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(fərăm'ənĭf`ərən), common name for members of the class Foraminifera, large, shelled ameboid protozoansprotozoan
, informal term for the unicellular heterotrophs of the kingdom Protista. Protozoans comprise a large, diverse assortment of microscopic or near-microscopic organisms that live as single cells or in simple colonies and that show no differentiation into tissues.
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 belonging to the phylum Sarcodina. Most foraminiferan shells are calcareous, but some are siliceous, and others are built of sand grains. Initially, the shell contains a single chamber, and new chambers are added in a characteristic linear, spiral, or concentric series as the organism grows. Some shells reach several inches in diameter, but most species are less than a millimeter in diameter. Long, branching extensions of the cell (pseudopodia) reach from openings in the shell and fuse together to form a net in which plankton organisms are trapped. The net may cover an area 10 times the diameter of the shell, and crustaceans of 1 in. (2.5 cm) or more long may be caught by these much smaller protozoans.

A few foraminiferans live in freshwater or brackish water, but the majority are marine. They are found in all seas at all depths and are extremely abundant. Foraminiferans may be red, brown, or white in color. About 30 pelagic species live in the open sea, the most important belonging to the genus Globigerina.

Foraminiferans live near the water surface when young, but gravitate downward with age. When the animals die, the shells drop to the bottom, forming "globigerina ooze." Such ooze constitutes about half the sediments found on the roughly 50 million sq mi (130 million sq km) of ocean bottom that is covered with sediment in warm and tropical seas. Similar deposits in the past have contributed heavily to the formation of sedimentary rock, and the study of fossil foraminiferans has been extremely important in recognizing geological strata and for dating deposits. Layers of limestone or chalk, such as are found in Dover, England, and in Alabama and Mississippi, solidified from similar deposits of ooze in ancient seas. Foraminiferan fossils have been particularly useful in locating domes where petroleum deposits occur. Limestone used in some Egyptian pyramids contains skeletons of foraminiferans, especially of nummulites, which have coin-shaped skeletons.

Foraminiferans are classified in the phylum SarcodinaSarcodina,
the largest phylum (11,500 living species and 33,000 fossil species) of protozoans). It comprises the amebas and related organisms; which are all solitary cells that move and capture food by means of pseudopods, flowing temporary extensions of the cell.
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, class Granuloreticulosa.

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References in periodicals archive ?
Among many foraminiferans with an organic shell, they found four undescribed specimens with agglutinated tests.
(2002) studied Albian--Maastrichtian palaeotemperatures using isotopic analyses of foraminiferans from Blake Nose.
A bush, not a tree: the extraordinary diversity of cold-water basal foraminiferans extends to warm-water environments.
Several qualitative studies document the large contribution of benthic foraminiferan tests in carbonate sands of the central GBR (Scoffin and Tudhope, 1985).
The planktic foraminiferans are well known to be affected by even slight climatic fluctuations, and their fossilized calcareous shells are capable of holding a perfect record of such changes.
In every sample, there are tens of thousands of protists, including amoebae, ciliates, foraminiferans, flagellates, and dinoflagellates.
Until today, the seas have been calm enough that staring at tiny living creatures magnified 12 or 50 times in petri dishes full of deoxygenated water has been a hypnotic, through-the-rabbit-hole exercise: foraminiferans like frosted Christmas-tree ornaments, spaghetti worms like exploded dissections gone bad, snails wearing circa-1960 bathing caps with bobbing bacterial filaments, all amid a snow-globe blizzard of gold, mica, and dragonfly-iridescent flakes.
Other acid-resistant microfossils encountered during this study include acritarchs, foraminiferans, melanoscleritoids, chitinous hydroids, and graptolite siculae, but these were not studied quantitatively.
Based upon benthic foraminiferans, Durham and Yerkes (1964) placed a late Miocene (upper Mohnian) age to the Yorba Member of the Puente Formation.
Monitoring bioremediation after oil spills, old and new, using marsh foraminiferans as indicators
The first factor had strong loadings for crustacean meiofauna (0.96), foraminiferans (0.96), bivalves (0.84), macroalgae (0.82), amphipods (0.78), and rock crab (-0.71).
Class 2 Foraminifera (Reticulopodate with Shell, Foraminiferans, Forams) Phylum 4 Xenophyophora (Large Deep-Sea Benthic Protoctists)