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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 ?
That means one-way airflow may have arisen not among the early archosaurs about 250 million years ago, but as early as 270 million years ago among cold-blooded diapsids, which were the common, cold-blooded ancestors of the archosaurs and Lepidosauromorpha, a group of reptiles that today includes lizards, snakes and lizard-like creatures known as tuataras.
Living reptiles and birds have two holes in the sides of their skulls and are termed diapsids.
Rieppel and deBraga conducted a detailed computer analysis of reptiles which revealed that turtles share more characteristics with diapsids -- modern-day reptiles -- than with anapsids, the more primitive reptile clade to which they long have been assigned.