noun. Any of a group of amniote vertebrates that are characterized by two openings in the temporal region on each side of the skull. The first diapsids emerged in the Pennsylvanian Period, and their descendants include the lizards, snakes, crocodiles, dinosaurs, pterosaurs, birds, and, in some classifications, the turtles.

Having two temporal arches like the members of the reptilian subclass Diapsida.

noun. Any of very many reptiles, of the subclass Diapsida, that have a pair of openings in the skull behind each eye

noun. reptile having a pair of openings in the skull behind each eye

"Perhaps the confusion here is the similarity to the term “theropod” which always refers to a diapsid except when it refers to Lenny. ben"

reptile  reptilian  

archosaur  archosaurian  archosaurian reptile  crocodilian  crocodilian reptile