The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.902 Ma and 247.2 Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic, which is a unit in chronostratigraphy. The Early Triassic is the oldest epoch of the Mesozoic Era and is divided into the Induan and Olenekian ages.
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 unit of continental red beds.
|Subdivision of the Triassic system|
according to the ICS, as of 2018.
The Permian-Triassic extinction event spawned the Triassic period. The massive extinctions that ended the Permian period and Paleozoic era caused extreme hardships for the surviving species. Many types of corals, brachiopods, molluscs, echinoderms, and other invertebrates had completely disappeared. The most common Early Triassic hard-shelled marine invertebrates were bivalves, gastropods, ammonites, echinoids, and a few articulate brachiopods. The most common land vertebrate was the small herbivorous synapsid Lystrosaurus.
Early Triassic faunas lacked biodiversity and were relatively homogenous throughout the epoch due to the effects of the extinction, ecological recovery on land took 30M years. The climate during the Early Triassic epoch (especially in the interior of the supercontinent Pangaea) was generally arid, rainless and dry and deserts were widespread; however the poles possessed a temperate climate. The relatively hot climate of the Early Triassic may have been caused by widespread volcanic eruptions which accelerated the rate of global warming and possibly caused the Permian-Triassic extinction event.
Until recently the existence of an extinction event about 3 million years following the end-Permian extinctions was not recognised, possibly because there were few species left to go extinct. However, studies on conodonts have revealed that temperatures rose in the first 3 million years of the Triassic, ultimately reaching sea surface temperatures of 40 °C (104 °F) in the tropics around 249 million years ago. Large and mobile species disappeared from the tropics, and amongst the immobile species such as molluscs, only the ones that could cope with the heat survived; half the bivalves disappeared. On land, the tropics were practically devoid of life. Big, active animals only returned to the tropics, and plants recolonised on land when temperatures returned to normal around 247 million years ago.
The Batrachia are a clade of amphibians that includes frogs and salamanders, as well as the extinct allocaudates, but not caecilians. The name Batrachia was first used by French zoologist Pierre André Latreille in 1800 to refer to frogs, but has more recently been defined in a phylogenetic sense as a node-based taxon that includes the last common ancestor of frogs and salamanders and all of its descendants. The idea that frogs and salamanders are more closely related to each other than either is to caecilians is strongly supported by morphological and molecular evidence, they are for instance the only vertebrates able to raise and lower their eyes, but an alternative hypothesis exists in which salamanders and caecilians are each other's closest relatives as part of a clade called the Procera, with frogs positioned as the sister taxon of this group.Bystrowisuchus
Bystrowisuchus is an extinct genus of ctenosauriscid pseudosuchian archosaur from the Early Triassic of European Russia. Fossils have been found in the Olenekian-age Lipovskaya Formation in Ilovlinsky District. The type species is Bystrowisuchus flerovi.Czatkowiella
Czatkowiella is an extinct genus of long-necked archosauromorph known from Early Triassic (Olenekian age) rocks of Czatkowice 1, Poland. It was first named by Magdalena Borsuk−Białynicka and Susan E. Evans in 2009 and the type species is Czatkowiella harae.Eucynodontia
Eucynodontia ("true dog teeth") is a clade of cynodont therapsids including mammals and most non-mammalian cynodonts. The oldest eucynodonts are known from the Early Triassic and possibly Late Permian. Eucynodontia includes two major subgroups, Cynognathia and Probainognathia.The clade was named by Thomas Kemp in 1982.In 2001, James Allen Hopson e.a. defined the clade Euynodontia as the least inclusive group containing Mammalia and Exaeretodon.Euskelia
Euskelia is a clade of extinct Temnospondyl amphibians.Hueneosauria
The Hueneosauria are a group of Ichthyosauria, living during the Mesozoic.
In 2000, Michael Werner Maisch and Andreas Matzke defined a node clade Hueneosauria as the group consisting of the last common ancestor of Mixosaurus cornalianus and Ophthalmosaurus icenicus; and all of its descendants. The clade is named after Friedrich von Huene, a German paleontologist who was a leading ichthyosaur expert in the early twentieth century.The Hueneosauria contain the more derived ichthyosaurs, which have the morphology of a fish. The group originated in the early Triassic and became extinct during the Cretaceous.Ichthyopterygia
Ichthyopterygia ("fish flippers") was a designation introduced by Sir Richard Owen in 1840 to designate the Jurassic ichthyosaurs that were known at the time, but the term is now used more often for both true Ichthyosauria and their more primitive early and middle Triassic ancestors.Basal ichthyopterygians (prior to and ancestral to true Ichthyosauria) were mostly small (a meter or less in length) with elongated bodies and long, spool-shaped vertebrae, indicating that they swam in a sinuous, eel-like manner. This allowed for quick movements and maneuverability that were advantages in shallow-water hunting. Even at this early stage, they were already very specialised animals with proper flippers, and would have been incapable of movement on land.
These animals seem to have been widely distributed around the coast of the northern half of Pangea, as they are known the Late Olenekian and Early Anisian (early part of the Triassic period) of Japan, China, Canada, and Spitsbergen (Norway). By the later part of the Middle Triassic, they were extinct, having been replaced by their descendants, the true ichthyosaurs.Induan
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 251.902 Ma and 251.2 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.Koilamasuchus
Koilamasuchus is an extinct genus of Triassic archosauriform. Remains have been found from the Quebrada de los Fósiles Formation of the Puesto Viejo Group in Argentina. This locality is probably early to mid Triassic (Ladinian to Carnian) in age, although the exact age is debatable. Koilamasuchus is derived from the Latin word 'koilamas' (which means cavity or pocket) and the Greek 'suchus' (which means crocodile). This is in reference to the lateral fossae (pits) on the type specimen's vertebrae. The type species of Koilamasuchus, K. gonzalezdiazi, refers to Dr. Emilio F. Gonzalez Diaz, the paleontologist who discovered the holotype specimen. The fossil has been known since 1981 when it was first described by paleontologist José Bonaparte, but it was not described as a new genus and species until 2010.Lepidosauromorpha
Lepidosauromorpha is a group of reptiles comprising all diapsids closer to lizards than to archosaurs (which include crocodiles and birds). The only living sub-group is the Lepidosauria: extant lizards, snakes, amphisbaenians and tuataras.
Lepidosauromorpha are distinguishable from Archosauromorphs (archosaurs) by their primitive sprawling gait, which allows for the same sinusoidal trunk and tail movement seen in fish, the sliding "joint" between the coracoids and the sternum (for a longer stride), and their pleurodont dentition. In contrast, Archosauromorphs possess a parasagittal gait, a reduction in their dermal girdle, a reduction and/or loss of the sternum, and a more thecodont dentition.
Lepidosauromorpha have retained cold blood because of their low-energy sprawling stance.Lissamphibia
The Lissamphibia are a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relatives), and the Gymnophiona (the limbless caecilians and their extinct relatives). A fourth group, the Allocaudata, was moderately successful, spanning 160 million years from the Middle Jurassic to the Early Pliocene, but became extinct 2.5 million years ago.
For several decades, this name has been used for a group that includes all living amphibians, but excludes all the main groups of Paleozoic tetrapods, such as Temnospondyli, Lepospondyli, Embolomeri, and Seymouriamorpha. Some scientists have concluded that all of the primary groups of modern amphibians—frogs, salamanders and caecilians—are closely related.
Some writers have argued that the early Permian dissorophoid Gerobatrachus hottoni is a lissamphibian. If it is not, the earliest known lissamphibians are Triadobatrachus and Czatkobatrachus from the Early Triassic.Lystrosaurus
Lystrosaurus (; 'shovel lizard'; proper Greek is λίστρον lístron ‘tool for leveling or smoothing, shovel, spade, hoe’) was a herbivorous genus of Late Permian and Early Triassic Period dicynodont therapsids, which lived around 250 million years ago in what is now Antarctica, India, China, Mongolia, European Russia and South Africa. Four to six species are currently recognized, although from the 1930s to 1970s the number of species was thought to be much higher. They ranged in size from a small dog to 2.5 meters long.Being a dicynodont, Lystrosaurus had only two teeth (a pair of tusk-like canines), and is thought to have had a horny beak that was used for biting off pieces of vegetation. Lystrosaurus was a heavily built, herbivorous animal, approximately the size of a pig. The structure of its shoulders and hip joints suggests that Lystrosaurus moved with a semi-sprawling gait. The forelimbs were even more robust than the hindlimbs, and the animal is thought to have been a powerful digger that nested in burrows.
Lystrosaurus survived the Permian-Triassic extinction, 252 million years ago. In the Early Triassic, they were by far the most common terrestrial vertebrates, accounting for as many as 95% of the total individuals in some fossil beds. Researchers have forwarded various hypotheses for why Lystrosaurus survived the extinction event and prospered in the early Triassic.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 251.2 Ma and 247.2 Ma (million years ago). The Olenekian follows the Induan and is followed by the Anisian.The Olenekian saw the deposition of a large part of the Buntsandstein in Europe. Archosaurs - a group encompassing crocodiles, pterosaurs, dinosaurs, and ultimately birds - are diapsid reptiles that first evolved from Archosauriform ancestors during the Olenekian.
The Olenekian is roughly coeval with the regional Yongningzhenian stage used in China.Procolophoninae
Procolophoninae is an extinct subfamily of procolophonid parareptiles from the late Early Triassic to the early Middle Triassic (Olenekian and Anisian stages) of Africa, Antarctica, Asia, Europe and South America. Currently, the oldest-known procolophonine is Procolophon from the earliest Olenekian stage.Sauropterygia
Sauropterygia ("lizard flippers") is an extinct, diverse taxon of 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 extinct at the end of that era. The plesiosaurs would continue to diversify till the end of the Mesozoic. Sauropterygians are united by a radical adaptation of their pectoral girdle, adapted to support powerful flipper strokes. Some later sauropterygians, such as the pliosaurs, developed a similar mechanism in their pelvis.Thrinaxodontidae
Thrinaxodontidae is an extinct family of cynodonts that includes the genera Thrinaxodon, Nanictosaurus, Nanocynodon, and Novocynodon, and possibly Bolotridon and Platycraniellus. All thrinaxodontids share a bony secondary palate. Thrinaxodontids are basal members of the cynodont clade Epicynodontia. Some studies consider the family a paraphyletic group, representing an evolutionary grade of basal epicynodonts rather than an actual clade.Trematosauria
Trematosauria is one of two major groups of temnospondyl amphibians that survived the Permian-Triassic extinction event, the other (according to Yates and Warren 2000) being the Capitosauria. The trematosaurs were a diverse and important group that included many medium-sized to large forms that were semi-aquatic to totally aquatic. The group included long-snouted forms such as the trematosauroids and short, broad-headed forms such as the metoposaurs. Although most groups did not survive beyond the Triassic, one lineage, the brachyopoids, continued until the Cretaceous period. Trematosauria is defined as all stereospondyls more closely related to Trematosaurus than to Parotosuchus, a capitosaurian.Vritramimosaurus
Vritramimosaurus is an extinct genus of large early archosauromorph. Although originally placed in the family Prolacertidae, recent studies on archosauromorph relationships doubt the validity of the family, at least in its broadest sense. Fossils have been found from Early Triassic deposits of the Rassypnaya locality in Orenburg Oblast, Russia. Rassypnaya is located on the Obshchy Syrt, a plateau in the European part of Russia that extends southwest of the Urals toward the Volga River. Vritramimosaurus is similar to the later genus Malutinisuchus, also from Rassypnaya but present in Middle Triassic deposits.
(541.0 Mya–2.5 Gya)
|Archean eon (2.5–4 Gya)|
|Hadean eon (4–4.6 Gya)|