any unicellular organism of the rhizopodan order Foraminiferida (formerly Foraminifera), characterized by long, fine pseudopodia that extend from a uninucleated or multinucleated cytoplasmic body encased within a test, or shell. Depending on the species, the test ranges in size from minute to more than 5 cm (2 inches) in diameter and varies in shape, number of chambers, chemical composition, and surface orientation. Tests of a South Pacific species are large enough to be used as jewelry by oceanic islanders; Nummulite specimens from the Eocene limestones of the Egyptian pyramids often exceed 5 cm in diameter. Foraminiferans inhabit virtually all marine waters and are found at almost all depths, wherever there is protection and suitable food (microscopic organisms)
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