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For the language family, see Permic languages. For the high school, see Permian High School.
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The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom of Permia, and not after the small town of Perm, as usually assumed; see "Origin of the Permian" is a geologic period that extends from 299.0 ± 0.8 Ma to 251.0 ± 0.4 Ma (million years before the present) (ICS, 2004)Gradstein, F.M.; Ogg, J.G.; Smith, A.G. (2004). A Geologic Time Scale 2004. Cambridge university press. . It is the last period of the Paleozoic Era.
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The three primary subdivisions of the Permian Period are given below from youngest to oldest, and include faunal stages also from youngest to oldest. Additional age/stage equivalents or subdivisions are given in parentheses. Epoch and age refer to time, and equivalents series and stage refer to the rocks.
Lopingian Epoch
Guadalupian Epoch
Cisuralian Epoch
Sea levels in the Permian remained generally low, and near-shore environments were limited by the collection of almost all major landmasses into a single continent -- Pangaea. One continent, even a very large one, has a smaller shoreline than six to eight smaller ones with the same total area. This could have in part caused the widespread 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 Earth\'s major land masses except portions of East Asia were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("Panthalassa", the "universal sea"), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmasses create climates with extreme variations of heat and cold ("continental climate") and monsoon conditions with highly seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores. The first modern trees (conifers, ginkgos and cycads) appeared in the Permian.
Three general areas are especially noted for their Permian deposits- the Ural Mountains (where Perm itself is located), China, and the southwest of North America, where the Permian Basin in the U.S. state of Texas is so named because it has one of the thickest deposits of Permian rocks in the world.
As the Permian opened, the Earth was still in the grip of an ice age, so the polar regions were covered with deep layers of ice. Glaciers continued to cover much of Gondwanaland, as they had during the late Carboniferous.
Towards the middle of the period the climate became warmer and milder, the glaciers receded, and the continental interiors became drier. Much of the interior of Pangaea was probably arid, with great seasonal fluctuations (wet and dry seasons), because of the lack of the moderating effect of nearby bodies of water. This drying tendency continued through to the late Permian, along with alternating warming and cooling periods.
Edaphosaurus pogonias - Early Permian
Ocher fauna - Early Middle Permian, Ural Region
Titanophoneus and Ulemosaurus - Middle Permian, Ural Region
Anteosaurus in landscape - Middle Permian, South Africa
Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. Fossilized shells of two kinds of invertebrates are widely used to identify Permian strata and correlate them between sites: fusulinids, a kind of shelled amoeba-like protist that is one of the foraminiferans, and ammonoids, shelled cephalopods that are distant relatives of the modern nautilus.
Terrestrial life in the Permian included diverse plants, fungi, arthropods, and various types of tetrapods.
The Permian began with the Carboniferous flora still flourishing. About the middle of the Permian there was a major transition in vegetation. The swamp-loving lycopod trees of the Carboniferous, such as Lepidodendron and Sigillaria, were replaced by the more advanced conifers, which were better adapted to the changing climatic conditions. Lycopods and swamp forests still dominated the South China continent because it was an isolated continent and it sat near or at the equator. Oxygen levels were probably high there. The Permian saw the radiation of many important conifer groups, including the ancestors of many present-day families. The ginkgos and cycads also appeared during this period. Rich forests were present in many areas, with a diverse mix of plant groups.
Cockroaches (Blattodea) were the dominant herbivore and omnivore in early Permian. By the Pennsylvanian and well into the Permian, by far the most successful were ancestors of the cockroach. Six fast legs, two well developed folding wings, fairly good eyes, long, well developed antennae (olfactory), an omnivorous digestive system, a receptacle for storing sperm, a chitin skeleton that could support and protect, as well as form a gizzard and efficient mouth parts, gave it formidable advantages over other herbivorous animals. About 90% of insects were roaches.Zimmerman EC (1948) Insects of Hawaii, Vol. II. Univ. Hawaii Press The dragonflies Odonata were the dominant aerial predator and probably dominated terrestrial insect predation as well. True Odonata appeared in the PermianGrzimek HC Bernhard (1975) Grzimek\'s Animal Life Encyclopedia Vol 22 Insects. Van Nostrand Reinhold Co. NY. Riek EF Kukalova-Peck J (1984) A new interpretation of dragonfly wing venation based on early Upper Carboniferous fossils from Argentina (Insecta: Odonatoida and basic character states in Pterygote wings.) Can. J. Zool. 62; 1150-1160. and all are amphibious. Their prototypes are the oldest winged fossils, Wakeling JM Ellington CP (1997) Dragonfly flight III lift and power requirements. Journal of Experimental Biology 200; 583-600, on p589 go back to the Devonian, and are different from other wings in every way. Matsuda R (1970) Morphology and evolution of the insect thorax. Mem. Ent. Soc. Can. 76; 1-431. Their prototypes may have had the beginnings of many modern attributes even by late Carboniferous and it is possible that they even captured small vertebrates, for some species had a wing span of 71 cm. Riek EF Kukalova-Peck J (1984) A new interpretation of dragonfly wing venation based on early Upper Carboniferous fossils from Argentina (Insecta: Odonatoida and basic character states in Pterygote wings.) Can. J. Zool. 62; 1150-1160 A number of important new insect groups appeared at this time, including the Coleoptera (beetles) and Diptera (flies).
Permian tetrapods consisted of temnospondyli, lepospondyli and batrachosaur amphibians and sauropsids and synapsid (pelycosaurs and therapsids) amniotes. This period saw the development of a fully terrestrial fauna and the appearance of the first large herbivores and carnivores.
Early Permian terrestrial faunas were dominated by pelycosaurs and amphibians, the middle Permian by primitive therapsids such as the dinocephalia, and the late Permian by more advanced therapsids such as gorgonopsians and dicynodonts. Towards the very end of the Permian the first archosaurs appeared (proterosuchid thecodonts); during the following, Triassic, period these latter would evolve into more advanced types, eventually into dinosaurs. Also appearing at the end of the Permian were the first cynodonts, which would go on to evolve into mammals during the Triassic. Another group of therapsids, the therocephalians (such as Trochosaurus), arose in the Middle Permian. There were no aerial vertebrates.
The Permian ended with the most extensive extinction event recorded in paleontology: the Permian-Triassic extinction event. 90% to 95% of marine species became extinct, as well as 70% of all land organisms. On an individual level, perhaps as many as 99.5% of separate organisms died as a result of the event.http://www.historyfiles.co.uk/FeaturesAfrica/Permian_Extinction1.htm
There is also significant evidence that massive flood basalt eruptions from magma output lasting thousands of years in what is now the Siberian Traps contributed to environmental stress leading to mass extinction. The reduced coastal habitat and highly increased aridity probably also contributed. Based on the amount of lava estimated to have been produced during this period, the worst case scenario is an expulsion of enough carbon dioxide from the eruptions to raise world temperatures five degrees Celsius, not enough to kill off 95% of life.
Another hypothesis involves ocean venting of hydrogen sulfide gas. Portions of deep ocean will periodically lose all of its dissolved oxygen allowing bacteria that live without oxygen to flourish and produce hydrogen sulfide gas. If enough hydrogen sulfide accumulates in an anoxic zone, the gas can rise into the atmosphere.
Oxidizing gases in the atmosphere would destroy the toxic gas, but the hydrogen sulfide would soon consume all of the atmospheric gas available to change it. Hydrogen sulfide levels would increase dramatically over a few hundred years.
Modeling of such an event indicates that the gas would destroy ozone in the upper atmosphere allowing ultraviolet radiation to kill off species that had survived the toxic gas (Kump, et al, 2005). Of course, there are species that can metabolize hydrogen sulfide.
Another hypothesis builds on the flood basalt eruption theory. Five degrees Celsius would not be enough increase in world temperatures to explain the death of 95% of life. But such warming could slowly raise ocean temperatures until frozen methane reservoirs below the ocean floor near coastlines (a current target for a new energy source) melted, expelling enough methane, among the most potent greenhouse gases, into the atmosphere to raise world temperatures an additional five degrees Celsius. The frozen methane hypothesis helps explain the increase in carbon-12 levels midway into the Permian-Triassic boundary layer. It also helps explain why the first phase of the layer\'s extinctions was land-based, the second was marine-based (and starting right after the increase in C-12 levels), and the third land-based again.
An even more speculative hypothesis is that intense radiation from a nearby supernova was responsible for the extinctions.
Trilobites, which had thrived since Cambrian times, finally became extinct before the end of the Permian.
In 2006, a group of American scientists from Ohio State University reported evidence for a possible huge meteorite crater (Wilkes Land crater) with a diameter of around 500 kilometers in Antarctica. The crater is located at a depth of 1.6 kilometers beneath the ice of Wilkes Land in eastern Antarctica. The scientists speculate that this impact may have caused the Permian-Triassic extinction event, although its age is bracketed only between 100 million and 500 million years ago. They also speculate that it may have contributed in some way to the separation of Australia from the Antarctic landmass, which were both part of a supercontinent called Gondwana. Levels of iridium and quartz fracturing in the Permian-Triassic layer do not approach those of the Cretaceous-Tertiary boundary layer. Given that a far greater proportion of species and individual organisms became extinct during the former, doubt is cast on the significance of a meteor impact in creating the latter. Further doubt has been cast on this theory based on fossils in Greenland showing the extinction to have been gradual, lasting about eighty thousand years, with three distinct phases.
Many scientists believe that the Permian-Triassic extinction event was caused by a combination of some or all of the hypotheses above and other factors; the formation of Pangaea decreased the number of coastal habitats and may have contributed to the extinction of many clades.
Wikimedia Commons has media related to:
| Permian period | ||
|---|---|---|
| Cisuralian | Guadalupian | Lopingian |
| Asselian | Sakmarian Artinskian | Kungurian | Roadian | Wordian Capitanian | Wuchiapingian Changhsingian |
| Paleozoic era | |||||
|---|---|---|---|---|---|
| Cambrian | Ordovician | Silurian | Devonian | Carboniferous | Permian |
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