The Early Triassic is the first of three
epochs of the
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
Period of the
geologic timescale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geoch ...
. It spans the time between
Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic
Series, which is a unit in
chronostratigraphy
Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time.
The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geologica ...
.
The Early Triassic is the oldest epoch of the
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...
Era. It is preceded by the
Lopingian Epoch (late Permian,
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ' ...
Era) and followed by the
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma ...
Epoch. The Early Triassic is divided into the
Induan and
Olenekian ages. The Induan is subdivided into the
Griesbachian and
Dienerian subages and the Olenekian is subdivided into the
Smithian and
Spathian
In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divid ...
subages.
The Lower Triassic series is coeval with the Scythian Stage, which is today not included in the official timescales but can be found in older literature. In Europe, most of the Lower Triassic is composed of
Buntsandstein, a
lithostratigraphic
Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology.
In general, strata are primarily igneous ...
unit of continental
red beds.
The Early Triassic and partly also the
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma ...
span the interval of biotic recovery from the
Permian-Triassic extinction event, the most severe
mass extinction
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. I ...
event in Earth's history.
A second extinction event, the
Smithian-Spathian boundary event
In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divided ...
, occurred during the Olenekian. A third extinction event occurred at the Olenekian-Anisian boundary, marking the end of the Early Triassic epoch.
Early Triassic climate
The climate during the Early Triassic Epoch (especially in the interior of the supercontinent
Pangaea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 millio ...
) was generally arid, rainless and dry and deserts were widespread; however the poles possessed a
temperate climate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...
. The pole-to-equator
temperature gradient was temporally flat during the Early Triassic and may have allowed tropical species to extend their distribution poleward. This is evidenced by the global distribution of
ammonoids.
The mostly hot climate of the Early Triassic may have been caused by late volcanic eruptions of the
Siberian Traps,
which had probably triggered the
Permian-Triassic extinction event and accelerated the rate of
global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate variability and change, Climate change in a broader sense also includes ...
into the Triassic.
Studies suggest that Early Triassic climate was very volatile, punctuated by a number of relatively rapid global temperature changes, marine anoxic events, and carbon cycle disturbances,
which led to subsequent extinction events in the aftermath of the
Permian-Triassic extinction event.
On the other hand, an alternative hypothesis proposes these Early Triassic climatic perturbations and biotic upheavals that inhibited the recovery of life following the P-T mass extinction to have been linked to forcing driven by changes in the Earth's obliquity defined by a roughly 32.8 thousand year periodicity with strong 1.2 million year modulations. According to proponents of this hypothesis, radiometric dating indicates that major activity from the Siberian Traps ended very shortly after the end-Permian extinction and did not span the entire Early Triassic epoch, thus not being the primary culprit for the climatic changes throughout this epoch.
Early Triassic life
Fauna and flora
The Triassic Period opened with the
Permian-Triassic extinction event. The massive extinctions that ended the
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...
Period and Paleozoic Era caused extreme hardships for the surviving species.
The Early Triassic Epoch saw the recovery of life after the biggest mass extinction event of the past, which took millions of years due to the severity of the event and the harsh Early Triassic climate. Many types of
coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secre ...
s,
brachiopod
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...
s,
molluscs,
echinoderm
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...
s, and other
invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s had disappeared. The Permian vegetation dominated by ''
Glossopteris'' in the southern hemisphere ceased to exist.
Other groups, such as
Actinopterygii, appear to have been less affected by this extinction event and body size was not a selective factor during the extinction event.
Different patterns of recovery are evident on land and in the sea. Early Triassic faunas lacked biodiversity and were relatively homogeneous due to the effects of the extinction. The ecological recovery on land took 30 million years.
Terrestrial biota
The most common land vertebrate was the small
herbivorous
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
synapsid
Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes rep ...
''
Lystrosaurus''. Often interpreted as a
disaster taxon (although this view was questioned), ''Lystrosaurus'' had a wide range across Pangea. In the southern part of the supercontinent, it co-occurred with the non-mammalian
cynodonts ''
Galesaurus'' and ''
Thrinaxodon'', early relatives of
mammals. First
archosauriforms appeared, such as ''
Erythrosuchus'' (
Olenekian-
Ladinian). This group includes the ancestors of
crocodile
Crocodiles (family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to include all extant ...
s and
dinosaurs
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
(including
birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
). Fossilized foot prints of
dinosauromorph
Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lage ...
s are known from the Olenekian.
The
flora
Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...
was
gymnosperm
The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...
-dominated at the onset of the Triassic, but changed rapidly and became
lycopod-dominated (e.g. ''
Pleuromeia
''Pleuromeia'' is an extinct genus of lycophytes. They are related to modern quillworts (''Isoetes''). ''Pleuromeia'' dominated vegetation during the Early Triassic all over Eurasia and elsewhere, in the aftermath of the collapse of floral comm ...
'') during the Griesbachian-Dienerian
ecological crisis. This change coincided with the extinction of the Permian ''
Glossopteris'' flora.
In the
Spathian
In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divid ...
subage, the flora changed back to gymnosperm and
pteridophyte dominated. These shifts reflect global changes in
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hai ...
and temperature.
Floral diversity was overall very low during the Early Triassic, as plant life had yet to fully recover from the Permian-Triassic extinction.
Microbially induced sedimentary structures (MISS) are common in the fossil record of North China in the immediate aftermath of the Permian-Triassic extinction, indicating that microbial mats dominated local terrestrial ecosystems following the Permian-Triassic boundary. The regional prevalence of MISS is attributable to a decrease in bioturbation and grazing pressure as a result of aridification and temperature increase. The disappearance of MISS later in the Early Triassic has been interpreted as a signal of increased bioturbation and recovery of terrestrial ecosystems.
Aquatic biota
In the oceans, the most common Early Triassic hard-shelled marine invertebrates were
bivalves,
gastropods
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. ...
,
ammonite
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttle ...
s,
echinoids, and a few articulate
brachiopod
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, ...
s.
Conodonts experienced a revival in diversity following a nadir during the Permian.
The first
oyster
Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not a ...
s appeared in the Early Triassic. They grew on the shells of living ammonoids as epizoans.
Microbial reefs were common, possibly due to lack of competition with
metazoan
Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...
reef
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic component, abiotic processes—deposition (geology), deposition of ...
builders as a result of the extinction. However, transient metazoan reefs reoccurred during the Olenekian wherever permitted by environmental conditions.
Ammonoids show blooms followed by extinctions during the Early Triassic.
Aquatic vertebrates diversified after the extinction.
Fishes: Typical Triassic
ray-finned fishes, such as ''
Australosomus
''Australosomus'' is an extinct genus of prehistoric ray-finned fish that lived during the Early Triassic epoch.
The interlocking scales (3 to 4 times long as wide), deeply forked caudal fin all help to distinguish this genus, which is known f ...
'', ''
Birgeria'', ''
Bobasatrania'', ''
Boreosomus
''Boreosomus'' (meaning: "boreal body") is an extinct genus of Triassic ray-finned fish. It was first described from the Arctic island of Spitsbergen (Svalbard, Norway), but was later also discovered in other parts of the world. ''Boreosomus'' be ...
'', ''
Pteronisculus'',
Parasemionotidae
Parasemionotiformes is an extinct order of neopterygian ray-finned fish that existed globally during the Triassic period. It comprises the families Parasemionotidae and Promecosominidae. Many of the included genera are monotypic and most specie ...
and ''
Saurichthys'' appeared close to the Permian-Triassic boundary, whereas
neopterygians diversified later during the Triassic.
Many species of fish had a global distribution during the Early Triassic.
Coelacanths show a peak in their diversity and new modes of life (''
Rebellatrix'').
Chondrichthyes
Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissu ...
are represented by
Hybodontiformes like ''
Palaeobates'', ''
Omanoselache'', ''
Lissodus
''Lissodus'' is an extinct genus of freshwater shark. It lived from the Early Carboniferous stage
Early may refer to:
History
* The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.:
** Early ...
'', some
Neoselachii, as well as last survivors of
Eugeneodontida
The Eugeneodontida is an extinct and poorly known order of Chondrichthyes, cartilaginous fishes. They possessed "tooth-whorls" on the symphysis of either the lower or both jaws and pectoral fins supported by long radials. They probably lacked pel ...
(''
Caseodus'', ''
Fadenia
''Fadenia'' is an extinct genus of eugeneodontid holocephalian chondrichthyan from the Carboniferous Period of Missouri (United States), the Permian period of Greenland, and the Early Triassic epoch of Greenland and Sulphur Mountain Formation o ...
'').
Amphibians: Relatively large, marine
temnospondyl amphibians
Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arb ...
, such as ''
Aphaneramma'' or ''
Wantzosaurus'', were geographically widespread during the
Induan and
Olenekian ages. The fossils of these crocodile-shaped amphibians were found in
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is ...
,
Spitsbergen
Spitsbergen (; formerly known as West Spitsbergen; Norwegian: ''Vest Spitsbergen'' or ''Vestspitsbergen'' , also sometimes spelled Spitzbergen) is the largest and the only permanently populated island of the Svalbard archipelago in northern N ...
,
Pakistan
Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
and
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
.
Reptiles: In the oceans, first marine reptiles appeared during the Early Triassic.
Their descendants ruled the oceans during the Mesozoic.
Hupehsuchia,
Ichthyopterygia and
sauropterygians
Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria became ...
are among the first marine reptiles to enter the scene in the Olenekian (e.g. ''
Cartorhynchus'', ''
Chaohusaurus'', ''
Utatsusaurus'', ''
Hupehsuchus'', ''
Grippia'', ''
Omphalosaurus
''Omphalosaurus'' (from the Greek root "Button Lizard", for their button-like teeth) is an extinct genus of marine reptile from the Early Triassic to Middle Triassic, thought to be in the order of Ichthyosauria. Most of what is known about ''O ...
'', ''
Corosaurus''). Other marine reptiles such as ''
Tanystropheus'', ''
Helveticosaurus'', ''
Atopodentatus'',
placodonts or the
thalattosaurs followed later in the Middle Triassic.
The
Anisian aged
ichthyosaur ''
Thalattoarchon'' was one of the first marine macropredators capable of eating prey that was similar in size to itself, an ecological role that can be compared to that of modern orcas.
Fossil gallery
File:PMS - spodnjetriasni kačjerepi (Ophiuroidea).jpg, Early Triassic brittle star
Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locom ...
s (echinoderms)
File:Claraia Clarai Museum Gröden.jpg, Fossils of the bivalve
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...
'' Claraia clarai''
File:Hedenstroemiidae_-_Hedenstroemia_tscherskii.JPG, Early Triassic ammonoid ''Hedenstroemia
''Hedenstroemia'' is an extinct genus of Early Triassic (Olenekian) cephalopods in the ammonoid order Ceratitida. They were nektonic carnivores.
Species
Distribution
Fossils of species within this family have been found in the Early Triassic o ...
''
File:Candelarialepis argentus.png, Fossil of the Early Triassic neopterygian '' Candelarialepis argentus''
File:HupehsuchusNanchangensis-PaleozoologicalMuseumOfChina-May23-08.jpg, Early Triassic '' Hupehsuchus'' fossil in the Paleozoological Museum of China
File:Erythrosuchus africanus 34.jpg, Skull of the Early Triassic archosauriform
Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian (roughly 252 million years ago). It was defined by Jacques Gauthier ...
'' Erythrosuchus''
File:Lystrosaurus hedini.JPG, '' Lystrosaurus hedini'' skeleton at the Museum of Paleontology in Tübingen
See also
*
Geologic time scale
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geoch ...
*
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
*
Mass extinction
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. I ...
References
Further reading
*
External links
GeoWhen Database - Early Triassic
{{Geological history, p, m
*01
Geological epochs
*01
de:Buntsandstein