Sea stars, sea urchins, sand dollars and sea cucumbers are all members of the phylum Echinodermata. Echinoderm means “spiny skin” in Greek. Echinoderms are found in ocean ecosystems worldwide ...

They belong to the Echinoidea, one of the five classes of the phylum Echinodermata, the others being holothurians, crinoids, starfish and brittlestars. Like all echinoderms, echinoids have a skeleton ...