The cranial osteology and dentition in the scincid lizards of the genus Chalcides (Reptilia, Scincidae)

Abstract

The skull and dentition were analysed and compared in a number of species of Old World scincid lizards, genus Chalcides (including Sphenops). The major differences are related to the decrease in absolute skull size, which entails an increase in the relative size of the otic capsule and the progressive obliteration of the supra‐ and post‐temporal fossae. The greatest reduction of the post‐temporal fossa is observed in the smallest species, resulting in close proximity of parietal and supraoccipital bones and in a possible reduction of metakinesis. Another major difference concerns the relationships between pre‐ and post‐frontal bones, widely separated in Chalcides sensu stricto and articulated in the taxa formerly attributed to the genus Sphenops. This close connection likely represents an internal reinforcement preventing deflection or fracture in these sand‐swimming taxa by reducing the mobility of the fronto‐parietal mesokinetic joint. The teeth are conical, pleurodont and ankylosed to the inner margin of the dentary, pre‐maxilla and maxilla. They exhibit two cusps separated by a single groove that probably aid in grasping hard‐bodied prey. The pre‐maxillae usually bear an odd number of teeth; the number of pre‐maxillary, maxillary and dentary teeth does not seem to increase with skull size. In all cases, the number of dentary teeth exceeds that of maxillary ones.