Пермдің орта ғасыры: Гвадалуп дәуірі

Second series and epoch of the Permian

The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± 0.5 – 259.1 ± 0.4 Mya. The series saw the rise of the therapsids, a minor extinction event called Olson's Extinction and a significant mass extinction called the end Capitanian extinction event. The Guadalupian was previously known as the Middle Permian.

The Guadalupian is the second and middle series or epoch of the Permian. Previously called Middle Permian, the name of this epoch is part of a revision of Permian stratigraphy for standard global correlation. The name "Guadalupian" was first proposed in the early 1900s, and approved by the International Subcommission on Permian Stratigraphy in 1996. References to the Middle Permian still exist. The International Chronostratigraphic Chart V2021/07 provides a numerical age of 273.01 ± 0.14 – 259.51 ± 0.21 mya.

Therapsids became the dominant land animals in Guadalupian, displacing the pelycosaurs. Therapsids evolved from a group of pelycosaurs called sphenacodonts. Therapsida consists of four major clades: the dinocephalians, the herbivorous anomodonts, the carnivorous biarmosuchians, and the mostly carnivorous theriodonts. This extinction was originally called Olson's Gap because it was thought to be a problem in preservation of fossils. Since the 1990s it has been renamed Olson's Extinction. This extinction event occurred near the beginning of the epoch and led to an extended period of low diversity when two thirds of terrestrial vertebrate life was lost worldwide. Global diversity rose dramatically by the end probably the result of disaster taxa filling empty guilds, only to fall again when the end Guadalupian event caused a diversity drop in the Wuchiapingian. Whether this climate change was a result of Earth's natural processes or exacerbated by another event is unknown.

The climate resembled that of much of central Asia today. Pangea was a supercontinent and had very hot dry summers and cold bitter winters. At this time on the equator there was a desert that reached 74 degrees Celsius. The coasts were tropical and had monsoons.

The Wordian Stage was between 268.8 ± 0.5 – 265.1 ± 0.4 Mya. The base of the Wordian Stage is defined as the place in the stratigraphic record where fossils of conodont species Jinogondolella aserrata first appear. The global reference profile for this stratigraphic boundary is located at Getaway Ledge in the Guadalupe Mountains of Texas. The top of the Wordian (the base of the Capitanian Stage) is defined as the place in the stratigraphic record where the conodont species Jinogondolella postserrata first appears.

The Capitanian Stage was between 265.1 ± 0.4 – 259.8 ± 0.4 Mya. The Guadalupian ended with a deteriorating environment, Greenhouse conditions, and several series of mass extinctions; both the great dinocephalians, other taxa on land and various invertebrates in the sea. They would be succeeded by new types of therapsids, especially the gorgonopsians among others. This extinction event may be related to the much larger Permian–Triassic extinction event that followed about 10 million years later. Carbon isotopes in marine limestone from the Capitanian Age show an increase in δ13C values. The change in carbon isotopes in the sea water reflects cooling of global climates. This climatic cooling may have caused the end Capitanian extinction event among species that lived in warm water, like larger fusulinids (Verbeekninidae), large bivalves (Alatoconchidae) and rugose corals, and Waagenophyllidae.