9x6” Inch Silurian Fossil Crinoid (Scyphocrinites) Plate tiny crack - Morocco Crinoids are echinoderms in the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. They live in both shallow water and in depths as great as 9,000 meters (30,000 ft). Adult crinoids are characterized by having the mouth located on the upper surface. The morphology of crinoids is variable and range in size from just a few millimeters to over 1 meter across. They are typically found on hard surfaces, such as rocks or coral reefs, where they filter feed on plankton and small particles from the water column.