Russia the Russian Federation, is a transcontinental country in Eastern Europe and North Asia. At 17,125,200 square kilometres, Russia is by far or by a considerable margin the largest country in the world by area, covering more than one-eighth of the Earth's inhabited land area, the ninth most populous, with about 146.77 million people as of 2019, including Crimea. About 77 % of the population live in the European part of the country. Russia's capital, Moscow, is one of the largest cities in the world and the second largest city in Europe. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a wide range of environments and landforms. From northwest to southeast, Russia shares land borders with Norway, Estonia, Latvia and Poland, Ukraine, Azerbaijan, China and North Korea, it shares maritime borders with Japan by the Sea of Okhotsk and the U. S. state of Alaska across the Bering Strait. However, Russia recognises two more countries that border it, Abkhazia and South Ossetia, both of which are internationally recognized as parts of Georgia.
The East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, the medieval state of Rus arose in the 9th century. In 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus' disintegrated into a number of smaller states; the Grand Duchy of Moscow reunified the surrounding Russian principalities and achieved independence from the Golden Horde. By the 18th century, the nation had expanded through conquest and exploration to become the Russian Empire, the third largest empire in history, stretching from Poland on the west to Alaska on the east. Following the Russian Revolution, the Russian Soviet Federative Socialist Republic became the largest and leading constituent of the Union of Soviet Socialist Republics, the world's first constitutionally socialist state; the Soviet Union played a decisive role in the Allied victory in World War II, emerged as a recognized superpower and rival to the United States during the Cold War.
The Soviet era saw some of the most significant technological achievements of the 20th century, including the world's first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the world's second largest economy, largest standing military in the world and the largest stockpile of weapons of mass destruction. Following the dissolution of the Soviet Union in 1991, twelve independent republics emerged from the USSR: Russia, Belarus, Uzbekistan, Azerbaijan, Kyrgyzstan, Tajikistan and the Baltic states regained independence: Estonia, Lithuania, it is governed as a federal semi-presidential republic. Russia's economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2018. Russia's extensive mineral and energy resources are the largest such reserves in the world, making it one of the leading producers of oil and natural gas globally; the country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction.
Russia is a great power as well as a regional power and has been characterised as a potential superpower. It is a permanent member of the United Nations Security Council and an active global partner of ASEAN, as well as a member of the Shanghai Cooperation Organisation, the G20, the Council of Europe, the Asia-Pacific Economic Cooperation, the Organization for Security and Co-operation in Europe, the World Trade Organization, as well as being the leading member of the Commonwealth of Independent States, the Collective Security Treaty Organization and one of the five members of the Eurasian Economic Union, along with Armenia, Belarus and Kyrgyzstan; the name Russia is derived from Rus', a medieval state populated by the East Slavs. However, this proper name became more prominent in the history, the country was called by its inhabitants "Русская Земля", which can be translated as "Russian Land" or "Land of Rus'". In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus' by modern historiography.
The name Rus itself comes from the early medieval Rus' people, Swedish merchants and warriors who relocated from across the Baltic Sea and founded a state centered on Novgorod that became Kievan Rus. An old Latin version of the name Rus' was Ruthenia applied to the western and southern regions of Rus' that were adjacent to Catholic Europe; the current name of the country, Россия, comes from the Byzantine Greek designation of the Rus', Ρωσσία Rossía—spelled Ρωσία in Modern Greek. The standard way to refer to citizens of Russia is rossiyane in Russian. There are two Russian words which are commonly
South Australia is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of 983,482 square kilometres, it is the fourth-largest of Australia's states and territories by area, fifth largest by population, it has a total of 1.7 million people, its population is the second most centralised in Australia, after Western Australia, with more than 77 percent of South Australians living in the capital, Adelaide, or its environs. Other population centres in the state are small. South Australia shares borders with all of the other mainland states, with the Northern Territory; the state comprises less than 8 percent of the Australian population and ranks fifth in population among the six states and two territories. The majority of its people reside in greater Metropolitan Adelaide. Most of the remainder are settled in fertile areas along River Murray; the state's colonial origins are unique in Australia as a settled, planned British province, rather than as a convict settlement.
Colonial government commenced on 28 December 1836, when the members of the council were sworn in near the Old Gum Tree. As with the rest of the continent, the region had been long occupied by Aboriginal peoples, who were organised into numerous tribes and languages; the South Australian Company established a temporary settlement at Kingscote, Kangaroo Island, on 26 July 1836, five months before Adelaide was founded. The guiding principle behind settlement was that of systematic colonisation, a theory espoused by Edward Gibbon Wakefield, employed by the New Zealand Company; the goal was to establish the province as a centre of civilisation for free immigrants, promising civil liberties and religious tolerance. Although its history is marked by economic hardship, South Australia has remained politically innovative and culturally vibrant. Today, it is known for numerous cultural festivals; the state's economy is dominated by the agricultural and mining industries. Evidence of human activity in South Australia dates back as far as 20,000 years, with flint mining activity and rock art in the Koonalda Cave on the Nullarbor Plain.
In addition wooden spears and tools were made in an area now covered in peat bog in the South East. Kangaroo Island was inhabited; the first recorded European sighting of the South Australian coast was in 1627 when the Dutch ship the Gulden Zeepaert, captained by François Thijssen and mapped a section of the coastline as far east as the Nuyts Archipelago. Thijssen named the whole of the country eastward of the Leeuwin "Nuyts Land", after a distinguished passenger on board; the coastline of South Australia was first mapped by Matthew Flinders and Nicolas Baudin in 1802, excepting the inlet named the Port Adelaide River, first discovered in 1831 by Captain Collet Barker and accurately charted in 1836–37 by Colonel William Light, leader of the South Australian Colonization Commissioners"First Expedition' and first Surveyor-General of South Australia. The land which now forms the state of South Australia was claimed for Britain in 1788 as part of the colony of New South Wales. Although the new colony included two-thirds of the continent, early settlements were all on the eastern coast and only a few intrepid explorers ventured this far west.
It took more than forty years before any serious proposal to establish settlements in the south-western portion of New South Wales were put forward. On 15 August 1834, the British Parliament passed the South Australia Act 1834, which empowered His Majesty to erect and establish a province or provinces in southern Australia; the act stated that the land between 132° and 141° east longitude and from 26° south latitude to the southern ocean would be allotted to the colony, it would be convict-free. In contrast to the rest of Australia, terra nullius did not apply to the new province; the Letters Patent, which used the enabling provisions of the South Australia Act 1834 to fix the boundaries of the Province of South Australia, provided that "nothing in those our Letters Patent shall affect or be construed to affect the rights of any Aboriginal Natives of the said Province to the actual occupation and enjoyment in their own Persons or in the Persons of their Descendants of any Lands therein now occupied or enjoyed by such Natives."
Although the patent guaranteed land rights under force of law for the indigenous inhabitants it was ignored by the South Australian Company authorities and squatters. Survey was required before settlement of the province, the Colonization Commissioners for South Australia appointed William Light as the leader of its'First Expedition', tasked with examining 1500 miles of the South Australian coastline and selecting the best site for the capital, with planning and surveying the site of the city into one-acre Town Sections and its surrounds into 134-acre Country Sections. Eager to commence the establishment of their whale and seal fisheries, the South Australian Company sought, obtained, the Commissioners' permission to send Company ships to South Australia, in advance of the surveys and ahead of the Commissioners' colonists; the Company's settlement of seven vessels and 636 people was temporarily made at Kingscote on Kangaroo Island, until
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 Pliocene; some geologists assert that the Neogene cannot be delineated from the modern geological period, the Quaternary. The term "Neogene" was coined in 1853 by the Austrian palaeontologist Moritz Hörnes. During this period and birds continued to evolve into modern forms, while other groups of life remained unchanged. 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 warm ocean currents from the Pacific to the Atlantic Ocean, leaving only the Gulf Stream to transfer heat to the Arctic Ocean; the global climate cooled over the course of the Neogene, culminating in a series of continental glaciations in the Quaternary Period that follows.
In ICS terminology, from upper to lower: The Pliocene Epoch is subdivided into 2 ages: Piacenzian Age, preceded by Zanclean AgeThe Miocene Epoch is subdivided into 6 ages: Messinian Age, preceded by Tortonian Age Serravallian Age Langhian Age Burdigalian Age Aquitanian AgeIn different geophysical regions of the world, other regional names are used for the same or overlapping ages and other timeline subdivisions. The terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period; the continents in the Neogene were close to their current positions. The Isthmus of Panama formed, connecting South America; the Indian subcontinent continued 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, 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 early part of the period, while the amphibians known as Allocaudata disappeared at the end. Mammals and birds continued to be the dominant terrestrial vertebrates, took many forms as they adapted to various habitats; the first hominins, the ancestors of humans, may have appeared in southern Europe and migrated into Africa. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones and grasslands replaced many forests. Grasses therefore diversified, herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses and bison. Eucalyptus fossil leaves occur in the Miocene of New Zealand, where the genus is not native today, but have been introduced from Australia; the Neogene traditionally ended at the end of the Pliocene Epoch, just before the older definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to include ongoing geological time in the Neogene, while others insist the Quaternary to be a separate period of distinctly different record.
The somewhat confusing terminology and disagreement amongst geologists on where to draw what hierarchical boundaries is due to the comparatively fine divisibility of time units as time approaches the present, due to geological preservation that causes the youngest sedimentary geological record to be preserved over a much larger area and to reflect many more environments than the older geological record. By dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more 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 beginning date of 2.58 Ma, namely the start of the Gelasian Stage. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs; the International Union for Quaternary Research counterproposed that the Neogene and the Pliocene end at 2.58 Ma, that the Gelasian be transferred to the Pleistocene, the Quaternary be recognized as the third period in the Cenozoic, citing key changes in Earth's climate and biota that occurred 2.58 Ma and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary.
In 2006 ICS and INQUA reached a compromise that made Quaternary a subera, subdividing Cenozoic into the old classical Tertiary and Quaternary, a compromise, rejected by International Union of Geological Sciences because it split both Neogene and Pliocene in two. Following formal discussions at the 2008 International Geological Congress in Oslo, the ICS decided in May 2009 to make the Quaternary the youngest period of the Cenozoic Era with its base at 2.58 Mya and including the Gelasian age, considered part of the Neogene Period and Pliocene Epoch. Thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. "Digital Atlas of Neogene Life for the Southeastern United States". San Jose State University. Archived from the original on 2013-04-23. Retrieved 21 September 2018
Ukraine, sometimes called the Ukraine, is a country in Eastern Europe. Excluding Crimea, Ukraine has a population of about 42.5 million, making it the 32nd most populous country in the world. Its capital and largest city is Kiev. Ukrainian is the official language and its alphabet is Cyrillic; the dominant religions in the country are Greek Catholicism. Ukraine is in a territorial dispute with Russia over the Crimean Peninsula, which Russia annexed in 2014. Including Crimea, Ukraine has an area of 603,628 km2, making it the largest country within Europe and the 46th largest country in the world; the territory of modern Ukraine has been inhabited since 32,000 BC. During the Middle Ages, the area was a key centre of East Slavic culture, with the powerful state of Kievan Rus' forming the basis of Ukrainian identity. Following its fragmentation in the 13th century, the territory was contested and divided by a variety of powers, including Lithuania, Austria-Hungary, the Ottoman Empire and Russia. A Cossack republic emerged and prospered during the 17th and 18th centuries, but its territory was split between Poland and the Russian Empire, merged into the Russian-dominated Soviet Union in the late 1940s as the Ukrainian Soviet Socialist Republic.
In 1991 Ukraine gained its independence from the Soviet Union in the aftermath of its dissolution at the end of the Cold War. Before its independence, Ukraine was referred to in English as "The Ukraine", but most sources have since moved to drop "the" from the name of Ukraine in all uses. Following its independence, Ukraine declared itself a neutral state. In 2013, after the government of President Viktor Yanukovych had decided to suspend the Ukraine-European Union Association Agreement and seek closer economic ties with Russia, a several-months-long wave of demonstrations and protests known as the Euromaidan began, which escalated into the 2014 Ukrainian revolution that led to the overthrow of Yanukovych and the establishment of a new government; these events formed the background for the annexation of Crimea by Russia in March 2014, the War in Donbass in April 2014. On 1 January 2016, Ukraine applied the economic component of the Deep and Comprehensive Free Trade Area with the European Union.
Ukraine is ranks 88th on the Human Development Index. As of 2018, Ukraine has the second lowest GDP per capita in Europe. At US$40, it has the lowest median wealth per adult in the world, it suffers from a high poverty rate and severe corruption. However, because of its extensive fertile farmlands, Ukraine is one of the world's largest grain exporters. Ukraine maintains the second-largest military in Europe after that of Russia; the country is home to a multi-ethnic population, 77.8 percent of whom are Ukrainians, followed by a large Russian minority, as well as Georgians, Belarusians, Crimean Tatars, Jews and Hungarians. Ukraine is a unitary republic under a semi-presidential system with separate powers: legislative and judicial branches; the country is a member of the United Nations, the Council of Europe, the OSCE, the GUAM organization, one of the founding states of the Commonwealth of Independent States. There are different hypotheses as to the etymology of the name Ukraine. According to the older widespread hypothesis, it means "borderland", while some more recent linguistic studies claim a different meaning: "homeland" or "region, country"."The Ukraine" used to be the usual form in English, but since the Declaration of Independence of Ukraine, "the Ukraine" has become less common in the English-speaking world, style-guides recommend not using the definite article.
"The Ukraine" now implies disregard for the country's sovereignty, according to U. S. ambassador William Taylor. The Ukrainian position is that the usage of "'The Ukraine' is incorrect both grammatically and politically." Neanderthal settlement in Ukraine is seen in the Molodova archaeological sites which include a mammoth bone dwelling. The territory is considered to be the location for the human domestication of the horse. Modern human settlement in Ukraine and its vicinity dates back to 32,000 BC, with evidence of the Gravettian culture in the Crimean Mountains. By 4,500 BC, the Neolithic Cucuteni–Trypillia culture flourished in wide areas of modern Ukraine including Trypillia and the entire Dnieper-Dniester region. During the Iron Age, the land was inhabited by Cimmerians and Sarmatians. Between 700 BC and 200 BC it was Scythia. Beginning in the sixth century BC, colonies of Ancient Greece, Ancient Rome and the Byzantine Empire, such as Tyras and Chersonesus, were founded on the northeastern shore of the Black Sea.
These colonies thrived well into the 6th century AD. The Goths stayed in the area but came under the sway of the Huns from the 370s AD. In the 7th century AD, the territory of eastern Ukraine was the centre of Old Great Bulgaria. At the end of the century, the majority of Bulgar tribes migrated in different directions, the Khazars took over much of the land. In the 5th and 6th centuries, the Antes were located in the territory of; the Antes were the ancestors of Ukrainians: White Croats, Polans, Dulebes and Tiverians. Migrations from Ukraine throughout the Balkans established many Southern Slavic nations. Northern migrations, reaching to the Ilmen l
Cnidaria is a phylum under Kingdom Animalia containing over 11,000 species of animals found in aquatic environments: they are predominantly marine. Their distinguishing feature is cnidocytes, specialized cells that they use for capturing prey, their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are one cell thick. They have two basic body forms: swimming medusae and sessile polyps, both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single body cavity that are used for digestion and respiration. Many cnidarian species produce colonies that are single organisms composed of medusa-like or polyp-like zooids, or both. Cnidarians' activities are coordinated by simple receptors. Several free-swimming species of Cubozoa and Scyphozoa possess balance-sensing statocysts, some have simple eyes. Not all cnidarians reproduce sexually, with many species having complex life cycles of asexual polyp stages and sexual medusae.
Some, omit either the polyp or the medusa stage. Cnidarians were grouped with ctenophores in the phylum Coelenterata, but increasing awareness of their differences caused them to be placed in separate phyla. Cnidarians are classified into four main groups: the wholly sessile Anthozoa. Staurozoa have been recognised as a class in their own right rather than a sub-group of Scyphozoa, the parasitic Myxozoa and Polypodiozoa were only recognized as cnidarians in 2007. Most cnidarians prey on organisms ranging in size from plankton to animals several times larger than themselves, but many obtain much of their nutrition from dinoflagellates, a few are parasites. Many are preyed on by other animals including starfish, sea slugs, fish and other cnidarians. Many scleractinian corals—which form the structural foundation for coral reefs—possess polyps that are filled with symbiotic photo-synthetic zooxanthellae. While reef-forming corals are entirely restricted to warm and shallow marine waters, other cnidarians can be found at great depths, in polar regions, in freshwater.
Recent phylogenetic analyses support monophyly of cnidarians, as well as the position of cnidarians as the sister group of bilaterians. Fossil cnidarians have been found in rocks formed about 580 million years ago, other fossils show that corals may have been present shortly before 490 million years ago and diversified a few million years later. However, molecular clock analysis of mitochondrial genes suggests a much older age for the crown group of cnidarians, estimated around 741 million years ago 200 million years before the Cambrian period as well as any fossils. Cnidarians form a phylum of animal that are more complex than sponges, about as complex as ctenophores, less complex than bilaterians, which include all other animals. Both cnidarians and ctenophores are more complex than sponges as they have: cells bound by inter-cell connections and carpet-like basement membranes. Cnidarians are distinguished from all other animals by having cnidocytes that fire harpoon like structures and are used to capture prey.
In some species, cnidocytes can be used as anchors. Like sponges and ctenophores, cnidarians have two main layers of cells that sandwich a middle layer of jelly-like material, called the mesoglea in cnidarians. Hence and ctenophores have traditionally been labelled diploblastic, along with sponges. However, both cnidarians and ctenophores have a type of muscle that, in more complex animals, arises from the middle cell layer; as a result, some recent text books classify ctenophores as triploblastic, it has been suggested that cnidarians evolved from triploblastic ancestors. Most adult cnidarians appear as either free-swimming medusae or sessile polyps, many hydrozoans species are known to alternate between the two forms. Both are radially symmetrical, like a tube respectively. Since these animals have no heads, their ends are described as "oral" and "aboral". Most have fringes of tentacles equipped with cnidocytes around their edges, medusae have an inner ring of tentacles around the mouth; some hydroids may consist of colonies of zooids that serve different purposes, such as defense and catching prey.
The mesoglea of polyps is thin and soft, but that of medusae is thick and springy, so that it returns to its original shape after muscles around the edge have contracted to squeeze water out, enabling medusae to swim by a sort of jet propulsion. In medusae the only supporting structure is the mesoglea. Hydra and most sea anemones close their mouths when they are not feeding, the water in the digestive cavity acts as a hydrostatic skeleton, rather like a water-filled balloon. Other polyps such as Tubularia use columns of water-filled cells for support. Sea pens stiffen the mesoglea with calcium carbonate spicules and tough fibrous proteins, rather like sponges. In some colonial polyps, a chitinous periderm gives support and some protection to the connecting sections and to the lower parts of individual polyps. Stony corals secrete massive calcium carbonate exoske
Binomial nomenclature called binominal nomenclature or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomen, binominal name or a scientific name; the first part of the name – the generic name – identifies the genus to which the species belongs, while the second part – the specific name or specific epithet – identifies the species within the genus. For example, humans belong within this genus to the species Homo sapiens. Tyrannosaurus rex is the most known binomial; the formal introduction of this system of naming species is credited to Carl Linnaeus beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus; the application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature for animals and the International Code of Nomenclature for algae and plants.
Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules. In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not when derived from a proper noun such as the name of a person or place. Both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a binomial name is given, at least when it is first mentioned, the date of publication may be specified. In zoology "Patella vulgata Linnaeus, 1758"; the name "Linnaeus" tells the reader who it was that first published a description and name for this species of limpet. "Passer domesticus". The original name given by Linnaeus was Fringilla domestica; the ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs include such information.
In botany "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus". "Hyacinthoides italica Rothm. – Linnaeus first named this bluebell species Scilla italica. The name is composed of two word-forming elements: "bi", a Latin prefix for two, "-nomial", relating to a term or terms; the word "binomium" was used in Medieval Latin to mean a two-term expression in mathematics. Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name, from one to several words long. Together they formed a system of polynomial nomenclature; these names had two separate functions. First, to designate or label the species, second, to be a diagnosis or description. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; such "polynomial names" may sometimes look like binomials, but are different. For example, Gerard's herbal describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort.
The other... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels; the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more known by his Latinized name Carl Linnaeus, it was in his 1753 Species Plantarum that he first began using a one-word "trivial name" together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as specific name; the Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word. Linnaeus's trivial names introduced an important new idea, namely that the function of a name could be to give a species a unique label; this meant. Thus Gerard's Phalangium ephemerum virginianum became Tradescantia virgi
The Jurassic period was a geologic period and system that spanned 56 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 known as the Age of Reptiles; the start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, the Tithonian event at the end; the Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations; the Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, Gondwana to the south; this created more coastlines and shifted the continental climate from dry to humid, many of the arid deserts of the Triassic were replaced by lush rainforests.
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 appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life; the oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates. The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range following the course of the France–Switzerland border. During a tour of the region in 1795, Alexander von Humboldt recognized the limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, he named it "Jura-Kalkstein" in 1799.
The name "Jura" is derived from the Celtic root *jor via Gaulish *iuris "wooded mountain", borrowed into Latin as a place name, evolved into Juria and Jura. The Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations known as Lias and Malm in Europe; the separation of the term Jurassic into three sections originated with Leopold von Buch. The faunal stages from youngest to oldest are: During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Jurassic North Atlantic Ocean was narrow, while the South Atlantic did not open until the following Cretaceous period, when Gondwana itself rifted apart. The Tethys Sea closed, the Neotethys basin appeared. Climates were warm, with no evidence of a glacier having appeared; as in the Triassic, there was no land over either pole, no extensive ice caps existed.
The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of that future landmass was submerged under shallow tropical seas. In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation; 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 common, along with calcitic ooids, calcitic cements, invertebrate faunas with dominantly calcitic skeletons; 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, South America, Japan and the United Kingdom.
In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north. As the Jurassic proceeded and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are neither well studied in Africa. Late Jurassic strata are poorly represented apart from the spectacular Tendaguru fauna in Tanzania; the Late Jurassic life of Tendaguru is similar to that found in western North America's Morrison Formation. During the Jurassic period, the primary vertebrates living in the sea were marine reptiles; the latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs and marine crocodiles of the families Teleosauridae and Metriorhynchidae. Numerous turtles could be found in rivers. In the invertebrate world, several new groups appeared, including rudists (a reef-formi