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Encyclopedia > Paleozoic

The Paleozoic Era (from the Greek palaio, "old" and zoion, "animals", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic eon. The Paleozoic spanned from roughly 542 mya to roughly 251 mya (ICS, 2004), and is subdivided into six geologic periods; from oldest to youngest they are: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... A geologic era is a subdivision of geologic time that is a separate classification that divides the Phanerozoic Eon into three parts timeframes. ... During the Phanerozoic the biodiversity shows a steady but not monotonic increase from near zero to several thousands of genera. ... In general usage, an eon (sometimes spelled aeon) is a very long period of time. ... For other uses of mya, see mya (disambiguation). ... A geologic period is a subdivision of geologic time that divides an era into smaller timeframes. ... For other uses, see Cambrian (disambiguation). ... Artist impression of the Ordovician Sea. ... The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443. ... The Devonian is a major division of the geologic timescale that extends from the end of the Silurian period (360 million years ago (mya)) to the beginning of the Mississippian subperiod of the Carboniferous (408. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... The Permian is a geologic period that extends from about 299. ...

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Paleozoic life

Trilobites flourished throughout the lower Paleozoic era until becoming extinct in the Permian period
Trilobites flourished throughout the lower Paleozoic era until becoming extinct in the Permian period

The Paleozoic covers the time from the first appearance of abundant, hard-shelled fossils to the time when the continents were beginning to be dominated by large, relatively sophisticated reptiles and relatively modern plants. The lower (oldest) boundary was classically set at the first appearance of creatures known as trilobites and archeocyathids. The upper (youngest) boundary is set at a major extinction event 300 million years later, known as the Permian extinction. Modern practice sets the older boundary at the first appearance of a distinctive trace fossil called Trichophycus pedum. Download high resolution version (878x1041, 124 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (878x1041, 124 KB) Wikipedia does not have an article with this exact name. ... Orders Agnostida Redlichiida Corynexochida Lichida Nektaspida? Phacopida Proetida Asaphida Harpetida Ptychopariida Trilobites are extinct arthropods in the class Trilobita. ... The Permian is a geologic period that extends from about 299. ... For other uses, see Fossil (disambiguation). ... Animated, colour-coded map showing the various continents. ... For other uses, see Plant (disambiguation). ... Orders Agnostida Nectaspida Redlichiida Corynexochida Lichida Phacopida Subclass: Librostoma Proetida Asaphida Harpetida Ptychopariida For the robot vacuum cleaner, see Electrolux Trilobite. ... The Archeocyatha, also called Archaeocyathids, were sessile, reef-building marine organisms that lived during the Lower Cambrian period (500-600 million years ago). ... An extinction event (also known as: mass extinction; extinction-level event, ELE) occurs when there is a sharp decrease in the number of species in a relatively short period of time. ... The Permian-Triassic extinction event, sometimes informally called the Great Dying, was an extinction event that occurred approximately 252 million years ago (mya), forming the boundary of the Permian and Triassic geologic periods. ... A fossilized dinosaur footprint at Clayton Lake State Park, New Mexico. ... Trichophycus pedum (or Treptichnus pedum; formerly Phycodes pedum) was one of the earliest animals, and the first found in great abundance. ...


At the start of the era, all life was confined to bacteria, algae, sponges and a variety of somewhat enigmatic forms known collectively as the Ediacaran fauna. A large number of body plans appeared nearly simultaneously at the start of the era -- a phenomenon known as the Cambrian Explosion. There is some evidence that simple life may already have invaded the land at the start of the Paleozoic, but substantial plants and animals did not take to the land until the Silurian and did not thrive until the Devonian. Although primitive vertebrates are known near the start of the Paleozoic, animal forms were dominated by invertebrates until the mid-Paleozoic. Fish populations exploded in the Devonian. During the late Paleozoic, great forests of primitive plants thrived on land forming the great coal beds of Europe and eastern North America. By the end of the era, the first large, sophisticated reptiles and the first modern plants (conifers) had developed. Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Algae have conventionally been regarded as simple plants within the study of botany. ... Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... Dickinsonia costata, an Ediacaran organism of unknown affinity, with a quilted appearance. ... The Cambrian explosion is the geologically kukko sudden appearance in the fossil record of the ancestors of familiar animals, starting about 542 million years ago (Mya). ... This article does not cite any references or sources. ... Invertebrate is an English word that describes any animal without a spinal column. ... For other uses, see Fish (disambiguation). ... This article is about a community of trees. ... Coal Coal (IPA: ) is a fossil fuel formed in swamp ecosystems where plant remains were saved by water and mud from oxidization and biodegradation. ... For other uses, see Europe (disambiguation). ... Orders & Families Cordaitales † Pinales   Pinaceae - Pine family   Araucariaceae - Araucaria family   Podocarpaceae - Yellow-wood family   Sciadopityaceae - Umbrella-pine family   Cupressaceae - Cypress family   Cephalotaxaceae - Plum-yew family   Taxaceae - Yew family Vojnovskyales † Voltziales † The conifers, division Pinophyta, are one of 13 or 14 division level taxa within the Kingdom Plantae. ...


Tectonics

Geologically, the Paleozoic starts shortly after the breakup of a supercontinent called Pannotia and at the end of a global ice age. (See Varanger glaciation and Snowball Earth). Throughout the early Palaeozoic, the Earth's landmass was broken up into a substantial number of relatively small continents. Toward the end of the era, the continents gathered together into a supercontinent called Pangaea, which included most of the Earth's land area. Download high resolution version (780x783, 111 KB)plate tectonics 290ma File links The following pages link to this file: Geology of the Himalaya ... In geology, a supercontinent is a land mass comprising more than one continental core, or craton. ... Pannotia is the name given to a hypothetical supercontinent that existed from about 600 to about 540 mya. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... The Cryogenian Period (from Greek cryos ice and genesis birth) is the second geologic period of the Neoproterozoic Era, followed by the Ediacaran Period. ... One computer simulation of conditions during the Snowball Earth period. ... In geology, a supercontinent is a land mass comprising more than one continental core, or craton. ... For other uses, see Pangaea (disambiguation). ...


Climate

The Early Cambrian climate was probably moderate at first, becoming warmer over the course of the Cambrian, as the second-greatest sustained sea level rise in the Phanerozoic got underway. However, as if to offset this trend, Gondwana moved south with considerable speed, so that, in Ordovician time, Most of West Gondwana (Africa and South America) lay directly over the South Pole. The Early Paleozoic climate was also strongly zonal, with the result that the "climate", in an abstract sense became warmer, but the living space of most organisms of the time -- the continental shelf marine environment -- became steadily colder. However, Baltica (Northern Europe and Russia) and Laurentia (eastern North America and Greenland) remained in the tropical zone, while China and Australia lay in waters which were at least temperate. The Early Paleozoic ended, rather abruptly, with the short, but apparently severe, Late Ordovician Ice Age. This cold spell caused the second-greatest mass extinction of Phanerozoic time. Image File history File links Broom_icon. ... For other uses of Gondwana and Gondwanaland, see Gondwana (disambiguation). ... For other uses, see South Pole (disambiguation). ... Baltica (green) Baltica is a Late Proterozoic-Early Palaeozoic continent that now includes the East European craton of northwestern Eurasia. ... This article or section does not adequately cite its references or sources. ...


The Middle Paleozoic was a time of considerable stability. Sea levels had dropped coincident with the Ice Age, but slowly recovered over the course of the Silurian and Devonian. The slow merger of Baltica and Laurentia, and the northward movement of bits and pieces of Gondwana created numerous new regions of relatively warm, shallow sea floor. As plants took hold on the continental margins, oxygen levels increased and carbon dioxide dropped, although much less dramatically. The north-south temperature gradient also seems to have moderated, or metazoan life simply became hardier, or both. At any event, the far southern continental margins of Antarctica and West Gondwana became increasingly less barren. The Devonian ended with a series of turnover pulses which killed off much of Middle Paleozoic vertebrate life, without noticeably reducing species diversity overall.


The Late Paleozoic was a time which has left us a good many unanswered questions. The Mississippian Epoch began with a spike in atmospheric oxygen, while carbon dioxide plummeted to unheard-of lows. This destabilized the climate and led to one, and perhaps two, ice ages during the Carboniferous. These were far more severe than the brief Late Ordovician Ice; but, this time, the effects on world biota were inconsequential. By the Cisuralian, both oxygen and carbon dioxide had recovered to more normal levels. On the other hand, the assembly of Pangea created huge arid inland areas subject to temperature extremes. The Lopingian is associated with falling sea levels, increased carbon dioxide and general climatic deterioration, culminating in the devastation of the Permian extinction. The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... Lopingian is the third of the three epoches of the Permian. ... The Permian-Triassic extinction event, sometimes informally called the Great Dying, was an extinction event that occurred approximately 252 million years ago (mya), forming the boundary of the Permian and Triassic geologic periods. ...


See also

The geologic time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. ...

References and further reading

  • British Palaeozoic Fossils, 1975, The Natural History Museum, London.
  • International Commission on Stratigraphy (ICS). Home Page. Retrieved on September 19, 2005.
Wikimedia Commons has media related to:
Paleozoic
Paleozoic era
Cambrian Ordovician Silurian Devonian Carboniferous Permian
Phanerozoic eon
Paleozoic era Mesozoic era Cenozoic era

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Palaeos Paleozoic: The Paleozoic Era (1615 words)
For most of the Paleozoic, Greenland remained close to the equator and, after Baltica sutured to Laurentia (North America plus Greenland) during the Silurian, this longitude came to correspond quite closely to the longitude of the future Greenwich, England, which defines the present conventional 0° longitude line.
The early Paleozoic saw many of the continents clustered around the equator, with Gondwana (representing the bulk of old Rodinia) slowly drifting south across the South poles, and Siberia, Laurentia (North America plus Greenland) and Baltica converging in the tropics.
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The Paleozoic is bracketed by two of the most important events in the history of animal life.
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