|Classification of the Extant
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Asteroidea (after Blake, 1987 and Clark and Downey, 1992)
25 valid genera
This is a monotypic family including only the genus Ctenodiscus with five species australis, caudatus, crispatus, orientalis and procurator.
3 valid genera.
This family is monotypic containing only the genus Luidia. Members of this family are burrowers into sandy substrates. Members of this family have anywhere from 5 to 15 arms. Several species in this taxa are of considerable size. One species Luidia superba from the Galapagos is one of the largest asteroids in the world.
Eleven genera This is an entirely deep-sea group inhabiting infaunal habitats. Representatives of this group are found in the deepest of the world’s oceans. Many taxa have cosmopolitan distributions.
This is a monotypic group including only the genus Radiaster with four species. All are found in relatively deep-water.
12 valid genera. Benthopectinids are an exclusively deep-sea taxon of asteroids found in the Atlantic and Pacific Oceans.
This monotypic multi-armed family represents the genus Acanthaster with two species planci and brevispinis. Acanthaster is distributed from the East Pacific (Baja California) to the East coast of Africa. Acanthaster planci is the notorious Crown of Thorns starfish whose mysterious population outbreaks have resulted in a perceived threat to the coral reefs of the southwest Pacific.
This family represents the sole genus Archaster found in the Indo-Pacific. Archaster is an infaunal burrower which superficially resemble members of the family Astropectinidae except that they have suckered tube feet. Archaster engages in a peculiar mating behavior known as pseudocopulation. This occurs when representatives of opposite genders crawl upon one another and spawn, presumably increasing the probability of fertilization.
18 valid genera. Asterinids are found throughout the world in tropical and temperate waters.
3 genera. All of which were formerly included in both the Goniasteridae and the Oreasteridae. They are found only in the tropical East and Indo-Pacific.
monotypic (1 genus)
9 valid genera. Members of this family are mostly poriferivorous and are found exclusively in the Antarctic Ocean (and surrounding areas).
~ 53 valid genera. This family represents an very diverse and broadly distributed taxa found in all the world’s oceans at all depths.
2 valid genera.This family is closely related to the Ophidiasteridae. It includes two genera found throughout the Indo-Pacific with a small population on the Caribbean side of the Panamic seaway. One genus in this family, Thromidia, is one of the largest asteroids in the world with an arm to arm span of ca. 2.5 feet and diameter of approx. 5 inches. Genera Include: Thromidia and Mithrodia
5 Valid genera. Odontasterids apparently feed primarily on encrusting invertebrates, especially poriferans.
19 Valid genera. Oreasterids are represented primarily in the tropical Indo and East Pacific however two species of Oreaster are found in the tropical Atlantic. These large heavily armored asteroids are primarily microherbivores and opportunistic scavengers. They are strikingly colored and are often sought after by the tourist industry for their large and ornate tests.
Genera include: Oreaster, Protoreaster, Pentaster, Culcita, Choriaster, Rosaster, Pentaceraster, Nidorellia, Anthenea
31 Valid genera. Ophidiasterids occur in both Atlantic and Pacific Oceans. The greatest diversity of this group occurs in the Indo-Pacific. Members of this family are often brilliantly colored (e.g., Fromia, Neoferdina). Some ophidiasterids possess remarkable powers of autonomy and regeneration (e.g., Linckia). Genera Include: Fromia, Linckia, Neoferdina, Nardoa, Ceratonardoa, Ophidiaster, Tamaria, Phataria, Pharia, Leiaster,
9 Valid genera.
monotypic (1 genus)
These are an entirely deep-sea taxon which may possibly related to Concentricycloids. They are found only at abyssal depths in the Atlantic and Pacific Oceans.
Myxasterids are reminiscent of pterasterids but are have longer arms. They generally posses more than 5 arms.
Genera include: Myxaster
Pterasterids are found in cold/ temperate but primarily deep-water habitats although there is one taxon which lives in the Indo-Pacific. These asteroids generally possess very short arms relative to their discs and an unusual membrane which is supra-dorsal to the aboral surface of the asteroid itself.
Genera include: Pteraster, Hymenodiscus, Diplopteraster, Retaster,
Solasterid asteroids are often multi-armed. With one exception, most are found in mostly cold/deep-water habitats. Solasterids appear to be predatory/ opportunistic feeders. Genera include: Lophaster, Heterozonias, Solaster, Seriaster
The species complex of Arctic Henricia has long been a challenge to asteroid population biologists. The latter genus, Echinaster is circum- tropical being found in both Pacific and Atlantic oceans.
Asteriids are among the best known and familiar of the asteroids. Representatives of this group includes the well known Atlantic Asterias and NW Pacific Pisaster. Members of this family all possess four rows of tube feet. Several members of this family are voracious predators of bivalve mollusks.
Noteworthy Asteriids include: Asterias amurensis, the asteroid introduced to Tasmania from Northern Japan belongs to this family. Several Asteriids are of considerable size. Pycnopodia helianthoides found on the Pacific Northwest coast of North America can attain a diameter (arm to arm) of almost 3 feet!! Specimens of Pisaster brevispinis and Stylasterias forreri can have a diameter (arm to arm) of approx. 2 feet.
This monotypic family represents the genus Heliaster found from Baja California and along the coast of South America and out to the Galapagos Islands. Heliasterids have 20-35 arms and are intertidal/subtidal predators of small mollusks and barnacles. These form a species complex along their range- the taxonomy of which has yet to be fully resolved.
All members of this family are multi-armed and are found in moderately deep Atlantic and Pacific oceans. At least two members of this family, Rathbunaster and Labidiaster can catch small crustaceans with their arms and pedicellariae.
Genera included in this family: Coronaster, Rathbunaster, Labidiaster, Plazaster
Zoroasterids are found only in deep-sea habitats. They possess long spindly arms. Fossil zoroasterids from Antarctica (Blake and Zinsmeister, 1983) show that some taxa existed in a shallower warmer habitat before 'moving' into deep-water habitats.
Brisingids are a group of exclusively deep-sea asteroids. They are most closely related to the Forcipulatida and are unusual in possessing 6 or more arms, (usually 12 to 18) and a fused oral disc. Brisingids are suspension feeders. They hold their long, attenuate arms into the water column using high densities of pedicellariae on their arm spines which act as “velcro” to catch small prey. (Emson and Young, 1994) One brisingid, Midgardia xandaros Downey, 1970 possess the longest arm span of any known asteroid.
Genera include: Astrolirus, Astrostephane, Brisinga, Brisingaster, Stegnobrisinga, Midgardia, Brisingenes, Hymenodiscus/ Brisingella, Parabrisinga, Novodinia
Genera include Colpaster, Freyella, Freyastera, Freyellaster
Concentricycloids or "sea daisies" are an enigmatic group of echinoderms discovered in 1986 from deep-water off New Zealand on woody debris. This taxa contains the single genus Xyloplax with two species, one in the Pacific and one in the Atlantic. Positive determination of the sister taxon to the concentricycloids remains elusive although evidence suggests a relationship with asteroids.
This is a deep-sea group, historically placed with the Ophiuridae.
Hemieuryalidae Ophionereidae Ophiothricidae
Ophiothricids are apparently successful in the tropical Pacific. Several taxa are epizoic on octocorals and other invertebrates. Tropical members of this family are also very colorful, often retaining their stunning purples and reds after preservation.
Deep-water and tropical echinoids.
Elasipodida These all represent exclusively deep-sea fauna.