1.
Crevalle jack
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The crevalle jack, Caranx hippos is a common species of large marine fish classified within the jack family, Carangidae. It is distinguishable from similar species by its body, fin colouration. It is one of the largest fish in the genus Caranx, growing to a known length of 124 cm. The crevalle jack inhabits both inshore and offshore waters to depths of around 350 m, predominantly over reefs, bays, lagoons, dietary shifts with both age, location and season have been demonstrated, which led some researchers to postulate the species is indiscriminant in its feeding habits. The crevalle jack reaches maturity at 55 cm in males and 66 cm in females, with spawning taking place year round, the larval and juvenile growth has been extensively studied, with the oldest known individual 17 years of age. The crevalle jack is an important species to commercial fisheries throughout its range and it is taken by a variety of netting methods, including purse nets, seines and gill nets, as well as hook-and-line methods. The crevalle jack is also a revered gamefish, taken both by lures and bait, the species is considered of good to poor quality table fare, and is sold fresh, frozen, or preserved, or as fishmeal or oil at market. The crevalle jack is closely related to both the Pacific crevalle jack and the longfin crevalle jack, the latter of which has been confused with the true crevalle jack until recently. The crevalle jack is classified within the genus Caranx, one of a number of known as the jacks or trevallies. Caranx itself is part of the jack and horse mackerel family Carangidae. The species belongs to what William Smith-Vaniz and Ken Carpenter refer to as the Caranx hippos complex, the crevalle jack was the first species of its genus to be scientifically described and named, and is also the type species of the genus Caranx. It was described and named in 1766 by the famed Swedish taxonomist Carl Linnaeus, based on the specimen taken off the coast of the Carolinas. He named the species Scomber hippos, placing it in the mackerel genus Scomber, the specific epithet means horse in Latin, with Scomber hippos literally translating in English as horse mackerel, which has become a common name for many species of carangid. As the state of fish taxonomy progressed, the species was transferred to both Caranx and Carangus, with the name Caranx hippos now accepted, there has been extensive discussion in the scientific literature regarding the possible conspecifity of the Pacific crevalle jack, Caranx caninus, with Caranx hippos. Arguments ranged from the species being conspecific, subspecific or as individual species and this led to the creation of two trinomial names, Caranx hippos hippos and Caranx hippos tropicus. The former was an attempt to separate the subspecies on each side of the Americas, the species most often used common name, crevalle jack is based on the word cavalla, an earlier word used for the jacks. Other names include common jack, black-tailed trevally, couvalli jack, black cavalli, yellow cavalli and a host of generic names, such as horse mackerel and crevalle. The crevalle jack is one of the largest members of Caranx, growing to a maximum length of 125 cm
2.
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
3.
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
4.
Chordate
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Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland
5.
Actinopterygii
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Actinopterygii /ˌæktᵻnˌɒptəˈrɪdʒi. aɪ/, or the ray-finned fishes, constitute a class or subclass of the bony fishes. These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, numerically, actinopterygians are the dominant class of vertebrates, comprising nearly 99% of the over 30,000 species of fish. They are ubiquitous throughout freshwater and marine environments from the sea to the highest mountain streams. Extant species can range in size from Paedocypris, at 8 mm, to the ocean sunfish, at 2,300 kg. Ray-finned fishes occur in variant forms. The main features of a typical ray-finned fish are shown in the diagram at the left. In nearly all ray-finned fish, the sexes are separate, development then proceeds with a free-swimming larval stage. However other patterns of ontogeny exist, with one of the commonest being sequential hermaphroditism, in most cases this involves protogyny, fish starting life as females and converting to males at some stage, triggered by some internal or external factor. This may be advantageous as females become less prolific as they age while male fecundity increases with age, protandry, where a fish converts from male to female, is much less common than protogyny. Most families use external rather than internal fertilization, of the oviparous teleosts, most do not provide parental care. Viviparity is relatively rare and is found in about 6% of teleost species, male territoriality preadapts a species for evolving male parental care. There are a few examples of fish that self-fertilise, the mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to the habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below 19 °C and can fertilise eggs that are spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred, the earliest known fossil actinopterygiian is Andreolepis hedei, dating back 420 million years. Remains have been found in Russia, Sweden, and Estonia, actinopterygians are divided into the subclasses Chondrostei and Neopterygii. The Neopterygii, in turn, are divided into the infraclasses Holostei and Teleostei, during the Mesozoic and Cenozoic the teleosts in particular diversified widely, and as a result, 96% of all known fish species are teleosts. The cladogram shows the groups of actinopterygians and their relationship to the terrestrial vertebrates that evolved from a related group of fish
6.
Caranx
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Caranx is a genus of tropical to subtropical marine fishes in the jack family Carangidae, commonly known as jacks, trevallies and kingfishes. They are moderate- to large-sized, deep-bodied fishes which are distinguished from other genera by specific gill raker, fin ray. The genus is represented in the Pacific, Indian and Atlantic Oceans, all species are powerful predators, taking a variety of fish, crustaceans and cephalopods, while they in turn are prey to larger pelagic fishes and sharks. A number of fish in the genus have a reputation as powerful gamefish and are sought by anglers. They often make up high amounts of the catch in various fisheries, the genus Caranx is one of 30 currently recognised genera of fish in the jack and horse mackerel family Carangidae, which are perciform fishes in the suborder Percoidei. The species has long placed in the subfamily Caranginae, with modern molecular and genetic studies indicating this subdivision is acceptable. Phylogenetically, the genus of Gnathanodon is most closely related to Caranx. The early days of carangid taxonomy had over 100 species designated as members of the genus, most of which were synonyms, Caranx took authority over these other genera names due to its prior description, rendering the rest as invalid junior synonyms. The fish in the genus are referred to as jacks. Like the genus Carangoides, the word Caranx is derived from the French carangue, fossils mostly consist of otoliths, with the bony skeletal material rarely preserved. In their general body profile, they are similar to a number of other genera, having a deep. The dorsal fin is in two parts, the first consisting of 8 spines and the second of one spine and between 16 and 25 soft rays, the anal fin has one or two detached anterior spines, with 1 spine and between 14 and 19 soft rays. The caudal fin is strongly forked, all species have moderate to very strong scutes on the posterior section of their lateral lines. All members of Caranx are all generally silver to grey in colour, with shades of blue or green dorsally, fin colours range from hyaline to yellow, blue and black. Species from the genus Caranx are distributed throughout the tropical and subtropical waters of the world, inhabiting the Atlantic, Pacific and Indian Oceans. They are known from the coasts of all continents and islands within this range, most species are coastal fish, and very few venture into waters further offshore than the continental shelf, and these species are generally moved by ocean currents. They inhabit a range of environments including sand flats, bays, lagoons, reefs, sea mounts, most species are demersal, or bottom dwelling, in nature, while others are pelagic, moving long distances in the upper water column. The level of information known about each species in Caranx is generally related to how important they are commercially
7.
Golden trevally
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The golden trevally, Gnathanodon speciosus, is a species of large marine fish classified in the jack and horse mackerel family Carangidae, and the only member of the genus Gnathanodon. The species predominantly occupies inshore waters where it inhabits both reef and sandy substrates and it is known to grow to 120 cm in length and 15 kg in weight. The golden trevally schools as a juvenile, often closely following larger objects including sharks, the species uses its protractile jaws to suck out prey from the sand or reef, and consumes a variety of fish, crustaceans and molluscs. Spawning aggregations gather at night at different times of the year throughout its range, the golden trevally is a popular gamefish, taken by bait, lure, fly and also spear throughout its range. Several Asian countries currently farm the fish in caged aquaculture, due to their brilliant colouration, juveniles are popular in marine aquaria. The species was described for the first time by the Swedish naturalist Peter Forsskål in 1775. Forsskål referred the species to the genus Scomber, where many jacks were placed before the recognition of the family Carangidae, consequently, authorities regard Scomber rim as a junior synonym. Forsskåls description was based on an individual from the Red Sea off Jeddah, the holotype has since been lost and a neotype was invalidly designated by Ronald Fricke in 1999. The specific epithet speciosus is Latin for beautiful, the species was transferred to Caranx before the Dutch ichthyologist Pieter Bleeker placed it in its own genus Gnathanodon, with this name derived from the Latin for toothless jaws. In addition to Forsskåls naming, seven other names have been ascribed to the fish. The species common names refer to its appearance with golden trevally, banded trevally. In Hawaii the species is referred to as the yellow ulua or papio, a study on the phylogenetic relationships of the Carangidae-based primarily on osteology by Soko Gushiken found that Gnathanodon is closely related to and forms a monophyletic group with Caranx. The species has yet to be included in any molecular phylogeny study of the family, the golden trevally is widely distributed throughout the tropical and subtropical waters of the Indian and Pacific Oceans. In the Indian Ocean, the species is distributed from South Africa along the east African coastline, including the Red Sea and its distribution extends east along the Indian and South East Asian coastlines, and south through Indonesia and northern Australia. Golden trevally are recorded from many Indian Ocean islands including Madagascar, The Seychelles, in the Pacific, the species is spread throughout the South East Asian and Indonesian archipelago north mainland China and Japan and south to eastern Australia and New Zealand. Golden trevally have been recorded from many central Pacific Islands, including Hawaii, here its range extends from the Gulf of California in the north to Colombia in the south. The golden trevally predominantly occupies inshore waters of varying substrate, although is known to occur on continental shelf reefs in Australia. In coastal areas the species inhabits rocky and coral reefs as well as open sand flats where it forages for food, a systematic study in northern Australia indicated it to be one of the only species to be approximately equally distributed in both reef and soft-bottom habitats
8.
Pacific Ocean
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The Pacific Ocean is the largest and deepest of the Earths oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by Asia and Australia in the west, the Mariana Trench in the western North Pacific is the deepest point in the world, reaching a depth of 10,911 metres. Both the center of the Water Hemisphere and the Western Hemisphere are in the Pacific Ocean, the oceans current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favourable winds on reaching the ocean. He called it Mar Pacífico, which in both Portuguese and Spanish means peaceful sea, important human migrations occurred in the Pacific in prehistoric times. Long-distance trade developed all along the coast from Mozambique to Japan, trade, and therefore knowledge, extended to the Indonesian islands but apparently not Australia. By at least 878 when there was a significant Islamic settlement in Canton much of trade was controlled by Arabs or Muslims. In 219 BC Xu Fu sailed out into the Pacific searching for the elixir of immortality, from 1404 to 1433 Zheng He led expeditions into the Indian Ocean. The east side of the ocean was discovered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and he named it Mar del Sur because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. Later, Portuguese explorer Ferdinand Magellan sailed the Pacific East to West on a Castilian expedition of world circumnavigation starting in 1519, Magellan called the ocean Pacífico because, after sailing through the stormy seas off Cape Horn, the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until the eighteenth century, sailing around and east of the Moluccas, between 1525 and 1527, Portuguese expeditions discovered the Caroline Islands, the Aru Islands, and Papua New Guinea. In 1542–43 the Portuguese also reached Japan, in 1564, five Spanish ships consisting of 379 explorers crossed the ocean from Mexico led by Miguel López de Legazpi and sailed to the Philippines and Mariana Islands. The Manila galleons operated for two and a half centuries linking Manila and Acapulco, in one of the longest trade routes in history, Spanish expeditions also discovered Tuvalu, the Marquesas, the Cook Islands, the Solomon Islands, and the Admiralty Islands in the South Pacific. In the 16th and 17th century Spain considered the Pacific Ocean a Mare clausum—a sea closed to other naval powers, as the only known entrance from the Atlantic the Strait of Magellan was at times patrolled by fleets sent to prevent entrance of non-Spanish ships. On the western end of the Pacific Ocean the Dutch threatened the Spanish Philippines, Spain also sent expeditions to the Pacific Northwest reaching Vancouver Island in southern Canada, and Alaska. The French explored and settled Polynesia, and the British made three voyages with James Cook to the South Pacific and Australia, Hawaii, and the North American Pacific Northwest, one of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794. It sailed vast areas of the Pacific, from Cape Horn to Alaska, Guam and the Philippines, New Zealand, Australia, and the South Pacific. Growing imperialism during the 19th century resulted in the occupation of much of Oceania by other European powers, and later, Japan, in Oceania, France got a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853 respectively. After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro managed to negotiate an incorporation of the island into Chile with native Rapanui in 1888, by occupying Easter Island, Chile joined the imperial nations
9.
Reef
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A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water. Reefs may be up to 261 feet below the surface, artificial reefs such as shipwrecks are sometimes created to enhance physical complexity on generally featureless sand bottoms in order to attract a diverse assemblage of organisms, especially fish. There is a variety of reef types, including oyster reefs. These biotic reef types take on additional names depending upon how the reef lies in relation to the land, Reef types include fringing reef, barrier reefs, as well as atolls. A fringing reef is a reef that is attached to an island, a barrier reef forms a calcareous barrier around an island resulting in a lagoon between the shore and the reef. An atoll is a reef with no land present. The reef front is a high energy locale whereas the internal lagoon will be at an energy with fine grained sediments. One useful definition distinguishes reefs from mounds as follows, reefs are held up by a macroscopic skeletal framework. Coral reefs are an excellent example of this kind, corals and calcareous algae grow on top of one another and form a three-dimensional framework that is modified in various ways by other organisms and inorganic processes. By contrast, mounds lack a macroscopic skeletal framework, mounds are built by microorganisms or by organisms that dont grow a skeletal framework. A microbial mound might be built exclusively or primarily by cyanobacteria, excellent examples of biostromes formed by cyanobacteria occur in the Great Salt Lake of Utah, and in Shark Bay, Western Australia. Cyanobacteria do not have skeletons and individuals are microscopic, cyanobacteria encourage the precipitation or accumulation of calcium carbonate and can produce distinct sediment bodies in composition that have relief on the seafloor. Cyanobacterial mounds were most abundant before the evolution of shelly macroscopic organisms, bryozoans and crinoids, common contributors to marine sediments during the Mississippian, produced a very different kind of mound. Bryozoans are small and the skeletons of crinoids disintegrate, however, bryozoan and crinoid meadows can persist over time and produce compositionally distinct bodies of sediment with depositional relief. The Proterozoic Belt Supergroup contains evidence of microbial mat and dome structures similar to stromatolite reef complexes. Ancient reefs buried within stratigraphic sections are of considerable interest to geologists because they provide information about the location in Earths history. Corals, including some major extinct groups Rugosa and Tabulata, have been important reef builders through much of the Phanerozoic since the Ordovician Period. However, other groups, such as calcifying algae, especially members of the red algae Rhodophyta
10.
Extinction
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In biology and ecology, extinction is the end of an organism or of a group of organisms, normally a species. The moment of extinction is considered to be the death of the last individual of the species, although the capacity to breed. Because a species range may be very large, determining this moment is difficult. This difficulty leads to such as Lazarus taxa, where a species presumed extinct abruptly reappears after a period of apparent absence. More than 99 percent of all species, amounting to five billion species. Estimates on the number of Earths current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described, the relationship between animals and their ecological niches has been firmly established. Mass extinctions are relatively rare events, however, isolated extinctions are quite common, only recently have extinctions been recorded and scientists have become alarmed at the current high rate of extinctions. Most species that become extinct are never scientifically documented, some scientists estimate that up to half of presently existing plant and animal species may become extinct by 2100. A dagger symbol next to a name is often used to indicate its extinction. A species is extinct when the last existing member dies, Extinction therefore becomes a certainty when there are no surviving individuals that can reproduce and create a new generation. Pinpointing the extinction of a species requires a definition of that species. If it is to be declared extinct, the species in question must be distinguishable from any ancestor or daughter species. Extinction of a plays a key role in the punctuated equilibrium hypothesis of Stephen Jay Gould. In ecology, extinction is often used informally to refer to local extinction, in which a species ceases to exist in the area of study. This phenomenon is known as extirpation. Local extinctions may be followed by a replacement of the species taken from other locations, species which are not extinct are termed extant. Those that are extant but threatened by extinction are referred to as threatened or endangered species, currently an important aspect of extinction is human attempts to preserve critically endangered species
11.
Miocene
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The Miocene is the first geological epoch of the Neogene Period and extends from about 23.03 to 5.333 million years ago. The Miocene was named by Sir Charles Lyell and its name comes from the Greek words μείων and καινός and means less recent because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene Epoch and is followed by the Pliocene Epoch, the earth went from the Oligocene through the Miocene and into the Pliocene, with the climate slowly cooling towards a series of ice ages. The Miocene boundaries are not marked by a single distinct global event, the apes arose and diversified during the Miocene, becoming widespread in the Old World. By the end of this epoch, the ancestors of humans had split away from the ancestors of the chimpanzees to follow their own evolutionary path, as in the Oligocene before it, grasslands continued to expand and forests to dwindle in extent. In the Miocene seas, kelp forests made their first appearance, the plants and animals of the Miocene were fairly modern. The Miocene faunal stages from youngest to oldest are typically named according to the International Commission on Stratigraphy, Two subdivisions each form the lower, middle, continents continued to drift toward their present positions. Mountain building took place in western North America, Europe, both continental and marine Miocene deposits are common worldwide with marine outcrops common near modern shorelines. Well studied continental exposures occur in the North American Great Plains, India continued to collide with Asia, creating dramatic new mountain ranges. The Tethys Seaway continued to shrink and then disappeared as Africa collided with Eurasia in the Turkish–Arabian region between 19 and 12 Ma. The subsequent uplift of mountains in the western Mediterranean region and a fall in sea levels combined to cause a temporary drying up of the Mediterranean Sea near the end of the Miocene. The global trend was towards increasing aridity caused primarily by global cooling reducing the ability of the atmosphere to absorb moisture, climates remained moderately warm, although the slow global cooling that eventually led to the Pleistocene glaciations continued. Although a long-term cooling trend was well underway, there is evidence of a period during the Miocene when the global climate rivalled that of the Oligocene. The Miocene warming began 21 million years ago and continued until 14 million years ago, by 8 million years ago, temperatures dropped sharply once again, and the Antarctic ice sheet was already approaching its present-day size and thickness. Greenland may have begun to have large glaciers as early as 7 to 8 million years ago, life during the Miocene Epoch was mostly supported by the two newly formed biomes, kelp forests and grasslands. This allows for more grazers, such as horses, rhinoceroses, ninety five percent of modern plants existed by the end of this epoch. The higher organic content and water retention of the deeper and richer grassland soils, with long term burial of carbon in sediments, produced a carbon and this, combined with higher surface albedo and lower evapotranspiration of grassland, contributed to a cooler, drier climate. The expansion of grasslands and radiations among terrestrial herbivores correlates to fluctuations in CO2
12.
Oligocene
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The Oligocene is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present. As with other geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start. The name Oligocene comes from the Ancient Greek ὀλίγος and καινός, the Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period, the Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included an expansion of grasslands. By contrast, the Oligocene–Miocene boundary is not set at an easily identified worldwide event, Oligocene faunal stages from youngest to oldest are, The Paleogene Period general temperature decline is interrupted by an Oligocene 7-million-year stepwise climate change. A deeper 8.2 °C,400, 000-year temperature depression leads the 2 °C, the stepwise climate change began 32.5 Ma and lasted through to 25.5 Ma, as depicted in the PaleoTemps chart. The Oligocene climate change was a increase in ice volume. The 7-million-year depression abruptly terminated within 1–2 million years of the La Garita Caldera eruption at 28–26 Ma, a deep 400, 000-year glaciated Oligocene Miocene boundary event is recorded at McMurdo Sound and King George Island. During this epoch, the continued to drift toward their present positions. Antarctica became more isolated and finally developed an ice cap, a brief marine incursion marks the early Oligocene in Europe. Marine fossils from the Oligocene are rare in North America, there appears to have been a land bridge in the early Oligocene between North America and Europe, since the faunas of the two regions are very similar. Sometime during the Oligocene, South America was finally detached from Antarctica and it also allowed the Antarctic Circumpolar Current to flow, rapidly cooling the Antarctic continent. Angiosperms continued their expansion throughout the world as tropical and sub-tropical forests were replaced by deciduous forests. Open plains and deserts became more common and grasses expanded from their habitat in the Eocene moving out into open tracts. However, even at the end of the period, grass was not quite enough for modern savannas. In North America, subtropical species dominated with cashews and lychee trees present, and temperate trees such as roses, beeches, the legumes spread, while sedges, bulrushes, and ferns continued their ascent. Even more open landscapes allowed animals to grow to larger sizes than they had earlier in the Paleocene epoch 30 million years earlier, marine faunas became fairly modern, as did terrestrial vertebrate fauna on the northern continents
