protostome(redirected from Protosome)
Also found in: Medical.
Any of numerous invertebrate animals of the group Protostomia, in which the mouth develops from the first opening in the embryo and the anus develops later, and including the mollusks, annelids, and arthropods.
[From New Latin Prōtostomia, taxon name : proto- + New Latin stoma; see stoma.]
(Zoology) a mollusc, annelid, arthropod or other animal in which the mouth develops before the anus at embryonic stage
any invertebrate in which the mouth appears before the anus during development, cleavage is spiral and determinate, and the coelom forms as a splitting of the mesoderm.