What is a deuterostome?

Deuterostome is one of the major groups of the animal kingdom. The majority of deuterostomes are either chordates or echinoderms. Chordates include fish and other vertebrates, while echinoderms include the spiny-skinned starfish, sea urchins and their relatives.

The name deuterostome means "second mouth." The name is derived from the embryo developing the anus first, followed by the mouth. Embryos that develop the mouth first and then the anus are members of the protostome group. Both protostomes and deuterostomes are classified as Bilateria, which are named for their bilateral symmetry, which means that their left and right sides are roughly identical.