Crinoidea is a class of marine animals within the phylum Echinodermata, commonly known as sea lilies or feather stars. These organisms are characterized by their cup-shaped body, called a calyx, and long, feathery arms that are used for feeding and capturing plankton from the water. Crinoids are notable for their ability to attach to the sea floor or swim free and are often found in deep-sea environments. They have a long evolutionary history, dating back to the Cambrian period.
