A group of marine animals including sea stars, sea urchins, and sea cucumbers, characterized by spiny skin and a unique water vascular system. They have radial symmetry and remarkable regenerative abilities.
From Greek 'echinos' meaning 'hedgehog' or 'sea urchin' and 'derma' meaning 'skin', literally 'spiny skin'. The term was coined in the 19th century to describe this distinctive group of marine animals.
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