Echinoderms (possibly confusing with other groups)

Echinoderms are a group of marine animals characterized by their radial symmetry, a hard spiny skin, and a water vascular system that helps in movement and feeding. Examples include sea stars, sea urchins, and sea cucumbers. They are distinct from other invertebrates like worms or mollusks due to their unique tubular feet operated by hydraulic pressure. Echinoderms are part of the deuterostomes, meaning their embryo develops differently from other invertebrates. Their ability to regenerate limbs and their often elaborate, symmetrical body plans make them fascinating and important members of ocean ecosystems.