noun
- an animal whose mouth develops from the first opening that forms during embryonic development
Usage: biology
Examples
- Insects, worms, and mollusks are all examples of protostomes.
- The protostome lineage includes arthropods and annelids.
- During development, a protostome’s mouth forms before its anus.
- Scientists classify animals as either protostomes or deuterostomes based on embryonic development.
- Most invertebrates belong to the protostome group.
- The protostome clade represents a major branch of the animal kingdom.