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Foraminifera are single-celled organisms, members of a phylum or class of Rhizarian protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell of diverse forms and materials. Tests of chitin are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the seafloor sediment, while a smaller number float in the water column at various depths, which belong to the suborder Globigerinina. Fewer are known from freshwater or brackish conditions, and some very few (nonaquatic) soil species have been identified through molecular analysis of small subunit ribosomal DNA.
Globigerina is a genus of planktonic Foraminifera, in the order of Rotaliida. It has populated the world's oceans since the Middle Jurassic.
The Rotaliida are an order of Foraminifera, characterized by multilocular tests (shells) composed of bilamellar perforate hyaline lamellar calcite that may be optically radial or granular.
Alveolinella is a genus of larger fusiform porcelaneous alveolinids from the Miocene to Recent with apertures on the septal face in multiple rows and aligned partitions (septula) dividing the primary chambers. Aveolinella is a larger foraminifer from the milioline family Alveolinidae. Like other miliolines, they have imperforate porcelaneous walls.
Miliolacea is one of five superfamilies belonging to the Miliolida,.
Quinqueloculina is a genus of foraminifera in the family Miliolidae.
Idalina is a genus of foraminifera included in the Hauerinidae, (Miliolida), that lived during the latter part of the Late Cretaceous.
The Spirillinida are an order of foraminifera in which the test, or shell, primitively consists of an enrolled open tube, coming after the proloculus, wound planospirally or conically, commonly composed of an optically single crystal of calcite. The aperture is a simple opening at the end of the tube. Advanced forms with more than one chamber may consist of a few crystals, or rarely, a mosaic of crystals of calcite.
The Robertinida are an order of Middle Triassic to recent, benthic foraminifera in which tests are planispirally to trochospirally coiled, with chambers provided with an internal partition and hyaline perforated walls composed of optically radiated aragonite.
Discorbis is a genus of benthic Foraminifera, that made its first appearance during the Eocene. Its present distribution is cosmopolitan.
Rotalidia comprises a class of Foraminifera where Foraminifera is regarded as a phylum, that unites Foraminifera that have tests composed of secreted lamellar calcium carbonate, optically radial or granular calcite, or aragonite; separating them from those with porcelaneous, agglutinated, or microgranular, tests, or tests composed of organic compounds. Seven orders are included, the:
Triloculina is a genus of foraminifera in the order Miliolida, included in the Quinqueloculininae. The test is three, chambers each a half coil in length. Early chambers, at least in the microspheric generation, in quinqueloculinan arrangement, later becoming triloculine with successive chambers added in planes 120 degrees apart. Only the final three chambers are visible externally. The aperture is terminal, at the end of the final chamber, with a bifid tooth in adult forms. As with the entire order, the test is composed of imperforate, porcelaneous calcite.
Sigmoilina is a miliolid genus, referring to the foraminiferal order Miliolida, characterized by an assymmetricall biconvex test formed by strongly overlapping chambers, one-half coil in length, that form a sigmoid (S-shaped) curve in cross section. The strongly overlapping chambers obliterate earlier ones from view resulting in the compressed biloculine appearance, differing from the squat, depressed biloculine form of Pyrgo and Biloculina. The test, as for all Miliolida, is porcelaneous and imperphorate, the terminal aperture, with tooth, the only point of egress and ingress for the animal.
Sigmoilinita is a miliolid genus (Foraminifera) with an ovate to fusiform test that becomes flattened with growth. Chambers are tubular, one-half coil in length, at first added in a sigmoiline (S-shaped) series starting at slightly more than 180° apart. the angle gradually decreasing until the later whorls are planispiral. Chambers are numerous, the wall narrow. imperforate, porcelaneous. The aperture at the end of the final chamber may have a weakly developed tooth.
Sigmoilinopsis is a genus of miliolid Foraminifera, with an ovate test, chambers one-half coil in length, arranged in rapidly changing planes in the early stage resulting in two spiralling series that appear sigmoid in section, gradually becoming planispiral in the adult. Walls are thick, porcelaneous but enclosing a large quantity of agglutinated quartz particles, sponge spicules, and shell fragments; the aperture terminal, rounded, with a small tooth.
Triloculinella is a genus of Miliolacean forams with a fusiform to asymmetrically globular test. Inner chambers, one-half coil in length, are crypto-quinqueloculine to quinqueloculine in arrangement; The final three to five visible from the exterior. The aperture is an arch at the end of the final chamber, largely covered by a broad apertural flap, which distinguishes the genus from Triloculina, Quinqueloculina and such, characterized by a more narrow tooth. The wall, as for all miliolids, is calcareous, imperforate, porcelaneous.
Miliollata is a class wherein Foraminifera is regarded as a phylum that unites the porcelaneous Miliolida, and siliceous Rzehakinidae based on similarities of their tests. Previously the Rzehakinidae were included in the Textulariina based on test wall composition rather than test form. The meaning of Miliolida is retained.
Miliamminana is a subclass of miliolates established by Mikhalevich, 1980 that combines two groups of foraminifers with agglutinated tests. They are the Rzehakinidae which previously were included in the Texulariina in the Treatise on Invertebrate Paleontology although milioline in form, and the milioline Schlumbergerinida which includes genera removed from the Miliolina. The rzehakinids are composed of finely agglutinated material, insoluble in acid, over an organic base. Schlumbergerinids are composed of acid soluble agglutinated material over a porcelenous base. The unifying character is the nature of their coiling in which there are two tubular chambers, or sections, per whorl arranged in various planes and the fact that they are in part all agglutinated.
Tubothalamea is a taxonomic class established for foraminiferans with tubular chambers. Includes the porcelaceous and agglutinated Miliolida and the monocrystalline and agglutinated Spirillinida. It is one of two classes of multichambered foraminifera based on SSU rDNA molecular studies with consideration of major morphological trands, the other being the Globothalamea.
Foraminiferal tests are the tests of Foraminifera.
References
- Miliolata-Foraminifera
- Alfred R Loeblich jr & Helen Tappan,1964. Treatise on Invertebrate Paleontology, Part C, Protista 2; Sarcodina, chiefly "Thecamoibians" and Foraminiferida. Geological Society of America and University of Kansas Press.
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