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The Serpukhovian is in the ICS geologic timescale the uppermost stage or youngest age of the Mississippian, the lower subsystem of the Carboniferous. The Serpukhovian age lasted from Ma to Megaannum.; 2004: A Geologic Time Scale 2004, Cambridge University Press. It is preceded by the Visean and is followed by the Bashkirian. The Serpukhovian correlates with the lower part of the Namurian Stage of European stratigraphy and the middle and upper parts of the Chesterian Stage of North American stratigraphy.
The base of the Serpukhovian is informally defined by the first appearance of the conodont Lochriea, though the utility and systematic stability of this species is not yet certain. No lower GSSP has been assigned to the Serpukhovian Stage yet. Two candidate GSSPs have been proposed: the Verkhnyaya Kardailovka section in the South Urals of Russia, and the Naqing (Nashui) section in Guizhou, China.
The top of the stage (the base of the Pennsylvanian subsystem and Bashkirian stage) is at the first appearance of the conodont Declinognathodus in the lower Bird Spring Formation, which overlies the Battleship Formation in Nevada.; 1999: The IUGS boundary in the middle of the Carboniferous: Arrow Canyon, Nevada, USA, Episodes 22 (4), pp 272–283 It is also slightly above the first appearance of the foraminifera Globivalvulina, genozone of the ammonoid genus Homoceras and the ammonoid biozone of Isohomoceras.; 2006: Global time scale and regional stratigraphic reference scales of Central and West Europe, East Europe, Tethys, South China, and North America as used in the Devonian–Carboniferous–Permian Correlation Chart 2003 (DCP 2003), Palaeogeography, Palaeoclimatology, Palaeoecology 240 (1-2): pp 318–372
In North America, the stage encompassed four conodont biozones: the Rhachistognathus muricatus Zone (youngest), Adetognathus unicornis Zone, Cavusgnathus naviculus Zone, and Gnathodus bilineatus Zone (in part, oldest).
In the regional stratigraphy of the United Kingdom (and Western Europe as a whole), the Serpukhovian corresponds to the lower half of the Namurian regional stage. This portion of the Namurian includes three substages, from oldest to youngest: the Pendleian, Arnsbergian and Chokierian. Only the lowermost Chokierian falls in the Serpukhovian, the upper part of the substage corresponds to the earliest Bashkirian.; 2006: The Carboniferous system, use of the new official names for the subsystems, series and stages, Geologica Acta 4 (3), pp 403–407
In North America, the Serpukhovian corresponds to the upper part of the Chesterian regional stage, while in China the Serpukhovian is roughly equivalent to the Dewuan regional stage.
Sepkoski (1996) plotted an extinction rate of around 23-24% for the Serpukhovian as a whole, based on marine Genus which persist through multiple stages. Bambach (2006) found an early Serpukhovian extinction rate of 31% among all marine genera. Using an extinction probability procedure generated from the Paleobiology Database, McGhee et al. (2013) estimated an extinction rate as high as 39% for marine genera. On the other hand, Stanley (2016) estimated that the extinction was much smaller, at a loss of only 13-14 % of marine genera.
Relative to other biological crises, the Serpukhovian extinction was much more selective in its effects on different evolutionary faunas. Stanley (2007) estimated that the early Serpukhovian saw the loss of 37.5% of marine genera in the Paleozoic evolutionary fauna. Only 15.4% of marine genera in the modern evolutionary fauna would have been lost along the same time interval. This disconnect, and the severity of the extinction as a whole, is reminiscent of the Late Devonian extinction events. Another similarity is how the Serpukhovian extinction was seemingly driven by low rates of speciation, rather than particularly high rates of extinction.
It is disputed whether the aftermath of the extinction saw a relative stagnation of biodiversity or a major increase. Some studies have found that in the following Late Paleozoic Ice Age (LPIA) of the Late Carboniferous and Early Permian, both speciation and extinction rates were low, with this stagnation in biological diversity driven by a reduction of carbonate platforms, which otherwise would have helped to maintain high biodiversity. More recent studies have instead argued that biodiversity surged during the LPIA in what is known as the Carboniferous-Earliest Permian Biodiversification Event (CPBE). Foraminifera especially saw extremely rapid diversification. The CPBE may have been caused by the dramatically increased marine provincialism resulting from sea level fall during the LPIA, combined with the assembly of Pangaea, which limited the spread of taxa from one region of the world ocean to another.
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