Definition of diapsid in US English:



  • A reptile of a large group characterized by the presence of two temporal openings in the skull, including the lizards, snakes, crocodiles, dinosaurs, and pterosaurs.

    Subclass Anapsida

    • ‘The primitive reptiles were represented by lizard-like captorhinids and basal diapsids.’
    • ‘As with many in the systematics community, I am skeptical that turtles are derived diapsids.’
    • ‘It would not be safe to assume that the synapsid temporal fenestra is strictly homologous to the lower temporal fenestra of diapsids.’
    • ‘You may also have noticed that the birds do not have their own box in the cladogram; this is because they are one subgroup of the diapsids, a clade which includes dinosaurs, snakes, and most reptiles.’
    • ‘Adding to the controversy, several independent molecular analyses also regard turtles as diapsids.’


Early 20th century: from modern Latin Diapsida, from di- ‘two’ + Greek apsis, apsid- ‘arch’.