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.
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.
Culcita is a genus of sea stars. They are found in tropical waters. Some are kept in home aquariums.
The Brisingids are deep-sea-dwelling starfish in the order Brisingida.
Elasipodida is an order of sea cucumbers. They have numerous appendages, including conical papillae and leaf-like tentacles. Although many species are benthic, a number are pelagic, and may have their appendages modified to form sails or fins. Most members of the order inhabit deep-sea environments, such as the species of the genus Enypniastes.
Cidaridae is a family of sea urchins in the order Cidaroida.
The Oreasteridae are a family of sea stars in the class Asteroidea.
Archasteridae is a family of starfish found in shallow waters in the tropical Indo-Pacific region. The genus Astropus, previously included in this family, is now included in the genus Archaster with the single species, Astropus longipes, being accepted as Archaster lorioli Sukarno & Jangoux, 1977.
Stylasterias is a genus of starfish in the family Asteriidae. Stylasterias forreri, the velcro star, is the only species in the genus. It is found on the Pacific coast of Canada and the United States.
Orthasterias is a genus of sea stars in the family Asteriidae. Orthasterias koehleri, the rainbow star or red-banded sea star, is the only species in the genus. It is found in the North Pacific Ocean.
Hippasteria is one of 70 genera of sea stars in the diverse family Goniasteridae.
Fromia is a genus of starfish belonging to the family Goniasteridae.
The Zoroasteridae are one of three families of Asteroidea in the order Forcipulatida. It contains seven living genera and one extinct genus.
Pelagothuria is a genus of sea cucumbers in the family Pelagothuriidae. It is monotypic, being represented by the single species Pelagothuria natatrix.
Evoplosoma is a genus of deep-sea sea star in the family Goniasteridae.
Mediaster is a genus of starfish in the family Goniasteridae. It was circumscribed in 1857 by William Stimpson for M. aequalis, the genus's type species. Its junior synonym is the genus Isaster, which was circumscribed in 1894 by Addison Emery Verrill for the species now known as M. bairdi. Verrill himself synonymized the two genus names in 1899.
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.
Glyphodiscus is a genus of echinoderms belonging to the family Goniasteridae.
