In the geologic timescale, the Olenekian is an age in the 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...

 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 a stage in 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 249.7 ± 0.7 Ma and 245 ± 0.7 Ma (million years ago). The Olenekian follows the Induan

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 ± 0.4 Ma and 249.7 ± 0.7 Ma...

 and is followed by the Anisian

Anisian

In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 245 million years ago until 237 million years ago, approximately...

.

The Olenekian saw the deposition of a large part of the Buntsandstein

Buntsandstein

The Buntsandstein or Bunter sandstone is a lithostratigraphic and allostratigraphic unit in the subsurface of large parts of west and central Europe...

 in Europe. Archosaurs - a group encompassing crocodiles, pterosaurs, dinosaurs, and ultimately birds - are diapsid

Diapsid

Diapsids are a group of reptiles that developed two holes in each side of their skulls, about 300 million years ago during the late Carboniferous period. Living diapsids are extremely diverse, and include all crocodiles, lizards, snakes, and tuatara...

 reptiles that first evolved from Archosauriform

Archosauriformes

Archosauriformes is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Late Permian...

 ancestors during the Olenekian.

The Olenekian is roughly coeval with the regional Yongningzhenian stage used in 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 Olenekian stage was introduced into scientific literature by Russian stratigraphers in 1956. The stage is named after Olenëk in Siberia

Siberia

Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

. Before the subdivision in Olenekian and Induan became commongood, both stages formed the Skythian stage, which has since disappeared from the official timescale.

The base of the Olenekian is at the lowest occurrence of 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 Hedenstroemia or Meekoceras gracilitatis, and of 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...

 Neospathodus waageni. It is defined as ending near the lowest occurrences of genera Japonites, Paradanubites, and Paracrochordiceras; and of the conodont Chiosella timorensis. A GSSP (global reference profile for the base) has in 2009 not yet been established.

The Olenekian is sometimes divided into the Smithian and the Spathian subages or substages.

Palaeontology

• Gnathorhizids
  Gnathorhizidae
  The Gnanthorhizidae are an extinct family of lungfish that lived from the late Carboniferous until the middle Triassic. Gnathorhizid fossils have been found in North America, Madagascar, Australia, and possibly Eastern Europe and South Africa...
  
  

• Archosaur
  Archosaur
  Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
  
  s
• Erythrosuchids
  Erythrosuchidae
  Erythrosuchidae are a family of large basal archosauromorph carnivores that lived from the later Early Triassic to the early Middle Triassic . Their fossil remains are known so far from South Africa , the Perm region of Russia, and China...
  
  
• Proterosuchids
  Proterosuchidae
  Proterosuchidae 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...
  
  
• Crurotarsi
  Crurotarsi
  The Crurotarsi are a group of archosauriformes, represented today by the crocodiles,...
  
  
  • Rauisuchia
    Rauisuchia
    Rauisuchia is a group of predatory and mostly large Triassic archosaurs. As a clade, Rauisuchia includes these Triassic forms and all crocodylomorphs, which are descendants of Triassic rauisuchians. The group in its traditional sense is paraphyletic, because it does not include crocodylomorph...
    
    

†Archosauromorphs (non-archosaurian)

†Non-archosaurian 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...  Archosauromorphs of the Olenekian
Taxa	Presence	Location	Description	Images
Chasmatosuchus Chasmatosuchus Not to be confused with Chasmatosaurus.Chasmatosuchus was a large archosauriform reptile from the early Triassic period of South Africa and China. It is one of the earliest well-known archosauriforms. It was over 6 ft long and is thought to have behaved like a modern crocodile...
Garjainia
Sharovipteryx Sharovipteryx Sharovipteryx , was an early gliding reptile, from the middle-late Triassic period . Fossils have been found from the Madygen Formation of Kyrgyzstan along with the unusual reptile Longisquama...		Madygen, Kyrgyzstan

†Ichthyosaurs

†Ichthyosauria of the Olenekian
Taxa	Presence	Location	Description	Images
Chaohusaurus Chaohusaurus Chaohusaurus geishanensis was an ichthyosaur, an extinct marine reptile, from the Early Triassic of Chaohu, China. It has also been called Anhuisaurus and Chensaurus. It was described by Young and Dong in 1972...
Grippia Grippia Grippia is a genus of ichthyosaur, an extinct group of reptiles that resembled dolphins. Fossils have been found along the coasts of Greenland, China, Japan, and Canada; of Early Triassic age. These ichthyosaurs were small; they were 1 - 1.5 m in length...
Utatsusaurus Utatsusaurus Utatsusaurus is the earliest-known form of an ichthyopterygian , which lived in the early Triassic period . Unlike the more advanced ichthyosaurs, Utatsusaurus has no dorsal fin and has a broad skull that tapers slowly toward the snout...		Japan, Canada

†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 Olenekian
Taxa	Presence	Location	Description	Images
Cynognathus Cynognathus Cynognathus crateronotus was a meter-long predator of the Early to Middle Triassic. It was among the more mammal-like of the Synapsids, a member of a grouping called Eucynodontia. The genus Cynognathus had an almost worldwide distribution...
Kannemeyeria Kannemeyeria Kannemeyeria was a large dicynodont of the family Kannemeyeriidae, one of the first representatives of the family, and hence one of the first large herbivores of the Triassic...

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 Press

Cambridge 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 - Olenekian
• 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.