Starfish (also called sea stars) belong to the class Asteroidea, a diverse group with roughly 1,900 species found across every ocean—from the Arctic and Atlantic to the Pacific, Indian, and Southern (Antarctic) oceans. They occupy an impressive range of habitats, from intertidal shores to abyssal depths.
Most sea stars are generalist predators or scavengers. Many target slow-moving or sessile animals that struggle to escape, such as bivalves and other benthic invertebrates. To help you understand the main “types” of starfish, this guide summarizes the major orders and highlights representative examples from each.
Table of Contents
Brisingida
Notomyotida
Paxillosida
Spinulosida
Forcipulatida
Velatida
Valvatida
Other Notable Starfish Species
Brisingida
Brisingida includes two families (Brisingidae and Freyellidae) with about 16 genera and roughly 112 species. These sea stars are best known from deep waters, though some species also appear in shallow Antarctic environments.
Key characteristics
Small, stiff central disc with a firm structure.
6 to 20 long, slender arms often used for suspension feeding.
Long spines along the arms, giving them a “bristly” appearance.
Specialized skeletal features, including fused disc plates and a distinctive ambulacral column.
In some species, tube feet may have rounded tips and lack strong suction.
Representative species
Colpaster edwardsi
Novodinia americana
Hymenodiscus coronata
Freyella elegans
Brisinga endecacnemos
Notomyotida
Notomyotida is a smaller order with a single family, Benthopectinidae, containing about 12 genera and around 75 species. These sea stars are strongly associated with deep-sea habitats.
Key characteristics
A reticulated internal skeleton (net-like endoskeletal structure).
Five very long arms that are dorsoventrally flattened and tapered.
Papulae (skin gills) concentrated near the proximal arm regions.
Arms are flexible, supported by longitudinal muscle bands on the inner dorsolateral surfaces.
Well-developed plate series, including abactinal, actinal, superomarginal, oral, and adambulacral plates.
Representative species
Myonotus intermedius
Pectinaster agassizi
Benthopecten acanthonotus
Acontiaster bandanus
Cheiraster echinulatus
Paxillosida
Paxillosida includes eight families (such as Astropectinidae, Ctenodiscidae, Luidiidae, Porcellanasteridae, and others), with about 46 genera and roughly 255 species. Many members are adapted to sandy sea floors and are skilled at burrowing.
Key characteristics
Typically have five or more arms, aiding movement and digging in sediment.
Papulae present on the abactinal (upper) surface.
Tube feet arranged in two rows, often conical, with a rudimentary sucker.
Inferomarginal plates commonly carry spines and may project as points or scales.
Representative species
Gephyreaster (genus)
Abyssaster planus
Ctenodiscus australis
Astropecten jonstoni
Luidia bellonae
Spinulosida
Spinulosida is represented mainly by the family Echinasteridae, containing about 9 genera and around 120 species. This order is found across polar, temperate, and tropical regions, from intertidal zones to deep waters.
Key characteristics
The abactinal surface is covered in spines of varied sizes.
Small central disc with five cylindrical arms.
Marginal plates are often not externally obvious.
Actinolateral plates are well developed and tend to form parallel series.
Representative species
Metrodira subulata
Henricia sanguinolenta
Odontohenricia violacea
Rhopiella hirsuta
Echinaster colemani
Forcipulatida
Forcipulatida is a large and widespread order with six families (including Asteriidae, Heliasteridae, Labidiasteridae, and others), about 68 genera, and roughly 300 species. Members occur globally in cold and tropical waters.
Key characteristics
Often show conspicuous forcipulate pedicellariae on the body surface (tiny pincer-like structures).
Numerous, small, and compressed ambulacral plates.
Abactinal plates are not paxilliform and not strongly scale-like.
Marginal plates are typically not prominent.
Tube feet are commonly arranged in four rows and end in a terminal sucker.
Representative species
Asterias rubens
Allostichaster capensis
Labidiaster annulatus
Coscinasterias tenuispina
Ampheraster alaminos
Velatida
Velatida includes several families (such as Caymanostellidae, Korethrasteridae, Myxasteridae, and others), around 25 genera, and roughly 200 species. Most are associated with deep-sea environments.
Key characteristics
A robust body with five or more arms.
Carinal plates are often not clearly differentiated.
Intermarginal plates occur only in some species.
Actinolateral plates are usually weakly developed.
Wide, prominent oral plates.
Adambulacral and ambulacral plates are generally not strongly compressed.
Representative species
Asthenactis australis
Caymanostella phorcynis
Belyaevostella hispida
Korethraster hispidus
Euretaster attenuatus
Valvatida
Valvatida is one of the most diverse sea star orders. It includes many families (such as Acanthasteridae, Archasteridae, Asterinidae, Asterodiscididae, Chaetasteridae, and others), totaling about 165 genera and more than 695 species.
Key characteristics
Body forms are often stout, bulky, or large.
Marginal ossicles (skeletal elements along the edge) are typically obvious.
The abactinal skeleton has tightly fitted plates that may be flat, table-like, paxilliform, and often bear spines or granules.
Arms can be short and broad, though some species have more cylindrical arms.
Representative species
Linckia guildingi
Diabocilla clarki
Pentaster obtusatus
Protoreaster nodosus
Heterozonias alternatus
Other Notable Starfish Species
The world’s oceans contain far more sea stars than any short list can cover. Sea stars are also among the most studied benthic invertebrates because of their ecological influence and their remarkable ability to regrow arms after injury or loss.
Additional examples of sea stars
Bythiolophus acanthinus (Acanthinus sea star)
Marthasterias glacialis (Common spiny star)
Echinaster sepositus (Red sea star)
Pycnopodia helianthoides (Sunflower sea star)
Asterina gibbosa (Captain star)
Luidia ciliaris (Luidia sea star)
Ophidiaster ophidianus (Purple sea star)
Astropecten irregularis (Sand star)
Astropecten bispinosus (Bispinose sand star)
Astropecten acanthifer (Acanthifer sand star)
