermediate or extreme cases of body elongation and limb reduction are found among closely related species or within the same genus (Pellegrino et al., 2001; Shapiro, 2002; Skinner et al., 2008; Wiens and Slingluff, 2001). The transition to fossoriality reflects an adapta- tive complex, which involves morphological modifi- cations in skeletal patterns related to elongation of the body, reduction/loss of limb bones, and skull modifications, such as loss of elements and exces- sive growth and robustness of others, associated with skull consolidation (Greer, 1991; Lee, 1998; Rieppel, 1996; Tarazona et al., 2008). Gymnophthalmidae (Estes et al., 1988) com- prises an assemblage of 42 genera of small lizards distributed throughout Central and South America (Rodrigues et al., 2007), many of which are fosso- rial burrowers with elongated trunks and reduced or lost limbs. These modifications toward the evo- lution of snake-like body plans have originated in- dependently several times during the evolutionary diversification of the family (Pellegrino et al., 2001). Within the Gymnophthalmidae, a monophyletic group of nine genera which is taxonomically known as the tribe Gymnophthalmini (Pellegrino et al., 2001; Rodrigues, 1991, 1995; Rodrigues and dos Santos, 2008), shows a clear and noticeable ev- olutionary trend related to a transition from a lac- ertiform to a serpentiform body plan. The basal genera (Tretioscincus, Micrablepharus, Gymnoph- thalmus, Procellosaurinus, Vanzosaura, and Psi- lophthalmus) are diurnal, lizard-like in shape, and have well-developed limbs and digits and tails lon- ger than body length, while the derived genera (Nothobachia, Scriptosaura, and Calyptommatus) are fossorial, show adaptations to life in sand, and are characterized by a snake-like shape, with extremely elongated body, tails shorter than body, Contract grant sponsors: Fundac ¸a ˜o de Amparo a ` Pesquisa do Estado de Sa ˜o Paulo (FAPESP) and Conselho Nacional de Desenvol- vimento Cientı ´fico e Tecnolo ´gico (CNPq). *Correspondence to: Juliana G. Roscito, Departamento de Zoo- logia, Instituto de Biocie ˆncias-Universidade de Sa ˜o Paulo, Cidade Universita ´ria, Rua do Mata ˜o, Trav. 14, no. 321, Sa ˜o Paulo-SP, Brazil CEP 05508-090. E-mail: juroscito@gmail.com Received 10 March 2010; Revised 21 April 2010; Accepted 5 May 2010 Published online 26 August 2010 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/jmor.10878 JOURNAL OF MORPHOLOGY 271:1352–1365 (2010) Ó 2010 WILEY-LISS, INC.