Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface.
The Valvatida are an order of starfish in the class Asteroidea, which contains 695 species in 172 genera in 17 families.
The Echinasteridae are a family of starfish in the monotypic order Spinulosida. The family includes eight genera and about 133 species found on the seabed in various habitats around the world.
The Asterinidae are a large family of sea stars in the order Valvatida.
Goniasteridae constitute the largest family of sea stars, included in the order Valvatida. They are mostly deep-dwelling species, but the family also include several colorful shallow tropical species.
Asterina is a genus of asteroideans in the family Asterinidae.
The Forcipulatida are an order of sea stars, containing three families and 49 genera.
The Brisingids are deep-sea-dwelling starfish in the order Brisingida.
The Asterozoa are a subphylum in the phylum Echinodermata. Characteristics include a star-shaped body and radially divergent axes of symmetry. The subphylum includes the class Asteroidea, the class Ophiuroidea, and the extinct order Somasteroidea.
The Oreasteridae are a family of sea stars in the class Asteroidea.
Protoreaster is a genus of sea stars in the family Oreasteridae from the Indo-Pacific. They are sometimes seen in the marine aquarium trade.
Thromidia is a genus of starfish in the family Mithrodiidae.
Solaster stimpsoni, common names Stimpson's sun star, sun star, orange sun star, striped sunstar, and sun sea star, is a species of starfish in the family Solasteridae.
Poraniidae is a family of starfishes in the order Valvatida.
The Heliasteridae are a family of Asteroidea in the order Forcipulatida. It includes two genera: Heliaster from the East Pacific, and Labidiaster from southernmost South America, Antarctica and subantarctic oceans.
The Zoroasteridae are one of three families of Asteroidea in the order Forcipulatida. It contains seven living genera and one extinct genus.
Luidia magellanica is a species of starfish in the family Luidiidae. It is found in the southeastern Pacific Ocean on the coast of South America.
Euretaster insignis, commonly known as the striking sea star, is a species of starfish in the family Pterasteridae found in the central west Pacific Ocean. It is one of only three species in the order Velatida to be found in shallow water in the tropics. The young are brooded in a cavity underneath a "supradorsal" membrane.
Maureen Elizabeth Downey was an American zoologist who worked for three decades at the Smithsonian National Museum of Natural History. Known as "The Starfish Lady," she was an authority on sea stars and other echinoderms, co-founding the International Echinoderm Conference in 1972. Among her discoveries is Midgardia xandaros, the world's largest starfish.
Helen Elizabeth Shearburn Rotman was a New Zealand expert on echinoderms, specifically starfish.
