Deuterostomes are animals that form their mouths second during embryonic development. This is in contrast to protostomes, which form their mouths first. Deuterostomes include the echinoderms, hemichordates, and chordates.

Here are some of the key characteristics of deuterostomes:

- Mouth forms second during embryonic development: The mouth of a deuterostome forms from the blastopore, which is the opening of the archenteron (the primitive gut). In contrast, the mouth of a protostome forms from the stomodeum, which is an invagination of the ectoderm.

- Coelom forms through enterocoely: The coelom, which is the body cavity of an animal, forms through enterocoely in deuterostomes. This means that the coelom is derived from the archenteron. In contrast, the coelom forms through schizocoely in protostomes, which means that it is derived from a split in the mesoderm.

- Radial or bilateral symmetry: Deuterostomes can have either radial or bilateral symmetry. Radial symmetry means that the animal has a body plan that is based on a central axis, with similar parts arranged around the axis. Bilateral symmetry means that the animal has a body plan that is based on a left-right axis, with two similar halves.

Examples of deuterostomes include:

- Echinoderms: sea stars, sea urchins, sand dollars

- Hemichordates: acorn worms, pterobranchs

- Chordates: fish, amphibians, reptiles, birds, mammals

Deuterostomes are one of the two main groups of animals, along with protostomes. They are a diverse group of animals with a wide range of body plans and lifestyles.