List of echinoderm orders

A brittle star, Ophionereis reticulata

A sea cucumber from Malaysia

Starfish exhibit a wide range of colours.

This List of echinoderm orders concerns the various classes and orders into which taxonomists categorize the roughly 7000 extant species^[1] as well as the extinct species of the exclusively marine phylum Echinodermata.

Subphylum Crinozoa

Class Crinoidea

Crinoid

Subclass Articulata (540 species)
- Order Bourgueticrinida
- Order Comatulida
- Order Cyrtocrinida
- Order Hyocrinida
- Order Isocrinida
- Order Millericrinida
Subclass †Flexibilia
Subclass †Camerata
Subclass †Disparida

Comaster schlegelii (Comatulida)
Holopus sp. (Cyrtocrinida)
Encrinus liliiformis (Encrinida)
Calamocrinus diomedae (Hyocrinida)
Proisocrinus ruberrimus (Isocrinida)
Liliocrinus polydactylus (Millericrinida)

Haeckel Cystoidea

Class Paracrinoidea †

No orders, 13 to 15 genera are known.

order Comarocystitida †
- ?Family Heckeritidae †
  - Heckerites †
- Family Amygdalocystitidae †
  - Achradocystites † Volborth, 1870
  - Amygdalocystites † Billings, 1854 (= Ottawacystis) (?= Billingsocystis)
  - Oklahomacystis † Parsley & Mintz, 1975 (Bassler, 1943)
  - Ovulocystites † Frest et al., 1980
- Family Comarocystitidae † Balther, 1899
  - Comarocystites † Billings, 1854
  - Implicaticystis †
  - Sinclairocystis †
order Platycystitida †
- Family Platycystitidae †
  - Canadocystis † (= Sigmacystis)
  - Platycystites †
- Family Malocystitidae †
  - Malocystites †
  - Wellerocystis †
- Family Bistomiacystitidae †
  - Bistomiacystis †

Doubtful paracrinoids:

Columbocystis
Foerstecystis
Springerocystis
Ulrichocystis
Paleocystites
Allocystites

Class Cystoidea

Class Edrioasteroidea †

Streptaster vorticellatus (Edrioasteroidea)

order Edrioasterida
order Isorophida

Subphylum Asterozoa

Class Ophiuroidea (Brittle stars)

Astroboa nuda (Euryalida)
Ophiura ophiura (Ophiurida)
Ophiolepis elegans (Amphilepidida)
Ophiocoma erinaceus (Ophiacanthida)
Ophioleuce seminudum (Ophioleucida)
Ophiomyces frutectosus (Ophioscolecida)

Class Asteroidea (Starfish)

Infraclass Concentricycloidea
- Peripodida
Superorder Forcipulatacea
- Brisingida
- Forcipulatida
Superorder Spinulosacea
- Spinulosida
Superorder Valvatacea
Velatida^[2]
† Calliasterellidae
† Trichasteropsida

Subphylum Echinozoa

Class Echinoidea (Sea urchins)

Strongylocentrotus purpuratus, a well-armoured sea urchin

Superorder Diadematacia
- Order Diadematoida
- Order Echinothurioida
- Order Pedinoida
Superorder Echinacea
- Order Arbacioida
- Order Echinoida
- Order Phymosomatoida
- Order Salenioida
- Order Temnopleuroida
Superorder Gnathostomata
- Order Clypeasteroida (sand dollars)
- Order Holectypoida
Superorder Atelostomata
- Order Holasteroida
- Order Spatangoida (heart urchins)

Class Holothuroidea (Sea cucumbers)

Order Apodida
Order Dendrochirotida
Order Elasipodida
Order Holothuriida
Order Molpadida
Order Persiculida
Order Synallactida

Class Ophiocistioidea †

Euthemon

No orders recognized: class is divided up into four families, Eucladiidae, Sollasiniidae, Volchoviidae, and Rhenosquamidae. The inclusion of Rhenosquamidae within Ophiocistioidea is doubtful, as the organs identified in fossils of Rhenosquamus as the characteristic "scaly podia" otherwise diagnostic of ophiocistioids may not, in fact, be such structures.

Class Helicoplacoidea †

No known orders, 2 known species, Helicoplacus curtisi and H. guthi

Subphylum Blastozoa

Class Blastoidea †

Blastoidea

Order Coronata †
Order Fissiculata †
Order Spiraculata †
basal Macurdablastus †

Class Eocrinoidea †

Gogia spiralis (Eocrinoidea)

Order Ascocystida †
Order Gogiida †
Order Imbricata †
Order Trachelocrinida †

Subphylum Homostelea / Homalozoa †

Corthurnocystis, a Stylophora.

Class Ctenocystoidea †

order Ctenocystida †

Class Soluta †

Class Cincta †

Class Stylophora †

order Cornuta †
order Mitrata †

References

^ "Animal Diversity Web - Echinodermata". University of Michigan Museum of Zoology. Retrieved 26 August 2012.
^ Sweet, Elizabeth (2005-11-22). "Asterozoa: Fossil groups: SciComms 05-06: Earth Sciences". University of Bristol. Archived from the original on 2007-07-14. Retrieved 2008-05-07.