plural noun

: a subclass of Reptilia comprising extinct reptiles of the Pennsylvanian, Permian, and Triassic, having a single pair of lateral temporal openings in the skull, and usually held to be ancestral to the true mammals compare ictidosauria , therapsida

Word History


New Latin, from synapsis + -ida

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Dictionary Entries Near Synapsida

Cite this Entry

“Synapsida.” Dictionary, Merriam-Webster, Accessed 21 Jun. 2024.

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