synapsid

From translingual Synapsida, from syn- + Ancient Greek ἁψίς (hapsís, “arch”).

• (UK) IPA^(key): /sɪˈnapsɪd/

synapsid (comparative more synapsid, superlative most synapsid)

1. Pertaining to the class Synapsida, of animals which have an opening low in the skull roof behind each eye, leaving a bony arch beneath each.
   • 1999, Matt Ridley, Genome, Harper Perennial, published 2000, page 26:

     We are synapsid tetrapods, a group of reptiles that almost went extinct 200 million years ago in competition with the better-designed dinosaurs.

synapsid (plural synapsids)

1. Any animal (including all mammals) of the class Synapsida.

• mammal-like reptile (dated)
• stem mammal