- They are exclusively marine animals.
- They are triploblastic and have a coelomic cavity.
- These are spiny skinned organisms.
- They exhibit organ system level of organization. Most members have a circulatory system as well as a digestive system.
- They also have a peculiar water-driven tube system that they use for moving around.
- They have hard calcium carbonate structures that they use as a skeleton.
For Example: sea stars, sea urchins.