any of the 550 living species of crinoid marine invertebrates (class Crinoidea) of the phylum Echinodermata lacking a stalk. The arms, which have feathery fringes and can be used for swimming, usually number five. Feather stars use their grasping “legs” (called cirri) to perch on sponges, corals, or other substrata and feed on drifting microorganisms, trapping them in the sticky arm grooves. Feather stars traditionally belong to a single order (Comatulida) and are often referred to as “comatulids”; however, some authorities divide these animals into several orders.