Along with the sea cucumbers, this phylum also contains the Echinoidia, or sea urchins, and the Asteroidea, or starfish.
One class of this phylum can vomit its internal organs at potential predators, which it can then regrow. That class, Holothuroidea, has microscopic ossicles with a sponge-like structure called stereom characteristic of the phylum, and has five rows of tube feet running along its body, thus exhibiting the symmetry characteristic of this phylum. Along with the sea cucumbers, this phylum also contains the Echinoidia, or sea urchins, and the Asteroidea, or starfish. For 10 points, what is this deuterostome phylum characterized by fivefold radial symmetry, the closest relatives of the chordates?
One class of this phylum can vomit its internal organs at potential predators, which it can then regrow.
{Echinodermata} or {echinoderm}s