Induan
Encyclopedia
The Induan is, in the geologic timescale, the first age of the Early Triassic
epoch
or the lowest stage of the Lower Triassic series
. It spans the time between 251 ± 0.4 Ma and 249.7 ± 0.7 Ma (million years ago). It is preceded by the Changhsingian
and is followed by the Olenekian
.
The Induan is roughly coeval with the regional Feixianguanian stage of China
.
The base of the Induan stage (which is also the base of the Lower Triassic series, the base of the Triassic system and the base of the Mesozoic
erathem
) is defined as the place in the fossil record where the conodont
species Hindeodus parvus first appears, or at the end of the negative δ18O anomaly after the big extinction event at the Permian-Triassic boundary. The global reference profile of the base of the Induan is situated in Changxing County
, China.
The top of the Induan stage (the base of the Olenekian) is at the first appearance of ammonite species Meekoceras gracilitatis.
Though the Induan is an unusually short age at this point in the geologic timescale, it still contains five ammonite biozone
s in the boreal domain and four ammonite biozones in the Tethyan domain
.
at the end of the Permian
period. Both global biodiversity
and community
-level (alpha) diversity
remained low through much of this stage of the Triassic. Much of the world remained almost lifeless, deserted, hot, and dry. The lystrosaurids (below) and the proterosuchids (below) were the only groups of land animals to dominate during the Induan stage. Other animals, such as the ammonite
s, fishes, insects, and the tetrapods (cynodont
s, amphibian
s, reptile
s, etc.) remained rare and terrestrial ecosystems did not recover for 30M years. Both the seas and much of the freshwater during the Induan were anoxic
.
.; 1956: Расчленение нижнего отдела триасовой системы на ярусы (Subdivision of the lower series of the Triassic System into stages), Doklady Akademii Nauk SSSR 109(4), pp 842–845 .
Early Triassic
The Early Triassic is the first of three epochs of the Triassic period of the geologic timescale. It spans the time between 251 ± 0.4 Ma and 245 ± 1.5 Ma . Rocks from this epoch are collectively known as the Lower Triassic, which is a unit in chronostratigraphy...
epoch
Epoch (geology)
An 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...
or the lowest stage of the Lower Triassic series
Series (stratigraphy)
Series are subdivisions of rock layers made based on the age of the rock and corresponding to the dating system unit called an epoch, both being formally defined international conventions of the geological timescale. A series is therefore a sequence of rock depositions defining a...
. It spans the time between 251 ± 0.4 Ma and 249.7 ± 0.7 Ma (million years ago). It is preceded by the Changhsingian
Changhsingian
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...
and is followed by the Olenekian
Olenekian
In the geologic timescale, the Olenekian is an age in the Early Triassic epoch or a stage in the Lower Triassic series. It spans the time between 249.7 ± 0.7 Ma and 245 ± 0.7 Ma . The Olenekian follows the Induan and is followed by the Anisian.The Olenekian saw the deposition of a large part of the...
.
The Induan is roughly coeval with the regional Feixianguanian stage of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
.
Stratigraphic definitions
The Induan stage was introduced into scientific literature by Russian stratigraphers in 1956, who divided the Skythian stage that was used by Western stratigraphers into the Induan and Olenekian stages. The Russian subdivision of the Lower Triassic then slowly replaced the one used in the West.The base of the Induan stage (which is also the base of the Lower Triassic series, the base of the Triassic system and the base of the Mesozoic
Mesozoic
The 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...
erathem
Erathem
In stratigraphy, paleontology, geology, and geobiology an erathem is the total stratigraphic record deposited during a certain corresponding span of time, an era in the geologic timescale....
) is defined as the place in the fossil record where the conodont
Conodont
Conodonts are extinct chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils now called conodont elements, found in isolation. Knowledge about soft tissues remains relatively sparse to this day...
species Hindeodus parvus first appears, or at the end of the negative δ18O anomaly after the big extinction event at the Permian-Triassic boundary. The global reference profile of the base of the Induan is situated in Changxing County
Changxing County
Changxing County is a county in the prefecture-level city of Huzhou, Zhejiang, China. Situated in the northern part of Zhejiang Province, it is close to the border of Zhejiang, Jiangsu, Anhui Province and serves as an important city in transportation.Changxing has since 2004 a Twin City ...
, China.
The top of the Induan stage (the base of the Olenekian) is at the first appearance of ammonite species Meekoceras gracilitatis.
Though the Induan is an unusually short age at this point in the geologic timescale, it still contains five ammonite biozone
Biozone
Biostratigraphic units or Biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxa....
s in the boreal domain and four ammonite biozones in the Tethyan domain
Tethys Ocean
The 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:...
.
Palaeontology
The Induan age followed the mass extinction eventPermian-Triassic extinction event
The 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...
at the end of the Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
period. Both global biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
and community
Community (ecology)
In ecology, a community is an assemblage of two or more populations of different species occupying the same geographical area. The term community has a variety of uses...
-level (alpha) diversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
remained low through much of this stage of the Triassic. Much of the world remained almost lifeless, deserted, hot, and dry. The lystrosaurids (below) and the proterosuchids (below) were the only groups of land animals to dominate during the Induan stage. Other animals, such as the ammonite
Ammonite
Ammonite, 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...
s, fishes, insects, and the tetrapods (cynodont
Cynodont
Cynodontia 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, amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s, reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
s, etc.) remained rare and terrestrial ecosystems did not recover for 30M years. Both the seas and much of the freshwater during the Induan were anoxic
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...
.
- lystrosauridsLystrosaurusLystrosaurus was a genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, and South Africa...
- proterosuchidsProterosuchidaeProterosuchidae is an early, possibly paraphyletic, assemblage of basal archosauriformes whose fossils are known from the Latest Permian of Russia and the Early Triassic of southern Africa, Russia, China, Australia, and Antarctica...
Archosaurs
Archosaurs of the Induan | ||||
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Taxa | Presence | Location | Description | Images |
|
South Africa | The largest land reptile during the Early Triassic period, equivalent in size to today's Komodo Dragons. It looked somewhat similar to a primitive crocodile, and shared many of their modern features like long jaws, powerful neck muscles, short legs and a lengthy tail, while retaining several of its own unique features such as its long legs, and hooked shaped mouth. |
|
|
|
South Africa, Fremouw Formation Fremouw Formation The Fremouw Formation is a Triassic-age rock formation in the Transantarctic Mountains of Antarctica. Fossils of prehistoric reptiles and amphibians have been found in the formation. Fossilized trees have also been found. The formation's beds were deposited along the banks of rivers and on... , Antarctica |
†Conodonts
†Conodonts of the Induan | ||||
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Taxa | Presence | Location | Description | Images |
|
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Procolophonomorphs
Procolophonomorpha Procolophonomorpha Procolophonomorpha is an order or clade of early reptiles that appeared during the Middle Permian. It constitutes a diverse assemblage that includes a number of lizard-like forms, as well as more diverse types like the pareiasaurs. The most important subclade, Procolophonia, is traditionally... of the Induan |
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Taxa | Presence | Location | Description | Images |
|
Late Permian to Late Triassic Late Triassic The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age... |
South Africa | A genus of lizard-shaped reptiles |
|
|
Induan/Olenekian Olenekian In the geologic timescale, the Olenekian is an age in the Early Triassic epoch or a stage in the Lower Triassic series. It spans the time between 249.7 ± 0.7 Ma and 245 ± 0.7 Ma . The Olenekian follows the Induan and is followed by the Anisian.The Olenekian saw the deposition of a large part of the... |
Mezen River Mezen River The Mezen is a river in Udorsky District of the Komi Republic and in Leshukonsky and Mezensky Districts of Arkhangelsk Oblast in Russia. Its mouth is located in the Mezen Bay of the White Sea. Mezen is one of the biggest rivers of European Russia. It is long, and the area of its basin... , European Russia |
A lizard-like looking reptile which diet consisted of aquatic plants. Adults discovered averaged 36 cm in length with a 4.4 cm skull | |
†Temnospondyls
†Temnospondyli Temnospondyli Temnospondyli 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... of the Induan |
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Taxa | Presence | Location | Description | Images |
|
Northern Russia | |||
†Therapsids (non-mammalian)
†Non-mammalian Paraphyly A group of taxa is said to be paraphyletic if the group consists of all the descendants of a hypothetical closest common ancestor minus one or more monophyletic groups of descendants... Therapsids of the Induan |
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Taxa | Presence | Location | Description | Images |
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|
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|
Late Permian to Early Triassic Early Triassic The Early Triassic is the first of three epochs of the Triassic period of the geologic timescale. It spans the time between 251 ± 0.4 Ma and 245 ± 1.5 Ma . Rocks from this epoch are collectively known as the Lower Triassic, which is a unit in chronostratigraphy... |
Antarctica, India and South Africa | The most common group of terrestrial vertebrates during the Early Triassic: for a while 95% of land vertebrates were Lystrosaurus | |
Scaloposaurus Scaloposaurus is an extinct carnivorous genus of therocephalian living during the Triassic 251.0—245.0 Ma existing for approximately .-Taxonomy:... |
A therocephalian | |||
Thrinaxodon Thrinaxodon was a cynodont, an ermine-sized therapsid. Pits on the skull suggest that Thrinaxodon may have had whiskers, and by extension a protective covering of fur. There are suggestions that it was warm-blooded... |
? | South Africa, Antarctica | A cat-sized cynodont. Many scientists suggest that the pits on the skull indicate that Thrinaxodon had whiskers and, therefore, probably had a covering of fur. There are suggestions that it was warm-blooded. Even so, it still had a reptilian skeleton and laid eggs. | |
Literature
; 2005: The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale, Episodes 28(4), pp. 233–244.; 2004: A Geologic Time Scale 2004, Cambridge University PressCambridge University Press
Cambridge University Press is the publishing business of the University of Cambridge. Granted letters patent by Henry VIII in 1534, it is the world's oldest publishing house, and the second largest university press in the world...
.; 1956: Расчленение нижнего отдела триасовой системы на ярусы (Subdivision of the lower series of the Triassic System into stages), Doklady Akademii Nauk SSSR 109(4), pp 842–845 .
External links
- GeoWhen Database - Induan
- Lower Triassic timescale at the website of the subcommission for stratigraphic information of the ICS
- Lower Triassic timescale at the website of Norges Network of offshore records of geology and stratigraphy.
- The Induan at palaeos.com