Short Communication New insights into the early history of snakes inferred from two nuclear genes Nicolas Vidal a, * and Patrick David b a Service de Syst ematique Mol eculaire, Institut de Syst ematique (CNRS FR 1541), Mus eum National dÕHistoire Naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, France b UMS 602 Taxinomie-collection, Reptiles et Amphibiens, D epartement Syst ematique et Evolution, Mus eum National dÕHistoire Naturelle, 25 rue Cuvier, 75231 Paris Cedex 05, France Received 30 June 2003; revised 18 December 2003 1. Introduction Snakes are among the most successful groups of reptiles, numbering about 3000 extant species (Uetz, 2003). They are divided into two main groups. The fossorial scolecophidians (‘‘blindsnakes’’) are small snakes with a limited gape size which feed on small prey (mainly ants and termites) on a frequent basis. The alethinophidians (‘‘typical snakes’’) are more ecologi- cally diverse and most species feed on relatively large prey, primarily vertebrates, on an infrequent basis (Cundall and Greene, 2000; Vidal and Hedges, 2002a). According to morphological studies, the most distinctive evolutionary trend within living snakes is the increase of the gape size from fossorial scolecophidians (Typhlopi- dae, Leptotyphlopidae, and Anomalepididae) and fos- sorial alethinophidians (‘‘Anilioidea’’ i.e. Aniliidae, Cylindrophiidae, Uropeltidae, and Anomochilidae) to ecologically diverse macrostomatan alethinophidian snakes such as boas, pythons, and caenophidians (vi- pers, cobras, and ‘‘colubrids’’) (Cundall and Greene, 2000, but see Lee and Scanlon, 2002). The name mac- rostomate is given to a complex structural plan that allows the buccal opening to enlarge. This enlargement is due mainly to a posterior elongation of the supra- temporal bone that shifts the quadrate posteriorly, and to the dorsoventral elongation of the quadrate. A mac- rostomate structure permits the ingestion of very large prey, sometimes greater in diameter than the predatory snake itself (Rage and Escuilli e, 2003). The monophyly of the macrostomatan condition is supported by the following seven unambiguous synapomorphies. (1) Marginal teeth elongate, needle-shaped, and distinctly recurved. (2) Ascending process of maxilla absent. (3) Maxilla projects distinctly beyond posterior margin of orbit with a broad, flat surface. (4) Basicranium keeled. (5) Presence of a free ending posterior process of the supratemporal. (6) Crista interfenestralis forms an in- dividualized component of the ventral rim of the crista circumfenestralis. (7) Elongate posterior dentigerous process of the dentary present (Rieppel et al., 2002). Several molecular phylogenies of snakes have ap- peared recently (Slowinski and Lawson, 2002; Vidal and Hedges, 2002a,b, in press; Wilcox et al., 2002). All agree on the monophyly of three of the four clades supported by morphological studies: the Scolecophidia, the Alethinophidia, and the Caenophidia. On the other hand, none of these studies found either the fossorial ‘‘Anilioidea’’ or the Macrostomata (Alethinophidia mi- nus ‘‘Anilioidea’’) to be monophyletic. In this work, we address the phylogenetic relationships of basal snakes in order to investigate the evolutionary history of the macrostomatan condition, using sequences from two nuclear protein coding genes, oocyte maturation factor (C-mos), and recombination-activating gene 1 (RAG1). 2. Materials and methods All sequences used for this study are listed in Table 1. Sequence entry and alignment (43 taxa) were performed manually with the MUST2000 software (Philippe, 1993). For the C-mos gene, amino acid properties were used while there were no indels for the RAG1 gene, resulting in 537 C-mos sites (297 variable sites, 195 of * Corresponding author. Fax: +31-1-40-79-38-44. E-mail address: nvidal@mnhn.fr (N. Vidal). 1055-7903/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2004.01.001 Molecular Phylogenetics and Evolution 31 (2004) 783–787 MOLECULAR PHYLOGENETICS AND EVOLUTION www.elsevier.com/locate/ympev