protostome
/ˈproʊtəˌstoʊm/
noun
- An animal in which the mouth develops from the first opening (the blastopore) in the embryo; includes arthropods, mollusks, annelids, and many other invertebrate groups.
- Protostomes make up one of the two major groups of bilaterally symmetrical animals.
- Insects and snails are examples of protostomes.
- In protostomes, the blastopore becomes the mouth during development.