Deuterostome

Deuterostomes (taxonomic term: Deuterostomia; from the Greek: "mouth second") are any members of a superphylum of animals. Deuterostomia is a subtaxon of the Bilateria branch of the subkingdom Eumetazoa, within Animalia, and are distinguished from protostomes by their embryonic development; in deuterostomes, the first opening (the blastopore) becomes the anus, while in protostomes, it becomes the mouth. Deuterostomes are also known as enterocoelomates because their coelom develops through enterocoely.

There are four extant phyla of deuterostomes:

Superphylum Deuterostomia was redefined in 1995 based on molecular sequence analyses when the lophophorates were removed from it and combined with other protostome animals to form superphylum Lophotrochozoa. The phylum Chaetognatha (arrow worms) may also belong here. Extinct groups may include the phylum Vetulicolia. Echinodermata, Hemichordata and Xenoturbellida form the clade Ambulacraria. The present phylum Priapulida also has a deuterostomic development, despite being otherwise placed within the protostomes.