In fact, there are even 20 distinct classes that can be found in the fossil record.
All echinoderms display penatamerous radial symmetry.
They are deuterostomes, and are often found as separate sexes. Echinoderms have spiny skin, which is a part of an endoskeleton which supports the organ systems such as muscles. Tube feet are common in this phylum - these are tubes with a suction disk at the distal end. The are used for locomotion and food getting. The water vascular system moves the feet by filling them with water, then emptying them.