PHYLOGENETIC AND GEOMETRIC MORPHOMETRIC ANALYSES OF LYGOSOMINE SKINK MANDIBLES

Skinks represent an abundant group of lizards with a global distribution. Efforts to classify skinks have manifested through phylogenetic analyses incorporating mostly molecular data. Disadvantages with this approach are relevant mostly to paleoherpetologists, working with fossil material and morphological traits. As a result in this shift towards molecular data use, much fewer studies have utilized morphological character matrices for extant taxa. Incomplete fossil squamate material is typically represented by fragmentary cranial or mandibular elements, severely constraining the amount of information for character scoring, and thus classification is based on much fewer characters. Phylogenetic and geometric morphometric methods may be employed for classification of incomplete material. In this study, methods using parsimony on a character matrix of twenty binary morphological characters on seventeen lygosomine scincid taxa, and a geometric morphometric analysis using Principal Component Analysis, Thin-Plate Spline Deformation, and MANOVA were used to determine the method better capable of discriminating amongst the three species groups of Australian lygosomines: Egernia, Eugongylus, and Sphenomorphus. While a phylogenetic analysis via parsimony failed to recover relationships between scincid taxa, a MANOVA based on geometric morphometric techniques detected significant differences between all three scincid groups. Few studies have incorporated geometric morphometrics on osteological specimens of skinks to aid in classification of skink material, in which this study here should aid in future investigations relevant to fossil skink material.