1.
Precambrian
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The Precambrian is the earliest period of Earths history, set before the current Phanerozoic Eon. The Precambrian is a supereon that is subdivided into three eons of the time scale. It spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, the Precambrian accounts for 89% of geologic time. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earths history, the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, and fossils from that time are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion. A stable crust was apparently in place by 4,412 Ma, the term Precambrian is recognized by the International Commission on Stratigraphy as a general term including the Archean and Proterozoic eons. It is still used by geologists and paleontologists for general discussions not requiring the more specific eon names and it was briefly called the Cryptozoic eon. A specific date for the origin of life has not been determined, carbon found in 3.8 billion year old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have found in Western Australia. Probable fossils 100 million years older have been found in the same area, there is a fairly solid record of bacterial life throughout the remainder of the Precambrian. The oldest fossil evidence from that era of such complex life comes from the Lantian formation of the Ediacarian period, a very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota, hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic era. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale. The explosion in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life, while land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Evidence of the details of plate motions and other activity in the Precambrian has been poorly preserved. It is generally believed that small proto-continents existed prior to 4280 Ma, the supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch, one of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a Snowball Earth. The atmosphere of the early Earth is not well understood, most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and was lacking in free oxygen
2.
Cambrian
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The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya and its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, as a result, our understanding of the Cambrian biology surpasses that of some later periods. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia, the seas were relatively warm, and polar ice was absent for much of the period. The United States Federal Geographic Data Committee uses a barred capital C ⟨Є⟩ character similar to the capital letter Ukrainian Ye ⟨Є⟩ to represent the Cambrian Period, the proper Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH BAR. Despite the long recognition of its distinction from younger Ordovician Period rocks and older Supereon Precambrian rocks, the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. Pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA, the stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain. The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period, the Cambrian is divided into four epochs and ten ages. Currently only two series and five stages are named and have a GSSP, because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian, Middle Cambrian and Furongian, rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian, each of the local epochs is divided into several stages. The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago, the lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites. The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier and this formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago quickly gained favour, though the used to obtain this number are now considered to be unsuitable. A more precise date using modern radiometric dating yield a date of 541 ±0.3 million years ago, most continental land was clustered in the Southern Hemisphere at this time, but was drifting north. Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian, the sea levels fluctuated somewhat, suggesting there were ice ages, associated with pulses of expansion and contraction of a south polar ice cap. In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into a epicontinental sea, the Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents
3.
Ordovician
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The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Mya. Lapworth recognized that the fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods. It received international sanction in 1960, when it was adopted as a period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, invertebrates, namely molluscs and arthropods, dominated the oceans. The Great Ordovician Biodiversification Event considerably increased the diversity of life, fish, the worlds first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land, about 100 times as many meteorites struck the Earth during the Ordovician compared with today. The Ordovician Period began with a major extinction called the Cambrian–Ordovician extinction event and it lasted for about 42 million years and ended with the Ordovician–Silurian extinction event, about 443.8 Mya which wiped out 60% of marine genera. The dates given are recent radiometric dates and vary slightly from those found in other sources and this second period of the Paleozoic era created abundant fossils that became major petroleum and gas reservoirs. The boundary chosen for the beginning of both the Ordovician Period and the Tremadocian stage is highly significant and it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species. The base of the Tremadocian allows scientists to relate these species not only to each other and this makes it easier to place many more species in time relative to the beginning of the Ordovician Period. A number of terms have been used to subdivide the Ordovician Period. In 2008, the ICS erected an international system of subdivisions. There exist Baltoscandic, British, Siberian, North American, Australian, the Ordovician Period in Britain was traditionally broken into Early, Middle and Late epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, the Floian corresponds to the lower Arenig, the Arenig continues until the early Darriwilian, subsuming the Dapingian. The Llanvirn occupies the rest of the Darriwilian, and terminates with it at the base of the Late Ordovician. The Sandbian represents the first half of the Caradoc, the Caradoc ends in the mid-Katian, during the Ordovician, the southern continents were collected into Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole, the small continent Avalonia separated from Gondwana and began to move north towards Baltica and Laurentia, opening the Rheic Ocean between Gondwana and Avalonia
4.
Silurian
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The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway
5.
Devonian
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The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, England, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician. The first ammonites, species of molluscs, appeared, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers
6.
Carboniferous
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The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period,298.9 Mya. The name Carboniferous means coal-bearing and derives from the Latin words carbō and ferō, and was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the system names to be employed. The Carboniferous is often treated in North America as two periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial life was established by the Carboniferous period. Amphibians were the dominant land vertebrates, of one branch would eventually evolve into amniotes. Arthropods were also common, and many were much larger than those of today. Vast swaths of forest covered the land, which would eventually be laid down, the atmospheric content of oxygen also reached their highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. A major marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred in the middle of the period, the later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. In the United States the Carboniferous is usually broken into Mississippian and Pennsylvanian subperiods, the Silesian is roughly contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, and the Westphalian as the Coal Measures and Pennant Sandstone. There was also a drop in south polar temperatures, southern Gondwanaland was glaciated throughout the period and these conditions apparently had little effect in the deep tropics, where lush swamps, later to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major extinction, one that hit crinoids. This sea level drop and the unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation, the Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America, in the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, the Late Carboniferous Pangaea was shaped like an O. There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the O in the Carboniferous Pangaea, other minor oceans were shrinking and eventually closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean
7.
Permian
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The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, turtles, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms. During the Permian, all the Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, fungi, arthropods, the period saw a massive desert covering the interior of Pangaea
8.
Triassic
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The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago, to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era, both the start and end of the period are marked by major extinction events. Therapsids and archosaurs were the terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic, the vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, however, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another mass extinction, the Triassic-Jurassic extinction event. The Triassic is usually separated into Early, Middle, and Late Triassic Epochs, from the east, along the equator, the Tethys sea penetrated Pangaea, causing the Paleo-Tethys Ocean to be closed. Later in the mid-Triassic a similar sea penetrated along the equator from the west, the remaining shores were surrounded by the world-ocean known as Panthalassa. All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates, thus, the supercontinent Pangaea was rifting during the Triassic—especially late in that period—but had not yet separated. In North America, for example, marine deposits are limited to a few exposures in the west, thus Triassic stratigraphy is mostly based on organisms that lived in lagoons and hypersaline environments, such as Estheria crustaceans. At the beginning of the Mesozoic Era, Africa was joined with Earths other continents in Pangaea, Africa shared the supercontinents relatively uniform fauna which was dominated by theropods, prosauropods and primitive ornithischians by the close of the Triassic period. Late Triassic fossils are found throughout Africa, but are common in the south than north. The time boundary separating the Permian and Triassic marks the advent of an event with global impact. At Paleorrota geopark, located in Rio Grande do Sul, Brazil, in these formations, one of the earliest dinosaurs, Staurikosaurus, as well as the mammal ancestors Brasilitherium and Brasilodon have been discovered. The Triassic continental interior climate was hot and dry, so that typical deposits are red bed sandstones and evaporites. Pangaeas large size limited the effect of the global ocean, its continental climate was highly seasonal, with very hot summers. The strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons, the best studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event. On land, the vascular plants included the lycophytes, the dominant cycadophytes, ginkgophyta, ferns, horsetails
9.
Jurassic
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The Jurassic is a geologic period and system that spans 56.3 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles, the start of the period is marked by the major Triassic–Jurassic extinction event. The Jurassic is named after the Jura Mountains within the European Alps, by the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, on land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs, other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to a mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, the chronostratigraphic term Jurassic is directly linked to the Jura Mountains. The name Jura is derived from the Celtic root jor, which was Latinised into juria, the Jurassic period is divided into the Early Jurassic, Middle, and Late Jurassic epochs. The Jurassic System, in stratigraphy, is divided into the Lower Jurassic, Middle, the separation of the term Jurassic into three sections goes back to Leopold von Buch. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, the Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation, as in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed. In contrast, the North American Jurassic record is the poorest of the Mesozoic, the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, India, South America, Japan, Australasia. As the Jurassic proceeded, larger and more groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are well represented nor well studied in Africa. Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania, the Late Jurassic life of Tendaguru is very similar to that found in western North Americas Morrison Formation. During the Jurassic period, the primary living in the sea were fish
10.
Cretaceous
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The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
11.
Paleogene
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The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera
12.
Neogene
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The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene, some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. During this period, mammals and birds continued to evolve into modern forms. Early hominids, the ancestors of humans, appeared in Africa near the end of the period, some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the ocean currents from the Pacific to the Atlantic ocean. The global climate cooled considerably over the course of the Neogene, the terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period. The continents in the Neogene were very close to their current positions, the Isthmus of Panama formed, connecting North and South America. The Indian subcontinent continued to collide with Asia, forming the Himalayas, sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America. The global climate became seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the current Ice Age began, marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the part of the period. Mammals and birds continued to be the dominant terrestrial vertebrates, the first hominids, the ancestors of humans, appeared in Africa and spread into Eurasia. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones, grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison. The Neogene traditionally ended at the end of the Pliocene Epoch, just before the definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to also include ongoing geological time in the Neogene, by dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The International Commission on Stratigraphy once proposed that the Quaternary be considered a sub-era of the Neogene, with a date of 2.58 Ma. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs, thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. Digital Atlas of Neogene Life for the Southeastern United States — by San Jose State University via Web Archive
13.
Homarus gammarus
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Homarus gammarus, known as the European lobster or common lobster, is a species of clawed lobster from the eastern Atlantic Ocean, Mediterranean Sea and parts of the Black Sea. It is closely related to the American lobster, H. americanus and it may grow to a length of 60 cm and a mass of 6 kilograms, and bears a conspicuous pair of claws. In life, the lobsters are blue, only becoming lobster red on cooking, mating occurs in the summer, producing eggs which are carried by the females for up to a year before hatching into planktonic larvae. Homarus gammarus is an esteemed food, and is widely caught using lobster pots. Like other crustaceans, lobsters have an exoskeleton which they must shed in order to grow. This may occur several times a year for young lobsters, the first pair of pereiopods is armed with a large, asymmetrical pair of claws. The larger one is the crusher, and has rounded nodules used for crushing prey, the other is the cutter, which has sharp inner edges, usually, the left claw is the crusher, and the right is the cutter. The exoskeleton is generally blue above, with spots that coalesce, the red colour associated with lobsters only appears after cooking. This occurs because, in life, the red pigment astaxanthin is bound to a protein complex, the closest relative of H. gammarus is the American lobster, Homarus americanus. The two species are similar, and can be crossed artificially, although hybrids are unlikely to occur in the wild since their ranges do not overlap. The two species can be distinguished by a number of characteristics, The rostrum of H. americanus bears one or more spines on the underside, the spines on the claws of H. americanus are red or red-tipped, while those of H. gammarus are white or white-tipped. The underside of the claw of H. americanus is orange or red, female H. gammarus reach sexual maturity when they have grown to a carapace length of 80–85 millimetres, whereas males mature at a slightly smaller size. Mating typically occurs in summer between a recently moulted female, whose shell is soft, and a hard-shelled male. The female carries the eggs for up to 12 months, depending on the temperature, females carrying eggs are said to be berried and can be found throughout the year. The eggs hatch at night, and the swim to the water surface where they drift with the ocean currents. This stage involves three moults and lasts for 15–35 days, after the third moult, the juvenile takes on a form closer to the adult, and adopts a benthic lifestyle. The juveniles are rarely seen in the wild, and are poorly known and it is estimated that only 1 larva in every 20,000 survives to the benthic phase. When they reach a length of 15 mm, the juveniles leave their burrows
14.
Taxonomy (biology)
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Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
15.
Animal
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Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
16.
Arthropod
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An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods form the phylum Arthropoda, which includes the insects, arachnids, myriapods, arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages, the rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Their versatility has enabled them to become the most species-rich members of all guilds in most environments. They have over a million described species, making up more than 80% of all described living species, some of which. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab, arthropods primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates, they have open circulatory systems. Like their exteriors, the organs of arthropods are generally built of repeated segments. Their nervous system is ladder-like, with paired ventral nerve cords running through all segments and their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong, arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae that project through their cuticles. Aquatic species use internal or external fertilization. Almost all arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother, arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. The evolutionary ancestry of arthropods dates back to the Cambrian period, the group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall however, the relationships of Metazoa are not yet well resolved. Likewise, the relationships between various groups are still actively debated. Arthropods contribute to the food supply both directly as food, and more importantly indirectly as pollinators of crops. Some species are known to spread disease to humans, livestock. The word arthropod comes from the Greek ἄρθρον árthron, joint, and πούς pous, i. e. foot or leg, arthropods are invertebrates with segmented bodies and jointed limbs
17.
Crustacean
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Crustaceans form a large, diverse arthropod taxon which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill, woodlice and barnacles. In other words, some crustaceans are more related to insects. The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm, to the Japanese spider crab with a leg span of up to 3.8 m, like other arthropods, crustaceans have an exoskeleton, which they moult to grow. Most crustaceans are free-living aquatic animals, but some are terrestrial, some are parasitic, the group has an extensive fossil record, reaching back to the Cambrian, and includes living fossils such as Triops cancriformis, which has existed apparently unchanged since the Triassic period. More than 10 million tons of crustaceans are produced by fishery or farming for human consumption, krill and copepods are not as widely fished, but may be the animals with the greatest biomass on the planet, and form a vital part of the food chain. The scientific study of crustaceans is known as carcinology, and a scientist who works in carcinology is a carcinologist, the body of a crustacean is composed of segments, which are grouped into three regions, the cephalon or head, the thorax, and the pleon or abdomen. The head and thorax may be fused together to form a cephalothorax, the crustacean body is protected by the hard exoskeleton, which must be moulted for the animal to grow. The shell around each somite can be divided into a dorsal tergum, ventral sternum, various parts of the exoskeleton may be fused together. The abdomen bears pleopods, and ends in a telson, which bears the anus, the number and variety of appendages in different crustaceans may be partly responsible for the groups success. It is unclear whether the condition is a derived state which evolved in crustaceans. Trilobites, for instance, also possessed biramous appendages, the main body cavity is an open circulatory system, where blood is pumped into the haemocoel by a heart located near the dorsum. Malacostraca have haemocyanin as the pigment, while copepods, ostracods, barnacles. The alimentary canal consists of a tube that often has a gizzard-like gastric mill for grinding food and a pair of digestive glands that absorb food. Structures that function as kidneys are located near the antennae, a brain exists in the form of ganglia close to the antennae, and a collection of major ganglia is found below the gut. In many decapods, the first pair of pleopods are specialised in the male for sperm transfer, many terrestrial crustaceans mate seasonally and return to the sea to release the eggs. Others, such as woodlice, lay their eggs on land, in most decapods, the females retain the eggs until they hatch into free-swimming larvae. Marine crustaceans are as ubiquitous in the oceans as insects are on land, some branchiurans are able to withstand rapid changes of salinity and will also switch hosts from marine to non-marine species. Krill are the layer and the most important part of the food chain in Antarctic animal communities
18.
Malacostraca
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Malacostraca is the largest of the six classes of crustaceans, containing about 40,000 living species, divided among 16 orders. They are abundant in all environments and have colonised freshwater. They are segmented animals, united by a body plan comprising 20 body segments, and divided into a head, thorax. The name Malacostraca was coined by a French zoologist Pierre André Latreille in 1802 and he was curator of the arthropod collection at the National Museum of Natural History in Paris. The name comes from the Greek roots μαλακός and ὄστρακον, the name is misleading, since the shell is only soft immediately after moulting, and is usually hard. Malacostracans are sometimes contrasted with entomostracans, a name applied to all crustaceans outside the Malacostraca, the class Malacostraca includes about 40,000 species, and arguably. Contains a greater diversity of forms than any other class in the animal kingdom. Malacostracans have abdominal appendages, a fact that differentiates them from all other major crustacean taxa except Remipedia, each body segment bears a pair of jointed appendages, although these may be lost secondarily. The head bears two pairs of antennae, the first of which is often biramous and the second pair bear exopods which are flattened into antennal scales known as scaphocerites. The mouthparts consist of each of mandibles, maxillules and maxillae. Usually a pair of stalked compound eyes is present, although in some taxa the eyes are unstalked, reduced or lost, up to three thoracic segments may be fused with the head to form a cephalothorax, the associated appendages turn forward and are modified as maxillipeds. A carapace may be absent, present or secondarily lost, and may cover the head, part or all of the thorax and it is variable in form and may be fused dorsally with some of the thoracic segments or occasionally be in two parts, hinged dorsally. Typically, each of the thoracic appendages is biramous and the endopods are the developed of the branches. Each endopod consist of seven articulating segments, the coxa, basis, ischium, in decapods, the claw is formed by the articulation of the dactylus against an outgrowth of the propodus. In some taxa, the exopods are lost and the appendages are uniramous, there is a clear demarcation between the thorax and the six or seven-segmented abdomen. In most taxa, each abdominal segment except the last carries a pair of biramous pleopods used for swimming, burrowing, gas exchange, the first and second abdominal pleopods may be modified in the male to form gonopods. The appendages of the last segment are typically flattened into uropods and it is the sudden flexion of this tail fan that provides the thrust for the rapid escape response of these crustaceans and the tail fan is also used in steering. In Leptostraca, the appendages on the telson instead form caudal rami, the digestive tract is straight and the foregut consists of a short oesophagus and a two-chambered stomach, the first part of which contains a gizzard-like gastric mill for grinding food
19.
Decapoda
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The Decapoda or decapods are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns, and shrimp. The order is estimated to contain nearly 15,000 species in around 2,700 genera, nearly half of these species are crabs, with the shrimp and Anomura (including hermit crabs, porcelain crabs, squat lobsters making up the bulk of the remainder. The earliest fossil decapod is the Devonian Palaeopalaemon, as the name Decapoda implies, all decapods have what are considered ten legs, in the form of five pairs of thoracic appendages on the last five thoracic segments. Decapods can have as many as twenty apendages, arranged in one pair per body segment, the front three pairs function as mouthparts and are generally referred to as maxillipeds, the remainder are pereiopods. In many decapods, however, one pair of legs has enlarged pincers, the remaining appendages are found on the abdomen, with each segment capable of carrying a pair of biramous pleopods, the last of which form part of the tail fan and are called uropods. Classification within the order Decapoda depends on the structure of the gills and legs, the Dendrobranchiata consist of prawns, including many species colloquially referred to as shrimp, such as the white shrimp, Litopenaeus setiferus. The Pleocyemata include the groups, including true shrimp. Those groups which usually walk rather than form a clade called Reptantia. This classification to the level of superfamilies follows De Grave et al
20.
James Dwight Dana
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James Dwight Dana FRS FRSE was an American geologist, mineralogist, volcanologist, and zoologist. He made pioneering studies of mountain-building, volcanic activity, and the origin and structure of continents, Dana was born February 12,1813 in Utica, New York. His father was merchant James Dana, and mother was Harriet Dwight, through his mother he was related to the Dwight New England family of missionaries and educators including uncle Harrison Gray Otis Dwight and first cousin Henry Otis Dwight. Graduating in 1833, for the two years he was teacher of mathematics to midshipmen in the Navy, and sailed to the Mediterranean while engaged in his duties. His labors in preparing the reports of his explorations occupied parts of thirteen years after his return to America in 1842 and his notebooks from the four years of travel contained fifty sketches, maps, and diagrams, including views of both Mount Shasta and Castle Crags. Danas sketch of Mount Shasta was engraved in 1849 for publication in the American Journal of Science and Arts, in the article he described in scientific terms the rocks, minerals, and geology of the Shasta region. As far as is known, his sketch of Mount Shasta became the view of the mountain ever published. In 1844 he again became a resident of New Haven, and married Professor Sillimans daughter, in 1850, he was appointed as Sillimans successor, as Silliman Professor of Natural History and Geology in Yale College, a position which he held until 1892. The 1849 publication of his geology of Mount Shasta was undoubtedly a response to the California gold rush publicity. Dana was the pre-eminent U. S. geologist of his time and he had previously written that there was likelihood that gold was to be found all along the route between the Umpqua River in Oregon and the Sacramento Valley. He was probably deluged with inquiries about the Shasta region, and was forced to publish in more detail some advice to the gold miners. Dana was responsible for developing much of the knowledge on Hawaiian volcanism. In 1880 and 1881 he led the first geological study of the volcanics of Hawaii island, Dana theorized that the volcanic chain consisted of two volcanic strands, dubbed the Loa and Kea trends. The Kea trend included Kīlauea, Mauna Kea, Kohala, Haleakala, the Loa trend includes Lōʻihi, Mauna Loa, Hualālai, Kahoʻolawe, Lānaʻi, and West Molokaʻi. Following another expedition by fellow geologist C. E. Dana died on April 14,1895, Dana was married to Henrietta Silliman in 1844. Their son, Edward Salisbury Dana, was also a distinguished mineralogist, Danas best known books were his System of Mineralogy Manual of Mineralogy, and his Manual of Geology. A bibliographical list of his writings shows 214 titles of books and papers and his reports on Zoophytes, on the Geology of the Pacific Area, and on Crustacea, summarizing his work on the Wilkes Expedition, appeared from 1846 onwards. Other works included Manual of Mineralogy, afterwards entitled Manual of Mineralogy and Lithology, in 1887, Dana revisited the Hawaiian Islands, and the results of his further investigations were published in a quarto volume entitled Characteristics of Volcanoes
21.
Genus
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A genus is a taxonomic rank used in the biological classification of living and fossil organisms in biology. In the hierarchy of classification, genus comes above species. In binomial nomenclature, the name forms the first part of the binomial species name for each species within the genus. Felis catus and Felis silvestris are two species within the genus Felis, Felis is a genus within the family Felidae. The composition of a genus is determined by a taxonomist, the standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. Moreover, genera should be composed of units of the same kind as other genera. The term comes from the Latin genus, a noun form cognate with gignere, linnaeus popularized its use in his 1753 Species Plantarum, but the French botanist Joseph Pitton de Tournefort is considered the founder of the modern concept of genera. The scientific name of a genus may be called the name or generic epithet. It plays a role in binomial nomenclature, the system of naming organisms. The rules for the names of organisms are laid down in the Nomenclature Codes. The standard way of scientifically describing species and other lower-ranked taxa is by binomial nomenclature, the generic name forms its first half. For example, the gray wolfs binomial name is Canis lupus, with Canis being the name shared by the wolfs close relatives. The specific name is written in lower-case and may be followed by names in zoology or a variety of infraspecific names in botany. Especially with these names, when the generic name is known from context. Because animals are typically only grouped within subspecies, it is written as a trinomen with a third name. Dog breeds, meanwhile, are not scientifically distinguished, there are several divisions of plant species and therefore their infraspecific names generally include contractions explaining the relation. For example, the genus Hibiscus includes hundreds of other species apart from the Rose of Sharon or common garden hibiscus, Rose of Sharon doesnt have subspecies but has cultivars that carry desired traits, such as the bright white H. syriaca Diana. Hawaiian hibiscus, meanwhile, includes several separate species, since not all botanists agree on the divisions or names between species, it is common to specify the source of the name using author abbreviations
22.
Acanthacaris
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Acanthacaris is a genus of deep-water lobsters. It contains two species, A. caeca and A. tenuimana, and is the genus in the subfamily Neophoberinae. They are relatively large lobsters with a body covered with sharp spines. The carapace has a well-developed rostrum, the eyes are very small and lack pigment, while the antennae are long and whiplike. The telson and uropods are powerful, the first three pairs of walking legs end in claws. The first pair of claws is symmetrical, and ends in long fingers covered with spines on cutting edges. The second pair of walking legs is longer than the third pair. Both species reach a length of 40 centimetres, the genus Acanthacaris is the only genus in the subfamily Neophoberinae, and contains two species, Acanthacaris caeca is found in the Caribbean Sea, in burrows at a depth of 290–870 m. Acanthacaris tenuimana, the species, is found in the Indian and Pacific Oceans. Although the replacement name Neophoberus was provided by Martin Glaessner in 1969, this is pre-dated by Charles Spence Bates 1888 name Acanthacaris, which has A. tenuimana as the type species
23.
Cape lobster
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The Cape lobster, Homarinus capensis, is a species of small lobster that lives off the coast of South Africa, from Dassen Island to Haga Haga. Only a few specimens are known, mostly regurgitated by reef-dwelling fish. It lives in reefs, and is thought to lay large eggs that have a short larval phase. Its closest relatives are the genera Thymops and Thymopides, the Cape lobster is endemic to South Africa. It occurs from Dassen Island, Western Cape in the west to Haga Haga, Eastern Cape in the east, most of the known specimens were regurgitated by fish caught on reefs at depths of 20–40 metres. Accounts of the colouration of H. capensis are variable, from tawny, red or yellow to a rather dark olive. Homarinus and Homarus are considered to be the most plesiomorphic genera in the family Nephropidae, nonetheless, the Cape lobster differs from Homarus in a number of characters. The rostrum of the Cape lobster is flattened, while that of Homarus is rounded in section, the three pairs of claws are covered with hairs in Homarinus, while those of Homarus are hairless. The telson tapers along its length in Homarus, but has sides which are parallel in Homarinus. Although no egg-bearing females have been collected, the gonopores of female Cape lobsters are much larger than those of Homarus gammarus and Homarus americanus, Cape lobsters are elusive and rare, with only fourteen specimens having been collected between 1792 and 1992. In 1992, a Cape lobster was discovered at Dassen Island, the Cape lobster was first described by Johann Friedrich Wilhelm Herbst in 1792 as Cancer capensis. It was independently described in 1793 by Johan Christian Fabricius as Astacus flavus, when Friedrich Weber erected the genus Homarus in 1795, he included Fabricius species in it, but this placement was not followed by later authors. The species reached its current classification in 1995, when the monotypic genus Homarinus was erected by Irv Kornfield, Austin B. Williams, while analyses of morphology suggest a close relationship between Homarinus and Homarus, molecular analyses using mitochondrial DNA reveal that they are not sister taxa. Both genera lack ornamentation such as spines and carinae, but are thought to have reached that state independently, the closest living relative of Homarus is Nephrops norvegicus, while the closest relatives of Homarinus are Thymops and Thymopides
24.
Homarus
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Homarus is a genus of lobsters, which include the common and commercially significant species Homarus americanus and Homarus gammarus. The Cape lobster, which was formerly in this genus as H. capensis, was moved in 1995 to the new genus Homarinus, Homarus is one of three extant genera of clawed lobsters to show dimorphism between claws – a specialisation into a crushing claw and a cutting claw. While analyses of morphology suggest a relationship between Homarinus and Homarus, molecular analyses using mitochondrial DNA reveal that they are not sister taxa. Both genera lack ornamentation such as spines and carinae, but are thought to have reached that state independently, the closest living relative of Homarus is Nephrops norvegicus, while the closest relatives of Homarinus are Thymops and Thymopides. Eight extinct species are known from the record, which stretches back to the Cretaceous. These two species, the American lobster and the European lobster, are similar and may have speciated as recently as the Pleistocene. Americanus but not in H. gammarus, Homarus gammarus, known as the European lobster or common lobster, may grow to a length of 60 cm and a mass of 6 kilograms, and bears a conspicuous pair of claws. In life, the lobsters are blue, only becoming lobster red on cooking, Homarus gammarus is a highly esteemed food, and is widely caught using lobster pots, mostly around the British Isles. An average adult is about 23 cm long and weighs 700–900 g, the boundaries between Homarus and the extinct genus Hoploparia are unclear, and some species, such as Hoploparia benedeni have been transferred between the two genera. Eight species have been assigned to Homarus from the fossil record, mating in Homarus is complex and is accompanied by a number of courtship behaviours. Males build mating shelters or burrows, and larger males can attract more females, a few days before moulting, a female will choose a mate, and will remain in his shelter until the moult. The male will insert a spermatophore into the females seminal vesicle. The eggs of Homarus species are laid in the autumn, being fertilised externally as they exit, the eggs generally hatch in the spring as a pre-larva, which rapidly develops into the first larval phase. This is followed by three phases, the total duration of which can vary from two weeks to two months, depending on the temperature. At the following moult, the animal becomes a post-larva. Although it can swim, using its pleopods, the post-larva soon settles to the bottom, as adults, Homarus species moult increasingly infrequently. The size at maturity varies with temperature, it is around 70 mm for female H. americanus in southern New England. In H. gammarus, the size at maturity is less well defined
25.
Nephropides
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Nephropides caribaeus is a species of lobster, the only species in the genus Nephropides. It is found in parts of the Caribbean Sea, from Belize to Colombia. It grows to a length of around 170 mm, and is covered in conspicuous tubercles. Nephropides caribaeus is a lobster, resembling Nephropsis or Nephrops. Adults of N. caribaeus are typically 155–170 millimetres in total length and it differs from Nephropsis in that the eyes contain pigment, which is lacking in Nephropsis. The rostrum has 2–3 lateral spines, but no spines on the lower edge, the whole body is covered in large tubercles, including the first pereiopods with their large chelae, and the other, smaller pereiopods. Nephropides caribaeus is found in the western Caribbean Sea, and has recorded from Belize to Colombia. It is a species, living on muddy bottoms at depths of 455–728 metres. The genus Nephropides and the species N. caribaeus were both erected in 1969 by Raymond B, a second species later described in the genus has since been transferred to Thymops as Thymops birsteini. The Food and Agriculture Organization has assigned the species an English name of mitten lobsterette, the type locality is at 12°25′N 82°15′W, off the coast of Nicaragua, at a depth of 546–582 metres. The generic name Nephropides alludes to a relationship with the genus Nephrops
26.
Thaumastocheles
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The family Thaumastochelidae contains five known species of deep-sea lobsters, three in the genus Thaumastocheles, and two in the genus Thaumastochelopsis. The fifth species was discovered in the ten–year Census of Marine Life and these creatures are distinguished from other clawed lobsters by their blindness, and by their single elongated, spiny chela. The five species are as follows, Thaumastocheles Thaumastocheles dochmiodon Chan & de Saint Laurent,1999 is found in the Timor Sea, Thaumastocheles japonicus Calman,1913, the Pacific pincer lobster, is endemic to the Sea of Japan. Thaumastocheles zaleucus Thomson,1873, the Atlantic pincer lobster or Atlantic deep-sea lobster, is endemic to the Caribbean region, Thaumastochelopsis Thaumastochelopsis brucei Ahyong, Chu & Chan,2007 lives in the Coral Sea. Thaumastochelopsis wardi Bruce,1988, the Australian pincer lobster, lives in the Coral Sea
27.
Thaumastochelopsis
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The family Thaumastochelidae contains five known species of deep-sea lobsters, three in the genus Thaumastocheles, and two in the genus Thaumastochelopsis. The fifth species was discovered in the ten–year Census of Marine Life and these creatures are distinguished from other clawed lobsters by their blindness, and by their single elongated, spiny chela. The five species are as follows, Thaumastocheles Thaumastocheles dochmiodon Chan & de Saint Laurent,1999 is found in the Timor Sea, Thaumastocheles japonicus Calman,1913, the Pacific pincer lobster, is endemic to the Sea of Japan. Thaumastocheles zaleucus Thomson,1873, the Atlantic pincer lobster or Atlantic deep-sea lobster, is endemic to the Caribbean region, Thaumastochelopsis Thaumastochelopsis brucei Ahyong, Chu & Chan,2007 lives in the Coral Sea. Thaumastochelopsis wardi Bruce,1988, the Australian pincer lobster, lives in the Coral Sea
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Thymopides
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Thymopides is a genus of deep-water lobsters, comprising the two species Thymopides grobovi and Thymopides laurentae. Two species are included in the genus Thymopides, Thymopides grobovi is found around Heard Island and the Kerguelen Archipelago in the southern Indian Ocean at depths of 525–1,220 metres. Thymopides laurentae is only known from a hydrothermal vent on the Mid-Atlantic Ridge at a depth of 3,480 m. Thymopides differs from related genera such as Homarus, Homarinus and Nephrops in having the first pair of pereiopods of similar size and shape, rather than one crusher and one cutter claw. It differs from others, such as Metanephrops and Eunephrops by the lack of a carina behind the spine, by the smaller size of some spines and by the smaller. The genus was first described by R. N. Burukovsky and B. S. Averin in 1976 under the name Bellator, after Lipke Holthuis informed the authors that a genus already existed called Bellator, they published a replacement name in a paper in the journal Crustaceana. That new name was Thymopides, referring to the resemblance between the new genus and the genus Thymops. The original genus name, Bellator derived from the Latin word bellator, in 2003, a second species was described, T. laurentae, commemorating Michèle de Saint Laurent
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Thymops
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Thymops birsteini, the Patagonian lobsterette, is a species of lobster found around the coasts of South America, particularly the South Atlantic. It belongs to the monotypic genus Thymops, T. birsteini is found on the continental shelf around South America, particularly in the Argentine Sea. In the Atlantic Ocean, it is south of 37° south, with Uruguay representing the northern extremity of its distribution, on the Chilean side. Its range includes the areas around the Falkland Islands and areas near South Georgia, extending as far south as 57° and it lives at depths of 120–1,500 metres. T. birsteini resembles a lobster, with two large claws, four other pairs of pereiopods, and a long pleon. The carapace is granular, especially in the front half, the total length may range from 8 to 25 centimetres, with the carapace being 2–10 cm long. Smaller individuals are found in shallower waters, and larger individuals are found at greater depths, there is also latitudinal variation in colour, with northern individuals being pale yellow, while those from further south are maroon. Little is known about the interactions of T. birsteini. It is occasionally eaten by the Patagonian toothfish Dissostichus eleginoides and it seems to prefer muddy bottoms, and has been observed entering and exiting burrows. As in other pleocyemates, T. birsteini broods its eggs on the females pleopods, one female may carry up to 380 eggs, each 1. 5–1.9 millimetres in diameter. The eggs grow as they develop to a size of 2. 9–3.3 mm. Newly hatched larvae have a length of 1. 7–2.2 mm. This extended larval release has previously found in other sub-Antarctic decapods, and is an adaptation to the low temperature, the long time taken for brooding. The meat of T. birsteini is reported to be excellent, the average weight of a caught individual is about 150 grams, of which 30% is the meaty tail. Daily yields of 19 kilograms are typical
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Trenton, Maine
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Trenton is a town in Hancock County, Maine, United States, near Acadia National Park. The population was 1,481 at the 2010 census, Hancock County-Bar Harbor Airport is located in Trenton. In January 1969, town voters defeated 144-77 an attempt to build a power plant. According to the United States Census Bureau, the town has an area of 28.39 square miles. As of the census of 2010, there were 1,481 people,663 households, the population density was 81.5 inhabitants per square mile. There were 1,021 housing units at a density of 56.2 per square mile. The racial makeup of the town was 95. 3% White,0. 4% African American,1. 6% Native American,0. 4% Asian,0. 2% from other races, hispanic or Latino of any race were 1. 5% of the population. 27. 9% of all households were made up of individuals and 8. 3% had someone living alone who was 65 years of age or older, the average household size was 2.23 and the average family size was 2.72. The median age in the town was 45.8 years. 17. 4% of residents were under the age of 18,7. 4% were between the ages of 18 and 24, 24% were from 25 to 44, 36% were from 45 to 64, and 15. 1% were 65 years of age or older. The gender makeup of the town was 50. 6% male and 49. 4% female, as of the census of 2000, there were 1,370 people,574 households, and 388 families residing in the town. The population density was 75.3 people per square mile, there were 816 housing units at an average density of 44.9 per square mile. The racial makeup of the town was 95. 69% White,0. 58% African American,1. 46% Native American,0. 22% Asian,0. 07% Pacific Islander,0. 07% from other races, and 1. 90% from two or more races. Hispanic or Latino of any race were 0. 44% of the population,27. 0% of all households were made up of individuals and 8. 4% had someone living alone who was 65 years of age or older. The average household size was 2.39 and the family size was 2.89. In the town, the population was out with 24. 5% under the age of 18,6. 0% from 18 to 24,27. 0% from 25 to 44,27. 7% from 45 to 64. The median age was 41 years, for every 100 females there were 96.0 males. For every 100 females age 18 and over, there were 90.1 males, the median income for a household in the town was $34,808, and the median income for a family was $45,859
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Hancock County, Maine
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Hancock County is a county located in the U. S. state of Maine. As of the 2010 census, the population was 54,418, the county was incorporated on June 25,1789 and named for John Hancock, the first governor of the Commonwealth of Massachusetts. The Commissioners are Antonio Blasi, Steven Joy, Percy Brown, according to the U. S. Census Bureau, the county has a total area of 2,345 square miles, of which 1,587 square miles is land and 758 square miles is water. The population density was 33 people per square mile, there were 33,945 housing units at an average density of 21 per square mile. The racial makeup of the county was 97. 61% White,0. 25% Black or African American,0. 37% Native American,0. 38% Asian,0. 03% Pacific Islander,0. 20% from other races, and 1. 15% from two or more races. 0. 65% of the population were Hispanic or Latino of any race,27. 90% of all households were made up of individuals and 11. 60% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the family size was 2.81. In the county, the population was out with 22. 30% under the age of 18,7. 40% from 18 to 24,27. 50% from 25 to 44,26. 80% from 45 to 64. The median age was 41 years, for every 100 females there were 95.70 males. For every 100 females age 18 and over, there were 92.10 males, the median income for a household in the county was $35,811, and the median income for a family was $43,216. Males had an income of $30,461 versus $22,647 for females. The per capita income for the county was $19,809, about 7. 00% of families and 10. 20% of the population were below the poverty line, including 11. 90% of those under age 18 and 9. 50% of those age 65 or over. The 1990 Census counted 46,948, though the 1998 population estimate is 49,932.1 The gender division was 22,996 males,23,952 females in 1989. Of the 31,475 persons over 25 years old, 83% had a school degree or higher. Twenty-one percent had a degree or higher. As of the 2010 United States Census, there were 54,418 people,24,221 households, the population density was 34.3 inhabitants per square mile. There were 40,184 housing units at a density of 25.3 per square mile. The racial makeup of the county was 96. 9% white,0. 8% Asian,0. 4% American Indian,0. 4% black or African American,0. 3% from other races, and 1. 2% from two or more races
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Maine
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Maine is the northernmost state in the New England region of the northeastern United States. Maine is the 39th most extensive and the 41st most populous of the U. S. states and territories and it is bordered by New Hampshire to the west, the Atlantic Ocean to the east, and the Canadian provinces of New Brunswick and Quebec to the north. Maine is the easternmost state in the contiguous United States, and it is known for its jagged, rocky coastline, low, rolling mountains, heavily forested interior, and picturesque waterways, and also its seafood cuisine, especially clams and lobster. There is a continental climate throughout the state, even in areas such as its most populous city of Portland. For thousands of years, indigenous peoples were the inhabitants of the territory that is now Maine. At the time of European arrival in what is now Maine, the first European settlement in the area was by the French in 1604 on Saint Croix Island, by Pierre Dugua, Sieur de Mons. The first English settlement was the short-lived Popham Colony, established by the Plymouth Company in 1607, as Maine entered the 18th century, only a half dozen European settlements had survived. Loyalist and Patriot forces contended for Maines territory during the American Revolution, Maine was part of the Commonwealth of Massachusetts until 1820, when it voted to secede from Massachusetts to become an independent state. On March 15,1820, it was admitted to the Union as the 23rd state under the Missouri Compromise, there is no definitive explanation for the origin of the name Maine, but the most likely origin is the name given by early explorers after a province in France. Whatever the origin, the name was fixed for English settlers in 1665 when the English Kings Commissioners ordered that the Province of Maine be entered from then on in official records. The state legislature in 2001 adopted a resolution establishing Franco-American Day, other theories mention earlier places with similar names, or claim it is a nautical reference to the mainland. Attempts to uncover the history of the name of Maine began with James Sullivans 1795 History of the District of Maine. He made the allegation that the Province of Maine was a compliment to the queen of Charles I, Henrietta Maria. MAINE appears in the Domesday Book of 1086 in reference to the county of Dorset, the view generally held among British place name scholars is that Mayne in Dorset is Brythonic, corresponding to modern Welsh maen, plural main or meini. Some early spellings are, MAINE1086, MEINE1200, MEINES1204, mason had served with the Royal Navy in the Orkney Islands where the chief island is called Mainland, a possible name derivation for these English sailors. Initially, several tracts along the coast of New England were referred to as Main or Maine, Maine is the only state whose name has exactly one syllable. The original inhabitants of the territory that is now Maine were Algonquian-speaking Wabanaki peoples, including the Abenaki, Passamaquoddy, Maliseet and Penobscot, who had a loose confederacy. European contact with what is now called Maine started around 1200 CE when Norwegians interacted with the native Penobscot in present-day Hancock County, most likely through trade
33.
Family (biology)
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In biological classification, family is one of the eight major taxonomic ranks, it is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks above the rank of genus. In vernacular usage, a family may be named one of its common members, for example, walnuts and hickory trees belong to the family Juglandaceae. What does or does not belong to a family—or whether a family should be recognized at all—are proposed and determined by practicing taxonomists. There are no rules for describing or recognizing a family. Taxonomists often take different positions about descriptions of taxa, and there may be no broad consensus across the community for some time. Some described taxa are accepted broadly and quickly, but others only rarely, if at all, the naming of families is codified by various international codes. In zoological nomenclature, the names of animals end with the suffix -idae. The concept of rank at time was not yet settled, and in the preface to the Prodromus Magnol spoke of uniting his families into larger genera. Carolus Linnaeus used the word familia in his Philosophia botanica to denote groups of plants, trees, herbs, ferns, palms. He used this term only in the section of the book. In zoology, the family as an intermediate between order and genus was introduced by Pierre André Latreille in his Précis des caractères génériques des insectes. He used families in some but not in all his orders of insects, families can be used for evolutionary, palaeontological and generic studies because they are more stable than lower taxonomic levels such as genera and species
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Seafood
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Seafood is any form of sea life regarded as food by humans. Seafood prominently includes fish and shellfish, shellfish include various species of molluscs, crustaceans, and echinoderms. Historically, sea mammals such as whales and dolphins have been consumed as food, edible sea plants, such as some seaweeds and microalgae, are widely eaten as seafood around the world, especially in Asia. In North America, although not generally in the United Kingdom, for the sake of completeness, this article includes all edible aquatic life. The harvesting of seafood is usually known as fishing or hunting. Seafood is often distinguished from meat, although it is still animal and is excluded in a vegetarian diet. Seafood is an important source of protein in many diets around the world, most of the seafood harvest is consumed by humans, but a significant proportion is used as fish food to farm other fish or rear farm animals. Some seafoods are used as food for other plants, in these ways, seafoods are indirectly used to produce further food for human consumption. Products, such as oil and spirulina tablets are also extracted from seafoods. Some seafood is feed to fish, or used to feed domestic pets, such as cats. The harvesting, processing, and consuming of seafoods are ancient practices with archaeological evidence dating back well into the Paleolithic, isotopic analysis of the skeletal remains of Tianyuan man, a 40, 000-year-old modern human from eastern Asia, has shown that he regularly consumed freshwater fish. Archaeology features such as middens, discarded fish bones and cave paintings show that sea foods were important for survival. During this period, most people lived a lifestyle and were, of necessity. However, where there are examples of permanent settlements such as those at Lepenski Vir. The ancient river Nile was full of fish, fresh and dried fish were a food for much of the population. The Egyptians had implements and methods for fishing and these are illustrated in scenes, drawings. Some representations hint at fishing being pursued as a pastime, fishing scenes are rarely represented in ancient Greek culture, a reflection of the low social status of fishing. However, Oppian of Corycus, a Greek author wrote a treatise on sea fishing
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Spiny lobster
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Spiny lobsters, also known as langouste or rock lobsters, are a family of about 60 species of achelate crustaceans, in the Decapoda Reptantia. The furry lobsters were previously separated into a family of their own, the Synaxidae, the slipper lobsters are their next-closest relatives, and these two or three families make up the Achelata. Genera of spiny lobsters include Palinurus and a number of anagrams thereof, Panulirus, Linuparus, true lobsters have much smaller antennae and claws on the first three pairs of legs, with the first being particularly enlarged. Spiny lobsters have typically a slightly compressed carapace, lacking any lateral ridges and their antennae lack a scaphocerite, the flattened exopod of the antenna. This is fused to the epistome, the flagellum, at the top of the antenna, is stout, tapering, and very long. The ambulatory legs end in claws, the fossil record of spiny lobsters has been extended by the discovery in 1995 of a 110-million-year-old fossil near El Espiñal in Chiapas, Mexico. Spiny lobsters tend to live in crevices of rocks and coral reefs, only venturing out at night to seek snails, clams, sea-hares, crabs. Sometimes, they migrate in large groups in long files of lobsters across the sea floor. These lines may be more than 50 lobsters long, spiny lobsters navigate using the smell and taste of natural substances in the water that change in different parts of the ocean. It was recently discovered that spiny lobsters can also navigate by detecting the Earths magnetic field and they keep together by contact, using their long antennae. Potential predators may be deterred from eating spiny lobsters by a loud screech made by the antennae of the spiny lobsters rubbing against a part of the exoskeleton. Spiny lobsters usually exhibit the social habit of being together, however recent studies indicate that healthy lobsters move away from infected ones, leaving the diseased lobsters to fend for themselves. Like true lobsters, spiny lobsters are edible and are a significant food source, they are the biggest food export of the Bahamas. Many spiny lobsters produce rasping sounds to repel predators by rubbing the plectrum at the base of the spiny lobsters antennae against a file, the noise is produced by frictional vibrations - sticking and slipping, similar to rubber materials sliding against hard surfaces. While a number of insects use frictional vibration mechanisms to generate sound, the stridulating organ is present in all but three genera in the family, and its form can distinguish different species. An audio recording of the rasp of a spiny lobster Media related to Palinuridae at Wikimedia Commons Data related to Palinuridae at Wikispecies
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Slipper lobster
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Slipper lobsters are a family of about 90 species of achelate crustaceans, in the Decapoda Reptantia, found in all warm oceans and seas. They are not true lobsters, but are closely related to spiny lobsters. Slipper lobsters are instantly recognisable by their antennae, which project forward from the head as wide plates. All the species are edible, and some, such as the Moreton Bay bug, slipper lobsters have six segments in their heads and eight segments in the thorax, which are collectively covered in a thick carapace. The six segments of the abdomen each bear a pair of pleopods, the head segments bear various mouthparts and two pairs of antennae. The first antennae, or antennules, are held on a flexible stalk. The second antennae are the slipper lobsters most conspicuous feature, as they are expanded and flattened into large plates that extend forward from the animals head. There is considerable variation in size among species of slipper lobsters, the Mediterranean species Scyllarus pygmaeus is the smallest, growing to a maximum total length of 55 millimetres, and rarely more than 40 mm. The largest species, Scyllarides haanii, may reach 50 centimetres long, slipper lobsters are typically bottom dwellers of the continental shelves, found at depths of up to 500 metres. Slipper lobsters eat a variety of molluscs, including limpets, mussels and oysters, as well as crustaceans, polychaetes and they grow slowly and live to a considerable age. The most significant predators of slipper lobsters are bony fish, with the grey triggerfish being the most significant predator of Scyllarides latus in the Mediterranean Sea, after hatching out of their eggs, young slipper lobsters pass through around ten instars as phyllosoma larvae — leaf-like, planktonic zoeae. These ten or so stages last the part of a year. Almost nothing is known about the transition from stage to the adults. Although they are fished for wherever they are found, slipper lobsters have not been the subject of intense fishery as spiny lobsters or true lobsters. The methods used for catching slipper lobsters varies depending on the species ecology and those that prefer soft substrates, such as Thenus and Ibacus, are often caught by trawling, while those that prefer crevices, caves and reefs are usually caught by SCUBA divers. The global catch of slipper lobsters was reported in 1991 to be 2,100 tonnes, more recently, annual production has been around 5,000 tonnes, the majority of which is production of Thenus orientalis in Asia. A number of names have been applied to the family Scyllaridae. The most common of these is slipper lobster, followed by shovel-nosed lobster, spanish lobster is used for members of the genus Arctides, mitten lobster for Parribacus, and fan lobster for Evibacus and Ibacus
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Chela (organ)
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A chela /kˈiːlə/, also named claw, nipper, or pincer, is a pincer-like organ terminating certain limbs of some arthropods. The name comes from Greek through New Latin, legs bearing a chela are called chelipeds. Another name is claw because most chelae are curved and have a point like a claw
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Squat lobster
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Squat lobsters are dorsoventrally flattened crustaceans with long tails held curled beneath the cephalothorax. They are found in the two superfamilies Galatheoidea and Chirostyloidea, which part of the decapod infraorder Anomura, alongside groups including the hermit crabs. They are distributed worldwide in the oceans, and occur from near the surface to deep sea hydrothermal vents, more than 900 species have been described, in around 60 genera. Some species form aggregations, either on the sea floor or in the water column. The two main groups of squat lobsters share most features of their morphology and they resemble true lobsters in some ways, but are somewhat flattened dorsoventrally, and are typically smaller. Squat lobsters vary in length, from 90 millimetres in the case of Munidopsis aries, down to only a few millimetres in the case of Galathea intermedia. As in other decapod crustaceans, the body of a squat lobster may be divided into two regions, the cephalothorax, and the pleon or abdomen. The cephalothorax is made of 13 body segments, although the divisions are not obvious and are most easily inferred from the paired appendages, from front to back, these are, the two pairs of antennae, six pairs of mouthparts, five pairs of pereiopods. A pair of compound eyes also project on stalks from the front of the carapace, these are made up of ommatidia with square facets, many deep-sea species have reduced eyes, and reduced movement of the eyestalks. In the families Munididae and Galatheidae, there is often a row of setae close to the eyes, the most conspicuous appendages are the pereiopods, and the largest of these is the first pair. The following three pairs of pereiopods are somewhat smaller than the chelipeds and are without claws, but are otherwise similar, the fifth pair of pereiopods are much smaller than the preceding pairs, and are held inconspicuously under the carapace. They each end in a tiny chela, and are believed to be used for cleaning the body, especially the gills. The pleon is made up of six somites, each bearing a pair of pleopods, the first somite is narrower than the succeeding somites, and the last pair of pleopods are modified into uropods, which flank the telson. The pleon is usually curled under the thorax, such only the first three somites are visible from above. The form of the varies between the sexes. In females, the first one or two pairs are missing, while the pairs are uniramous, and have long setae. In males, the first two pairs are formed into gonopods, and are used to transfer the spermatophore to the female during mating, the remaining pleopods can be similar to those of the females, or reduced in size, or entirely absent. In both sexes, the uropods are biramous, the majority of squat lobsters are benthic, spending their lives on the sea-floor
39.
Reef lobster
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Reef lobsters, Enoplometopus, are a genus of small lobsters that live on reefs in the Indo-Pacific, Caribbean and warmer parts of the east Atlantic Ocean. Species of Enoplometopus occur from coral reefs at depths of less than 1 metre to rocky reefs at depths of 300 m and they are brightly coloured, with stripes, rings, or spots. They are typically red, orange, purplish and white. Reef lobsters are small, nocturnal, and very timid, the species can be distinguished by their colouration and morphology. As a result of their colours, they are popular in the aquarium trade. Due to uncertainty over the impact of potential threats, the majority are considered data deficient by the International Union for Conservation of Nature. Reef lobsters are distinguished from clawed lobsters by having full chelae only on the first pair of pereiopods, clawed lobsters have full claws on the first three pereiopods. Males, unlike those of nephropoid lobsters, have a lobe on the second pleopod. Reef lobsters have a shallow cervical groove while clawed lobsters have a deep cervical groove, although there is no fossil record of reef lobsters, there is some evidence that they may be related to the extinct genus Eryma which lived from the Permo-Triassic to the late Cretaceous. Milne Edwards,1862 Enoplometopus voigtmanni Türkay,1989
40.
Crayfish
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Some species are found in brooks and streams where there is running fresh water, while others thrive in swamps, ditches, and rice paddies. Most crayfish cannot tolerate polluted water, although species such as Procambarus clarkii are hardier. Crayfish feed on living and dead animals and plants, the name crayfish comes from the Old French word escrevisse. The word has been modified to crayfish by association with fish, the largely American variant crawfish is similarly derived. Some kinds of crayfish are known locally as lobsters, crawdads, mudbugs, the study of crayfish is called astacology. Exceptions include western rock lobster found on the west coast of Australia, the Tasmanian giant freshwater crayfish found only in Tasmania, in Singapore, the term crayfish typically refers to Thenus orientalis, a seawater crustacean from the slipper lobster family. True crayfish are not native to Singapore, but are found as pets, or as an invasive species in the many water catchment areas. The body of a crustacean, such as a crab, lobster. Each segment may possess one pair of appendages, although in various groups these may be reduced or missing, on average, crayfish grow to 17.5 centimetres in length, but some grow larger. Walking legs have a claw at the end. There are three families of crayfish, two in the Northern Hemisphere and one in the Southern Hemisphere, the Southern Hemisphere family Parastacidae lives in South America, Madagascar and Australasia, and is distinguished by the lack of the first pair of pleopods. Of the other two families, members of the Astacidae live in western Eurasia and western North America and members of the family Cambaridae live in eastern Asia, Madagascar has an endemic genus, Astacoides, containing seven species. Europe is home to seven species of crayfish in the genera Astacus and Austropotamobius, cambaroides is native to Japan and eastern mainland Asia. The greatest diversity of species is found in southeastern North America, with over 330 species in nine genera. A further genus of crayfish is found in the Pacific Northwest. Many crayfish are found in lowland areas where the water is abundant in calcium. Crayfish were introduced purposely into a few Arizona reservoirs and other bodies of water decades ago and they have since dispersed beyond those original sites. Australia has over 100 species in a dozen genera, in Australia, many of the better-known crayfish are of the genus Cherax, and include the marron from Western Australia, red-claw crayfish, common yabby and western yabby
. PMID 12208997.
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