How is the embryological development of a vertebrate animal (frog or bird) similar to that of an echinoderm (starfish or sea cucumber)?

Echinoderms (like starfish and sea cucumber) are deuterostomes, unlike most of the other multicellular animals which are protostomes. Their embryological development is similar to that of vertebrates (like frog and bird) in that they undergo radial cleavage and their anus is formed before the mouth.