Answer the following question given this paragraph: Echinoderms are named for their "spiny skin. " However, the spines aren't on their skin. They are part of the endoskeleton. The endoskeleton consists of calcium carbonate plates and spines, covered by a thin layer of skin. Adult echinoderms have radial symmetry. This is easy to see in the sea star and sand dollar in Figure above . However, echinoderms evolved from an ancestor with bilateral symmetry. Evidence for this is the bilateral symmetry of their larvae. Q: What type of organism, including sea stars and sand dollars, is named for their spiny skin? Choices: - mollusks - diatoms - chordates - echinoderms A:
A:
echinoderms