pro·​to·​stome ˈprō-tə-ˌstōm How to pronounce protostome (audio)
: any of a major group (Protostomia) of bilateral metazoan animals (such as mollusks, annelids, and arthropods) characterized in typical forms by determinate and spiral cleavage, formation of a mouth and anus directly from the blastopore, and formation of the coelom by splitting of the embryonic mesoderm compare deuterostome

Word History


New Latin Protostomia, from prot- + Greek stoma mouth — more at stomach entry 1

First Known Use

1959, in the meaning defined above

Time Traveler
The first known use of protostome was in 1959

Dictionary Entries Near protostome

Cite this Entry

“Protostome.” Dictionary, Merriam-Webster, Accessed 2 Oct. 2023.

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