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Encyclopedia > Late Devonian extinction
Comparison of the three episodes of extinction in the Late Devonian ("Late D") to other mass extinction events in Earth's history. Data based on marine genera.
Comparison of the three episodes of extinction in the Late Devonian ("Late D") to other mass extinction events in Earth's history. Data based on marine genera.

The Late Devonian extinction was one of five major extinction events in the history of the Earth's biota. A major extinction occurred at the boundary that marks the beginning of the last phase of the Devonian period, the Famennian faunal stage, (the Frasnian-Famennian boundary), about 364 million years ago, when all the fossil agnathan fishes suddenly disappeared. A second strong pulse closed the Devonian period. Image File history File links Description Total Phanerozoic biodiversity during the same interval. ... Image File history File links Description Total Phanerozoic biodiversity during the same interval. ... In biology, a genus (plural genera) is a grouping in the classification of living organisms having one or more related and morphologically similar species. ... An extinction event (also extinction-level event, ELE) occurs when a large number of species die out in a relatively short period of time. ... Disambiguation: Devonian is also an adjective relating to the English county of Devon or the people there. ... The Famennian Age is one of two ages in the Late Devonian Period. ... Faunal stages are a subdivision of geologic time used primarily by paleontologists who study fossils rather than by geologists who study rock formations. ... Groups Myxinoidea (hagfish) Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi Thelodonti Anaspida Cephalaspidomorphi Galeaspida Pituriaspida Osteostraci Agnatha (Greek, no jaws) is a paraphyletic superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. ...


Although it is clear that there was a massive loss of biodiversity towards the end of the Devonian, the extent of time during which these events took place is still mooted, with estimates as brief as 500 thousand years or as extended as 15 million, the full length of the Famennian. Nor is it clear whether it concerned two sharp mass extinctions or a cumulative sequence of several smaller extinctions, though the most recent research suggests multiple causes and a series of distinct extinction pulses through an interval of some three million years [1] [2].


Anoxic conditions in the sea-bed of late Devonian ocean basins produced some oil shales. The Devonian extinction crisis primarily affected the marine community, and selectively affected shallow warm-water organisms rather than cool-water organisms. 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 reef system collapse was so severe that major reef-building (effected by new families of carbonate-excreting organisms, the modern scleractinian corals) did not recover until the Mesozoic era. Tabulate Corals lived entirely during the Paleozoic. ...


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. Some 57 percent of the genera went extinct, and—the estimate most likely to be adjusted—at least 75 percent of the species did not survive into the following Carboniferous. The estimates of species loss depend on surveys of marine taxa that are perhaps not well enough known to assess their true rate of losses, and for the Devonian it is not easy to allow for possible effects of differential preservation and sampling biases. Amongst the severely affected marine groups were the brachiopods, trilobites, ammonites, conodonts, and acritarchs, as well as jawless fish, and all placoderms. Freshwater species, including our tetrapod ancestors, were less affected. Biodiversity or biological diversity is the diversity of and in living nature. ... The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65. ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... Invertebrate is a term coined by Jean-Baptiste Lamarck to describe any animal without a spinal column. ... In biology, a genus (plural genera) is a grouping in the classification of living organisms having one or more related and morphologically similar species. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... In general, a sample is a part of the total, such as one individual or a set of individuals from a population (of people or things), a small piece or amount of something larger, a number of function values of a function, or part of a song. ... Subphyla and classes See Classification Brachiopods (from Latin bracchium, arm + New Latin -poda, foot) make up one of the major animal phyla, Brachiopoda. ... Orders Agnostida Redlichiida Corynexochida Lichida Phacopida Proetida Asaphida Harpetida Ptychopariida doubtful order Nektaspida Trilobites are extinct arthropods in the class Trilobita. ... This article is about the marine animal. ... Conodonts are extinct worm-like forms with distinctive conical or multi-denticulate teeth made of apatite (calcium phosphate). ... Acritarchs are small organic structures found as fossils. ... Groups Myxinoidea (hagfish) Hyperoartia Petromyzontidae (lampreys) Pteraspidomorphi Thelodonti Anaspida Cephalaspidomorphi Galeaspida Pituriaspida Osteostraci Agnatha (Greek, no jaws) is a paraphyletic superclass of jawless fish in the phylum Chordata, subphylum Vertebrata. ... Orders Antiarchi † Arthrodira † Petalichthyda † Phyllolepida † Ptyctodontida † Rhenanida † The Placodermi are fish known from fossils dating to the Devonian period. ... Groups Amphibia Elginerpetontidae Acanthostegidae Ichthyostegidae Whatcheeriidae Crassigyrinidae Baphetidae Colosteidae (Batrachomorpha) Temnospondyli Lepospondyli Reptiliomorpha Amniota Sauropsida/Reptilia Aves (Birds) Synapsida Mammalia Tetrapods (Greek tetrapoda, four-legged) are the most successful body form; a vertebrate animal having four feet, legs or leglike appendages. ...


Reasons for the late Devonian extinctions are still speculative. Bolide impacts are dramatic triggers of mass extinctions. In 1969, Canadian paleontologist Digby McLaren suggested that an asteroid impact was the prime cause of this faunal turnover, supported by McGhee (1996), but no secure evidence of a specific extra-terrestrial impact has been identified in this case (yet see the Alamo bolide impact of Nevada). The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. ... To meet Wikipedias quality standards, this article or section may require cleanup. ...


The "greening" of the continents occurred during Devonian time: by the end of the Devonian, complex branch and root systems supported trees 30m/90 ft tall. (Carbon locked in Devonian coal, the earliest of Earth's coal deposits, is currently being returned to the atmosphere.) But the mass extinction at the Frasnian-Famennian boundary did not affect land plants. The covering of the planet's continents with photosynthesizing land plants may have reduced carbon dioxide levels in the atmosphere. Since CO2 is a greenhouse gas, reduced levels might have helped produce a chillier climate. A cause of the extinctions may have been an episode of global cooling, following the mild climate of the Devonian period. Evidence such as glacial deposits in northern Brazil (located near the Devonian south pole) suggest widespread glaciation at the end of the Devonian, as a large continental mass covered the polar region [3]. Massive glaciation tends to lower eustatic sea-levels, which may have exacerbated the late Devonian crisis. Because glaciation appears only toward the very end of the Devonian, it is more likely to be a result, rather than a cause of the drop in global temperatures. Leaf. ... Top: Increasing atmospheric CO2 levels as measured in the atmosphere and ice cores. ...


George R. McGhee Jr (1996) has detected among the survivors, some trends that lead to his conclusion that survivors generally represent more primitive or ancestral morphologies. In other words, the conservative generalists are more likely to survive an ecological crisis than species that have evolved as specialists.


External links

  • Devonian Mass Extinction
  • BBC "The Extinction files" "The Late Devonian Extinction"
  • "Understanding Late Devonian and Permian-Triassic Biotic and Climatic Events: Towards an Integrated Approach": a Geological Society of America conference in 2003 reflects current approaches
  • PBS: Deep Time

The Geological Society of America (or GSA) is a nonprofit organization dedicated to the advancement of the geosciences. ...

Further reading

  • McGhee, George R., Jr, 1996. The Late Devonian Mass Extinction: the Frasnian/Famennian Crisis (Columbia University Press) reviewed by Sherman J. Suter, Smithsonian.

  Results from FactBites:
 
extinction event: Information from Answers.com (3179 words)
The extinctions, however, did not conform to the usual evolutionary rules regarding who survives; the only factor that appears to have improved a family of organisms' chance of survival was widespread geographic colonization at the time of the event.
Though there were undoubtedly mass extinctions in the Archean and Proterozoic, it is only during the Phanerozoic Eon that the emergence of bones and shells in the evolutionary tree has provided a sufficient fossil record from which to make a systematic study of extinction patterns.
The K/T extinction was rather uneven, for example: all non-avian dinosaurs and all pterosaurs, plesiosaurs, mosasaurs and ammonites became extinct; marsupials, birds, plankton, teleosts, bivalves, snails, sponges, and sea urchins suffered heavy losses; but placental mammals, non-dinosaurian reptiles and amphibians appear to have got off relatively lightly.
Devonian (854 words)
The west coast of Devonian North America, by contrast, was a passive margin with deep silty embayments, river deltas and estuaries, in today's Idaho and Nevada; an approaching volcanic
By the Devonian Period, life was well underway in its colonization of the land.
The evolving co-dependence of insects and seed-plants that characterizes a recognizably modern world had its genesis in the late Devonian.
  More results at FactBites »

 
 

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