Anthozoans solitary or colonial polyps that lack a medusa stage. Include the largest number of cnidarians species. The anthozoan polyp is more complex than hydrozoan or scyphozoan polyps. The gut, for instance, contains several thin partitions, or septa, that provide additional surface area for the tigestion of large prey . Sea anemones are common and colorful anthozoans that often have large polyps. Colonial anthozoans occur in an almost infinite variety of shapes.The mostly colonial stony corals have calcium carbonate skeletons that may from coral reefs. Though stony corals can be foun in cold waters, it is in the tropics that they are active in reefbuilding .Gorgonians, such as sea fans , are colonial anthozoans that secrete a tough branching skeleton made of protein.Precious corals are gorgonians with fused re or pink calcareous spicules in addition to the protein skeleton .Black corals, which are neither gorgonians nor stony corals , secrete a hard , black, protein skeleton. Both precious and black corals are carved into jewelry. Some anthozoans form fleshy colonies with large polyps and no has skeletons . Examples of these are the soft corals , sea pens