Phanerozoic
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The Phanerozoic The time span of the Phanerozoic starts with the myriapods and tetrapods; and the development of modern fauna dominated by vascular plants. During this time span, tectonic forces which move the continents had collected them into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.
EtymologyThe term "Phanerozoic" was coined in 1930 by the American geologist George Halcott Chadwick (1876–1953), Proterozoic–Phanerozoic boundary
The Avalon Explosion, have been identified since the systematic study of those forms started in the 1950s.[8][9] The transition from the largely sessile Precambrian biota to the active mobile Cambrian biota occurred early in the Phanerozoic.
Eras of the Phanerozoic The Phanerozoic is divided into three extinction of all non-avian dinosaurs, pterosaurs and marine reptiles, and features the great diversification in birds and mammals. Humans appeared and evolved during the most recent part of the Cenozoic.
Paleozoic EraThe Paleozoic is a time in Earth's history when active complex life forms evolved, took their first foothold on dry land, and when the forerunners of all multicellular life on Earth began to diversify. There are six periods in the Paleozoic era: Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.[10] Cambrian PeriodMain article: radiodontids) and to a lesser extent shelled cephalopods (such as orthocones). Almost all phyla of marine animals evolved in this period. During this time, the super-continent Pannotia began to break up, most of which later recombined into the super-continent Gondwana.[11]
Ordovician PeriodThe Ordovician spans from 485 million to 444 million years ago. The Ordovician was a time in Earth's history in which many groups still prevalent today evolved or diversified, such as primitive land plants .
By the end of the Ordovician, Gondwana had moved from the equator to the Ordovician–Silurian extinction, during which 60% of marine invertebrates and 25% of families became extinct. Though one of the deadliest mass extinctions in earth's history, the O–S extinction did not cause profound ecological changes between the periods.[13]
Silurian Period The Silurian spans from 444 million to 419 million years ago, which saw a warming from an icehouse Earth. This period saw the myriapods. The evolution of vascular plants (mainly spore-producing ferns such as Cooksonia) allowed land plants to gain a foothold further inland as well. During this time, there were four continents: Gondwana (Africa, South America, Australia, Antarctica, India), Laurentia (North America with parts of Europe), Baltica (the rest of Europe), and Siberia (Northern Asia).[14]
Devonian Period The Devonian spans from 419 million to 359 million years ago. Also informally known as the "Age of the Fish", the Devonian features a huge diversification in fish such as the jawless lycophytes, horsetails and progymnosperm. This greening event also allowed the diversification of arthropods as they took advantage of the new habitat. Near the end of the Devonian, 70% of all species became extinct in a sequence of mass extinction events, collectively known as the Late Devonian extinction.[15]
Carboniferous Period The Carboniferous spans from 359 million to 299 million years ago. Permian Period The Permian spans from 299 million to 251 million years ago and was the last period of the Paleozoic era. At its beginning, all landmasses came together to form the supercontinent mass extinction, an event sometimes known as "the Great Dying", caused by large floods of lava (the Siberian Traps in Russia and the Emeishan Traps in China). This extinction was the largest in Earth's history and led to the loss of 95% of all species of life.[19][20]
Mesozoic EraThe Mesozoic ranges from 252 million to 66 million years ago. Also referred to as the Age of Reptiles, Age of Dinosaurs or Age of Conifers, Triassic PeriodThe Triassic ranges from 252 million to 201 million years ago. The Triassic is mostly a transitional recovery period between the desolate aftermath of the Permian Extinction and the lush Jurassic Period. It has three major epochs: Early Triassic, Middle Triassic, and Late Triassic.[22]
The Early Triassic lasted between 252 million to 247 million years ago,  The Middle Triassic spans from 247 million to 237 million years ago.[23] The Middle Triassic featured the beginnings of the break-up of Pangaea as rifting commenced in north Pangaea. The northern part of the Tethys Ocean, the Paleotethys Ocean, had become a passive basin, but a spreading center was active in the southern part of the Tethys Ocean, the Neotethys Ocean.[27] Phytoplankton, coral, crustaceans and many other marine invertebrates recovered from the Permian extinction by the end of the Middle Triassic.[28] Meanwhile, on land, reptiles continued to diversify, conifer forests flourished,[29] as well as the first flies.[30][31][32] The Late Triassic spans from 237 million to 201 million years ago. Jurassic Period The Jurassic ranges from 201 million to 145 million years ago, and features three major epochs: Early Jurassic, Middle Jurassic and Late Jurassic.[39] The Early Jurassic epoch spans from 201 million to 174 million years ago.  The Middle and Late Jurassic Epochs span from 174 million to 145 million years ago. Cretaceous PeriodThe Cretaceous is the Phanerozoic's longest period and the last period of the Mesozoic. It spans from 145 million to 66 million years ago, and is divided into two epochs: Early Cretaceous, and Late Cretaceous.[53]  The Early Cretaceous Epoch spans from 145 million to 100 million years ago. The Late Cretaceous Epoch spans from 100 million to 66 million years ago. Cenozoic EraThe Cenozoic featured the rise of mammals and birds as the dominant class of animals, as the end of the Age of Dinosaurs left significant open niches. There are three divisions of the Cenozoic: Paleogene, Neogene and Quaternary. Paleogene PeriodThe Paleogene spans from the extinction of the non-avian dinosaurs, some 66 million years ago, to the dawn of the Neogene 23 million years ago. It features three . The Paleocene Epoch began with the K–Pg extinction event, and the early part of the Paleocene saw the recovery of the Earth from that event. The continents began to take their modern shapes, but most continents (and India) remained separated from each other: Africa and , the largest known snake, lived in South America during the Paleocene.The Eocene Epoch ranged from 56 million to 34 million years ago. In the early Eocene, most land mammals were small and living in cramped jungles, much like the Paleocene. Among them were early primates, whales and horses along with many other early forms of mammals. The climate was warm and humid, with little temperature gradient from pole to pole. In the Middle Eocene Epoch, the Antarctic Circumpolar Current formed when South America and Australia both separated from Antarctica to open up the Drake Passage and Tasmanian Passage, disrupting ocean currents worldwide, resulting in global cooling and causing the jungles to shrink. More modern forms of mammals continued to diversify with the cooling climate even as more archaic forms died out. By the end of the Eocene, whales such as Basilosaurus had become fully aquatic. The late Eocene Epoch saw the rebirth of seasons, which caused the expansion of savanna-like areas with the earliest substantial grasslands.[57][58] At the transition between the Eocene and Oligocene epochs there was a significant extinction event, the cause of which is debated. The Oligocene Epoch spans from 34 million to 23 million years ago. The Oligocene was an important transitional period between the tropical world of the Eocene and more modern ecosystems. This period featured a global expansion of grass which led to many new species taking advantage, including the first perissodactyls .
Neogene PeriodThe Neogene spans from 23.03 million to 2.58 million years ago. It features two epochs: the Miocene and the Pliocene.[59] The Miocene spans from 23.03 million to 5.333 million years ago and is a period in which Mediterranean and Caspian seas. This only increased aridity. Many new plants evolved, and 95% of modern seed plants evolved in the mid-Miocene.[60]
The Pliocene lasted from 5.333 million to 2.58 million years ago. The Pliocene featured dramatic climatic changes, which ultimately led to modern species and plants. The Mediterranean Sea dried up for hundreds of thousand years in the Sahara Desert. The Earth's continents and seas moved into their present shapes. The world map has not changed much since, save for changes brought about by the Quaternary glaciation such as Lake Agassiz (precursor of the Great Lakes).[61][62]
Quaternary PeriodThe Quaternary spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic Eon. It features modern animals, and dramatic changes in the climate. It is divided into two epochs: the Pleistocene and the Holocene .
The Pleistocene lasted from 2.58 million to 11,700 years ago. This epoch was marked by a series of Homo neanderthalensis and Homo floresiensis. All the continents were affected, but Africa was impacted to a lesser extent and retained many large animals such as elephants, rhinoceros and hippopotamus. The extent to which Homo sapiens were involved in this megafaunal extinction is debated.[63]
The Holocene began 11,700 years ago at the end of Biodiversity  It has been demonstrated that changes in biodiversity through the Phanerozoic correlate much better with the hyperbolic model (widely used in demography and macrosociology) than with exponential and logistic models (traditionally used in population biology and extensively applied to fossil biodiversity as well). The latter models imply that changes in diversity are guided by a first-order positive feedback (more ancestors, more descendants) or a negative feedback that arises from resource limitation, or both. The hyperbolic model implies a second-order positive feedback. The hyperbolic pattern of the human population growth arises from quadratic positive feedback, caused by the interaction of the population size and the rate of technological growth.[67] The character of biodiversity growth in the Phanerozoic Eon can be similarly accounted for by a feedback between the diversity and community structure complexity. It has been suggested that the similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the superposition on the hyperbolic trend of cyclical and random dynamics.[67] ClimateAcross the Phanerozoic, the dominant driver of long-term climatic change was the concentration of carbon dioxide in the atmosphere,[68] though some studies have suggested a decoupling of carbon dioxide and palaeotemperature, particularly during cold intervals of the Phanerozoic.[69] Phanerozoic carbon dioxide concentrations have been governed partially by a 26 million year oceanic crustal cycle.[70] Since the Devonian, large swings in carbon dioxide of 2,000 ppm or more were uncommon over short timescales.[71] Variations in global temperature were limited by negative feedbacks in the phosphorus cycle, wherein increased phosphorus input into the ocean would increase surficial biological productivity that would in turn enhance iron redox cycling and thus remove phosphorus from seawater; this maintained a relatively stable rate of removal of carbon from the atmosphere and ocean via organic carbon burial.[72] The climate also controlled the availability of phosphate through its regulation of rates of continental and seafloor weathering.[73] Major global temperature variations of >7 °C during the Phanerozoic were strongly associated with mass extinctions.[74] See also 
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General references
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