Of the lizards, 3 of the 6 species of Varanidae, 16 of the 30 Scincidae, 8 Geckonidae, and 8 out of the 11 Agamidae are peculiar.
Zonuridae and Anguidae assume a central position, with Agamidae and Iguanidae as two parallel families (not very different from each other) of highest development, one in the Old World, the other in America.
In their general structure the Iguanidae closely resemble the Agamidae, from which they differ mainly by the pleurodont dentition.