Crinoidea

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Related to crinoid: 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 ?
The spindly animals with feathery arms--called crinoids, but better known today by the plant-like name sea lily--appear to have been buried alive in storms during the Carboniferous Period, when North America was covered with vast inland seas.
Crinoids are flower-shaped animals that grow on stalks rooted to the ocean floor.
Spatial and temporal distribution of the crinoid Florometra serratissma on the Oregon continental shelf.
In the black marble, the most abundant fossils are crinoid stem segments, but there are also brachiopods, bryozoans, stromatoporoids, cephalopods, gastropods, and corals (Fig.
Systematics and phylogeny of the Late Osagean and Meramecian crinoids Platycrinites and Eucladocrinus from the Mississippian stratotype region.
Unlike the Caribbean and western Atlantic, there are few species that associate with sea anemones, crinoids or sponges.
An accurate field study has revealed brachiopod, separate rugose and colonial coral, bryozoan, crinoids and cephalopod macrofossil frequency;.
Topics include wind erosion in deserts, groundwater age dating, diffusion in solid silicates, crinoid ecological morphology, the Southern Dead Sea Fault, the redox state of Earth's mantle, coastal impacts due to sea-level rise, and the rheology of the lower crust and upper mantle.
The crinoid sculpture is suspended from the ceiling by five ropes incorporating fibre optics, which are fixed to the floor, with the changing colours and movement of the ropes representing the sense of being underwater.
War Eagle Cavern Features an underground stream, an abundance of crinoid fossils, unusual dome pits, onyx and much more.
The crinoid Uintacrinus socialis, an important stratigraphic marker for Late Santonian deposits in the Western Interior and Europe, has now been found in the Tombigbee Sand Member of the Eutaw Formation in Mississippi.