Therapsida

plural noun

The·​rap·​si·​da

-sədə

: an order of synapsid reptiles that flourished during the Permian and Triassic periods with the last forms becoming extinct during the Cretaceous

Note: Reptiles of the order Therapsida are considered ancestors of the mammals.

Word History

Etymology

New Latin, from Greek theraps attendant + New Latin -ida

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!