1.
Megaannum
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A year is the orbital period of the Earth moving in its orbit around the Sun. Due to the Earths axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the globe, four seasons are recognized, spring, summer, autumn. In tropical and subtropical regions several geographical sectors do not present defined seasons, but in the seasonal tropics, a calendar year is an approximation of the number of days of the Earths orbital period as counted in a given calendar. The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a year of 366 days, as do the Julian calendars. For the Gregorian calendar the average length of the year across the complete leap cycle of 400 years is 365.2425 days. The ISO standard ISO 80000-3, Annex C, supports the symbol a to represent a year of either 365 or 366 days, in English, the abbreviations y and yr are commonly used. In astronomy, the Julian year is a unit of time, it is defined as 365.25 days of exactly 86400 seconds, totalling exactly 31557600 seconds in the Julian astronomical year. The word year is used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year. Similarly, year can mean the period of any planet, for example. The term can also be used in reference to any long period or cycle, west Saxon ġēar, Anglian ġēr continues Proto-Germanic *jǣran. Cognates are German Jahr, Old High German jār, Old Norse ár and Gothic jer, all the descendants of the Proto-Indo-European noun *yeh₁rom year, season. Cognates also descended from the same Proto-Indo-European noun are Avestan yārǝ year, Greek ὥρα year, season, period of time, Old Church Slavonic jarŭ, Latin annus is from a PIE noun *h₂et-no-, which also yielded Gothic aþn year. Both *yeh₁-ro- and *h₂et-no- are based on verbal roots expressing movement, *h₁ey- and *h₂et- respectively, the Greek word for year, ἔτος, is cognate with Latin vetus old, from the PIE word *wetos- year, also preserved in this meaning in Sanskrit vat-sa- yearling and vat-sa-ras year. Derived from Latin annus are a number of English words, such as annual, annuity, anniversary, etc. per annum means each year, anno Domini means in the year of the Lord. No astronomical year has an number of days or lunar months. Financial and scientific calculations often use a 365-day calendar to simplify daily rates, in the Julian calendar, the average length of a year is 365.25 days. In a non-leap year, there are 365 days, in a year there are 366 days
2.
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
3.
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
4.
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
5.
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
6.
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
7.
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
8.
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
9.
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
10.
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
11.
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
12.
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
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Neogene
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The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene, some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. During this period, mammals and birds continued to evolve into modern forms. Early hominids, the ancestors of humans, appeared in Africa near the end of the period, some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the ocean currents from the Pacific to the Atlantic ocean. The global climate cooled considerably over the course of the Neogene, the terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period. The continents in the Neogene were very close to their current positions, the Isthmus of Panama formed, connecting North and South America. The Indian subcontinent continued to collide with Asia, forming the Himalayas, sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America. The global climate became seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the current Ice Age began, marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the part of the period. Mammals and birds continued to be the dominant terrestrial vertebrates, the first hominids, the ancestors of humans, appeared in Africa and spread into Eurasia. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones, grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison. The Neogene traditionally ended at the end of the Pliocene Epoch, just before the definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to also include ongoing geological time in the Neogene, by dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The International Commission on Stratigraphy once proposed that the Quaternary be considered a sub-era of the Neogene, with a date of 2.58 Ma. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs, thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. Digital Atlas of Neogene Life for the Southeastern United States — by San Jose State University via Web Archive
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Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
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Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
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Chordate
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Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland
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Dinosaur
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Dinosaurs are a diverse group of reptiles of the clade Dinosauria that first appeared during the Triassic. Although the exact origin and timing of the evolution of dinosaurs is the subject of active research and they became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago. Their dominance continued through the Jurassic and Cretaceous periods and ended when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups 66 million years ago, until the late 20th century, all groups of dinosaurs were believed to be extinct. As such, birds were the dinosaur lineage to survive the mass extinction event. This article deals primarily with non-avian dinosaurs, Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides perciform fish, using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs. Dinosaurs are represented on every continent by both extant species and fossil remains, while dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, and some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, evidence suggests that egg laying and nest building are additional traits shared by all dinosaurs.7 meters and heights of 18 meters and were the largest land animals of all time. Still, the idea that dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large. Many dinosaurs were small, Xixianykus, for example, was only about 50 cm long. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the community believed dinosaurs to have been sluggish. Most research conducted since the 1970s, however, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction. The large sizes of some groups, as well as their seemingly monstrous and fantastic nature, have ensured dinosaurs regular appearance in best-selling books and films. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, the term is derived from the Greek words δεινός and σαῦρος. Though the taxonomic name has often interpreted as a reference to dinosaurs teeth, claws. Instead, dinosaurs, like many forms of reptile sub-groups, did not exhibit characteristics which were traditionally regarded as reptilian. Under phylogenetic nomenclature, dinosaurs are usually defined as the group consisting of Triceratops, Neornithes, their most recent common ancestor, Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. In traditional taxonomy, birds were considered a class that had evolved from dinosaurs
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Saurischia
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Saurischia is one of the two basic divisions of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure, though today most paleontologists classify Saurischia as a clade rather than an order. All carnivorous dinosaurs are saurischians, as are all of the birds, at the end of the Cretaceous Period, all saurischians except the birds became extinct in the course of the Cretaceous–Paleogene extinction event. Birds, as descendants of one group of theropod dinosaurs, are a sub-clade of saurischian dinosaurs in phylogenetic classification. Saurischian dinosaurs are traditionally distinguished from ornithischian dinosaurs by their pelvic structure. The ornithischians pelvis is arranged with the pubis rotated backward, parallel with the ischium, often also with a forward-pointing process, the saurischian hip structure led Seeley to name them lizard-hipped dinosaurs, because they retained the ancestral hip anatomy also found in modern lizards and other reptiles. In his paper naming the two groups, Seeley reviewed previous classification schemes put forth by other paleontologists to divide up the traditional order Dinosauria. He preferred one that had put forward by Othniel Charles Marsh in 1878, which divided dinosaurs into four orders, Sauropoda, Theropoda, Ornithopoda. He found this in the configuration of the hip bones, and he placed the Stegosauria and Ornithopoda in the Ornithischia, and the Theropoda and Sauropoda in the Saurischia. One alternate hypothesis challenging Seeleys classification was proposed by Robert T. Bakker in his 1986 book The Dinosaur Heresies, bakkers classification separated the theropods into their own group and placed the two groups of herbivorous dinosaurs together in a separate group he named the Phytodinosauria. However, it was found that segnosaurs were an unusual type of herbivorous theropod saurischian closely related to birds
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Sauropodomorpha
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Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to large sizes, had long necks and tails, were quadrupedal. The prosauropods, which preceded the sauropods, were smaller and were able to walk on two legs. Sauropodomorphs were adapted to browsing higher than any other contemporary herbivore and this feeding strategy is supported by many of their defining characteristics, such as, a light, tiny skull on the end of a long neck and a counterbalancing long tail. Their teeth were weak, and shaped like leaves or spoons, instead of grinding teeth, they had stomach stones, similar to the gizzard stones of modern birds and crocodiles, to help digest tough plant fibers. The front of the upper mouth bends down in what may be a beak, ultimately the largest sauropods, like Supersaurus, Diplodocus hallorum, and Argentinosaurus, reached 30–40 metres in length, and 60, 000–100,000 kilograms or more in mass. Initially bipedal, as their size increased they evolved a four-legged graviportal gait adapted only to walking slowly on land, the early sauropodomorphs were most likely omnivores as their shared common ancestor with the other saurischian lineage was a carnivore. Therefore, their evolution to herbivory went hand in hand with their increasing size and they also had large nostrils, and retained a thumb with a big claw, which may have been used for defense — though their primary defensive adaptation was their extreme size. Sauropodomorphs can be distinguished as a group on the basis of some of the following synapomorphies, the distal part of the tibia is covered by an ascending process of the astragalus. Their hind limbs are short compared to their torso length. The presence of three or more sacral vertebrae, the teeth are thin, flat and are spatula-like, with bladed and serrated crowns. Their perceived decline in the early Cretaceous is most likely a bias in sampling, as most fossils are known from Europe. Sauropods were still the dominant herbivores in the Gondwanan landmasses, however, the spread of flowering plants and advanced ornithischians, another major group of herbivorous dinosaurs, are most likely not a major factor in sauropod decline in the northern continents. Like all non-avian dinosaurs, the sauropodomorphs became extinct 66 Mya, the earliest and most basal sauropodomorphs known are Chromogisaurus novasi and Panphagia protos, both from the Ischigualasto Formation, dated to 231.4 million years ago. Some studies have found Eoraptor lunensis, traditionally considered a theropod, to be an member of the sauropodomorph lineage. Additional fragmentary remains from Madagascar may represent an even earlier sauropodomorph from the middle Triassic, Sauropodomorpha is one of the two major clades within the order Saurischia. The sauropodomorphs sister group, the Theropoda, includes bipedal carnivores like Velociraptor and Tyrannosaurus, in Linnaean taxonomy, Sauropodomorpha is either a suborder or is left unranked. It was originally established by Friedrich von Huene in 1932, who broke it into two groups, the forms within Prosauropoda, and their descendants, the giant Sauropoda
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Sauropoda
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Sauropoda, or the sauropods, are an infraorder of saurischian dinosaurs. They had very long necks, long tails, small heads and they are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land. Well-known genera include Brachiosaurus, Diplodocus, Apatosaurus and Brontosaurus, sauropods first appeared in the late Triassic Period, where they somewhat resembled the closely related group Prosauropoda. By the Late Jurassic, sauropods had become widespread, by the Late Cretaceous, those groups had mainly been replaced by the titanosaurs, which had a near-global distribution. However, as all other non-avian dinosaurs alive at the time. Fossilised remains of sauropods have been found on every continent, including Antarctica, the name Sauropoda was coined by O. C. Marsh in 1878, and is derived from Greek, meaning lizard foot, sauropods are one of the most recognizable groups of dinosaurs, and have become a fixture in popular culture due to their large sizes. Complete sauropod fossil finds are rare, many species, especially the largest, are known only from isolated and disarticulated bones. Many near-complete specimens lack heads, tail tips and limbs, sauropods were herbivorous, usually quite long-necked quadrupeds, often with spatulate teeth. They had tiny heads, massive bodies, and most had long tails and their hind legs were thick, straight, and powerful, ending in club-like feet with five toes, though only the inner three bore claws. Their forelimbs were more slender and ended in pillar-like hands built for supporting weight. Many illustrations of sauropods in the flesh miss these facts, inaccurately depicting sauropods with hooves capping the claw-less digits of the feet, the proximal caudal vertebrae are extremely diagnostic for sauropods. The sauropods most defining characteristic was their size, even the dwarf sauropods were counted among the largest animals in their ecosystem. Their only real competitors in terms of size are the rorquals, but, unlike whales, sauropods were primarily land-based animals. Their body structure did not vary as much as other dinosaurs, perhaps due to size constraints, but they displayed ample variety. Some, like the diplodocids, possessed tremendously long tails, which they may have been able to crack like a whip as a signal or to deter or injure predators, or to make sonic booms. Supersaurus, at 33 to 34 metres long, was the longest sauropod known from reasonably complete remains, the holotype vertebra of Amphicoelias fragillimus may have come from an animal 58 metres long, its vertebral column would have been substantially longer than that of the blue whale. However, a research published in 2015 speculated that the estimates of A. fragillimus may have been highly exaggerated
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Brachiosauridae
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Brachiosauridae is a family of herbivorous, quadrupedal sauropod dinosaurs. Brachiosaurids had long necks that enabled them to access the leaves of trees that other sauropods would have been unable to access. In addition, they possessed thick spoon-shaped teeth which helped them to consume tough plants more efficiently than other sauropods and they have also been characterized by a few unique unambiguous synapomorphies, dorsal vertebrae with rod-like transverse processes and an ischium with an abbreviate pubic peduncle. Brachiosaurus is one of the members of the Brachiosauridae family. They thrived in the regions which are now North and South America, Africa, Europe and they first appear in the fossil record in the Middle/Late Jurassic Period and disappear in the late Early Cretaceous Period. The broad distribution of Brachiosauridae in both northern and southern continents suggests that the group originated prior to the breakup of Pangaea, in the Early Cretaceous the distribution of the family is dramatically reduced. It is still unclear whether this reduction is due to local extinctions or to the nature of the Early Cretaceous fossil record. Brachiosauridae has been defined as all titanosauriforms that are closely related to Brachiosaurus than to Saltasaurus. It is one of the three families that belongs to the Titanosauriformes clade of dinosaurs, which also includes Euhelopdidae. The Brachiosauridae family is composed of quadrupedal dinosaurs that are extremely large, the giant animals of this family can be distinguished from other taxon by their broad, thick and spoon-shaped teeth. The maxillary teeth were twisted apically, and the shape of teeth were optimal for biting off resistant vegetation. While brachiosaurids didnt perform significant food processing in their mouths, their teeth enabled them to slice through food instead of having to pull it off of tree branches. Evidence for this precision shearing consists of apical wear facets on the teeth, in addition, the characteristic long necks of brachiosaurids are distinct from those of other long-necked dinosaur taxa. They possessed a narrow neck composed of 12–13 extremely long cervical bones that was laterally inflexible and this meant that brachiosaurids could angle their necks up and lift their heads, enabling them to graze from treetops up to a height of about 14 meters. Other sauropods lacked this dorsoventral flexibility and thus their necks stretched outwards in front of them instead of upwards, however, the giant size and long necks of brachiosaurids meant that they required tremendous pressure to bring oxygenated blood to their brains. It has been proposed that they possessed a four-chambered double pump heart, with one pump for oxygenated, as in all macronarians, the forelimbs of brachiosaurids are long relative to the hindlimbs, but this trait is more pronounced in brachiosaurids. The forelimbs were very slender and the bone of the forelimb was elongated. These adaptations overall increased the length of the forelimbs, likely resulting in an uneven gait
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2006 in paleontology
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Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of fossils, tracks, burrows, cast-off parts, fossilised feces, palynomorphs. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science and this article records significant discoveries and events related to paleontology that occurred or were published in the year 2006. Vickaryous, M K.2006, New information on the anatomy of Edmontonia rugosidens Gilmore. Data coutersy of George Olshevkys dinosaur genera list
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Binomial nomenclature
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Such a name is called a binomial name, a binomen, binominal name or a scientific name, more informally it is also called a Latin name. The first part of the name identifies the genus to which the species belongs, for example, humans belong to the genus Homo and within this genus to the species Homo sapiens. The formal introduction of system of naming species is credited to Carl Linnaeus. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus. Although the general principles underlying binomial nomenclature are common to these two codes, there are differences, both in the terminology they use and in their precise rules. Similarly, both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a name is usually given, at least when it is first mentioned. In zoology Patella vulgata Linnaeus,1758, the original name given by Linnaeus was Fringilla domestica, the parentheses indicate that the species is now considered to belong in a different genus. The ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, in botany Amaranthus retroflexus L. – L. is the standard abbreviation used in botany for Linnaeus. – Linnaeus first named this bluebell species Scilla italica, Rothmaler transferred it to the genus Hyacinthoides, the ICN does not require that the dates of either publication be specified. Prior to the adoption of the binomial system of naming species. Together they formed a system of polynomial nomenclature and these names had two separate functions. First, to designate or label the species, and second, to be a diagnosis or description, such polynomial names may sometimes look like binomials, but are significantly different. For example, Gerards herbal describes various kinds of spiderwort, The first is called Phalangium ramosum, Branched Spiderwort, is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia. The Latin phrases are short descriptions, rather than identifying labels, the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné. It was in his 1753 Species Plantarum that he first began using a one-word trivial name together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as an epithet or specific name
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Macronaria
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Macronaria is a clade of sauropod dinosaurs from the Middle Jurassic to Late Cretaceous Periods of what are now North America, South America, Europe, Asia, Africa and Australia. The name means large nostrils, in reference to the nasal openings high on the head that probably supported fleshy resonating chambers. Macronaria consists of a main group, Titanosauriformes, along with several more basal taxa. Taxonomy after Mannion et al. and DEmic unless otherwise noted, the cladogram below follows José L. Carballido, Oliver W. M. Rauhut, Diego Pol and Leonardo Salgado. Simplified cladogram of Macronaria after DEmic, for alternative cladogramas see also Mateus et al. The Phylogenetic relationships of sauropod dinosaurs, zoological Journal of the Linnean Society
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Quadrupedalism
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Quadrupedalism or pronograde posture is a form of terrestrial locomotion in animals using four limbs or legs. An animal or machine that moves in a quadrupedal manner is known as a quadruped. The majority of quadrupeds are vertebrate animals, including such as cattle, dogs and cats. Few other animals are quadrupedal, though a few birds like the shoebill sometimes use their wings to itself after lunging at prey. Although the words quadruped and tetrapod are both derived from terms meaning four-footed, they have distinct meanings, a tetrapod is any member of the taxonomic unit Tetrapoda whereas a quadruped actually uses four limbs for locomotion. Not all tetrapods are quadrupeds and not all quadrupeds are tetrapods, the distinction between quadrupeds and tetrapods is important in evolutionary biology, particularly in the context of tetrapods whose limbs have adapted to other roles. All of these animals are tetrapods, but none is a quadruped, even snakes, whose limbs have become vestigial or lost entirely, are nevertheless tetrapods. Most quadrupedal animals are tetrapods but there are a few exceptions, for instance, among the insects, the praying mantis is a quadruped. In July 2005, in rural Turkey, scientists discovered five Kurdish siblings who had learned to walk naturally on their hands, unlike chimpanzees, which ambulate on their knuckles, the Kurdish siblings walked on their palms, allowing them to preserve the dexterity of their fingers. Many people, especially practitioners of Parkour and Freerunning and Georges Héberts Natural Method, kenichi Ito is a Japanese man famous for speed running on four limbs. Quadrupedalism is sometimes referred to as being on all fours, and is observed in crawling especially by infants, bigDog is a dynamically stable quadruped robot created in 2005 by Boston Dynamics with Foster-Miller, the NASA Jet Propulsion Laboratory, and the Harvard University Concord Field Station. Also by NASA JPL, in collaboration with University of California, Santa Barbara Robotics Lab, is RoboSimian, with emphasis on stability and it has been demonstrated at the DARPA Robotics Challenge. Bipedalism Orthograde posture Family may provide evolution clue - BBC News
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Herbivore
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A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding, horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material. A large percentage of herbivores have mutualistic gut flora that help them digest plant matter and this gut flora is made up of cellulose-digesting protozoans or bacteria living in the herbivores intestines. Herbivore is the form of a modern Latin coinage, herbivora. Richard Owen employed the term in an 1854 work on fossil teeth. Herbivora is derived from the Latin herba meaning a small plant or herb, Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms feed on autotrophs in general are known as primary consumers. Herbivory usually refers to eating plants, fungi, bacteria and protists that feed on living plants are usually termed plant pathogens. Flowering plants that obtain nutrition from other living plants are usually termed parasitic plants, there is however no single exclusive and definitive ecological classification of consumption patterns, each textbook has its own variations on the theme. Insects fed on the spores of early Devonian plants, and the Rhynie chert also provides evidence that organisms fed on plants using a pierce, during the next 75 million years, plants evolved a range of more complex organs, such as roots and seeds. There is no evidence of any organism being fed upon until the middle-late Mississippian,330.9 million years ago, further than their arthropod status, the identity of these early herbivores is uncertain. Hole feeding and skeletonisation are recorded in the early Permian, with surface fluid feeding evolving by the end of that period, Herbivory among four-limbed terrestrial vertebrates, the tetrapods developed in the Late Carboniferous. Early tetrapods were large amphibious piscivores, while amphibians continued to feed on fish and insects, some reptiles began exploring two new food types, tetrapods and plants. The entire dinosaur order ornithischia was composed with herbivores dinosaurs, carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation. In contrast, a set of adaptations was necessary for feeding on highly fibrous plant materials. Arthropods evolved herbivory in four phases, changing their approach to it in response to changing plant communities, tetrapod herbivores made their first appearance in the fossil record of their jaws near the Permio-Carboniferous boundary, approximately 300 million years ago. The earliest evidence of their herbivory has been attributed to dental occlusion, the evolution of dental occlusion led to a drastic increase in plant food processing and provides evidence about feeding strategies based on tooth wear patterns. Examination of phylogenetic frameworks of tooth and jaw morphologes has revealed that dental occlusion developed independently in several lineages tetrapod herbivores and this suggests that evolution and spread occurred simultaneously within various lineages
27.
Kimmeridgian
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In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 157.3 ±1.0 Ma and 152.1 ±0.9 Ma, the Kimmeridgian follows the Oxfordian and precedes the Tithonian. The Kimmeridgian stage takes its name from the village of Kimmeridge on the Dorset coast, the name was introduced in literature by Swiss geologist Jules Thurmann in 1832. The Kimmeridge Clay Formation has its name from the type location. It is the source for about 95% of the petroleum in the North Sea, historically the term Kimmeridgian has been used in two different ways. The base of the interval is the same but the top was defined by British stratigraphers as the base of the Portlandian whereas in France the top was defined as the base of the Tithonian. The differences have not yet fully resolved, As of 2004 Tithonian is has been seen as the uppermost stage of the Jurassic in the timescale of the ICS. The base of the Kimmeridgian is at the first appearance of ammonite species Pictonia baylei in the stratigraphic column, a global reference profile for the base had in 2009 not yet been assigned. The top of the Kimmeridgian is at the first appearance of ammonite species Hybonoticeras hybonotum and it also coincides with the top of magnetic anomaly M22An. The Kimmeridgian is sometimes subdivided into Upper and Lower substages. M, & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press
28.
Germany
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Germany, officially the Federal Republic of Germany, is a federal parliamentary republic in central-western Europe. It includes 16 constituent states, covers an area of 357,021 square kilometres, with about 82 million inhabitants, Germany is the most populous member state of the European Union. After the United States, it is the second most popular destination in the world. Germanys capital and largest metropolis is Berlin, while its largest conurbation is the Ruhr, other major cities include Hamburg, Munich, Cologne, Frankfurt, Stuttgart, Düsseldorf and Leipzig. Various Germanic tribes have inhabited the northern parts of modern Germany since classical antiquity, a region named Germania was documented before 100 AD. During the Migration Period the Germanic tribes expanded southward, beginning in the 10th century, German territories formed a central part of the Holy Roman Empire. During the 16th century, northern German regions became the centre of the Protestant Reformation, in 1871, Germany became a nation state when most of the German states unified into the Prussian-dominated German Empire. After World War I and the German Revolution of 1918–1919, the Empire was replaced by the parliamentary Weimar Republic, the establishment of the national socialist dictatorship in 1933 led to World War II and the Holocaust. After a period of Allied occupation, two German states were founded, the Federal Republic of Germany and the German Democratic Republic, in 1990, the country was reunified. In the 21st century, Germany is a power and has the worlds fourth-largest economy by nominal GDP. As a global leader in industrial and technological sectors, it is both the worlds third-largest exporter and importer of goods. Germany is a country with a very high standard of living sustained by a skilled. It upholds a social security and universal health system, environmental protection. Germany was a member of the European Economic Community in 1957. It is part of the Schengen Area, and became a co-founder of the Eurozone in 1999, Germany is a member of the United Nations, NATO, the G8, the G20, and the OECD. The national military expenditure is the 9th highest in the world, the English word Germany derives from the Latin Germania, which came into use after Julius Caesar adopted it for the peoples east of the Rhine. This in turn descends from Proto-Germanic *þiudiskaz popular, derived from *þeudō, descended from Proto-Indo-European *tewtéh₂- people, the discovery of the Mauer 1 mandible shows that ancient humans were present in Germany at least 600,000 years ago. The oldest complete hunting weapons found anywhere in the world were discovered in a mine in Schöningen where three 380, 000-year-old wooden javelins were unearthed
29.
Insular dwarfism
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This natural process is distinct from the intentional creation of dwarf breeds, called dwarfing. This process has occurred many times throughout history, with examples including dinosaurs, like Europasaurus. This process, and other island genetics artifacts, can not only on traditional islands. This can include caves, desert oases, isolated valleys and isolated mountains, there are several proposed explanations for the mechanism which produces such dwarfism. One is a process where only smaller animals trapped on the island survive. Smaller size is also advantageous from a standpoint, as it entails shorter gestation periods. In the tropics, small size should make thermoregulation easier, among carnivores, the main factor is thought to be the size and availability of prey resources, and competition is believed to be less important. In tiger snakes, insular dwarfism occurs on islands where available prey is restricted to smaller sizes than are taken by mainland snakes. Since prey size preference in snakes is generally proportional to body size, the inverse process, wherein small animals breeding on isolated islands lacking the predators of large land masses may become much larger than normal, is called island gigantism. An excellent example is the dodo, the ancestors of which were normal-sized pigeons, there are also several species of giant rats, one still extant, that coexisted with both Homo floresiensis and the dwarf stegodons on Flores. The process of insular dwarfing can occur relatively rapidly by evolutionary standards and this is in contrast to increases in maximum body size, which are much more gradual.5 log per log. Recognition that insular dwarfism could apply to dinosaurs arose through the work of Ferenc Nopcsa, a Hungarian-born aristocrat, adventurer, scholar, Nopcsa studied Transylvanian dinosaurs intensively, noticing that they were smaller than their cousins elsewhere in the world. For example, he unearthed six-meter-long sauropods, a group of dinosaurs which elsewhere commonly grew to 30 meters or more, Nopcsa deduced that the area where the remains were found was an island, Hațeg Island during the Mesozoic era. Nopcsas proposal of dinosaur dwarfism on Hațeg Island is today widely accepted after further research confirmed that the remains found are not from juveniles, pygmy three-toed sloth of Isla Escudo de Veraguas, Bradypus pygmaeus. Mnaidriensis, P. melitensis, P. falconeri Cretan elephants, Palaeoloxodon chaniensis, P. creutzburgi Cyprus dwarf elephant, Palaeoloxodon cypriotes Naxos dwarf elephant, small-bodied humans from Palau, Micronesia, similar in size to the Flores hominins. Carnivorans Canids Channel Island fox in California, Urocyon littoralis Cozumel fox, † Birds King Island emu, Dromaius novaehollandiae ater † Kangaroo Island emu, Dromaius baudinianus † Lizards Madagascar dwarf chamaeleon, Brookesia minima Brookesia micra, a less than 3
30.
Oker
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The Oker is a river in Lower Saxony, Germany, that has historically formed an important political boundary. It is a tributary of the River Aller,105 kilometres in length. The rivers name was recorded around 830 as Obacra and, later, the origin of the name is derived from the roots ov- and -akara meaning “upper” and “onward rushing” as distinct from its tributary, the Ecker, whose name means only “onward rushing”. The Oker rises at about 910 metres in the Harz National Park in an area on the Bruchberg in the Harz mountains of central Germany. This early section is known as the Große Oker and it is impounded below Altenau by the Oker Dam, from the dam wall to the former village of Oker, which is today part of the borough of Goslar, the Oker is on certain occasions suitable for canoeing. This section, often called the Oker Valley, includes the Romkerhall Waterfall, here the Romke stream drops about 64 metres in height over a waterfall laid out in 1863 into the Oker. Downstream in the rivers fast-flowing waters, the Verlobungsinsel is to be found, left and right of the Oker in this area are many crags that are popular with climbers. In the Goslar vicinity of Oker the river is polluted with heavy metals from the slag heaps as well as groundwater. From the village of Oker the River Oker flows away in a direction to Vienenburg. After these two confluences the river continues southeast past the Harly Forest, after which it bends north to flow through Schladen, in south Brunswick the Oker is dammed by the Eisenbüttel Weir. In the Bürgerpark shortly before Brunswicks old town the Oker divides into the western and eastern bypass channels which circumnavigate the historic city centre at a higher level. These channels were laid in the 16th century as the moats of the towns defences. The actual course of the Oker through the centre of the town was covered and, today, the water level in the city area is controlled by the St. Peters Gate Weir in the western and the Wends Weir in the eastern ditch. It then flows down to its mouth into the River Aller, north of Schladen the royal palace of Werla was established on the banks about 20 metres above the river bed. Since the Expo 2000 bridges over the Oker in Brunswick and its area were artistically designed. Heavy metal pollution of the Oker Description of white water canoe section between Kraftwerk and Nachstaubecken with many photos Oste class fleet service ship
31.
Lower Saxony
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Lower Saxony is a German state situated in northwestern Germany and is second in area, with 47,624 square kilometres, and fourth in population among the sixteen Länder of Germany. In rural areas Northern Low Saxon, a dialect of Low German, and Saterland Frisian, a variety of Frisian, are still spoken, but the number of speakers is declining. Lower Saxony borders on the North Sea, the states of Schleswig-Holstein, Hamburg, Mecklenburg-Vorpommern, Brandenburg, Saxony-Anhalt, Thuringia, Hesse and North Rhine-Westphalia, and the Netherlands. Furthermore, the state of Bremen forms two enclaves within Lower Saxony, one being the city of Bremen, the other, its city of Bremerhaven. In fact, Lower Saxony borders more neighbours than any other single Bundesland, the states principal cities include the state capital Hanover, Braunschweig, Lüneburg, Osnabrück, Oldenburg, Hildesheim, Wolfenbüttel, Wolfsburg and Göttingen. The northwestern area of Lower Saxony, which lies on the coast of the North Sea, is called East Frisia, in the extreme west of Lower Saxony is the Emsland, a traditionally poor and sparsely populated area, once dominated by inaccessible swamps. The northern half of Lower Saxony, also known as the North German Plains, is almost invariably flat except for the hills around the Bremen geestland. Towards the south and southwest lie the northern parts of the German Central Uplands, the Weser Uplands, between these two lie the Lower Saxon Hills, a range of low ridges. Thus, Lower Saxony is the only Bundesland that encompasses both maritime and mountainous areas, Lower Saxonys major cities and economic centres are mainly situated in its central and southern parts, namely Hanover, Braunschweig, Osnabrück, Wolfsburg, Salzgitter, Hildesheim and Göttingen. Oldenburg, near the coastline, is another economic centre. To the north, the Elbe river separates Lower Saxony from Hamburg, Schleswig-Holstein, Mecklenburg-Western Pomerania, the banks just south of the Elbe are known as Altes Land. Due to its local climate and fertile soil, it is the states largest area of fruit farming. Most of the territory was part of the historic Kingdom of Hanover. It was created by the merger of the State of Hanover with several states in 1946. Lower Saxony has a boundary in the north in the North Sea. The state and city of Bremen is an enclave surrounded by Lower Saxony. The Bremen/Oldenburg Metropolitan Region is a body for the enclave area. To the southeast the state border runs through the Harz, low mountains that are part of the German Central Uplands, in northeast Lower Saxony is Lüneburg Heath
32.
Oxfordian (stage)
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The Oxfordian is, in the ICS geologic timescale, the earliest age of the Late Jurassic epoch, or the lowest stage of the Upper Jurassic series. It spans the time between 163.5 ±4 Ma and 157.3 ±4 Ma, the Oxfordian is preceded by the Callovian and is followed by the Kimmeridgian. The Oxfordian stage was introduced into scientific writing by Alexandre Brongniart in 1827, the stage takes its name from the city of Oxford in England. The base of the Oxfordian stage is defined as the point in the record where the ammonite species Brightia thuouxensis first appears. A global reference profile for the base had in 2009 not yet been assigned, the top of the Oxfordian stage is at the first appearance of ammonite species Pictonia baylei. 1829, Tableau théorique de la succession et de la disposition la plus générale on Europa, des terrains et roches, qui composent lécorce de la terre, & Smith, A. G.2004, A Geologic Time Scale 2004, Cambridge University Press
33.
Hanover
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At the end of the Napoleonic Wars, the Electorate was enlarged to become a Kingdom with Hanover as its capital. From 1868 to 1946 Hanover was the capital of the Prussian Province of Hanover and it is now the capital of the Land of Lower Saxony. Since 2001 it has been part of the Hanover district, which is a body made up from the former district. With a population of 518,000, Hanover is a centre of Northern Germany. Hanover also hosts annual commercial trade fairs such as the Hanover Fair, every year Hanover hosts the Schützenfest Hannover, the worlds largest marksmens festival, and the Oktoberfest Hannover, the second largest such festival in Germany. In 2000, Hanover hosted the world fair Expo 2000, the Hanover fairground, due to numerous extensions, especially for the Expo 2000, is the largest in the world. Hanover is of importance because of its universities and medical school, its international airport. The city is also a crossing point of railway lines and highways. Hanover is the traditional English spelling, the German spelling is becoming more popular in English, recent editions of encyclopaedias prefer the German spelling, and the local government uses the German spelling on English websites. The traditional English spelling is used in historical contexts, especially when referring to the British House of Hanover. Hanover was founded in times on the east bank of the River Leine. Its original name Honovere may mean high bank, though this is debated, Hanover was a small village of ferrymen and fishermen that became a comparatively large town in the 13th century due to its position at a natural crossroads. As overland travel was difficult, its position on the upper navigable reaches of the river helped it to grow by increasing trade. In the 14th century the churches of Hanover were built. The beginning of industrialization in Germany led to trade in iron and silver from the northern Harz Mountains, in 1636 George, Duke of Brunswick-Lüneburg, ruler of the Brunswick-Lüneburg principality of Calenberg, moved his residence to Hanover. The Dukes of Brunswick-Lüneburg were elevated by the Holy Roman Emperor to the rank of Prince-Elector in 1692, thus the principality was upgraded to the Electorate of Brunswick-Lüneburg, colloquially known as the Electorate of Hanover after Calenbergs capital. Its electors would later become monarchs of Great Britain, the first of these was George I Louis, who acceded to the British throne in 1714. The last British monarch who ruled in Hanover was William IV, semi-Salic law, which required succession by the male line if possible, forbade the accession of Queen Victoria in Hanover
34.
Holotype
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A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, under the International Code of Zoological Nomenclature, a holotype is one of several kinds of name-bearing types. In the International Code of Nomenclature for algae, fungi, and plants and ICZN the definitions of types are similar in intent but not identical in terminology or underlying concept. For example, the holotype for the butterfly Lycaeides idas longinus is a specimen of that species. An isotype is a duplicate of the holotype and is made for plants. A holotype is not necessarily typical of that taxon, although ideally it should be, sometimes just a fragment of an organism is the holotype, particularly in the case of a fossil. For example, the holotype of Pelorosaurus humerocristatus, a herbivorous dinosaur from the early Jurassic period, is a fossil leg bone stored at the Natural History Museum in London. Even if a specimen is subsequently found, the holotype is not superseded. Under the ICN, an additional and clarifying type could be designated, an epitype under Article 9.8, a conserved type is sometimes used to correct a problem with a name which has been misapplied, this specimen replaces the original holotype. In the absence of a holotype, another type may be selected, out of a range of different kinds of type, depending on the case, a lectotype or a neotype. For example, in both the ICN and the ICZN a neotype is a type that was appointed in the absence of the original holotype. This made the name Parasuchus hislopi a nomen dubium, texan paleontologist Sankar Chatterjee proposed that a new type specimen, a complete skeleton, be designated. The International Commission on Zoological Nomenclature considered the case and agreed to replace the type specimen with the proposed neotype. Type Allotype Paratype Type species Genetypes- genetic sequence data from type specimens, BOA Photographs of type specimens of Neotropical Rhopalocera
35.
Skull
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The skull is a bony structure that forms the head of the skeleton in most vertebrates. It supports the structures of the face and provides a cavity for the brain. The skull is composed of two parts, the cranium and the mandible, in the human these two parts are the neurocranium and the viscerocranium or facial skeleton that includes the mandible as its largest bone. The skull forms the anterior most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, in the human these sensory structures are part of the facial skeleton. In some animals such as horned ungulates, the skull also has a function by providing the mount for the horns. The English word skull is probably derived from Old Norse skulle, while the Latin word cranium comes from the Greek root κρανίον, the skull is made up of a number of fused flat bones, and contains many foramina and processes, and several cavities or sinuses. For details and the constituent bones, see neurocranium and viscerocranium, the human skull is the bony structure that forms the head in the human skeleton. It supports the structures of the face and forms a cavity for the brain, like the skulls of other vertebrates, it protects the brain from injury. The skull consists of two parts, of different embryological origin—the neurocranium and the facial skeleton, the neurocranium forms the protective cranial cavity that surrounds and houses the brain and brainstem. The facial skeleton is formed by the supporting the face. Except for the mandible, all of the bones of the skull are joined together by sutures—synarthrodial joints formed by bony ossification, sometimes there can be extra bone pieces within the suture known as wormian bones or sutural bones. The human skull is considered to consist of twenty-two bones—eight cranial bones. In the neurocranium these are the bone, two temporal bones, two parietal bones, the sphenoid, ethmoid and frontal bones. The bones of the skeleton are the vomer, two nasal conchae, two nasal bones, two maxilla, the mandible, two palatine bones, two zygomatic bones, and two lacrimal bones. Some of these bones—the occipital, parietal, frontal, in the neurocranium, and the nasal, lacrimal, the skull also contains sinus cavities and numerous foramina. The sinuses are lined with respiratory epithelium and their known functions are the lessening of the weight of the skull, the aiding of resonance to the voice and the warming and moistening of the air drawn through the nasal cavity. The foramina are openings in the skull, the largest of these is the foramen magnum that allows the passage of the spinal cord as well as nerves and blood vessels. The many processes of the include the mastoid process and the zygomatic process
36.
Premaxilla
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The premaxilla is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla and usually termed as the incisive bone, other terms used for this structure include premaxillary bone or os premaxillare, and intermaxillary bone or os intermaxillare. In humans, the premaxilla is referred to as the bone and is the part of the maxilla which bears the incisor teeth. In the nasal cavity, the premaxillary element projects higher than the maxillary element behind, the palatal portion of the premaxilla is a bony plate with a generally transverse orientation. The incisive foramen is bound anteriorly and laterally by the premaxilla, in the embryo, the nasal region develops from neural crest cells which start their migration down to the face during the fourth week of gestation. A pair of symmetrical nasal placodes are each divided into medial and lateral processes by the nasal pits, the medial processes become the septum, philtrum, and premaxilla. The first ossification centers in the area of the future premaxilla appear during the week above the germ of the second incisor on the outer surface of the nasal capsule. After eleven weeks an accessory ossification center develops into the region of the premaxilla. Then a premaxillary process grow upwards to fuse with the process of the maxilla. The boundary between the premaxilla and the maxilla remains discernible after birth and a suture is often observable up to five years of age, forming the oral edge of the upper jaw in most jawed vertebrates, the premaxillary bones comprise only the central part in more primitive forms. They are fused in blowfishes and absent in cartilaginous fishes such as sturgeons, reptiles and most non-mammalian therapsids have a large, paired, intramembranous bone behind the premaxilla called the septomaxilla. Because this bone is vestigial in Acristatherium this species is believed to be the oldest known therian mammal, intriguingly the septomaxilla is still present in monotremes. The differences in the size and composition in the premaxilla of various families of bats is used for classification
37.
Braincase
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In mammals, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull. The skull can be divided into two parts, the neurocranium, which forms a case around the brain, and the facial skeleton. In the human skull, the neurocranium includes the calvaria or skullcap, the lower part of the skull is the facial skeleton, also known as the splanchnocranium. There may variably also be extra sutural bones present, below the neurocranium is a complex of openings and bones, including the foramen magnum which houses the neural spine. The auditory bullae, located in the region, aid in hearing. The size of the neurocranium is variable among mammals, the roof may contain ridges such as the temporal crests. The neurocranium arises from paraxial mesoderm, there is also some contribution of ectomesenchyme. In Chondrichthyes and other cartilaginous vertebrates this portion of the cranium does not ossify, the neurocranium is formed by the endocranium, the lower portions of the cranial vault, and the skull roof. These are not fused in fishes, and a proper neurocranium is only found in land vertebrates, the upper-frontmost part of the cranium also houses the evolutionarily newest part of the human brain, the frontal lobes
38.
Mandible
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The mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the face. It forms the lower jaw and holds the teeth in place. The mandible sits beneath the maxilla, the bone is formed from a fusion of left and right processes, and the point where these sides join, the mandibular symphysis, is still visible as a faint ridge in the midline. Like other symphyses in the body, this is a midline articulation where the bones are joined by fibrocartilage, the body of the mandible is curved somewhat like a horseshoe and has two surfaces and two borders. From the outside, the mandible is marked in the midline by a faint ridge and this ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. On either side of the symphysis, just below the teeth, is a depression, the incisive fossa, which gives origin to the mentalis. Below the second premolar tooth, on side, midway between the upper and lower borders of the body, is the mental foramen, for the passage of the mental vessels. From the inside, the mandible appears concave, near the lower part of the symphysis is a pair of laterally placed spines, termed the mental spines, which give origin to the genioglossus. Immediately below these is a pair of spines, or more frequently a median ridge or impression. In some cases the mental spines are fused to form a single eminence, in others they are absent, above the mental spines a median foramen and furrow are sometimes seen, they mark the line of union of the halves of the bone. Below the mental spines, on side of the middle line, is an oval depression for the attachment of the anterior belly of the digastric. Above the anterior part of line is a smooth triangular area against which the sublingual gland rests, and below the hinder part. To the outer lip of the border, on either side. The ramus of the mandible has four sides, two surfaces, four borders, and two processes. On the outside, the ramus is flat and marked by oblique ridges at its lower part, on the inside, the mandible presents about its center the oblique mandibular foramen, for the entrance of the inferior alveolar vessels and nerve. Behind this groove is a surface, for the insertion of the internal pterygoid muscle. The mandibular canal runs obliquely downward and forward in the ramus, and then horizontally forward in the body, on arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off two small canals which run to the cavities containing the incisor teeth. In the posterior two-thirds of the bone the canal is situated nearer the surface of the mandible
39.
Rib cage
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The rib cage is an arrangement of bones in the thorax of all vertebrates except the lamprey and the frog. It is formed by the column, ribs, and sternum and encloses the heart. A typical human rib cage consists of 24 ribs, the sternum, costal cartilages, and the 12 thoracic vertebrae. Together with the skin and associated fascia and muscles, the rib cage makes up the wall and provides attachments for the muscles of the neck, thorax, upper abdomen. Ribs are described based on their location and connection with the sternum, ribs that articulate directly with the sternum are called true ribs, whereas those that connect indirectly via cartilage are termed false ribs. The terms true and false rib describe rib pairs that are directly or indirectly attached to the sternum, the phrase true rib, or fixed rib, refers to the first seven, or vertebrosternal, rib pairs. The phrase false rib, or vertebrochondral ribs refers to the pairs of ribs. The eighth-to-tenth pairs of ribs connect to the sternum indirectly via the costal cartilages of the ribs above them and their elasticity allows ribcage movement for respiratory activity. The phrase floating rib refers to the two lowermost, the eleventh and twelfth, rib pairs, so-called because they are attached only to the not to the sternum or cartilage of the sternum. These ribs are small and delicate, and include a cartilaginous tip. The spaces between the ribs are known as intercostal spaces, they contain the intercostal muscles, nerves, arteries, each rib consists of a head, neck, and a shaft and they are numbered from top to bottom. The head of rib is the end part closest to the spine with which it articulates and it is marked by a kidney-shaped articular surface which is divided by a horizontal crest into two facets. The superior facet is smaller and articulates with the vertebra above, the transverse process of a thoracic vertebra also articulates with the rib of the same number. The crest gives attachment to the intra-articular ligament, all ribs are attached posteriorly to the thoracic vertebrae. The neck of the rib is the part that extends laterally from the head. The neck is about 3 cm long, and is placed in front of the process of the lower of the two vertebrae with which the head articulates. Its anterior surface is flat and smooth, whilst its posterior is perforated by numerous foramina and its surface rough and its upper border presents a rough crest for the attachment of the anterior costotransverse ligament, its lower border is rounded. On the posterior surface at the junction of the neck and body, and nearer the lower than the border, is an eminence—the tubercle, it consists of an articular
40.
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
. PMID 20435913.
