The Euryalida are an order of

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

s, which includes large species with either branching arms (called "basket stars") or long and curling arms (called "snake stars").

Characteristics

Many of the species in this order have characteristic repeatedly branched arms (a shape known as "basket stars", which includes most Gorgonocephalidae and two species in the family

Euryalidae Euryalidae is a family of echinoderms belonging to the order Euryalida. Genera Genera: * '' Asteromorpha'' Lütken, 1869 * '' Asteroschema'' Örsted & Lütken, 1856 * '' Asterostegus'' Mortensen, 1933 * '' Astrobrachion'' Doederlein, 1927 * '' ...

), while the other species have very long and curling arms, and go rather by the name of "snake stars" (mostly abyssal species). Many of them live in

deep sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres (656 feet) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combin ...

habitats or cold waters, though some basket stars can be seen at night in shallow tropical reefs. Most young basket stars live on specific type of coral. In the wild they may live up to 35 years. They weigh up to Like other

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

s, basket stars lack blood and achieve gas exchange via their water vascular system. The basket stars are the largest ophiuroids with '' Gorgonocephalus stimpsoni'' measuring up to 70 cm in arm length with a disk diameter of 14 cm.

Systematics and phylogeny

The fossil record of this group is rather poor and only dates back to

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...

. Basket stars are divided into the following families: * family

Asteronychidae Asteronychidae is a family of echinoderms belonging to the order Euryalida The Euryalida are an order of brittle stars, which includes large species with either branching arms (called "basket stars") or long and curling arms (called "snake star ...

Ljungman, 1867 -- 4 genera (11 species) * family

Gray, 1840, emended Okanishi et al., 2011 -- 11 genera (89 species) * family Gorgonocephalidae Ljungman, 1867 -- 34 genera (96 species) ** sub-family Astrocloninae Okanishi & Fujita, 2018 ** sub-family Astrothamninae Okanishi & Fujita, 2013 ** sub-family Astrotominae Matsumoto, 1915 ** sub-family Gorgonocephalinae Döderlein, 1911 Image:Astrodia tenuispina (MIIC-01651).jpg, '' Astrodia tenuispina'' (

) Image:Astroceras aurantiacum.jpg, '' Astroceras aurantiacum'' (

) Image:Basket star on sea fan at Fan Reef DSC08990.JPG, '' Astrocladus euryale'' ( Gorgonocephalidae) Image:Squamophis lifouensis.jpg, '' Squamophis lifouensis'' (

, ex- Astrocharidae)

Gallery

File:Basket Star in the Atlantic Ocean at 28m near Maori Bay.jpg, A basket star, located in an area known as "Star Wall", near Maori Bay, New Zealand at a depth of approximately 28 m. File:Close-up of basket star arm fragment in the Red Sea.JPG, Close-up of '' Astroboa nuda'' basket star arm File:BasketStar NOAA.jpg, Basket star taken from the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

Image:Asteroschematidae Hawaii 01.jpg, An abyssal snake star curled around a cold-water coral. Image:Euryale aspera (MIIC-01520).jpg, Beware of the genus ''

Euryale In Greek mythology, Euryale ( ; grc, Εὐρυάλη, lit=far-roaming") was the name of the following characters: * Euryale (Gorgon), Euryale, one of the Gorgons. * Euryale, daughter of Minos, possible mother of the great hunter Orion (mythology) ...

'', the only "basket star" not belonging to the Gorgonocephalidae (family

References

External links

* Ophiuroidea Phrynophiurida {{Ophiuroidea-stub