synapsid

noun syn·ap·sid \ sə-ˈnap-səd \

Definition of synapsid

:any of a subclass (Synapsida) of extinct chiefly Permian and Triassic reptiles (such as the pelycosaurs) that resembled mammals, had a single pair of lateral temporal skull openings, and are usually held to be ancestral to mammals

synapsid

adjective

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Origin and Etymology of synapsid

New Latin Synapsida, from Greek syn- + apsid-, apsis arch, vault — more at apsis


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