Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typically around 1 mm (0.039 in) in size, but varying from 0.2 to 30 mm (0.008 to 1.181 in) in the case of Gigantocypris. Their bodies are flattened from side to side and protected by a bivalve-like, chitinous or calcareous valve or "shell". The hinge of the two valves is in the upper (dorsal) region of the body. Ostracods are grouped together based on gross morphology. While early work indicated the group may not be monophyletic; and early molecular phylogeny was ambiguous on this front, recent combined analyses of molecular and morphological data found support for monophyly in analyses with broadest taxon sampling 
Ecologically, marine ostracods can be part of the zooplankton or (most commonly) are part of the benthos, living on or inside the upper layer of the sea floor. Many ostracods, especially the Podocopida, are also found in fresh water, and terrestrial species of Mesocypris are known from humid forest soils of South Africa, Australia and New Zealand. They have a wide range of diets, and the group includes carnivores, herbivores, scavengers and filter feeders.
As of 2008, around 2000 species and 200 genera of nonmarine ostracods are found. However, a large portion of diversity is still undescribed, indicated by undocumented diversity hotspots of temporary habitats in Africa and Australia. Of the known specific and generic diversity of nonmarine ostracods, half (1000 species, 100 genera) belongs to one family (of 13 families), Cyprididae. Many Cyprididae occur in temporary water bodies and have drought-resistant eggs, mixed/parthenogenetic reproduction, and the ability to swim. These biological attributes preadapt them to form successful radiations in these habitats.
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Ostracods are "by far the most common arthropods in the fossil record" with fossils being found from the early Ordovician to the present. An outline microfaunal zonal scheme based on both Foraminifera and Ostracoda was compiled by M. B. Hart. Freshwater ostracods have even been found in Baltic amber of Eocene age, having presumably been washed onto trees during floods.
Ostracods have been particularly useful for the biozonation of marine strata on a local or regional scale, and they are invaluable indicators of paleoenvironments because of their widespread occurrence, small size, easily preservable, generally moulted, calcified bivalve carapaces; the valves are a commonly found microfossil.
A find in Queensland, Australia in 2013, announced in May 2014, at the Bicentennary Site in the Riversleigh World Heritage area, revealed both male and female specimens with very well preserved soft tissue. This set the Guinness World Record for the oldest penis. Males had observable sperm that is the oldest yet seen and, when analysed, showed internal structures and has been assessed as being the largest sperm (per body size) of any animal recorded. It was assessed that the fossilisation was achieved within several days, due to phosphorus in the bat droppings of the cave where the ostracods were living.
The body of an ostracod is encased by two valves, superficially resembling the shell of a clam. A distinction is made between the valve (hard parts) and the body with its appendages (soft parts).
The body consists of a head and thorax, separated by a slight constriction. Unlike many other crustaceans, the body is not clearly divided into segments. The abdomen is regressed or absent, whereas the adult gonads are relatively large.
The head is the largest part of the body, and bears most of the appendages. Two pairs of well-developed antennae are used to swim through the water. In addition, there is a pair of mandibles and two pairs of maxillae. The thorax typically has two pairs of appendages, but these are reduced to a single pair, or entirely absent, in many species. The two "rami", or projections, from the tip of the tail, point downwards and slightly forward from the rear of the shell.
Ostracods typically have no gills, instead taking in oxygen through branchial plates on the body surface. Most ostracods have no heart or circulatory system, and blood simply circulates between the valves of the shell. Nitrogenous waste is excreted through glands on the maxillae, antennae, or both.
The primary sense of ostracods is likely touch, as they have several sensitive hairs on their bodies and appendages. However, they do possess a single naupliar eye, and, in some cases, a pair of compound eyes, as well.
A new method is in development called mutual ostracod temperature range (MOTR), similar to the mutual climatic range (MCR) used for beetles, which can be used to infer palaeotemperatures. The ratio of oxygen-18 to oxygen-16 (δ18O) and the ratio of magnesium to calcium (Mg/Ca) in the calcite of ostracod valves can be used to infer information about past hydrological regimes, global ice volume and water temperatures.
Male ostracods have two penii, corresponding to two genital openings (gonopores) on the female. The individual sperm are often large, and are coiled up within the testis prior to mating; in some cases, the uncoiled sperm can be up to six times the length of the male ostracod itself. Mating typically occurs during swarming, with large numbers of females swimming to join the males. Some species are partially or wholly parthenogenetic.
In most ostracods, eggs are either laid directly into the water as plankton, or are attached to vegetation or the substratum. However, in some species, the eggs are brooded inside the shell, giving them a greater degree of protection. The eggs hatch into nauplius larvae, which already have a hard shell.
A variety of fauna prey upon ostracods in both aquatic and terrestrial environments. An example of predation in the marine environment is the action of certain cuspidariid clams in detecting ostracods with cilia protruding from inhalant structures, thence drawing the ostracod prey in by a violent suction action. Predation from higher animals also occurs; for example, amphibians such as the rough-skinned newt prey upon certain ostracods.
Some ostracods, such as Vargula hilgendorfii, have a light organ in which they produce luminescent chemicals. Most use the light as predation defense, while some use the light for mating (only in the Caribbean). These ostracods are called "blue sand" or "blue tears" and glow blue in the dark at night. Their bioluminescent properties made them valuable to the Japanese during World War II, when the Japanese army collected large amounts from the ocean to use as a convenient light for reading maps and other papers at night. The light from these ostracods, called umihotaru in Japanese, was sufficient to read by but not bright enough to give away troops' position to enemies.
Candonidae is a family of ostracods, containing around 25% of all known species of freshwater ostracods. Around 75% of genera in the family are endemic to a single zoogeographic region. It contains more than 500 species, of which more than 300 are endemic to the Palaearctic ecozone.Carbonita (ostracod)
Carbonita is an extinct genus of nonmarine ostracod crustaceans that lived during the Carboniferous period.Cyprididae
Not to be confused with Cyprinidae, a family of fish.
Cyprididae is "the most diverse group of freshwater ostracods". It contains 1000 species, which represents 50% of the known species of freshwater ostracods (other speciose families include Candonidae, with 25%, and Limnocytheridae, with 10%). Around 60% of genera in the family are endemic to a single zoogeographic region. The family contains 25 subfamilies, and is most diverse in the Afrotropic ecozone, with over 300 species in 45 genera. Many Cyprididae occur in temporary water bodies and have drought-resistant eggs, mixed/parthenogenetic reproduction and ability to swim. These biological attributes pre-adapt them to form successful radiations in these habitats. Bennelongia is an interesting genus of the family Cyprididae. It may be the last true descendant genus of the Mesozoic (and now extinct) lineage of Cypridea, which was a dominant lineage of ostracod in non-marine waters in the Cretaceous.Cytherellidae
Cytherellidae is a family of ostracods, and is the only living family in the order, Platycopida, although the family Punciidae is also sometimes included. Members of the family have existed since the Jurassic. It contains 6 genera:
Cytherella Jones, 1849
Cytherelloidea Alexander, 1929
Grammcythella Swanson et al., 2005
Inversacytherella Swanson et al., 2005
Keijcyoidea Malz, 1981
Platella Coryell & Fields, 1937Geoarchaeology
Geoarchaeology is a multi-disciplinary approach which uses the techniques and subject matter of geography, geology, geophysics and other Earth sciences to examine topics which inform archaeological knowledge and thought. Geoarchaeologists study the natural physical processes that affect archaeological sites such as geomorphology, the formation of sites through geological processes and the effects on buried sites and artifacts post-deposition. Geoarchaeologists' work frequently involves studying soil and sediments as well as other geographical concepts to contribute an archaeological study. Geoarchaeologists may also use computer cartography, geographic information systems (GIS) and digital elevation models (DEM) in combination with disciplines from human and social sciences and earth sciences. Geoarchaeology is important to society because it informs archaeologists about the geomorphology of the soil, sediments and the rocks on the buried sites and artifacts they're researching on. By doing this we are able to locate ancient cities and artifacts and estimate by the quality of soil how "prehistoric" they really are.Greylake
Greylake (grid reference ST384336) is a 9.3 hectare geological Site of Special Scientific Interest near Middlezoy in Somerset, notified in 1987.
This site, on the Somerset Levels, consists of 20 low-lying fields in the north west corner of King's Sedgemoor, and includes the Royal Society for the Protection of Birds Greylake nature reserve which has taken over arable farmland and is now home to lapwings, snipe, curlews, redshanks, yellow wagtails, skylarks and meadow pipits.This location is the type section for the Pleistocene Burtle Beds, as it is probably the most complete Burtle Beds
sequence in Somerset. It demonstrates a sequence of fluvial (or possibly glacial) gravels, marine intertidal silts and marine subtidal. Rich molluscan, ostracod and foraminifera assemblages and a mammalian fauna, including red deer (Cervus elephus), aurochs (Bos primigenius) and fallow deer (Dama dama) have been recorded.Greylake was flooded during the winter flooding of 2013–14 on the Somerset Levels.Kilmaluag Formation
The Kilmaluag Formation is a Middle Jurassic geologic formation in Scotland. It was formerly known as the Ostracod Limestone for the abundance of fossil freshwater ostracods within it. The Kilmaluag Formation is very fossiliferous, with ostracods, gastropods, bivalves and vertebrate fossil remains. Vertebrate fossils include fish, crocodiles, mammals, lizards and some large reptile remains including dinosaurs.
The Kilmaluag Formation is Bathonian,and dates to around 167 million years old. It is part of the Great Estuarine Group of the Hebrides Basin, a series of sediments laid down when the Scottish Hebrides was part of a warm shallow sea running between what is now mainland Scotland the Outer Hebrides.The Kilmaluag Formation is composed of dolomitised limestones, fine grain sandstones, and mudstones, indicating that it alternated between a shallow environment, and lagoonal mudflats as the basin subsided and rose, causing sea levels to fluctuate. These mudflats sometimes dried out to form desiccation cracks. The Kilmaluag Formation is unusual among the Estuarine Group for the freshwater environment it preserves, whereas many other formations in this group are predominantly brackish to marine in nature. In many beds, freshwater gastropods and bivalves can be found, including Viviparus and Unio, and freshwater ostracods such as Darwinula.Many vertebrate fossils are found in the Kilmaluag Formation, and it has been explored by palaeontologists since the 1970s, when the first mammal fossil was found there by Michael Waldman. He returned with fellow palaeontologist Robert Savage and they collected more fossils and named two new species from the area: the Docodont Borealestes serendipitus, and the tritylodontid,
Stereognathus hebridicus (although S. hebridicus is now thought to be a junior synonym to S. ooliticus). Many other fossils are found in the Kilmaluag, including members of other Mesozoic mammal groups, turtles, reptiles, and amphibians. The most recent discoveries in the Kilmaluag Formation include Palaeoxonodon ooliticus and Wareolestes rex. and the tooth of a sauropod dinosaur.Limnocytheridae
Limnocytheridae is a family of ostracods, containing the following genera:
Cytheridella Daday, 1905
Gomphocythere Sars, 1924
Leptocytheromorpha Purper, 1979†
Limnocythere Brady, 1968
Minicythere Ornellas, 1974List of prehistoric ostracod genera
This list of prehistoric ostracods is an attempt to create a comprehensive listing of all genera from the fossil record that have ever been considered to be members of the Ostracoda, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomina dubia), or were not formally published (nomina nuda), as well as junior synonyms of more established names, and genera that are no longer considered ostracods.Mannville Group
The Mannville Group is a stratigraphical unit of Cretaceous age in the Western Canadian Sedimentary Basin.
It takes the name from the town of Mannville, Alberta, and was first described in the Northwest Mannville 1 well by A.W. Nauss in 1945.Marjorie Mestayer
Marjorie Katherine Mestayer (1880 – 7 September 1955) was a New Zealand curator and conchologist. She is best known for the molluscan, foraminiferal and ostracod species named after her. Beginning as an amateur shell enthusiast, she went on to work as a conchology curator for the Dominion Museum in Wellington. She also received grants for her conchology research. She donated scientific and personal collections to the Museum of New Zealand Te Papa Tongarewa.Muellerina (ostracod)
Muellerina is a Cenozoic genus of ostracods in the family Hemicytheridae. The name is a tribute to German zoologist specializing in ostracod biology Christian Gustav Wilhelm Müller (1857-1940).Pauline (ostracod)
Pauline is a fossil genus of ostracods from the Silurian. Genus contains two species: Pauline avibella found in 425-million-year-old rocks in the Herefordshire Lagerstätte in England near the Welsh Border and Pauline nivisis, known from the Lower Silurian (upper Telychian) Pentamerus Bjerge Formation of north Greenland.Quasillites
Quasillites is a fossil genus of ostracod from the Devonian and Carboniferous Periods.Spelaeoecia
Spelaeoecia is a genus of crustaceans in the family Thaumatocyprididae. One species, the Bermudan endemic S. bermudensis, is listed as critically endangered on the IUCN Red List. It contains the following species:
Spelaeoecia barri Kornicker in Kornicker & Barr, 1997
Spelaeoecia bermudensis Angel & Iliffe, 1987
Spelaeoecia capax Kornicker in Kornicker, Yager & Williams, 1990
Spelaeoecia cubensis Kornicker & Yager, 1996
Spelaeoecia hox Kornicker, Iliffe & Harrison-Nelson, 2007
Spelaeoecia jamaicensis Kornicker & Iliffe, 1992
Spelaeoecia mayan Kornicker & Iliffe, 1998
Spelaeoecia parkeri Kornicker, Iliffe & Harrison-Nelson, 2002
Spelaeoecia sagax Kornicker in Kornicker, Yager & Williams, 1990
Spelaeoecia saturno Kornicker & Yager, 2002
Spelaeoecia styx Kornicker in Kornicker, Yager & Williams, 1990Subfossil
A subfossil is a part of a dead organism that is partially, rather than fully, fossilized, as is a fossil. Partial fossilization may be present because not enough time has elapsed since the animal died for full fossilization, or because the conditions in which the remains were deposited were not optimal for fossilization.
For remains such as molluscan seashells, which frequently do not change their chemical composition over geological time, and may occasionally even retain such features as the original color markings for millions of years, the label "subfossil" is applied to shells that are understood to be thousands of years old, but are of Holocene age, and therefore are not old enough to be from the Pleistocene epoch.
Unfossilized or partially fossilized remains can include bones, exoskeletons, nests, skin imprints, or fecal deposits. Subfossils of vertebrates are often found in caves or other shelters, where the remains have been preserved for thousands of years. The main importance of these vertebrate subfossil (versus fully fossilized) remains is that they contain organic material, which can be used for radiocarbon dating or the extraction and sequencing of DNA, protein, or other biomolecules. Additionally, isotope ratios can provide information about the ecological conditions under which extinct animals lived. Subfossils are useful for studying the evolutionary history of an environment and can be important to studies in paleoclimatology.
Subfossils are also often found in depositionary environments, such as lake sediments, oceanic sediments, and soils. Once deposited, physical and chemical weathering may alter the state of preservation, and small subfossils can also be ingested by living organisms. Subfossil remains that date from the Mesozoic are exceptionally rare, are usually in an advanced state of decay, and are consequently much disputed. The vast bulk of subfossil material comes from Quaternary sediments, including many subfossilized chironomid head capsules, ostracod carapaces, diatoms, and foraminifera.Vargula hilgendorfii
Vargula hilgendorfii, sometimes called the sea-firefly and one of three bioluminescent species known in Japan as umi-hotaru (海蛍), is a species of ostracod crustacean. It is the only member of genus Vargula to inhabit Japanese waters; all other members of its genus inhabit the Gulf of Mexico, the Caribbean Sea, and waters off the coast of California. V. hilgendorfii was formerly more common, but its numbers have fallen significantly.
Extant Arthropoda classes by subphylum