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Permian Period—298.9 to 251.9 MYA

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flat-topped reef mountain
Permian age ancient reef formation, Guadalupe Mountains National Park, Texas.

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Introduction

In 1841 British geologist Roderick Impey Murchison named this system from the province of Perm in Russia, where it consists of a great thickness of limestone overlying Carboniferous strata. Before formally naming this system, Murchison ascertained that Permian strata could be identified in widespread areas by their distinctive fossils (Eicher 1976).

Significant Permian events

During the Permian Period, Earth’s crustal plates formed a single, massive continent called Pangaea. In the correspondingly large ocean, Panthalassa, marine organisms such as brachiopods, gastropods, cephalopods (nautiloids and ammonoids), and crinoids were present. On land, reptiles replaced amphibians in abundance. The most devastating incidence of mass extinction in Earth’s history marked the end of the Permian Period.

Learn about what events during the Permian Period

During the Permian Period, all the world’s landmasses were joined into a single continent that spread from pole to pole. Pangaea was shaped like a huge letter “C” facing eastward. The open part of the letter cupped the Tethys Ocean. The spine of the “C” was adjacent to a long subduction zone, which formed the eastern margin of the Pacific basin. Much of Earth’s surface was covered by a large ocean called Panthalassa.

The meeting of continents created arid conditions, just as great deserts are located at the interior of most continents today. Only portions of this vast continent received rainfall throughout the year, and without the moderating effect of nearby bodies of water, great seasonal fluctuations occurred. In addition, the formation of Pangaea reduced the total amount of shoreline, and thus the amount of coastal marine habitat, a possible factor in the extinction at the end of the period that devastated marine life.
Under arid conditions during the Permian, amniotes, which did not depend on permanent bodies of water to reproduce, began to dominate terrestrial environments. The early Permian Period was dominated by the pelycosaurs, both herbivores and carnivores. The most spectacular pelycosaurs were the plant-eating Edaphosaurus and the meat-eating Dimetrodon, which is well-known amongst school children for the striking “sails” on its back. Dimetrodon is often mistaken to be a dinosaur; however, the first dinosaurs did not appear until the Triassic. Scientists have postulated that the large dorsal “fin” of Dimetrodon was used to help regulate internal body temperature by serving as a radiator to either collect or lose heat, depending upon whether the “sail” faced the sun.

By the mid-Permian, other amniote groups appeared. One group, the therapsids, evolved from the pelycosaurs and is important to us because they eventually evolved into mammals. They had complex, powerful jaws with differently shaped teeth that performed various functions. Their legs were positioned more vertically under their bodies, and they likely had warm-blooded metabolisms.
The largest extinction event in Earth’s history—far more devastating than the more famous Cretaceous extinction when the dinosaurs disappeared—marks the end of the Permian. Scientists estimate that more than half (53%) of all taxonomic families were lost. This translates to 95% of all species, including 70% of all land species (i.e., plants, animals, and insects). The cause may have been climate change resulting in a worldwide lowering in sea level. Some notable groups that disappeared include the remaining trilobite species, the rugose and tabulate corals, all blastoids (crinoid-like animals), and the fusulinid foraminifera (large “amoebas with shells”). Many groups suffered heavy losses and nearly died out including crinoids, brachiopods, bryozoans, gastropods, and ammonoids.

The Permian mass extinction came closer than any other extinction event in the fossil record to wiping out life on Earth. Yet the extinctions of species were selective and uneven. Finding a cause that would affect both land-dwelling and marine organisms is challenging. If the cause was sea-level change, lowering of sea level would greatly reduce shallow, marine habitats, but not terrestrial habitats. Therefore, the probable link between extinctions in these habitats may be climate change. When sea level fell, great quantities of organic deposits from shallow-water organisms became exposed to the atmosphere. Oxidation of this material produced carbon dioxide (CO_2), a greenhouse gas, which traps heat near Earth’s surface. Additionally, one of the largest episodes of continental volcanism occurred at the end of Permian time in what is now central Siberia. The volcanic gases released during the eruptions were sources of greenhouse gases (CO_2 and sulfur dioxide [SO_2]). Because changes in concentrations of greenhouse gases can have substantial effects on climate, a sudden increase in such gases could have had a detrimental effect on many species.

Finally, because Pangaea stretched from pole to pole near the end of the Permian, conditions were appropriate for the formation of polar ice caps, which evidence shows did indeed occur. The large and rapid sea-level fluctuations near the end of the Permian were at least partly the result of waxing-and-waning glaciers. The large sea-level drop at the end of the Permian was followed quite rapidly by general global warming and a substantial rise in sea level. With volcanic eruptions, climatic variability, and abrupt sea-level changes, the world at the end of the Permian was a particularly harsh place for many life-forms. Hence, any or all of these changes could have played a role in the biological devastation that occurred.

Visit—Permian Parks

Every park contains some slice of geologic time. Below, we highlight selected parks associated with the Permian Period. This is not to say that a particular park has only rocks from the specified period. Rather, rocks in selected parks exemplify a certain event or preserve fossils or rocks from a certain geologic age.

More about the Paleozoic

Last updated: September 28, 2020