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222-569: The Triassic began in the wake of the Permian–Triassic extinction event , which left the Earth's biosphere impoverished; it was well into the middle of the Triassic before life recovered its former diversity. Three categories of organisms can be distinguished in the Triassic record: survivors from the extinction event, new groups that flourished briefly, and other new groups that went on to dominate

444-630: A bolide impact, for which an impact crater containing Manicouagan Reservoir in Quebec , Canada , has been singled out. However, the Manicouagan impact melt has been dated to 214±1 Mya. The date of the Triassic-Jurassic boundary has also been more accurately fixed recently, at 201.4 Mya. Both dates are gaining accuracy by using more accurate forms of radiometric dating, in particular the decay of uranium to lead in zircons formed at time of

666-567: A cosmopolitan distribution . Coelacanths show their highest post- Devonian diversity in the Early Triassic . Ray-finned fishes (actinopterygians) went through a remarkable diversification in the beginning of the Triassic, leading to peak diversity during the Middle Triassic; however, the pattern of this diversification is still not well understood due to a taphonomic megabias . The first stem-group teleosts appeared during

888-620: A brief period of domination in the early Spathian, probably related to a transient oxygenation of deep waters. Neospathodid conodonts survived the crisis but underwent proteromorphosis. In the PTME's aftermath, disaster taxa of benthic foraminifera filled many of their vacant niches. The recovery of benthic foraminifera was very slow and frequently interrupted until the Spathian. In the Tethys, foraminiferal communities remained low in diversity into

1110-567: A ceiling limiting the maximum ecological complexity of marine ecosystems until the Spathian. Recovery biotas appear to have been ecologically uneven and unstable into the Anisian , making them vulnerable to environmental stresses. Whereas most marine communities were fully recovered by the Middle Triassic, global marine diversity reached pre-extinction values no earlier than the Middle Jurassic, approximately 75 million years after

1332-553: A chain of mountain ranges stretching from Turkey to Malaysia . Pangaea was fractured by widespread faulting and rift basins during the Triassic—especially late in that period—but had not yet separated. The first nonmarine sediments in the rift that marks the initial break-up of Pangaea, which separated eastern North America from Morocco , are of Late Triassic age; in the United States , these thick sediments comprise

1554-642: A complex series of orogenic events assembled the eastern parts of Gondwana (eastern Africa, Arabian-Nubian Shield, Seychelles, Madagascar, India, Sri Lanka, East Antarctica, and Australia) c. 750 to 530 Ma . First, the Arabian-Nubian Shield collided with eastern Africa (in the Kenya-Tanzania region) in the East African Orogeny c. 750 to 620 Ma . Then Australia and East Antarctica were merged with

1776-599: A continuous arc chain, the direction of subduction was different between the Australian-Tasmanian and New Zealand-Antarctica arc segments. Many terranes were accreted to Eurasia during Gondwana's existence, but the Cambrian or Precambrian origin of many of these terranes remains uncertain. For example, some Palaeozoic terranes and microcontinents that now make up Central Asia, often called the "Kazakh" and "Mongolian terranes", were progressively amalgamated into

1998-746: A diversified assemblage of true insects. In Gondwana, in contrast, ice and, in Australia, volcanism decimated the Devonian flora to a low-diversity seed fern flora – the pteridophytes were increasingly replaced by the gymnosperms which were to dominate until the Mid-Cretaceous. Australia, however, was still located near the Equator during the Early Carboniferous, and during this period, temnospondyl and lepospondyl amphibians and

2220-513: A family of large-size fusuline foraminifera . The impact of the end-Guadalupian extinction on marine organisms appears to have varied between locations and between taxonomic groups – brachiopods and corals had severe losses. Marine invertebrates suffered the greatest losses during the P–Tr extinction. Evidence of this was found in samples from south China sections at the P–Tr boundary. Here, 286 out of 329 marine invertebrate genera disappear within

2442-469: A few exposures in the west. During the Triassic peneplains are thought to have formed in what is now Norway and southern Sweden. Remnants of this peneplain can be traced as a tilted summit accordance in the Swedish West Coast . In northern Norway Triassic peneplains may have been buried in sediments to be then re-exposed as coastal plains called strandflats . Dating of illite clay from

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2664-472: A few million years, reached its peak at c. 200 Ma , and coincided with the Triassic–Jurassic extinction event . The reformed Gondwanan continent was not precisely the same as that which had existed before Pangaea formed; for example, most of Florida and southern Georgia and Alabama is underlain by rocks that were originally part of Gondwana, but this region stayed attached to North America when

2886-538: A gradual decline during the Triassic while ferns, though never dominant, managed to diversify. The brief period of icehouse conditions during the Triassic–Jurassic extinction event had a dramatic impact on dinosaurs but left plants largely unaffected. The Jurassic was mostly one of hot-house conditions and, while vertebrates managed to diversify in this environment, plants have left little evidence of such development, apart from Cheiroleidiacean conifers and Caytoniales and other groups of seed ferns. In terms of biomass,

3108-581: A great reduction in their geographic range. Following this transition, coal swamps vanished. The North Chinese floral extinction correlates with the decline of the Gigantopteris flora of South China. In South China, the subtropical Cathaysian gigantopterid dominated rainforests abruptly collapsed. The floral extinction in South China is associated with bacterial blooms in soil and nearby lacustrine ecosystems, with soil erosion resulting from

3330-420: A high background extinction rate (by implication, taxa with a high turnover ). The extinction rate of marine organisms was catastrophic. Bioturbators were extremely severely affected, as evidenced by the loss of the sedimentary mixed layer in many marine facies during the end-Permian extinction. Surviving marine invertebrate groups included articulate brachiopods (those with a hinge), which had undergone

3552-474: A lake-dominated Triassic world rather than an earliest Triassic zone of death and decay in some terrestrial fossil beds. Newer chemical evidence agrees better with a fungal origin for Reduviasporonites , diluting these critiques. Uncertainty exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Some evidence suggests that there were multiple extinction pulses or that

3774-471: A long beak-like snout), and Shringasaurus (a horned herbivore which reached a body length of 3–4 metres (9.8–13.1 ft)). One group of archosauromorphs, the archosauriforms , were distinguished by their active predatory lifestyle, with serrated teeth and upright limb postures. Archosauriforms were diverse in the Triassic, including various terrestrial and semiaquatic predators of all shapes and sizes. The large-headed and robust erythrosuchids were among

3996-509: A massive rearrangement of ecosystems does occur, with plant abundances and distributions changing profoundly and all the forests virtually disappearing. The dominant floral groups changed, with many groups of land plants entering abrupt decline, such as Cordaites ( gymnosperms ) and Glossopteris ( seed ferns ). The severity of plant extinction has been disputed. The Glossopteris -dominated flora that characterised high-latitude Gondwana collapsed in Australia around 370,000 years before

4218-518: A north-east motion about 90 million years ago. While subduction direction changed, it remained oblique (and not perpendicular) to the coast of South America, and the direction change affected several subduction zone -parallel faults including Atacama , Domeyko and Liquiñe-Ofqui . Insular India began to collide with Asia circa 70 Ma , forming the Indian subcontinent , since which more than 1,400 km (870 mi) of crust has been absorbed by

4440-639: A number of species related to those of the laurissilva of Valdivia, through the connection of the Antarctic flora . These include gymnosperms and the deciduous species of Nothofagus , as well as the New Zealand laurel, Corynocarpus laevigatus , and Laurelia novae-zelandiae . New Caledonia and New Zealand became separated from Australia by continental drift 85 million years ago. The islands still retain plants that originated in Gondwana and spread to

4662-544: A pattern that reflects the Jurassic break-up of Pangaea. The Cretaceous saw the arrival of the angiosperms , or flowering plants, a group that probably evolved in western Gondwana (South America–Africa). From there the angiosperms diversified in two stages: the monocots and magnoliids evolved in the Early Cretaceous, followed by the hammamelid dicots . By the Mid-Cretaceous, angiosperms constituted half of

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4884-521: A peak in biodiversity – the end-Permian extinction was enormous and so was the radiation that followed. Two families of conifers, Podocarpaceae and Araucariaceae , dominated Gondwana in the Early Triassic, but Dicroidium , an extinct genus of fork-leaved seed ferns, dominated woodlands and forests of Gondwana during most of the Triassic. Conifers evolved and radiated during the period, with six of eight extant families already present before

5106-617: A pseudosuchian. Pseudosuchians were far more ecologically dominant in the Triassic, including large herbivores (such as aetosaurs ), large carnivores (" rauisuchians "), and the first crocodylomorphs (" sphenosuchians "). Aetosaurs were heavily-armored reptiles that were common during the last 30 million years of the Late Triassic until they died out at the Triassic-Jurassic extinction. Most aetosaurs were herbivorous and fed on low-growing plants, but some may have eaten meat. " rauisuchians " (formally known as paracrocodylomorphs ) were

5328-853: A series of events severally restricted the Proto-ACC: change to shallow marine conditions along the North Scotia Ridge; closure of the Fuegan Seaway, the deep sea that existed in Tierra del Fuego; and uplift of the Patagonian Cordillera. This, together with the reactivated Iceland plume , contributed to global warming. During the Miocene, the Drake Passage began to widen, and as water flow between South America and

5550-553: A severe bottleneck in diversity. Evidence from South China indicates the foraminiferal extinction had two pulses. Foraminiferal biodiversity hotspots shifted into deeper waters during the PTME. Approximately 93% of latest Permian foraminifera became extinct, with 50% of the clade Textulariina, 92% of Lagenida, 96% of Fusulinida, and 100% of Miliolida disappearing. Foraminifera that were calcaerous suffered an extinction rate of 91%. The reason why lagenides survived while fusulinoidean fusulinides went completely extinct may have been due to

5772-458: A short period of time, becoming extinct about 220 million years ago. They were exceptionally abundant in the middle of the Triassic, as the primary large herbivores in many Carnian-age ecosystems. They sheared plants with premaxillary beaks and plates along the upper jaw with multiple rows of teeth. Allokotosaurs were iguana-like reptiles, including Trilophosaurus (a common Late Triassic reptile with three-crowned teeth), Teraterpeton (which had

5994-694: A single jaw from Australia. The closure of the Rheic Ocean and the formation of Pangaea in the Carboniferous resulted in the rerouting of ocean currents that initiated an Ice House period. As Gondwana began to rotate clockwise, Australia shifted south to more temperate latitudes. An ice cap initially covered most of southern Africa and South America but spread to eventually cover most of the supercontinent, save for northernmost Africa-South America and eastern Australia. Giant lycopod and horsetail forests continued to evolve in tropical Laurasia together with

6216-481: A slow decline in numbers since the P–Tr extinction; the Ceratitida order of ammonites ; and crinoids ("sea lilies"), which very nearly became extinct but later became abundant and diverse. The groups with the highest survival rates generally had active control of circulation , elaborate gas exchange mechanisms, and light calcification; more heavily calcified organisms with simpler breathing apparatuses suffered

6438-511: A specialized subgroup of cynodonts, appeared during the Triassic and would survive the extinction event, allowing them to radiate during the Jurassic. Amphibians were primarily represented by the temnospondyls , giant aquatic predators that had survived the end-Permian extinction and saw a new burst of diversification in the Triassic, before going extinct by the end; however, early crown-group lissamphibians (including stem-group frogs , salamanders and caecilians ) also became more common during

6660-406: A specific region were more likely to go extinct than cosmopolitan taxa. There was little latitudinal difference in the survival rates of taxa. Organisms that inhabited refugia less affected by global warming experienced lesser or delayed extinctions. Among benthic organisms the extinction event multiplied background extinction rates , and therefore caused maximum species loss to taxa that had

6882-448: A strandflat of Bømlo , southern Norway, have shown that landscape there became weathered in Late Triassic times ( c. 210 million years ago) with the landscape likely also being shaped during that time. Eustatic sea level in the Triassic was consistently low compared to the other geological periods. The beginning of the Triassic was around present sea level, rising to about 10–20 metres (33–66 ft) above present-day sea level during

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7104-590: A study of the Shangsi section showed two extinction pulses with different causes too. Recent research shows that different groups became extinct at different times; for example, while difficult to date absolutely, ostracod and brachiopod extinctions were separated by around 670,000 to 1.17 million years. Palaeoenvironmental analysis of Lopingian strata in the Bowen Basin of Queensland indicates numerous intermittent periods of marine environmental stress from

7326-584: A supercontinent has less shoreline compared to a series of smaller continents, Triassic marine deposits are relatively uncommon on a global scale. A major exception is in Western Europe , where the Triassic was first studied. The northeastern margin of Gondwana was a stable passive margin along the Neo-Tethys Ocean, and marine sediments have been preserved in parts of northern India and Arabia . In North America , marine deposits are limited to

7548-467: Is a recent study of North American faunas. In the Petrified Forest of northeast Arizona there is a unique sequence of late Carnian-early Norian terrestrial sediments. An analysis in 2002 found no significant change in the paleoenvironment. Phytosaurs , the most common fossils there, experienced a change-over only at the genus level, and the number of species remained the same. Some aetosaurs ,

7770-496: Is another point of controversy. Evidence from a well-preserved sequence in east Greenland suggests that the terrestrial and marine extinctions began simultaneously. In this sequence, the decline of animal life is concentrated in a period approximately 10,000 to 60,000 years long, with plants taking an additional several hundred thousand years to show the full impact of the event. Many sedimentary sequences from South China show synchronous terrestrial and marine extinctions. Research in

7992-508: Is likely a paraphyletic group rather than a true clade. Tanystropheids were a family of protorosaurs which elevated their neck size to extremes, with the largest genus Tanystropheus having a neck longer than its body. The protorosaur family Sharovipterygidae used their elongated hindlimbs for gliding. Other archosauromorphs, such as rhynchosaurs and allokotosaurs , were mostly stocky-bodied herbivores with specialized jaw structures. Rhynchosaurs, barrel-gutted herbivores, thrived for only

8214-600: Is likely attributable to their ability to thrive in a wide range of environmental conditions. Conodonts saw a rapid recovery during the Induan, with anchignathodontids experiencing a diversity peak in the earliest Induan. Gondolellids diversified at the end of the Griesbachian; this diversity spike was most responsible for the overall conodont diversity peak in the Smithian. Segminiplanate conodonts again experienced

8436-451: Is likely that post-extinction microbial mats played a vital, indispensable role in the survival and recovery of various bioturbating organisms. The microbialite refuge hypothesis has been criticised as reflecting a taphonomic bias due to the greater preservation potential of microbialite deposits, however, rather than a genuine phenomenon. Ichnocoenoses show that marine ecosystems recovered to pre-extinction levels of ecological complexity by

8658-468: Is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate , providing a climate suitable for forests and vertebrates, including reptiles. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. The strong contrast between the Pangea supercontinent and

8880-818: Is now the Transantarctic Mountains ): the Antarctic Peninsula , Marie Byrd Land , Zealandia , and Thurston Island ; the Falkland Islands and Ellsworth–Whitmore Mountains (in Antarctica) were rotated 90° in opposite directions; and South America south of the Gastre Fault (often referred to as Patagonia ) was pushed westward. The history of the Africa-Antarctica break-up can be studied in great detail in

9102-576: Is now the southern Weddell Sea where initial break-up occurred during the Jurassic c. 180 to 160 Ma . Gondwana began to break up in the early Jurassic following the extensive and fast emplacement of the Karoo-Ferrar flood basalts c. 184 Ma . Before the Karoo plume initiated rifting between Africa and Antarctica , it separated a series of smaller continental blocks from Gondwana's southern, Proto-Pacific margin (along what

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9324-541: Is presumed to have been linked to the subduction of cold oceanic lithosphere . During the mid to Late Cretaceous ( c.  90 million years ago ), the Andean orogeny changed significantly in character. Warmer and younger oceanic lithosphere is believed to have started to be subducted beneath South America around this time. Such kind of subduction is held responsible not only for the intense contractional deformation that different lithologies were subject to, but also

9546-459: Is superimposed by 22 sea level drop events widespread in the geologic record, mostly of minor (less than 25-metre (82 ft)) and medium (25–75-metre (82–246 ft)) magnitudes. A lack of evidence for Triassic continental ice sheets suggest that glacial eustasy is unlikely to be the cause of these changes. The Triassic continental interior climate was generally hot and dry, so that typical deposits are red bed sandstones and evaporites . There

9768-513: Is that the main cause of the extinction was the flood basalt volcanic eruptions that created the Siberian Traps , which released sulfur dioxide and carbon dioxide , resulting in euxinia (oxygen-starved, sulfurous oceans), elevating global temperatures, and acidifying the oceans . The level of atmospheric carbon dioxide rose from around 400 ppm to 2,500 ppm with approximately 3,900 to 12,000 gigatonnes of carbon being added to

9990-410: Is usually divided into Early , Middle , and Late Triassic Epochs , and the corresponding rocks are referred to as Lower, Middle, or Upper Triassic. The faunal stages from the youngest to oldest are: During the Triassic, almost all the Earth's land mass was concentrated into a single supercontinent , Pangaea ( lit.   ' entire land ' ). This supercontinent was more-or-less centered on

10212-787: The Antarctic Peninsula increased, the renewed ACC resulted in cooler global climate. Since the Eocene, the northward movement of the Australian Plate has resulted in an arc-continent collision with the Philippine and Caroline plates and the uplift of the New Guinea Highlands . From the Oligocene to the late Miocene, the climate in Australia, dominated by warm and humid rainforests before this collision, began to alternate between open forest and rainforest before

10434-580: The Araguainha crater and caused seismic release of methane and the destruction of the ozone layer with increased exposure to solar radiation. Previously, it was thought that rock sequences spanning the Permian–Triassic boundary were too few and contained too many gaps for scientists to reliably determine its details. However, it is now possible to date the extinction with millennial precision. U–Pb zircon dates from five volcanic ash beds from

10656-1075: The Australian Plate are now separated by the Capricorn Plate and its diffuse boundaries. During the opening of the Indian Ocean, the Kerguelen hotspot first formed the Kerguelen Plateau on the Antarctic Plate c. 118 to 95 Ma and then the Ninety East Ridge on the Indian Plate at c. 100 Ma . The Kerguelen Plateau and the Broken Ridge , the southern end of the Ninety East Ridge, are now separated by

10878-650: The Cambrian explosion occurred. Laurentia was docked against the western shores of a united Gondwana for a brief period near the Precambrian/Cambrian boundary, forming the short-lived and still disputed supercontinent Pannotia . The Mozambique Ocean separated the Congo – Tanzania – Bangweulu Block of central Africa from Neoproterozoic India (India, the Antongil Block in far eastern Madagascar,

11100-844: The Campbell Plateau , Chatham Rise , Lord Howe Rise , Norfolk Ridge , and New Caledonia , from West Antarctica c. 84 Ma . The opening of the South Atlantic Ocean divided West Gondwana (South America and Africa), but there is considerable debate over the exact timing of this break-up. Rifting propagated from south to north along Triassic–Early Jurassic lineaments, but intra-continental rifts also began to develop within both continents in Jurassic–Cretaceous sedimentary basins, subdividing each continent into three sub-plates. Rifting began c. 190 Ma at Falkland latitudes, forcing Patagonia to move relative to

11322-578: The Carnian (early part of the Late Triassic), some advanced cynodonts gave rise to the first mammals . During the Triassic, archosaurs displaced therapsids as the largest and most ecologically prolific terrestrial amniotes. This "Triassic Takeover" may have contributed to the evolution of mammals by forcing the surviving therapsids and their mammaliaform successors to live as small, mainly nocturnal insectivores . Nocturnal life may have forced

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11544-550: The Central Atlantic opened . Antarctica, the centre of the supercontinent, shared boundaries with all other Gondwana continents and the fragmentation of Gondwana propagated clockwise around it. The break-up was the result of the eruption of the Karoo-Ferrar igneous province , one of the Earth's most extensive large igneous provinces (LIP) c. 200 to 170 Ma , but the oldest magnetic anomalies between South America, Africa, and Antarctica are found in what

11766-834: The Drake Passage and the deepening of the Tasman Gateway. The oldest oceanic crust in the Drake Passage, however, is 34 to 29 Ma -old which indicates that the spreading between the Antarctic and South American plates began near the Eocene/Oligocene boundary. Deep sea environments in Tierra del Fuego and the North Scotia Ridge during the Eocene and Oligocene indicate a "Proto-ACC" opened during this period. Later, 26 to 14 Ma ,

11988-402: The Global Stratotype Section and Point for the Permian–Triassic boundary at Meishan , China , establish a high-resolution age model for the extinction – allowing exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales. The first appearance of the conodont Hindeodus parvus has been used to delineate

12210-435: The Great American Interchange . The break-up of Gondwana can be said to continue in eastern Africa at the Afar Triple Junction , which separates the Arabian , Nubian , and Somali plates, resulting in rifting in the Red Sea and East African Rift . In the Early Cenozoic , Australia was still connected to Antarctica c. 35–40° south of its current location and both continents were largely unglaciated. A rift between

12432-401: The Himalayan - Tibetan orogen. During the Cenozoic, the orogen resulted in the construction of the Tibetan Plateau between the Tethyan Himalayas in the south and the Kunlun and Qilian mountains in the north. Later, South America was connected to North America via the Isthmus of Panama , cutting off a circulation of warm water and thereby making the Arctic colder, as well as allowing

12654-440: The Indian Subcontinent . Gondwana was formed by the accretion of several cratons (large stable blocks of the Earth's crust), beginning c.   800 to 650 Ma with the East African Orogeny , the collision of India and Madagascar with East Africa, and culminating in c.   600 to 530 Ma with the overlapping Brasiliano and Kuunga orogenies, the collision of South America with Africa, and

12876-445: The Industrial Revolution was 280 ppm , and the amount today is about 422 ppm ). There is also evidence of increased ultraviolet radiation reaching the earth, causing the mutation of plant spores. It has been suggested that the Permian–Triassic boundary is associated with a sharp increase in the abundance of marine and terrestrial fungi , caused by the sharp increase in the amount of dead plants and animals fed upon by

13098-434: The Jurassic , when the temnospondyls had become very rare. Most of the Reptiliomorpha , stem-amniotes that gave rise to the amniotes, disappeared in the Triassic, but two water-dwelling groups survived: Embolomeri that only survived into the early part of the period, and the Chroniosuchia , which survived until the end of the Triassic. The Permian–Triassic extinction devastated terrestrial life. Biodiversity rebounded as

13320-445: The Lake Lugano region of northern Italy and southern Switzerland , was in Middle Triassic times a lagoon behind reefs with an anoxic bottom layer, so there were no scavengers and little turbulence to disturb fossilization, a situation that can be compared to the better-known Jurassic Solnhofen Limestone lagerstätte . The remains of fish and various marine reptiles (including the common pachypleurosaur Neusticosaurus , and

13542-414: The Malagasy Orogeny in southern Madagascar) ( 550 Ma ), the collision between East Gondwana and East Africa in two steps, and the Brasiliano orogeny ( 660 to 530 Ma ), the successive collision between South American and African cratons . The last stages of Gondwanan assembly overlapped with the opening of the Iapetus Ocean between Laurentia and western Gondwana. During this interval,

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13764-448: The Mesozoic Era. Reptiles , especially archosaurs , were the chief terrestrial vertebrates during this time. A specialized group of archosaurs, called dinosaurs , first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic Period. Archosaurs that became dominant in this period were primarily pseudosuchians , relatives and ancestors of modern crocodilians , while some archosaurs specialized in flight,

13986-416: The Middle Triassic ) due to the severity of the extinction. However, studies in Bear Lake County , near Paris, Idaho , and nearby sites in Idaho and Nevada showed a relatively quick rebound in a localized Early Triassic marine ecosystem ( Paris biota ), taking around 1.3 million years to recover, while an unusually diverse and complex ichnobiota is known from Italy less than a million years after

14208-422: The Mozambique Belt , formed 800 to 650 Ma and was originally interpreted as the suture between East (India, Madagascar, Antarctica, and Australia) and West Gondwana (Africa and South America). Three orogenies were recognised during the 1990s as a result of data sets compiled on behalf of oil and mining companies: the East African Orogeny ( 650 to 800 Ma ) and Kuunga orogeny (including

14430-465: The Newark Supergroup . Rift basins are also common in South America, Europe, and Africa. Terrestrial environments are particularly well-represented in the South Africa, Russia, central Europe, and the southwest United States. Terrestrial Triassic biostratigraphy is mostly based on terrestrial and freshwater tetrapods, as well as conchostracans ("clam shrimps"), a type of fast-breeding crustacean which lived in lakes and hypersaline environments. Because

14652-418: The Olenekian and Anisian of Gondwana . Both kannemeyeriiform dicynodonts and gomphodont cynodonts remained important herbivores during much of the period. Therocephalians included both large predators ( Moschorhinus ) and herbivorous forms ( bauriids ) until their extinction midway through the period. Ecteniniid cynodonts played a role as large-sized, cursorial predators in the Late Triassic. During

14874-481: The Ordovician . This is the Cuyania or Precordillera terrane of the Famatinian orogeny in northwest Argentina which may have continued the line of the Appalachians southwards. Chilenia terrane accreted later against Cuyania. The collision of the Patagonian terrane with the southwestern Gondwanan occurred in the late Paleozoic. Subduction-related igneous rocks from beneath the North Patagonian Massif have been dated at 320–330 million years old, indicating that

15096-486: The Paleozoic and Mesozoic eras. It is Earth 's most severe known extinction event , with the extinction of 57% of biological families , 83% of genera, 81% of marine species and 70% of terrestrial vertebrate species. It is also the greatest known mass extinction of insects . It is the greatest of the "Big Five" mass extinctions of the Phanerozoic . There is evidence for one to three distinct pulses, or phases, of extinction. The scientific consensus

15318-481: The Pangaea supercontinent during the Carboniferous. Pangaea began to break up in the Mid-Jurassic when the Central Atlantic opened . In the western end of Pangaea, the collision between Gondwana and Laurasia closed the Rheic and Palaeo-Tethys oceans. The obliquity of this closure resulted in the docking of some northern terranes in the Marathon , Ouachita , Alleghanian , and Variscan orogenies, respectively. Southern terranes, such as Chortis and Oaxaca , on

15540-404: The Roadian (middle Permian), suffered a selective extinction pulse 10 million years before the main event, at the end of the Capitanian stage. In this preliminary extinction, which greatly reduced disparity , or the range of different ecological guilds, environmental factors were apparently responsible. Diversity and disparity fell further until the P–Tr boundary; the extinction here (P–Tr)

15762-483: The Seychelles , and the Napier and Rayner Complexes in East Antarctica ). The Azania continent (much of central Madagascar , the Horn of Africa and parts of Yemen and Arabia) was an island in the Mozambique Ocean. The continent Australia/ Mawson was still separated from India, eastern Africa, and Kalahari by c. 600 Ma , when most of western Gondwana had already been amalgamated. By c. 550 Ma, India had reached its Gondwanan position, which initiated

15984-756: The Southeast Indian Ridge . Separation between Australia and East Antarctica began c. 132 Ma with seafloor spreading occurring c. 96 Ma . A shallow seaway developed over the South Tasman Rise during the Early Cenozoic and as oceanic crust started to separate the continents during the Eocene c. 35.5 Ma global ocean temperature dropped significantly. A dramatic shift from arc- to rift magmatism c. 100 Ma separated Zealandia , including New Zealand ,

16206-579: The Triassic , and started to fragment during the Early Jurassic (around 180 million years ago). The final stages of break-up, involving the separation of Antarctica from South America (forming the Drake Passage ) and Australia, occurred during the Paleogene (from around 66 to 23 million years ago (Ma)). Gondwana was not considered a supercontinent by the earliest definition, since

16428-652: The Uralian orogeny and Laurasia . Pangaea was finally amalgamated in the Late Carboniferous-Early Permian, but the oblique forces continued until Pangaea began to rift in the Triassic. In the eastern end, collisions occurred slightly later. The North China , South China , and Indochina blocks rifted from Gondwana during the middle Paleozoic and opened the Proto-Tethys Ocean . North China docked with Mongolia and Siberia during

16650-605: The Variscan orogeny close to the Carboniferous–Permian boundary. South-east Asia was made of Gondwanan and Cathaysian continental fragments that were assembled during the Mid-Palaeozoic and Cenozoic. This process can be divided into three phases of rifting along Gondwana's northern margin: first, in the Devonian, North and South China , together with Tarim and Quidam (north-western China) rifted, opening

16872-406: The ocean acidification that resulted from increased atmospheric CO 2 . Organisms that relied on haemocyanin or haemoglobin for transporting oxygen were more resistant to extinction than those utilising haemerythrin or oxygen diffusion. There is also evidence that endemism was a strong risk factor influencing a taxon's likelihood of extinction. Bivalve taxa that were endemic and localised to

17094-454: The region in central India of the same name , which is derived from Sanskrit for "forest of the Gonds ". The name had been previously used in a geological context, first by H. B. Medlicott in 1872, from which the Gondwana sedimentary sequences ( Permian - Triassic ) are also described. Some scientists prefer the term "Gondwanaland" for the supercontinent to make a clear distinction between

17316-669: The surviving species repopulated empty terrain, but these were short-lived. Diverse communities with complex food-web structures took 30 million years to reestablish. Archosauromorph reptiles, which had already appeared and diversified to an extent in the Permian Period, exploded in diversity as an adaptive radiation in response to the Permian-Triassic mass extinction. By the Early Triassic, several major archosauromorph groups had appeared. Long-necked, lizard-like early archosauromorphs were known as protorosaurs , which

17538-468: The thecodonts ) disappeared, as did most of the large labyrinthodont amphibians, groups of small reptiles, and most synapsids. Some of the early, primitive dinosaurs also became extinct, but more adaptive ones survived to evolve into the Jurassic. Surviving plants that went on to dominate the Mesozoic world included modern conifers and cycadeoids. The cause of the Late Triassic extinction is uncertain. It

17760-437: The traversodont cynodonts—were much reduced in the northern half of Pangaea ( Laurasia ). These extinctions within the Triassic and at its end allowed the dinosaurs to expand into many niches that had become unoccupied. Dinosaurs became increasingly dominant, abundant and diverse, and remained that way for the next 150 million years. The true "Age of Dinosaurs" is during the following Jurassic and Cretaceous periods, rather than

17982-539: The uplift and erosion known to have occurred from the Late Cretaceous onward. Plate tectonic reorganisation since the mid-Cretaceous might also have been linked to the opening of the South Atlantic Ocean . Another change related to mid-Cretaceous plate tectonic rearrangement was the change of subduction direction of the oceanic lithosphere that went from having south-east motion to having

18204-832: The Anisian to Ladinian of the Tethysian domain, and from the Carnian and Rhaetian of a larger area that includes also the Boreal domain (e.g., Svalbard Islands), the North American continent, the South China block and Argentina . The best-studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event . The Early Triassic was the hottest portion of

18426-490: The Anisian. Metazoan reefs became common again during the Anisian because the oceans cooled down then from their overheated state during the Early Triassic. Biodiversity amongst metazoan reefs did not recover until well into the Anisian, millions of years after non-reef ecosystems recovered their diversity. Microbially induced sedimentary structures (MISS) from the earliest Triassic have been found to be associated with abundant opportunistic bivalves and vertical burrows, and it

18648-634: The Carboniferous–Permian, followed by South China. The Cimmerian blocks then rifted from Gondwana to form the Palaeo-Thethys and Neo-Tethys oceans in the Late Carboniferous, and docked with Asia during the Triassic and Jurassic. Western Pangaea began to rift while the eastern end was still being assembled. The formation of Pangaea and its mountains had a tremendous impact on global climate and sea levels, which resulted in glaciations and continent-wide sedimentation. In North America,

18870-404: The Carnian and include early sauropodomorphs and theropods. Most Triassic dinosaurs were small predators and only a few were common, such as Coelophysis , which was 1 to 2 metres (3.3 to 6.6 ft) long. Triassic sauropodomorphs primarily inhabited cooler regions of the world. The large predator Smok was most likely also an archosaur, but it is uncertain if it was a primitive dinosaur or

19092-530: The Early Cretaceous, and West Burma and Woyla during the Late Cretaceous. Gondwana's long, northern margin remained a mostly passive margin throughout the Palaeozoic. The Early Permian opening of the Neo-Tethys Ocean along this margin produced a long series of terranes, many of which were and still are being deformed in the Himalaya Orogeny . These terranes are, from Turkey to north-eastern India:

19314-501: The Early Triassic, forming small patches of reefs of modest extent compared to the great reef systems of Devonian or modern times. At the end of the Carnian, a reef crisis occurred in South China. Serpulids appeared in the Middle Triassic. Microconchids were abundant. The shelled cephalopods called ammonites recovered, diversifying from a single line that survived the Permian extinction. Bivalves began to rapidly diversify during

19536-402: The Early Triassic, while others (e.g. capitosaurs ) remained successful throughout the whole period, or only came to prominence in the Late Triassic (e.g. Plagiosaurus , metoposaurs ). The first Lissamphibians (modern amphibians) appear in the Triassic, with the progenitors of the first frogs already present by the Early Triassic. However, the group as a whole did not become common until

19758-712: The Early Triassic; and they dominated many surviving communities across the recovery from the mass extinction. Microbialite deposits appear to have declined in the early Griesbachian synchronously with a significant sea level drop that occurred then. Metazoan-built reefs reemerged during the Olenekian, mainly being composed of sponge biostrome and bivalve builups. Keratose sponges were particularly noteworthy in their integral importance to Early Triassic microbial-metazoan reef communities, and they helped to create stability in heavily damaged ecosystems during early phases of biotic recovery. " Tubiphytes "-dominated reefs appeared at

19980-562: The Early and Middle Triassic. Sea level rise accelerated in the Ladinian, culminating with a sea level up to 50 metres (164 ft) above present-day levels during the Carnian. Sea level began to decline in the Norian, reaching a low of 50 metres (164 ft) below present sea level during the mid-Rhaetian. Low global sea levels persisted into the earliest Jurassic. The long-term sea level trend

20202-628: The Equator during this period and remained a lifeless and barren landscape. West Gondwana drifted north during the Devonian , bringing Gondwana and Laurasia close together. Global cooling contributed to the Late Devonian extinction (19% of marine families and 50% of genera went extinct) and glaciation occurred in South America. Before Pangaea had formed, terrestrial plants, such as pteridophytes , began to diversify rapidly resulting in

20424-457: The Equator on landmasses then limited to Laurasia and, in Gondwana, to Australia. In the late Silurian, two distinctive lineages, zosterophylls and rhyniophytes , had colonised the tropics. The former evolved into the lycopods that were to dominate the Gondwanan vegetation over a long period, whilst the latter evolved into horsetails and gymnosperms . Most of Gondwana was located far from

20646-446: The Jurassic flora was dominated by conifer families and other gymnosperms that had evolved during the Triassic. The Pteridophytes that had dominated during the Palaeozoic were now marginalised, except for ferns. In contrast to Laurentia, very few insect fossils have been found in Gondwana, to a considerable extent because of widespread deserts and volcanism. While plants had a cosmopolitan distribution, dinosaurs evolved and diversified in

20868-402: The Jurassic. The Triassic was named in 1834 by Friedrich August von Alberti , after a succession of three distinct rock layers (Greek triás meaning 'triad') that are widespread in southern Germany : the lower Buntsandstein (colourful sandstone ) , the middle Muschelkalk (shell-bearing limestone ) and the upper Keuper (coloured clay ). On the geologic time scale , the Triassic

21090-613: The Jurassic. There were many types of marine reptiles. These included the Sauropterygia , which featured pachypleurosaurus and nothosaurs (both common during the Middle Triassic, especially in the Tethys region), placodonts , the earliest known herbivorous marine reptile Atopodentatus , and the first plesiosaurs . The first of the lizardlike Thalattosauria ( askeptosaurs ) and the highly successful ichthyopterygians , which appeared in Early Triassic seas, soon diversified. By

21312-752: The Karoo Basin indicates a protracted extinction lasting a million years. Other evidence from the Karoo deposits suggest it took 50,000 years or less, while a study of coprolites in the Vyazniki fossil beds in Russia suggests it took only a few thousand years. Aridification induced by global warming was the chief culprit behind terrestrial vertebrate extinctions. There is enough evidence to indicate that over two thirds of terrestrial labyrinthodont amphibians , sauropsid ("reptile") and therapsid ("proto-mammal") taxa became extinct. Large herbivores suffered

21534-646: The Kuunga orogeny (also known as the Pinjarra orogeny). Meanwhile, on the other side of the newly forming Africa, Kalahari collided with Congo and Rio de la Plata which closed the Adamastor Ocean . c. 540–530 Ma, the closure of the Mozambique Ocean brought India next to Australia–East Antarctica, and both North and South China were in proximity to Australia. As the rest of Gondwana formed,

21756-419: The Late Cretaceous to recover their full diversity. Crinoids ("sea lilies") suffered a selective extinction, resulting in a decrease in the variety of their forms. Though cladistic analyses suggest the beginning of their recovery to have taken place in the Induan, the recovery of their diversity as measured by fossil evidence was far less brisk, showing up in the late Ladinian. Their adaptive radiation after

21978-651: The Late Permian, many known from South Africa and Australia. Beetles and cockroaches remained minor elements in this fauna. Tetrapod fossils from the Early Permian have only been found in Laurasia but they became common in Gondwana later during the Permian. The arrival of the therapsids resulted in the first plant-vertebrate-insect ecosystem. During the Mid- to Late Triassic, hot-house conditions coincided with

22200-596: The Latest Olenekian Cooling (LOC), from 248 to 247 Ma, temperatures cooled by about 6 °C. The Middle Triassic was cooler than the Early Triassic, with temperatures falling over most of the Anisian, with the exception of a warming spike in the latter portion of the stage. From 242 to 233 Ma, the Ladinian-Carnian Cooling (LCC) ensued. At the beginning of the Carnian, global temperatures continued to be relatively cool. The eruption of

22422-484: The Middle Triassic, becoming highly abundant in the oceans. Aquatic insects rapidly diversified during the Middle Triassic, with this time interval representing a crucial diversification for Holometabola , the clade containing the majority of modern insect species. In the wake of the Permian-Triassic mass extinction event , the fish fauna was remarkably uniform, with many families and genera exhibiting

22644-617: The Middle Triassic, some ichthyopterygians were achieving very large body masses. Among other reptiles, the earliest turtles , like Proganochelys and Proterochersis , appeared during the Norian Age (Stage) of the Late Triassic Period. The Lepidosauromorpha , specifically the Sphenodontia , are first found in the fossil record of the earlier Carnian Age, though the earliest lepidosauromorphs likely occurred in

22866-514: The Middle Triassic, with the exception of a notable Ladinian fauna from the Catalonian Basin. Microbial reefs were common across shallow seas for a short time during the earliest Triassic, predominating in low latitudes while being rarer in higher latitudes, occurring both in anoxic and oxic waters. Polybessurus -like microfossils often dominated these earliest Triassic microbialites . Microbial-metazoan reefs appeared very early in

23088-460: The Miocene, a warm and humid climate developed with pockets of rainforests in central Australia, but before the end of the period, colder and drier climate severely reduced this rainforest. A brief period of increased rainfall in the Pliocene was followed by drier climate which favoured grassland. Since then, the fluctuation between wet interglacial periods and dry glacial periods has developed into

23310-763: The Neoproterozoic to Palaeozoic phase of the Terra Australis Orogen , a series of terranes were rafted from the proto-Andean margin when the Iapteus Ocean opened, to be added back to Gondwana during the closure of that ocean. During the Paleozoic, some blocks which helped to form parts of the Southern Cone of South America, include a piece transferred from Laurentia when the west edge of Gondwana scraped against southeast Laurentia in

23532-420: The PTME, being the most severely affected clade among the lophophorates. Deep water sponges suffered a significant diversity loss and exhibited a decrease in spicule size over the course of the PTME. Shallow water sponges were affected much less strongly; they experienced an increase in spicule size and much lower loss of morphological diversity compared to their deep water counterparts. Foraminifera suffered

23754-610: The PTME, but some tentative evidence suggests they may have survived into the Triassic. Freshwater and euryhaline fishes, having experienced minimal diversity losses before the PTME, were unaffected during the PTME and actually appear to have increased in diversity across the Permian-Triassic boundary. However, faunal turnovers in freshwater fish communities occurred in areas like the Kuznetsk Basin. The groups that survived suffered extremely heavy losses of species and some terrestrial vertebrate groups very nearly became extinct at

23976-517: The PTME. The Cordaites flora, which dominated the Angaran floristic realm corresponding to Siberia, collapsed over the course of the extinction. In the Kuznetsk Basin , the aridity-induced extinction of the regions's humid-adapted forest flora dominated by cordaitaleans occurred approximately 252.76 Ma, around 820,000 years before the end-Permian extinction in South China, suggesting that

24198-504: The Palaeo-Tethys behind them. These terranes accreted to Asia during Late Devonian and Permian. Second, in the Late Carboniferous to Early Permian, Cimmerian terranes opened Meso-Tethys Ocean; Sibumasu and Qiangtang were added to south-east Asia during Late Permian and Early Jurassic. Third, in the Late Triassic to Late Jurassic, Lhasa , West Burma , Woyla terranes opened the Neo-Tethys Ocean; Lhasa collided with Asia during

24420-447: The Permian extinction, Archaeplastida (red and green algae) had been the major marine phytoplanktons since about 659–645 million years ago, when they replaced marine planktonic cyanobacteria , which first appeared about 800 million years ago, as the dominant phytoplankton in the oceans. In the Triassic, secondary endosymbiotic algae became the most important plankton. In marine environments , new modern types of corals appeared in

24642-511: The Permian mass extinction event, both complex and simple marine ecosystems were equally common. After the recovery from the mass extinction, the complex communities outnumbered the simple communities by nearly three to one, and the increase in predation pressure and durophagy led to the Mesozoic Marine Revolution . Marine vertebrates recovered relatively quickly, with complex predator-prey interactions with vertebrates at

24864-447: The Permian-Triassic boundary are highly variable depending on the location and preservation quality of any given site. Plants are relatively immune to mass extinction, with the impact of all the major mass extinctions "insignificant" at a family level. Floral diversity losses were more superficial than those of marine animals. Even the reduction observed in species diversity (of 50%) may be mostly due to taphonomic processes. However,

25086-462: The Permian-Triassic boundary, with this flora's collapse being less constrained in western Gondwana but still likely occurring a few hundred thousand years before the boundary. The collapse of this flora is indirectly marked by an abrupt change in river morphology from meandering to braided river systems, signifying the widespread demise of rooted plants. Palynological or pollen studies from East Greenland of sedimentary rock strata laid down during

25308-494: The Permian-Triassic boundary. The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031 million years ago, a duration of 60 ± 48 thousand years. A large, abrupt global decrease in δ C , the ratio of the stable isotope carbon-13 to that of carbon-12 , coincides with this extinction, and is sometimes used to identify the Permian–Triassic boundary and PTME in rocks that are unsuitable for radiometric dating . The negative carbon isotope excursion's magnitude

25530-526: The Permian-Triassic mass extinction marked a key turning point in this ecological shift that began after the Capitanian mass extinction and culminated in the Late Jurassic . Typical taxa of shelly benthic faunas were now bivalves , snails , sea urchins and Malacostraca , whereas bony fishes and marine reptiles diversified in the pelagic zone . On land, dinosaurs and mammals arose in

25752-475: The Permian. The Procolophonidae , the last surviving parareptiles , were an important group of small lizard-like herbivores. The drepanosaurs were a clade of unusual, chameleon-like arboreal reptiles with birdlike heads and specialised claws. Three therapsid groups survived into the Triassic: dicynodonts , therocephalians , and cynodonts . The cynodont Cynognathus was a characteristic top predator in

25974-520: The Permian–Triassic boundary. The best-known record of vertebrate changes across the Permian–Triassic boundary occurs in the Karoo Supergroup of South Africa , but statistical analyses have so far not produced clear conclusions. One study of the Karoo Basin found that 69% of terrestrial vertebrates went extinct over 300,000 years leading up to the Permian-Triassic boundary, followed by a minor extinction pulse involving four taxa that survived

26196-575: The South Atlantic (Brazil and Cameroon ) dating to around 120  million years ago , suggesting that some form of land connection still existed between Africa and South America as recently as the early Aptian . The first phases of Andean orogeny in the Jurassic and Early Cretaceous were characterised by extensional tectonics , rifting , the development of back-arc basins and the emplacement of large batholiths . This development

26418-710: The Southern Hemisphere, has a "Gondwanan distribution" and is often described as an archaic, or relict , lineage. The distributions in the Proteaceae is, nevertheless, the result of both Gondwanan rafting and later oceanic dispersal. During the Silurian, Gondwana extended from the Equator (Australia) to the South Pole (North Africa and South America) whilst Laurasia was located on the Equator opposite to Australia. A short-lived Late Ordovician glaciation

26640-432: The Spathian and Anisian. Accordingly, low levels of interspecific competition in seafloor communities that are dominated by primary consumers correspond to slow rates of diversification and high levels of interspecific competition among nektonic secondary and tertiary consumers to high diversification rates. Other explanations state that life was delayed in its recovery because grim conditions returned periodically over

26862-437: The Spathian. Despite high taxonomic turnover, the ecological life modes of Early Triassic ostracods remained rather similar to those of pre-PTME ostracods. Bryozoans in the Early Triassic were restricted to the Boreal realm. They were also not diverse, represented mainly by members of Trepostomatida . During the Middle Triassic, there was a rise in bryozoan diversity, which peaked in the Carnian. However, bryozoans took until

27084-526: The Sydney Basin of the PTME's duration and course also supports a synchronous occurrence of the terrestrial and marine biotic collapses. Other scientists believe the terrestrial mass extinction began between 60,000 and 370,000 years before the onset of the marine mass extinction. Chemostratigraphic analysis from sections in Finnmark and Trøndelag shows the terrestrial floral turnover occurred before

27306-1113: The Taurides in southern Turkey; the Lesser Caucasus Terrane in Georgia; the Sanand, Alborz, and Lut terranes in Iran; the Mangysglak or Kopetdag Terrane in the Caspian Sea; the Afghan Terrane; the Karakorum Terrane in northern Pakistan; and the Lhasa and Qiangtang terranes in Tibet. The Permian–Triassic widening of the Neo-Tethys pushed all these terranes across the Equator and over to Eurasia. During

27528-406: The Triassic (teleosts are by far the most diverse group of fish today). Predatory actinopterygians such as saurichthyids and birgeriids , some of which grew over 1.2 m (3.9 ft) in length, appeared in the Early Triassic and became widespread and successful during the period as a whole. Lakes and rivers were populated by lungfish (Dipnoi), such as Ceratodus , which are mainly known from

27750-497: The Triassic and survived the extinction event. The earliest known neopterygian fish, including early holosteans and teleosts , appeared near the beginning of the Triassic, and quickly diversified to become among the dominant groups of fish in both freshwater and marine habitats. The vast supercontinent of Pangaea dominated the globe during the Triassic, but in the latest Triassic ( Rhaetian ) and Early Jurassic it began to gradually rift into two separate landmasses: Laurasia to

27972-609: The Triassic, enlarging the Neo-Tethys Ocean which formed in their wake. At the same time, they forced the Paleo-Tethys Ocean to shrink as it was being subducted under Asia. By the end of the Triassic, the Paleo-Tethys Ocean occupied a small area and the Cimmerian terranes began to collide with southern Asia. This collision, known as the Cimmerian Orogeny , continued into the Jurassic and Cretaceous to produce

28194-446: The Triassic, taking over niches that were filled primarily by brachiopods before the mass extinction event. Bivalves were once thought to have outcompeted brachiopods, but this outdated hypothesis about the brachiopod-bivalve transition has been disproven by Bayesian analysis . The success of bivalves in the aftermath of the extinction event may have been a function of them possessing greater resilience to environmental stress compared to

28416-729: The Triassic. Permian%E2%80%93Triassic extinction event Approximately 251.9 million years ago, the Permian–Triassic ( P–T , P–Tr ) extinction event ( PTME ; also known as the Late Permian extinction event , the Latest Permian extinction event , the End-Permian extinction event , and colloquially as the Great Dying ) forms the boundary between the Permian and Triassic geologic periods , and with them

28638-480: The Wrangellia Large Igneous Province around 234 Ma caused abrupt global warming, terminating the cooling trend of the LCC. This warming was responsible for the Carnian Pluvial Event and resulted in an episode of widespread global humidity. The CPE ushered in the Mid-Carnian Warm Interval (MCWI), which lasted from 234 to 227 Ma. At the Carnian-Norian boundary occurred a positive δC excursion believed to signify an increase in organic carbon burial. From 227 to 217 Ma, there

28860-401: The addition of Australia and Antarctica, respectively. Eventually, Gondwana became the largest piece of continental crust of the Palaeozoic Era, covering an area of some 100,000,000 km (39,000,000 sq mi), about one-fifth of the Earth's surface. It fused with Euramerica during the Carboniferous to form Pangea . It began to separate from northern Pangea ( Laurasia ) during

29082-550: The base of the Absaroka sequence coincides with the Alleghanian and Ouachita orogenies and are indicative of a large-scale change in the mode of deposition far away from the Pangaean orogenies. Ultimately, these changes contributed to the Permian–Triassic extinction event and left large deposits of hydrocarbons, coal, evaporite, and metals. The breakup of Pangaea began with the Central Atlantic magmatic province (CAMP) between South America, Africa, North America, and Europe. CAMP covered more than seven million square kilometres over

29304-401: The bizarre long-necked archosauromorph Tanystropheus ), along with some terrestrial forms like Ticinosuchus and Macrocnemus , have been recovered from this locality. All these fossils date from the Anisian and Ladinian ages (about 242 Ma ago). The Triassic Period ended with a mass extinction, which was particularly severe in the oceans; the conodonts disappeared, as did all

29526-423: The brachiopods that they coexisted with, whilst other studies have emphasised the greater niche breadth of the former. The rise of bivalves to taxonomic and ecological dominance over brachiopods was not synchronous, however, and brachiopods retained an outsized ecological dominance into the Middle Triassic even as bivalves eclipsed them in taxonomic diversity. Some researchers think the brachiopod-bivalve transition

29748-414: The colonisation of Gondwana. The Baragwanathia Flora, found only in the Yea Beds of Victoria, Australia, occurs in two strata separated by 1,700 m (5,600 ft) or 30 Ma; the upper assemblage is more diverse and includes Baragwanathia, the first primitive herbaceous lycopod to evolve from the zosterophylls. During the Devonian, giant club mosses replaced the Baragwanathia Flora, introducing

29970-492: The continent Kazakhstania in the late Silurian . Whether these blocks originated on the shores of Gondwana is not known. In the Early Palaeozoic, the Armorican terrane , which today form large parts of France, was part of either Peri-Gondwana or core Gondwana; the Rheic Ocean closed in front of it and the Palaeo-Tethys Ocean opened behind it. Precambrian rocks from the Iberian Peninsula suggest that it, too, formed part of core Gondwana before its detachment as an orocline in

30192-424: The continent became the arid or semiarid landscape it is today. The adjective "Gondwanan" is in common use in biogeography when referring to patterns of distribution of living organisms, typically when the organisms are restricted to two or more of the now-discontinuous regions that were once part of Gondwana, including the Antarctic flora . For example, the plant family Proteaceae , known from all continents in

30414-425: The course of the Triassic . The profound change in the taxonomic composition was partly a result of the selectivity of the extinction event, which affected some taxa (e.g., brachiopods ) more severely than others (e.g., bivalves ). However, recovery was also differential between taxa. Some survivors became extinct some million years after the extinction event without having rediversified ( dead clade walking , e.g.

30636-568: The course of the Early Triassic, causing further extinction events, such as the Smithian-Spathian boundary extinction . Continual episodes of extremely hot climatic conditions during the Early Triassic have been held responsible for the delayed recovery of oceanic life, in particular skeletonised taxa that are most vulnerable to high carbon dioxide concentrations. The relative delay in the recovery of benthic organisms has been attributed to widespread anoxia, but high abundances of benthic species contradict this explanation. A 2019 study attributed

30858-444: The dental plates, abundant in the fossils record. Hybodonts , a group of shark-like cartilaginous fish , were dominant in both freshwater and marine environments throughout the Triassic. Last survivors of the mainly Palaeozoic Eugeneodontida are known from the Early Triassic. Temnospondyl amphibians were among those groups that survived the Permian–Triassic extinction. Once abundant in both terrestrial and aquatic environments,

31080-559: The development of rifts systems on both continents, including the Central African Rift System and the Central African Shear Zone which lasted until c. 85 Ma . At Brazilian latitudes spreading is more difficult to assess because of the lack of palaeo-magnetic data, but rifting occurred in Nigeria at the Benue Trough c. 118 Ma . North of the Equator the rifting began after 120.4 Ma and continued until c. 100 to 96 Ma . Dinosaur footprints representing identical species assemblages are known from opposite sides of

31302-410: The die-off of plants being their likely cause. Wildfires too likely played a role in the fall of Gigantopteris . A conifer flora in what is now Jordan, known from fossils near the Dead Sea , showed unusual stability over the Permian-Triassic transition, and appears to have been only minimally affected by the crisis. The tempo of the terrestrial vertebrate extinction is disputed. Some evidence from

31524-423: The dissimilarity of recovery times between different ecological communities to differences in local environmental stress during the biotic recovery interval, with regions experiencing persistent environmental stress post-extinction recovering more slowly, supporting the view that recurrent environmental calamities were culpable for retarded biotic recovery. Recurrent Early Triassic environmental stresses also acted as

31746-428: The dominant carnivores in the early Triassic. Phytosaurs were a particularly common group which prospered during the Late Triassic. These long-snouted and semiaquatic predators resemble living crocodiles and probably had a similar lifestyle, hunting for fish and small reptiles around the water's edge. However, this resemblance is only superficial and is a prime-case of convergent evolution. True archosaurs appeared in

31968-405: The early Triassic, splitting into two branches: Avemetatarsalia (the ancestors to birds) and Pseudosuchia (the ancestors to crocodilians). Avemetatarsalians were a minor component of their ecosystems, but eventually produced the earliest pterosaurs and dinosaurs in the Late Triassic. Early long-tailed pterosaurs appeared in the Norian and quickly spread worldwide. Triassic dinosaurs evolved in

32190-437: The end of it. Bennettitales and Pentoxylales , two now extinct orders of gymnospermous plants, evolved in the Late Triassic and became important in the Jurassic and Cretaceous. It is possible that gymnosperm biodiversity surpassed later angiosperm biodiversity and that the evolution of angiosperms began during the Triassic but, if so, in Laurasia rather than in Gondwana. Two Gondwanan classes, lycophytes and sphenophytes , saw

32412-437: The end of the Olenekian, representing the earliest platform-margin reefs of the Triassic, though they did not become abundant until the late Anisian, when reefs' species richness increased. The first scleractinian corals appear in the late Anisian as well, although they would not become the dominant reef builders until the end of the Triassic period. Bryozoans, after sponges, were the most numerous organisms in Tethyan reefs during

32634-440: The end of the Permian. Some of the surviving groups did not persist for long past this period, but others that barely survived went on to produce diverse and long-lasting lineages. However, it took 30   million years for the terrestrial vertebrate fauna to fully recover both numerically and ecologically. It is difficult to analyze extinction and survival rates of land organisms in detail because few terrestrial fossil beds span

32856-439: The end-Capitanian had finished, depending on the factor considered. Many of the extinctions once dated to the Permian-Triassic boundary have more recently been redated to the end- Capitanian . Further, it is unclear whether some species who survived the prior extinction(s) had recovered well enough for their final demise in the Permian-Triassic event to be considered separate from Capitanian event. A minority point of view considers

33078-439: The end-Permian biotic catastrophe may have started earlier on land and that the ecological crisis may have been more gradual and asynchronous on land compared to its more abrupt onset in the marine realm. In North China, the transition between the Upper Shihhotse and Sunjiagou Formations and their lateral equivalents marked a very large extinction of plants in the region. Those plant genera that did not go extinct still experienced

33300-412: The end-Permian extinction. Additionally, the complex Guiyang biota found near Guiyang , China also indicates life thrived in some places just a million years after the mass extinction, as does a fossil assemblage known as the Shanggan fauna found in Shanggan, China, the Wangmo biota from the Luolou Formation of Guizhou, and a gastropod fauna from the Al Jil Formation of Oman. Regional differences in

33522-401: The entire Phanerozoic, seeing as it occurred during and immediately after the discharge of titanic volumes of greenhouse gases from the Siberian Traps. The Early Triassic began with the Permian-Triassic Thermal Maximum (PTTM) and was followed by the brief Dienerian Cooling (DC) from 251 to 249 Ma, which was in turn followed by the Latest Smithian Thermal Maximum (LSTT) around 249 to 248 Ma. During

33744-466: The equator and extended between the poles, though it did drift northwards as the period progressed. Southern Pangea, also known as Gondwana , was made up by closely-appressed cratons corresponding to modern South America , Africa , Madagascar , India , Antarctica , and Australia . North Pangea, also known as Laurussia or Laurasia , corresponds to modern-day North America and the fragmented predecessors of Eurasia . The western edge of Pangea lay at

33966-650: The eruption of the Deccan basalts , whose eruption site may survive as the Réunion hotspot . The Seychelles and the Maldives are now separated by the Central Indian Ridge . During the initial break-up in the Early Jurassic a marine transgression swept over the Horn of Africa covering Triassic planation surfaces with sandstone , limestone , shale , marls and evaporites . East Gondwana, comprising Antarctica, Madagascar, India, and Australia, began to separate from Africa. East Gondwana then began to break up c. 132.5 to 96 Ma when India moved northwest from Australia-Antarctica. The Indian Plate and

34188-439: The evolution of Voltziales , one of the few plant orders to survive the end-Permian extinction (57% of marine families and 83% of genera went extinct) and which came to dominate in the Late Permian and from whom true conifers evolved. Tall lycopods and horsetails dominated the wetlands of Gondwana in the Early Permian. Insects co-evolved with glossopterids across Gondwana and diversified with more than 200 species in 21 orders by

34410-498: The expansion of more habitable climatic zones. Brachiopod taxa during the Anisian recovery interval were only phylogenetically related to Late Permian brachiopods at a familial taxonomic level or higher; the ecology of brachiopods had radically changed from before in the mass extinction's aftermath. Ostracods were extremely rare during the basalmost Early Triassic. Taxa associated with microbialites were disproportionately represented among ostracod survivors. Ostracod recovery began in

34632-413: The extinct family Cheirolepidiaceae , which first appeared in the Late Triassic, and would be prominent throughout most of the rest of the Mesozoic. No known coal deposits date from the start of the Triassic Period. This is known as the Early Triassic "coal gap" and can be seen as part of the Permian–Triassic extinction event . Possible explanations for the coal gap include sharp drops in sea level at

34854-415: The extinction event resulted in forms possessing flexible arms becoming widespread; motility , predominantly a response to predation pressure, also became far more prevalent. Though their taxonomic diversity remained relatively low, crinoids regained much of their ecological dominance by the Middle Triassic epoch. Stem-group echinoids survived the PTME. The survival of miocidarid echinoids such as Eotiaris

35076-496: The extinction event. Prior to the extinction, about two-thirds of marine animals were sessile and attached to the seafloor. During the Mesozoic, only about half of the marine animals were sessile while the rest were free-living. Analysis of marine fossils from the period indicated a decrease in the abundance of sessile epifaunal suspension feeders such as brachiopods and sea lilies and an increase in more complex mobile species such as snails , sea urchins and crabs . Before

35298-409: The extinction period indicate dense gymnosperm woodlands before the event. At the same time that marine invertebrate macrofauna declined, these large woodlands died out and were followed by a rise in diversity of smaller herbaceous plants including Lycopodiophyta , both Selaginellales and Isoetales . Data from Kap Stosch suggest that floral species richness was not significantly affected during

35520-439: The extinction was long and spread out over a few million years, with a sharp peak in the last million years of the Permian. Statistical analyses of some highly fossiliferous strata in Meishan, Zhejiang Province in southeastern China, suggest that the main extinction was clustered around one peak, while a study of the Liangfengya section found evidence of two extinction waves, MEH-1 and MEH-2, which varied in their causes, and

35742-407: The final extinction killed off only about 80% of marine species alive at that time, whereas the other losses occurred during the first pulse or the interval between pulses. According to this theory, one of these extinction pulses occurred at the end of the Guadalupian epoch of the Permian. For example, all dinocephalian genera died out at the end of the Guadalupian, as did the Verbeekinidae ,

35964-409: The final two sedimentary zones containing conodonts from the Permian. The decrease in diversity was probably caused by a sharp increase in extinctions, rather than a decrease in speciation . The extinction primarily affected organisms with calcium carbonate skeletons, especially those reliant on stable CO 2 levels to produce their skeletons. These organisms were susceptible to the effects of

36186-452: The first amniote reptilians evolved, all closely related to the Laurasian fauna, but spreading ice eventually drove these animals away from Gondwana entirely. The Gondwana ice sheet melted, and sea levels dropped during the Permian and Triassic global warming. During this period, the extinct glossopterids colonised Gondwana and reached peak diversity in the Late Permian when coal-forming forests covered much of Gondwana. The period also saw

36408-406: The first time among vertebrates, becoming the pterosaurs . Therapsids , the dominant vertebrates of the preceding Permian period, saw a brief surge in diversification in the Triassic, with dicynodonts and cynodonts quickly becoming dominant, but they declined throughout the period with the majority becoming extinct by the end. However, the first stem-group mammals ( mammaliamorphs ), themselves

36630-402: The first trees, and by the Late Devonian this first forest was accompanied by the progymnosperms , including the first large trees Archaeopteris . The Late Devonian extinction probably also resulted in osteolepiform fishes evolving into the amphibian tetrapods , the earliest land vertebrates, in Greenland and Russia. The only traces of this evolution in Gondwana are amphibian footprints and

36852-459: The flora in northeastern Australia. There is, however, no obvious connection between this spectacular angiosperm radiation and any known extinction event nor with vertebrate/insect evolution. Insect orders associated with pollination, such as beetles , flies , butterflies and moths , and wasps, bees, and ants , radiated continuously from the Permian-Triassic, long before the arrival of the angiosperms. Well-preserved insect fossils have been found in

37074-433: The fracture zones and magnetic anomalies flanking the Southwest Indian Ridge . The Madagascar block and the Mascarene Plateau , stretching from the Seychelles to Réunion , were broken off India, causing Madagascar and Insular India to be separate landmasses : elements of this break-up nearly coincide with the Cretaceous–Paleogene extinction event . The India–Madagascar–Seychelles separations appear to coincide with

37296-405: The fungi. This "fungal spike" has been used by some paleontologists to identify a lithological sequence as being on or very close to the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating or have a lack of suitable index fossils . However, even the proposers of the fungal spike hypothesis pointed out that "fungal spikes" may have been a repeating phenomenon created by

37518-405: The global ocean triggered intense cross-equatorial monsoons , sometimes referred to as the Pangean megamonsoons . The Triassic may have mostly been a dry period, but evidence exists that it was punctuated by several episodes of increased rainfall in tropical and subtropical latitudes of the Tethys Sea and its surrounding land. Sediments and fossils suggestive of a more humid climate are known from

37740-441: The greater range of environmental tolerance and greater geographic distribution of the former compared to the latter. Cladodontomorph sharks likely survived the extinction by surviving in refugia in the deep oceans, a hypothesis based on the discovery of Early Cretaceous cladodontomorphs in deep, outer shelf environments. Ichthyosaurs , which evolved immediately before the PTME, were also PTME survivors. The Lilliput effect ,

37962-421: The greatest loss of species diversity. In the case of the brachiopods, at least, surviving taxa were generally small, rare members of a formerly diverse community. Conodonts were severely affected both in terms of taxonomic and morphological diversity, although not as severely as during the Capitanian mass extinction. The ammonoids , which had been in a long-term decline for the 30 million years since

38184-628: The heaviest losses. All Permian anapsid reptiles died out except the procolophonids (although testudines have morphologically -anapsid skulls, they are now thought to have separately evolved from diapsid ancestors). Pelycosaurs died out before the end of the Permian. Too few Permian diapsid fossils have been found to support any conclusion about the effect of the Permian extinction on diapsids (the "reptile" group from which lizards, snakes, crocodilians, and dinosaurs (including birds) evolved). Tangasaurids were largely unaffected. Gorgonopsians are traditionally thought to have gone extinct during

38406-419: The impact. So, the evidence suggests the Manicouagan impact preceded the end of the Triassic by approximately 10±2 Ma. It could not therefore be the immediate cause of the observed mass extinction. The number of Late Triassic extinctions is disputed. Some studies suggest that there are at least two periods of extinction towards the end of the Triassic, separated by 12 to 17 million years. But arguing against this

38628-423: The inarticulate brachiopod Lingularia , and the foraminifera Earlandia and Rectocornuspira kalhori , the latter of which is sometimes classified under the genus Ammodiscus . Their guild diversity was also low. Post-PTME faunas had a flat, insignificant latitudinal diversity gradient. The speed of recovery from the extinction is disputed. Some scientists estimate that it took 10 million years (until

38850-401: The keystone predators of most Triassic terrestrial ecosystems. Over 25 species have been found, including giant quadrupedal hunters, sleek bipedal omnivores, and lumbering beasts with deep sails on their backs. They probably occupied the large-predator niche later filled by theropods. "Rauisuchians" were ancestral to small, lightly-built crocodylomorphs, the only pseudosuchians which survived into

39072-571: The lake deposits of the Santana Formation in Brazil, the Koonwarra Lake fauna in Australia, and the Orapa diamond mine in Botswana. Dinosaurs continued to prosper but, as the angiosperm diversified, conifers, bennettitaleans and pentoxylaleans disappeared from Gondwana c. 115 Ma together with the specialised herbivorous ornithischians , whilst generalist browsers, such as several families of sauropodomorph Saurischia , prevailed. The Cretaceous–Paleogene extinction event killed off all dinosaurs except birds, but plant evolution in Gondwana

39294-403: The landmasses of Baltica , Laurentia , and Siberia were separated from it. To differentiate it from the Indian region of the same name (see § Name ), it is also commonly called Gondwanaland . Regions that were part of Gondwana shared floral and zoological elements that persist to the present day. The continent of Gondwana was named by the Austrian scientist Eduard Suess , after

39516-440: The large negative δ C shift during the marine extinction. Dating of the boundary between the Dicynodon and Lystrosaurus assemblage zones in the Karoo Basin indicates that the terrestrial extinction occurred earlier than the marine extinction. The Sunjiagou Formation of South China also records a terrestrial ecosystem demise predating the marine crisis. Other research still has found that the terrestrial extinction occurred after

39738-545: The late Olenekian. Anisian ichnocoenoses show slightly lower diversity than Spathian ichnocoenoses, although this was likely a taphonomic consequence of increased and deeper bioturbation erasing evidence of shallower bioturbation. Gondwana Gondwana ( / ɡ ɒ n d ˈ w ɑː n ə / ) was a large landmass, sometimes referred to as a supercontinent . The remnants of Gondwana make up around two-thirds of today's continental area, including South America , Africa , Antarctica , Australia , Zealandia , Arabia , and

39960-486: The mammaliaforms to develop fur and a higher metabolic rate . Two Early Triassic lagerstätten (high-quality fossil beds), the Dienerian aged Guiyang biota and the earliest Spathian aged Paris biota stand out due to their exceptional preservation and diversity . They represent the earliest lagerstätten of the Mesozoic era and provide insight into the biotic recovery from the Permian-Triassic mass extinction event. The Monte San Giorgio lagerstätte, now in

40182-572: The margin of an enormous ocean, Panthalassa ( lit.   ' entire sea ' ), which roughly corresponds to the modern Pacific Ocean . Practically all deep-ocean crust present during the Triassic has been recycled through the subduction of oceanic plates, so very little is known about the open ocean from this time period. Most information on Panthalassan geology and marine life is derived from island arcs and rare seafloor sediments accreted onto surrounding land masses, such as present-day Japan and western North America. The eastern edge of Pangea

40404-402: The marine extinction in the tropics. Studies of the timing and causes of the Permian-Triassic extinction are complicated by the often-overlooked Capitanian extinction (also called the Guadalupian extinction), just one of perhaps two mass extinctions in the late Permian that closely preceded the Permian-Triassic event. In short, when the Permian-Triassic starts it is difficult to know whether

40626-453: The marine reptiles except ichthyosaurs and plesiosaurs . Invertebrates like brachiopods and molluscs (such as gastropods ) were severely affected. In the oceans, 22% of marine families and possibly about half of marine genera went missing. Though the end-Triassic extinction event was not equally devastating in all terrestrial ecosystems, several important clades of crurotarsans (large archosaurian reptiles previously grouped together as

40848-608: The mass extinction, exemplifying the Lilliput effect's opposite, which has been dubbed the Brobdingnag effect. The Permian had great diversity in insect and other invertebrate species, including the largest insects ever to have existed. The end-Permian is the largest known mass extinction of insects; according to some sources, it may well be the only mass extinction to significantly affect insect diversity. Eight or nine insect orders became extinct and ten more were greatly reduced in diversity. Palaeodictyopteroids (insects with piercing and sucking mouthparts) began to decline during

41070-451: The mid-Permian; these extinctions have been linked to a change in flora. The greatest decline occurred in the Late Permian and was probably not directly caused by weather-related floral transitions. However, some observed entomofaunal declines in the PTME were biogeographic changes rather than outright extinctions. The geological record of terrestrial plants is sparse and based mostly on pollen and spore studies. Floral changes across

41292-428: The middle to late Lopingian leading up to the end-Permian extinction proper, supporting aspects of the gradualist hypothesis. Additionally, the decline in marine species richness and the structural collapse of marine ecosystems may have been decoupled as well, with the former preceding the latter by about 61,000 years according to one study. Whether the terrestrial and marine extinctions were synchronous or asynchronous

41514-430: The next most common tetrapods, and early dinosaurs, passed through unchanged. However, both phytosaurs and aetosaurs were among the groups of archosaur reptiles completely wiped out by the end-Triassic extinction event. It seems likely then that there was some sort of end-Carnian extinction, when several herbivorous archosauromorph groups died out, while the large herbivorous therapsids —the kannemeyeriid dicynodonts and

41736-452: The north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event , that wiped out many groups, including most pseudosuchians, and allowed dinosaurs to assume dominance in

41958-488: The ocean-atmosphere system during this period. Several other contributing factors have been proposed, including the emission of carbon dioxide from the burning of oil and coal deposits ignited by the eruptions; emissions of methane from the gasification of methane clathrates ; emissions of methane by novel methanogenic microorganisms nourished by minerals dispersed in the eruptions; longer and more intense El Niño events; and an extraterrestrial impact which created

42180-402: The order Isoetales (which contains living quillworts ), rose to prominence due to the environmental instability following the Permian-Triassic extinction, with one particularly notable example being the genus Pleuromeia , which grew in columnar like fashion, sometimes reaching a height of 2 metres (6.6 ft). The relevance of lycophytes declined from the Middle Triassic onwards, following

42402-513: The other hand, remained largely unaffected by the collision along the southern shores of Laurentia. Some Peri-Gondwanan terranes, such as Yucatán and Florida , were buffered from collisions by major promontories. Other terranes, such as Carolina and Meguma , were directly involved in the collision. The final collision resulted in the Variscan- Appalachian Mountains , stretching from present-day Mexico to southern Europe. Meanwhile, Baltica collided with Siberia and Kazakhstania which resulted in

42624-475: The pace of biotic recovery existed, which suggests that the impact of the extinction may have been felt less severely in some areas than others, with differential environmental stress and instability being the source of the variance. In addition, it has been proposed that although overall taxonomic diversity rebounded rapidly, functional ecological diversity took much longer to return to its pre-extinction levels; one study concluded that marine ecological recovery

42846-415: The parameters were now shared differently among clades . Ostracods experienced prolonged diversity perturbations during the Changhsingian before the PTME proper, when immense proportions of them abruptly vanished. At least 74% of ostracods died out during the PTME itself. Bryozoans had been on a long-term decline throughout the Late Permian epoch before they suffered even more catastrophic losses during

43068-516: The phenomenon of dwarfing of species during and immediately following a mass extinction event, has been observed across the Permian-Triassic boundary, notably occurring in foraminifera, brachiopods, bivalves, and ostracods. Though gastropods that survived the cataclysm were smaller in size than those that did not, it remains debated whether the Lilliput effect truly took hold among gastropods. Some gastropod taxa, termed "Gulliver gastropods", ballooned in size during and immediately following

43290-403: The post-extinction ecosystem during the earliest Triassic. The very idea of a fungal spike has been criticized on several grounds, including: Reduviasporonites , the most common supposed fungal spore, may be a fossilized alga ; the spike did not appear worldwide; and in many places it did not fall on the Permian–Triassic boundary. The Reduviasporonites may even represent a transition to

43512-414: The present arid regime. Australia has thus experienced various climate changes over a 15-million-year period with a gradual decrease in precipitation. The Tasman Gateway between Australia and Antarctica began to open c. 40 to 30 Ma . Palaeontological evidence indicates the Antarctic Circumpolar Current (ACC) was established in the Late Oligocene c. 23 Ma with the full opening of

43734-405: The previous extinction interval. Another study of latest Permian vertebrates in the Karoo Basin found that 54% of them went extinct due to the PTME. In the wake of the extinction event, the ecological structure of present-day biosphere evolved from the stock of surviving taxa. In the sea, the "Palaeozoic evolutionary fauna" declined while the "modern evolutionary fauna" achieved greater dominance;

43956-456: The quick recovery seen in nektonic organisms such as ammonoids , which exceeded pre-extinction diversities already two million years after the crisis, and conodonts, which diversified considerably over the first two million years of the Early Triassic. Recent work suggests that the pace of recovery was intrinsically driven by the intensity of competition among species, which drives rates of niche differentiation and speciation . That recovery

44178-404: The region and the supercontinent. The assembly of Gondwana was a protracted process during the Neoproterozoic and Paleozoic , which remains incompletely understood because of the lack of paleo-magnetic data. Several orogenies , collectively known as the Pan-African orogeny , caused the continental fragments of a much older supercontinent, Rodinia , to amalgamate. One of those orogenic belts,

44400-631: The remaining Gondwana c. 570 to 530 Ma in the Kuunga Orogeny. The later Malagasy orogeny at about 550–515 Mya affected Madagascar, eastern East Africa and southern India. In it, Neoproterozoic India collided with the already combined Azania and Congo–Tanzania–Bangweulu Block, suturing along the Mozambique Belt. The 18,000 km-long (11,000 mi) Terra Australis Orogen developed along Gondwana's western, southern, and eastern margins. Proto-Gondwanan Cambrian arc belts from this margin have been found in eastern Australia, Tasmania, New Zealand, and Antarctica. Though these belts formed

44622-414: The return of more stable environmental conditions. While having first appeared during the Permian, the extinct seed plant group Bennettitales first became a prominent element in global floras during the Late Triassic, a position they would hold for much of the Mesozoic. In the Southern Hemisphere landmasses of Gondwana, the tree Dicroidium , an extinct " seed fern " belong to the order Corystospermales

44844-412: The sequence of environmental disasters to have effectively constituted a single, prolonged extinction event, perhaps depending on which species is considered. This older theory, still supported in some recent papers, proposes that there were two major extinction pulses 9.4 million years apart, separated by a period of extinctions that were less extensive, but still well above the background level, and that

45066-417: The snail family Bellerophontidae ), whereas others rose to dominance over geologic times (e.g., bivalves). A cosmopolitanism event began immediately after the end-Permian extinction event. Marine post-extinction faunas were mostly species-poor and were dominated by few disaster taxa such as the bivalves Claraia , Unionites , Eumorphotis , and Promyalina , the conodonts Clarkina and Hindeodus ,

45288-491: The still static remainder of South America and Africa, and this westward movement lasted until the Early Cretaceous 126.7 Ma . From there rifting propagated northward during the Late Jurassic c. 150 Ma or Early Cretaceous c. 140 Ma most likely forcing dextral movements between sub-plates on either side. South of the Walvis Ridge and Rio Grande Rise the Paraná and Etendeka magmatics resulted in further ocean-floor spreading c. 130 to 135 Ma and

45510-399: The subduction process initiated in the early Carboniferous. This was relatively short-lived (lasting about 20 million years), and initial contact of the two landmasses occurred in the mid-Carboniferous, with broader collision during the early Permian. In the Devonian, an island arc named Chaitenia accreted to Patagonia in what is now south-central Chile. Gondwana and Laurasia formed

45732-452: The terminus of the Triassic, there was an extreme warming event referred to as the End-Triassic Thermal Event (ETTE), which was responsible for the Triassic-Jurassic mass extinction. Bubbles of carbon dioxide in basaltic rocks dating back to the end of the Triassic indicate that volcanic activity from the Central Atlantic Magmatic Province helped trigger climate change in the ETTE. During the Early Triassic, lycophytes , particularly those of

45954-525: The terrestrial species had mostly died out during the extinction event. The Triassic survivors were aquatic or semi-aquatic, and were represented by Tupilakosaurus , Thabanchuia , Branchiosauridae and Micropholis , all of which died out in Early Triassic, and the successful Stereospondyli , with survivors into the Cretaceous Period. The largest Triassic stereospondyls, such as Mastodonsaurus , were up to 4 to 6 metres (13 to 20 ft) in length. Some lineages (e.g. trematosaurs ) flourished briefly in

46176-510: The time of the Permo-Triassic boundary; acid rain from the Siberian Traps eruptions or from an impact event that overwhelmed acidic swamps; climate shift to a greenhouse climate that was too hot and dry for peat accumulation; evolution of fungi or herbivores that were more destructive of wetlands; the extinction of all plants adapted to peat swamps, with a hiatus of several million years before new plant species evolved that were adapted to peat swamps; or soil anoxia as oxygen levels plummeted. Before

46398-420: The top of the food web being known from coprolites five million years after the PTME. Post-PTME hybodonts exhibited extremely rapid tooth replacement. Ichthyopterygians appear to have ballooned in size extremely rapidly following the PTME. Bivalves rapidly recolonised many marine environments in the wake of the catastrophe. Bivalves were fairly rare before the P–Tr extinction but became numerous and diverse in

46620-439: The two developed but remained an embayment until the Eocene-Oligocene boundary when the Circumpolar Current developed and the glaciation of Antarctica began. Australia was warm and wet during the Palaeocene and dominated by rainforest. The opening of the Tasman Gateway at the Eocene-Oligocene boundary ( 33 Ma ) resulted in abrupt cooling but the Oligocene became a period of high rainfall with swamps in southeast Australia. During

46842-431: Was 4-7% and lasted for approximately 500 kyr, though estimating its exact value is challenging due to diagenetic alteration of many sedimentary facies spanning the boundary. Further evidence for environmental change around the Permian-Triassic boundary suggests an 8 °C (14 °F) rise in temperature, and an increase in CO 2 levels to 2,500  ppm (for comparison, the concentration immediately before

47064-424: Was a dominant element in forest habitats across the region during the Middle-Late Triassic. During the Late Triassic, the Ginkgoales (which today are represented by only a single species, Ginkgo biloba ) underwent considerable diversification. Conifers were abundant during the Triassic, and included the Voltziales (which contains various lineages, probably including those ancestral to modern conifers), as well as

47286-454: Was a relatively cool period known as the Early Norian Cool Interval (ENCI), after which occurred the Mid-Norian Warm Interval (MNWI) from 217 to 209 Ma. The MNWI was briefly interrupted around 214 Ma by a cooling possibly related to the Manicouagan impact . Around 212 Ma, a 10 Myr eccentricity maximum caused a paludification of Pangaea and a reduction in the size of arid climatic zones. The Rhaetian Cool Interval (RCI) lasted from 209 to 201 Ma. At

47508-413: Was accompanied by huge volcanic eruptions that occurred as the supercontinent Pangaea began to break apart about 202 to 191 million years ago (40Ar/39Ar dates), forming the Central Atlantic Magmatic Province (CAMP), one of the largest known inland volcanic events since the planet had first cooled and stabilized. Other possible but less likely causes for the extinction events include global cooling or even

47730-588: Was attributable not only to the end-Permian extinction but also the ecological restructuring that began as a result of the Capitanian extinction. Infaunal habits in bivalves became more common after the PTME. Linguliform brachiopods were commonplace immediately after the extinction event, their abundance having been essentially unaffected by the crisis. Adaptations for oxygen-poor and warm environments, such as increased lophophoral cavity surface, shell width/length ratio, and shell miniaturisation, are observed in post-extinction linguliforms. The surviving brachiopod fauna

47952-428: Was encroached upon by a pair of extensive oceanic basins: The Neo-Tethys (or simply Tethys) and Paleo-Tethys Oceans . These extended from China to Iberia, hosting abundant marine life along their shallow tropical peripheries. They were divided from each other by a long string of microcontinents known as the Cimmerian terranes . Cimmerian crust had detached from Gondwana in the early Permian and drifted northwards during

48174-424: Was followed by a Silurian Hot House period. The End-Ordovician extinction , which resulted in 27% of marine invertebrate families and 57% of genera going extinct, occurred during this shift from Ice House to Hot House. By the end of the Ordovician, Cooksonia , a slender, ground-covering plant, became the first known vascular plant to establish itself on land. This first colonisation occurred exclusively around

48396-475: Was hardly affected. Gondwanatheria is an extinct group of non- therian mammals with a Gondwanan distribution (South America, Africa, Madagascar, India, Zealandia and Antarctica) during the Late Cretaceous and Palaeogene. Xenarthra and Afrotheria , two placental clades, are of Gondwanan origin and probably began to evolve separately c. 105 Ma when Africa and South America separated. The laurel forests of Australia, New Caledonia, and New Zealand have

48618-410: Was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low. The range of morphospace occupied by the ammonoids, that is, their range of possible forms, shapes or structures, became more restricted as the Permian progressed. A few million years into the Triassic, the original range of ammonoid structures was once again reoccupied, but

48840-425: Was slow in the Early Triassic can be explained by low levels of biological competition due to the paucity of taxonomic diversity, and that biotic recovery explosively accelerated in the Anisian can be explained by niche crowding, a phenomenon that would have drastically increased competition, becoming prevalent by the Anisian. Biodiversity rise thus behaved as a positive feedback loop enhancing itself as it took off in

49062-519: Was still ongoing 50 million years after the extinction, during the latest Triassic, even though taxonomic diversity had rebounded in a tenth of that time. The pace and timing of recovery also differed based on clade and mode of life. Seafloor communities maintained a comparatively low diversity until the end of the Early Triassic, approximately 4 million years after the extinction event. Epifaunal benthos took longer to recover than infaunal benthos. This slow recovery stands in remarkable contrast with

49284-435: Was very low in diversity and exhibited no provincialism whatsoever. Brachiopods began their recovery around 250.1 ± 0.3 Ma, as marked by the appearance of the genus Meishanorhynchia , believed to be the first of the progenitor brachiopods that evolved after the mass extinction. Major brachiopod rediversification only began in the late Spathian and Anisian in conjunction with the decline of widespread anoxia and extreme heat and

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