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

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Other Words from synapsid

synapsid adjective

Examples of synapsid in a Sentence

Recent Examples on the Web

Four-limbed vertebrates were becoming more diverse and among them were primitive amphibians, early reptiles and synapsids, the group that would one day include mammals. Fox News, "World's Largest Extinction Explained by World's Largest Volcanic Eruption," 23 Jan. 2011

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'synapsid.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of synapsid

1956, in the meaning defined above

History and Etymology for synapsid

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

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The first known use of synapsid was in 1956

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something that serves to warn or remind

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