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The Mississippian is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earlier/lower of two subperiods of the Carboniferous period lasting from roughly 358.9 to 323.2 million years ago. As with most other geochronologic units, the rock beds that define the Mississippian are well identified, but the exact start and end dates are uncertain by a few million years. The Mississippian is so named because rocks with this age are exposed in the Mississippi Valley.
Xenophyophorea is a clade of foraminiferans. Members of this class are multinucleate unicellular organisms found on the ocean floor throughout the world's oceans, at depths of 500 to 10,600 metres. They are a kind of foraminiferan that extracts minerals from their surroundings and uses them to form an exoskeleton known as a test.
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 Rhizaria are a species-rich supergroup of mostly unicellular eukaryotes. Except from the Chlorarachniophyte and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthethic, but many foraminifera and radiolaria have a symbiotic relationship with unicellular algae. A multicellular form, Guttulinopsis vulgaris, a cellular slime mold, has also been described. This supergroup was proposed by Cavalier-Smith in 2002. Being described mainly from rDNA sequences, they vary considerably in form, having no clear morphological distinctive characters (synapomorphies), but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods. Many produce shells or skeletons, which may be quite complex in structure, and these make up the vast majority of protozoan fossils. Nearly all have mitochondria with tubular cristae.
Gromia is a genus of protists, closely related to foraminifera, which inhabit marine and freshwater environments. Gromia are ameboid, producing filose pseudopodia that extend out from the cell’s proteinaceous test through a gap enclosed by the cell’s oral capsule. The test, a shell made up of protein that encloses the cytoplasm, is made up of several layers of membrane, which resemble honeycombs in shape — a defining character of this genus.
The Fusulinida is an extinct order within the Foraminifera in which the tests are composed of secreted hyaline calcite. Like all forams, they were single-celled organisms. In advanced forms the test wall was differentiated into two or more layers. Loeblich and Tappan, 1988, gives a range from the Lower Silurian to the Upper Permian, with the fusulinid foraminifera going extinct with the Permian–Triassic extinction event. While the latter is true, a more supported projected timespan is from the Mid-Carboniferous period.
The Miliolida are an order of foraminifera with calcareous, porcelacous tests that are imperforate and commonly have a pseudochitinous lining. Tests are composed of randomly oriented calcite needles that have a high proportion of magnesium along with organic material. Tests lack pores and generally have multiple chambers.
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.
The slender catshark is a small species of catshark belonging to the family Scyliorhinidae. It is found on the upper continental slope off the coast of Suriname, French Guiana and northern Brazil, including the mouth of the Amazon River at depths between 72 to 450 metres. Its it can grow up to a length of 70 centimetres (28 in).
Lukas Hottinger was a paleontologist, biologist and geologist. Hottinger collaborated with the Natural History Museum of Basel (Switzerland).
Harold John Finlay was a New Zealand palaeontologist and conchologist. He was born in Comilla, India, on 22 March 1901.
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.
Globigerina bulloides is a species of heterotrophic planktonic foraminifer with a wide distribution in the photic zone of the world's oceans. It is able to tolerate a range of sea surface temperatures, salinities and water densities, and is most abundant at high southern latitudes, certain high northern latitudes, and in low-latitude upwelling regions. The density or presence of G. bulloides may change as a function of phytoplankton bloom successions, and they are known to be most abundant during winter and spring months.
Hedbergella is an extinct genus of planktonic foraminifera from the Cretaceous, described by Loeblich and Tappan, 1961, as:
Test free, trochospiral, biconvex, umbilicate, periphery rounded with no indication of keel or poreless margin; chambers globular to ovate; sutures depressed, radial, straight or curved; wall calcareous, finely perforate, radial in structure, surface smooth to hispid or rugose; aperture an interiomarginal, extraumbilical-umbilical arch commonly bordered above by a narrow lip or spatulate flap, ... Includes species otherwise similar to Praeglobotruncana but which lack a keel or poreless margin, hence is regarded as a separate genus rather than as a subgenus of Praeglobotruncana as by Banner and Blow (1959).
Globigerinoides is an extant genus of shallow-water planktonic foraminifera of family Globigerinidae. First appearing in the Oligocene these foraminifera are found in all modern oceans. Species of this genus occupy the euphotic zone, generally at depths between 10-50m, in waters which cover a range of salinities and temperatures. They are a shorter lived species, especially when compared to Globorotalia genus. As a genus Globigerinoides is widely used in various fields of research including biostratigraphy, isotope geochemistry, biogeochemistry, climatology, and oceanography.
Cyclammina is a genus of foraminifers in the family Cyclamminidae. Most species are extinct, but there are a few that are extant.
"Monothalamea" is a grouping of foraminiferans, traditionally consisting of all foraminifera with single-chambered tests. Recent work has shown that the grouping is paraphyletic, and as such does not constitute a natural group; nonetheless, the name "monothalamea" continues to be used by foraminifera workers out of convenience.
Cassigerinellidae is an extinct family of foraminifera belonging to the superfamily Guembelitrioidea and the suborder Globigerinina.
Cassigerinella chipolensis is an extinct species of foraminifera belonging to the genus Cassigerinella, the family Cassigerinellidae and the suborder Globigerinina.
Acarinina is an extinct genus of foraminifera belonging to the family Truncorotaloididae of the superfamily Globorotalioidea and the suborder Globigerinina. Its fossil range is from the upper Paleocene to the middle Eocene. Its type species is Acarinina nitida.
References
- ↑ Pokorný, V. (1955). Cassigerinella boudecensis n. gen., n. sp. (Foraminifera, Protozoa) z oligocénu zdánického flyse. Vestnik Ustredního Ústavu Geologického, 30: 136-140
- 1 2 3 Cassigerinella, World Foraminifera Database, accessed 27 November 2018