Crinoidea is a class of marine animals within the phylum Echinodermata, commonly known as sea lilies and feather stars. They are characterized by their cup-shaped body and feathery, branched arms that are used for feeding and locomotion. Crinoids are primarily found in deep-sea environments but can also inhabit shallower waters. They are known for their fossil record, with some species dating back to the Cambrian period.
