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Foraminifera are single-celled organisms, members of a phylum or class of amoeboid 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. 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.
The Globigerinina is a suborder of foraminiferans that are found as marine plankton. They produce hyaline calcareous tests, and are known as fossils from the Jurassic period onwards. The group has included more than 100 genera and over 400 species, of which about 30 species are extant. One of the most important genera is Globigerina; vast areas of the ocean floor are covered with Globigerina ooze, dominated by the shells of planktonic forms.
The Allogromiida is an order of single-chambered, mostly organic-walled foraminiferans, including some that produce agglutinated tests (Lagynacea). Genetic studies indicate that some foraminiferans with agglutinated tests, previously included in the Textulariida or as their own order Astrorhizida, may also belong here. Allogromiids produce relatively simple tests, usually with a single chamber, similar to those of other protists such as Gromia. They are found as both marine and freshwater forms, and are the oldest forms known from the fossil record.
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.
The Textulariida are an order of foraminifera that produce agglutinated shells or tests. An agglutinated test is one made of foreign particles glued together with an organic or calcareous cement to form an external shell on the outside of the organism. Commonly, the order had been made up of all species of Foraminifera with these types of shells, but genetic studies indicate these organisms do not form an evolutionary group, and several superfamilies in the order have been moved to the order Allogromiida. The remaining forms are sometimes divided into three orders: the Trochamminida and Lituolida, which have organic cement, and the Textulariida sensu stricto, which use a calcareous cement. All three orders or superfamilies are known as fossils from the Cambrian onwards.
Carterina is a genus in the Carterinida. The type species is Carterina spiculotesta Brady, 1884. The genus is described from specimens gathered during the Challenger expedition's circumnavigation of the Earth from 1872-1876.
Carterinida is an order of multi-chambered foraminifera within the Globothalamea. Members of this order form hard tests out of thin calcite rods known as spicules, which are held together by a proteinaceous matrix.
Abadehella is a genus of large Upper Permian benthic forams in the order Fusulinida. Their outer test is conical, up to 1.35mm at the concave base, coiled trochospirally with up to twenty whorls, each with one and a half to two low chambers surrounding the open umbilicus. Chambers are subdivided by close, evenly spaced radial beams. The test wall is calcareous and two-layered, with an external wall with an outer dark microgranular layer and an inner light fibrous layer, septa and beams with a single micro-granular layer. The aperture from each chamber opens into the umbilical region beneath a short projection.
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.
Cibicides is a genus of cosmopolitan benthic foraminifera known from at least as far back as the Paleocene that extends down to the present.
Discorbis is a genus of benthic Foraminfera, that made its first appearance during the Eocene. Its present distribution is cosmopolitan.
Neoconorbina is a genus of recent (Holocene) discorbacean foraminifers related to Rosalina with a low conical trochoidal test, circular in outline. The conical side is the spiral side, on which all three whorls are visible, the final chamber taking up most of the periphery. The umbilical side is flat to concave. exposing only the three to four chambers of the final whorl around an open umbilicus. Chambers on the umbilical side have triangular to platelike umbilical extensions as with other rasalinids. The wall of is calcite, finely and densely perforate on the spiral side, more coarsely perforate on the umbilical side; surface smooth; aperture at the umbilical margin of the chamber, beneath the platelike extension, or folium.
The Cassidulinacea is a superfamily of benthic amoeboid foraminifera in the order Rotaliida that has been extant from the Paleocene down to the present. Tests are composed of secreted, optically radial or granular, perforate calcite with chambers biserially coiled at least in the early part, Apertures are usually an interiomarginal slit, but may become terminal and may have secondary features.
The Planorbulinacea are a superfamily of rotalliid foraminifera that has been extant since the Early Cretaceous (Berriasian), characterized by trochospiral tests, at least in early stage but which later may become uncoiled. The test wall is of perforate hyaline calcite, commonly optically radial in structure, with crystallographic c-axes perpendicular to the surface. The apertural face may be imperforate; the aperture interiomarginal and extraumbilical-umbilical to nearly equatorial in coiled forms, subterminal in uncoiled forms.
The Textulariacea is a superfamily of Middle Jurassic to Holocene agglutinated benthic textulariid Foraminifera. Tests are trochospiral, triserial, or biserial in early stages; later may be biserial or uniserial. Walls are agglutinated, made of gathered material cemented together and are canaliculate - contain micro-tubular cavities extending between the inner and outer surfaces.
The Buliminida is an order of mostly benthic foraminifera with tests commonly of perforate, hyaline, radially laminated calcite, with chambers arranged biserially or triserially, at least in the early stages. Superfamilies include the Bolivinacea, Buliminacea, Eouvigerinacea, and Turrilinacea.
Sigmoilina ia 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.
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.
Globigerinana are free living pelagic foraminiferan, included in the class Rotaliata that range from the Jurassic to recent. Test are commonly planospiral or trochospiral but may be uniserial to multiserial and are of secreted hyaline (glassy) calcite. Chambers are flattened in planospiral forms and spheroidal in trochospiral and serial forms. Some have long radial spines, or needles that may be solidly fixed or moveable in sockets. Gametes are biflagellate and are produced in greater number than by bottom dwelling benthic forms.
References
- Loeblich, Alfred R.; Tappan, Helen (1964). Moore, R.C. (ed.). Protista 2: Sarcodina Chiefly "Thecamoebians" and Foraminiferida. Treatise on Invertebrate Paleontology. C (5th ed.). Geological Society of America. ISBN 978-0-8137-3003-5. .
- Gupta, Barun K. Sen (2002). Modern Foraminifera. Springer. pp. 16–. ISBN 978-1-4020-0598-5.
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