Cisuralian

The Cisuralian is the first series or epoch of the Permian.[3] The Cisuralian was preceded by the last Pennsylvanian epoch (Gzhelian) and is followed by the Permian Guadalupian epoch.

The name "Cisuralian" was proposed in 1982,[4] and approved by the International Subcommission on Permian Stratigraphy in 1996.[5] The Cisuralian Epoch is named after the western slopes of the Ural Mountains in Russia and Kazakhstan.[6][7][8]

Limestones on the edge of Russian Platform and make up the Ishimbay oil fields. These oil fields were vital to the Soviet Union during WW2 when the Germans controlled the oil fields to the west.[6]

The International Chronostratigraphic Chart (v2018/07)[3] provides a numerical age of 298.9 ± 0.15 – 272.3 ± 0.5 Mya.[9]

The base of the Cisuralian series and the Permian system is defined as the place in the stratigraphic record where fossils of the conodont Streptognathodus isolatus first appear. The global reference profile for the base (the GSSP or golden spike) is located in the valley of the Aidaralash River, near Aqtöbe in the Ural Mountains of Kazakhstan.[10]

The World at the start of the Cisuralian

Gondwana collided Laurussia and created the Alleghenian orogeny in present-day North America.[6] In northwestern Europe the Hercynian orogeny continued.[6] This created the large supercontinent, Pangea by the middle of the Early Permian Epoch which was to have an impact on the climate.[6]

Selwyn Rock, South Australia, an exhumed glacial pavement of Permian age

At the start of the Permian, the Earth was still in an ice age, which began in the Carboniferous. Glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continent's interiors.[11]

Dimetrodon, a Pelycosaur, was top of the food chain in the Cisuralian

The swampy fringes were mostly ferns, seed ferns, and lycophytes. The series saw the appearance of beetles and flies.[6]

The coal swamps from the Carboniferous continued and the herbivores, Diadectes and Edaphosaurus.[7] The dry interior with small insectivores. Caseids and proto-therapsid Tetraceratops made their appearance.[7] The marine life was probable more diverse than modern times as the climate warmed.[6] Unusual sharks such as Helicoprion continued in this series.

Helicoprion bessonovi with characteristic 'tooth-whorl' at front of jaw.

Early Permian terrestrial faunas were dominated by pelycosaurs, diadectids and amphibians,[12][13] The pelycosaurs appeared during the Late Carboniferous and reached their apex in the Cisuralian remaining the dominant land animals for some 40 million years.[7] A few continued into the Capitanian. They were succeeded by the therapsids.[7]