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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.

[New Latin Diapsida, taxon name : di- + Greek hapsis, hapsid-, arch (from the two temporal openings on each side of the skull ); see apsis.]

di·ap′sid adj.


(daɪˈæpsɪd) zoology
any member of the group of reptiles having two holes towards the back of each side of the skull; this group includes crocodiles and snakes
of or relating to diapsids


(daɪˈæp sɪd)

(of reptiles) having two openings in the skull behind each eye.
[< New Latin Diapsida (1903) =di- di-1 + -apsida, neuter pl. of -apsidus, adj. derivative of Greek (h)apsís loop, arch; see apsis]
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.diapsid - reptile having a pair of openings in the skull behind each eye
reptile, reptilian - any cold-blooded vertebrate of the class Reptilia including tortoises, turtles, snakes, lizards, alligators, crocodiles, and extinct forms
Sphenodon punctatum, tuatara - only extant member of the order Rhynchocephalia of large spiny lizard-like diapsid reptiles of coastal islands off New Zealand
saurian - any of various reptiles of the suborder Sauria which includes lizards; in former classifications included also the crocodiles and dinosaurs
archosaur, archosaurian, archosaurian reptile - extinct reptiles including: dinosaurs; plesiosaurs; pterosaurs; ichthyosaurs; thecodonts
crocodilian, crocodilian reptile - extant archosaurian reptile
ophidian, serpent, snake - limbless scaly elongate reptile; some are venomous
anapsid, anapsid reptile - primitive reptile having no opening in the temporal region of the skull; all extinct except turtles
References in periodicals archive ?
Apart from this, the team also found signs that confirmed Eorhynchochelys was a diapsid 6 the reptile group that had two openings on the side of their skulls.
Commingled with the invertebrate trace fossils are abundant vertebrate ichnites, including: Batrachichnus and Characichnos, which were produced by temnospondyl amphibians; Notalacerta, which was produced by diapsid reptiles; and Undichna, which was produced by fish (Getty et al.
All reptiles living today are diapsid, with the exception of turtles, previously thought to be anapsid, making them the only living primitive reptiles.
(1987): Simoedosaurus dakotensis, new species, a diapsid reptile (Archosauromorpha: Choristodera) from the Paleocene of North America.