1. Animals in which the anus develops before the mouth during embryonic development, and the coelom forms from outpouchings of the archenteron; a major division of bilaterally symmetrical animals.
Usage: biology; plural form; singular is deuterostome; technical term used in zoology and evolutionary biology

Examples

• Deuterostomes include echinoderms, hemichordates, and chordates.
• The key characteristic of deuterostomes is that the blastopore becomes the anus.
• Scientists classify vertebrates as deuterostomes based on their embryological development.
• Humans are deuterostomes, sharing this trait with other mammals and birds.
• The evolutionary split between protostomes and deuterostomes occurred over 600 million years ago.