Feather stars are echinoderms in the class Crinoidea. The juveniles attach to the substrate by a stalk with rootlike branches. The mouth side faces upward. In the adult stage they break away from the stalk and move about freely.They possess appendages, known as cirri, attached to the underside of the body with which they cling to to sponges or corals. Some can swim by undulating movements of the arms. Some have five arms, others up to 200.