DEUTEROSTOMIA

(Greek: second mouth), group of animalsincluding those of the phyla Echinodermata (e.g., starfish, sea urchins), Chordata (e.g., vertebrates), Chaetognatha (e.g., arrowworms), and Brachiopoda (e.g., lamp shells)classified together on the basis of embryological development. During that process the mouth of the Deuterostomia develops from an opening into the embryonic gut other than the blastopore, which develops into the anus. The coelom (body cavity) develops from buds off the embryonic gut. A number of Deuterostomia have larval forms. The Deuterostomia constitute one of two divisions of the coelomates (animals having a coelom). Compare Protostomia.