Protostomia

plural noun
Pro·​to·​sto·​mia

Definition of Protostomia

: animals in which the definitive mouth develops directly from the blastopore (as most worms, bryozoans, brachiopods, mollusks, and arthropods) — compare deuterostomia

History and Etymology for Protostomia

New Latin, from prot- + -stomia

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