Diapsida (subclass)

Members of a taxon of reptiles who developed two pairs of temporal arches (holes behind the eye in their skull) around 300 million years ago during the late Carboniferous period. Among diapsids are dinosaurs, crocodians, lizards, snakes, turtles, and birds. Some living diapsids have lost either one hole (lizards), or both holes (snakes), or even have a heavily restructured skull (modern birds), but they are classified as diapsids based on their ancestry. There are at least 14,600 living species of diapsids.