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.
Stelleroidea is a superclass of marine echinoderms including three classes:
Brittle stars, serpent stars, or ophiuroids are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens.
Eleutherozoa is a proposed subphylum of echinoderms. They are mobile animals with the mouth directed towards the substrate. They usually have a madreporite, tube feet, and moveable spines of some sort. It includes all living echinoderms except for crinoids.
Asterina is a genus of asteroideans in the family Asterinidae.
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.
Thromidia is a genus of starfish in the family Mithrodiidae.
Callopatiria is a genus of starfish of the family Asterinidae. The genus is found in shallow waters off South Africa, down to a depth of about 82 m (269 ft).
Chantal Conand is a French marine biologist and oceanographer.
Fromia ghardaqana, common name Ghardaqa sea star, is a species of marine starfish in the family Goniasteridae.
Patiria chilensis is a species of starfish in the family Asterinidae. It is found in the southeastern Pacific Ocean along the coasts of South America. It is a broadly pentagonal, cushion-like starfish with five short arms.
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.
Meyenaster is a genus of starfish in the family Asteriidae. It is a monotypic genus and the only species is Meyenaster gelatinosus which was first described by the Prussian botanist and zoologist Franz Julius Ferdinand Meyen in 1834. It is found in the southeastern Pacific Ocean on the coasts of South America.
Echinaster luzonicus, the Luzon sea star, is a species of starfish in the family Echinasteridae, found in shallow parts of the western Indo-Pacific region. It sometimes lives symbiotically with a copepod or a comb jelly, and is prone to shed its arms, which then regenerate into new individuals.
Ailsa McGown Clark (1926–2014) was a British zoologist, who principally studied echinoderms and was a specialist on asteroidea. She worked at the Natural History Museum for most of her career.
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.
Euryalidae is a family of echinoderms belonging to the order Euryalida.
Helen Elizabeth Shearburn Rotman was a New Zealand expert on echinoderms, specifically starfish.
Thromidia gigas is a species of starfish in the family Mithrodiidae. It was described by Ole Theodor Jensen Mortensen in 1935. It lives in the Indian Ocean off the coast of eastern South Africa and southern Madagascar. This species is probably the largest echinoderm in terms of bulk, and may exceed 13 pounds (5.9 kg).
Luidia neozelanica is a species of starfish in the family Luidiidae. It is found in the southwestern parts of the Pacific Ocean off Australia, New Zealand and the Kermadec Islands.
