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
13.
Dakosaurus
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Dakosaurus is an extinct genus within the family Metriorhynchidae that lived during the Late Jurassic and Early Cretaceous. It was large, with teeth that were serrated and compressed lateromedially, the genus was established by Friedrich August von Quenstedt in 1856 for an isolated tooth named Geosaurus maximus by Plieninger. Dakosaurus was a carnivore that spent much, if not all, the name Dakosaurus means biter lizard, and is derived from the Greek dakos and σαῦρος -sauros. When isolated Dakosaurus teeth were first discovered in Germany, they were mistaken for belonging to the theropod dinosaur Megalosaurus, in 1856 von Quenstedt made Plieningers Geosaurus maximus teeth a new genus with the name Dakosaurus. He explained the etymology as Greek dakos Biss in 1858 in German and he gave the meaning of Greek dakos more correctly as Beisser in another description in 1859 in which he classified Dakosaurus as a dinosaur. Fossil specimens referrable to Dakosaurus are known from Late Jurassic deposits from England, France, Switzerland, Germany, Poland, Russia, Argentina, teeth referrable to Dakosaurus are known from Europe from the Oxfordian. The type species Dakosaurus maximus, meaning greatest biter lizard, is known from fossil discoveries in Western Europe of the Late Jurassic, Dakosaurus andiniensis, meaning biter lizard from the Andes, was first discovered in 1987 in the Neuquén Basin, a very rich fossil bed in Argentina. However, it was not until 1996 that the binomen Dakosaurus andiniensis was erected and this species has a fossil range from the late Jurassic to early Cretaceous. Dakosaurus nicaeensis, named in 1913 by Ambayrac, was classified as a megalosaurid dinosaur. Buffetaut in 1982 demonstrated that it was in fact a metriorhynchid, closely related to, as the type specimen is poorly preserved it is considered nomen dubium. In 2009, Young and Andrade published a re-description of Geosaurus, examining its relationships, incomplete skull specimens of Dakosaurus have been discovered in Kimmeridgian age rocks from Mexico. Dacosaurus is a misspelling of Dakosaurus, and thus a synonym, recent phylogenetic analysis does not support the monophyly of Dakosaurus, although the species D. maximus and D. andiniensis do constite a natural group. The cladogram below follows a subsequent analysis by Young et al, all currently known species would have been approximately 4 to 5 metres in length, which when compared to living crocodilians, Dakosaurus can be considered large-sized. Its body was streamlined for greater efficiency, which along with its finned tail made it a more efficient swimmer than modern crocodilian species. The incomplete skull specimens from the Mexican species of Dakosaurus preserves the chamber in which the salt glands would have been housed. Unfortunately, there was no evidence of the glands themselves. Dakosaurus maximus is one of several species of metriorhynchids known from the Mörnsheim Formation of Bavaria, alongside three other metriorhynchid species, it has been hypothesised that niche partitioning enabled several species of crocodyliforms to co-exist. Dakosaurus and Geosaurus giganteus would have been top predators of this Formation, the remaining two species and the teleosaurid Steneosaurus would have fed mostly on fish
14.
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
15.
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
17.
Reptile
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Reptiles are tetrapod animals in the class Reptilia, comprising todays turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of amphibians, is called herpetology. Because some reptiles are more related to birds than they are to other reptiles. For this reason, many scientists prefer to consider the birds part of Reptilia as well. Some early examples include the lizard-like Hylonomus and Casineria, in addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the K–Pg extinction wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, as well as species of theropods, crocodyliforms. Modern non-avian reptiles inhabit every continent with the exception of Antarctica, several living subgroups are recognized, Testudines, approximately 400 species, Sphenodontia,1 species, Squamata, over 9,600 species, Crocodilia,25 species, and Aves,10,000 species. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, unlike amphibians, reptiles do not have an aquatic larval stage. As amniotes, reptile eggs are surrounded by membranes for protection and transport, many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. In the 18th century, the reptiles were, from the outset of classification, the terms reptile and amphibian were largely interchangeable, reptile being preferred by the French. Josephus Nicolaus Laurenti was the first to use the term Reptilia for an expanded selection of reptiles. Today, the two groups are commonly treated under the same heading as herptiles. He subsequently proposed the names of Sauropsida and Ichthyopsida for the two groups. In 1866, Haeckel demonstrated that vertebrates could be divided based on their strategies, and that reptiles, birds. The terms Sauropsida and Theropsida were used again in 1916 by E. S, Goodrich to distinguish between lizards, birds, and their relatives on the one hand and mammals and their extinct relatives on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, according to Goodrich, both lineages evolved from an earlier stem group, Protosauria in which he included some animals today considered reptile-like amphibians, as well as early reptiles. Watson observed that the first two groups diverged very early in history, so he divided Goodrichs Protosauria between them. He also reinterpreted Sauropsida and Theropsida to exclude birds and mammals, thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia, Squamata, Rhynchocephalia, Crocodilia, thecodonts, non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropterygians
18.
Thalattosuchia
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Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, the term Thalattosuchia was coined by Fraas in 1901. Various authors considered Thalattosuchia an infraorder or a suborder within Mesosuchia, however, the term Mesosuchia is a paraphyletic group, and as such is no longer used. For consistency, the Thalattosuchia are here placed at suborder rank, since Buffetaut demonstrated the shared characteristics of the early forms of Metriorhynchidae and Teleosauridae, Thalattosuchia has consisted of these two families. Some of the members of Teleosauridae have been discovered in non-marine deposits. The systematics of the genus Pelagosaurus are confused, with differencing topologies placing it as either a teleosaurid, others considered Pelagosaurus to be a basal metriorhynchid. List of thalattosuchian-bearing stratigraphic units List of marine reptiles Fraas, E, die Meer-Krocodilier des oberen Jura unter specieller Berücksichtigung von Dacosaurus und Geosaurus
19.
Metriorhynchidae
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Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period of Europe, North America and South America. The name Metriorhynchidae was coined by the Austrian zoologist Leopold Fitzinger in 1843, the group contains two subfamilies, the Metriorhynchinae and the Geosaurinae. Their forelimbs were small and paddle-like, and unlike living crocodilians and their body shape maximised hydrodynamy, as did having a shark-like tail flukes. Metriorhynchids were the group of archosaurs to become fully adapted to the marine realm. The family has a geographic distribution, with material found in Argentina, Chile, Cuba, England, France, Germany, Italy, Mexico, Poland, Russia. Phylogenetic analyses published during the 2000s cast doubt on the idea that many traditional metriorhynchid genera formed natural groups, Young and Marco Brandalise de Andrade. The monophyly of Metriorhynchus and Teleidosaurus is also unsupported, and the species of genera are pending reclassification. The classification presented by Young and Andrade in 2009 was approved in later studies of the Metriorhynchidae, Metriorhynchidae is a node-based taxon defined in 2009 as the least inclusive clade consisting of Metriorhynchus geoffroyii and Geosaurus giganteus. The cladogram below follows the topology from a 2011 analysis by Andrea Cau and Federico Fanti with clade names from Young et al.2011, the type genus of the family Metriorhynchidae is Metriorhynchus from the Middle to Late Jurassic. Other genera included within this family are Cricosaurus, Geosaurus, though once considered a metriorhynchid, Teleidosaurus has since been found to be slightly more distantly related to these animals within the superfamily Metriorhynchoidea. Within this family, the genus Neustosaurus is considered nomen dubium, the genus Capelliniosuchus was once thought to be a metriorhynchid similar to Dakosaurus. However, Sirotti demonstrated that it is a synonym of Mosasaurus
20.
Richard Lydekker
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Richard Lydekker was an English naturalist, geologist and writer of numerous books on natural history. Richard Lydekker was born at Tavistock Square in London and his father was Gerard Wolfe Lydekker, a barrister-at-law with Dutch ancestry. The family moved to Harpenden Lodge soon after Richards birth, and educated at Trinity College, Cambridge, where he took a first-class in the Natural Science tripos. In 1874 he joined the Geological Survey of India and made studies of the paleontology of northern India. He remained in this post until the death of his father in 1881 and his main work in India was on the Siwalik palaeofauna, it was published in Palaeontologia Indica. He was responsible for the cataloguing of the mammals, reptiles. He named a variety of including the golden-bellied mangabey, as a taxon authority he is named simply as Lydekker. He was influential in the science of biogeography, in 1895 he delineated the biogeographical boundary through Indonesia, known as Lydekkers Line, that separates Wallacea on the west from Australia-New Guinea on the east. It follows the edge of the Sahul Shelf, an area from New Guinea to Australia of shallow water with the Aru Islands on its edge. Along with Wallaces Line and Huxleys Line it indicates the effect of geology on the biogeography of the region. Six days later on 12 February 1913, he wrote again, letters about the first cuckoo became a tradition in the newspaper. He received the Lyell Medal from the Geological Society of London in 1902, catalogue of the Fossil Mammalia in the British Museum,5 vols. A Manual of Palaeontology Phases of Animal Life The Royal Natural History (with W. H. Flower],6 vols, wild life of the World, a descriptive survey of the geographical distribution of animals 3 vols. Harpenden History, The Lydekkers of Harpenden Lodge — 1853-1979 Works of Richard Lydekker at Google Books
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Genus
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A genus is a taxonomic rank used in the biological classification of living and fossil organisms in biology. In the hierarchy of classification, genus comes above species. In binomial nomenclature, the name forms the first part of the binomial species name for each species within the genus. Felis catus and Felis silvestris are two species within the genus Felis, Felis is a genus within the family Felidae. The composition of a genus is determined by a taxonomist, the standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. Moreover, genera should be composed of units of the same kind as other genera. The term comes from the Latin genus, a noun form cognate with gignere, linnaeus popularized its use in his 1753 Species Plantarum, but the French botanist Joseph Pitton de Tournefort is considered the founder of the modern concept of genera. The scientific name of a genus may be called the name or generic epithet. It plays a role in binomial nomenclature, the system of naming organisms. The rules for the names of organisms are laid down in the Nomenclature Codes. The standard way of scientifically describing species and other lower-ranked taxa is by binomial nomenclature, the generic name forms its first half. For example, the gray wolfs binomial name is Canis lupus, with Canis being the name shared by the wolfs close relatives. The specific name is written in lower-case and may be followed by names in zoology or a variety of infraspecific names in botany. Especially with these names, when the generic name is known from context. Because animals are typically only grouped within subspecies, it is written as a trinomen with a third name. Dog breeds, meanwhile, are not scientifically distinguished, there are several divisions of plant species and therefore their infraspecific names generally include contractions explaining the relation. For example, the genus Hibiscus includes hundreds of other species apart from the Rose of Sharon or common garden hibiscus, Rose of Sharon doesnt have subspecies but has cultivars that carry desired traits, such as the bright white H. syriaca Diana. Hawaiian hibiscus, meanwhile, includes several separate species, since not all botanists agree on the divisions or names between species, it is common to specify the source of the name using author abbreviations
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Neptunidraco
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Neptunidraco is an extinct genus of carnivorous marine crocodyliform which lived during the middle Jurassic period in what is now northeastern Italy. It is known from a partial skeleton recovered from the limestone of the Rosso Ammonitico Veronese Formation. This specimen had been referred to an unnamed species of Late Jurassic Metriorhynchus or Geosaurus. Neptunidraco was named by Andrea Cau and Federico Fanti in 2011, the Portomaggiore crocodile is the most complete specimen of an Italian metriorhynchid to date and the oldest known metriorhynchid. Steneosaurus barettoni was referred to Neptunidraco in a 2013 study
23.
Purranisaurus
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Purranisaurus is an extinct genus of marine crocodyliform from the Middle to Late Jurassic period of Chile and Argentina. In the 2000s phylogenetic analysis has shown that Purranisaurus is a distinct metriorhynchid genus, a subsequent study expanded the genus Purranisaurus to include Metriorhynchus casamiquelai and M. westermanni. P. casamiquelai, Middle Jurassic of Chile, P. westermanni, although previously considered a junior synonym of P. casamiquelai, it has been revalidated, P. potens, End Jurassic of Argentina
24.
Torvoneustes
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Torvoneustes is an extinct genus of metriorhynchid mesoeucrocodylian. It is known from a skull and some postcranial remains that have been found from the Kimmeridge Clay of Wiltshire. The skull was first to be found, and was assigned to the species Metriorhynchus superciliosus. Postcranial remains were discovered, and the material was then recognized as belonging to a new species of Dakosaurus. D. carpenteri was later reassigned to the genus Geosaurus in 2008, two years later, it was assigned to its own genus, Torvoneustes. When T. carpenteri was considered a species of Dakosaurus, its long snout and smaller. Because of this, the species was seen as a transitional form between long-snouted, piscivorous metriorhynchids and hypercarnivorous, short-snouted species of Dakosaurus, while Dakosaurus and Geosaurus have ziphodont dentitions with teeth that are laterally compressed, Torvoneustes is unique in having a false-ziphodont dentition. However, it is possible that Dakosaurus and Geosaurus acquired similar dentitions independently. The species was named to honour Simon Carpenter, an amateur geologist from Frome in Somerset, who provided access to the fossil material
25.
Geosaurus
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Geosaurus is an extinct genus of marine crocodyliform within the family Metriorhynchidae, that lived during the Late Jurassic and the Early Cretaceous. Geosaurus was a carnivore that spent much, if not all, where Geosaurus mated, whether on land or at sea, is currently unknown. The name Geosaurus means Mother of Giants lizard, and is derived from the Greek Ge-, the name Geosaurus was established by the French naturalist Georges Cuvier in 1824. Geosaurus was a large, marine reptile of the group Crurotarsi, specifically, it was a marine crocodile, or thalattosuchian. Geosaurus was similar in appearance to the related Dakosaurus with a short skull and curved teeth designed for slashing. Many early depictions of Geosaurus were based on a complete specimen described by Eberhard Fraas. This specimen was found in Germany and dated to the late Jurassic period, G. suevicus had a distinctively long, narrow snout filled with small, pointed teeth very different from skulls belonging to the type species. Further study and a re-description of Geosaurus published in 2009 showed that these long-snouted form actually represent individuals of Cricosaurus, genera considered junior synonyms of Geosaurus include Brachytaenius and Halilimnosaurus. Numerous species had been assigned to this genus since the 19th Century, however, phylogenetic analyses begun in 2005 did not support the monophyly of Geosaurus. Although some traditional species, such as G. suevicus and G. araucanensis formed a natural group, the species included below follow this revised classification, presented by Young and Andrade in 2009. The type species Geosaurus giganteus, meaning giant Earth lizard, is known from Western Europe of the Late Jurassic and it was originally named Lacerta gigantea by von Sömmerring. Geosaurus grandis, first described by Wagner in 1858, was considered a species of Cricosaurus. It is known from a complete skull, Geosaurus lapparenti is known from south-east France and dates to the early Cretaceous period. It was named in honour of French palaeontologist Albert-Félix de Lapparent and it was originally classified as a species of Dakosaurus. A large species of Geosaurus is known only from a tooth from the Nusplingen Plattenkalk of Germany. In 2009, Young and de Andrade published a re-description of Geosaurus, examining its relationships, after performing a phylogenetic analysis of metriorhynchids, they found that many species were grouped in a paraphyletic manner or with the wrong genera. Rhacheosaurus gracilis, another long-snouted species, was also at one time considered a species of Geosaurus, Geosaurus carpenteri, also formerly referred to Dakosaurus, is known from a partial skull. Teeth identical to the teeth of this species are also known from Yorkshire
26.
Plesiosuchus
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Plesiosuchus is an extinct genus of geosaurine metriorhynchid crocodyliform known from the Late Jurassic of Dorset, England and possibly also Spain. It contains a single species, Plesiosuchus manselii, Mansel-Pleydell gave these remains to the British Museum in 1866. Part of the holotype of P. manselii was first described by John Hulke in 1869 and he referred it to Steneosaurus rostro-minor Geoffroy, alongside Dakosaurus maximus and other specimens. Initially, the skull was believed to be pliosaurian, it was the preparator Mr Davies that suggested a crocodylian nature for the skull, in 1870, Hulke described the skull, which is preserved in two sections, the rostrum and the occiput. Hulke suggested that this head and the jaw both belonged to one individual as both the same dimensions and were discovered in close proximity in a reef exposed at low water in Kimmeridge Bay. Some material was destroyed due to pyrite decay while the bone fragment referred to as the upper maxilla has never been figured. Richard Owen erected the genus Plesiosuchus for S. manselii in 1884 as he considered it to be more similar morphologically to extant crocodylians than to Steneosaurus, woodward referred the species to the genus Dakosaurus. Lydekker synonymized P. manselii with Dakosaurus maximus while Fraas regarded the two species to be synonymous or closely related, phylogenetic analyses of Young & Andrade, Cau & Fanti and Young et al. support the hypothesis that the two are separate species of Dakosaurus. The holotype of Plesiosuchus includes, NHMUK PV OR40103, a broken and incomplete skull with a mandible, the incomplete skull includes the snout and the occiput, lacking the occipital condyle, with fragments of the supratemporal arches and isolated right articular. NHMUK PV OR40103a includes the right mandibular ramus, some isolated teeth, a humerus, two further specimens may belong to the holotype, NHMUK PV OR40104 - an occipital condyle, and NHMUK PV OR40105 – carpal and tarsal bones. Both specimens were donated to the University of Toronto through Professor Ramsay Wright in 1900, the holotype of Plesiosuchus represents a large individual.42 m. It was collected from the late Kimmeridgian Lower Kimmeridge Clay Formation of Kimmeridge Bay, the specimen NHMUK PV OR40103b, a short series of cervicodorsal vertebrae preserved in matrix, is also a thalattosuchian due to its possession of several apomorphies of the group. However, it does not belong to the individual as the holotype as the vertebrae are much smaller than those of NHMUK PV OR40103a. It is unclear whether it belongs to Plesiosuchus or another metriorhynchid, NHMUK PV R1089, a mandible and a braincase with part of the supratemporal arches collected from the early Tithonian Upper Kimmeridge Clay Formation, of Kimmeridge is also referred to Plesiosuchus. It was also presented by Mansel-Pleydell in 1866, and as with the holotype, was considered to belong to a pliosaurid plesiosaur. It was originally described by Owen as a specimen to the species Pliosaurus trochanterius. However, Owen never provided evidence for this referral and there were no overlapping elements between NHMUK PV R1089 and the holotype of P. trochanterius, furthermore, both species of Machimosaurus lack the prearticular, which is present in NHMUK PV R1089. Additionally, NHMUK PV R1089 exhibits extreme reduction in dentition that is observed in geosaurine metriorhynchids
27.
Suchodus
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Suchodus is an extinct genus of marine crocodyliform from the Middle to Late Jurassic period of England and France. In the 2000s, phylogenetic analysis has shown that Suchodus is a distinct metriorhynchid genus, valid species are, S. brachyrhynchus, Western Europe of the Middle-Late Jurassic, Metriorhynchus cultridens is a junior synonym. S. durobrivensis, Western Europe of the Middle Jurassic, was originally the type species of the genus Suchodus, but it was regarded as a junior synonym of Metriorhynchus by Andrews,1913
28.
Crocodyliformes
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Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as crocodilians. They are the members of Crocodylomorpha who survived beyond the Early Jurassic. The traditional group Crocodylia was replaced with the name Crocodyliformes, which included many of the families that the new definition left out. Chris Brochu agreed with the assessment that Crocodylia as a name has never had stable contents, Brochu and colleagues rejected this proposal, arguing that the crown definition of Crocodylia is the standard meaning both within and beyond the crocodyliform systematics community. Below is a cladogram based on Fiorelli and Calvo. In 2012, paleontologists Mario Bronzati, Felipe Chinaglia Montefeltro, langer conducted a broad phylogenetic analysis to produce supertrees of Crocodyliformes, including 184 species. The most parsimonious trees were highly resolved, meaning the relationships found in the analysis were highly likely. Below is a tree from the study
29.
Bajocian
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In the geologic timescale, the Bajocian is an age or stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma, the Bajocian age succeeds the Aalenian age and precedes the Bathonian age. The Bajocian stage takes its name from the Latin name of the town of Bayeux, the stage was named and introduced in scientific literature by French palaeontologist Alcide dOrbigny in 1842. The base of the Bajocian stage is defined as the place in the column where fossils of the ammonite genus Hyperlioceras first appear. A global reference profile for the base is located at Murtinheira, the top of the Bajocian is at the first appearance of ammonite species Parkinsonia convergens. The Bajocian is often divided into Lower/Early and Upper/Late subages or substages. M, & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press. Terrains oolitiques ou jurassiques,642 pp. Bertrand, Paris, pavia, G. & Enay, R.1997, Definition of the Aalenian-Bajocian Stage boundary, Episodes,20, pp 16–22. Sepkoski, J.2002, A compendium of fossil marine animal genera, Bulletin of American Paleontology 364, p 560
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Valanginian
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In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ±3.0 Ma and 132.9 ±2.0 Ma, the Valanginian stage succeeds the Berriasian stage of the Lower Cretaceous and precedes the Hauterivian stage of the Lower Cretaceous. The Valanginian was first described and named by Édouard Desor in 1853 and it is named after Valangin, a small town north of Neuchâtel in the Jura Mountains of Switzerland. The base of the Valanginian is at the first appearance of calpionellid species Calpionellites darderi in the stratigraphic column, a global reference section had in 2009 not yet been appointed. The top of the Valanginian is at the first appearance of the ammonite genus Acanthodiscus, the Valanginian is often subdivided in Lower and Upper substages. The Upper substage begins at the first appearance of ammonite species Saynoceras verrucosum, a Geologic Time Scale 2004, Cambridge University Press. GeoWhen Database - Valanginian Mid-Cretaceous timescale and ühttp, //stratigraphy. science. purdue. edu/charts/Timeslices/5_JurCret
31.
Europe
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Europe is a continent that comprises the westernmost part of Eurasia. Europe is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, yet the non-oceanic borders of Europe—a concept dating back to classical antiquity—are arbitrary. Europe covers about 10,180,000 square kilometres, or 2% of the Earths surface, politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a population of about 740 million as of 2015. Further from the sea, seasonal differences are more noticeable than close to the coast, Europe, in particular ancient Greece, was the birthplace of Western civilization. The fall of the Western Roman Empire, during the period, marked the end of ancient history. Renaissance humanism, exploration, art, and science led to the modern era, from the Age of Discovery onwards, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at times the Americas, most of Africa, Oceania. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to economic, cultural, and social change in Western Europe. During the Cold War, Europe was divided along the Iron Curtain between NATO in the west and the Warsaw Pact in the east, until the revolutions of 1989 and fall of the Berlin Wall. In 1955, the Council of Europe was formed following a speech by Sir Winston Churchill and it includes all states except for Belarus, Kazakhstan and Vatican City. Further European integration by some states led to the formation of the European Union, the EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The European Anthem is Ode to Joy and states celebrate peace, in classical Greek mythology, Europa is the name of either a Phoenician princess or of a queen of Crete. The name contains the elements εὐρύς, wide, broad and ὤψ eye, broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. For the second part also the divine attributes of grey-eyed Athena or ox-eyed Hera. The same naming motive according to cartographic convention appears in Greek Ανατολή, Martin Litchfield West stated that phonologically, the match between Europas name and any form of the Semitic word is very poor. Next to these there is also a Proto-Indo-European root *h1regʷos, meaning darkness. Most major world languages use words derived from Eurṓpē or Europa to refer to the continent, in some Turkic languages the originally Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa
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North America
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North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16. 5% of the land area. North America is the third largest continent by area, following Asia and Africa, and the fourth by population after Asia, Africa, and Europe. In 2013, its population was estimated at nearly 565 million people in 23 independent states, or about 7. 5% of the worlds population, North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge. The so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago, the Classic stage spans roughly the 6th to 13th centuries. The Pre-Columbian era ended with the migrations and the arrival of European settlers during the Age of Discovery. Present-day cultural and ethnic patterns reflect different kind of interactions between European colonists, indigenous peoples, African slaves and their descendants, European influences are strongest in the northern parts of the continent while indigenous and African influences are relatively stronger in the south. Because of the history of colonialism, most North Americans speak English, Spanish or French, the Americas are usually accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass previously unknown by Europeans. In 1507, Waldseemüller produced a map, in which he placed the word America on the continent of South America. He explained the rationale for the name in the accompanying book Cosmographiae Introductio, for Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespuccis name, but in its feminine form America, following the examples of Europa, Asia and Africa. Later, other mapmakers extended the name America to the continent, In 1538. Some argue that the convention is to use the surname for naming discoveries except in the case of royalty, a minutely explored belief that has been advanced is that America was named for a Spanish sailor bearing the ancient Visigothic name of Amairick. Another is that the name is rooted in a Native American language, the term North America maintains various definitions in accordance with location and context. In Canadian English, North America may be used to refer to the United States, alternatively, usage sometimes includes Greenland and Mexico, as well as offshore islands
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South America
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South America is a continent located in the western hemisphere, mostly in the southern hemisphere, with a relatively small portion in the northern hemisphere. It may also be considered a subcontinent of the Americas, which is the used in nations that speak Romance languages. The reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean, North America and it includes twelve sovereign states, a part of France, and a non-sovereign area. In addition to this, the ABC islands of the Kingdom of the Netherlands, Trinidad and Tobago, South America has an area of 17,840,000 square kilometers. Its population as of 2005 has been estimated at more than 371,090,000, South America ranks fourth in area and fifth in population. Brazil is by far the most populous South American country, with more than half of the population, followed by Colombia, Argentina, Venezuela. In recent decades Brazil has also concentrated half of the regions GDP and has become a first regional power, most of the population lives near the continents western or eastern coasts while the interior and the far south are sparsely populated. Most of the continent lies in the tropics, the continents cultural and ethnic outlook has its origin with the interaction of indigenous peoples with European conquerors and immigrants and, more locally, with African slaves. Given a long history of colonialism, the majority of South Americans speak Portuguese or Spanish. South America occupies the portion of the Americas. The continent is delimited on the northwest by the Darién watershed along the Colombia–Panama border. Almost all of mainland South America sits on the South American Plate, South Americas major mineral resources are gold, silver, copper, iron ore, tin, and petroleum. These resources found in South America have brought high income to its countries especially in times of war or of rapid growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity often has hindered the development of diversified economies and this is leading to efforts to diversify production to drive away from staying as economies dedicated to one major export. South America is one of the most biodiverse continents on earth, South America is home to many interesting and unique species of animals including the llama, anaconda, piranha, jaguar, vicuña, and tapir. The Amazon rainforests possess high biodiversity, containing a proportion of the Earths species. Brazil is the largest country in South America, encompassing around half of the land area
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Metriorhynchinae
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Metriorhynchinae is a subfamily of metriorhynchid crocodyliforms from the late Middle Jurassic to the Early Cretaceous of Europe, North America and South America. Named by Fitzinger, in 1843, it contains the metriorhynchids Metriorhynchus, Gracilineustes, the last two taxa form a tribe within Metriorhynchinae, the Rhacheosaurini. Metriorhynchinae is one of two subfamilies of Metriorhynchidae, the other being Geosaurinae, Metriorhynchinae is a stem-based taxon defined in 2009 as the most inclusive clade consisting of Metriorhynchus geoffroyii, but not Geosaurus giganteus. Rhacheosaurini is a taxon and it was named and defined by Mark T. Young. Bell and Stephen L. Brusatte in 2011 as the most inclusive clade including Rhacheosaurus gracilis, but not Metriorhynchus geoffroyii and Gracilineustes leedsi. The cladogram below follows the topology from a 2010 analysis by Mark T. Young, Stephen L. Brusatte, Marcello Ruta and Marco Brandalise de Andrade with clade names from Young et al
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Phylogenetic nomenclature
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Phylogenetic nomenclature, often called cladistic nomenclature, is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. Phylogenetic nomenclature is not regulated, but the International Code of Phylogenetic Nomenclature is intended to regulate it once it is ratified. Phylogenetic nomenclature ties names to clades, groups consisting of an ancestor and these groups can equivalently be called monophyletic. There are slightly different ways of specifying the ancestor, which are discussed below, once the ancestor is specified, the meaning of the name is fixed, the ancestor and all organisms which are its descendants are included in the named taxon. Listing all these organisms requires the full phylogenetic tree to be known, in practice, there are only one or more hypotheses as to the correct tree. Different hypotheses lead to different organisms being thought to be included in the named taxon, in this sense the name is independent of theory revision. Phylogenetic nomenclature ties names to clades, groups consisting solely of an ancestor, all that is needed to specify a clade, therefore, is to designate the ancestor. There are a number of ways of doing this, commonly, the ancestor is indicated by its relation to two or more specifiers that are mentioned explicitly. The diagram shows three ways of doing this. A node-based definition could read, the last common ancestor of A and B, thus, the entire line below the junction of A and B does not belong to the clade to which the name with this definition refers. Example, The sauropod dinosaurs consist of the last common ancestor of Vulcanodon and Apatosaurus and this ancestor was the first sauropod. C could include other dinosaurs like Stegosaurus, a branch-based definition, often called a stem-based definition, could read, the first ancestor of A which is not also an ancestor of C, and all descendants of that ancestor. Thus, the line below the junction of A and B does belong to the clade to which the name with this definition refers. Example, The rodents consist of the first ancestor of the mouse that is not also an ancestor of the eastern cottontail rabbit together with all descendants of that ancestor. Here, the ancestor is the very first rodent, B is some other descendant, perhaps the red squirrel. An apomorphy-based definition could read, the first ancestor of A to possess trait M that is inherited by A, in the diagram, M evolves at the intersection of the horizontal line with the tree. Thus, the clade to which the name with this definition refers contains that part of the line below the last common ancestor of A and B which corresponds to ancestors possessing the apomorphy M, the lower part of the line is excluded. It is not required that B have trait M, it may have disappeared in the leading to B
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Metriorhynchus
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Metriorhynchus is an extinct genus of marine crocodyliform that lived in the oceans during the Middle to Late Jurassic. Metriorhynchus was named by the German palaeontologist Christian von Meyer in 1830, Metriorhynchus was a carnivore that spent much, if not all, its life out at sea. Where Metriorhynchus mated, whether on land or at sea, is currently unknown, the name Metriorhynchus means Moderate snout, and is derived from the Greek Metrio- and -rhynchos. Fossil specimens referrable to Metriorhynchus are known from Middle-Late Jurassic deposits of England, France, species in this genus were traditionally classed into two skull groups, longirostrine and brevirostrine. However, there has been some contention as to how many of species are valid. All brevirostrine species have been transferred to the genera Purranisaurus and Suchodus, eudes-Deslongchamps found there to be four Callovian species, M. superciliosus, M. moreli, M. blainvillei, and M. brachyrhynchus. Andrews considered there to be seven valid species, M. superciliosus, M. moreli, M. brachyrhynchus, M. durobrivensis, M. cultridens, M. leedsi and M. laeve. Adams-Tresman using linear morphometrics however could only distinguish between the two groups, so she found there to be two species, M. superciliosus and M. brachyrhynchus. Vignaud however, considered there to be three Callovian species, M. superciliosus, M. brachyrhynchus and M. leedsi, M. superciliosus, Western Europe of the Middle-Late Jurassic, M. moreli, M. blainvillei, and M. jaekeli are junior synonyms. M. hastifer, Western Europe of the Late Jurassic M. geoffroyii, Western Europe of the Late Jurassic, M. palpebrosus, two longirsotrine species, M. acutus and M. leedsi have been referred to the genus Gracilineustes. Fragmentary remains attributed to Metriorhynchus are known from South America during the Bajocian and Bathonian, however, phylogenetic analysis has shown that these species cannot be referred to Metriorhynchus. The genera Purranisaurus and Suchodus have been considered synonyms of Metriorhynchus, Recent phylogenetic analyses however. Some of the forms, however, do appear to form a natural group. The cladogram presented below follows an analysis by Mark Young and Marco Brandalise de Andrade, averaging 3 metres in length, Metriorhynchus was of a similar size to modern crocodiles. However, it had a body and a finned tail. Recent examination of the specimens of Metriorhynchus superciliosus, have shown that adults of this species had well-developed salt glands. This means that like Geosaurus it would have been able to drink salt-water, even though Metriorhynchus was an effective predator, it was vulnerable to predation from apex predators such as Liopleurodon which could grow to 6.39 meters in length. Since Metriorhynchus had lost its osteoderms, armour scutes, to more efficient swimmers it would have had little defense against larger marine predators
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Cladistics
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Therefore, members of a group are assumed to share a common history and are considered to be closely related. The techniques and nomenclature of cladistics have been applied to other disciplines, Cladistics in the original sense refers to a particular set of methods used in phylogenetic analysis, although it is now sometimes used to refer to the whole field. What is now called the cladistic method appeared as early as 1901 with a work by Peter Chalmers Mitchell for birds and subsequently by Robert John Tillyard in 1921, Hennig referred to his own approach as phylogenetic systematics. Phenetics was championed at this time by the numerical taxonomists Peter Sneath and Robert Sokal, originally conceived, if only in essence, by Willi Hennig in a book published in 1950, cladistics did not flourish until its translation into English in 1966. Today, cladistics is the most popular method for constructing phylogenies from morphological, unlike phenetics, cladistics is specifically aimed at reconstructing evolutionary histories. The way for computational phylogenetics was paved by phenetics, a set of commonly used from the 1950s to 1980s. Phenetics did not try to reconstruct phylogenetic trees, rather, it tried to build dendrograms from similarity data, the cladistic method interprets each character state transformation implied by the distribution of shared character states among taxa as a potential piece of evidence for grouping. The outcome of an analysis is a cladogram – a tree-shaped diagram that is interpreted to represent the best hypothesis of phylogenetic relationships. Cladists contend that these models are unjustified, every cladogram is based on a particular dataset analyzed with a particular method. Different datasets and different methods, not to mention violations of the mentioned assumptions, only scientific investigation can show which is more likely to be correct. Since the cladograms provide competing accounts of events, at most one of them is correct. Within the primates, all anthropoids are hypothesized to have had a common ancestor all of whose descendants were anthropoids, the prosimians, on the other hand, form a paraphyletic taxon. When two or more taxa that are not nested within each other share a plesiomorphy, it is a symplesiomorphy, symplesiomorphies do not mean that the taxa that exhibit that character state are necessarily closely related. For example, Reptilia is traditionally characterized by being cold-blooded, whereas birds are warm-blooded, an apomorphy or derived state is an innovation. It can thus be used to diagnose a clade – or even to help define a clade name in phylogenetic nomenclature, features that are derived in individual taxa are called autapomorphies. Autapomorphies express nothing about relationships among groups, clades are identified by synapomorphies, for example, the possession of digits that are homologous with those of Homo sapiens is a synapomorphy within the vertebrates. The tetrapods can be singled out as consisting of the first vertebrate with such digits homologous to those of Homo sapiens together with all descendants of this vertebrate and it is therefore inferred to have evolved by convergence or reversal. Both mammals and birds are able to maintain a constant body temperature
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Cladogram
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A cladogram is a diagram used in cladistics to show relations among organisms. A cladogram uses lines that branch off in different directions ending at a clade, there are many shapes of cladograms but they all have lines that branch off from other lines. The lines can be traced back to where they branch off and these branching off points represent a hypothetical ancestor which can be inferred to exhibit the traits shared among the terminal taxa above it. This hypothetical ancestor might then provide clues about the order of evolution of features, adaptation. The characteristics used to create a cladogram can be categorized as either morphological or molecular. Prior to the advent of DNA sequencing, cladistic analysis primarily used morphological data, behavioral data may also be used. As DNA sequencing has become cheaper and easier, molecular systematics has become a more and more popular way to infer phylogenetic hypotheses. Another powerful method of reconstructing phylogenies is the use of genomic retrotransposon markers, researchers must decide which character states are ancestral and which are derived, because only synapomorphic character states provide evidence of grouping. This determination is usually done by comparison to the states of one or more outgroups. States shared between the outgroup and some members of the in-group are symplesiomorphies, states that are present only in a subset of the in-group are synapomorphies, note that character states unique to a single terminal do not provide evidence of grouping. The choice of an outgroup is a step in cladistic analysis because different outgroups can produce trees with profoundly different topologies. A homoplasy is a state that is shared by two or more taxa due to some cause other than common ancestry. The two main types of homoplasy are convergence and reversion, however, homoplasy is often not evident from inspection of the character itself, and is then detected by its incongruence on a most-parsimonious cladogram. Note that characters that are homoplastic may still contain phylogenetic signal, a well-known example of homoplasy due to convergent evolution would be the character, presence of wings. Though the wings of birds, bats, and insects serve the function, each evolved independently. Of course, the reason a homoplasy is recognizable in the first place is because there are other characters that imply a pattern of relationships that reveal its homoplastic distribution. A cladogram is the result of a parsimony analysis, which groups taxa on the basis of synapomorphies alone. There are many other algorithms that treat data somewhat differently
39.
Wikidata
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Wikidata is a collaboratively edited knowledge base operated by the Wikimedia Foundation. It is intended to provide a source of data which can be used by Wikimedia projects such as Wikipedia. This is similar to the way Wikimedia Commons provides storage for files and access to those files for all Wikimedia projects. Wikidata is powered by the software Wikibase, Wikidata is a document-oriented database, focused on items. Each item represents a topic and is identified by a number, prefixed with the letter Q—for example. This enables the basic information required to identify the topic the item covers to be translated without favouring any language, information is added to items by creating statements. Statements take the form of pairs, with each statement consisting of a property. The creation of the project was funded by donations from the Allen Institute for Artificial Intelligence, the Gordon and Betty Moore Foundation, at this time, only the first phase was available. Historically, a Wikipedia article would include a list of links, being links to articles on the same topic in other editions of Wikipedia. Initially, Wikidata was a repository of interlanguage links. No Wikipedia language editions were able to access Wikidata, so they needed to continue to maintain their own lists of interlanguage links, on 14 January 2013, the Hungarian Wikipedia became the first to enable the provision of interlanguage links via Wikidata. This functionality was extended to the Hebrew and Italian Wikipedias on 30 January, to the English Wikipedia on 13 February, on 23 September 2013, phase 1 went live on Wikimedia Commons. The first aspects of the second phase were deployed on 4 February 2013, the values were initially limited to two data types, with more data types to follow later. The first new type, string, was deployed on 6 March, the ability of the various language editions of Wikipedia to access data added to Wikidata as part of phase two was rolled out progressively between 27 March and 25 April 2013. On 16 September 2015, Wikidata began allowing so-called arbitrary access, for example, in the past the article about Berlin you could not access data about Germany, but with arbitrary access it could. On 27 April 2016 arbitrary access was activated on Wikimedia Commons, phase 3 will involve database querying and the creation of lists based on data stored on Wikidata. As of October 2016 two tools for querying Wikidata were available, AutoList and PetScan, additionally to a public SPARQL endpoint, there is concern that the project is being influenced by lobbying companies, PR professionals and search engine optimizers. As of December 2015, according to Wikimedia statistics, half of the information in Wikidata is unsourced, another 30% is labeled as having come from Wikipedia, but with no indication as to which article
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Prehistory
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Prehistory means literally before history, from the Latin word for before, præ, and Greek ιστορία. Neighbouring civilisations were the first to follow, most other civilisations reached the end of prehistory during the Iron Age. The period when a culture is written about by others, but has not developed its own writing is known as the protohistory of the culture. By definition, there are no records from human prehistory. Clear techniques for dating were not well-developed until the 19th century and this article is concerned with human prehistory as defined here above. There are separate articles for the history of the Earth. However, for the race as a whole, prehistory ends when recorded history begins with the accounts of the ancient world around the 4th millennium BC. For example, in Egypt it is accepted that prehistory ended around 3200 BC, whereas in New Guinea the end of the prehistoric era is set much more recently. The three-age system is the periodization of prehistory into three consecutive time periods, named for their respective predominant tool-making technologies, Stone Age Bronze Age Iron Age. The notion of prehistory began to surface during the Enlightenment in the work of antiquarians who used the word primitive to describe societies that existed before written records, the first use of the word prehistory in English, however, occurred in the Foreign Quarterly Review in 1836. The main source for prehistory is archaeology, but some scholars are beginning to more use of evidence from the natural and social sciences. This view has been articulated by advocates of deep history, human population geneticists and historical linguists are also providing valuable insight for these questions. Human prehistory differs from history not only in terms of its chronology, restricted to material processes, remains and artifacts rather than written records, prehistory is anonymous. Because of this, reference terms that use, such as Neanderthal or Iron Age are modern labels with definitions sometimes subject to debate. Palaeolithic means Old Stone Age, and begins with the first use of stone tools, the Paleolithic is the earliest period of the Stone Age. The early part of the Palaeolithic is called the Lower Palaeolithic, evidence of control of fire by early humans during the Lower Palaeolithic Era is uncertain and has at best limited scholarly support. The most widely accepted claim is that H. erectus or H. ergaster made fires between 790,000 and 690,000 BP in a site at Bnot Yaakov Bridge, Israel. The use of fire enabled early humans to cook food, provide warmth, Early Homo sapiens originated some 200,000 years ago, ushering in the Middle Palaeolithic
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Archosaur
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Archosaurs are a group of diapsid amniotes whose living representatives consist of birds and crocodilians. This group also includes all extinct dinosaurs, extinct crocodilian relatives. Archosauria, the clade, is a crown group that includes the most recent common ancestor of living birds. It includes two clades, Pseudosuchia, which includes crocodilians and their extinct relatives, and Ornithosuchia. Archosaurs can be distinguished from other tetrapods on the basis of synapomorphies, or shared characteristics. The simplest and most widely agreed synapomorphies of archosaurs include teeth set in sockets, antorbital and mandibular fenestrae, being set in sockets, the teeth were less likely to be torn loose during feeding. This feature is responsible for the name thecodont, which used to apply to many Triassic archosaurs. Some archosaurs, such as birds, are secondarily toothless, antorbital fenestrae reduced the weight of the skull, which was relatively large in early archosaurs, rather like that of modern crocodilians. Mandibular fenestrae may also have reduced the weight of the jaw in some forms, the fourth trochanter provides a large site for the attachment of muscles on the femur. There is some debate about when archosaurs first appeared and those who classify the Permian reptiles Archosaurus rossicus and/or Protorosaurus speneri as true archosaurs maintain that archosaurs first appeared in the late Permian. The earliest archosaurs were rauisuchians, such as Scythosuchus and Tsylmosuchus, synapsids were the dominant land vertebrates throughout the Permian, but most perished in the Permian-Triassic extinction event. Very few large synapsids survived the event, although one form, Lystrosaurus, but archosaurs quickly became the dominant land vertebrates in the early Triassic. The two most commonly suggested explanations for this are, Archosaurs made more progress towards erect limbs than synapsids. An objection to this explanation is that became dominant while they still had sprawling or semi-erect limbs, similar to those of Lystrosaurus. The early Triassic was predominantly arid, because most of the land was concentrated in the supercontinent Pangaea. Archosaurs were probably better at conserving water than early synapsids because, Modern diapsids excrete uric acid and it is reasonable to suppose that archosaurs also excreted uric acid, and therefore were good at conserving water. The aglandular skins of diapsids would also have helped to conserve water, Modern mammals excrete urea, which requires a lot of water to keep it dissolved. Their skins also contain many glands, which also lose water, assuming that early synapsids had similar features, e. g. as argued by the authors of Palaeos, they were at a disadvantage in a mainly arid world
