Patterns of Head Shape Variation in Lizards: Morphological Correlates of Foraging Mode

Introduction, The relationship between cranial morphology, diet, and feeding performance has been explored in most vertebrate classes. In fact, key biomechanical elements and regions of the skull are known to be associated with various prey types in a wide range of species (Radinsky, 1981; Kiltie, 1982; Lauder, 1991; Zweers et al., 1994; Perez-Barberia and Gordon, 1999). Numerous examples in teleosts have linked form, function, and diet (Lauder, 1991; Turingan et al., 1995; Wainwright, 1996); in birds, beak morphology and lever mechanics have been correlated with various dietary patterns (Beecher, 1962; James, 1982; Barbosa and Moreno, 1999). In mammals, the rostrum (snout) often becomes narrower and incisor tooth structure changes as dietary selectivity increases (Radinsky, 1981; Solounias, 1988; Gordon and Illius, 1994; Biknevicius, 1996). In lizards (non-ophidian squamates), there are relatively few quantitative and comparative studies relating diet to skull morphology, especially with regard to foraging modes (McBrayer, 2004). Classic works provide descriptions of lizard skull and muscle morphology (see, for example, Haas, 1973; Gomes, 1974). Some functional morphological studies have detailed particularly interesting forms such as the outgroup to lizards, Sphenodon (Gorniak et al., 1982), durophagous species (Wineski and Gans, 1984; Gans et al., 1985; Gans and De Vree, 1986, 1987), carnivorous species (Smith, 1982, 1984; Throckmorton and Saubert, 1982), ovophagous species (Herrel et al., 1997b), and herbivorous species (Throckmorton, 1976, 1978, 1980; Herrel and De Vree, 1999; Herrel et al., 1999a).