[thuh-rap-sid] 
| 1. | 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. |
| 2. | of or pertaining to the Therapsida. |
r wild beast) + apsid- (s. of apsís arch, vault, referring to the temporal arch of the skull) + NL -a neut. pl. ending (see -a 1 )
| the·rap·sid (thə-rāp'sĭd) n. Any of various reptiles of the order Therapsida of the Permian and Triassic periods, many of which are considered to be direct ancestors of mammals. [From New Latin Thērapsida, order name : Greek thēr, wild animal; see theropod + Greek hapsis, hapsid-, arch, vault (from the enlarged lower temporal opening characteristic of the order); see apsis.] the·rap'sid adj. |
| therapsid (thə-rāp'sĭd) Pronunciation Key
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. |
therapsid
any member of a major order (Therapsida) of reptiles of Permian and Triassic time (from 299 million to 200 million years ago). Therapsids were the stock that gave rise to mammals. As early as the preceding Carboniferous Period (from 359 million to 299 million years ago), there appeared a distinct evolutionary line, beginning with the archaic mammal ancestors, order Pelycosauria, and leading toward mammals. From one pelycosaur family sprang the therapsids. Therapsids include mammals and other cynodonts; they form a subgroup of the Synopsida, one of the major branches of amniotes. Therapsids first appear in the Permian Period, during which they flourished and evolved into a number of mammal forms
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