The Yarenskian Gorizont ("Yarenskian Horizon") is a major biostratigraphic unit in Russia corresponding to Upper Olenekian-age terrestrial sediments. It lies above the

Ustmylian Gorizont The Ustmylian Gorizont (geology), Gorizont ("Ustmylian Horizon") is a Lower Triassic biostratigraphic unit in Western Russia. The Ustmylian Gorizont is the youngest subunit of the Vetlugian Supergorizont, lying above the Sludkian Gorizont and below ...

of the Vetlugian Supergorizont, and is located below a short unconformity overlain by the Donguz Gorizont. Some paleontologists elevate the Yarenskian to a supergorizont and subdivide it into two smaller units: the older Fedorovskian Gorizont and the younger Gamskian Gorizont. Others prefer to consider the Fedorovskian and Gamskian to be subgorizonts or members of the Yarenskian. Vertebrate index fossils of the Fedorovskian include the lungfish ''

Gnathorhiza ''Gnathorhiza'' is an extinct genus of prehistoric lobe-finned fish (lungfish) which lived during the Permian period and Early Triassic epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the or ...

,'' the

trematosaurid Trematosauridae are a family of large marine temnospondyl amphibians with many members. They first appeared during the Induan age of the Early Triassic, and existed until around the Carnian stage of the Late Triassic, although by then they wer ...

Inflectosaurus ''Inflectosuchus'' is an extinct genus of prehistoric amphibian. References See also * Prehistoric amphibian * List of prehistoric amphibians This list of prehistoric amphibians is an attempt to create a comprehensive listing of all Genus, ...

,'' and the procolophonid '' Burtensia''. In the Gamskian, these index fossils are replaced by ''

Ceratodus ''Ceratodus'' (from el, κέρας , 'horn' and el, ὀδούς 'tooth') was a wide-ranging genus of extinct lungfish. Fossil evidence dates back to the Early Triassic. A wide range of fossil species from different time periods have been found ...

'', ''

Trematosaurus ''Trematosaurus'' is an extinct genus of trematosaurid temnospondyl amphibian found in Germany and Russia. It was first named by Hermann Burmeister in 1849 and the type species is ''Trematosaurus brauni''. History of study ''Trematosaurus'' ...

'', and ''

Kapes Kapes was a wife of Pharaoh Takelot I and the mother of Pharaoh Osorkon II.Dodson, Aidan and Hilton, Dyan. The Complete Royal Families of Ancient Egypt. Thames & Hudson. 2004. Kapes is mentioned on the Pasenhor stela found in the Serapeum o ...

'', respectively. The Yarenskian as a whole is characterized by the

capitosaur Capitosauria is an extinct group of large temnospondyl amphibians with simplified stereospondyl vertebrae. Mainly living as piscivores in lakes and rivers, the Capitosauria and its sister taxon Trematosauria were the only major labyrinthodonts t ...

amphibian ''

Parotosuchus ''Parotosuchus'' is an extinct genus of capitosaurian temnospondyl amphibians within the family Mastodonsauridae. Fossils are known from the Early Triassic of Europe, Africa, Australia, and Antarctica. It was about long and likely lived in aqua ...

'', and has also been known as the ''Parotosuchus'' fauna. A few geographical influence on the faunas can be observed; erythrosuchids and rhytidosteids are more common in southern exposures while procolophonids and putative " rauisuchids" are more common in the north. The Yarenskian encompasses several svitas (equivalent to

geological formations A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

). The most fossiliferous and best-exposed is the

Petropavlovskaya Svita The Yarenskian Gorizont ("Yarenskian Horizon") is a major biostratigraphic unit in Russia corresponding to Upper Olenekian-age terrestrial sediments. It lies above the Ustmylian Gorizont of the Vetlugian Supergorizont, and is located below a sh ...

, a Fedorovskian-age assemblage in the Cis-Ural region (near the Ural River in

Orenburg Oblast Orenburg Oblast (russian: Оренбургская область, ''Orenburgskaya oblast'') is a federal subject of Russia (an oblast). Its administrative center is the city of Orenburg. From 1938 to 1957, it bore the name ''Chkalov Oblast'' () ...

). Another productive unit is the Gamskian-age

Lipovskaya Formation The Yarenskian Gorizont (geology), Gorizont ("Yarenskian Horizon") is a major biostratigraphic unit in Russia corresponding to Upper Olenekian-age terrestrial sediments. It lies above the Ustmylian Gorizont of the Vetlugian Supergorizont, and is lo ...

, which is found near the Don River in

Volgograd Oblast Volgograd Oblast (russian: Волгогра́дская о́бласть, ''Volgogradskaya oblast'') is a federal subjects of Russia, federal subject (an oblast) of Russia, located in the Volga region, Volga region of Southern Russia. Its adminis ...

. The Caspian Depression includes coastal sediments equivalent to the Yarenskian (such as the Bogdo or Bogdinskaya Svita), though there is some controversy over how the stratigraphy of the area should be defined. Thin exposures of Yarenskian units are also known further north in the Vyatka, Vychegda, Luza, and Pechora basins.

References

Geologic formations of Russia Triassic System of Europe Triassic Russia Olenekian Stage Paleontology in Russia Formations {{Europe-geologic-formation-stub