Echinodermata
An echinoderm is classified as a member of the phylum Echinodermata, which encompasses a diverse group of adult organisms featuring radial symmetry. This phylum includes various well-known creatures such as starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies, also referred to as "stone lilies". Adult echinoderms can be found inhabiting the sea floor across all depths of the ocean, ranging from the intertidal zone to the abyssal zone. With approximately 7,000 living species, the phylum Echinodermata ranks as the second-largest category of deuterostomes, following the chordates. Notably, echinoderms comprise the largest group of exclusively marine organisms. The earliest definitive echinoderms emerged during the Cambrian era.
