These animals could have been designed by a science fiction writer. They can be star shaped, like a ball, with many snake-like arms or a big fat sausage. Some are covered with sharp spines.
They have an internal skeleton protecting the body. The skeleton has a skin on the outside. All the echinoderms have small tube feet that look like flexible tentacles. There is a sucker at the end of the tube feet. The tube feet are worked by a central water pump. Echinoderms have a water pumping system with tubes.
Echinoderms don’t have a head. You can’t see eyes or ears. Most have their mouth under the middle of their body.
Their larvae float around before they settle down on the sea floor. Many kinds of echinoderms live in rockpools. Others live on the bottom of the deepest oceans.