The Sand dollar is related to the starfish, brittle stars, feather stars, sea cucumbers, sea lillies, and sea urchins. About 13,000 are fossils, and there are about 6,000 living species know.
All echinoderms have unique features.
Some features of the sand dollar are that they are mostly round. The sand dollars use the short spines on them to burrow into the ground. Just like any type of animal, the sand dollar, when alive, is covered with skin, and muscle tissue. Also sand dollars have suckers which are fueled by water pressure. The suckers help the sand dollar slide into the sand to get away from predators.