The Permian witnessed the diversification of the two groups ofamniotes, thesynapsids and thesauropsids (reptiles). The world at the time was dominated by the supercontinentPangaea, which had formed due to the collision ofEuramerica andGondwana during the Carboniferous. Pangaea was surrounded by the superoceanPanthalassa. TheCarboniferous rainforest collapse left behind vast regions ofdesert within the continental interior.[10] Amniotes, which could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors.
Various authors have proposed at least three,[11] and possibly four major extinction events in the Permian, though the validity of some of these extinctions has been disputed.[12] The end of the Early Permian (Cisuralian) has a gap in the fossil record that may have constituted amajor extinction, as most lineages of primitive "pelycosaur" synapsids becoming extinct, being replaced by more advancedtherapsids. The end of theCapitanian Stage of the Permian was marked by the majorCapitanian mass extinction event,[13] associated with the eruption of theEmeishan Traps. The Permian (along with the Paleozoic) ended with thePermian–Triassic extinction event (colloquially known as the Great Dying), the largest mass extinction in Earth's history (which is the last of the three or four crises that occurred in the Permian), in which nearly 81% of marine species and 70% of terrestrial species died out, associated with the eruption of theSiberian Traps. It took well into theTriassic for life to recover from this catastrophe;[14][15][16] on land, ecosystems took 30 million years to recover.[17]
Prior to the introduction of the termPermian, rocks of equivalent age in Germany had been named theRotliegend andZechstein, and in Great Britain as theNew Red Sandstone.[18]
The termPermian was introduced intogeology in 1841 bySir Roderick Impey Murchison, president of theGeological Society of London, after extensive Russian explorations undertaken withÉdouard de Verneuil in the vicinity of theUral Mountains in the years 1840 and 1841. Murchison identified "vast series of beds ofmarl,schist,limestone,sandstone and conglomerate" that succeededCarboniferous strata in the region.[19][20] Murchison, in collaboration with Russian geologists,[21] named the period after the surrounding Russian region of Perm, which takes its name from the medieval kingdom ofPermia that occupied the same area hundreds of years prior, and which is now located in thePerm Krai administrative region.[22] Between 1853 and 1867,Jules Marcou recognised Permian strata in a large area of North America from theMississippi River to theColorado River and proposed the nameDyassic, fromDyas andTrias, though Murchison rejected this in 1871.[23] The Permian system was controversial for over a century after its original naming, with theUnited States Geological Survey until 1941 considering the Permian a subsystem of the Carboniferous equivalent to theMississippian andPennsylvanian.[18]
For most of the 20th century, the Permian was divided into the Early and Late Permian, with the Kungurian being the last stage of the Early Permian.[25] Glenister and colleagues in 1992 proposed a tripartite scheme, advocating that the Roadian-Capitanian was distinct from the rest of the Late Permian, and should be regarded as a separate epoch.[26] The tripartite split was adopted after a formal proposal by Glenister et al. (1999).[27]
Historically, most marine biostratigraphy of the Permian was based onammonoids; however, ammonoid localities are rare in Permian stratigraphic sections, and species characterise relatively long periods of time. All GSSPs for the Permian are based around thefirst appearance datum of specific species ofconodont, an enigmatic group of jawlesschordates with hard tooth-like oral elements. Conodonts are used asindex fossils for most of the Palaeozoic and the Triassic.[28]
The Cisuralian Series is named after the strata exposed on the western slopes of the Ural Mountains in Russia and Kazakhstan. The name was proposed by J. B. Waterhouse in 1982 to comprise the Asselian, Sakmarian, and Artinskian stages. The Kungurian was later added to conform to the Russian "Lower Permian".Albert Auguste Cochon de Lapparent in 1900 had proposed the "Uralian Series", but the subsequent inconsistent usage of this term meant that it was later abandoned.[29]
The Asselian was named by the Russian stratigrapher V.E. Ruzhenchev in 1954, after theAssel River in the southern Ural Mountains. The GSSP for the base of the Asselian is located in the Aidaralash River valley nearAqtöbe, Kazakhstan, which was ratified in 1996. The beginning of the stage is defined by the first appearance ofStreptognathodus postfusus.[30]
The Sakmarian is named in reference to theSakmara River in the southern Urals, and was coined byAlexander Karpinsky in 1874. The GSSP for the base of the Sakmarian is located at the Usolka section in the southern Urals, which was ratified in 2018. The GSSP is defined by the first appearance ofSweetognathus binodosus.[31]
The Artinskian was named after the city ofArti inSverdlovsk Oblast, Russia. It was named by Karpinsky in 1874. The Artinskian currently lacks a defined GSSP.[24] The proposed definition for the base of the Artinskian is the first appearance ofSweetognathus aff. S. whitei.[28]
The Kungurian takes its name afterKungur, a city in Perm Krai. The stage was introduced by Alexandr Antonovich Stukenberg in 1890. The Kungurian currently lacks a defined GSSP.[24] Recent proposals have suggested the appearance ofNeostreptognathodus pnevi as the lower boundary.[28]
The Guadalupian Series is named after theGuadalupe Mountains in Texas and New Mexico, where extensive marine sequences of this age are exposed. It was named byGeorge Herbert Girty in 1902.[32]
The Roadian was named in 1968 in reference to the Road Canyon Member of theWord Formation in Texas.[32] The GSSP for the base of the Roadian is located 42.7m above the base of theCutoff Formation in Stratotype Canyon, Guadalupe Mountains, Texas, and was ratified in 2001. The beginning of the stage is defined by the first appearance ofJinogondolella nankingensis.[28]
The Wordian was named in reference to the Word Formation byJohan August Udden in 1916, Glenister and Furnish in 1961 was the first publication to use it as a chronostratigraphic term as a substage of the Guadalupian Stage.[32] The GSSP for the base of the Wordian is located in Guadalupe Pass, Texas, within the sediments of the Getaway Limestone Member of theCherry Canyon Formation, which was ratified in 2001. The base of the Wordian is defined by the first appearance of the conodontJinogondolella aserrata.[28]
The Capitanian is named after the Capitan Reef in the Guadalupe Mountains of Texas, named byGeorge Burr Richardson in 1904, and first used in a chronostratigraphic sense by Glenister and Furnish in 1961 as a substage of the Guadalupian Stage.[32] The Capitanian was ratified as an international stage by the ICS in 2001. The GSSP for the base of the Capitanian is located at Nipple Hill in the southeast Guadalupe Mountains of Texas, and was ratified in 2001, the beginning of the stage is defined by the first appearance ofJinogondolella postserrata.[28]
The Lopingian was first introduced byAmadeus William Grabau in 1923 as the "Loping Series" afterLeping,Jiangxi, China. Originally used as a lithostraphic unit, T.K. Huang in 1932 raised the Lopingian to a series, including all Permian deposits in South China that overlie the Maokou Limestone. In 1995, a vote by the Subcommission on Permian Stratigraphy of the ICS adopted the Lopingian as an international standard chronostratigraphic unit.[33]
The Wuchiapinginan and Changhsingian were first introduced in 1962, by J. Z. Sheng as the "Wuchiaping Formation" and "Changhsing Formation" within the Lopingian series. The GSSP for the base of the Wuchiapingian is located at Penglaitan,Guangxi, China and was ratified in 2004. The boundary is defined by the first appearance ofClarkina postbitteri postbitteri[33] The Changhsingian was originally derived from the Changxing Limestone, a geological unit first named by the Grabau in 1923, ultimately deriving fromChangxing County,Zhejiang .The GSSP for the base of the Changhsingian is located 88 cm above the base of the Changxing Limestone in the Meishan D section, Zhejiang, China and was ratified in 2005, the boundary is defined by the first appearance ofClarkina wangi.[34]
The GSSP for the base of the Triassic is located at the base of Bed 27c at the Meishan D section, and was ratified in 2001. The GSSP is defined by the first appearance of the conodontHindeodus parvus.[35]
The Russian Tatarian Stage includes the Lopingian, Capitanian and part of the Wordian, while the underlying Kazanian includes the rest of the Wordian as well as the Roadian.[25]
In North America, the Permian is divided into the Wolfcampian (which includes the Nealian and the Lenoxian stages); the Leonardian (Hessian and Cathedralian stages); the Guadalupian; and the Ochoan, corresponding to the Lopingian.[36][37]
TheNew Zealand geologic time scale divides the Permian into three epochs, Pre-Telfordian (undivided), D'Urville (divided into the Makarewan, Waiitian, and Puruhauan stages), and Aparima (Flettian, Barrettian, Mangapirian, and Telfordian stages). The Pre-Telfordian epoch corresponds approximately to the Asselian, Sakmarian, and Artinskian stages; the D'Urville epoch is roughly contemporary with the Kungurian stage and Guadalupian epoch; and the Aparima epoch is closely contemporary with the Lopingian epoch.[38]
During the Permian, all theEarth's major landmasses were collected into a single supercontinent known asPangaea, with themicrocontinental terranes ofCathaysia to the east. Pangaea straddled theequator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("Panthalassa", the "universal sea"), and thePaleo-Tethys Ocean, a large ocean that existed between Asia and Gondwana. TheCimmeria continentrifted away fromGondwana and drifted north toLaurasia, causing the Paleo-Tethys Ocean to shrink. A new ocean was growing on its southern end, theNeotethys Ocean, an ocean that would dominate much of theMesozoic Era.[39] A magmatic arc, containing Hainan on its southwesternmost end, began to form as Panthalassa subducted under the southeastern South China.[40] TheCentral Pangean Mountains, which began forming due to the collision of Laurasia and Gondwana during the Carboniferous, reached their maximum height during the early Permian around 295 Ma, comparable to the presentHimalayas, but became heavily eroded as the Permian progressed.[41] TheKazakhstania block collided with Baltica during the Cisuralian, while theNorth China Craton, theSouth China Block andIndochina fused to each other and Pangea by the end of the Permian.[42] TheZechstein Sea, a hypersalineepicontinental sea, existed in what is now northwestern Europe.[43]
Large continental landmass interiors experience climates with extreme variations of heat and cold ("continental climate") andmonsoon conditions with highly seasonal rainfall patterns.Deserts seem to have been widespread on Pangaea.[44] Such dry conditions favoredgymnosperms, plants with seeds enclosed in a protective cover, over plants such asferns that dispersespores in a wetter environment. The first modern trees (conifers,ginkgos andcycads) appeared in the Permian.
Three general areas are especially noted for their extensive Permian deposits—theUral Mountains (where Perm itself is located), China, and the southwest of North America, including theTexas red beds. ThePermian Basin in theU.S. states ofTexas andNew Mexico is so named because it has one of the thickest deposits of Permian rocks in the world.[45]
Sea levels dropped slightly during the earliest Permian (Asselian). The sea level was stable at several tens of metres above present during the Early Permian, but there was a sharp drop beginning during the Roadian, culminating in the lowest sea level of the entire Palaeozoic at around present sea level during the Wuchiapingian, followed by a slight rise during the Changhsingian.[46]
The Permian was cool in comparison to most other geologic time periods, with modest pole to Equator temperature gradients. At the start of the Permian, the Earth was still in theLate Paleozoic icehouse (LPIA), which began in the latestDevonian and spanned the entire Carboniferous period, with its most intense phase occurring during the latter part of thePennsylvanian epoch.[47][48] A significant trend of increasing aridification can be observed over the course of the Cisuralian.[49] Early Permian aridification was most notable in Pangaean localities at near-equatorial latitudes.[50] Sea levels also rose notably in the Early Permian as the LPIA slowly waned.[51][52] At the Carboniferous-Permian boundary, a warming event occurred.[53] In addition to becoming warmer, the climate became notably more arid at the end of the Carboniferous and beginning of the Permian.[54][55] Nonetheless, temperatures continued to cool during most of the Asselian and Sakmarian, during which the LPIA peaked.[48][47] By 287 Ma, temperatures warmed and the South Pole ice cap retreated in what was known as the Artinskian Warming Event (AWE),[56] though glaciers remained present in the uplands of eastern Australia,[47][57] and perhaps also the mountainous regions of far northern Siberia.[58] Southern Africa also retained glaciers during the late Cisuralian in upland environments.[59] The AWE also witnessed aridification of a particularly great magnitude.[56]
In the late Kungurian, cooling resumed,[60] resulting in a cool glacial interval that lasted into the early Capitanian,[61] though average temperatures were still much higher than during the beginning of the Cisuralian.[57] Another cool period began around the middle Capitanian.[61] This cool period, lasting for 3–4 Myr, was known as the Kamura Event.[62] It was interrupted by the Emeishan Thermal Excursion in the late part of the Capitanian, around 260 million years ago, corresponding to the eruption of theEmeishan Traps.[63] This interval of rapidclimate change was responsible for the Capitanian mass extinction event.[13]
During the early Wuchiapingian, following the emplacement of the Emeishan Traps, global temperatures declined as carbon dioxide was weathered out of the atmosphere by the large igneous province's emplaced basalts.[64] The late Wuchiapingian saw the finale of the Late Palaeozoic Ice Age, when the last Australian glaciers melted.[47] The end of the Permian is marked by a temperature excursion, much larger than the Emeishan Thermal Excursion, at the Permian-Triassic boundary, corresponding to the eruption of theSiberian Traps, which released more than 5 teratonnes of CO2, more than doubling the atmospheric carbon dioxide concentration.[48] A -2%δ18O excursion signifies the extreme magnitude of this climatic shift.[65] This extremely rapid interval of greenhouse gas release caused the Permian-Triassic mass extinction,[66] as well as ushering in an extreme hothouse that persisted for several million years into the next geologic epoch, the Triassic.[67]
The Permian climate was also extremely seasonal and characterised bymegamonsoons,[68] which produced high aridity and extreme seasonality in Pangaea's interiors.[69] Precipitation along the western margins of the Palaeo-Tethys Ocean was very high.[70] Evidence for the megamonsoon includes the presence of megamonsoonal rainforests in the Qiangtang Basin of Tibet,[71] enormous seasonal variation in sedimentation, bioturbation, and ichnofossil deposition recorded in sedimentary facies in theSydney Basin,[72] and palaeoclimatic models of the Earth's climate based on the behaviour of modern weather patterns showing that such a megamonsoon would occur given the continental arrangement of the Permian.[73] The aforementioned increasing equatorial aridity was likely driven by the development and intensification of this Pangaean megamonsoon.[74]
Permian marine deposits are rich infossilmollusks,[75]brachiopods,[76][77][78] andechinoderms.[79][80] Brachiopods were highly diverse during the Permian. The extinct orderProductida was the predominant group of Permian brachiopods, accounting for up to about half of all Permian brachiopod genera.[81] Brachiopods also served as important ecosystem engineers in Permian reef complexes.[82] Amongstammonoids,Goniatitida were a major group during the Early-Mid Permian, but declined during the Late Permian. Members of the orderProlecanitida were less diverse. TheCeratitida originated from the familyDaraelitidae within Prolecanitida during the mid-Permian, and extensively diversified during the Late Permian.[83] Only three families oftrilobite are known from the Permian,Proetidae, Brachymetopidae andPhillipsiidae. Diversity, origination and extinction rates during the Early Permian were low. Trilobites underwent a diversification during the Kungurian-Wordian, the last in their evolutionary history, before declining during the Late Permian. By the Changhsingian, only a handful (4–6) genera remained.[84] Corals exhibited a decline in diversity over the course of the Middle and Late Permian.[85]
Terrestrial life in the Permian included diverse plants,fungi,arthropods, and various types oftetrapods. The period saw a massive desert covering the interior ofPangaea. The warm zone spread in the northern hemisphere, where extensive dry desert appeared.[86] The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals died out or became marginal elements.
The Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began. Theswamp-lovinglycopod trees of the Carboniferous, such asLepidodendron andSigillaria, were progressively replaced in the continental interior by the more advancedseed ferns and earlyconifers as a result of theCarboniferous rainforest collapse. At the close of the Permian, lycopod andequisete swamps reminiscent of Carboniferous flora survived only inCathaysia, a series of equatorial islands in thePaleo-Tethys Ocean that later would becomeSouth China.[87]
The Permian saw the radiation of many important conifer groups, including the ancestors of many present-day families. Rich forests were present in many areas, with a diverse mix of plant groups. The southern continent saw extensive seed fern forests of theGlossopteris flora. Oxygen levels were probably high there. Theginkgos andcycads also appeared during this period.
Insects, which had first appeared and become abundant during the preceding Carboniferous, experienced a dramatic increase in diversification during the Early Permian. Towards the end of the Permian, there was a substantial drop in both origination and extinction rates.[88] By the start of the Permian, there was already an active coevolutionary arms race between insects and plant reproductive structures, evidenced by both insect-caused damage in plants and defensive structures in plants aimed at minimising predation by insects.[89] The dominant insects during the Permian Period were early representatives ofPaleoptera,Polyneoptera, andParaneoptera.Palaeodictyopteroidea, which had represented the dominant group of insects during the Carboniferous, declined during the Permian. This is likely due tocompetition byHemiptera, due to their similar mouthparts and therefore ecology. Primitive relatives ofdamselflies anddragonflies (Meganisoptera), which include the largest flying insects of all time, also declined during the Permian.[90]Holometabola, the largest group of modern insects, also diversified during this time.[88] "Grylloblattidans", an extinct group of winged insects thought to be related to modernice crawlers, reached their apex of diversity during the Permian, representing up to a third of all insects at some localities.[91]Mecoptera (sometimes known as scorpionflies) first appeared during the Early Permian, going on to become diverse during the Late Permian. Some Permian mecopterans, likeMesopsychidae have long proboscis that suggest they may have pollinated gymnosperms.[92] The earliest knownbeetles appeared at the beginning of the Permian. Early beetles such as members ofPermocupedidae were likelyxylophagous, feeding on decaying wood. Several lineages such as Schizophoridae expanded into aquatic habitats by the Late Permian.[93] Members of the modern ordersArchostemata andAdephaga are known from the Late Permian.[94][95] Complex wood boring traces found in the Late Permian of China suggest that members ofPolyphaga, the most diverse group of modern beetles, were also present by the Late Permian.[96]
Restoration ofWeigeltisaurus jaekeli, aweigeltisaurid from the Late Permian of Europe. Weigeltisaurids represent the oldest known gliding vertebrates.
The terrestrial fossil record of the Permian is patchy and temporally discontinuous. Early Permian records are dominated by equatorial Europe and North America, while those of the Middle and Late Permian are dominated by temperateKaroo Supergroup sediments of South Africa and the Ural region of European Russia.[97] Early Permian terrestrial faunas of North America and Europe were dominated by primitivepelycosaursynapsids including the herbivorousedaphosaurids, and carnivoroussphenacodontids,diadectids andamphibians.[98][99] Early Permian reptiles, such asacleistorhinids, were mostly small insectivores.[100]
Synapsids (the group that would later include mammals) thrived and diversified greatly during the Cisuralian. Permian synapsids included some large members such asDimetrodon. The special adaptations of synapsids enabled them to flourish in the drier climate of the Permian and they grew to dominate the vertebrates.[98] A faunal turnover occurred around the transition between the Cisuralian and Guadalupian, with the decline of amphibians and the replacement of pelycosaurs (aparaphyletic group) with more advancedtherapsids,[11] although the decline of early synapsid clades was apparently a slow event that lasted about 20 Ma, from theSakmarian to the end of theKungurian.[101] Predator-prey interactions among terrestrial synapsids became more dynamic.[102] If terrestrial deposition ended around the end of the Cisuralian in North America and began in Russia during the early Guadalupian, a continuous record of the transition is not preserved. Uncertain dating has led to suggestions that there is a global hiatus in the terrestrial fossil record during the late Kungurian and earlyRoadian, referred to as "Olson's Gap" that obscures the nature of the transition. Other proposals have suggested that the North American and Russian records overlap,[103][104][105][106] with the latest terrestrial North American deposition occurring during the Roadian, suggesting that there was an extinction event, dubbed "Olson's Extinction".[107]
The Middle Permian faunas of South Africa and Russia are dominated by therapsids, most abundantly by the diverseDinocephalia. Dinocephalians become extinct at the end of the Middle Permian, during theCapitanian mass extinction event. Late Permian faunas are dominated by advanced therapsids such as the predatory sabertoothedgorgonopsians and herbivorous beakeddicynodonts, alongside large herbivorouspareiasaurparareptiles.[108] TheArchosauromorpha, the group of reptiles that would give rise to thepseudosuchians,dinosaurs, andpterosaurs in the following Triassic, first appeared and diversified during the Late Permian, including the first appearance of theArchosauriformes during the latest Permian.[109]Cynodonts, the group of therapsids ancestral to modernmammals, first appeared and gained a worldwide distribution during the Late Permian.[110] Another group of therapsids, thetherocephalians (such asLycosuchus), arose in the Middle Permian.[111][112] There were no flying vertebrates, though the extinct lizard-like reptile familyWeigeltisauridae from the Late Permian had extendable wings like moderngliding lizards, and are the oldest known gliding vertebrates.[113][114]
Temnospondyls reached a peak of diversity in the Cisuralian, with a substantial decline during the Guadalupian-Lopingian following Olson's extinction, with the family diversity dropping below Carboniferous levels.[117]
Embolomeres, a group of aquatic crocodile-like limbed vertebrates that arereptilliomorphs under some phylogenies. They previously had their last records in the Cisuralian, are now known to have persisted into the Lopingian in China.[118]
The diversity of fish during the Permian is relatively low compared to the following Triassic. The dominant group ofbony fishes during the Permian were the "Paleopterygii" aparaphyletic grouping ofActinopterygii that lie outside ofNeopterygii.[120] The earliest unequivocal members of Neopterygii appear during the Early Triassic, but a Permian origin is suspected.[121] The diversity ofcoelacanths is relatively low throughout the Permian in comparison to other marine fishes, though there is an increase in diversity during the terminal Permian (Changhsingian), corresponding with the highest diversity in their evolutionary history during the Early Triassic.[120] Diversity of freshwater fish faunas was generally low and dominated bylungfish and "Paleopterygians".[120] The last common ancestor of all living lungfish is thought to have existed during the Early Permian. Though the fossil record is fragmentary, lungfish appear to have undergone an evolutionary diversification and size increase in freshwater habitats during the Early Permian, but subsequently declined during the middle and late Permian.[122] Conodonts experienced their lowest diversity of their entire evolutionary history during the Permian.[123] Permian chondrichthyan faunas are poorly known.[124] Members of the chondrichthyan cladeHolocephali, which contains livingchimaeras, reached their apex of diversity during the Carboniferous-Permian, the most famous Permian representative being the "buzz-saw shark"Helicoprion, known for its unusual spiral shaped spiral tooth whorl in the lower jaw.[125]Hybodonts, a group of shark-like chondrichthyans, were widespread and abundant members of marine and freshwater faunas throughout the Permian.[124][126]Xenacanthiformes, another extinct group of shark-like chondrichthyans, were common in freshwater habitats, and represented theapex predators of freshwater ecosystems.[127]
Map of the world at the Carboniferous-Permian boundary, showing the four floristic provinces
Fourfloristic provinces in the Permian are recognised, theAngaran, Euramerican, Gondwanan, and Cathaysian realms.[128] TheCarboniferous Rainforest Collapse would result in the replacement oflycopsid-dominated forests withtree-fern dominated ones during the late Carboniferous in Euramerica, and result in the differentiation of the Cathaysian floras from those of Euramerica.[128] The Gondwanan floristic region was dominated byGlossopteridales, a group of woody gymnosperm plants, for most of the Permian, extending to high southern latitudes. The ecology of the most prominent glossopterid,Glossopteris, has been compared to that ofbald cypress, living inmires with waterlogged soils.[129] The tree-likecalamites, distant relatives of modernhorsetails, lived in coal swamps and grew inbamboo-like vertical thickets. A mostly complete specimen ofArthropitys from the Early PermianChemnitz petrified forest of Germany demonstrates that they had complex branching patterns similar to modernangiosperm trees.[130] By the Late Permian, high thin forests had become widespread across the globe, as evidenced by the global distribution of weigeltisaurids.[131]
The oldest likely record ofGinkgoales (the group containingGinkgo and its close relatives) isTrichopitys heteromorpha from the earliest Permian of France.[132] The oldest known fossils definitively assignable to moderncycads are known from the Late Permian.[133] In Cathaysia, where a wet tropical frost-free climate prevailed, theNoeggerathiales, an extinct group of tree fern-likeprogymnosperms were a common component of the flora[134][135] The earliest Permian (~ 298 million years ago) Cathyasian Wuda Tuff flora, representing a coal swamp community, has an upper canopy consisting oflycopsid treeSigillaria, with a lower canopy consisting ofMarattialean tree ferns, and Noeggerathiales.[128] Earlyconifers appeared in the Late Carboniferous, represented by primitivewalchian conifers, but were replaced with more derivedvoltzialeans during the Permian. Permian conifers were very similar morphologically to their modern counterparts, and were adapted to stressed dry or seasonally dry climatic conditions.[130] The increasing aridity, especially at low latitudes, facilitated the spread of conifers and their increasing prevalence throughout terrestrial ecosystems.[136]Bennettitales, which would go on to become in widespread the Mesozoic, first appeared during the Cisuralian in China.[137]Lyginopterids, which had declined in the late Pennsylvanian and subsequently have a patchy fossil record, survived into the Late Permian in Cathaysia and equatorial east Gondwana.[138]
The Permian–Triassic extinction event, labeled "End P" here, is the most significant extinction event in this plot for marinegenera which produce large numbers offossils
The Permian ended with the most extensiveextinction event recorded inpaleontology: thePermian–Triassic extinction event. 90 to 95% of marine species becameextinct, as well as 70% of all land organisms. It is also the only known mass extinction of insects.[16][139] Recovery from the Permian–Triassic extinction event was protracted; on land, ecosystems took 30 million years to recover.[17]Trilobites, which had thrived sinceCambrian times, finally became extinct before the end of the Permian.Nautiloids, a subclass of cephalopods, surprisingly survived this occurrence.
There is evidence thatmagma, in the form offlood basalt, poured onto the Earth's surface in what is now called theSiberian Traps, for thousands of years, contributing to the environmental stress that led to mass extinction. The reduced coastal habitat and highly increased aridity probably also contributed. Based on the amount oflava estimated to have been produced during this period, the worst-case scenario is the release of enough carbon dioxide from the eruptions to raise world temperatures five degrees Celsius.[140]
Another hypothesis involves ocean venting ofhydrogen sulfide gas. Portions of thedeep 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 ananoxic 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. Hydrogen sulfide levels might have increased dramatically over a few hundred years. Models of such an event indicate that the gas would destroyozone in the upper atmosphere allowingultraviolet radiation to kill off species that had survived the toxic gas.[141]There are species that can metabolize hydrogen sulfide.
Another hypothesis builds on the flood basalt eruption theory. An increase in temperature of five degrees Celsius would not be enough to explain the death of 95% of life. But such warming could slowly raise ocean temperatures untilfrozen methane reservoirs below the ocean floor near coastlines melted, expelling enough methane (among the most potentgreenhouse 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 found midway in 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.[142]
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^Ogg, J.G.; Ogg, G.; Gradstein, F.M. (2016).A Concise Geologic Time Scale: 2016. Amsterdam: Elsevier. p. 115.ISBN978-0-444-63771-0.
^Murchison, R.I.; de Verneuil, E.; von Keyserling, A. (1842).On the Geological Structure of the Central and Southern Regions of Russia in Europe, and of the Ural Mountains. London: Richard and John E. Taylor. p. 14.Permian System. (Zechstein of Germany — Magnesian limestone of England)—Some introductory remarks explain why the authors have ventured to use a new name in reference to a group of rocks which, as a whole, they consider to be on the parallel of the Zechstein of Germany and the magnesian limestone of England. They do so, not merely because a portion of deposits has long been known by the name "grits of Perm", but because, being enormously developed in thegovernments of Perm and Orenburg, they there assume a great variety of lithological features ...
^Murchison, R.I.; de Verneuil, E.; von Keyserling, A. (1845).Geology of Russia in Europe and the Ural Mountains. Vol. 1: Geology. London: John Murray. pp. 138–139....Convincing ourselves in the field, that these strata were so distinguished as to constitute a system, connected with the carboniferous rocks on the one hand, and independent of the Trias on the other, we ventured to designate them by a geographical term, derived from the ancient kingdom ofPermia, within and around whose precincts the necessary evidences had been obtained. ... For these reasons, then, we were led to abandon both the German and British nomenclature, and to prefer a geographical name, taken from the region in which the beds are loaded with fossils of an independent and intermediary character; and where the order of superposition is clear, the lower strata of the group being seen to rest upon the Carboniferous rocks.
^Verneuil, E. (1842). "Correspondance et communications".Bulletin de la Société Géologique de France.13:11–14. pp. 12–13:Le nom de Système Permien, nom dérivé de l'ancien royaume de Permie, aujourd'hui gouvernement de Perm, donc ce dépôt occupe une large part, semblerait assez lui convener ... [The name of the Permian System, a name derived from the ancient kingdom ofPermia, today theGovernment of Perm, of which this deposit occupies a large part, would seem to suit it well enough ...]
^Murchison, Roderick Impey (1841)"First sketch of some of the principal results of a second geological survey of Russia",Archived 2023-07-16 at theWayback MachinePhilosophical Magazine and Journal of Science, series 3,19 : 417–422. From p. 419: "The carboniferous system is surmounted, to the east of the Volga, by a vast series of marls, schists, limestones, sandstones and conglomerates, to which I propose to give the name of "Permian System," … ."
^Henderson, C. M.; Davydov and, V. I.; Wardlaw, B. R.; Gradstein, F. M.; Hammer, O. (2012-01-01), Gradstein, Felix M.; Ogg, James G.; Schmitz, Mark D.; Ogg, Gabi M. (eds.),"Chapter 24 - The Permian Period",The Geologic Time Scale, Boston: Elsevier, pp. 653–679,doi:10.1016/b978-0-444-59425-9.00024-x,ISBN978-0-444-59425-9,archived from the original on 2022-02-01, retrieved2022-02-01,In 1841, after a tour of Russia with French paleontologist Edouard de Verneuil, Roderick I. Murchison, in collabo- ration with Russian geologists, named the Permian System
^Henderson, C. M.; Davydov and, V. I.; Wardlaw, B. R.; Gradstein, F. M.; Hammer, O. (2012-01-01), Gradstein, Felix M.; Ogg, James G.; Schmitz, Mark D.; Ogg, Gabi M. (eds.),"Chapter 24 - The Permian Period",The Geologic Time Scale, Boston: Elsevier, p. 654,doi:10.1016/b978-0-444-59425-9.00024-x,ISBN978-0-444-59425-9,archived from the original on 2022-02-01, retrieved2022-02-01,He proposed the name "Permian" based on the extensive region that composed the ancient kingdom of Permia; the city of Perm lies on the flanks of the Urals.
^Glenister BF., Wardlaw BR., Lambert LL., Spinosa C., Bowring SA., Erwin DH., Menning M., Wilde GL. 1999. Proposal of Guadalupian and component Roadian, Wordian and Capitanian stages as international standards for the middle Permian series. Permophiles 34:3-11
^"Permian: Stratigraphy".UC Museum of Paleontology. University of California Berkeley.Archived from the original on 5 February 2022. Retrieved17 June 2021.
^Xu, R. & Wang, X.-Q. (1982): Di zhi shi qi Zhongguo ge zhu yao Diqu zhi wu jing guan (Reconstructions of Landscapes in Principal Regions of China). Ke xue chu ban she, Beijing. 55 pages, 25 plates.
^abHuttenlocker, A. K., and E. Rega. 2012. The Paleobiology and Bone Microstructure of Pelycosaurian-grade Synapsids. Pp. 90–119 in A. Chinsamy (ed.) Forerunners of Mammals: Radiation, Histology, Biology. Indiana University Press.
^Lozovsky, Vladlen R. (1 January 2005)."Olson's gap or Olson's bridge, that is the question".New Mexico Museum of Natural History and Science Bulletin. 30, The Nonmarine Permian. New Mexico Museum of Natural History and Science:179–184.
^Laurin, Michel; Hook, Robert W. (2022). "The age of North America's youngest Paleozoic continental vertebrates: a review of data from the Middle Permian Pease River (Texas) and El Reno (Oklahoma) Groups".BSGF - Earth Sciences Bulletin.193: 10.doi:10.1051/bsgf/2022007.
^abKoot, Martha B.; Cuny, Gilles; Tintori, Andrea; Twitchett, Richard J. (March 2013). "A new diverse shark fauna from the Wordian (Middle Permian) Khuff Formation in the interior Haushi-Huqf area, Sultanate of Oman: CHONDRICHTHYANS FROM THE WORDIAN KHUFF FORMATION OF OMAN".Palaeontology.56 (2):303–343.doi:10.1111/j.1475-4983.2012.01199.x.S2CID86428264.
^McLoughlin, S (2012). "Glossopteris – insights into the architecture and relationships of an iconic Permian Gondwanan plant".Journal of the Botanical Society of Bengal.65 (2):1–14.
^Kump, L.R.; Pavlov, A.; Arthur, M.A. (2005). "Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia".Geology.33 (May):397–400.Bibcode:2005Geo....33..397K.doi:10.1130/G21295.1.S2CID34821866.
^Benton, Michael J.; Twitchett, Richard J. (7 July 2003). "How to kill (almost) all life: the end-Permian extinction event".Trends in Ecology and Evolution.18 (7):358–365.doi:10.1016/S0169-5347(03)00093-4.
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