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 are named for their “spiny skin”?

 Choices:

- arachnids

- reptiles

- amphibians

- echinoderms

A:
echinoderms
