Morphological variation in the abdominal skeleton of Tropiduridae was examined from radiographs and cleared-and-stained specimens of 61 species. Based on the numbers of xiphisternal and postxiphisternal inscriptional ribs, as well as the presence of inscriptional ribs articulating ventromedially, seven patterns of rib attachment are described. The distribution of these patterns among the species studied reveals intra- and interspecific variation, which indicates that the abdominal skeleton of lizards is a good source of fixed and polymorphic characters for phylogenetic analyses.