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[thuh-rap-sid] /θəˈræp sɪd/
any of various groups of mammallike reptiles of the extinct order Therapsida, inhabiting all continents from mid-Permian to late Triassic times, some of which were probably warm-blooded and directly ancestral to mammals.
of or relating to the Therapsida.
Origin of therapsid
< New Latin Therapsida (1905), equivalent to Greek thēr- (stem of thḗr wild beast) + apsid- (stem of apsís arch, vault, referring to the temporal arch of the skull) + New Latin -a neuter plural ending (see -a1) Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for therapsid


any extinct reptile of the order Therapsida, of Permian to Triassic times: considered to be the ancestors of mammals
Word Origin
C20: from New Latin Therapsida, from Greek thēr beast + Latin apsis arch
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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therapsid in Science
An advanced type of synapsid reptile that evolved in the Permian Period. Therapsids further differentiated their dentition into nipping, biting, and crushing teeth, and (unlike diapsids) had forelimbs that were more greatly developed than hindlimbs. Therapsids include the so-called mammallike reptiles of the Permian and Triassic Periods, as well as mammals. Compare anapsid, diapsid, synapsid.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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