The Echinoderms
Phylum Echinodermata: 5 classes
- Class Asteroidea: sea stars or starfishsize from inch to yard, important predators (e.g. reefs), in coastal areas and in deep-sea
- Class Ophiuroidea: brittle starslargest and most abundant class, coastal areas and deep-sea
- Class Echinoidea: sea urchins & sand dollarssolid skeleton of fused calcite plates
- Class Holothuroidea: sea cucumberssize from inch to 2 m; 90% of deep-sea trench fauna biomass
- Class Crinoidea: feather stars and sea liliessessile; 5 to many arms, probably oldest class