The
Permian
>The term "Permian" was introduced into
geologyGeology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
in 1841 by Sir
Sir R. I. MurchisonSir Roderick Impey Murchison, 1st Baronet KCB DCL FRS FRSE FLS PRGS PBA MRIA was a Scottish geologist who first described and investigated the Silurian system.-Early life and work:...
, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with
Edouard de VerneuilPhillippe Edouard Poulletier de Verneuil was a French paleontologist.He was born in Paris and educated in law, but being of independent means he was free to follow his own inclinations, and having attended lectures on geology by Jean-Baptiste Elie de Beaumont he was so attracted to the subject...
; Murchison asserted in 1841 that he named his "Permian system" after the ancient kingdom of
PermiaGreat Perm or simply Perm, Latinized Permia, was a medieval Komi state in what is now the Perm Krai of the Russian Federation.Cherdyn is said to have been its capital....
, and not after the then small town of
PermPerm is a city and the administrative center of Perm Krai, Russia, located on the banks of the Kama River, in the European part of Russia near the Ural Mountains. From 1940 to 1957 it was named Molotov ....
, as usually assumed; see
"Origin of the Permian" is a geologic period and system which extends from 299.0 ± 0.8 to 251.0 ± 0.4 Mya (Million years ago). It was named after the
Perm KraiPerm Krai is a federal subject of Russia that came into existence on December 1, 2005 as a result of the 2004 referendum on the merger of Perm Oblast and Komi-Permyak Autonomous Okrug. The city of Perm became the administrative center of the new federal subject...
in
RussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
by Scottish geologist
Roderick MurchisonSir Roderick Impey Murchison, 1st Baronet KCB DCL FRS FRSE FLS PRGS PBA MRIA was a Scottish geologist who first described and investigated the Silurian system.-Early life and work:...
in 1841. The Permian follows the
CarboniferousThe Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
and precedes the
TriassicThe Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
, and is characterized among land vertebrates by the diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs and archosaurs. The world at the time was very hot and dry, and was dominated by a single
supercontinentIn geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
known as
PangaeaPangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
. The extensive
rainforestRainforests are forests characterized by high rainfall, with definitions based on a minimum normal annual rainfall of 1750-2000 mm...
s of the
CarboniferousThe Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
had disappeared, leaving behind vast swathes of
desertA desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
. The Permian period (along with the Paleozoic era) ended with the
largest mass extinction in Earth's historyThe Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras...
, in which nearly 90% of marine species and 70% of terrestrial species died out.
ICS Subdivisions
Official Subdivisions of the Permian System, from most recent to most ancient rock layers are:
Upper Permian (Late Permian) or Lopingian, Tatarian, or Zechstein,
epochAn epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
[260.4 ± 0.7 Mya - 251.0 ± 0.4 Mya]:
- Changhsingian (Changxingian)
In the geologic timescale, the Changhsingian or Changxingian is the latest age or uppermost stage of the Permian. It is also the upper or latest of two subdivisions of the Lopingian epoch or series. The Changhsingian lasted from 253.8 ± 0.7 to 251.0 ± 0.7 million years ago...
[253.8 ± 0.7 Mya - 251.0 ± 0.4 Mya]
- Wuchiapingian (Wujiapingian)
In the geologic timescale, the Wuchiapingian or Wujiapingian is an age or stage of the Permian. It is also the lower or earlier of two subdivisions of the Lopingian epoch or series. The Wuchiapingian spans the time between 260.4 ± 0.7 and 253.8 ± 0.7 million years ago...
[260.4 ± 0.7 Mya - 253.8 ± 0.7 Mya]
- Others:
- Waiitian (New Zealand) [260.4 ± 0.7 Mya - 253.8 ± 0.7 Mya]
- Makabewan (New Zealand) [253.8 - 251.0 ± 0.4 Mya]
- Ochoan (North American) [260.4 ± 0.7 Mya - 251.0 ± 0.4 Mya]
Middle Permian, or Guadalupian epoch [270.6 ± 0.7 - 260.4 ± 0.7 Mya]:
- Capitanian
In the geologic timescale, the Capitanian is an age or stage of the Permian. It is also the uppermost or latest of three subdivisions of the Guadalupian epoch or series. The Capitanian lasted between and...
stage [265.8 ± 0.7 - 260.4 ± 0.7 Mya]
- Wordian
In the geologic timescale, the Wordian is an age or stage of the Permian. It is the middle of three subdivisions of the Guadalupian epoch or series. The Wordian lasted between 268.0 ± 0.7 and 265.8 ± 0.7 million years ago...
stage [268.0 ± 0.7 - 265.8 ± 0.7 Mya]
- Roadian
In the geologic timescale, the Roadian is an age or stage of the Permian. It is the earliest or lower of three subdivisions of the Guadalupian epoch or series. The Roadian lasted between 270.6 ± 0.7 and 268.0 ± 0.7 million years ago...
stage [270.6 ± 0.7 - 268.0 ± 0.7 Mya]
- Others:
- Kazanian or Maokovian (European) [270.6 ± 0.7 - 260.4 ± 0.7 Mya]
- Braxtonian stage (New Zealand) [270.6 ± 0.7 - 260.4 ± 0.7 Mya]
Lower / Early Permian or Cisuralian epoch [299.0 ± 0.8 - 270.6 ± 0.7 Mya]:
- Kungurian
In the geologic timescale, the Kungurian is an age or stage of the Permian. It is the latest or upper of four subdivisions of the Cisuralian epoch or series. The Kungurian lasted between 275.6 ± 0.7 and 270.6 ± 0.7 million years ago...
(Irenian / Filippovian / Leonard) stage [275.6 ± 0.7 - 270.6 ± 0.7 Mya]
- Artinskian
In the geologic timescale, the Artinskian is an age or stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Artinskian lasted between 284.4 ± 0.7 and 275.6 ± 0.7 million years ago...
(Baigendzinian / Aktastinian) stage [284.4 ± 0.7 - 275.6 ± 0.7 Mya]
- Sakmarian
In the geologic timescale, the Sakmarian is an age or stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Sakmarian lasted between 294.6 ± 0.8 and 284.4 ± 0.7 million years ago...
(Sterlitamakian / Tastubian / Leonard / Wolfcamp) stage [294.6 ± 0.8 - 284.4 ± 0.7 Mya]
- Asselian
In the geologic timescale, the Asselian is the earliest geochronologic age or lowermost chronostratigraphic stage of the Permian. It is a subdivision of the Cisuralian epoch or series. The Asselian lasted between 299.0 ± 0.8 and 294.6 ± 0.8 million years ago...
(Krumaian / Uskalikian / Surenian / Wolfcamp) stage [299.0 ± 0.8 - 294.6 ± 0.8 Mya]
- Others:
- Telfordian (New Zealand) [289 - 278]
- Mangapirian (New Zealand) [278 - 270.6]
Oceans
Sea levelMean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
s in the Permian remained generally low, and near-shore environments were limited by the collection of almost all major
landmassA landmass is a contiguous area of land surrounded by ocean. Although it may be most often written as one word to distinguish it from the usage "land mass"—the measure of land area—it is also used as two words.Landmasses include:*supercontinents...
es into a single continent --
PangaeaPangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
. This could have in part caused the widespread extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms.
Paleogeography
During the Permian, all the
EarthEarth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
's major land masses were collected into a single supercontinent known as
PangaeaPangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
. Pangaea straddled the
equatorAn equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean ("
PanthalassaPanthalassa , also known as the Panthalassic Ocean, was the vast global ocean that surrounded the supercontinent Pangaea, during the late Paleozoic and the early Mesozoic years. It included the Pacific Ocean to the west and north and the Tethys Ocean to the southeast...
", the "universal sea"), and the Paleo-Tethys Ocean, a large ocean that was between Asia and Gondwana. The Cimmeria continent
riftIn geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....
ed away from
GondwanaIn paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
and drifted north to
LaurasiaIn paleogeography, Laurasia was the northernmost of two supercontinents that formed part of the Pangaea supercontinent from approximately...
, causing the Paleo-Tethys to shrink. A new ocean was growing on its southern end, the
Tethys OceanThe Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...
, an ocean that would dominate much of the
MesozoicThe Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
Era. Large continental landmasses create climates with extreme variations of heat and cold ("
continental climateContinental climate is a climate characterized by important annual variation in temperature due to the lack of significant bodies of water nearby...
") and
monsoonMonsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
conditions with highly seasonal rainfall patterns.
DesertA desert is a landscape or region that receives an extremely low amount of precipitation, less than enough to support growth of most plants. Most deserts have an average annual precipitation of less than...
s seem to have been widespread on Pangaea. Such dry conditions favored
gymnospermThe gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...
s, plants with seeds enclosed in a protective cover, over plants such as
fernA fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...
s that disperse
sporeIn biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s. The first modern trees (
conifersThe conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...
,
ginkgoGinkgo , also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives...
s and
cycadCycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
s) appeared in the Permian.
Three general areas are especially noted for their extensive Permian deposits - the
Ural MountainsThe Ural Mountains , or simply the Urals, are a mountain range that runs approximately from north to south through western Russia, from the coast of the Arctic Ocean to the Ural River and northwestern Kazakhstan. Their eastern side is usually considered the natural boundary between Europe and Asia...
(where Perm itself is located), China, and the southwest of North America, where the Permian Basin in the
U.S.The United States of America is a federal constitutional republic comprising fifty states and a federal district...
state of
TexasTexas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
is so named because it has one of the thickest deposits of Permian rocks in the world.
Climate
The
climateClimate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
in the Permian was quite varied. At the start of the Permian, the
EarthEarth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
was still at the grip of an
Ice AgeAn ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
from the
CarboniferousThe Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
. Glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles.
Life
Marine biota
Permian marine deposits are rich in
fossilFossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
mollusks,
echinodermEchinoderms are a phylum of marine animals. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone....
s, and
brachiopodBrachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...
s. Fossilized shells of two kinds of
invertebrateAn invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s are widely used to identify Permian strata and correlate them between sites:
fusulinidThe Fusulinida is an extinct order within the Foraminifera in which the tests are composed of tightly packed, secreted microgranular calcite. In advanced forms the test wall is differentiated into two or more layers...
s, a kind of shelled amoeba-like
protistProtists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...
that is one of the
foraminiferaThe Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
ns, and
ammonoidsAmmonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...
, shelled
cephalopodA cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s that are distant relatives of the modern
nautilusNautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus...
. By the close of the Permian,
trilobiteTrilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...
s and a host of other marine groups became extinct.
Terrestrial biota
Terrestrial life in the Permian included diverse plants, fungi,
arthropodAn arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s, and various types of
tetrapodsPermian Tetrapods were amphibians and reptiles that lived during the Permian Period.During this time, amphibians remained common, including various Temnospondyli and Lepospondyli...
. The period saw a massive desert covering the interior of the
PangaeaPangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
. The warm zone spread in the northern hemisphere, where extensive dry desert appeared. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals died out or became marginal elements.
The Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began. The swamp-loving lycopod trees of the Carboniferous, such as
LepidodendronLepidodendron is an extinct genus of primitive, vascular, arborescent plant related to the Lycopsids . It was part of the coal forest flora. They sometimes reached heights of over , and the trunks were often over in diameter, and thrived during the Carboniferous period...
and
SigillariaSigillaria is a genus of extinct, spore-bearing, arborescent plants which flourished in the Late Carboniferous period but dwindled to extinction in the early Permian period. It was a lycopodiophyte, and is related to the lycopsids, or club-mosses, but even more closely to quillworts, as was its...
, were progressively replaced in the continental interior by the more advanced seed ferns and early conifers. At the close of the Permian, lycopod and equicete
swampA swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
s reminiscent of Carboniferous flora was relegated to a series of equatorial islands in the Paleotethys Sea that later would become the
South ChinaSouth China continent, also known as South China craton, South Chinese craton, or Yangtze craton, was an ancient continent that contained today's South and Southeast China , Indochina, and parts of Southeast Asia...
.
The Permian saw the radiation of many important conifer groups, including the ancestors of many present-day families. Rich forests were present in many areas, with a diverse mix of plant groups. The southern continent saw extensive seed fern forests of the
GlossopterisGlossopteris is the largest and best-known genus of the extinct order of seed ferns known as Glossopteridales ....
flora. Oxygen levels were probably high there. The
ginkgoGinkgo , also spelled gingko and known as the Maidenhair Tree, is a unique species of tree with no close living relatives...
s and
cycadCycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
s also appeared during this period.
Insects of the Permian
By the
PennsylvanianThe Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...
and well into the Permian, by far the most successful were primitive
relatives of cockroachesBlattoptera , or proto-cockroaches, is a name given to various "roachid" fossil insects related to cockroaches, mantises and termites, and of general cockroach-like appearance and possibly habit. The group is on the rank of an order, though being paraphyletic is most often given without formal...
. Six fast legs, four well developed folding wings, fairly good eyes, long, well developed antennae (olfactory), an omnivorous digestive system, a receptacle for storing sperm, a
chitinChitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
-based
exoskeletonAn exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
that could support and protect, as well as form of gizzard and efficient mouth parts, gave it formidable advantages over other herbivorous animals. About 90% of insects at the start of the Permian were cockroach-like insects ("Blattopterans").
Primitive forms of dragonflies (
OdonataOdonata is an order of insects, encompassing dragonflies and damselflies . The word dragonfly is also sometimes used to refer to all Odonata, but the back-formation odonate is a more correct English name for the group as a whole...
) were the dominant aerial predators and probably dominated terrestrial insect predation as well. True Odonata appeared in the Permian and all are effectively
amphibiousAmphibious means able to use either land or water. In particular it may refer to:*Amphibious warfare, warfare carried out on both land and water*Amphibians, vertebrate animals of the Class Amphibia...
(aquatic immature stages, and terrestrial adults), as are all modern odonates. Their prototypes are the oldest winged fossils, go back to the
DevonianThe Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
, and are different in several respects from the wings of other insects. Fossils suggest they may have possessed many modern attributes even by the late
CarboniferousThe Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
, and it is possible that they captured small vertebrates, for some species had a wing span of 71 cm. Several other insect groups appeared during the Permian, including the Coleoptera (beetles) and
HemipteraHemiptera is an order of insects most often known as the true bugs , comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others...
(true bugs).
Synapsid and amphibian fauna
Early Permian terrestrial faunas were dominated by pelycosaurs and amphibians, the middle Permian by primitive therapsids such as the
dinocephaliaDinocephalia are a clade of large early therapsids that flourished during the Middle Permian, but became extinct leaving no descendants.-Description:...
, and the late Permian by more advanced therapsids such as
gorgonopsiaGorgonopsia is a suborder of therapsid synapsids. Their name is a reference to the Gorgons of Greek mythology. Like other therapsids, gorgonopsians were at one time called "mammal-like reptiles"...
ns and
dicynodontDicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'...
s. Towards the very end of the Permian the first
archosaursArchosauriformes is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Late Permian...
appeared, a group that would give rise to the
dinosaurDinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s in the
following periodThe Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
. Also appearing at the end of the Permian were the first
cynodontCynodontia or cynodonts are a taxon of therapsids which first appeared in the Late Permian and were eventually distributed throughout all seven continents by the Early Triassic . This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of...
s, which would go on to evolve into
mammalMammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s during the Triassic. Another group of therapsids, the
therocephaliaTherocephalians are an extinct suborder of carnivorous eutheriodont therapsids that lived from the middle and late Permian into the Triassic 265.0—245.0 Ma existing for approximately ....
ns (such as
TrochosaurusTrochosaurus is an extinct genus of mammal-like reptile. It belong to a synapsid suborder called Therocephalia. Like them, and the mammals, it had a secondary palate....
), arose in the Middle Permian. There were no aerial vertebrates.
The Permian period saw the development of a fully terrestrial fauna and the appearance of the first
largeIn terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...
herbivoreHerbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s and
carnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s. It was the high tide of the
anapsidAn anapsid is an amniote whose skull does not have openings near the temples.While "anapsid reptiles" or "anapsida" are traditionally spoken of as if they were a monophyletic group, it has been suggested that several groups of reptiles that had anapsid skulls may be only distantly related...
es in the form of the massive
PareiasaurThe Pareiasaurs - Family Pareiasauridae - are a clade of medium-sized to large herbivorous anapsid reptiles that flourished during the Permian period....
s and host of smaller, generally lizard-like groups. A group of small reptiles, the diapsids started to abound. These were the ancestors to most modern reptiles and the ruling dinosaurs as well as pterosaurs and crocodiles.
Thriving also, were the early ancestors to mammals, the
synapsidSynapsids are a group of animals that includes mammals and everything more closely related to mammals than to other living amniotes. They are easily separated from other amniotes by having an opening low in the skull roof behind each eye, leaving a bony arch beneath each, accounting for their name...
a, which included some large reptiles such as
DimetrodonDimetrodon was a predatory synapsid genus that flourished during the Permian period, living between 280–265 million years ago ....
. Reptiles grew to dominance among vertebrates, because their special adaptations enabled them to flourish in the drier climate.
Permian amphibians consisted of
temnospondyliTemnospondyli is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent...
,
lepospondyliLepospondyli are a group of small but diverse Carboniferous to early Permian tetrapods. Six different groups are known, the Acherontiscidae, Adelospondyli, Aïstopoda, Lysorophia, Microsauria and Nectridea, and between them they include newt-like, eel- or snake-like, and lizard-like forms, along...
and
batrachosaursBatrachosauria is a name given either to very reptile-like amphibians dating from the Carboniferous and Permian periods, or to amniotes and those amphibians very closely related to them...
.
Permian–Triassic extinction event
The Permian ended with the most extensive
extinction eventAn extinction event is a sharp decrease in the diversity and abundance of macroscopic life. They occur when the rate of extinction increases with respect to the rate of speciation...
recorded in
paleontologyPaleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
: the
Permian-Triassic extinction eventThe Permian–Triassic extinction event, informally known as the Great Dying, was an extinction event that occurred 252.28 Ma ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras...
. 90% to 95% of marine species became
extinctIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
, as well as 70% of all land organisms. It is also the only known mass extinction of insects. Recovery from the Permian-Triassic extinction event was protracted; on land ecosystems took 30M years to recover.
There is also significant evidence that massive
flood basaltA flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales in prehistory, creating great plateaus and mountain ranges...
eruptions from magma output lasting thousands of years in what is now the
Siberian TrapsThe Siberian Traps form a large region of volcanic rock, known as a large igneous province, in the Russian region of Siberia. The massive eruptive event which formed the traps, one of the largest known volcanic events of the last 500 million years of Earth's geological history, continued for...
contributed to environmental stress leading to mass extinction. The reduced coastal habitat and highly increased aridity probably also contributed. Based on the amount of lava estimated to have been produced during this period, the worst-case scenario is an expulsion of enough carbon dioxide from the eruptions to raise world temperatures five degrees Celsius.
Another hypothesis involves ocean venting of
hydrogen sulfideHydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
gas. Portions of deep ocean will periodically lose all of their dissolved oxygen allowing bacteria that live without oxygen to flourish and produce hydrogen sulfide gas. If enough hydrogen sulfide accumulates in an
anoxic zoneOceanic anoxic events or anoxic events occur when the Earth's oceans become completely depleted of oxygen below the surface levels. Although anoxic events have not happened for millions of years, the geological record shows that they happened many times in the past. Anoxic events may have caused...
, the gas can rise into the atmosphere.
Oxidizing gases in the atmosphere would destroy the toxic gas, but the hydrogen sulfide would soon consume all of the atmospheric gas available to change it. Hydrogen sulfide levels would increase dramatically over a few hundred years.
Modeling of such an event indicates that the gas would destroy
ozoneOzone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
in the upper atmosphere allowing
ultravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation to kill off species that had survived the toxic gas. Of course, there are species that can metabolize hydrogen sulfide.
Another hypothesis builds on the flood basalt eruption theory. Five degrees Celsius would not be enough increase in world temperatures to explain the death of 95% of life. But such warming could slowly raise ocean temperatures until frozen methane reservoirs below the ocean floor near coastlines (a current target for a new energy source) melted, expelling enough methane, among the most potent greenhouse gases, into the atmosphere to raise world temperatures an additional five degrees Celsius. The frozen methane hypothesis helps explain the increase in carbon-12 levels midway into the Permian-Triassic boundary layer. It also helps explain why the first phase of the layer's extinctions was land-based, the second was marine-based (and starting right after the increase in C-12 levels), and the third land-based again.
An even more speculative hypothesis is that intense radiation from a nearby
supernovaA supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
was responsible for the extinctions.
TrilobiteTrilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...
s, which had thrived since
CambrianThe Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
times, finally became extinct before the end of the Permian.
NautilusNautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus...
es, a species of cephalopods, surprisingly survived this occurrence.
In 2006, a group of American scientists from The Ohio State University reported evidence for a possible huge
meteoriteA meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
craterIn the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
(
Wilkes Land craterWilkes Land crater is an informal term that may apply to two separate cases of conjectured giant impact craters hidden beneath the ice cap of Wilkes Land, East Antarctica...
) with a diameter of around 500 kilometers in
Antarctica. The crater is located at a depth of 1.6 kilometers beneath the ice of Wilkes Land in eastern Antarctica. The scientists speculate that this impact may have caused the Permian–Triassic extinction event, although its age is bracketed only between 100 million and 500 million years ago. They also speculate that it may have contributed in some way to the separation of
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
from the Antarctic landmass, which were both part of a supercontinent called
GondwanaIn paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
. Levels of iridium and quartz fracturing in the Permian-Triassic layer do not approach those of the
Cretaceous-Tertiary boundary layerThe K–T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 Ma ago. K is the traditional abbreviation for the Cretaceous period, and T is the abbreviation for the Tertiary period...
. Given that a far greater proportion of species and individual organisms became extinct during the former, doubt is cast on the significance of a meteor impact in creating the latter. Further doubt has been cast on this theory based on fossils in Greenland showing the extinction to have been gradual, lasting about eighty thousand years, with three distinct phases.
Many scientists argue that the Permian-Triassic extinction event was caused by a combination of some or all of the hypotheses above and other factors; the formation of
PangaeaPangaea, Pangæa, or Pangea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration....
decreased the number of coastal habitats and may have contributed to the extinction of many clades.
See also
- List of fossil sites (with link directory)
- Olson's Extinction
Olson's Extinction was a mass extinction that occurred in the Early Guadalupian of the Permian period and which predated the Permian–Triassic extinction event.- Extinction Patterns :...
- Permian tetrapods
Permian Tetrapods were amphibians and reptiles that lived during the Permian Period.During this time, amphibians remained common, including various Temnospondyli and Lepospondyli...
External links