1.
Holocene
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The Holocene is the geological epoch that began after the Pleistocene at approximately 11,700 years before present. The term Recent has often used as an exact synonym of Holocene. The Holocene is part of the Quaternary period and its name comes from the Ancient Greek words ὅλος and καινός, meaning entirely recent. It has been identified with the current warm period, known as MIS1, given these, a new term, Anthropocene, is specifically proposed and used informally only for the very latest part of modern history involving significant human impact. It is accepted by the International Commission on Stratigraphy that the Holocene started approximately 11,700 years ago, the epoch follows the Pleistocene and the last glacial period. The Holocene can be subdivided into five time intervals, or chronozones, based on climatic fluctuations, Preboreal, Boreal, Atlantic, Subboreal and they find a general correspondence across Eurasia and North America, though the method was once thought to be of no interest. The scheme was defined for Northern Europe, but the changes were claimed to occur more widely. The periods of the include a few of the final pre-Holocene oscillations of the last glacial period. Paleontologists have not defined any faunal stages for the Holocene, if subdivision is necessary, periods of human technological development, such as the Mesolithic, Neolithic, and Bronze Age, are usually used. However, the time periods referenced by these terms vary with the emergence of those technologies in different parts of the world, climatically, the Holocene may be divided evenly into the Hypsithermal and Neoglacial periods, the boundary coincides with the start of the Bronze Age in Europe. According to some scholars, a division, the Anthropocene, has now begun. Continental motions due to plate tectonics are less than a kilometre over a span of only 10,000 years, however, ice melt caused world sea levels to rise about 35 m in the early part of the Holocene. The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea, Holocene marine fossils are known, for example, from Vermont and Michigan. Other than higher-latitude temporary marine incursions associated with depression, Holocene fossils are found primarily in lakebed, floodplain. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely tectonic uplift of non-glacial origin, post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea. The region continues to rise, still causing weak earthquakes across Northern Europe, the equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries. Climate has been stable over the Holocene. It appears that this was influenced by the glacial ice remaining in the Northern Hemisphere until the later date
2.
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
3.
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
4.
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
5.
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
6.
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
7.
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
8.
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
9.
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
10.
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
11.
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
12.
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
13.
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
14.
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
15.
Common box turtle
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The common box turtle is a species of box turtle with six existing subspecies. It is found throughout the eastern United States and Mexico, the box turtle has a distinctive hinged lowered shell that allows it to completely enclose itself. Its upper jaw is long and curved, the turtle is primarily terrestrial and eats a wide variety of plants and animals. The females lay their eggs in the summer, Turtles in the northern part of their range hibernate over the winter. Common box turtle numbers are declining because of loss, roadkill. The species is classified as Vulnerable to threats to its survival by the IUCN Red List, three U. S. states name subspecies of the common box turtle as their official reptile. Terrapene carolina was first described by Linnaeus in 1758 and it is the type species for the Terrapene genus and also has more subspecies than the other three species within that genus. The eastern box turtle subspecies was the one recognized by Linnaeus, the other five subspecies were first classified during the 19th century. In addition, one extinct subspecies T. c. putnamii is distinguished, subspecies Parentheses around the name of an authority indicate that he originally described the subspecies in a genus other than Terrapene. The carapace is brown, often adorned with a pattern of orange or yellow lines, spots. The plastron is dark brown and may be coloured, or show darker blotches or smudges. The common box turtle has a small to moderately sized head, the majority of adult male common box turtles have red irises, while those of the female are yellowish-brown. Males also differ from females by possessing shorter, stockier and more curved claws on their hind feet, the subspecies Terrapene carolina triunguis is particularly distinctive as most males have a bright red head. It is found in Canada in southern Ontario and in Mexico along the Gulf Coast and in the Yucatán Peninsula. The species range is not continuous as the two Mexican subspecies, T. c. mexicana and T. c. yucatana, are separated from the US subspecies by a gap in western Texas. Three of the US subspecies, T. c. carolina, major and T. c. bauri, occur roughly in the areas indicated by their names. T. c. triunguis is found in the central United States, Common box turtles are predominantly terrestrial reptiles that are often seen early in the day, or after rain, when they emerge from the shelter of rotting leaves, logs, or a mammal burrow to forage. These turtles have a varied diet of animal and plant matter, including earthworms, slugs, insects, wild berries
16.
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
17.
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
18.
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
19.
Reptile
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Reptiles are tetrapod animals in the class Reptilia, comprising todays turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of amphibians, is called herpetology. Because some reptiles are more related to birds than they are to other reptiles. For this reason, many scientists prefer to consider the birds part of Reptilia as well. Some early examples include the lizard-like Hylonomus and Casineria, in addition to the living reptiles, there are many diverse groups that are now extinct, in some cases due to mass extinction events. In particular, the K–Pg extinction wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, as well as species of theropods, crocodyliforms. Modern non-avian reptiles inhabit every continent with the exception of Antarctica, several living subgroups are recognized, Testudines, approximately 400 species, Sphenodontia,1 species, Squamata, over 9,600 species, Crocodilia,25 species, and Aves,10,000 species. Reptiles are tetrapod vertebrates, creatures that either have four limbs or, unlike amphibians, reptiles do not have an aquatic larval stage. As amniotes, reptile eggs are surrounded by membranes for protection and transport, many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. In the 18th century, the reptiles were, from the outset of classification, the terms reptile and amphibian were largely interchangeable, reptile being preferred by the French. Josephus Nicolaus Laurenti was the first to use the term Reptilia for an expanded selection of reptiles. Today, the two groups are commonly treated under the same heading as herptiles. He subsequently proposed the names of Sauropsida and Ichthyopsida for the two groups. In 1866, Haeckel demonstrated that vertebrates could be divided based on their strategies, and that reptiles, birds. The terms Sauropsida and Theropsida were used again in 1916 by E. S, Goodrich to distinguish between lizards, birds, and their relatives on the one hand and mammals and their extinct relatives on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, according to Goodrich, both lineages evolved from an earlier stem group, Protosauria in which he included some animals today considered reptile-like amphibians, as well as early reptiles. Watson observed that the first two groups diverged very early in history, so he divided Goodrichs Protosauria between them. He also reinterpreted Sauropsida and Theropsida to exclude birds and mammals, thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia, Squamata, Rhynchocephalia, Crocodilia, thecodonts, non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropterygians
20.
August Batsch
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August Johann Georg Karl Batsch was a German naturalist. He was an authority on mushrooms, and also described new species of ferns, bryophytes. Batsch was born in Jena, Saxe-Weimar to George Lorenz Bratsch and he studied at the city school, and then had private tuition. He showed an aptitude for sciences, and so subsequently studied at the University of Jena, entering in 1772. Batsch was married in 1787 to Amalie Pfaundel and they had three children, Friedrich, George Friedrich Karl, and Karoline. He died in 1802 after a short illness, in 1786, he obtained a further doctorate in medicine, and began to teach natural history at the university the same year. In 1787, he began teaching medicine at the university, in 1792, became Professor of Philosophy. He advised Johann Wolfgang von Goethe on his botanical research, in 1790, Batsch founded a botanical garden in Jena, and the Naturforschende Gesellschaft. Batsch discovered almost 200 new species of mushrooms, including Clitocybe nebularis, Calocera cornea, Paxillus involutus and he was a recognised authority writing two books on the topic, Elenchus Fungorum, which is still highly rated today and Versuch einer Anleitung zur Kenntniss und Geschichte der Pflanzen. Looked into the nature of what we now know to be fungal diseases of plants, other works include Dispositio Generum Plantarum Jenensium Secundum Linnaeum et Familias Naturales, Jena 1786, generally referenced as Dispos. Besondre Geschichte der Insekten, Gewürme und Mineralien on insects, worms, tabula affinitatum regni vegetabilis, quam delineavit, et nunc ulterius adumbratam tradit A. J. G. C. List of mycologists Plate Plate from Elenchus fungorum, text of Elenchus Fungorum University of Jena botanical garden Texts of works available at BHL
21.
Cryptodira
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Cryptodira is a suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira in that they lower their necks and pull the heads straight back into the shells and they include among their species freshwater turtles, snapping turtles, tortoises, soft-shell turtles, and sea turtles. Cryptodires evolved during the Jurassic period, and by the end of the Jurassic had almost completely replaced pleurodires in the lakes and rivers, meanwhile, pleurodires became the dominant freshwater testudines in the Cretaceous to Eocene of Europe, and produced a family of marine species, the Bothremydidae. The Cryptodira suborder has three living superfamilies, the Chelonioidea, Testudinoidea, and Trionychoidea, the families within the Kinosternoidea are now recognized as a paraphyletic assemblage of mostly primitive Trionychoidea, they do not form a natural group. Two circumscriptions of the Cryptodira are commonly found, one is used here, it includes a number of primitive extinct lineages known only from fossils, as well as the Eucryptodira. The alternate concept restricts the use of the term Cryptodira to the crown clade, the Cryptodira as understood here are called Cryptodiramorpha in this view. Under this approach, the pleurodires and cryptodires are not sister taxa, doi,10. 1086/275138 First page image Haaramo, Mikko, Mikkos Phylogeny Archive – Cryptodira. Rhodin, Anders G. J. van Dijk, Peter Paul, Inverson, turtles of the world,2011 update, Annotated checklist of taxonomy, synonymy, distribution and conservation status. Archived from the original on 2012-01-22, rhodin, Anders G. J. van Dijk, Peter Paul, Parham, James F. Turtles of the world,2008 checklist, archived from the original on 2012-04-23
22.
Pleurodira
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The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. In many cases in the nomenclature of animals, ranks such as suborder are considered of little importance apart from nomenclatural or taxonomic reasons, however, this is not the case with the suborders of the turtles. This division represents a very deep evolutionary divide between two different types of turtles. The physical differences between them, although anatomical and largely internal, are significant, and the zoogeographic implications of them are substantial. The Pleurodira are known commonly as the side-necked turtles and the name Pleurodira quite literally translates to side neck. The Pleurodira turtles are restricted to the Southern Hemisphere, largely to Australia, South America, the Pleurodira are identified by the method with which they withdraw their heads into their shells. In these turtles, the neck is bent in the horizontal plane, a larger overhang of the carapace helps to protect the neck, which remains partially exposed after retraction. This differs from the method employed by a cryptodiran, which tucks its head, the different methods of bending the neck require completely different anatomies of the cervical vertebrae. All extant turtles studied so far have eight vertebrae in the neck, in the Pleurodira, these vertebrae are narrow in cross-section and spool-shaped with biconvex centra on one or more of the cervicals. These centra act as a joint, allowing a large degree of sideways movement. Conversely, in the Cryptodira, the bones are wide. The biconvex centra in some of the cryptodiran cervicals allow the neck to fold onto itself in the vertical plane, pleurodirans also differ from cryptodirans in the emarginations of their skulls. Skull emargination provides room and anchorage for the jaw muscles, the connection points and the position of the emarginations relate to different bones of the skull. Another difference is in the arrangement of the bones of the shell, pleurodiran turtles have 13 scutes on the plastron of the shell, whereas cryptodiran turtles only have 12. The extra scute is called the intergular and is at the front of the plastron between the gular scutes, pelomedusid turtles also possess mesoplastra, further differentiaing this group. Podocnemididae Chelidae Dortokidae Eusarkiidae Propleuridae Bothremydidae Pelomedusidae
23.
Meiolaniidae
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Meiolaniidae is an extinct family of large, possibly herbivorous turtles with heavily armored heads and tails known from South America and most of Oceania. A similar form is known from the Miocene Saint Bathans Fauna of New Zealand. The family was thought to have originated in Australia sometime in the Oligocene. Though once believed to be cryptodires, meiolaniids are outside of the Testudines crown-group, several basal non-testudine turtles possibly related to meionaliids are known in both laurasian and gondwanann landmasses in the Cretaceous, such as the Asian Mongolochelys. More recently, Eocene australian species have also been uncovered
24.
Biodiversity
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Biodiversity, a contraction of biological diversity, generally refers to the variety and variability of life on Earth. One of the most widely used definitions defines it in terms of the variability within species and it is a measure of the variety of organisms present in different ecosystems. This can refer to genetic variation, ecosystem variation, or species variation within an area, biome, terrestrial biodiversity tends to be greater near the equator, which seems to be the result of the warm climate and high primary productivity. Biodiversity is not distributed evenly on Earth, and is richest in the tropics and these tropical forest ecosystems cover less than 10 per cent of earths surface, and contain about 90 percent of the worlds species. Marine biodiversity tends to be highest along coasts in the Western Pacific, there are latitudinal gradients in species diversity. Biodiversity generally tends to cluster in hotspots, and has been increasing through time, the number and variety of plants, animals and other organisms that exist is known as biodiversity. It is a component of nature and it ensures the survival of human species by providing food, fuel, shelter, medicines. The richness of biodiversity depends on the conditions and area of the region. All species of plants taken together are known as flora and about 300,000 species of plants are known to date, all species of animals taken together are known as fauna which includes birds, mammals, fish, reptiles, insects, crustaceans, molluscs, etc. Rapid environmental changes typically cause mass extinctions, more than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described, the total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes. In comparison, the mass of the biosphere has been estimated to be as much as 4 TtC. In July 2016, scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor of all living on Earth. The age of the Earth is about 4.54 billion years old, there are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland. More recently, in 2015, remains of life were found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, If life arose relatively quickly on Earth, then it could be common in the universe
25.
Diapsid
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Diapsids are a group of amniote tetrapods that developed two holes in each side of their skulls about 300 million years ago during the late Carboniferous period. The diapsids are extremely diverse, and include all crocodiles, lizards, snakes, tuatara, turtles, although some diapsids have lost either one hole, or both holes, or have a heavily restructured skull, they are still classified as diapsids based on their ancestry. At least 7,925 species of diapsid reptiles exist in environments around the world today, the name Diapsida means two arches, and diapsids are traditionally classified based on their two ancestral skull openings posteriorly above and below the eye. This arrangement allows for the attachment of larger, stronger jaw muscles, a more obscure ancestral characteristic is a relatively long lower arm bone compared to the upper arm bone. Diapsids were originally classified as one of four subclasses of the class Reptilia, all of which were based on the number, the other three subclasses were Synapsida, Anapsida, and Euryapsida. With the advent of phylogenetic nomenclature, this system of classification was heavily modified, today, the synapsids are often not considered true reptiles, while Euryapsida were found to be an unnatural assemblage of diapsids that had lost one of their skull openings. Genetic studies have shown that this is also the case in turtles, in phylogenetic systems, birds are also considered to be members of this group. Some modern studies of relationships have preferred to use the name diapsid to refer to the crown group of all modern diapsid reptiles. However, many researchers have favored a more traditional definition that includes the prehistoric araeoscelidians. In 1991, Laurin defined Diapsida as a clade, the most recent common ancestor of araeoscelidians, lepidosaurs, and archosaurs, below is a cladogram showing the relations of the major groups of diapsids. Cladogram after Bickelmann et al.2009 and Reisz et al,2011, Vertebrate paleontology Synapsida Anapsida Euryapsida Data related to Diapsid at Wikispecies Diapsida. Michel Laurin and Jacques A. Gauthier, Diapsida Cladogram at Mikkos Phylogeny Archive
26.
Order (biology)
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In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, an immediately higher rank, superorder, may be added directly above order, while suborder would be a lower rank. A taxonomic unit, a taxon, in that rank, in that case the plural is orders. Example, The Juglans and Hickory trees belong to the family Juglandaceae, what does and does not belong to each order is determined by a taxonomist, as is whether a particular order should be recognized at all. Often there is no agreement, with different taxonomists each taking a different position. There are no rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognised only rarely, for some groups of organisms, consistent suffixes are used to denote that the rank is an order. The Latin suffix -formes meaning having the form of is used for the name of orders of birds and fishes. The suffix -ales is for the name of orders of plants, fungi, for some clades covered by the International Code of Zoological Nomenclature, a number of additional classifications are sometimes used, although not all of these are officially recognised. In their 1997 classification of mammals, McKenna and Bell used two levels between superorder and order, grandorder and mirorder. Michael Novacek inserted them at the same position, michael Benton inserted them between superorder and magnorder instead. This position was adopted by Systema Naturae 2000 and others, in botany, the ranks of subclass and suborder are secondary ranks pre-defined as respectively above and below the rank of order. Any number of further ranks can be used as long as they are clearly defined, the superorder rank is commonly used, with the ending -anae that was initiated by Armen Takhtajans publications from 1966 onwards. Carl Linnaeus was the first to apply it consistently to the division of all three kingdoms of nature in his Systema Naturae, for plants, Linnaeus orders in the Systema Naturae and the Species Plantarum were strictly artificial, introduced to subdivide the artificial classes into more comprehensible smaller groups. In French botanical publications, from Michel Adansons Familles naturelles des plantes and until the end of the 19th century, some of the plant families still retain the names of Linnaean natural orders or even the names of pre-Linnaean natural groups recognised by Linnaeus as orders in his natural classification. Such names are known as family names. In zoology, the Linnaean orders were used more consistently and that is, the orders in the zoology part of the Systema Naturae refer to natural groups. Some of his names are still in use
27.
Cartilage
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It is not as hard and rigid as bone, but it is stiffer and less flexible than muscle. Because of its rigidity, cartilage often serves the purpose of holding tubes open in the body, cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in relative amounts of collagen and proteoglycan. Cartilage does not contain blood vessels or nerves, nutrition is supplied to the chondrocytes by diffusion. The compression of the cartilage or flexion of the elastic cartilage generates fluid flow. Compared to other tissues, cartilage has a very slow turnover of its extracellular matrix. In embryogenesis, the system is derived from the mesoderm germ layer. Following the initial chondrification that occurs during embryogenesis, cartilage growth consists mostly of the maturing of immature cartilage to a mature state. The division of cells within cartilage occurs very slowly, and thus growth in cartilage is not based on an increase in size or mass of the cartilage itself. The articular cartilage function is dependent on the composition of the extracellular matrix. The ECM consists mainly of proteoglycan and collagens, the main proteoglycan in cartilage is aggrecan, which, as its name suggests, forms large aggregates with hyaluronan. These aggregates are negatively charged and hold water in the tissue, the collagen, mostly collagen type II, constrains the proteoglycans. The ECM responds to tensile and compressive forces that are experienced by the cartilage, cartilage growth thus refers to the matrix deposition, but can also refer to both the growth and remodeling of the extracellular matrix. Due to the stress on the patellofemoral joint during resisted knee flexion. The mechanical properties of articular cartilage in load bearing joints such as knee and hip have been studied extensively at macro, micro and these mechanical properties include the response of cartilage in frictional, compressive, shear and tensile loading. Cartilage is resilient and displays viscoelastic properties, lubricin, a glycoprotein abundant in cartilage and synovial fluid, plays a major role in bio-lubrication and wear protection of cartilage. Cartilage has limited capabilities, Because chondrocytes are bound in lacunae. Therefore, cartilage damage is difficult to heal, also, because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Damaged hyaline cartilage is replaced by fibrocartilage scar tissue
28.
Exoskeleton
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An exoskeleton is the external skeleton that supports and protects an animals body, in contrast to the internal skeleton of, for example, a human. In usage, some of the kinds of exoskeletons are known as shells. Examples of animals with exoskeletons include insects such as grasshoppers and cockroaches, the shells of certain sponges and the various groups of shelled molluscs, including those of snails, clams, tusk shells, chitons and nautilus, are also exoskeletons. Some animals, such as the tortoise, have both an endoskeleton and an exoskeleton, exoskeletons have a role in defense from pests and predators, support, and in providing an attachment framework for musculature. Exoskeletons contain chitin, the addition of calcium carbonate makes them harder and stronger, ingrowths of the arthropod exoskeleton known as apodemes serve as attachment sites for muscles. These structures are composed of chitin, and are six times as strong. Similar to tendons, apodemes can stretch to store energy for jumping. Many different species produce exoskeletons, which are composed of a range of materials, bone, cartilage, or dentine is used in the Ostracoderm fish and turtles. Chitin forms the exoskeleton in arthropods including insects, arachnids such as spiders, crustaceans such as crabs and lobsters, calcium carbonates constitute the shells of molluscs, brachiopods, and some tube-building polychaete worms. Silica forms the exoskeleton in the microscopic diatoms and radiolaria, one species of mollusc, the scaly-foot gastropod, even makes use of the iron sulfides greigite and pyrite. Some organisms, such as some foraminifera, agglutinate exoskeletons by sticking grains of sand, contrary to a common misconception, echinoderms do not possess an exoskeleton, as their test is always contained within a layer of living tissue. Exoskeletons have evolved many times,18 lineages evolved calcified exoskeletons alone. Further, other lineages have produced tough outer coatings analogous to an exoskeleton and this coating is constructed from bone in the armadillo, and hair in the pangolin. The armor of reptiles like turtles and Ankylosaurs is constructed of bone, crocodiles have bony scutes, since exoskeletons are rigid, they present some limits to growth. Organisms with open shells can grow by adding new material to the aperture of their shell, as is the case in snails, bivalves, a true exoskeleton, like that found in arthropods, must be shed when it is outgrown. A new exoskeleton is produced beneath the old one, as the old one is shed, the new skeleton is soft and pliable. The animal will pump itself up to expand the new shell to maximal size, when the shell has set, the empty space inside the new skeleton can be filled up as the animal eats. Failure to shed the exoskeleton once outgrown can result in the animal being suffocated within its own shell and this is the mechanism behind some insect pesticides, such as Azadirachtin
29.
Rib
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In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most tetrapods, ribs surround the chest, enabling the lungs to expand and they serve to protect the lungs, heart, and other internal organs of the thorax. In some animals, especially snakes, ribs may provide support, the first seven sets of ribs, known as true ribs also known as vertebrosternal ribs, are directly attached to the sternum through the costal cartilage. Rib 1 is unique and harder to distinguish than other ribs and it is a short, flat, C-shaped bone. The vertebral attachment can be found just below the neck and the majority of this bone can be found above the level of the clavicle, Ribs 2 through 7 have a more traditional appearance and become longer and less curved as they progress downwards. The following five sets are known as ribs, three of these sharing a common cartilaginous connection to the sternum, while the last two are termed floating ribs or vertebral ribs. They are attached to the only, and not to the sternum or cartilage coming off of the sternum. Some people lack one of the two pairs of floating ribs, while others have a third pair, in general, human ribs increase in length from ribs 1 through 7 and decrease in length again through rib 12. Along with this change in size, the ribs become progressively oblique from ribs 1 through 9, the ribcage is separated from the lower abdomen by the thoracic diaphragm which controls breathing. When the diaphragm contracts, the cavity is expanded, reducing intra-thoracic pressure. In fish, there are two sets of ribs attached to the vertebral column. One set, the ribs, are found in the dividing septum between the upper and lower parts of the main muscle segments, projecting roughly sideways from the vertebral column. The second set, of ventral ribs arise from the vertebral column just below the dorsal ribs, not all species possess both types of rib, with the dorsal ribs being most commonly absent. Sharks, for example, have no ribs, and only very short ventral ribs. In some teleosts, there may be additional rib-like bones within the muscle mass, tetrapods, however, only ever have a single set of ribs which are probably homologous with the dorsal ribs of fishes. In the early tetrapods, every vertebra bore a pair of ribs, the sacral ribs were stout and short, since they formed part of the pelvis, connecting the backbone to the hip bones. In most subsequent forms, many of these early ribs have been lost, frogs typically have no ribs, aside from a sacral pair, which form part of the pelvis. In birds, ribs are present as distinct bones only on the thoracic region, the thoracic ribs of birds possess a wide projection to the rear, this uncinate process is an attachment for the shoulder muscles
30.
Shield
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A shield is a piece of personal armour held in the hand or mounted on the wrist or forearm. Shields are used to specific attacks, whether from close-ranged weaponry or projectiles such as arrows, by means of active blocks. Shields vary greatly in size, ranging from large panels that protect the whole body to small models that were intended for hand-to-hand-combat use. In prehistory and during the era of the earliest civilisations, shields were made of wood, animal hide and they were carried by foot soldiers, knights and cavalry. Depending on time and place, shields could be round, oval, square, rectangular, triangular, sometimes they took on the form of kites or flatirons, or had rounded tops on a rectangular base with perhaps an eye-hole, to look through when used with combat. The shield was held by a grip or by straps that went over or around the users arm. Often shields were decorated with a pattern or an animal representation to show their army or clan. These designs developed into systematized heraldic devices during the High Middle Ages for purposes of battlefield identification, even after the introduction of gunpowder and firearms to the battlefield, shields continued to be used by certain groups. In the 20th and 21st century, shields have been used by military and police units that specialize in anti-terrorist actions, hostage rescue, riot control and siege-breaking. The modern term usually refers to a device that is held in the hand or attached to the arm, Shields are also sometimes mounted on vehicle-mounted weapons to protect the operator. The oldest form of shield was a device designed to block attacks by hand weapons, such as swords, axes and maces, or ranged weapons like sling-stones. Shields have varied greatly in construction time and place. Sometimes shields were made of metal, but wood or animal hide construction was more common, wicker. Many surviving examples of metal shields are generally felt to be rather than practical, for example the Yetholm-type shields of the Bronze Age. Lightly armored warriors relying on speed and surprise would generally carry light shields that were small or thin. Heavy troops might be equipped with robust shields that could cover most of the body, many had a strap called a guige that allowed them to be slung over the users back when not in use or on horseback. During the 14th–13th century BC, the Sards or Shardana, working as mercenaries for the Egyptian pharaoh Ramses II, the Mycenaean Greeks used two types of shields, the figure-of-eight shield and a rectangular tower shield. These shields were made primarily from a frame and then reinforced with leather
31.
Extinction
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In biology and ecology, extinction is the end of an organism or of a group of organisms, normally a species. The moment of extinction is considered to be the death of the last individual of the species, although the capacity to breed. Because a species range may be very large, determining this moment is difficult. This difficulty leads to such as Lazarus taxa, where a species presumed extinct abruptly reappears after a period of apparent absence. More than 99 percent of all species, amounting to five billion species. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described, the relationship between animals and their ecological niches has been firmly established. Mass extinctions are relatively rare events, however, isolated extinctions are quite common, only recently have extinctions been recorded and scientists have become alarmed at the current high rate of extinctions. Most species that become extinct are never scientifically documented, some scientists estimate that up to half of presently existing plant and animal species may become extinct by 2100. A dagger symbol next to a name is often used to indicate its extinction. A species is extinct when the last existing member dies, Extinction therefore becomes a certainty when there are no surviving individuals that can reproduce and create a new generation. Pinpointing the extinction of a species requires a definition of that species. If it is to be declared extinct, the species in question must be distinguishable from any ancestor or daughter species. Extinction of a plays a key role in the punctuated equilibrium hypothesis of Stephen Jay Gould. In ecology, extinction is often used informally to refer to local extinction, in which a species ceases to exist in the area of study. This phenomenon is known as extirpation. Local extinctions may be followed by a replacement of the species taken from other locations, species which are not extinct are termed extant. Those that are extant but threatened by extinction are referred to as threatened or endangered species, currently an important aspect of extinction is human attempts to preserve critically endangered species
32.
Snake
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Snakes are elongated, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales, many species of snakes have skulls with several more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads with their highly mobile jaws. To accommodate their bodies, snakes paired organs appear one in front of the other instead of side by side. Some species retain a pelvic girdle with a pair of claws on either side of the cloaca. Additionally, sea snakes are widespread throughout the Indian and Pacific Oceans, more than 20 families are currently recognized, comprising about 500 genera and about 3,400 species. They range in size from the tiny,10.4 cm -long thread snake to the reticulated python of 6.95 meters in length, the fossil species Titanoboa cerrejonensis was 12.8 meters long. Snakes are thought to have evolved from either burrowing or aquatic lizards, perhaps during the Jurassic period, the diversity of modern snakes appeared during the Paleocene period. The oldest preserved descriptions of snakes can be found in the Brooklyn Papyrus, most species are nonvenomous and those that have venom use it primarily to kill and subdue prey rather than for self-defense. Some possess venom potent enough to cause injury or death to humans. Nonvenomous snakes either swallow prey alive or kill by constriction, the word ousted adder, as adder went on to narrow in meaning, though in Old English næddre was the general word for snake. The other term, serpent, is from French, ultimately from Indo-European *serp-, the fossil record of snakes is relatively poor because snake skeletons are typically small and fragile making fossilization uncommon. Fossils readily identifiable as snakes first appear in the record during the Cretaceous period. The earliest known snake fossils come from the marine simoliophiids. Based on comparative anatomy, there is consensus that snakes descended from lizards, pythons and boas—primitive groups among modern snakes—have vestigial hind limbs, tiny, clawed digits known as anal spurs, which are used to grasp during mating. The families Leptotyphlopidae and Typhlopidae also possess remnants of the pelvic girdle, front limbs are nonexistent in all known snakes. This is caused by the evolution of Hox genes, controlling limb morphogenesis, the axial skeleton of the snakes’ common ancestor, like most other tetrapods, had regional specializations consisting of cervical, thoracic, lumbar, sacral, and caudal vertebrae. Early in snake evolution, the Hox gene expression in the axial skeleton responsible for the development of the thorax became dominant, as a result, the vertebrae anterior to the hindlimb buds all have the same thoracic-like identity. In other words, most of a skeleton is an extremely extended thorax
33.
Crocodilia
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The Crocodilia is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 83.5 million years ago in the Late Cretaceous period and are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the total group, the clade Pseudosuchia, appeared about 250 million years ago in the Early Triassic period. The order Crocodilia includes the true crocodiles, the alligators and caimans, although the term crocodiles is sometimes used to refer to all of these, crocodilians is a less ambiguous vernacular term for members of this group. Large, solidly built, lizard-like reptiles, crocodilians have flattened snouts, laterally compressed tails, and eyes, ears. They swim well and can move on land in a high walk and their skin is thick and covered in non-overlapping scales. They have conical, peg-like teeth and a powerful bite and they have a four-chambered heart and, somewhat like birds, a unidirectional looping system of airflow within the lungs, but like other non-avian reptiles they are ectotherms. Crocodilians are found mainly in lowlands in the tropics, but alligators also live in the southeastern United States, Crocodilians are typically solitary and territorial, though cooperative feeding does occur. During breeding, dominant males try to monopolise available females, females lay eggs in holes or in mounds and, unlike most other reptiles, care for their hatched young. Eight species of crocodilians are known to have attacked humans, the largest number of attacks comes from the Nile crocodile. Artistic and literary representations of crocodilians have appeared in cultures around the world since at least Ancient Egypt. Crocodilia and Crocodylia have been used interchangeably for decades starting with Schmidts redescription of the group from the defunct term Loricata. Schmidt used the older term Crocodilia, based on Owens original name for the group, shortly after, Wermuth opted for Crocodylia as the proper name for this redescribed group, basing it on the type genus Crocodylus. Dundee—in a revision of many reptilian and amphibian names—argued strongly for Crocodylia to be the spelling for the group, however, it was not until the advent of cladistics and phylogenetic nomenclature that a more solid justification for assuming one spelling over the other was proposed. Prior to 2003, Crocodilia/Crocodylia was a group that encompassed the modern-day animals as well as their distant relatives now in the larger groups called Crocodylomorpha. Under its current definition Crocodylia is restricted to only the most recent ancestor of todays modern-day crocodilians and this distinction is more important for paleontologists studying crocodilian evolution. As such, the alternate spellings Crocodilia and Crocodylia are still used interchangeably in the neontological literature, Crocodilia appears to be a Latinizing of the Greek κροκόδειλος, which means both lizard and Nile crocodile. Crocodylia, as coined by Wermuth, in regards to the genus Crocodylus appears to be derived from the ancient Greek κρόκη —meaning shingle or pebble—and δρîλος or δρεîλος for worm, the name may refer to the animals habit of basking on the pebbled shores of the Nile
34.
Species
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In biology, a species is the basic unit of biological classification and a taxonomic rank. A species is defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is problematic, for example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Other ways of defining species include similarity of DNA, morphology, all species are given a two-part name, a binomial. The first part of a binomial is the genus to which the species belongs, the second part is called the specific name or the specific epithet. For example, Boa constrictor is one of four species of the Boa genus, Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped that species could evolve given sufficient time, Charles Darwins 1859 book The Origin of Species explained how species could arise by natural selection. Genes can sometimes be exchanged between species by horizontal transfer, and species may become extinct for a variety of reasons. In his biology, Aristotle used the term γένος to mean a kind, such as a bird or fish, a kind was distinguished by its attributes, for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance, when observers in the Early Modern period began to develop systems of organization for living things, they placed each kind of animal or plant into a context. Many of these early delineation schemes would now be considered whimsical, animals likewise that differ specifically preserve their distinct species permanently, one species never springs from the seed of another nor vice versa. In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics and he established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships. At the time, however, it was widely believed that there was no organic connection between species, no matter how similar they appeared. However, whether or not it was supposed to be fixed, by the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time, in 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals and this required a new definition of species. Darwin concluded that species are what appear to be, ideas
35.
Endangered species
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An endangered species is a species which has been categorized as likely to become extinct. In 2012, the IUCN Red List featured 3079 animal and 2655 plant species as endangered worldwide, the figures for 1998 were, respectively,1102 and 1197. Many nations have laws that protect conservation-reliant species, for example, population numbers, trends and species conservation status can be found in the lists of organisms by population. The conservation status of a species indicates the likelihood that it will become extinct, the IUCN Red List of Threatened Species is the best-known worldwide conservation status listing and ranking system. Over 40% of the species are estimated to be at risk of extinction. Internationally,199 countries have signed an accord to create Biodiversity Action Plans that will protect endangered, in the United States, such plans are usually called Species Recovery Plans. Those species of Near Threatened and Least Concern status have been assessed and found to have relatively robust and healthy populations, though these may be in decline. The IUCN categories, with examples of animals classified by them, include, Extinct Extinct in the wild Captive individuals survive, critically endangered Faces an extremely high risk of extinction in the immediate future. Endangered Faces a high risk of extinction in the near future, vulnerable Faces a high risk of endangerment in the medium term. Near-threatened May be considered threatened in the near future, Least concern No immediate threat to species survival. A population size reduction of ≥ 50%, projected or suspected to be met within the next 10 years or three generations, whichever is the longer, based on any of to under A1. E) Quantitative analysis showing the probability of extinction in the wild is at least 20% within 20 years or five generations, there is data from the United States that shows a correlation between human populations and threatened and endangered species. Under the Endangered Species Act in the United States, species may be listed as endangered or threatened, the Salt Creek tiger beetle is an example of an endangered subspecies protected under the ESA. Some endangered species laws are controversial, also lobbying from hunters and various industries like the petroleum industry, construction industry, and logging, has been an obstacle in establishing endangered species laws. The Bush administration lifted a policy that required federal officials to consult an expert before taking actions that could damage endangered species. Under the Obama administration, this policy has been reinstated, being listed as an endangered species can have negative effect since it could make a species more desirable for collectors and poachers. This effect is potentially reducible, such as in China where commercially farmed turtles may be reducing some of the pressure to poach endangered species. Another problem with the species is its effect of inciting the use of the shoot, shovel
36.
Ectotherm
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An ectotherm, is an organism in which internal physiological sources of heat are of relatively small or quite negligible importance in controlling body temperature. Such organisms rely on environmental heat sources, which permit them to operate at very economical metabolic rates, colloquially, some refer to these organisms as cold blooded though such a term is not technically correct, as the blood temperature of the organism varies with ambient environmental temperature. Some of these live in environments where temperatures are practically constant. In contrast to ectotherms, endotherms rely largely, even predominantly, in ectotherms, fluctuating ambient temperatures may affect the body temperature. Such variation in temperature is called poikilothermy, though the concept is not widely satisfactory. Ectotherms can also display the features of homeothermy, especially within aquatic organisms, various patterns of behavior enable certain ectotherms to regulate body temperature to a useful extent. To warm up, reptiles and many insects find sunny places and adopt positions that maximise their exposure, in cold weather, honey bees huddle together to retain heat. Butterflies and moths may orient their wings to maximize exposure to radiation in order to build up heat before take-off. Gregarious caterpillars, such as the Forest Tent caterpillar, benefit from basking in groups for thermoregulation. Many flying insects, such as bees and bumble bees, also raise their internal temperatures endothermally prior to flight. Such endothermal activity is an example of the difficulty of consistent application of such as poikilothermy and homiothermy. In addition to adaptations, physiological adaptations help ectotherms regulate temperature. The skin of bullfrogs secretes more mucus when it is hot, during periods of cold, some ectotherms enter a state of torpor, in which their metabolism slows or, in some cases, such as the wood frog, effectively stops. The torpor might last overnight or last for a season, or even for years, ectotherms rely largely on external heat sources such as sunlight to achieve their optimal body temperature for various bodily activities. Accordingly, they depend on ambient conditions to reach operational body temperatures, also, as a rule, ectotherms have lower metabolic rates than endotherms at a given body mass. As a consequence, endotherms generally rely on food consumption. Such requirements may limit the capacity of a given environment for endotherms as compared to its carrying capacity for ectotherms. Because ectotherms depend on conditions for body temperature regulation, as a rule, they are more sluggish at night
37.
Poikilotherm
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A poikilotherm is an organism whose internal temperature varies considerably. It is the opposite of a homeotherm, an organism which maintains thermal homeostasis, usually the variation is a consequence of variation in the ambient environmental temperature. However some ectotherms remain in temperature-constant environments to the point that they are able to maintain a constant internal temperature. It is this distinction that often makes the term poikilotherm more useful than the vernacular cold-blooded, poikilothermic animals include types of vertebrate animals, specifically fish, amphibians, and reptiles, as well as a large number of invertebrate animals. The naked mole-rat is the only mammal that is thought to be poikilothermic. The term derives from Greek poikilos, meaning varied, ultimately from thousand-making and thermos, for an important chemical reaction, poikilotherms may have four to ten enzyme systems that operate at different temperatures. As a result, poikilotherms often have larger, more complex genomes than homeotherms in the ecological niche. Frogs are an example of this effect, though their complex development is likely more important. The metabolism of poikilotherms favors strategies such as sit-and-wait hunting over chasing prey for animals with high movement cost. As they do not use their metabolisms to heat or cool themselves, for the same body weight, poikilotherms need only 5 to 10% of the energy of homeotherms. Lizards and snakes bask in the sun in the morning and late evening. The eggs of the bumblebee are unable to regulate heat. The bumblebee generates heat by shivering flight muscles even though they are not flying, termite mounds are usually oriented in a north-south direction so that they absorb as much heat as possible around dawn and dusk and minimise heat absorption around noon. Tuna are able to warm their bodies through a heat exchange mechanism called the rete mirabile, which helps keep heat inside the body. They also have their swimming muscles near the center of their bodies instead of near the surface, gigantothermy means using a low ratio of surface area to volume to minimise heat loss, such as in sea turtles. Camels, although they are homeotherms, thermoregulate using a method termed temperature cycling to conserve energy, in hot deserts, they allow their body temperature to rise during the day and fall during the night, adjusting their body temperature to cycle over approximately 6°C. It is comparatively easy for a poikilotherm to accumulate enough energy to reproduce, poikilotherms at the same trophic level often have much shorter generations than homeotherms, weeks rather than years. Such applies even to animals with similar ecological roles such as cats and this difference in energy requirement also means that a given food source can support a greater density of poikilothermic animals than homeothermic animals
38.
Leatherback sea turtle
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The leatherback sea turtle, sometimes called the lute turtle or leathery turtle, is the largest of all living turtles and is the fourth-heaviest modern reptile behind three crocodilians. It is the living species in the genus Dermochelys and family Dermochelyidae. It can easily be differentiated from other sea turtles by its lack of a bony shell. Instead, its carapace is covered by skin and oily flesh, Dermochelys is the only extant genus of the family Dermochelyidae. D. coriacea is the species in genus Dermochelys. The genus, in turn, contains the only extant member of the family Dermochelyidae, domenico Agostino Vandelli named the species first in 1761 as Testudo coriacea after an animal captured at Ostia and donated to the University of Padua by Pope Clement XIII. In 1816, French zoologist Henri Blainville coined the term Dermochelys, the leatherback was then reclassified as Dermochelys coriacea. In 1843, the zoologist Leopold Fitzinger put the genus in its own family, in 1884, the American naturalist Samuel Garman described the species as Sphargis coriacea schlegelii. The two were united in D. coriacea, with each given subspecies status as D. c. coriacea. The subspecies were later labeled invalid synonyms of D. coriacea, the turtles common name comes from the leathery texture and appearance of its carapace. Older names include leathery turtle and trunk turtle, relatives of modern leatherback turtles have existed in some form since the first true sea turtles evolved over 110 million years ago during the Cretaceous period. The dermochelyids are relatives of the family Cheloniidae, which contains the six extant sea turtle species. However, their sister taxon is the extinct family Protostegidae that included species that did not have a hard carapace. Leatherback turtles have the most hydrodynamic body design of any sea turtle, with a large, a large pair of front flippers powers the turtles through the water. Like other sea turtles, the leatherback has flattened fore limbs adapted for swimming in the open ocean, claws are absent from both pairs of flippers. The leatherbacks flippers are the largest in proportion to its body among extant sea turtles, Leatherbacks front flippers can grow up to 2.7 m in large specimens, the largest flippers of any sea turtle. The leatherback has several characteristics that distinguish it from sea turtles. Its most notable feature is the lack of a bony carapace, instead of scutes, it has thick, leathery skin with embedded minuscule osteoderms
39.
Amniote
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Amniotes are a clade of tetrapod vertebrates comprising the reptiles, birds, and mammals that lay their eggs on land or retain the fertilized egg within the mother. They are distinguished from the anamniotes, which lay their eggs in water. Older sources, particularly prior to the 20th century, may refer to amniotes as higher vertebrates and anamniotes as lower vertebrates, based on the discredited idea of the Great Chain of Being. Amniotes are tetrapods that are characterised by having an egg equipped with an amnion, amniotes include synapsids and sauropsids, as well as their ancestors, back to amphibians. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes, in eutherian mammals, these membranes include the amniotic sac that surrounds the fetus. These embryonic membranes and the lack of a larval stage distinguish amniotes from tetrapod amphibians, the first amniotes, referred to as basal amniotes, resembled small lizards and evolved from the amphibian reptiliomorphs about 312 million years ago, in the Carboniferous geologic period. Their eggs could survive out of the water, allowing amniotes to branch out into drier environments, the eggs could also breathe and cope with wastes, allowing the eggs and the amniotes themselves to evolve into larger forms. From this point the amniotes spread around the globe, eventually to become the dominant land vertebrates, very early in the evolutionary history of amniotes, basal amniotes diverged into two main lines, the synapsids and the sauropsids, both of which persist into the modern era. Amniotes can be characterized in part by embryonic development that includes the formation of several extensive membranes, the amnion, chorion, and allantois. Amniotes develop directly into a form with limbs and a thick stratified epithelium. In amniotes, the transition from a two-layered periderm to cornified epithelium is triggered by thyroid hormone during embryonic development and their kidneys and large intestines are also well-suited to water retention. Most mammals do not lay eggs, but corresponding structures may be found inside the placenta, the ancestors of true amniotes, such as Casineria kiddi, which lived about 340 million years ago, evolved from amphibian reptiliomorphs and resembled small lizards. At the late Devonian mass extinction 360 million years ago, all known tetrapods were essentially aquatic, indeed, many modern day amniotes are dependent on moisture to keep their eggs from desiccating. Although some modern amphibians lay eggs on land, they all lack advanced traits like an amnion, the amniotic egg was formed through a series of evolutionary steps. This allowed the egg to both its size and the rate of gas exchange, permitting a larger, metabolically more active embryo to reach full development before hatching. Further development of the design, like extraembryonic membranes and a shell, were not essential. The only way for the eggs to increase in size would be to develop new internal structures specialized for respiration, as this happened, it would also affect how much the juveniles could grow before they reached adulthood. In fish and amphibians there is one inner membrane, the embryonic membrane
40.
Turtle
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Turtles are reptiles of the order Testudines characterised by a special bony or cartilaginous shell developed from their ribs and acting as a shield. Turtle may refer to the order as a whole or to fresh-water, the order Testudines includes both extant and extinct species. The earliest known members of this date from 157 million years ago, making turtles one of the oldest reptile groups. Of the 327 known species alive today, some are highly endangered, turtles are ectotherms—animals commonly called cold-blooded—meaning that their internal temperature varies according to the ambient environment. However, because of their metabolic rate, leatherback sea turtles have a body temperature that is noticeably higher than that of the surrounding water. Turtles are classified as amniotes, along with reptiles, birds. Like other amniotes, turtles breathe air and do not lay eggs underwater, Chelonia is based on the Greek word χελώνη chelone tortoise, turtle, also denoting armor or interlocking shields, testudines, on the other hand, is based on the Latin word testudo tortoise. Turtle may either refer to the order as a whole, or to particular turtles that make up a form taxon that is not monophyletic, the meaning of the word turtle differs from region to region. In North America, all chelonians are commonly called turtles, including terrapins, in Great Britain, the word turtle is used for sea-dwelling species, but not for tortoises. The term tortoise usually refers to any land-dwelling, non-swimming chelonian, most land-dwelling chelonians are in the Testudinidae family, only one of the 14 extant turtle families. Terrapin is used to describe several species of small, edible, hard-shell turtles, typically found in brackish waters. Some languages do not have this distinction, as all of these are referred to by the same name, for example, in Spanish, the word tortuga is used for turtles, tortoises, and terrapins. A sea-dwelling turtle is tortuga marina, a freshwater species tortuga de río, the largest living chelonian is the leatherback sea turtle, which reaches a shell length of 200 cm and can reach a weight of over 900 kg. Freshwater turtles are generally smaller, but with the largest species, the Asian softshell turtle Pelochelys cantorii, a few individuals have been reported up to 200 cm. This dwarfs even the better-known alligator snapping turtle, the largest chelonian in North America and they became extinct at the same time as the appearance of man, and it is assumed humans hunted them for food. The only surviving giant tortoises are on the Seychelles and Galápagos Islands and can grow to over 130 cm in length, the largest ever chelonian was Archelon ischyros, a Late Cretaceous sea turtle known to have been up to 4.6 m long. The smallest turtle is the speckled padloper tortoise of South Africa and it measures no more than 8 cm in length and weighs about 140 g. Two other species of turtles are the American mud turtles
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Green sea turtle
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The green sea turtle, also known as the green turtle, black turtle, or Pacific green turtle, is a large sea turtle of the family Cheloniidae. It is the species in the genus Chelonia. Its range extends throughout tropical and subtropical seas around the world, the common name comes from the usually green fat found beneath its carapace, these turtles shells are olive to black. This sea turtles dorsoventrally flattened body is covered by a large, teardrop-shaped carapace, it has a pair of large and it is usually lightly colored, although in the eastern Pacific populations parts of the carapace can be almost black. Unlike other members of its family, such as the sea turtle. The adults usually inhabit shallow lagoons, feeding mostly on various species of seagrasses, the turtles bite off the tips of the blades of seagrass, which keeps the grass healthy. Like other sea turtles, green sea turtles migrate long distances between feeding grounds and hatching beaches, many islands worldwide are known as Turtle Island due to green sea turtles nesting on their beaches. Females crawl out on beaches, dig nests and lay eggs during the night, later, hatchlings emerge and scramble into the water. Those that reach maturity may live to 80 years in the wild, C. mydas is listed as endangered by the IUCN and CITES and is protected from exploitation in most countries. It is illegal to collect, harm, or kill them, in addition, many countries have laws and ordinances to protect nesting areas. However, turtles are still in danger due to human activity, in some countries, turtles and their eggs are hunted for food. Pollution indirectly harms turtles at both population and individual scales, many turtles die after being caught in fishing nets. Also, real estate development often causes habitat loss by eliminating nesting beaches, the green sea turtle is a member of the tribe Chelonini. A1993 study clarified the status of genus Chelonia with respect to the marine turtles. The carnivorous Eretmochelys, Caretta and Lepidochelys were assigned to the tribe Carettini, herbivorous Chelonia warranted their status as a genus, while Natator was further removed from the other genera than previously believed. The species was described by Linnaeus in 1758 as Testudo mydas. In 1868, Marie Firmin Bocourt named a species of sea turtle Chelonia agassizii. This species was referred to as the sea turtle
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African spurred tortoise
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The African spurred tortoise, also called the sulcata tortoise, is a species of tortoise, which inhabits the southern edge of the Sahara desert, in northern Africa. It is the third-largest species of tortoise in the world, the largest species of tortoise. Its specific name sulcata is from the Latin word sulcus meaning furrow, burrows may average 30 inches in depth, some dig tunnel systems extending 10 feet or more underground. C. sulcata is the third-largest species of tortoise in the world after the Galapagos tortoise, and Aldabra giant tortoise, adults can reach 83 cm and can weigh 105 kg. They grow from hatchling size very quickly, reaching 6-10 in within the first few years of their lives, the lifespan of an African spurred tortoise is about 50–150 years, though they can live much longer. Primarily, their diets consist of types of grasses and plants, high in fiber. Flowers and other plants including cactus pads can be consumed, feeding of fruit should be avoided. Due to their reputation for having a pleasant temperament, sulcata tortoises are kept as pets. They require large enclosures, temperatures above 60 °F, and bedding composed of grasses or grass-based hay, due to their high dietary fiber needs, grasses form a minimum of 75% of their food intake. To remain healthy, they require sufficient calcium for bone and shell development, low protein, whereas wild tortoises obtain enough calcium from the soil, pets generally require calcium supplements. Young sulcatas grow quickly and can double in each year during the first three years. Many wet vegetables cause health problems in large quantities but prickly pear cactus pads, hibiscus leaves, hay from various grasses, some common garden plants, such as azaleas, are toxic to tortoises. Lack of calcium combined with high protein contributes to shell malformations, sulcatas are voracious and sometimes overeat. Some tortoises take in excessive protein by eating caterpillars and snails, per CITES, a zero annual export quota has been established for C. sulcata for specimens removed from the wild and traded for primarily commercial purposes. Due to excessive captive breeding and removal from the wild, many centers are full. Copulation takes place right after the season, during the months from September through November. Males combat each other for breeding rights with the females and are vocal during copulation, sixty days after mating, the female begins to roam looking for suitable nesting sites. For five to fifteen days, four or five nests may be excavated before she selects the perfect location in which the eggs will be laid, loose soil is kicked out of the depression, and the female may frequently urinate into the depression
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Red-eared slider
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The red-eared slider, also known as the red-eared terrapin, is a semiaquatic turtle belonging to the family Emydidae. It is a subspecies of the pond slider and it is the most popular pet turtle in the United States and is also popular as a pet in the rest of the world. It has, therefore, become the most commonly traded turtle in the world, the red-eared slider is included in the list of the worlds 100 most invasive species published by the IUCN. Red-eared sliders get their name from the red stripe around their ears. The slider in their name comes from their ability to slide off rocks and logs and this species was previously known as Troosts turtle in honor of an American herpetologist, Trachemys scripta troostii is now the scientific name for another subspecies, the Cumberland slider. The red-eared slider belongs to the order Testudines, which contains about 250 turtle species and it is a subspecies of Trachemys scripta. They were previously classified under the name Chrysemys scripta elegans, the species Trachemys scripta contains three subspecies, T. s. elegans, T. s. scripta, and T. s. troostii. The carapace of this species can reach more than 40 cm in length, the females of the species are usually larger than the males. They typically live between 20 and 30 years, although individuals have lived for more than 40 years. Their life expectancy is shorter when they are kept in captivity, the quality of their living environment has a strong influence on their lifespans and well being. These turtles are poikilotherms, meaning they are unable to regulate their body temperatures independently, for this reason, they need to sunbathe frequently to warm themselves and maintain their body temperatures. The shell is divided two sections, the upper or dorsal carapace, and the lower, ventral carapace or plastron. The rear marginal scutes are notched, the scutes are bony keratinous elements. The carapace is oval and flattened and has a keel that is more pronounced in the young. The color of the carapace changes depending on the age of the turtle, the carapace usually has a dark green background with light and dark, highly variable markings. In young or recently hatched turtles, it is green and gets slightly darker as a turtle gets older, until it is a very dark green. The plastron is always a light yellow with dark, paired, the plastron is highly variable in pattern. The head, legs, and tail are green with fine, irregular, the whole shell is covered in these stripes and markings that aid in camouflaging an individual
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Tortoise
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Tortoises are a family, Testudinidae, of land-dwelling reptiles in the order Testudines. Tortoises are shielded from predators by a shell, the top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge. The carapace is fused to both the vertebrae and ribcage, and tortoises are unique among vertebrates in that the pectoral, Tortoises can vary in size from a few centimeters to two meters. They are usually diurnal animals with tendencies to be depending on the ambient temperatures. Tortoises are the longest living animal in the world, although the longest living species of tortoise is a matter of debate. Galapagos tortoises are noted to live over 150 years, but an Aldabra giant tortoise named Adwaita may having been the longest living at an estimated 255 years. It is important to note that tortoises are not the longest living animal, period, with bowhead whales reaching over 200 years, and the ocean quahog clam reaching 500 years old. Differences exist in usage of the common terms turtle, tortoise and these terms are common names and do not reflect precise biological or taxonomic distinctions. In America, for example, the members of the genus Terrapene dwell on land, in Britain, terrapin is used to refer to a larger group of semiaquatic turtles than the restricted meaning in America. Australian usage is different from both American and British usage, land tortoises are not native to Australia, yet traditionally freshwater turtles have been called tortoises in Australia. Female tortoises dig nesting burrows in which lay from one to 30 eggs. Egg-laying typically occurs at night, after which the mother covers her clutch with sand, soil. The eggs are unattended, and depending on the species. The size of the egg depends on the size of the mother, the plastron of a female tortoise often has a noticeable V-shaped notch below the tail which facilitates passing the eggs. Upon completion of the period, a fully formed hatchling uses an egg tooth to break out of its shell. It digs to the surface of the nest and begins a life of survival on its own and they are hatched with an embryonic egg sac which serves as a source of nutrition for the first three to seven days until they have the strength and mobility to find food. Juvenile tortoises often require a different balance of nutrients than adults, for example, the young of a strictly herbivorous species commonly will consume worms or insect larvae for additional protein. Moreover, some tortoises grow more than one ring per season, Tortoises generally have one of the longest lifespans of any animal, and some individuals are known to have lived longer than 150 years
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Terrapin
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A terrapin is one of several small species of turtle living in fresh or brackish water. Terrapins do not form a unit, and may not be related. Many belong to the families Geoemydidae and Emydidae, the name terrapin is derived from torope, a word in the Native American Algonquian language that referred to the species, Malaclemys terrapin. It appears that it became part of common usage during the era of North America and was carried back to Great Britain. Since then, it has used in common names for turtles in the English language. Diamondback terrapin or just terrapin, Malaclemys terrapin, a turtle of the Emydidae family, European pond terrapin or European pond turtle, Emys orbicularis, a turtle in the family Emydidae found in West Asia and parts of North Africa. Indian pond terrapin, or Indian black turtle, Melanochelys trijuga, Mexican spotted terrapin or Mexican spotted wood turtle, Rhinoclemmys rubida, a species of turtle in the family Geoemydidae, endemic to Mexico. Northern river terrapin, Batagur baska, an endangered turtle in the Geoemydidae family native to Cambodia. Painted terrapin, Batagur borneoensis, a turtle in the Geoemydidae family native to Brunei, Indonesia, Malaysia, red-eared terrapin, Trachemys scripta elegans, a turtle of southern North America in the family Emydidae, a popular pet and an invasive species in many places. Serrated hinged terrapin, Pelusios sinuatus, is a species of turtle in the Pelomedusidae family found in southern Africa, Seychelles black terrapin, Pelusios seychellensis, an extinct species of turtle in the Pelomedusidae family that was endemic to the Seychelles. Smiling terrapin or Black marsh turtle, Siebenrockiella crassicollis, a turtle in the Geoemydidae family native to Southeast Asia, southern river terrapin, Batagur affinis, a turtle in the Geoemydidae family native to Cambodia. Striped-neck terrapin or Caspian turtle, Mauremys caspica, a turtle in the family Geoemydidae, native to the eastern Mediterranean region
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Form classification
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Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty, the goal of science is to form taxa to biological taxa whose affinity is known. Form taxa are groupings that are based on common overall forms, early attempts at classification of labyrinthodonts was based on skull shape. The amount of convergent evolution in the groups lead to a number of polyphyletic taxa. Such groups are united by a mode of life, often one that is generalist. Ediacaran biota — whether they are the precursors of the Cambrian explosion of the fossil record, other examples include the seabirds and the Graculavidae. A parataxon, or sciotaxon, is a based on incomplete data, for instance. It reflects a paucity of data that makes biological classification impossible, a later term morphotaxa also allows for differences in preservational state. These three terms have been replaced as of 2011 by provisions for fossil-taxa that are similar to the provisions for other types of plants. Names given to organ genera could only be applied to the organs in question, fossil-taxon names can cover several parts of an organism, or several preservational states, but do not compete for priority with any names for the same organism that are based on a non-fossil type. Well-known form taxa of this kind include ducks, fish, reptiles and worms
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. PMID 23624526. Retrieved November 15, 2013.
