Crinoidea

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Related to Crinoids: class Crinoidea, Sea lilies

Crinoidea:

see EchinodermataEchinodermata
[Gr.,=spiny skin], phylum of exclusively marine bottom-dwelling invertebrates having external skeletons of calcareous plates just beneath the skin. The plates may be solidly fused together, as in sea urchins, loosely articulated to facilitate movement, as in sea
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; feather starfeather star,
common name of a class of echinoderms that, as juveniles, are attached to the sea bottom by a stalk with rootlike branches; the mouth side faces upward. In the adult stage they break away from the stalk and move about freely.
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; sea lilysea lily,
stalked echinoderm of the class Crinoidea. Sea lilies are ancient, having reached their peak in the Middle Mississippian period; about 5,000 fossil species are known. About 80 modern species remain.
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Crinoidea

 

a class of benthic invertebrates of the phylum Echinodermata. They have a cup-shaped body, or calyx, in the middle of which is a mouth; the body is crowned by feathery, generally branching, upwardly directed rays. There are five rays at the base of the calyx and ten or more (up to 200) further up. The loose crown forms a net for catching small planktonic organisms and detritus, upon which the crinoids feed.

Stalked crinoids, or sea lilies, have a segmented stalk, which is up to 1 m long. Fixed to the base of the calyx, the stalk attaches itself to the sea bottom. Stalkless crinoids, or comatulids, have numerous movable processes (cirri) and can crawl and swim. Sea lilies, of which there are approximately 80 species, are found at depths to 9,700 m. Stalkless forms, of which there are about 550 species, are most diverse in the shallow waters of tropical seas and are often brightly colored. Adult invertebrates develop from free-swimming larvae and a sessile stalked stage.

More than 5,000 species of fossil crinoids have been traced to the Lower Ordovician. They reached the height of their development in the Middle Paleozoic (several subclasses). By the end of the Paleozoic, most species had become extinct. The subclass Articulata, to which all extant crinoids belong, has been traced back to the Triassic.

REFERENCES

Zhizn’ zhivotnykh, vol. 2. Moscow, 1968.
Hyman, L. H. The Invertebrates, vol. 4. New York-London, 1955.

Crinoidea

[krə′nȯid·ē·ə]
(invertebrate zoology)
A class of radially symmetrical crinozoans in which the adult body is flower-shaped and is either carried on an anchored stem or is free-living.
References in periodicals archive ?
With long, stem-like bodies topped with feathery fronds, crinoids resembled flowers, though the center of the "flower" was a mouth, and the "petals" were arms that captured plankton for food.
Crinoids, Bivalve, Brachiopodal Sandy Wackestone Facies (MF4): This facies is 8m thick and has two beds.
Because modern-day crinoids usually lose and regenerate their arms as a result of attacks by fish and other marine animals, the scientists reasoned that arm regeneration in fossil crinoids might be an indicator of past predator-prey interactions.
Stalked crinoids are more abundant downslope of the wall on transect AA, for instance, suggesting a greater flux of food in this region.
Fossil goniasterid marginals have been found in calcareous sediments ranging from fine to coarse and are typically accompanied by the stereomate remains of other echinoderms, namely echinoids and crinoids.
Descriptions of two new species of Crustacea, fifty-one species of Mollusca, and three species of crinoids, from the Carboniferous formations of Illinois and adjacent states.
Beringer was completely taken in, and published a Latin monograph (a copy of which was on exhibit) on this fabulous "find" of fossilized ferns, crinoids, spiders, worms and less recognizable fantasy-flora and fauna.
During the great Permian extinction, the crinoids were almost wiped out, but today there are about 540 named species, living at a range of depths down to 6,000 metres; Right: water lilies, Okavango Delta, Botswana.
Other megafaunal invertebrates, such as crinoids, basket stars, and sponges also may enhance the structural components of fish habitat (Puniwai, 2002) and may be disturbed or destroyed by some fishing activities (Freese, 2001; Krieger, 2001).