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Topic: Late Devonian extinction

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Devonian period

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	Reference.com/Encyclopedia/Devonian
		The Devonian is a geologic period of the Paleozoic era.
		The paleogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, and the early formation of the small supercontinent of Euramerica in the middle.
		The continent Euramerica (or Laurussia) was created in the early Devonian by the collision of Laurentia and Baltica, which rotated into the natural dry zone along the Tropic of Capricorn, which is formed as much in Paleozoic times as nowadays by the convergence of two great airmasses, the Hadley cell and the Ferrel cell.
	www.reference.com /browse/wiki/Devonian (1307 words)

	Palaeos Paleozoic : Devonian : The Late Devonian Period
		Late Devonian stratigraphy has been intensively studied; and there seems to be considerable agreement on basics, particularly for the Euramerican world.
		"The Devonian Period was characterized by major changes in both the terrestrial biosphere e g the evolution of trees and seed plants and the appearance of multi-storied forests, and in the marine biosphere an extended biotic crisis that decimated tropical marine benthos, especially the stromatoporoid tabulate coral reef community.
		The Late Devonian period marked the time when the first tetrapods animals evolved from their sarcopterygian ancestors.
	www.palaeos.com /Paleozoic/Devonian/LateDev.html (1468 words)

	Extinction Events
		This late Devonian crisis affected these organisms so severely that reef-building was relatively uncommon until the evolution of the scleractinian (modern) corals in the Mesozoic era.
		Many paleontologists to attribute the Devonian extinction to an episode of global cooling, similar to the event which is thought to have cause the late Ordovician mass extinction.
		According to this theory,the extinction of the Devonian was triggered by another glaciation event on Gondwana, as evidenced by glacial deposits of this age in northern Brazil.
	www.lakepowell.net /sciencecenter/extinction_events.htm (1939 words)

	Chapter 12 Study Guide
		Extinction of the tabulate coral and stromatoporoids at the end of the Devonian changed the composition of reefs in the Carboniferous.
		The reef framework was a loose construction of bryozoa, brachiopods, and crinoids that baffled and trapped fine-grained sediment, encasing the reef in mud.
		Summarize the hypotheses for the cause(s) of this extinction.
	www.uvm.edu /~cmehrten/courses/historical/ch15sg.html (1871 words)

	Devonian Period
		The Devonian was proposed by Roderick I. Murchison and Adam Sedgewick in 1840.
		The base of the Devonian is defined immediately at the first appearance of the graptolite species Monograptus uniformis in the rhythmically alterating limestones and calcareous shales of ‘Bed 20’ in the Klonk Section, which is located about 35km southwest of Prague, near the village of Suchomasty, in the Czech Republic.
		The youngest Devonian and earliest Carboniferous beds are characterized by a sequence of predominantly biodetrital oolitic limestone within a pelagic matrix of shale and cephalopod bearing calcilutites.
	www.peripatus.gen.nz /paleontology/Devonian.html (1266 words)

	Paleobiology 4
		The late Paleozoic, the subject of this chapter, saw the spread of plant life over the land surface and the emergence and diversification of amphibians and their descendants the reptiles as dominant animal life on land.
		The earliest terrestrial vertebrate fossils are from the late Devonian.
		Glacial tillites and other geological evidence of late Permian age occur in Australia, Siberia and in the North Sea are interpreted as proof of the existence of large continental glaciers at the close of the Permian.
	www.emc.maricopa.edu /faculty/farabee/BIOBK/BioBookPaleo4.html (6474 words)

	Mass Extinction (Site not responding. Last check: 2007-11-03)
		The mass extinction at the end of the Permian period (245 MYA) was the largest extinction event in the Earth's history.
		The extinction at the boundary of the Cretaceous and the Tertiary periods, 65 million years ago, is the most famous of all mass extinctions.
		Glaciation: Most of the extinctions in the last 2.5 million years are associated with changes in climate resulting from glaciation where ice sheets covered a significant proportion of the earth’s surface.
	www.owlnet.rice.edu /~sehh/Dino/Mass_Extinction/extinct_history.htm (744 words)

	Devonian Summary
		Then, in the Devonian, came the fish, which developed jaws and were such successful competitors that the Agnathans were reduced almost to extinction, with only the lampreys and hagfish as their descendants.
		The Early Devonian Epoch is the most ancient, followed in sequence by the Middle Devonian Epoch, and the Late Devonian Epoch.
		The continent Euramerica (or Laurussia) was created in the early Devonian by the collision of Laurentia and Baltica, which rotated into the natural dry zone along the Tropic of Cancer, which is formed as much in Paleozoic times as nowadays by the convergence of two great airmasses, the Hadley cell and the Ferrel cell.
	www.bookrags.com /Devonian (2087 words)

	Late Devonian extinction - Wikipedia, the free encyclopedia
		The Late Devonian extinction was one of five major extinction events in the history of the Earth's biota.
		The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef-systems, including the stromatoporoids, and the rugose and tabulate corals.
		The late Devonian crash in biodiversity was more drastic than the familiar extinction event that closed the Cretaceous: a recent survey (McGhee 1996) estimates that 22 percent of all the families of marine animals (largely invertebrates) were eliminated, the category of families offering a broad range of real structural diversity.
	en.wikipedia.org /wiki/Late_Devonian_extinction (824 words)

	American Scientist Online - Planetary Realignment (Site not responding. Last check: 2007-11-03)
		The end-Permian mass extinction (the most severe in the history of life) and its dramatic impact are considered in an earlier volume of Columbia University Press's Critical Moments in Paleobiology series.
		Employing our current map of the Late Devonian world, McGhee identifies five ecological signals in the extinction data: global scope, greater extinction in equatorial regions, latitudinal compression of the ranges of low-latitude survivors, higher extinction in shallow-water marine environments, and more severe losses in marine than freshwater environments.
		Although explanations invoking multiple causes may be much harder to test, I would have appreciated an explicit consideration of the possibility that the severity of the Late Devonian extinction stems from the simultaneous or sequential effects of independent factors.
	www.americanscientist.org /template/BookReviewTypeDetail/assetid/28695 (992 words)

	UC Davis Geology: GEL 107 Paleobiology
		Extinction is local if a species disappears from part of its range; if all populations disappear, extinction is said to be global.
		Extinction occurs because all individuals are killed or because all reproduction fails.
		For extinctions caused by or associated with a reduction in primary productivity, high-energy species (those with a high metabolic rate) and species of large body size are at risk, as are single-celled species that have no way to store food or energy.
	www.geology.ucdavis.edu /~gel107/w05_vermeij/extinction.html (430 words)

	Dinosaur Extinction - Enchanted Learning Software
		The extinctions are clustered in a short amount of geological time (a few million years is very short in terms of geological time).
		The nemesis hypothesis of Raup and Sepkoski theorizes that there is a periodicity of 26 million years to mass extinctions which is caused by collisions with comets from the Oort cloud as they are perturbed in their orbits by a dark star (a companion star to the sun).
		The other dinosaur species died out during the several mass extinctions that occurred in the Mesozoic: at the end of the Triassic (213 million years ago), during and at the end of the Jurassic (at 190, 160, 144 mya), and during and at the end of the Cretaceous (at 120, 82, and 65 mya).
	www.enchantedlearning.com /subjects/dinosaurs/extinction/index.html (602 words)

	NAPC Abstracts, Ph - Py
		Devonian fossil concentrations are generally polytaxic but dominated by brachiopods, while Mississippian fossil concentrations are typically monotaxic (i.e., separate crinoidal, gastropod, and rugose coral fossil concentrations) and dominated by crinoidal fossil concentrations; the number of brachiopod concentrations decreases considerably.
		These results, coupled with the loss of large-scale reefs at the Devonian extinction, thought to be largely a result of the loss of stromatoporoids (Scrutton, 1988), point to the importance of retaining keystone and dominant taxa in maintaining ecosystem integrity.
		The late Miocene Roblar Tuff occurs at Steinbeck Ranch in the southern part of the outcrop area, whereas the occurrence of the bivalve mollusks Macoma addicotti (Nikas) and Nuttallia jamesii Roth and Naidu suggest a late Pliocene age for the northern outcrops at River Road.
	www.ucmp.berkeley.edu /napc/abs19.html (3692 words)

	The Extinction Cycle Moon Hypothesis
		The largest mass extinction to have affected life on Earth was the Permian-Triassic one that ended the Permian period 250 million years ago and killed off 90% of all species.
		The last such mass extinction led to the demise of the dinosaurs and has been found to have coincided with a large asteroid impact; this is the Cretaceous-Tertiary (K-T) extinction event.
		This would be the final piece of evidence that convinced the vast majority of scientists that this extinction resulted from a point event that is most probably an extra-terrestrial impact and not from increased volcanism and climate change (which would spread its main effect over a much longer time period).
	karinahall.txc.net.au /MoonExtinctionCycle (978 words)

	Open Directory - Science: Earth Sciences: Paleontology: Extinction (Site not responding. Last check: 2007-11-03)
		Extinction - A number of extinction concepts are discussed and loosely defined, followed by a survey of some important extinction and "extinction-like" events, primarily from the Phanerozoic.
		Extinctions: Cycles of Life and Death Through Time - Covers patterns and periodicity of extinction, with discussions of major mass extinctions and minor extinction events.
		The Late Devonian Mass Extinction - A professional technical paper discussing whether the Late Devonian (Frasnian-Famennian) mass extinction was initiated by an extraterrestrial impact or an earth-bound event.
	dmoz.org /Science/Earth_Sciences/Paleontology/Extinction (137 words)

	Devonian Period
		The adaptive radiation of Devonian fishes was probably the result of endemism, as lower water levels at beginning of Devonian isolated continental oceans and seas
		The evolution of tetrapods is closely linked to the rise of Devonian vascular plants, as the evolution of shrubbery and forests with deeper roots is though to have stabilized stream banks and provided more stable habitat for tetrapods to colonize
		Mass extinction of marine taxa occurs near the border of the Frasnian / Famennian stages of the Late Devonian epoch
	www.denison.edu /biology/faculty/firooznia/plant/devonian.html.org (817 words)

	WHAT IS AN EXTINCTION (Site not responding. Last check: 2007-11-03)
		Extinction is the process in which groups of organisms die out.
		Extinction is a natural phenomenon predicted by Darwin in his theory of evolution.
		These are the mass extinctions, they cause a dramatic decrease in the earth's biodiversity, and punctuate the earth's history, and are used by Geologists to break up geological time.
	palaeo.gly.bris.ac.uk /Palaeofiles/Triassic/extinction.htm (290 words)

	Devonian Times - The First Forests
		Terrestrial vegetation of the Silurian and Early Devonian was typically short and restricted to a narrow band along the water's edge.
		The widespread deposition of fl marine shales during the late Middle Devonian (Givetian) and Late Devonian has been attributed to a dramatic increase in the influx of terrestrial organic matter.
		Another striking characteristic of the Late Devonian forests is the apparent disappearance of the forest biome following the extinction of Archaeopteris near the end of the Devonian.
	www.devoniantimes.org /opportunity/forests.html (1185 words)

	Evolution: Change: Deep Time
		Intense reef building activity in shallow-water habitats indicates that the Devonian climate is, on the whole, warm and stable.
		During the Devonian period, survivors from the late Ordovician extinction steadily recover.
		For example, many shallow-water and reef-dwelling species probably died off in the Devonian because they (or their habitats) were more sensitive to changes in ocean chemistry or temperature than surviving animals that lived in deeper waters.
	www.pbs.org /wgbh/evolution/change/deeptime/devonian.html (903 words)

	dinosaur
		The extinction of the Dinosaurs 65 milllion years ago has not been the only large extinction in earths history.
		One of the Geological markers for the extinction of dinosaurs is the K-T (cretaceous (K) and tertiary (T)boundary).
		A possible causal relationship between extinction of dinosaurs and K/T iridium enrichment in the Nanxiong Basin, South China; evidence from dinosaur eggshells, Zhao Zikui In: Palaeogeography, Palaeoclimatology, Palaeoecology, January 01, 2002, Vol.
	www.earlham.edu /~smithan/dinosaur.htm (363 words)

	Oceanography: Changes during the Late Devonian Mass Extinction (Site not responding. Last check: 2007-11-03)
		The Late Devonian mass extinction witnessed the collapse of several ecosystems, including reefs and the planktonic food chain.
		The timing of the changes is being compared with the fossil record of the tentaculitids, an abundant group of planktonic microfossils, that disappeared druing the crisis.
		In addition, the broad spectrum of palaeoenvrionments recorded in the reef-to-basin centre sections of the Holy Cross Mountains (Poland) and the inner ramp-to-outer ramp and basin settings of the foreland basin of eastern Nevada are also under investigation.
	www.palaeobiology.org.uk /projects_06.htm (212 words)

	Late Devonian Mass Extinction, Educational Resources for K-16 (Site not responding. Last check: 2007-11-03)
		short explanation of mass extinctions, their cause and effect, and a discussion of the Late Devonian extinction.
		Short outline of the Late Devonian extinction, with pictures and graphs of the marine invertebrates that were affected and paleogeographic maps showing where glaciers were.
		Short summary of the Late Devonian extinction, with emphasis on the "Devonian Plant Hypothesis." This theory infers that the evolution and expansion of terrestrial vegetation led to changes in geochemical cycles that caused the mass extinction.
	www.uky.edu /KGS/education/LateDevonianMassExtinction.htm (148 words)

	Geotimes -- August 2000: Web extra 8/28/00
		A meteor impact may have caused the Late Devonian extinction, one of the longest lasting in history, but scientists have also implicated global warming, global cooling, sea level change and oxygen depletion.
		The three-million-year long event, known as the Frasnian-Fammenian extinction, decimated low-latitude tropical reef ecosystems and shallow-water marine faunas during the Middle Devonian to Late Devonian period.
		According to their new model of ocean circulation, Sageman says, during the late Devonian period this process could have resulted in the excess burial of carbon seen at the Kellwasser Horizons and at a series of fl shales leading up to them.
	www.geotimes.org /sept00/massex.html (627 words)

	Causes of the Devonian Extinction (Site not responding. Last check: 2007-11-03)
		Evidence supporting the Devonian mass extinction suggests that warm water marine species were the most severely affected in this extinction event.
		This evidence has lead many paleontologists to attribute the Devonian extinction to an episode of global cooling, similar to the event which is thought to have cause the late Ordovician mass extinction.
		Currently, the data surrounding a possible extra-terrestrial impact remains inconclusive, and the mechanisms which produced the Devonian mass extinction are still under debate.
	hannover.park.org /Canada/Museum/extinction/devcause.html (144 words)

	Ecological effects of paleo
		The extinction of the late Ordovician was one of the five largest extinctions on marine life.
		the severity of an extinction is not a function of the number of species lost but their ecological importance.
		This new model of mass extinctions, has not only provided a new way to analyze paleo-extinctions, but has also provided a model of what will happen in the extinction events which are occurring at present.
	palaeo.gly.bris.ac.uk /palaeofiles/triassic/ecoeffects.htm (351 words)

	David Bond
		The team possesses expertise in palaeontology, stable isotope geochemistry, palaeobotany, and palaeomagnetism, and together we aim to test the hypothesis that the Emeishan basalt eruptions precisely coincide with the onset of marine dysoxia and mass extinction due to a chain of cause-and-effects driven by volcanic CO2 release.
		My project was titled "Oceanographic changes during the Late Devonian mass extinction" and was a synthesis of faunal and geochemical data across the Frasnian-Famennian boundary, which records one of the "big 5" mass extinctions during the Phanerozoic.
		I concluded that the globally synchronous marine anoxia during the latest Frasnian was a key factor in the extinction scenario.
	earth.leeds.ac.uk /~eardpgb (591 words)

	GEOS301 Study Guide Chapter 6 Extinction (Site not responding. Last check: 2007-11-03)
		Summarize the early history of thought regarding the concept of extinction of organisms.
		Beside the specific taxa that were affected, explain how the Late Devonian extinction differs from the Permo-Triassic and the K-T events.
		Explain how the Late Ordovician extinction event was similar to the Permo-Triassic and Late Devonian events.
	www.lhup.edu /jway/301/301sg.6.htm (367 words)

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