A group of marine organisms with a calcium carbonate (CaCO3) skeleton of stereom, and a water vascular system used for respiration, locomotion and consumption and removal of food and waste. All living groups of echinoderms display unique five-fold symmetry, but many fossil taxa do not. The name echinoderm comes from the ancient Greek echinos, or hedgehog, and derma, which means skin. This is because many echinoderms have spines. Echinoderms first appear in the fossil record in the Cambrian period around 520 million years ago.