Spiny Skinned Animals

Overview

Starfish, brittle stars, sea urchins and sea cucumbers are considered spiny skinned animals because of their spiny outer skin. The skin is strengthened by hardened plates, which can be scattered or patterned into a continuous coat. The simple body plan includes an anus at top and mouth at the bottom. For locomotion they fill their body cavity with water then push the water through to tube feet making them rigid and allowing the animal to move in any direction.