Are Sand Dollars Alive?

Sand dollars are indeed alive. They are fascinating marine invertebrates that make up the order Clypeastroida (a group of echinoderms in class Echinoidea). Sand dollars are closely related to sea urchins and heart urchins, with which they share a similar flat, disk-shaped body structure and radial symmetry. They are found in shallow coastal waters around the world where they inhabit sandy seafloor environments and feed on tiny crustaceans, diatoms, and algae. Their bodies commonly wash up on beaches.

Sand dollars have a number of unique adaptations. Their bodies are covered with spines and hairs (which are called cilia) that help them burrow and crawl through the sand. These structures also funnel food into the mouth (which is located in the center of the animal’s underside). The spines are oriented towards the anus (which is located at its posterior). The upper surface of a sand dollar displays pentaradiate symmetry, a body pattern that can be described as “five petals” spreading out from the center of its body.

The group is made up of more than 250 species. One of the most well-known is the common sand dollar (Echinarachnius parma), which is found along the coast of eastern North America, Alaska, Japan, and far eastern Russia, and a handful of islands in the Southern Hemisphere.