[ dahy-ap-sid ]
/ daɪˈæp sɪd /


(of reptiles) having two openings in the skull behind each eye, characteristic of the subclasses Lepidosauria and Archosauria, including all living reptiles except turtles.


a diapsid reptile.
Compare anapsid.

Origin of diapsid

< New Latin Diapsida (1903); see di-1, anapsid
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for diapsid

  • Their remains fall into two great groups, which are known as the Diapsid and the Synapsid reptiles.

Science definitions for diapsid


[ dī-ăpsĭd ]

Any of various amniotes having a skull with two pairs of temporal openings. Diapsids evolved in the Permian Period and grew longer and better-developed hindlimbs than forelimbs (unlike therapsids). Diapsids evolved into the archosaurs (including the dinosaurs and their descendants the birds) and all modern reptiles except, in some classifications, the turtles. Compare anapsid synapsid therapsid.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.