Ontogenetic variation in the molariform teeth of lizards

The presence of enlarged molariform teeth in some groups of lizards has been known since the early nineteenth century. Few papers, however, have documented ontogenetic variation in the development of such teeth. This paper discusses and evaluates both new and previously described examples of molariform teeth in fossil and Recent squamates of the families Iguanidae, Teiidae, Lacertidae, Scincidae, Xantusiidae, Anguidae, Varanidae, Mosasauridae, and Amphisbaenidae. New data on ontogenetic change in Iguanidae (Chamaeleolis, Diplolaemus), Teiidae (Ameiva), Scincidae (Tiliqua), and Anguidae (Diploglossus) are given. Most species with enlarged teeth as adults have unmodified teeth in hatchling or young individuals, but in a few species (Dracaena guianensis, Teiidae; Tiliqua scincoides, Scincidae; Amphisbaena ridleyi, Amphisbaenidae) the dental modification is already present in early ontogenetic stages. Lack of information on the diet of lizards in general and young animals in particular prevents formulation of well founded hypotheses regarding the adaptive value of molariform teeth. Such dietary information as is available, however, suggests that such lizards may be functioning as generalists, being omnivorous rather than specializing in durophagy.