Classification of the Extant Echinodermata
This list also contains links to images.
We welcome updates or corrections to this list.
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 anywere 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 worlds oceans. Many taxa have cosmopolitan
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
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
monotypic (1 genus)
9 valid genera. Members of this family are mostly poriferivorous
and are found exclusively in the Antarctic Ocean (and surrounding
~ 53 valid genera. This family represents an very diverse and
broadly distributed taxa found in all the worlds oceans
at all depths.
2 valid genera.This family is closely related to the Ophidiasteridae.
It includes two genera found thoughout 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
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,
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 autotomy and regeneration (e.g.,
Linckia). Genera Include: Fromia, Linckia, Neoferdina,
Nardoa, Ceratonardoa, Ophidiaster, Tamaria, Phataria, Pharia,
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
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 molluscs.
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 diamter (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 molluscs 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,
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,
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.
Hemieuryalidae Ophionereidae Ophiothricidae
- This is a deep-sea group, historically placed with the Ophiuridae.
- 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.