Cranial musculature of South American Gekkonidae

The cranial myology of 13 South American geckos was compared and analyzed for taxonomic significance. The general pattern emerges that muscles in this group do not vary substantially from those of other lizards, except that the geckonids have fewer muscle layers. The former condition is particularly important with respect to the adductor musculature of the jaw, given its fundamental role in the chewing process. A great variety of lizards, both those with the geckonid bauplan and those with other morphologies exhibit similar basic structures in the jaw adductor muscles, despite significant differences in diet. There appears to be no direct correlation between diet and the morphology of head musculature of lizards. It is hypothesized that differences between and within bauplans can be ascribed to phylogenetic factors rather than to functional characteristics such as diet and life-styles. Twenty characteristics reflecting minor variations in the Gekkotan bauplan were selected for comparison in performing a cladistic analysis rooted on the sphaerodactylinid geckoes Coleodactylus amazonicus and C. septentrionalis. Groupings of muscular characteristics resulting from this analysis lead to different interpretations of taxonomic relationships from those derived from previous studies on the taxa examined.