1.
Precambrian
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The Precambrian is the earliest period of Earths history, set before the current Phanerozoic Eon. The Precambrian is a supereon that is subdivided into three eons of the time scale. It spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, the Precambrian accounts for 89% of geologic time. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earths history, the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, and fossils from that time are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion. A stable crust was apparently in place by 4,412 Ma, the term Precambrian is recognized by the International Commission on Stratigraphy as a general term including the Archean and Proterozoic eons. It is still used by geologists and paleontologists for general discussions not requiring the more specific eon names and it was briefly called the Cryptozoic eon. A specific date for the origin of life has not been determined, carbon found in 3.8 billion year old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have found in Western Australia. Probable fossils 100 million years older have been found in the same area, there is a fairly solid record of bacterial life throughout the remainder of the Precambrian. The oldest fossil evidence from that era of such complex life comes from the Lantian formation of the Ediacarian period, a very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota, hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic era. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale. The explosion in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life, while land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Evidence of the details of plate motions and other activity in the Precambrian has been poorly preserved. It is generally believed that small proto-continents existed prior to 4280 Ma, the supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch, one of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a Snowball Earth. The atmosphere of the early Earth is not well understood, most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and was lacking in free oxygen
2.
Cambrian
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The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya and its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, as a result, our understanding of the Cambrian biology surpasses that of some later periods. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia, the seas were relatively warm, and polar ice was absent for much of the period. The United States Federal Geographic Data Committee uses a barred capital C ⟨Є⟩ character similar to the capital letter Ukrainian Ye ⟨Є⟩ to represent the Cambrian Period, the proper Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH BAR. Despite the long recognition of its distinction from younger Ordovician Period rocks and older Supereon Precambrian rocks, the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. Pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA, the stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain. The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period, the Cambrian is divided into four epochs and ten ages. Currently only two series and five stages are named and have a GSSP, because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian, Middle Cambrian and Furongian, rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian, each of the local epochs is divided into several stages. The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago, the lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites. The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier and this formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago quickly gained favour, though the used to obtain this number are now considered to be unsuitable. A more precise date using modern radiometric dating yield a date of 541 ±0.3 million years ago, most continental land was clustered in the Southern Hemisphere at this time, but was drifting north. Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian, the sea levels fluctuated somewhat, suggesting there were ice ages, associated with pulses of expansion and contraction of a south polar ice cap. In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into a epicontinental sea, the Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents
3.
Ordovician
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The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Mya. Lapworth recognized that the fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods. It received international sanction in 1960, when it was adopted as a period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, invertebrates, namely molluscs and arthropods, dominated the oceans. The Great Ordovician Biodiversification Event considerably increased the diversity of life, fish, the worlds first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land, about 100 times as many meteorites struck the Earth during the Ordovician compared with today. The Ordovician Period began with a major extinction called the Cambrian–Ordovician extinction event and it lasted for about 42 million years and ended with the Ordovician–Silurian extinction event, about 443.8 Mya which wiped out 60% of marine genera. The dates given are recent radiometric dates and vary slightly from those found in other sources and this second period of the Paleozoic era created abundant fossils that became major petroleum and gas reservoirs. The boundary chosen for the beginning of both the Ordovician Period and the Tremadocian stage is highly significant and it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species. The base of the Tremadocian allows scientists to relate these species not only to each other and this makes it easier to place many more species in time relative to the beginning of the Ordovician Period. A number of terms have been used to subdivide the Ordovician Period. In 2008, the ICS erected an international system of subdivisions. There exist Baltoscandic, British, Siberian, North American, Australian, the Ordovician Period in Britain was traditionally broken into Early, Middle and Late epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, the Floian corresponds to the lower Arenig, the Arenig continues until the early Darriwilian, subsuming the Dapingian. The Llanvirn occupies the rest of the Darriwilian, and terminates with it at the base of the Late Ordovician. The Sandbian represents the first half of the Caradoc, the Caradoc ends in the mid-Katian, during the Ordovician, the southern continents were collected into Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole, the small continent Avalonia separated from Gondwana and began to move north towards Baltica and Laurentia, opening the Rheic Ocean between Gondwana and Avalonia
4.
Silurian
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The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway
5.
Devonian
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The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, England, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician. The first ammonites, species of molluscs, appeared, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers
6.
Carboniferous
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The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period,298.9 Mya. The name Carboniferous means coal-bearing and derives from the Latin words carbō and ferō, and was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the system names to be employed. The Carboniferous is often treated in North America as two periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial life was established by the Carboniferous period. Amphibians were the dominant land vertebrates, of one branch would eventually evolve into amniotes. Arthropods were also common, and many were much larger than those of today. Vast swaths of forest covered the land, which would eventually be laid down, the atmospheric content of oxygen also reached their highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. A major marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred in the middle of the period, the later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. In the United States the Carboniferous is usually broken into Mississippian and Pennsylvanian subperiods, the Silesian is roughly contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, and the Westphalian as the Coal Measures and Pennant Sandstone. There was also a drop in south polar temperatures, southern Gondwanaland was glaciated throughout the period and these conditions apparently had little effect in the deep tropics, where lush swamps, later to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major extinction, one that hit crinoids. This sea level drop and the unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation, the Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America, in the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, the Late Carboniferous Pangaea was shaped like an O. There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the O in the Carboniferous Pangaea, other minor oceans were shrinking and eventually closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean
7.
Permian
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The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, turtles, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms. During the Permian, all the Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, fungi, arthropods, the period saw a massive desert covering the interior of Pangaea
8.
Triassic
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The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago, to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era, both the start and end of the period are marked by major extinction events. Therapsids and archosaurs were the terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic, the vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, however, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another mass extinction, the Triassic-Jurassic extinction event. The Triassic is usually separated into Early, Middle, and Late Triassic Epochs, from the east, along the equator, the Tethys sea penetrated Pangaea, causing the Paleo-Tethys Ocean to be closed. Later in the mid-Triassic a similar sea penetrated along the equator from the west, the remaining shores were surrounded by the world-ocean known as Panthalassa. All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates, thus, the supercontinent Pangaea was rifting during the Triassic—especially late in that period—but had not yet separated. In North America, for example, marine deposits are limited to a few exposures in the west, thus Triassic stratigraphy is mostly based on organisms that lived in lagoons and hypersaline environments, such as Estheria crustaceans. At the beginning of the Mesozoic Era, Africa was joined with Earths other continents in Pangaea, Africa shared the supercontinents relatively uniform fauna which was dominated by theropods, prosauropods and primitive ornithischians by the close of the Triassic period. Late Triassic fossils are found throughout Africa, but are common in the south than north. The time boundary separating the Permian and Triassic marks the advent of an event with global impact. At Paleorrota geopark, located in Rio Grande do Sul, Brazil, in these formations, one of the earliest dinosaurs, Staurikosaurus, as well as the mammal ancestors Brasilitherium and Brasilodon have been discovered. The Triassic continental interior climate was hot and dry, so that typical deposits are red bed sandstones and evaporites. Pangaeas large size limited the effect of the global ocean, its continental climate was highly seasonal, with very hot summers. The strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons, the best studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event. On land, the vascular plants included the lycophytes, the dominant cycadophytes, ginkgophyta, ferns, horsetails
9.
Jurassic
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The Jurassic is a geologic period and system that spans 56.3 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles, the start of the period is marked by the major Triassic–Jurassic extinction event. The Jurassic is named after the Jura Mountains within the European Alps, by the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, on land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs, other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to a mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, the chronostratigraphic term Jurassic is directly linked to the Jura Mountains. The name Jura is derived from the Celtic root jor, which was Latinised into juria, the Jurassic period is divided into the Early Jurassic, Middle, and Late Jurassic epochs. The Jurassic System, in stratigraphy, is divided into the Lower Jurassic, Middle, the separation of the term Jurassic into three sections goes back to Leopold von Buch. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, the Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation, as in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed. In contrast, the North American Jurassic record is the poorest of the Mesozoic, the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, India, South America, Japan, Australasia. As the Jurassic proceeded, larger and more groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are well represented nor well studied in Africa. Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania, the Late Jurassic life of Tendaguru is very similar to that found in western North Americas Morrison Formation. During the Jurassic period, the primary living in the sea were fish
10.
Cretaceous
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The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
11.
Paleogene
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The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera
12.
Neogene
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The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene, some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. During this period, mammals and birds continued to evolve into modern forms. Early hominids, the ancestors of humans, appeared in Africa near the end of the period, some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the ocean currents from the Pacific to the Atlantic ocean. The global climate cooled considerably over the course of the Neogene, the terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period. The continents in the Neogene were very close to their current positions, the Isthmus of Panama formed, connecting North and South America. The Indian subcontinent continued to collide with Asia, forming the Himalayas, sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America. The global climate became seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the current Ice Age began, marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the part of the period. Mammals and birds continued to be the dominant terrestrial vertebrates, the first hominids, the ancestors of humans, appeared in Africa and spread into Eurasia. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones, grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison. The Neogene traditionally ended at the end of the Pliocene Epoch, just before the definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to also include ongoing geological time in the Neogene, by dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The International Commission on Stratigraphy once proposed that the Quaternary be considered a sub-era of the Neogene, with a date of 2.58 Ma. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs, thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. Digital Atlas of Neogene Life for the Southeastern United States — by San Jose State University via Web Archive
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Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
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Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
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Chordate
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Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland
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Osteichthyes
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Osteichthyes /ˌɒstiːˈɪkθi. iːz/, popularly referred to as the bony fish, is a diverse taxonomic group of fish that have skeletons primarily composed of bone tissue, as opposed to cartilage. The vast majority of fish are members of Osteichthyes, which is a diverse and abundant group consisting of 45 orders. It is the largest class of vertebrates in existence today, the group Osteichthyes is divided into the ray-finned fish and lobe-finned fish. The oldest known fossils of fish are about 420 million years ago. Osteichthyes can be compared to Euteleostomi, in paleontology, the terms are synonymous. However, recently published phylogenetic trees treat the Osteichthyes as a clade, bony fish are characterized by a relatively stable pattern of cranial bones, rooted, medial insertion of mandibular muscle in the lower jaw. The head and pectoral girdles are covered with large dermal bones, the eyeball is supported by a sclerotic ring of four small bones, but this characteristic has been lost or modified in many modern species. The labyrinth in the ear contains large otoliths. The braincase, or neurocranium, is divided into anterior and posterior sections divided by a fissure. Early bony fish had simple lungs which helped them breathe in low-oxygen water, in many bony fish these have evolved into swim bladders, which help the body create a neutral balance between sinking and floating. They do not have fin spines, but instead support the fin with lepidotrichia and they also have an operculum, which helps them breathe without having to swim. Bony fish have no placoid scales, most have smooth and overlapping ganoid, cycloid or ctenoid scales. Traditionally, Osteichthyes is considered a class, recognised on having a swim bladder, under this classification systems, the Osteichthyes are paraphyletic with regard to land vertebrates as the common ancestor of all Osteichthyes includes tetrapods amongst its descendants. The largest subclass, the Actinopterygii are monophyletic, but with the inclusion of the smaller sub-class Sarcopterygii and this has led to an alternative classification, splitting the Osteichthyes into two full classes. Paradoxically, Sarcopterygii is under this scheme monophyletic, as it includes the tetrapods, most bony fish belong to the ray-finned fish. The phylogeny of living bony fishes is shown in the cladogram, for the majority this is their sole or main means of respiration. Lungfish and other species are capable of respiration through lungs or vascularized swim bladders. Other species can respire through their skin, intestines, and/or stomach, Osteichthyes are primitively ectothermic, meaning that their body temperature is dependent on that of the water
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Chondrostei
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Chondrostei are primarily cartilaginous fish showing some degree of ossification. It is thought that the condition is derived, and that the ancestors of this group were bony fish with fully ossified skeletons. Members of this group share with the Elasmobranchii certain features such as the possession of spiracles, a heterocercal tail, nevertheless, the fossil record suggests they have more in common with the teleosts. The Chondrostei is probably a paraphyletic grouping, the living species are divided among two orders, the Acipenseriformes, and the Polypteriformes. The main distinguishing feature of this group is the nature of the skeleton. Elderly chondrostean individuals show beginnings of ossification of the skeleton, which suggests this process is delayed rather than wholly lost in these fishes, additional shared features include spiracles and, in sturgeons and paddlefishes, a heterocercal tail. However the fossil record suggests these fish have more characters in common with the Teleostei than their appearance might suggest. Chondrostei is paraphyletic, meaning this subclass does not contain all the descendants of their common ancestor, the name comes from Greek chondros meaning cartilage and osteo meaning bone
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Neopterygii
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Neopterygii are a group of fish. Only a few changes occurred during their evolution from the earlier actinopterygians and they appeared sometime in the Late Permian, before the time of the dinosaurs. The Neopterygii are a successful group of fish, because they can move more rapidly than their ancestors. Their scales and skeletons began to lighten during their evolution, and their jaws became more powerful and efficient
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Cladistia
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Cladistia is a clade of bony fishes that currently consists of few anguilliform remnants of an ancient diversity. Their major synapomorphies are a dorsal fin with independent rays, cladistia is the sister group of Actinopteri
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Class (biology)
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In biological classification, class is, a taxonomic rank. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, as for the other well-known ranks, there is the option of an immediately lower rank, indicated by the prefix sub-, subclass. A taxonomic unit, a taxon, in that rank, in that case the plural is classes The composition of each class is determined by a taxonomist. Often there is no agreement, with different taxonomists taking different positions. There are no rules that a taxonomist needs to follow in describing a class. For example, dogs are assigned to the phylum Chordata, in the class Mammalia. In botany, classes are now rarely discussed, for some clades, a number of alternative classifications are used. In the first edition of his Systema Naturae, carl Linnaeus divided all three of his kingdoms of Nature into classes. The class was considered the highest level of the hierarchy until George Cuviers embranchements. Cladistics List of animal classes Phylogenetics Systematics Taxonomy
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Fish
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A fish is any member of a group of animals that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. They form a group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish, lampreys, and cartilaginous, tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered obsolete or paraphyletic by excluding the tetrapods, because in this manner the term fish is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology. The traditional term pisces is considered a typological, but not a phylogenetic classification, the earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts, fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators, the first fish with jaws appeared in the Silurian period, after which many became formidable marine predators rather than just the prey of arthropods. Fish are abundant in most bodies of water and they can be found in nearly all aquatic environments, from high mountain streams to the abyssal and even hadal depths of the deepest oceans. With 33,100 described species, fish exhibit greater species diversity than any group of vertebrates. Fish are an important resource for humans worldwide, especially as food, commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean. They are also caught by fishers, kept as pets, raised by fishkeepers. Fish have had a role in culture through the ages, serving as deities, religious symbols, fish do not represent a monophyletic group, and therefore the evolution of fish is not studied as a single event. Early fish from the record are represented by a group of small, jawless. Jawless fish lineages are mostly extinct, an extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils, the diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways. The first ancestors of fish may have kept the form into adulthood. Fish are a group, that is, any clade containing all fish also contains the tetrapods
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Sarcopterygii
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The living sarcopterygians are the coelacanths and lungfish, additionally, all tetrapods are sarcopterygians or descendants of them. Early lobe-finned fishes are bony fish with fleshy, lobed, paired fins, the fins of lobe-finned fishes differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. The scales of sarcopterygians are true scaloids, consisting of lamellar bone surrounded by layers of bone, dentine-like cosmine. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs and these fins evolved into the legs of the first tetrapod land vertebrates, amphibians. They also possess two dorsal fins with separate bases, as opposed to the dorsal fin of actinopterygians. The braincase of sarcopterygians primitively has a line, but this is lost in tetrapods. Many early sarcopterygians have a symmetrical tail, all sarcopterygians possess teeth covered with true enamel. Most species of lobe-finned fishes are extinct, the largest known lobe-finned fish was Rhizodus hibberti from the Carboniferous period of Scotland which may have exceeded 7 meters in length. Among the two groups of extant species, the coelacanths and the lungfishes, the largest species is the West Indian Ocean coelacanth, reaching 2 m in length, the largest lungfish is the African lungfish which can reach 2 m in length and weigh up to 50 kg. Taxonomists who subscribe to the approach include the grouping Tetrapoda within this group. The fin-limbs of lobe-finned fishes such as the show a strong similarity to the expected ancestral form of tetrapod limbs. The lobe-finned fishes apparently followed two different lines of development and are separated into two subclasses, the Rhipidistia and the Actinistia. The classification below follows Benton 2004, and uses a synthesis of rank-based Linnaean taxonomy, the earliest fossils of sarcopterygians, found in the uppermost Silurian, closely resembled the acanthodians. In the early–middle Devonian, while the predatory placoderms dominated the seas, in the Early Devonian, the sarcopterygians split into two main lineages — the coelacanths and the rhipidistians. The Rhipidistians, whose ancestors lived in the oceans near the river mouths, left the ocean world. They in turn split into two groups, the lungfish and the tetrapodomorphs. The lungfishs greatest diversity was in the Triassic period, today there are fewer than a dozen genera left, the lungfish evolved the first proto-lungs and proto-limbs, developing the ability to live outside a water environment in the middle Devonian. There are three hypotheses as to how they evolved their stubby fins
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Vertebrate
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Vertebrates /ˈvɜːrtᵻbrᵻts/ comprise all species of animals within the subphylum Vertebrata /-ɑː/. Vertebrates represent the majority of the phylum Chordata, with currently about 66,000 species described. Vertebrates include the fish and the jawed vertebrates, which include the cartilaginous fish. A bony fish known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, reptiles, mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, vertebrates make up less than five percent of all described animal species, the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as Craniata when discussing morphology, molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a group of vertebrates in the common taxon of craniata. The word origin of vertebrate derives from the Latin word vertebratus, the Proto-Indo-European language origins are still unclear. Vertebrate is derived from the vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic body plan, a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it. In all vertebrates, the mouth is found at, or right below, the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon, jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills, the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch, the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their relatives have more than 50 pairs of gills. In amphibians and some primitive fishes, the larvae bear external gills. These are reduced in adulthood, their function taken over by the gills proper in fishes, some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods
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Fresh water
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Fresh water is generally characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and brackish water although it does include mineral-rich waters such as chalybeate springs, the term sweet water has been used to describe fresh water in contrast to salt water. The term fresh water does not have the meaning as potable water. Much of the fresh water and ground water is unsuitable for drinking without some form of purification because of the presence of chemical or biological contaminants. It may also be in contact with the underlying underground water. The majority of water on Earth is in ice caps. The source of almost all water is precipitation from the atmosphere, in the form of mist, rain. Fresh water falling as mist, rain or snow contains materials dissolved from the atmosphere and material from the sea, in some cases this acid rain results in pollution of lakes and rivers. In coastal areas fresh water may contain significant concentrations of salts derived from the sea if windy conditions have lifted drops of seawater into the rain-bearing clouds. This can give rise to elevated concentrations of sodium, chloride, magnesium, significant quantities of iron may be transported in this way including the well-documented transfer of iron-rich rainfall falling in Brazil derived from sand-storms in the Sahara in north Africa. Water is an issue for the survival of all living organisms. Some can use water but many organisms including the great majority of higher plants. Out of all the water on Earth, saline water in oceans, seas and saline groundwater make up about 97% of it. Freshwater lakes contain about 87% of this surface water, including 29% in the African Great Lakes, 20% in Lake Baikal in Russia, 21% in the North American Great Lakes. Swamps have most of the balance only a small amount in rivers. In areas with no water on the ground surface, fresh water derived from precipitation may, because of its lower density. Most of the fresh water is frozen in ice sheets. Many areas suffer from lack of distribution of water, such as deserts
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Ocean
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An ocean is a body of saline water that composes much of a planets hydrosphere. On Earth, an ocean is one of the major divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern, the word sea is often used interchangeably with ocean in American English but, strictly speaking, a sea is a body of saline water partly or fully enclosed by land. The ocean contains 97% of Earths water, and oceanographers have stated that less than 5% of the World Ocean has been explored, the total volume is approximately 1.35 billion cubic kilometers with an average depth of nearly 3,700 meters. As the world ocean is the component of Earths hydrosphere, it is integral to all known life, forms part of the carbon cycle. The world ocean is the habitat of 230,000 known species, but because much of it is unexplored, the origin of Earths oceans remains unknown, oceans are thought to have formed in the Hadean period and may have been the impetus for the emergence of life. Extraterrestrial oceans may be composed of water or other elements and compounds, the only confirmed large stable bodies of extraterrestrial surface liquids are the lakes of Titan, although there is evidence for the existence of oceans elsewhere in the Solar System. Early in their histories, Mars and Venus are theorized to have had large water oceans. The Mars ocean hypothesis suggests that nearly a third of the surface of Mars was once covered by water, compounds such as salts and ammonia dissolved in water lower its freezing point so that water might exist in large quantities in extraterrestrial environments as brine or convecting ice. Unconfirmed oceans are speculated beneath the surface of many planets and natural satellites, notably. The Solar Systems giant planets are thought to have liquid atmospheric layers of yet to be confirmed compositions. Oceans may also exist on exoplanets and exomoons, including surface oceans of water within a circumstellar habitable zone. Ocean planets are a type of planet with a surface completely covered with liquid. The concept of Ōkeanós has an Indo-European connection, Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion, the Okeanos is represented with a dragon-tail on some early Greek vases, though generally described as several separate oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a body of water with relatively free interchange among its parts is of fundamental importance to oceanography. The major oceanic divisions – listed below in descending order of area and volume – are defined in part by the continents, various archipelagos, Oceans are fringed by smaller, adjoining bodies of water such as seas, gulfs, bays, bights, and straits. The Mid-Oceanic Ridge of the World are connected and form the Ocean Ridge, the continuous mountain range is 65,000 km long, and the total length of the oceanic ridge system is 80,000 km long
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Paedocypris
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Paedocypris is a genus of cyprinid fish found in Southeast Asia, where it occurs in Malaysia, and Indonesia. Paedocypris progenetica has been claimed to be the smallest known species of fish in the world, the smallest mature female measured 9.7 mm and the largest known individual 10.3 mm. The three currently recognized species in this genus are, Paedocypris carbunculus Britz & Kottelat,2008 Paedocypris micromegethes Kottelat, Britz, tan & K. E. Witte,2006 Paedocypris progenetica Kottelat, Britz, H. H. Their osteology was studied by Ralf Britz at Londons Natural History Museum, in 1994, the same ichthyologists had already discovered in Sarawak another miniature species of the same genus Paedocypris. Like P. progenetica, P. micromegethes was found in the slow-flowing blackwater streams, the genus, Paedocyrpis, and two species, Paedocypris progenetica and Paedocypris micromegethes, were first described in 2006. Paideios is Greek for children and cypris is Greek for Venus and is a suffix for cyprinid genera. Progenetica is used as an adjective, micromegethes is Greek for small in size, and is used as a noun in apposition. Paedocypris is considered a genus by Tyson Roberts. Males also have a pad of keratinized skin in front of the pelvic fins and these modified fins are thought to be used to grasp the female during mating, or to keep position over a spawning surface. Paedocypris progenetica has been claimed to be the smallest known species of fish and vertebrate in the world, the smallest mature P. progenetica female is only 9.7 mm standard length, smaller than the female of any other vertebrate species, including those of P. amauensis. The largest known individual is 10.3 mm. Male individuals of the anglerfish species Photocorynus spiniceps have been documented to be 6. 2-7.3 mm at maturity, Paedocypris micromegethes lives in the peat swamps of Sarawak. Their small size helps them to extreme droughts, as they can live in small remaining puddles of acid water. Their habitat is threatened by forest fires, logging, and plantations, BBC, Scientists find smallest fish BBC, Is it really the smallest fish after all. Pharyngula, Paedocypris Raffles Museum of Biodiversity Research, National University of Singapore Some records in the fish world
27.
Ocean sunfish
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The ocean sunfish or common mola is the heaviest known bony fish in the world. Adults typically weigh between 247 and 1,000 kg, the species is native to tropical and temperate waters around the globe. It resembles a head with a tail, and its main body is flattened laterally. Sunfish can be as tall as they are long when their dorsal and ventral fins are extended, sunfish live on a diet consisting mainly of jellyfish, but because this diet is nutritionally poor, they consume large amounts to develop and maintain their great bulk. Females of the species can produce more eggs than any known vertebrate. Sunfish fry resemble miniature pufferfish, with large fins, a tail fin. Adult sunfish are vulnerable to few natural predators, but sea lions, killer whales, among humans, sunfish are considered a delicacy in some parts of the world, including Japan, Korea, and Taiwan. In the EU, regulations ban the sale of fish and fishery products derived from the family Molidae, sunfish are frequently caught in gillnets. A member of the order Tetraodontiformes, which includes pufferfish, porcupinefish, and filefish. The ocean sunfish, Mola mola, is the species of the genus. Many of the various names allude to its flattened shape. Its specific name, mola, is Latin for millstone, which the fish resembles because of its color, rough texture. Its common English name, sunfish, refers to the habit of sunbathing at the surface of the water. In German, the fish is known as Schwimmender Kopf. In Polish, it is named samogłów, meaning head alone, the Chinese translation of its academic name is fan-che yu 翻車魚, meaning toppled wheel fish. The ocean sunfish has various superseded binomial synonyms, and was classified in the pufferfish genus. It is now placed in its own genus, Mola, with two species, Mola mola and Mola ramsayi, the ocean sunfish, Mola mola, is the type species of the genus. The genus Mola belongs to the family Molidae and this family comprises three genera, Masturus, Mola and Ranzania
28.
Oarfish
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Oarfish are large, greatly elongated, pelagic lampriform fish belonging to the small family Regalecidae. Found in all temperate to tropical oceans yet rarely seen, the family contains four species in two genera. One of these, the giant oarfish, is the longest bony fish alive and that is not enough to qualify as the longest fish, however, as some of the cartilaginous fish such as the basking shark and whale shark are even longer. The family name Regalecidae is derived from the Latin regalis, meaning royal, the occasional beachings of oarfish after storms, and their habit of lingering at the surface when sick or dying, make oarfish a probable source of many sea serpent tales. The dorsal fin originates from above the eyes and runs the length of the fish. Of the approximately 400 dorsal fin rays, the first 10 to 13 are elongated to varying degrees, forming a trailing crest embellished with reddish spots, the pelvic fins are similarly elongated and adorned, reduced to one to five rays each. The pectoral fins are reduced and situated low on the body. The anal fin is absent and the caudal fin may be reduced or absent, as well. At least one account, from researchers in New Zealand, described the oarfish as giving off electric shocks when touched, like other members of its order, the oarfish has a small yet highly protrusible oblique mouth with no visible teeth. The body is scaleless and the skin is covered with easily abraded, in the streamer fish, the skin is clad with hard tubercles. All species lack gas bladders and the number of gill rakers is variable, Oarfish coloration is also variable, the flanks are commonly covered with irregular bluish to blackish streaks, black dots, and squiggles. These markings quickly fade following death, the giant oarfish is by far the largest member of the family at a published total length of 11 m —with unconfirmed reports of 17 m specimens—and 270 kg in weight. The streamer fish is known to reach 3 m in length, Oarfish have the longest known length of any living species of bony fish. The oarfish is thought to inhabit the epipelagic to mesopelagic ocean layers, a few have been found still barely alive, but usually if one floats to the surface, it dies. At the depths the oarfish live, there are little or no currents and so they build little muscle mass, the members of the family are known to have a worldwide range. However, human encounters with live oarfish are rare, and distribution information is collated from records of oarfish caught or washed ashore, rare encounters with divers and accidental catches have supplied what little is known of oarfish behaviour and ecology. Apparently solitary animals, oarfish may frequent significant depths up to 1,000 m. The photograph was taken by Dr. Leo Smith of the Field Museum, of a found in September 1996 by United States Navy SEAL trainees on the coast of Coronado, California
29.
Cichlid
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Cichlids /ˈsɪklᵻdz/ are fish from the family Cichlidae in the order Perciformes. Cichlids are members of a known as Labroidei, along with the wrasses, damselfishes. This family is large and diverse. At least 1,650 species have been described, making it one of the largest vertebrate families. New species are discovered annually, and many species remain undescribed, the actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000. Cichlids are popular freshwater fish kept in the home aquarium, Cichlids span a wide range of body sizes, from species as small as 2.5 cm in length to much larger species approaching 1 m in length. As a group, cichlids exhibit a diversity of body shapes, ranging from strongly laterally compressed species to species that are cylindrical. Generally, however, cichlids tend to be of size, ovate in shape, and slightly laterally compressed, and generally similar to the North American sunfishes in morphology, behavior. Many cichlids, particularly tilapia, are important food fishes, while others are valued game fish, the family also includes many familiar aquarium fish, including the angelfish, oscars, and discus. Cichlids have the largest number of endangered species among vertebrate families and their diversity in the African Great Lakes is important for the study of speciation in evolution. Many cichlids introduced into waters outside of their range have become nuisances. Cichlids share a key trait, the fusion of the lower pharyngeal bones into a single tooth-bearing structure. Cichlids are efficient and often highly specialized feeders that capture and process a wide variety of food items. This is assumed to be one reason why they are so diverse, Cichlids vary in body shape, ranging from compressed and disc-shaped, to triangular to elongated and cylindrical. A ninth subfamily, Ptychochrominae, was recognized by Sparks. Cichlid taxonomy is still debated, and classification of genera cannot yet be definitively given, a comprehensive system of assigning species to monophyletic genera is still lacking, and there is not complete agreement on what genera should be recognized in this family. As an example of the problems, Kullander placed the African genus Heterochromis phylogenetically within Neotropical cichlids. Other problems center upon the identity of the common ancestor for the Lake Victoria superflock
30.
Dorsal fin
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A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fish, cetaceans, and the ichthyosaurs. Depending on the species, an animal may have one or two of them, wildlife biologists often use the distinctive nicks and wear patterns which develop on the dorsal fins of large cetaceans to identify individuals in the field. The bony or cartilaginous bones that support the base of the fin in fish are called pterygiophores. The main purpose of the fin is to stabilize the animal against rolling. Some species have adapted their dorsal fins to other uses. The sunfish uses the dorsal fin for propulsion, in anglerfish, the anterior of the dorsal fin is modified into a biological equivalent to a fishing pole and a lure known as illicium or esca. Many catfish can lock the leading ray of the fin in an extended position to discourage predation or to wedge themselves into a crevice. Some animals have developed dorsal fins with protective functions, such as spines or venom, for example, both the spiny dogfish and the Port Jackson shark have spines in their dorsal fins which are capable of secreting venom. Like tuna, mackerel and other scombroids, billfish streamline themselves by retracting their fins into a groove in their body when they swim. The shape, size, position and colour of the dorsal fin varies with the type of billfish, for example, the white marlin has a dorsal fin with a curved front edge and is covered with black spots. The huge dorsal fin, or sail, of the sailfish is kept retracted most of the time, sailfish raise them if they want to herd a school of small fish, and also after periods of high activity, presumably to cool down. Fish fin Submarine sail Vertical stabilizer
31.
Fish fin
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Fins are usually the most distinctive features of a fish. Apart from the tail or caudal fin, fish fins have no connection with the spine and are supported only by muscles. Their principal function is to help the fish swim, Fins located in different places on the fish serve different purposes such as moving forward, turning, keeping an upright position or stopping. Most fish use fins when swimming, flying fish use pectoral fins for gliding, for every type of fin, there are a number of fish species in which this particular fin has been lost during evolution. Bony fishes form a group called Osteichthyes. They have skeletons made of bone, and can be contrasted with cartilaginous fishes which have made of cartilage. Bony fishes are divided into ray-finned and lobe-finned fish, most fish are ray-finned, an extremely diverse and abundant group consisting of over 30,000 species. It is the largest class of vertebrates in existence today, in the distant past, lobe-finned fish were abundant. Nowadays they are extinct, with only eight living species. Bony fish have fin spines and rays called lepidotrichia and they typically have swim bladders, which allows the fish to create a neutral balance between sinking and floating without having to use its fins. However, these are absent in species, and have developed into primitive lungs in the lungfishes. Bony fishes also have an operculum, which helps them breathe without having to use fins to swim, lobe-finned fishes are a class of bony fishes called Sarcopterygii. They have fleshy, lobed, paired fins, which are joined to the body by a single bone, the fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs and these fins evolved into legs of the first tetrapod land vertebrates, amphibians. They also possess two dorsal fins with separate bases, as opposed to the dorsal fin of ray-finned fish. The coelacanth is another lobe-finned fish which is still extant and it is thought to have evolved into roughly its current form about 408 million years ago, during the early Devonian. Locomotion of the coelacanths is unique to their kind, to move around, coelacanths most commonly take advantage of up or downwellings of the current and drift. They use their fins to stabilize their movement through the water
32.
Lateral line
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The lateral line is a system of sense organs found in aquatic vertebrates, used to detect movement, vibration, and pressure gradients in the surrounding water. Lateral lines serve an important role in schooling behavior, predation, for example, fish can use their lateral line system to follow the vortices produced by fleeing prey. Lateral lines are visible as faint lines of pores running lengthwise down each side. Most amphibian larvae and some fully aquatic adult amphibians possess mechanosensitive systems comparable to the lateral line and this plays an essential role in orientation, predatory behavior, defense, and social schooling. The lateral line system is necessary to detect vibrations made by prey, Fish are able to detect movement, produced either by prey or a vibrating metal sphere, and orient themselves toward the source before proceeding to make a predatory strike at it. This behavior persists even in blinded fish, but is diminished when lateral line function was inhibited by CoCl2 application. Cobalt chloride treatment results in the release of cobalt ions, disrupting ionic transport and these behaviors are dependent specifically on mechanoreceptors located within the canals of the lateral line. The role mechanoreception plays in schooling behavior was demonstrated in a 1976 study, a school of Pollachius virens was established in a tank and individual fish were removed and subjected to different procedures before their ability to rejoin the school was observed. Fish that were experimentally blinded were able to reintegrate into the school, therefore, reliance on functional mechanoreception, not vision, is essential for schooling behavior. A study in 2014 suggests that the lateral line system plays an important role in the behavior of Mexican blind cave fish, the major unit of functionality of the lateral line is the neuromast. The neuromast is an organ which allows the sensing of mechanical changes in water. There are two varieties of neuromasts located in animals, canal neuromasts and superficial or freestanding neuromasts. Superficial neuromasts are located externally on the surface of the body, while canal neuromasts are located along the lines in subdermal. Each neuromast consists of hair cells whose tips are covered by a flexible. Hair cells typically possess both glutamatergic afferent connections and cholinergic efferent connections, the receptive hair cells are modified epithelial cells and typically possess bundles of 40-50 microvilli hairs which function as the mechanoreceptors. These bundles are organized in rough staircases of hairs of increasing length order and this use of mechanosensitive hairs is homologous to the functioning of hair cells in the auditory and vestibular systems, indicating a close link between these systems. Hair cells utilize a system of transduction that uses rate coding in order to transmit the directionality of a stimulus, hair cells of the lateral line system produce a constant, tonic rate of firing. As mechanical motion is transmitted through water to the neuromast, the bends and is displaced
33.
Swim bladder
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Also, the dorsal position of the swim bladder means the center of mass is below the center of volume, allowing it to act as a stabilizing agent. Additionally, the swim bladder functions as a chamber, to produce or receive sound. The swim bladder is evolutionarily homologous to the lungs, charles Darwin remarked upon this in On the Origin of Species. Darwin reasoned that the lung in air-breathing vertebrates had derived from a primitive swim bladder. In the embryonic stages some species, such as blenny, have lost the swim bladder again. Other fish like the Opah and the Pomfret use their fins to swim. The normally bottom dwelling sea robin can use their fins to produce lift while swimming. The gas/tissue interface at the swim bladder produces a reflection of sound. The cartilaginous fish do not have swim bladders, the swim bladder normally consists of two gas-filled sacs located in the dorsal portion of the fish, although in a few primitive species, there is only a single sac. It has flexible walls that contract or expand according to the ambient pressure, the walls of the bladder contain very few blood vessels and are lined with guanine crystals, which make them impermeable to gases. By adjusting the gas pressurising organ using the gas gland or oval window the fish can obtain neutral buoyancy, due to the dorsal position it gives the fish lateral stability. In physostomous swim bladders, a connection is retained between the bladder and the gut, the pneumatic duct, allowing the fish to fill up the swim bladder by gulping air. Excess gas can be removed in a similar manner, in more derived varieties of fish the connection to the digestive tract is lost. In order to introduce gas into the bladder, the gas gland excretes lactic acid, the resulting acidity causes the hemoglobin of the blood to lose its oxygen which then diffuses partly into the swim bladder. Thus a very high gas pressure of oxygen can be obtained, elsewhere, at a similar structure known as the oval window, the bladder is in contact with blood and the oxygen can diffuse back out again. Together with oxygen, other gases are salted out in the bladder which accounts for the high pressures of other gases as well. The combination of gases in the bladder varies, in shallow water fish, the ratios closely approximate that of the atmosphere, while deep sea fish tend to have higher percentages of oxygen. For instance, the eel Synaphobranchus has been observed to have 75. 1% oxygen,20. 5% nitrogen,3. 1% carbon dioxide, physoclist swim bladders have one important disadvantage, they prohibit fast rising, as the bladder would burst
34.
Weberian apparatus
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The Weberian apparatus is an anatomical structure that connects the swim bladder to the auditory system in fishes belonging to the superorder Ostariophysi. When it is developed in adult fish, the elements of the apparatus are sometimes collectively referred to as the Weberian ossicles. The presence of the structure is one of the most important, the structure itself consists of a set of minute bones that originate from the first few vertebrae to develop in an embryonic ostariophysan. These bones grow to physically connect the system, specifically the inner ear. The structure acts as an amplifier of sound waves that would otherwise be only slightly perceivable by the ear structure alone. The entire structure is derived from elements of the first four vertebrae. In addition, a composed of fused neural spines form the dorsalmost part of the Weberian apparatus. Together, the structure interacts anteriorly with the lagenar otolith set within the skull, postero-ventrally, it is the tripus, the os suspensorium and the third rib that interact directly with the anterior chamber of the swim bladder. The Weberian apparatus functions by transmitting auditory signals straight from the gas bladder, through the Weberian ossicles, the structure essentially acts as an amplifier of sound waves that would otherwise be only slightly perceivable by the inner ear structure alone. With the added function of the bladder as a resonating chamber. Embryonic analysis of Weberian apparatuses of the taxon Brycon has shed light on the development of the structure itself. The Weberian apparatus elements form from the fully distinguishable first five vertebrae of the individual, the supraneural starts as an element of the skull. The claustra and the scaphia develop from expanded elements of the arch of the first vertebra. From the second vertebra, the intercalarum and the lateral process are reduced. The plural rib of the third vertebra shrinks and moves somewhat ventrally, the os suspensorium bone of the fourth vertebra somewhat retains its shape, developing from the pleural rib of the vertebra. The remaining elements of the vertebra, the parapophysis and the articulating rib. The neural spines of the first four vertebrae fuse and compress, specific studies have been done on the Weberian apparatuses of a few select taxa, including Danio rerio, Rhaphiodon vulpinus and Corydoras paleatus. The earliest recorded incidence of a Weberian apparatus is from the fossil fish Santanichthys diasii dating from the Early Cretaceous of Northeastern Brazil
35.
Gill
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A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide. The gills of species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a surface area to the external environment. Many microscopic aquatic animals, and some larger but inactive ones, can absorb oxygen through the entire surface of their bodies. However, more complex or more active aquatic organisms usually require a gill or gills, Gills usually consist of thin filaments of tissue, branches, or slender, tufted processes that have a highly folded surface to increase surface area. A high surface area is crucial to the gas exchange of aquatic organisms, a cubic meter of air contains about 250 grams of oxygen at STP. The concentration of oxygen in water is lower than in air, in fresh water, the dissolved oxygen content is approximately 8 cm3/L compared to that of air which is 210 cm3/L. Water is 777 times more dense than air and is 100 times more viscous, oxygen has a diffusion rate in air 10,000 times greater than in water. The use of sac-like lungs to remove oxygen from water would not be efficient enough to sustain life, rather than using lungs, aseous exchange takes place across the surface of highly vascularised gills over which a one-way current of water is kept flowing by a specialised pumping mechanism. The density of the water prevents the gills from collapsing and lying on top of each other, with the exception of some aquatic insects, the filaments and lamellae contain blood or coelomic fluid, from which gases are exchanged through the thin walls. The blood carries oxygen to other parts of the body, carbon dioxide passes from the blood through the thin gill tissue into the water. Gills or gill-like organs, located in different parts of the body, are found in groups of aquatic animals, including mollusks, crustaceans, insects, fish. The gills of vertebrates typically develop in the walls of the pharynx, most species employ a countercurrent exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other. The gills are composed of filaments, the gill lamellae. When a fish breathes, it draws in a mouthful of water at regular intervals, then it draws the sides of its throat together, forcing the water through the gill openings, so it passes over the gills to the outside. Fish gill slits may be the ancestors of the tonsils, thymus glands. Adjacent slits are separated by a gill arch from which projects a cartilaginous gill ray. This gill ray is the support for the sheet-like interbranchial septum, the base of the arch may also support gill rakers, projections into the pharyngeal cavity that help to prevent large pieces of debris from damaging the delicate gills
36.
Barbel (anatomy)
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A barbel on a fish is a slender, whiskerlike sensory organ near the mouth. Fish that have include the catfish, the carp, the goatfish, hagfish, sturgeon. Barbels house the taste buds of such fish and are used to search for food in murky water, Barbels are often erroneously referred to as barbs, which are found in bird feathers for flight. Barbels may be located in a variety of locations on the head of a fish, maxillary barbels refers to barbels on either side of the mouth. Barbels may also be nasal, extending from the nostrils, also, barbels are often mandibular or mental, being located on the chin. Adriaens, D. and Verraes, W. Ontogeny of the maxillary barbel muscles in Clarias gariepinus, eakin, R. R. Eastman, J. T. and Vacchi, M. Sexual dimorphism and mental barbel structure in the South Georgia plunderfish Artedidraco mirus. Pourkazemi, M. Tavakoli, M. Joushideh, H. Khoshghalb, hosseini, M. R. and Abdulhay, H. Tagging and tracking juvenile sturgeons in shallow waters of the Caspian Sea using CWT and barbel incision. Journal of Applied Ichthyology 22, 160-165, fox, H. Barbels and barbel-like tentacular structures in sub-mammalian vertebrates, A review. Fine structure of taste buds in the barbel of the catfish, joyce, E. C. and Chapman, G. B. Fine structure of the nasal barbel of the catfish, Ictalurus punctatus. Leclair, E. and Topczewski, J. Methods for the study of the maxillary barbel. LeClair, E. and Topczewski, J. Development and regeneration of the maxillary barbel. Ogawa, K. Marui, T. and Caprio, J. Bimodal fibers innervate the maxillary barbel in the channel catfish
37.
Tuna
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A tuna is a saltwater fish that belongs to the tribe Thunnini, a sub-grouping of the mackerel family – which together with the tunas, also includes the bonitos, mackerels, and Spanish mackerels. Thunnini comprises fifteen species across five genera, the sizes of which vary greatly, the bluefin averages 2 m, and is believed to live for up to 50 years. Tuna and mackerel sharks are the species of fish that can maintain a body temperature higher than that of the surrounding water. An active and agile predator, the tuna has a sleek, streamlined body, found in warm seas, it is extensively fished commercially, and is popular as a game fish. As a result of over-fishing, stocks of tuna species such as the southern bluefin tuna have been reduced dangerously close to the point of extinction. The term tuna ultimately derives from Thunnus, the Middle Latin form of the Ancient Greek, θύννος tunny-fish – which is in turn derived from θύνω, rush, the following cladogram illustrates the relationship between the tunas and other tribes of the family Scombridae. The true tunas are those that belong to the genus Thunnus, until recently, it was thought that there were seven Thunnus species, and that Atlantic bluefin tuna and Pacific bluefin tuna were subspecies of a single species. In 1999, Collette established that based on molecular and morphological considerations, they are in fact distinct species. The genus Thunnus is further classified into two subgenera, Thunnus, and Thunnus, the Thunnini tribe also includes seven additional species of tuna across four genera. They are, The tuna is a sleek and streamlined fish and it has two closely spaced dorsal fins on its back, The first is depressible – it can be laid down, flush, in a groove that runs along its back. Seven to ten yellow finlets run from the fins to the tail. The caudal peduncle, to which the tail is attached, is quite thin, the tunas dorsal side is generally a metallic dark blue, while the ventral side, or underside, is silvery or whitish, for camouflage. Thunnus are widely but sparsely distributed throughout the oceans of the world, generally in tropical, all tunas are able to maintain the temperature of certain parts of their body above the temperature of ambient seawater. For example, bluefin can maintain a body temperature of 25–33 °C. However, unlike typical endothermic creatures such as mammals and birds, tunas achieve endothermy by conserving the heat generated through normal metabolism. In all tunas, the heart operates at ambient temperature, as it receives cooled blood, also unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red myotomal muscles derive their color from myoglobin, an oxygen-binding molecule, the oxygen-rich blood further enables energy delivery to their muscles. For powerful swimming animals like dolphins and tuna, cavitation may be detrimental, even if they have the power to swim faster, dolphins may have to restrict their speed, because collapsing cavitation bubbles on their tail are too painful
38.
Swordfish
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Swordfish, also known as broadbills in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood and these fish are found widely in tropical and temperate parts of the Atlantic, Pacific, and Indian Oceans, and can typically be found from near the surface to a depth of 550 m. They commonly reach 3 m in length, and the maximum reported is 4.55 m in length and 650 kg in weight and they are the sole member of their family, Xiphiidae. The swordfish is named after its bill, which resembles a sword and this makes it superficially similar to other billfish such as marlin, but upon examination, their physiology is quite different and they are members of different families. They commonly reach 3 m in length, and the maximum reported is 4.55 m in length and 650 kg in weight, the International Game Fish Associations all-tackle angling record for a swordfish was a 1,182 lb specimen taken off Chile in 1953. Females are larger than males, and Pacific swordfish reach a greater size than northwest Atlantic and they reach maturity at 4–5 years of age and the maximum age is believed to be at least 9 years. The oldest swordfish found in a recent study were a 16-year-old female, swordfish ages are derived, with difficulty, from annual rings on fin rays rather than otoliths, since their otoliths are small in size. Swordfish are ectothermic animals, however, along some species of sharks, they have special organs next to their eyes to heat their eyes. Temperatures of 10 to 15 °C above the water temperature have been measured. The heating of the eyes greatly improves their vision, and consequently improves their ability to catch prey, of the 25, 000+ fish species, only 22 are known to have a mechanism to conserve heat. These include the swordfish, marlin, tuna, and some sharks, contrary to popular belief, the sword is not used to spear, but instead may be used to slash at its prey to injure the prey animal, to make for an easier catch. Mainly, the swordfish relies on its speed and agility in the water to catch its prey. It is undoubtedly among the fastest fish, but the basis for the frequently quoted speed of 97 km/h is unreliable, swordfish prefer water temperatures between 18 and 22 °C, but have the widest tolerance among billfish, and can be found from 5 to 27 °C. This highly migratory species typically moves towards colder regions to feed during the summer, swordfish feed daily, most often at night, when they rise to surface and near-surface waters in search of smaller fish. During the day, they occur to depths of 550 m and have exceptionally been recorded as deep as 2,878 m. Adults feed on a range of pelagic fish, such as mackerel, barracudinas, silver hake, rockfish, herring, and lanternfishes, but they also take demersal fish, squid. Large prey are typically slashed with the sword, while small are swallowed whole and they swim alone or in very loose aggregations, separated by as much as 10 m from a neighboring swordfish
39.
Salmon
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Salmon /ˈsæmən/ is the common name for several species of ray-finned fish in the family Salmonidae. Other fish in the family include trout, char, grayling. Salmon are native to tributaries of the North Atlantic and Pacific Ocean, many species of salmon have been introduced into non-native environments such as the Great Lakes of North America and Patagonia in South America. Salmon are intensively farmed in parts of the world. Typically, salmon are anadromous, they are born in water, migrate to the ocean. However, populations of species are restricted to fresh water through their lives. Various species of salmon display anadromous life strategies while others display freshwater resident life strategies, folklore has it that the fish return to the exact spot where they were born to spawn, tracking studies have shown this to be mostly true. A portion of a salmon run may stray and spawn in different freshwater systems. The percent of straying depends on the species of salmon, homing behavior has been shown to depend on olfactory memory. The term salmon comes from the Latin salmo, which in turn may have originated from salire, the nine commercially important species of salmon occur in two genera. The genus Salmo contains the Atlantic salmon, found in the north Atlantic, the genus Oncorhynchus contains eight species which occur naturally only in the North Pacific. As a group, these are known as Pacific salmon, Chinook salmon have been introduced in New Zealand and Patagonia. Coho, freshwater sockeye, and Atlantic salmon have established in Patagonia. † Both the Salmo and Oncorhynchus genera also contain a number of species referred to as trout, within Salmo, additional minor taxa have been called salmon in English, i. e. the Adriatic salmon and Black Sea salmon. The steelhead anadromous form of the rainbow trout migrates to sea, also a number of other species have common names which refer to them as being salmon. The British Columbia salmon fossil provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago, Both the fossil record and analysis of mitochondrial DNA suggest the divergence occurred by 10 to 20 million years ago. This independent evidence from DNA analysis and the fossil record rejects the theory of salmon divergence. Atlantic salmon reproduce in northern rivers on both coasts of the Atlantic Ocean, landlocked salmon live in a number of lakes in eastern North America and in Northern Europe, for instance in lakes Sebago, Onega, Ladoga, Saimaa, Vänern, and Winnipesaukee
40.
Cod
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Cod is the common name for the genus Gadus of demersal fishes, belonging to the family Gadidae. Cod is also used as part of the name for a number of other fish species. Gadus morhua was named by Linnaeus in 1758, Cod is popular as a food with a mild flavour and a dense, flaky, white flesh. Cod livers are processed to make cod liver oil, an important source of vitamin A, vitamin D, vitamin E, young Atlantic cod or haddock prepared in strips for cooking is called scrod. In the United Kingdom, Atlantic cod is one of the most common ingredients in fish and chips, along with haddock, at various times in the past, taxonomists included many species in the genus Gadus. Most of these are now classified in other genera, or have been recognized as simply forms of one of three species. All these species have a number of names, most of them ending with the word cod, whereas other species. However, many other, unrelated species also have names ending with cod. The usage often changes with different localities and at different times, three species in the Gadus genus are currently called cod, Cod forms part of the common name of many other fish no longer classified in the genus Gadus. The tadpole cod family has now placed in Gadidae. Gadiformes include, Some fish have common names derived from cod, such as codling, Some fish commonly known as cod are unrelated to Gadus. Part of this confusion is market-driven. Severely shrunken Atlantic cod stocks have led to the marketing of cod replacements using culinary names of the form x cod, the common names for the following species have become well established, note that all inhabit the Southern Hemisphere. Most are better known as groupers, and belong to the family Serranidae, Some fish that do not have cod in their names are sometimes sold as cod. Haddock and whiting belong to the family, the Gadidae. Haddock Melanogrammus aeglefinus Whiting Merlangius merlangus Cods of the genus Gadus have three rounded dorsal and two anal fins, the pelvic fins are small, with the first ray extended, and are set under the gill cover, in front of the pectoral fins. The upper jaw extends over the jaw, which has a well-developed chin barbel. The eyes are medium-sized, approximately the same as the length of the chin barbel, Cod have a distinct white lateral line running from the gill slit above the pectoral fin, to the base of the caudal or tail fin
41.
Catfish
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Catfish are a diverse group of ray-finned fish. There are armour-plated types and there are also naked types, neither having scales, despite their name, not all catfish have prominent barbel. Members of the Siluriformes order are defined by features of the skull, Catfish are of considerable commercial importance, many of the larger species are farmed or fished for food. Many of the species, particularly the genus Corydoras, are important in the aquarium hobby. Many catfish are nocturnal, but others are crepuscular or diurnal, extant catfish species live inland or in coastal waters of every continent except Antarctica. Catfish have inhabited all continents at one time or another, Catfish are most diverse in tropical South America, Asia and Africa with one family native to North America and one family in Europe. More than half of all species live in the Americas. They are the only ostariophysans that have entered freshwater habitats in Madagascar, Australia and they are found in freshwater environments, though most inhabit shallow, running water. Representatives of at least eight families are hypogean with three families that are also troglobitic, one such species is Phreatobius cisternarum, known to live underground in phreatic habitats. Numerous species from the families Ariidae and Plotosidae, and a few species from among the Aspredinidae and Bagridae, are found in salt water. In the United States, catfish species may be known by a variety of names, such as mud cat, polliwogs. These nicknames are not standardized, so one area may call a bullhead catfish by the nickname chucklehead, while in state or region. Representatives of the genus Ictalurus have been introduced into European waters in the hope of obtaining a sporting, however, the European stock of American catfishes has not achieved the dimensions of these fish in their native waters, and have only increased the ecological pressure on native European fauna. Walking catfish have also introduced in the freshwaters of Florida. Flathead catfish, Pylodictis olivaris, is also a North American pest on Atlantic slope drainages, pterygoplichthys species, released by aquarium fishkeepers, have also established feral populations in many warm waters around the world. In general, they are buoyant, which means that they will usually sink rather than float due to a reduced gas bladder. Catfish have a variety of shapes, though most have a cylindrical body with a flattened ventrum to allow for benthic feeding. A flattened head allows for digging through the substrate as well as serving as a hydrofoil
42.
Flatfish
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A flatfish is a member of the order Pleuronectiformes of ray-finned demersal fishes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both lie on one side of the head, one or the other migrating through. Some species face their left sides upward, some face their right sides upward, many important food fish are in this order, including the flounders, soles, turbot, plaice, and halibut. Some flatfish can camouflage themselves on the ocean floor. Over 700 species are in the 11 families, the largest families are Bothidae, Cynoglossidae, Paralichthyidae, Pleuronectidae, and Soleidae, with more than 100 species each. Some families are the results of relatively recent splits, for example, the Achiridae were classified as a subfamily of Soleidae in the past, and the Samaridae were considered a subfamily of the Pleuronectidae. The Pleuronectidae may be split further still, as some authorities elevate Paralichthodinae, Poecilopsettinae, the taxonomy of some groups is in need of a review, as the last monograph covering the entire order was John Roxborough Normans Monograph of the Flatfishes published in 1934. New species are described with some regularity and undescribed species likely remain, hybrids are well known in flatfishes. The Pleuronectidae, of fishes, have the largest number of reported hybrids. Two of the most famous intergeneric hybrids are between the European plaice and European flounder in the Baltic Sea, and between the English sole and starry flounder in Puget Sound. The offspring of the species pair is popularly known as the hybrid sole and was initially believed to be a valid species in its own right. Flatfishes are found in worldwide, ranging from the Arctic, through the tropics. Most species are found in depths between 0 and 500 m, but a few have been recorded from depths in excess of 1,500 m, none have been confirmed from the abyssal or hadal zones. Among the deepwater species, Symphurus thermophilus lives in congregating around ponds of sulphur at hydrothermal vents on the seafloor, no other flatfish is known from hydrothermal vents. Many species will enter brackish or fresh water, and a number of soles. The most obvious characteristic of the flatfish is its asymmetry, with both eyes lying on the side of the head in the adult fish. In some families, the eyes are usually on the side of the body. The primitive spiny turbots include equal numbers of right- and left-sided individuals, other distinguishing features of the order are the presence of protrusible eyes, another adaptation to living on the seabed, and the extension of the dorsal fin onto the head
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Sturgeon
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Sturgeon is the common name for the 27 species of fish belonging to the family Acipenseridae. Their evolution dates back to the Triassic some 245 to 208 million years ago, the family is grouped into four genera, Acipenser, Huso, Scaphirhynchus and Pseudoscaphirhynchus. Four species may now be extinct, two closely related species, Polyodon spathula and Psephurus gladius are of the same order, Acipenseriformes, but are in the family Polyodontidae and are not considered to be true sturgeons. Both sturgeons and paddlefish have been referred to as primitive fishes because their morphological characteristics have remained unchanged since the earliest fossil record. Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia, several species can grow quite large, typically ranging 7–12 feet in length. The largest sturgeon on record was a Beluga female captured in the Volga estuary in 1827, most sturgeons are anadromous bottom-feeders which migrate upstream to spawn but spend most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively while others primarily inhabit marine environments near coastal areas and they are particularly vulnerable to overexploitation and other threats, including pollution and habitat fragmentation. Most species of sturgeon are considered to be at risk of extinction, acipenseriform fishes appeared in the fossil record some 245 to 208 million years ago presumably near the end of the Triassic, making them among the most ancient of actinopterygian fishes. True sturgeons appear in the record during the Upper Cretaceous. In that time, sturgeons have undergone remarkably little change, indicating their evolution has been exceptionally slow. Although their evolution has been slow, they are a highly evolved living fossil. They do however still share several characteristics, such as heterocercal tail, reduced squamation, more fin rays than supporting bony elements. A further confounding factor is the ability of sturgeons to produce reproductively viable hybrids. While ray-finned fishes have an evolutionary history culminating in our most familiar fishes, past adaptive radiations have left only a few survivors, like sturgeons. The wide range of the acipenserids and their endangered status have made collection of systematic materials difficult and these factors have led researchers in the past to identify over 40 additional species that were rejected by later scientists. There is an effort to resolve the taxonomic confusion using a continuing synthesis of systematic data. Sturgeons retain several primitive characters among the bony fishes, along with other members of the subclass Chondrostei, they are unique among bony fishes because the skeleton is almost entirely cartilaginous. Notably, however, the skeleton is not a primitive character
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Lanternfish
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Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera and they are aptly named after their conspicuous use of bioluminescence. Sampling via deep trawling indicates lanternfish account for as much as 65% of all deep-sea fish biomass, indeed, lanternfish are among the most widely distributed, populous, and diverse of all vertebrates, playing an important ecological role as prey for larger organisms. In the Southern Ocean, myctophids provide a food resource to krill for predators such as squid. Although plentiful and prolific, currently only a few commercial fisheries exist, limited operations off South Africa, in the sub-Antarctic. The fins are small, with a single high dorsal fin, a forked caudal fin. The anal fin is supported by a plate at its base, and originates under, or slightly behind. The pectoral fins, usually with eight rays, may be large and well-developed to small and degenerate, in some species, such as those of the genus Lampanyctus, the pectorals are greatly elongated. Most lanternfish have a gas bladder, but it degenerates or fills with lipids during the maturation of a few species, in all but one species, Taaningichthys paurolychnus, a number of photophores are present, these are paired and concentrated in ventrolateral rows on the body and head. Some may also possess specialised photophores on the peduncle, in proximity to the eyes. The photophores emit a blue, green, or yellow light. In some species, the pattern varies between males and females and this is true for the luminous caudal patches, with the males being typically above the tail and the females being below the tail. Lantern fish are small fish, ranging from about 2 to 30 cm in length, with most being under 15 cm. In life, shallow-living species are an iridescent blue to green or silver and it is the most populous fish species in the open ocean with a density of approximately one per cubic metre. The lanternfish are thought to do this to avoid predation, after a night spent feeding in the surface layers of the water column, the lanternfish begin to descend back into the lightless depths and are gone by daybreak. Most species remain near the coast, schooling over the continental slope, different species are known to segregate themselves by depth, forming dense, discrete conspecific layers, probably to avoid competition between different species. Due to their gas bladders, these layers are visible on sonar scans and give the impression of a false bottom, great variability in migration patterns occurs within the family. Some deeper-living species may not migrate at all, while others may do so only sporadically, migration patterns may also depend on life stage, sex, latitude, and season
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Fangtooth
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Fangtooths are beryciform fish of the family Anoplogastridae that live in the deep sea. The name is from Greek anoplo meaning unarmed and gaster meaning stomach, with a circumglobal distribution in tropical and cold-temperate waters, the family contains only two very similar species in one genus, with no known close relatives. The head is small with a jaw and appears haggard, riddled with mucous cavities delineated by serrated edges. The eyes are small, set high on the head. The fins are small, simple, and spineless, the scales are embedded in the skin, as compensation for reduced eyes, the lateral line is well-developed and appears as an open groove along the flanks. In adults, the largest two fangs of the jaw are so long, the fangtooths have evolved a pair of opposing sockets on either side of the brain to accommodate the teeth when the mouth is closed. According to BBCs Blue Planet, episode The Deep, the fangtooth has the largest teeth of any fish in the ocean, proportionate to body size and these differences once caused the two life stages to be classed as distinct species, with one in another genus, Caulolepis. The pelagic fangtooths are among the fish, found as far as 5,000 m down. They are more commonly found between 200 and 2,000 m, however, and juveniles apparently stay within the reaches of this range. Fangtooths may form schools or go alone. They are thought to use contact chemoreception to find prey, relying on luck to bump into something edible, the smaller teeth and longer gill rakers of juveniles suggest they feed primarily by filtering zooplankton from the water, while the deeper-living adults target other fish and squid. The fangtooths in turn are preyed upon by other pelagic fish, such as tuna and marlin. Fangtooths have planktonic larvae and are assumed to not be egg guarders, spawning frequency and time are not certain, the juveniles of common fangtooths begin to assume adult form from about 8 cm in length, at which time they begin to descend into deeper water. Onset of maturity is not known, but common fangtooths are known to be mature at 16 cm and they are probably slow-growing, as are most deep-sea fish
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Anglerfish
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Anglerfishes are fish of the teleost order Lophiiformes /ˌlɒfiːəˈfɔːrmiːz/. They are bony fish named for their mode of predation. Some anglerfish are also notable for sexual dimorphism and sexual parasitism of the small male on the much larger female. In these species, males may be several orders of magnitude smaller than females, some are pelagic, while others are benthic, some live in the deep sea, while others on the continental shelf. Pelagic forms are most laterally compressed, whereas the benthic forms are often extremely dorsoventrally compressed, a mitochondrial genome phylogenetic study suggested the anglerfishes diversified in a short period of the early to mid-Cretaceous, between 130 and 100 million years ago. Their length can vary from 20 cm to over 1 m with weights up to 45 kg, fishBase, Nelson, and Pietsch list 18 families, but ITIS lists only 16. The following taxa have been arranged to show their evolutionary relationships, the organ has been hypothesized to serve the obvious purpose of luring prey in dark, deep-sea environments, but also serves to call males attention to the females to facilitate mating. The source of luminescence is symbiotic bacteria that dwell in and around the esca and they depend on the fish to make up the difference. Electron microscopy of these bacteria in some species reveals they are Gram-negative rods that lack capsules, spores and they have double-layered cell walls and mesosomes. A pore connects the esca with the seawater, which enables the removal of bacteria and cellular waste. This, as well as the constant temperature of the bathypelagic zone inhabited by fish, is crucial for the long-term viability of bacterial cultures. In most species, a wide mouth extends all around the circumference of the head. The teeth can be depressed so as to offer no impediment to an object gliding towards the stomach, but prevent its escape from the mouth. The anglerfish is able to both its jaw and its stomach, since its bones are thin and flexible, to enormous size. In 2005, near Monterey, California, at 1474 metres depth, when approached, the fish retreated rapidly, but in 74% of the video footage, it drifted passively, oriented at any angle. When advancing, it swam intermittently at a speed of 0.24 body lengths per second, the lethargic behaviour of this ambush predator is suited to the energy-poor environment of the deep sea. Another in situ observation of three different whipnose anglerfish showed unusual upside-down swimming behavior, fish were observed floating upside-down completely motionless with the illicium hanging down stiffly in a slight arch in front of the fish. The illicium was hanging over small visible burrows and it was suggested this is an effort to entice prey and an example of low-energy opportunistic foraging and predation
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Alfonsino
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The alfonsino, also known as the alfonsin, longfinned beryx, red bream, or imperador, is a species of deepwater berycid fish of the order Beryciformes. It can be found in temperate and subtropical ocean waters nearly worldwide and it is typically associated with deep-sea corals, and schools are known to form over seamounts. Adults are demersal and search for prey along the floor, primarily fish, cephalopods. Like other members of its family, it is remarkably long-lived, with individuals reaching ages of up to 69 years and it can reach sizes of up to 100.0 cm in length and 2.5 kg in weight and is targeted by commercial fisheries. It was renamed B. decadactylus by ichthyologist G. E. Maul in 1990, the etymology of its generic name is unclear, but it likely comes from the Greek name for a fish, but which species it was originally used for remains unknown. It is possible that Beryx originally described a species of parrotfish, the alfonsino has large eyes and a deep, compressed body,1. 9-2.5 times its standard length at the greatest depth. It is a red color dorsally and orange ventrally. The rest of its body is silvery-pink, and the breast is yellow-white in color, fins and the inside of the mouth are bright red. The anal fin is larger than in many fish species. Its bright red color is an adaptation to deepwater surroundings. Although the most common size is 35.0 cm, it can reach lengths of up to 100.0 cm TL, the maximum published weight for an alfonsino is 2.5 kg. Juveniles have heavy head spines, while adults do not, the alfonsino is found worldwide in subtropical and temperate waters, with a latitudinal range extending from 70°N to 48°S. It is found from as far north as Greenland and Iceland south to Brazil in the western Atlantic, in the Indo-Pacific it is found from South Africa east to Japan, Australia, and New Zealand. It has also been reported off the coasts of Argentina and Hawaii and it is likely more common in the western Pacific than records indicate due to lack of fishing in its depth range in the region. With an extensive depth range 110–1,000 m below the surface, by day it stays in deeper water and vertically migrates to shallower waters at night. It is most commonly found 200–400 m deep in waters around 24 °C in temperature, in the eastern Atlantic its depth range is 350–600 m, while in the western Atlantic its depth range is 100–972 m, common depth range 400–600 m. The splendid alfonsino is the far more studied species of Beryx, alfonsinos are benthopelagic and aggregate over deep-ocean seamounts, typically near deep-sea corals. At night, they migrate vertically into shallower waters and their primary food sources are crustaceans, cephalopods, and small fish, with the last being the most abundant prey in its diet
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Giant oarfish
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The giant oarfish is a species of oarfish of the family Regalecidae. It is a species with a worldwide distribution, excluding polar regions. Other common names include Pacific oarfish, king of herrings, ribbonfish, R. glesne is the worlds longest bony fish. Its shape is ribbon-like, narrow laterally, with a fin along its entire length, stubby pectoral fins. Its coloration is silvery with dark markings, and its fins are red and its physical characteristics and its undulating mode of swimming have led to speculation that it might be the source of many sea serpent sightings. R. glesne was first described by Peter Ascanius in 1772, the genus name, Regalecus, signifies belonging to a king, the specific epithet glesne is from Glesnaes, the name of a farm at Glesvær, where the type specimen was found. Its king of herrings nickname may derive from its crownlike appendages and from being sighted near shoals of herring, which fishermen thought were being guided by this fish. Its common name, oarfish, is probably an allusion to the shape of its pelvic fins, the giant oarfish is found worldwide in the upper layers of the open ocean. It is believed to be oceanodromous, following its primary food source and it has been found as far north as 72°N and as far south as 52°S, but is most common in the tropics to middle latitudes. It is thought to inhabit the epipelagic to dimly lit mesopelagic zones. This species is the worlds longest bony fish, reaching a length of 11 m, however. It is commonly measured to 3 m in total length, the maximum recorded weight of a giant oarfish is 270 kg. Its shape is ribbonlike, narrow laterally, with a fin along its entire length from between its eyes to the tip of its tail. The fin rays are soft and may number up to 400 or more, at the head of the fish, the rays are lengthened forming a distinctive red crest. Its pectoral and pelvic fins are nearly adjacent, the pectoral fins are stubby while the pelvic fins are long, single-rayed, and reminiscent of an oar in shape, widening at the tip. Its head is small with the protrusible jaw typical of lampriformes, it has 40 to 58 gill rakers, the organs of the giant oarfish are concentrated toward the head end of the body, possibly enabling it to survive losing large portions of its tail. The liver of R. glesne is orange or red, the result of astaxanthin in its diet. The lateral line begins above and behind the eye then, descending to the third of the body
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