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Five extant classes of echinoderms are generally recognized: the Asteroidea (starfish, with over 1900 species), Ophiuroidea (brittle stars, with around 2,300 species), Echinoidea (sea urchins and sand dollars, with some 900 species), Holothuroidea (sea cucumbers, with about 1,430 species), and Crinoidea (feather stars and sea lilies, with ...
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.
The flower urchin is a dangerous, potentially lethally venomous species. The spines, long and sharp in some species, protect the urchin from predators. Some tropical sea urchins like Diadematidae, Echinothuriidae and Toxopneustidae have venomous spines. Other creatures also make use of these defences; crabs, shrimps and other organisms shelter ...
Most species in this order have five arms and two rows of tube feet with suckers. There are conspicuous marginal plates on the arms and disc. Some species have paxillae and in some, the main pedicellariae are clamp-like and recessed into the skeletal plates. [110] This group includes the cushion stars, [113] the leather star [114] and the sea ...
Holothurians appear to be the echinoderms best adapted to extreme depths, and are still very diversified beyond 5,000 metres (16,000 ft) deep: several species from the family Elpidiidae ("sea pigs") can be found deeper than 9,500 metres (31,200 ft), and the record seems to be some species of the genus Myriotrochus (in particular Myriotrochus ...
Echinoderms (sea urchins, sea lilies, sea stars, crinoids, ...) are animals in the phylum Echinodermata. There are 5 subphyla, some of them being extinct: †Homalozoa, Crinozoa, Asterozoa, Echinozoa and †Blastozoa.
Echinus is a genus of sea urchins.Sea urchins are echinoderms that are typically spherical or flattened with a covering of spine-like structures. Sea urchins tend to be important members of their ecosystems by grazing on other organisms and stabilizing populations.
Ophiurida have bursae for respiration and excretion, and dorsal and ventral arm shields are present and usually well developed. Arms are unbranched and incapable of coiling vertically.