FOSSIL SAND DOLLAR

Sand Dollars are members of the order Clypeasteroida, whereas certain species within the order that are not quite as flat in shape are known as sea biscuits. Sand Dollars have also been called "sand cakes" or "cake urchins". They possess a rigid skeleton called a test, which consists of calcium carbonate plates that are arranged in a fivefold symmetric pattern. The term "sand dollar" derives from the currency-like appearance of the tests of dead individuals after being washed ashore. They tend to lack the velvet-like skin of spines and have often been bleached by sunlight. On rarer occasions, the remains become fossilized through the process of mineralization. Sand Dollars first appeared roughly 65 million years ago, during the Paleocene, or the first epoch of the “Age of Mammals” in the Cenozoic Era. They have thrived since then, with 250 living species currently in existence today.

ECHINODERMS

An echinoderm is any animal of the phylum Echinodermata, which includes sea urchins, sand dollars, sea cucumbers, starfish, and brittle stars, as well as the sessile sea lilies, often called "stone lilies". While bilaterally symmetrical as larvae, adult echinoderms are more easily recognized by their five-pointed radial symmetry, or pentamerous symmetry. They are found on the sea bed at every ocean depth, from the intertidal zone, or high tide and low tide zone, to the abyssal zone of darkness, reaching depths of 12,000 feet. The echinoderm phylum contains about 7,600 still living species, making it one of the largest marine-only phyla in the animal kingdom. The first definitive echinoderms appeared near the start of the Cambrian, over 500 million years ago.