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K-Pg extinction event

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The Cretaceous-Paleogene extinction event (aka the Cretaceous-Tertiary extinction event, abbreviated as either the K-T extinction event or the K-Pg extinction event) was a major mass extinction event that took place around 66 million years ago, and lead to the deaths of a large number of organisms around the globe, including all of the dinosaurs (except birds).

Causes of the extinction[edit]

There may have ultimately been multiple different causes for the K-Pg extinction event, but what is widely agreed upon is that the major catalyst for the extinction was a 10–15 km asteroid or comet that hit the Yucatán peninsula, and formed the Chicxulub crater.Wikipedia's W.svg[1] Other causes may have included the Deccan TrapsWikipedia's W.svg[note 1][2] Strangely enough, the extinction ratios of clades affected by the extinction suggests that the extinction was ultimately due to the re-entry of ejecta into the atmosphere after the impact occurred.[3]

Woo[edit]

There is some woo regarding the causes of the K-Pg extinction event, with some people believing that the event was actually caused by something other than the asteroid impact, in general the evidence favors a combination of factors including the Deccan Traps and the impact, but the impact was definitely the main factor. Some people used to claim that dinosaurs were in decline long before the extinction event, with the asteroid impact being a coup de grace of sorts, but no evidence supports that position.

Extinction ratios[edit]

Freshwater biomes were in general less affected by the K-Pg extinction event than their terrestrial or marine counterparts, with amphibians in particular not being generally affected by the extinction event, with only a few extinctions among them.[4] Terrestrial organisms were hit hard however, with the extinction of every bird outside of Neornithes[5], all pterosaurs, all non-avian dinosaurs, entire clades of mammals (marsupials used to be the dominant mammals in North America, but after the K-Pg extinction event only a few marsupials remained, among them Peradectes, with the mammals above the K-Pg boundary layer that dominated North America being eutherians). The oceans were hit hard as well, with almost every marine reptile outside of sea turtles going extinct, not to mention the extinction of the ammonites[note 2].

Notes[edit]

  1. A period of flood basalt eruptions that were one of the largest eruptions in Earth's history
  2. Just like in 2 Samuel 12:26

References[edit]

  1. Hildebrand, A. R.; Penfield, G. T.; et al. (1991). "Chicxulub crater: a possible Cretaceous/Tertiary boundary impact crater on the Yucatán peninsula, Mexico". Geology. 19 (9): 867–871. Bibcode:1991Geo....19..867H. doi:10.1130/0091-7613(1991)019<0867:ccapct>2.3.co;2.
  2. Petersen Sierra V., Dutton Andrea, Lohmann Kyger C. (2016). "End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change". Nature Communications. 7: 12079. Bibcode:2016NatCo...712079P. doi:10.1038/ncomms12079.
  3. http://groups.google.com/forum/#!topic/sci.bio.paleontology/7RpgzUW6O3M
  4. Sheehan, P. M.; Fastovsky, D. E. (1992). "Major extinctions of land-dwelling vertebrates at the Cretaceous-Tertiary boundary, Eastern Montana". Geology. 20 (6): 556–560. Bibcode:1992Geo....20..556S. doi:10.1130/0091-7613(1992)020<0556:meoldv>2.3.co;2.
  5. Hou, L; Martin, M; Zhou, Z; Feduccia, A (1996). "Early Adaptive Radiation of Birds: Evidence from Fossils from Northeastern China". Science. 274 (5290): 1164–1167. Bibcode:1996Sci...274.1164H. doi:10.1126/science.274.5290.1164. PMID 8895459.