Permian

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Permian

The Permian period, 280 to 230 million years ago, was named for the Perm Province of the Ural Mountains in Russia. The Permian signaled the end of the "ancient life" Paleozoic era.

In the Permian, the close ties between geology and evolution were especially apparent. The two great land masses of the Paleozoic drifted close enough together to form one supercontinent, Pangaea. Collisions in the tectonic plates created extensive volcanic activity and heaved up the Urals, Alps, Appalachians, and Rocky Mountains. The shallow inland seas drained to leave deposits of gypsum and salt. Vast sand dunes throughout much of what is now North America and Europe were recorded by massive yellow sandstones (hardened sand dunes) that contained few fossils other than scorpions.

Great glaciers scoured the southern regions of Africa, India, and Australia, further inhibiting life. Conifers and a few cold-hardy plants grew along the fringes of the immense ice cap.

The long stable climate of the Carboniferous gave way to dryness, with severe fluctuations of heat and cold. Only in the tropics of Pangaea did anything remain of the great Carboniferous rain forests, and there insects and amphibians continued to evolve.

Insects, members of the arthropod or "jointed leg" animals whose ancestors were the first to explore both land and air, continued to flourish in every new ecological opportunity. Several new groups appearedthe bugs, cicadas, and beetles. Thanks possibly to their diminutive size and adaptable metamorphosis, in which young live and feed in a totally different

EraPeriodEpochMillion Years Before Present
PaleozoicPermian286
Pennsylvanian320
Missipian360
Devonian408
Silurian438
Ordovician505
Cambrian570

environment from adults, the arthropods became the most evolutionarily successful animals on Earth. Amphibians fared less well, mostly just hanging on in those areas still hospitable to their warm, moist requirements.

Many marine species thrived in the shallow seas. Thousands of types of sponges, corals, ammonites , bryozoans, brachiopods , and snails left their remains in the rocks that now make up the mountains of west Texas and southern New Mexico. Bony fishes remained plentiful. However, spiny fishes, the fleshy-finned rhipidistians (organisms who originally gave rise to amphibians), and the once-dominant trilobites disappeared.

Reptiles flourished in the semidesert regions that made up much of Pangaea. Their leathery-skinned, cold-blooded bodies were ideal for the hotter, drier climate. Reptile adaptations led to herbivores and insectivores who could exploit new food resources. As their legs continued to become stronger and more upright, the reptiles increased in body size and mobility. Coelorosauravus joined the flying insects, gliding from tree to tree by means of a sail-like membrane. And Mesosaurus, a 1 meter (3 feet) long fish eater, returned to living underwater. Virtually the whole of Pangaea was dominated by the reptiles.

However, all this exuberance ended. The close of the Permian was marked by the worst extinction ever recorded. More than 75 percent of all plant and animal groups disappeared forever from the land, and in the ocean only about 5 percent of existing species survived. As devastating as these losses were, evolution and extinction are a recurring theme: the emptying of habitats , the reshuffling of genes , and a new start. Survival of the fittest might really be said to be survival of the luckiest.

see also Geological Time Scale.

Nancy Weaver

Bibliography

Asimov, Isaac. Life and Time. Garden City, NY: Doubleday & Company, 1978.

Fortey, Richard. Fossils: The Key to the Past. Cambridge, MA: Harvard University Press, 1991.

. Life: A Natural History of the First Four Billion Years of Life on Earth. New York: Viking Press, 1998.

Friday, Adrian, and David S. Ingram, eds. The Cambridge Encyclopedia of Life Sciences. London: Cambridge University, 1985.

Gould, Stephen Jay, ed. The Book of Life. New York: W. W. Norton & Company, 1993.

McLoughlan, John C. Synapsida: A New Look Into the Origin of Mammals. New York: Viking Press, 1980.

Steele, Rodney, and Anthony Harvey, eds. The Encyclopedia of Prehistoric Life. New York: McGraw Hill, 1979.

Wade, Nicholas, ed. The Science Times Book of Fossils and Evolution. New York: The Lyons Press, 1998.

Permian Period

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Permian Period

In geologic time , the Permian Period, the last period of the Paleozoic Era , covers the time roughly 286 million years ago (mya) until 245 mya.

The Permian Period spans two epochs. The Early Permian Epoch is the most ancient, followed by the Late Permian Epoch.

The Early Permian Epoch is divided chronologically (from the most ancient to the most recent) into the Asselian, Sakmarian, and Artinskian stages. The Late Permian Epoch is divided chronologically (from the most ancient to the most recent) into the Kungurian, Kazanian, and Tatarian stages.

In terms of paleogeography (the study of the evolution of the continents from supercontinents and the establishment of geologic features), the Permian Period was dominated by the movements of the supercontinent Pangaea, that during the Permian Period was located along the equator. Plate tectonic activity along the western border of Pangaea formed an extensive subduction zone that survives today as a large number of volcanoes located around the Pacific rim (i.e., the Pacific "Ring of Fire").

Differentiated by fossil remains and continental movements, the Carboniferous Period (360 mya to 286 mya) preceded the Permian Period. In many modern geological texts, especially those in the United States, the time of Carboniferous Period is covered by two alternate geologic periods, the Mississippian Period (360 mya to 325 mya) and the Pennsylvanian Period (325 mya to 286 mya). The Permian Period is followed in geologic time by start of the Triassic Period of the Mesozoic Era . The largest mass extinction in Earth's historya catastrophic extinction of marine life marks the close of both the Permian Period and the Paleozoic Era. Accordingly, many fossils dated to the Permian Period are not found in Mesozoic Era formations.

The fossil record indicates that more than 95% of all Permian species became extinct at the close of the Permian Period. Alternative hypotheses integrate differently the effects of loss of marine habitat due to the continued fusion of continents into Pangaea.

There were a number of major impacts from large meteorites during the Permian Period. Although no crater has been specifically identified with the impact possibly associated with the mass extinction of species, indirect evidence in the form of catastrophically fused quartz crystals (shocked quartz) in area of Antarctica indicates that the crater measured approximately 300 mi (450 km) in diameter. Other but smaller impact craters dating to the Permian Period have been identified in modern Florida, Quebec, and Brazil.

Because of the fusion and confluence of continental land masses in Pangaea, locations as diverse as Texas (Glass Mountains), Nova Scotia (Brule Trackways), and Germany share a similar fossil record dating to the Permian Period.

See also Archean; Cambrian Period; Cenozoic Era; Cretaceous Period; Dating methods; Devonian Period; Eocene Epoch; Evolution, evidence of; Fossils and fossilization; Historical geology; Holocene Epoch; Jurassic Period; Miocene Epoch; Oligocene Epoch; Ordovician Period; Paleocene Epoch; Phanerozoic Era; Pleistocene Epoch; Pliocene Epoch; Precambrian; Proterozoic Era; Quaternary Period; Silurian Period; Tertiary Period

Permian

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Permian Final period (290–248 Ma) of the Palaeozoic Era, which is named after the central Russian province of Perm. The period is often noted for the widespread continental conditions that prevailed in the northern hemisphere and for the extensive nature of the southern hemisphere glaciation. Many groups of animals and plants, including the rugose corals (Rugosa), trilobites (Trilobita), and blastoid echinoderms (Blastozoa), vanished at the end of the Permian, in a mass extinction that was one of the great crises in the history of life. The period is divided into seven ages: the Asselian, Sakmarian, Artinskian, and Kungurian Ages in the Early Permian Epoch (290–256.1 Ma); and the Ufimian, Kazanian, and Tatarian Ages in the Late Permian Epoch (256.1–248 Ma).

Permian

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Permian The last geological period in the Palaeozoic era. It extended from the end of the Carboniferous period, about 286 million years ago, to the beginning of the Mesozoic era, about 248 million years ago. It was named by the British geologist Roderick Murchison (1792–1871) in 1841 after the Perm province in Russia. In some areas continental conditions prevailed, which continued into the following period, the Triassic. These conditions resulted in the deposition of the New Red Sandstone. During the period a number of animal groups became extinct, including the trilobites, tabulate and rugose corals, and blastoids (see mass extinction). Amphibians and reptiles continued to be the dominant land animals and gymnosperms replaced ferns, clubmosses, and horsetails as the dominant plants.

Permian

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Permian The final period of the Palaeozoic Era, about 286–248 Ma ago. It is named after the central Russian province of Perm. The period is often noted for the widespread continental conditions that prevailed in the northern hemisphere and for the extensive nature of the southern hemisphere glaciation. Many groups of animals and plants vanished at the end of the Permian in one of the most extensive of all mass extinctions. It was during this period that the Pteridophyta were superseded as the dominant vegetation by the gymnosperms.

Permian

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Permian The final period of the Palaeozoic Era, about 290–248 Ma ago. It is named after the central Russian province of Perm. The period is often noted for the widespread continental conditions that prevailed in the northern hemisphere and for the extensive nature of the southern hemisphere glaciation. Many groups of animals and plants (including the rugose corals, trilobites, and blastoid echinoderms) vanished at the end of the Permian in one of the most extensive of all mass extinctions. It was during this period that the Pteridophyta were superseded as the dominant vegetation by the gymnosperms and the first gliding flight by tetrapods occurred (about 260 Ma ago).

Permian

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Permian The final period of the Palaeozoic Era, about 299–251 Ma ago. It is named after the central Russian province of Perm. The period is often noted for the widespread continental conditions that prevailed in the northern hemisphere and for the extensive nature of the southern hemisphere glaciation. Many groups of animals and plants vanished at the end of the Permian in one of the most extensive of all mass extinctions, including the Rugosa, Trilobitomorpha, and Blastoidea.

Permian

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Permian Geological period of the Palaeozoic era lasting from 286 to 248 million years ago. There was widespread geologic uplift and mostly cool, dry climates with periods of glaciation in the southern continents. Many groups of marine invertebrate animals became extinct during the period.

Permian

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Permian (geol.) pert. to the upper division of palaeozoic strata, characteristic of Perm, former province of E. Russia. XIX. See -IAN.