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Foraminifera (, Latin meaning ''hole bearers'', informally called "forams") are members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm that among other things is used for catching food, and commonly by an external shell or "test" made of various materials and constructed in diverse forms. All but perhaps a very few are aquatic and most are marine, the majority of which live on or within the seafloor sediment (i.e., are benthic) while a smaller variety are floaters in the water column at various depths (i.e., are planktonic). A few are known from freshwater or brackish conditions and some soil species have been identified through molecular analysis of small subunit ribosomal DNA. Foraminifera typically produce a test, or shell, which can have either one or multiple chambers, some becoming quite elaborate in structure. These shells are commonly made of calcium carbonate () or agglutinated sediment particles. Over 10,000 species are recognized, both living (8,708) and fossil (1,837). They are usually less than 1 mm in size, but some are much larger, the largest species reaching up to 20 cm. ==Classification-taxonomy== The taxonomic position of Foraminifera has varied since their recognition as protozoa (protists) by Schultze in 1854, there referred to as an order, Foraminiferida. Loeblich and Tappan (1992) re-ranked Foraminifera as a class as it is now commonly regarded. Foraminifera have typically been included in the Protozoa,〔( Tolweb Cercozoa )〕 or in the similar Protoctista or Protist kingdom.〔(European Register of Marine Species )〕〔( eForams-taxonomy )〕 There is compelling evidence, based primarily on molecular phylogenetics, for their belonging to a major group within the Protozoa known as the Rhizaria.〔 Prior to the recognition of evolutionary relationships among the members of the Rhizaria, Foraminifera were generally grouped with other Amoeboids as phylum Rhizopodea (or Sarcodina) in the class Granuloreticulosa. Rhizaria is problematic as it is often called a "supergroup", rather than using an established taxonomic rank such as phylum. Cavalier-Smith defines Rhizaria as an infrakingdom within the Kingdom Protozoa.〔 Some taxonomies put Foraminifera in a phylum of their own, putting them on par with the amoeboid Sarcodina in which they had been placed. Although as yet unsupported by morphological correlates, molecular data strongly suggest that Foraminifera are closely related to the Cercozoa and Radiolaria, both of which also include amoeboids with complex shells; these three groups make up the Rhizaria.〔 However, the exact relationships of the forams to the other groups and to one another are still not entirely clear. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「foraminifera」の詳細全文を読む スポンサード リンク
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