According to one common classification, six principle groups of echinoderms (phyla Echinodermata, from the Greek terms echina, meaning “spiny,” and derma, meaning “skin”) exist: 1) class Crinoidea (sea lilies and feather stars); 2) class Asteroidea (sea stars, also called starfish); 3) class Ophiuroidea (basket stars and brittle stars); 4) class Eichinoidea (sea urchins and sand dollars); 5) class Holothuroidea (sea cucumbers); and 6) class Concentricycloidea (sea daisies that live on waterlogged wood in the deep ocean and were first discovered in 1986).