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[[File:Elephant near ndutu.jpg|thumb|right|El [[elefante africano]], el animal terrestre vivo más grande]]
{{referencias}}
En zoología terrestre, el término '''megafauna''' (del [[griego antiguo]] ''megas'' "grande" + el [[latín]] ''fauna'' "animal") se refiere a animales "gigantes", "muy grandes" o "grandes". El umbral más comúnmente usado es 44 kilogramos<ref name = "Stuart">{{Cite journal
| last = Stuart | first = A. J. | authorlink = | title = Mammalian extinctions in the Late Pleistocene of northern Eurasia and North America | journal = [[Biological Reviews]] | volume = 66 | issue = 4 | pages = 453–562 | publisher = [[John Wiley & Sons|Wiley]] | date = 1991-11 | doi = 10.1111/j.1469-185X.1991.tb01149.x}}</ref><ref name = "Johnson">{{Cite journal | last = Johnson | first = C. N. | authorlink = | title = Determinants of Loss of Mammal Species during the Late Quaternary 'Megafauna' Extinctions: Life History and Ecology, but Not Body Size | journal = [[Proceedings of the Royal Society of London B]] | volume = 269 | issue = 1506 | pages = 2221–2227 (see p. 2225) | publisher = [[The Royal Society]] | date = 2002-09-23 | jstor = 3558643 | doi = 10.1098/rspb.2002.2130}}</ref> o 100 kilogramos.<ref name = "Johnson"/><ref name = "islands&continents">{{Cita publicación | last = Martin | first = P. S. | author-link = Paul S. Martin | last2 = Steadman | first2 = D. W. | author2-link = David Steadman | editor-last = MacPhee | editor-first = R. D. E | title = Extinctions in near time: causes, contexts and consequences
| place = New York | publisher = Kluwer/Plenum | series = Advances in Vertebrate Paleontology | volume = 2 | date = 1999-06-30 | chapter = Prehistoric extinctions on islands and continents
| chapterurl = http://google.com/books?id=UZLuF1YXYTcC&pg=PA17 | pages = 17–56 | url = http://www.google.com/books?id=UZLuF1YXYTcC&printsec=frontcover | doi = | isbn = 978-0-306-46092-0 | oclc = 41368299 | accessdate = 2011-08-23 | postscript =.}}</ref> Por lo tanto esto incluye a muchas especies que no son popurlarmente consideradas como especialmente grandes, como el [[ciervo de cola blanca]] y el [[canguro rojo]], y con el límite menor, incluso a los [[humano]]s.


En la práctica el uso más común encontrado en los escritos académicos y de divulgación describe a animales terrestres que son mayores que un ser humano los cuales no están (solamente) domesticados. El término es especialmente asociado con la megafauna del [[Pleistoceno]] — los animales grandes o gigantescos que se consideran arquetípicos de la [[Pleistocene glaciation|última era de hielo]] como los [[mamut]]es.<ref>[http://www.museum.state.il.us/exhibits/larson/ice_age_animals.html# Ice Age Animals]. Illinois State Museum</ref> Es también usado comúnmente para los mayores animales salvajes existentes, especialmente [[elefante]]s, [[jirafa]]s, [[hipopótamo]]s, [[rinoceronte]]s, [[alce]]s, [[cóndor]]es, etc. La megafauna puede ser subcategorizada por su posición [[Trophic species|trófica]] en megaherbívoros (por ej. [[ciervo]]s), megacarnívoros ([[leones]]), y más raramente, megaomnívoros ([[oso]]s).
[[Imagen:Mammouth.png|right|thumb|El [[mamut]], un animal extinto de tipo megafauna.]]

'''Megafauna''' (del griego ''mega'', "grande") es un término que se usa en [[paleontología]] para designar a los grandes [[animales]] terrestres extintos que vivieron a partir del final del [[Cretácico]]; en el periodo posterior a la extinción de los dinosaurios.
Otros usos comunes son para especies gigantes acuáticas, especialmente [[ballena]]s, cualquier animal terrestre salvaje o domesticado como los mayores [[antílope]]s y los [[toro]]s, y los [[dinosaurio]]s y otros reptiles gigantes extintos.

El término es a veces aplicado a animales (usualmente [[extinto]]s) de gran tamaño ''parientes de'' u tipo de animal más común o sobreviviente, por ejemplo las [[libélula]]s de 1 metro de envergadura del período [[Carbonífero]].

<!-- ==Ecological strategy==

Megafauna — in the sense of the largest mammals and birds — are generally [[R/K selection theory|K-strategist]]s, with great longevity, slow population growth rates, low death rates, and few or no natural predators capable of killing adults. These characteristics, although not exclusive to such megafauna, make them highly vulnerable to human [[overexploitation]].

==Evolution of large body size==

One observation that has been made about the evolution of larger body size is that rapid rates of increase that are often seen over relatively short time intervals are not sustainable over much longer time periods. In an examination of mammal body mass changes over time, the maximum increase possible in a given time interval was found to scale with the interval length raised to the 0.25 power.<ref name = "Evans"/> This is thought to reflect the emergence, during a trend of increasing maximum body size, of a series of anatomical, physiological, environmental, genetic and other constraints that must be overcome by evolutionary innovations before further size increases are possible. A strikingly faster rate of change was found for large decreases in body mass, such as may be associated with the phenomenon of [[insular dwarfism]]. When normalized to generation length, the maximum rate of large body mass decreases was found to be over 30 times greater than the maximum rate for large body mass increases.<ref name = "Evans"/>

===In terrestrial mammals===

Subsequent to the [[Cretaceous–Tertiary extinction event|K-T extinction event]] that eliminated the dinosaurs about 65.5 [[Megaannum|Ma]] ago, terrestrial mammals underwent a nearly exponential increase in body size as they diversified to occupy the ecological niches left vacant.<ref name = "F.A.Smith">{{cite journal
| last = Smith | first = F. A. | authorlink =
| coauthors = Boyer, A. G.; Brown, J. H.; Costa, D. P.; Dayan, T.; Ernest, S. K. M.; Evans, A. R.; Fortelius, M.; Gittleman, J. L.; Hamilton, M. J.; Harding, L. E.; Lintulaakso, K.; Lyons, S. K.; McCain, C.; Okie, J. G.; Saarinen, J. J.; Sibly, R. M.; Stephens, P. R.; Theodor, J.; Uhen, M. D.
| title = The Evolution of Maximum Body Size of Terrestrial Mammals
| journal = [[Science (journal)|Science]]
| volume = 330 | issue = 6008
| pages = 1216–1219 | publisher = | location =
| date = 2010-11-26 | language =
| url = http://www.sciencemag.org/content/330/6008/1216.short
| doi = 10.1126/science.1194830 | accessdate = 2012-01-07}}</ref> Starting from just a few kg before the event, maximum size had reached ~50 kg a few million years later, and ~750 kg by the end of the [[Paleocene]]. This trend of increasing body mass appears to level off about 40 Ma ago (in the late [[Eocene]]), suggesting that physiological or ecological constraints had been reached, after an increase in body mass of over three orders of magnitude.<ref name = "F.A.Smith"/> However, when considered from the standpoint of rate of size increase per generation, the exponential increase is found to have continued until the appearance of ''[[Indricotherium]]'' 30 Ma ago. (Since generation time scales with ''body mass''<sup>0.259</sup>, increasing generation times with increasing size cause the log mass vs. time plot to curve downward from a linear fit.)<ref name = "Evans">{{cite journal
| last = Evans | first = A. R. | authorlink = | coauthors = ''et al.''
| title = The maximum rate of mammal evolution
| journal = [[Proceedings of the National Academy of Sciences|PNAS]]
| volume = 109 | issue = | pages =
| publisher = | location = | date = 2012-01-30 | language =
| url = http://www.pnas.org/content/early/2012/01/26/1120774109.abstract
| doi = 10.1073/pnas.1120774109
| id = | accessdate = 2011-02-11}}</ref>

Megaherbivores eventually attained a body mass of over 10 000 kg. The largest of these, [[indricothere]]s and [[proboscid]]s, have been [[hindgut fermentation|hindgut fermenter]]s, which are believed to have an advantage over [[Foregut fermentation|foregut fermenter]]s in terms of being able to accelerate gastrointestinal transit in order to accommodate very large food intakes.<ref name = "Clauss">{{cite journal
| last = Clauss | first = M. | authorlink =
| coauthors = Frey, R.; Kiefer, B.; Lechner-Doll, M.; Loehlein, W.; Polster, C.; Roessner, G. E.; Streich, W. J.
| title = The maximum attainable body size of herbivorous mammals: morphophysiological constraints on foregut, and adaptations of hindgut fermenters
| journal = [[Oecologia]] | volume = 136 | issue = 1 | pages = 14–27
| publisher = | location = | date = 2003-04-24 | language =
| url = http://www.springerlink.com/content/npxv6d9aarkaqjkh/
| jstor = | issn = | doi = 10.1007/s00442-003-1254-z
| accessdate = 2012-01-08}}</ref> A similar trend emerges when rates of increase of maximum body mass per generation for different mammalian [[clade]]s are compared (using rates averaged over [[macroevolution]]ary time scales). Among terrestrial mammals, the fastest rates of increase occurred in [[perissodactyl]]s, followed by [[rodent]]s and [[proboscid]]s,<ref name = "Evans"/> all of which are hindgut fermenters. The rate of increase for [[artiodactyl]]s was about a third that of perissodactyls. The rate for [[carnivora]]ns was slightly lower yet, while [[primate]]s, perhaps constrained by their [[arboreal]] habits, had the lowest rate among the mammalian groups studied.<ref name = "Evans"/>

Terrestrial mammalian carnivores from several [[eutheria]]n groups (the [[mesonychid]] ''[[Andrewsarchus]]'', the [[creodont]]s ''[[Megistotherium]]'' and ''[[Sarkastodon]]'', and the [[carnivora]]ns ''[[Amphicyon]]'' and ''[[Arctodus]]'') all reached a maximum size of about 1000 kg<ref name = "F.A.Smith"/> (''[[Arctotherium]]'' apparently actually got a bit larger). The largest known [[metatheria]]n carnivore, ''[[Proborhyaena]] gigantea'', apparently reached 600 kg, also close to this limit.<ref name = ""Sorkin"/> A similar theoretical maximum size for mammalian carnivores has been predicted based on the metabolic rate of mammals, the energetic cost of obtaining prey, and the maximum estimated rate coefficient of prey intake.<ref name = "Carbone">{{cite journal
| last = Carbone | first = C. | authorlink =
| coauthors = Teacher, A; Rowcliffe, J. M.
| title = The Costs of Carnivory | journal = [[PLoS Biology]]
| volume = 5 | issue = 2, e22 | pages = 363–368
| publisher = | location = | date = 2007-01-16 | language =
| url = http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0050022
| doi = 10.1371/journal.pbio.0050022
| accessdate = 2012-01-08 | pmid=17227145 | pmc=1769424}}</ref> It has also been suggested that maximum size for mammalian carnivores is constrained by the stress the [[humerus]] can withstand at top running speed.<ref name = ""Sorkin">{{Cite journal
| last = Sorkin | first = B. | authorlink =
| title = A biomechanical constraint on body mass in terrestrial mammalian predators
| journal = [[Lethaia]] | volume = 41 | issue = 4 | pages = 333–347
| publisher = | location = | date = 2008-04-10 | language =
| url = http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111/j.1502-3931.2007.00091.x
| doi = 10.1111/j.1502-3931.2007.00091.x | accessdate = 2011-08-02}}</ref>

Analysis of the variation of maximum body size over the last 40 Ma suggests that decreasing temperature and increasing continental land area are associated with increasing maximum body size. The former correlation would be consistent with [[Bergmann's rule]],<ref name = "Ashton">{{cite journal
| last = Ashton | first = K. G. | authorlink = | coauthors = Tracy, M. C.; de Queiroz, A.
| title = Is Bergmann’s Rule Valid for Mammals?
| journal = [[The American Naturalist]]
| volume = 156 | issue = 4 | pages = 390–415
| publisher = | location = | date = October 2000 | language =
| url = http://www.jstor.org/stable/10.1086/303400
| jstor = | doi = 10.1086/303400
| accessdate = 2012-01-07}}</ref> and might be related to the [[Thermoregulation|thermoregulatory]] advantage of large body mass in cool climates,<ref name = "F.A.Smith"/> better ability of larger organisms to cope with seasonality in food supply,<ref name = "Ashton"/> or other factors;<ref name = "Ashton"/> the latter correlation could be explainable in terms of range and resource limitations.<ref name = "F.A.Smith"/> However, the two parameters are interrelated (due to sea level drops accompanying increased glaciation), making the driver of the trends in maximum size more difficult to identify.<ref name = "F.A.Smith"/>

===In flightless birds===
During the Paleocene, because of the small initial size of all mammals, [[apex predator]] niches were often occupied by members of other classes, such as terrestrial [[crocodilian]]s (e.g. ''[[Pristichampsus]]''), large snakes (e.g. ''[[Titanoboa]]''), [[varanid lizard]]s, or flightless birds<ref name = "F.A.Smith"/> (e.g. ''[[Gastornis]]'' in Europe and North America, ''[[Paleopsilopterus]]'' in South America). In the northern continents, large predatory birds were displaced when large eutherian carnivores evolved. In isolated South America, the [[phorusrhacid]]s could not be outcompeted by the local metatherian [[Sparassodonta|sparassodont]]s and remained dominant until advanced eutherian predators arrived from North America (as part of the [[Great American Interchange]]) during the [[Pliocene]]. However, none of the largest predatory (''[[Brontornis]]''), possibly omnivorous (''[[Dromornis]]''<ref name = "Murray 2004">{{cite book
| last1 = Murray | first1 = Peter F.
| last2 = Vickers-Rich | first2 = Patricia
| year = 2004
| title = Magnificent Mihirungs: The Colossal Flightless Birds of the Australian Dreamtime
| url=http://google.com/books?id=-t6cQHdVEggC&pg=PA51
| publisher = Indiana University Press | pages = 51, 314
| isbn = 978-0-253-34282-9 | accessdate=7 January 2012
}}</ref>) or herbivorous (''[[Aepyornis]]'') flightless birds of the [[Cenozoic]] ever grew to masses much above 500 kg, and thus never attained the size of the largest mammalian carnivores, let alone that of the largest mammalian herbivores. It has been suggested that the increasing thickness of avian eggshells in proportion to egg mass with increasing egg size places an upper limit on the size of birds.<ref name = "Murray 2004b">{{cite book
| last1 = ''Ibid'' | url=http://google.com/books?id=-t6cQHdVEggC&pg=PA212
| title = p. 212}}</ref> The largest species of ''Dromornis'', ''D. stirtoni'', may have gone extinct after it attained the maximum avian body mass and was then outcompeted by marsupial [[diprotodon]]ts that evolved to sizes several times larger.<ref name = "Murray 2004c">{{cite book
| last1 = ''Ibid'' | url=http://google.com/books?id=-t6cQHdVEggC&pg=PA277
| title = p. 277}}</ref>

==Mass extinctions==

A well-known mass extinction of megafauna, the [[Holocene extinction]] (see also [[Quaternary extinction event]]), occurred at the end of the [[Last glacial period|last ice age glacial period]] (a.k.a. the [[Würm glaciation]]) and wiped out many giant ice age animals, such as [[woolly mammoth]]s, in the [[Americas]] and northern [[Eurasia]]. Various theories have attributed the wave of extinctions to [[Quaternary extinction event#Hunting hypothesis|human hunting]], [[Quaternary extinction event#Climate change hypothesis|climate change]], [[Quaternary extinction event#Hyperdisease hypothesis|disease]], a [[Younger Dryas event|putative extraterrestrial impact]], or other causes. However, [[Quaternary extinction event|this extinction pulse]] near the end of the [[Pleistocene]] was just one of a series of megafaunal extinction pulses that have occurred during the last 50,000 years over much of the Earth's surface, with [[Africa]] and southern [[Asia]] being largely spared. The latter areas did suffer a gradual attrition of megafauna, particularly of the slower-moving species (a class of vulnerable megafauna epitomized by [[giant tortoise]]s), over the last several million years.<ref name=corlett>{{Cite journal | last1 = Corlett | first1 = R. T. | year = 2006 | title = Megafaunal extinctions in tropical Asia | url = http://www.tropicalbio.org/pastissues/tn_v17_n3_Sept_2006.pdf | journal = Tropinet | volume = 17 | issue = 3| pages = 1–3 | accessdate = 2010-10-04}}</ref><ref name = "Edmeades">{{Cite web
| last = Edmeades | first = Baz | authorlink =
| title = Megafauna — First Victims of the Human-Caused Extinction
| work = | publisher = (internet-published book with Foreword by [[Paul S. Martin]]) | date =
| url = http://www.megafauna.com/ | doi = | accessdate = 2010-10-04}}</ref>

Outside the mainland of [[Afro-Eurasia]], these megafaunal extinctions followed a distinctive landmass-by-landmass pattern that closely parallels the spread of humans into previously uninhabited regions of the world, and which shows no correlation with climatic history (which can be visualized with plots over recent geological time periods of climate markers such as [[:Image:Five Myr Climate Change.png|marine oxygen isotopes]] or [[:Image:Atmospheric CO2 with glaciers cycles.gif|atmospheric carbon dioxide levels]]).<ref name = "Martin">{{cite book
| last = Martin | first = P. S. | authorlink = Paul S. Martin
| title = Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America
| publisher = [[University of California Press]] | year = 2005 | location =
| contribution = Chapter 6, Deadly Syncopation | pages = 118–128
| url = http://www.google.com/books?id=eThoCsL1hRAC&printsec=frontcover
| isbn = 0-520-23141-4}}</ref><ref name = "Burney">{{cite journal
| last = Burney | first = D. A. | authorlink =
| coauthors = Flannery, T. F.
| title = Fifty millennia of catastrophic extinctions after human contact
| journal = Trends in Ecology & Evolution | volume = 20 | issue = 7 | pages = 395–401
| publisher = [[Elsevier]] | date = July 2005
| url = http://www.anthropology.hawaii.edu/Fieldschools/Kauai/Publications/Publication%204.pdf
| doi = 10.1016/j.tree.2005.04.022 | accessdate = 2009-06-12 | pmid = 16701402}}</ref> [[Australia]] was struck first around 45,000 years ago,<ref name = "New Ages">{{Cite journal
| last = Roberts | first = R. G. | authorlink =
| coauthors = [[Tim Flannery|Flannery, T. F.]]; Ayliffe, L. K.; Yoshida, H.; Olley, J. M.; Prideaux, G. J.; Laslett, G. M.; Baynes, A.; Smith, M. A.; Jones, R.; Smith, B. L.
| title = New Ages for the Last Australian Megafauna: Continent-Wide Extinction About 46,000 Years Ago
| journal = [[Science (journal)|Science]] | volume = 292 | issue = 5523 | pages = 1888–1892
| publisher = | date = 2001-06-08 | url = http://www.uow.edu.au/content/groups/public/@web/@sci/@eesc/documents/doc/uow014698.pdf
| doi = 10.1126/science.1060264 | accessdate = 2011-08-26 | pmid=11397939}}</ref> followed by [[Tasmania]] about 41,000 years ago (after formation of a land bridge to Australia about 43,000 years ago),<ref name = "Diamond">{{Cite journal
| last = Diamond | first = Jared | authorlink = Jared Diamond
| title = Palaeontology: The last giant kangaroo
| journal = [[Nature (journal)|Nature]] | volume = 454 | issue = 7206| pages = 835–836
| publisher = | date = 2008-08-13 | url = http://www.nature.com/nature/journal/v454/n7206/full/454835a.html
| doi = 10.1038/454835a | mr = | zbl = | jfm = | accessdate = 2011-05-08 | pmid=18704074}}</ref><ref name = "Turney">{{Cite journal
| last = Turney | first = C. S. M. | authorlink =
| coauthors = [[Tim Flannery|Flannery, T. F.]]; Roberts, R. G.; ''et al.''
| title = Late-surviving megafauna in Tasmania, Australia, implicate human involvement in their extinction
| journal = [[Proceedings of the National Academy of Sciences|PNAS]] | volume = 105 | issue = 34 | pages = 12150–12153
| publisher = [[United States National Academy of Sciences|NAS]] | date = 2008-08-21 | url = http://www.pnas.org/content/early/2008/08/20/0801360105.abstract
| doi = 10.1073/pnas.0801360105 | accessdate = 2011-05-08 | pmid=18719103 | pmc=2527880}}</ref><ref name = "Lost Giants">{{Cite journal
| last = Roberts | first = R. | authorlink = | coauthors = Jacobs, Z.
| title = The Lost Giants of Tasmania | journal = [[Australasian Science]]
| volume = 29 | issue = 9 | pages = 14–17
| publisher = | date = 2008-10 | url = http://www.control.com.au/bi2008/299megafauna.pdf
| accessdate = 2011-08-26}}</ref> [[Japan]] apparently about 30,000 years ago,<ref name = "Norton">{{Cite journal
| last = Norton | first = C. J. | authorlink =
| coauthors = Kondo, Y.; Ono, A.; Zhang, Y.; Diab, M. C.
| title = The nature of megafaunal extinctions during the MIS 3–2 transition in Japan
| journal = [[Quaternary International]] | volume = 211 | issue = 1–2 | pages = 113–122
| publisher = | date = 2009-05-23 | url = http://www.sciencedirect.com/science/article/pii/S1040618209001451
| doi = 10.1016/j.quaint.2009.05.002
| accessdate = 2011-08-30}}</ref> [[North America]] 13,000 years ago, [[South America]] about 500 years later,<ref name = "Haynes">{{Cite book
| first = Gary | last = Haynes | editor-last = Haynes | editor-first = Gary
| contribution = Introduction to the Volume
| contribution-url = http://www.springerlink.com/content/w314m76738r91g35/?p=5af1eb7387d443a2b514b284c646efa7&pi=0
| title = American Megafaunal Extinctions at the End of the Pleistocene | year = 2009 | pages = 1–20
| publisher = [[Springer Science+Business Media|Springer]]
| url = http://www.springerlink.com/content/978-1-4020-8792-9
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| first = Stuart | last = Fiedel | editor-last = Haynes | editor-first = Gary
| contribution = Sudden Deaths: The Chronology of Terminal Pleistocene Megafaunal Extinction
| contribution-url = http://www.springerlink.com/content/l225628681672725/?p=5af1eb7387d443a2b514b284c646efa7&pi=1
| title = American Megafaunal Extinctions at the End of the Pleistocene | year = 2009 | pages = 21–37
| publisher = [[Springer Science+Business Media|Springer]]
| url = http://www.springerlink.com/content/978-1-4020-8792-9
| doi = 10.1007/978-1-4020-8793-6_2 | isbn = 978-1-4020-8792-9}}</ref> [[Prehistoric Cyprus|Cyprus]] 10,000 years ago,<ref name = "Simmons1">{{Cite book
| last = Simmons | first = A. H. | authorlink =
| title = Faunal extinction in an island society: pygmy hippopotamus hunters of Cyprus | publisher = [[Kluwer Academic/Plenum Publishers]]
| series = Interdisciplinary Contributions to Archaeology
| volume = | year = 1999 | location = | pages = 382 | url = http://google.com/books?id=hCwYwyEBXEAC&printsec=frontcover
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| last = Simmons | first = A. H. | authorlink = | coauthors = Mandel, R. D.
| title = Not Such a New Light: A Response to Ammerman and Noller | journal = [[World Archaeology]]
| volume = 39 | issue = 4 | pages = 475–482 | publisher = | date = 2007-12
| jstor = 40026143
| doi = 10.1080/00438240701676169}}</ref> the [[Antilles]] 6000 years ago,<ref name = "Steadman">{{cite journal
| last = Steadman | first = D. W. | authorlink = David Steadman
| coauthors = [[Paul S. Martin|Martin, P. S.]]; MacPhee, R. D. E.; Jull, A. J. T.; McDonald, H. G.; Woods, C. A.; Iturralde-Vinent, M.; Hodgins, G. W. L.
| title = Asynchronous extinction of late Quaternary sloths on continents and islands
| journal = [[Proceedings of the National Academy of Sciences|Proc. Natl. Acad. Sci. USA]]
| volume = 102 | issue = 33 | pages = 11763–11768
| publisher = [[United States National Academy of Sciences|National Academy of Sciences]]
| date = 2005-08-16| doi = 10.1073/pnas.0502777102| pmid = 16085711
| pmc = 1187974}}</ref> [[New Caledonia#Ecology|New Caledonia]]<ref name = "Anderson">{{Cite journal
| last = Anderson | first = A. | authorlink =
| coauthors = Sand, C.; Petchey, F.; Worthy, T. H.
| title = Faunal extinction and human habitation in New Caledonia: Initial results and implications of new research at the Pindai Caves
| journal = Journal of Pacific Archaeology | volume = 1 | issue = 1 | pages = 89–109
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| doi =}}</ref> and nearby islands<ref name = "White">{{Cite journal
| last = White | first = A. W. | authorlink =
| coauthors = Worthy, T. H.; Hawkins, S.; Bedford, S.; Spriggs, M.
| title = Megafaunal meiolaniid horned turtles survived until early human settlement in Vanuatu, Southwest Pacific
| journal = [[PNAS|Proc. Natl. Acad. Sci. USA]]
| volume = 107 | issue = 35 | pages = 15512–15516
| publisher = | date = 2010-08-16| doi = 10.1073/pnas.1005780107}}</ref> 3000 years ago, [[Madagascar]] 2000 years ago,<ref name = "Madagascar">{{Cite journal
| last = Burney | first = D. A. | authorlink =
| coauthors = Burney, L. P.; Godfrey, L. R.; Jungers, W. L.; Goodman, S. M.; Wright, H. T.; Jull. A. J. T.
| title = A chronology for late prehistoric Madagascar
| journal = [[Journal of Human Evolution]] | volume = 47 | issue = 1–2 | pages = 25–63
| publisher = | date = 2004-07 | url = http://www.sciencedirect.com/science/article/pii/S0047248404000843
| doi = 10.1016/j.jhevol.2004.05.005 | accessdate = 2011-08-30 | pmid=15288523}}</ref> [[New Zealand]] 700 years ago,<ref name = "Holdaway">{{cite journal
| last = Holdaway | first = R. N. | authorlink = | coauthors = Jacomb, C.
| date = 2000-03-24 | title = Rapid Extinction of the Moas (Aves: Dinornithiformes): Model, Test, and Implications
| journal = [[Science (journal)|Science]] | volume = 287 | issue = 5461 | pages = 2250–2254
| doi = 10.1126/science.287.5461.2250 | url = http://www.sciencemag.org/content/287/5461/2250
| accessdate = 2011-08-30 | pmid = 10731144 }}</ref> the [[Mascarene Islands|Mascarenes]] 400 years ago,<ref name = "Janoo">{{Cite journal
| last = Janoo | first = A. | authorlink =
| title = Discovery of isolated dodo bones (''Raphus cucullatus'' (L.), Aves, Columbiformes) from Mauritius cave shelters highlights human predation, with a comment on the status of the family Raphidae Wetmore, 1930
| journal = Annales de Paléontologie | volume = 91 | issue = 2 | pages = 167–180
| publisher = | date = 2005-04 | url = http://www.sciencedirect.com/science/article/pii/S0753396905000170
| doi = 10.1016/j.annpal.2004.12.002
| accessdate = 2011-08-30}}</ref> and the [[Commander Islands]] 250 years ago.<ref name = "Hydrodamalis">{{cite journal
| last = Anderson | first = P. K. | authorlink =
| title = Competition, Predation, and the Evolution and Extinction of Steller's Sea Cow, ''Hydrodamalis gigas''
| journal = Marine Mammal Science | volume = 11 | issue = 3 | pages = 391–394
| publisher = [[Society for Marine Mammalogy]] | date = 1995-07 | url = http://www3.interscience.wiley.com/journal/119963340/abstract
| doi = 10.1111/j.1748-7692.1995.tb00294.x
| accessdate = 2011-08-30}}</ref> Nearly all of the world's isolated islands could furnish similar examples of extinctions occurring shortly after the arrival of ''[[Homo sapiens]]'', though most of these islands, such as the [[Hawaiian Islands]], never had terrestrial megafauna, so their [[List of extinct animals of the Hawaiian Islands|extinct fauna]] were smaller.<ref name = "Martin"/><ref name = "Burney"/>

An analysis of ''[[Sporormiella]]'' fungal spores (which derive mainly from the dung of megaherbivores) in swamp sediment cores spanning the last 130,000 years from Lynch’s Crater in [[Queensland]], Australia showed that the megafauna virtually disappeared about 41,000 years ago, at a time when climate changes were minimal; the change was accompanied by an increase in charcoal, and was followed by a transition from rainforest to fire-tolerant [[sclerophyll]] vegetation. The high-resolution chronology of the changes supports the hypothesis that human hunting alone eliminated the megafauna, and that the subsequent change in flora was most likely a consequence of the elimination of browsers and an increase in fire.<ref name = "">{{cite web
| last = Biello | first = D. | authorlink =
| title = Big Kill, Not Big Chill, Finished Off Giant Kangaroos
| work = [http://www.scientificamerican.com/section.cfm?id=news Scientific American news]
| publisher = | date = 2012-03-22
| url = http://www.scientificamerican.com/article.cfm?id=hunters-killed-off-big-animals-australia
| format = | accessdate = 2012-03-25}}</ref><ref name = "McGlone">{{cite journal
| last = McGlone | first = M. | authorlink =
| title = The Hunters Did It
| journal = [[Science (journal)|Science]]
| volume = 335 | issue = 6075 | pages = 1452–1453
| publisher = | location = | date = 2012-03-23 | language =
| url = http://www.sciencemag.org/content/335/6075/1452.summary
| doi = 10.1126/science.1220176 | id =
| accessdate = 2012-03-25}}</ref><ref name = "Rule">{{cite journal
| last = Rule | first = S. | authorlink =
| coauthors = Brook, B. W.; Haberle, S. G.; Turney, C. S. M.; Kershaw, A. P.
| title = The Aftermath of Megafaunal Extinction: Ecosystem Transformation in Pleistocene Australia
| journal = [[Science (journal)|Science]]
| volume = 335 | issue = 6075 | pages = 1483–1486
| publisher = | location = | date = 2012-03-23 | language =
| url = http://www.sciencemag.org/content/335/6075/1483.abstract
| doi = 10.1126/science.1214261
| id = | accessdate = 2012-03-25}}</ref> The increase in fire lagged the disappearance of megafauna by about a century, and most likely resulted from accumulation of fuel once grazing stopped. Over the next several centuries grass increased; sclerophyll vegetation increased with a lag of another century, and a sclerophyll forest developed after about another thousand years.<ref name = "Rule"/> During two periods of climate change about 120 and 75 thousand years ago, sclerophyll vegetation had also increased at the site in response to a shift to cooler, drier conditions; neither of these episodes had a significant impact on megafaunal abundance.<ref name = "Rule"/>

Continuing human hunting and environmental disturbance has led to additional [[Holocene extinction#Ongoing Holocene extinction|megafaunal extinctions in the recent past]], and has created a [[IUCN Red List critically endangered species|serious danger of further extinctions]] in the near future (see examples below).

A number of other [[Extinction event|mass extinction]]s occurred earlier in Earth's geologic history, in which some or all of the megafauna of the time also died out. Famously, in the [[Cretaceous–Tertiary extinction event]] the dinosaurs and most other giant reptilians were eliminated. However, the earlier mass extinctions were more global and not so selective for megafauna; i.e., many species of other types, including plants, marine invertebrates<ref name = "Alroy">{{Cite journal
| last = Alroy | first = J. | authorlink =
| title = Dynamics of origination and extinction in the marine fossil record
| journal = [[Proceedings of the National Academy of Sciences of the United States of America|PNAS]]
| volume = 105 Suppl 1 | pages = 11536–11542 | date = 2008-08-12 | pmid = 18695240
| pmc = 2556405 | doi = 10.1073/pnas.0802597105 |bibcode = 2008PNAS..10511536A
| issue = Supplement_1 }}</ref> and plankton, went extinct as well. Thus, the earlier events must have been caused by more generalized types of disturbances to the [[biosphere]].

==Effect of megafaunal extinctions on methane emissions==

Many [[herbivores]] produce [[methane]] as a byproduct of [[foregut fermentation]] in digestion, and release it through belching. Large populations of herbivore megafauna have the potential to contribute greatly to the atmospheric concentration of methane, which is an important [[greenhouse gas]]. Today, around 20% of annual methane emissions come from livestock methane release. Recent studies have indicated that the extinction of megafaunal herbivores may have caused a reduction in [[atmospheric methane]]. This hypothesis is relatively new.<ref name = "Smith">{{Cite journal
| last = Smith | first = F. A. | authorlink = | coauthors = Elliot, S. M.; Lyons, S. K.
| title = Methane emissions from extinct megafauna
| journal = [[Nature Geoscience]] | volume = 3 | issue = 6| pages = 374–375
| publisher = [[Nature Publishing Group]] | date = 2010-05-23
| url = http://www.nature.com/ngeo/journal/v3/n6/full/ngeo877.html| doi = 10.1038/ngeo877 | accessdate = 2011-02-26}}</ref>

Several studies have examined the effect of elimination of megaherbivorous mammals on methane emissions. One study examined the methane emissions from the [[American bison|bison]] that occupied the [[Great Plains]] of North America before contact with European settlers. The study estimated that the removal of the bison caused a decrease of 2.2 Tg/yr. This is a proportionally large change for the time period.<ref name = "Kelliher">{{Cite journal
| last = Kelliher | first = F. M. | authorlink = | coauthors = Clark, H.
| title = Methane emissions from bison—An historic herd estimate for the North American Great Plains
| journal = [[Agricultural and Forest Meteorology]] | volume = 150 | issue = 3 | pages = 473–577
| publisher = | date = 2010-03-15 | url = | doi = 10.1016/j.agrformet.2009.11.019}}</ref>

Another study examined the change of methane concentration in the atmosphere at the end of the [[Pleistocene epoch]] after the extinction of megafauna in the Americas. After early humans migrated to the Americas ~13,000 [[Before Present|BP]], their hunting and other associated ecological impacts led to the extinction of many megafaunal species in the region. Calculations suggest that this extinction decreased methane production by ~9.6 Tg/yr. [[Ice core]] records support this hypothesis of rapid methane decrease during the time period. This suggests that the absence of megafaunal methane emissions may have contributed to the abrupt climatic cooling at the onset of the [[Younger Dryas]].<ref name = "Smith"/>

==Examples==
The following are some notable examples of animals often considered as megafauna (in the sense of the "large animal" definition). This list is not intended to be exhaustive:

*class [[Mammalia]]
**infraclass [[Metatheria]]
***order [[Diprotodontia]]
****The [[Red Kangaroo|red kangaroo]] (''Macropus rufus'') is the largest living [[Australia]]n mammal and [[marsupial]] at a weight of up to {{convert|85|kg|lb|abbr=on}}. However, its extinct relative, the [[Procoptodon|giant short-faced kangaroo]] ''Procoptodon goliah'' reached {{convert|230|kg|abbr=on}}, while extinct [[diprotodon]]ts attained the largest size of any marsupial in history, up to an estimated {{convert|2750|kg|abbr=on}}. The extinct [[Marsupial Lion|marsupial lion]] (''Thylacleo carnifex''), at up to 160&nbsp;kg (350&nbsp;lb) was much larger than any extant carnivorous marsupial.
**infraclass [[Eutheria]]
***superorder [[Afrotheria]]
****order [[Proboscidea]]
*****[[Elephants]] are the largest living land animals. They and their relatives arose in [[Africa]], but until recently had a nearly worldwide distribution. The [[African Bush Elephant|African bush elephant]] (''Loxodonta africana'') has a shoulder height of up to {{convert|4.3|m|ft|0|abbr=on}} and weighs up to 13 tons. Among recently extinct proboscideans, [[mammoth]]s (''Mammuthus'') were close relatives of elephants, while [[mastodon]]s (''Mammut'') were much more distantly related. The [[Mammuthus sungari|Songhua River mammoth]] (''M. sungari'') is estimated to have weighed 17 tonnes, making it the largest [[Proboscidea|proboscid]] and second largest land mammal after [[Indricotheriinae|indricotherines]].
****order [[Sirenia]]
*****The largest sirenian at up to 1500&nbsp;kg is the [[West Indian Manatee|West Indian manatee]] (''Trichechus manatus''). [[Steller's sea cow]] (''Hydrodamalis gigas'') was probably around five times as massive, but unfortunately was exterminated by humans within 27 years of its discovery off the remote [[Commander Islands]] in 1741. In prehistoric times this sea cow also lived along the coasts of northeastern [[Asia]] and northwestern [[North America]]; it was apparently eliminated from these more accessible locations by aboriginal hunters.
***superorder [[Xenarthra]]
****order [[Cingulata]]
*****The [[Glyptodontidae|glyptodonts]] were a group of large, heavily armored [[ankylosauria|ankylosaur]]-like [[xenarthra]]ns related to living [[armadillos]]. They originated in [[South America]], invaded North America during the [[Great American Interchange]], and went extinct at the end of the [[Pleistocene]] [[Series (stratigraphy)|epoch]].
****order [[Pilosa]]
*****[[Ground sloth]]s were another group of slow, terrestrial xenarthrans, related to modern [[sloth|tree sloth]]s. They had a similar history, although they reached North America earlier, and spread [[Megalonyx|farther north]]. The largest genera, ''[[Megatherium]]'' and ''[[Eremotherium]]'', reached sizes comparable to elephants.
***superorder [[Euarchontoglires]]
****order [[Primates]]
*****The largest living primate, at up to {{convert|266|kg|lb|abbr=on}}, is the [[gorilla]] (''[[Gorilla beringei]]'' and ''[[Gorilla gorilla]]'', with three of four subspecies being [[critically endangered]]). The extinct Malagasy [[sloth lemur]] ''[[Archaeoindris]]'' reached a similar size, while the extinct ''[[Gigantopithecus#Gigantopithecus blacki|Gigantopithecus blacki]]'' of [[Southeast Asia]] is believed to have been several times larger. Some populations of [[Archaic Homo sapiens|archaic ''Homo'']] were significantly larger than recent ''[[Homo sapiens]]''; for example, ''[[Homo heidelbergensis]]'' in southern Africa may have commonly reached {{convert|7|ft|m}} in height,<ref name = "Our_Story">{{Cite web
| last = Smith | first = Chris | authorlink = | coauthors = Burger, Lee
| title = Our Story: Human Ancestor Fossils
| work = [http://www.thenakedscientists.com/ The Naked Scientists]
| publisher = | date = November 2007
| url = http://www.thenakedscientists.com/HTML/content/interviews/interview/833/
| doi = | accessdate = 2011-02-19}}</ref><ref name = "Hawks">{{Cite web
| last = Hawks | first = John | authorlink = | title = Bringing down "Goliath"
| work = [http://johnhawks.net/weblog/ John Hawks weblog]
| publisher = | date = 2005-04-02
| url = http://johnhawks.net/weblog/fossils/middle/body_mass_2005.html
| doi = | accessdate = 2011-02-19}}</ref><ref name = "Ciochon">{{Cite book
| last = Ciochon | first = Russell L. | authorlink = | coauthors = Fleagle, John G.
| title = The human evolution source book | publisher = [[Pearson Prentice Hall]]
| year = 2006 | location = | pages = 699 (see p. 394)
| url = http://books.google.com/?id=1DyAAAAAMAAJ&dq=human+evolution+source+book+Russell+L.+Ciochon%2C+John+G.+Fleagle&q=These+estimates+agree+with+other+estimates+based+on+cranial+dimensions#search_anchor
| doi = | isbn = 978-0-13-032981-3}}</ref><ref name = "Grine">{{Cite journal
| last = Grine | first = F. E. | authorlink = | coauthors = Jumgers, W. L.; Tobias, P. V.; Pearson, O. M.
| title = Fossil ''Homo'' femur from Berg Aukas, northern Namibia
| journal = [[American Journal of Physical Anthropology]] | volume = 97 | issue = 2 | pages = 151–185
| publisher = | date = June 1995| doi = 10.1002/ajpa.1330970207 | pmid = 7653506}}</ref> while [[Neanderthal]]s were about 30% more massive.<ref name = "Kappelman">{{Cite journal
| last = Kappelman | first = John | authorlink = | title = They might be giants
| journal = [[Nature (journal)|Nature]] | volume = 387 | issue = 6629| pages = 126–127
| publisher = | date = 1997-05-08
| url = http://www.nature.com/nature/journal/v387/n6629/pdf/387126a0.pdf| doi = 10.1038/387126a0 | pmid = 9144276 | accessdate = 2011-02-19}}</ref>
****order [[Rodent]]ia
*****The extant [[capybara]] (''Hydrochoerus hydrochaeris'') of South America, the largest living rodent, weighs up to {{convert|65|kg|lb|abbr=on}}. Several recently extinct North American forms were larger: the capybara ''[[Neochoerus pinckneyi]]'' (another [[Neotropic ecozone|neotropic]] migrant) was about 40% heavier; the [[Giant Beaver|giant beaver]] (''Castoroides ohioensis'') was similar. The extinct [[Blunt-toothed Giant Hutia|blunt-toothed giant hutia]] (''Amblyrhiza inundata'') of several [[Caribbean]] islands may have been larger still. However, several million years ago South America harbored much more massive rodents. ''[[Phoberomys pattersoni]]'', known from a nearly full skeleton, probably reached {{convert|700|kg|lb|abbr=on}}. Fragmentary remains suggest that ''[[Josephoartigasia monesi]]'' grew to upwards of {{convert|1000|kg|lb|-2|abbr=on}}.
***superorder [[Laurasiatheria]]
****order [[Carnivora]]
*****Big cats include the [[tiger]] (''Panthera tigris'') and [[lion]] (''Panthera leo''). The largest subspecies, at up to 306&nbsp;kg, is the [[Siberian tiger]] (''P. tigris altaica''), in accord with [[Bergmann's rule]]. Members of ''[[Panthera]]'' are distinguished by [[morphology (biology)|morphological]] features which enable them to roar. Larger extinct felids include the [[American Lion|American lion]] (''Panthera leo atrox'') and the South American [[saber-toothed cat]] ''[[Smilodon populator]]''.
*****[[Bears]] are large carnivorans of the [[Caniformia|caniform suborder]]. The largest living forms are the [[polar bear]] (''Ursus maritimus''), with a body weight of up to {{convert|680|kg|lb|-2|abbr=on}}, and the similarly sized [[Kodiak Bear|Kodiak bear]] (''Ursus arctos middendorffi''), again consistent with Bergmann's rule. ''[[Arctotherium]] augustans'', an extinct [[short-faced bear]] from South America, was the largest predatory land mammal ever with an estimated average weight of 1,600&nbsp;kg (3,500&nbsp;lb).<ref name = "Soibelzon">{{Cite journal
| last = Soibelzon | first = L. H. | authorlink = | coauthors = Schubert, B. W.
| title = The Largest Known Bear, ''Arctotherium angustidens'', from the Early Pleistocene Pampean Region of Argentina: With a Discussion of Size and Diet Trends in Bears
| journal = [[Journal of Paleontology]] | volume = 85 | issue = 1 | pages = 69–75
| publisher = [[Paleontological Society]]
| date = 2011-01 | url = http://jpaleontol.geoscienceworld.org/cgi/content/abstract/85/1/69
| doi = 10.1666/10-037.1 | mr = | zbl = | jfm = | accessdate = 2011-06-01}}</ref>
*****[[Pinniped|Seals, sea lions, and walruses]] are amphibious marine carnivorans that evolved from bearlike ancestors. The [[Southern Elephant Seal|southern elephant seal]] (''Mirounga leonina'') of [[Antarctic]] and [[subantarctic]] waters is the largest carnivoran of all time, with bull males reaching a maximum length of {{convert|6|-|7|m|ft|0|abbr=on}} and maximum weight of 5,000 kilograms.
****order [[Perissodactyla]]
*****[[Tapir]]s are browsing animals, with a short prehensile snout and pig-like form that appears to have changed little in 20 million years. They inhabit [[tropical rainforest|tropical forests]] of Southeast Asia and South and Central America, and include the largest surviving land animals of the latter two regions. There are four species.
*****[[File:Megafauna1.jpg|thumb|Rhinoceros]][[Rhinoceros]]es are [[odd-toed ungulates]] with horns made of [[keratin]], the same type of [[protein]] composing hair. They are among the largest living land mammals after elephants (hippos attain a similar size). Three of five extant species are [[IUCN Red List critically endangered species (Animalia)#Rhinocerotidae|critically endangered]]. Their extinct [[central Asia]]n relatives the [[Indricotheriinae|indricotherines]] were the largest terrestrial mammals of all time.
****order [[Artiodactyla]] (or [[cladistics|cladistically]], [[Cetartiodactyla]])
*****[[Giraffes]] (''Giraffa camelopardalis'') are the tallest living land animals, reaching heights of up to nearly {{convert|6|m|ft|0|abbr=on}}.
*****[[Bovinae|Bovine ungulates]] include the largest surviving land animals of [[Europe]] and North America. The [[Wild water buffalo|water buffalo]] (''Bubalis arnee''), [[bison]] (''[[Bison bison]]'' and ''[[Wisent|B. bonasus]]''), and [[gaur]] (''Bos gaurus'') can all grow to weights of over {{convert|900|kg|lb|abbr=on}}.
*****The [[semiaquatic]] [[hippopotamus]] (''Hippopotamus amphibius'') is the heaviest living [[even-toed ungulate]]; it and the [[critically endangered species|critically endangered]] [[Pygmy Hippopotamus|pygmy hippo]] (''Choeropsis liberiensis'') are believed to be the [[Cetartiodactyla#Kin to hippos|closest extant relatives]] of cetaceans. Hippos are among the megafaunal species [[Hippopotamus#Aggression|most dangerous]] to humans.<ref name = "SI">{{cite web
| last = Swift | first = E. M. | authorlink =
| title = What Big Mouths They Have: Travelers in Africa who run afoul of hippos may not live to tell the tale
| work = [http://sportsillustrated.cnn.com/vault/ Sports Illustrated Vault]
| publisher = [[Time Inc.]] | date = 1997-11-17
| url = http://sportsillustrated.cnn.com/vault/article/magazine/MAG1011493/1/index.htm
| accessdate = 2011-11-16}}</ref>
****order [[Cetacea]] (or cladistically, Cetartiodactyla)
*****[[Cetacea|Whales, dolphins, and porpoises]] are marine mammals. The [[Blue Whale|blue whale]] (''Balaenoptera musculus'') is the largest [[baleen whale]] and the largest animal that has ever lived. The [[Sperm Whale|sperm whale]] (''Physeter macrocephalus'') is the largest [[toothed whale]], as well as the planet's loudest and [[Sperm Whale#Brain and senses|brainiest animal]] (with a [[brain]] about five times as massive as a [[human brain|human's]]). The [[killer whale]] (''Orcinus orca'') is the largest dolphin.
*class [[Aves]] ([[Phylogenetic nomenclature|phylogenetically]], a [[clade]] within [[Coelurosauria]], a [[taxon]] within the order Saurischia of the clade [[Sauropsida]]; see below)
**order [[Struthioniformes]]
***The [[ratite]]s are an ancient and diverse group of [[flightless bird]]s that are found on fragments of the former [[supercontinent]] [[Gondwana]]. The largest living bird, the [[Ostrich]] (''Struthio camelus'') was surpassed by the extinct ''[[Aepyornis]]'' of [[Madagascar]], the heaviest of the group, and the extinct [[Dinornis|giant moa]] (''Dinornis'') of [[New Zealand]], the tallest, growing to heights of {{convert|3.4|m|ft|0|abbr=on}}. The latter two are examples of [[island gigantism]].
**order [[Anseriformes]]
***Extinct [[Dromornithidae|dromornithid]]s of Australia such as ''[[Dromornis]]'' may have exceeded the largest ratites in size. (Due to its small size for a continent and its isolation, Australia is sometimes viewed as the [[Australia#Geography and climate|world's largest island]]; thus, these species could also be considered insular giants.)
*class [[Reptilia]] (or cladistically, Sauropsida)
**order [[Crocodilia]]
***[[Alligators]] and [[crocodiles]] are large semiaquatic reptiles, the largest of which, the [[Saltwater Crocodile|saltwater crocodile]] (''Crocodylus porosus''), can grow to a weight of {{convert|1360|kg|lb|-2|abbr=on}}. Crocodilians' distant ancestors and their kin, the [[Crurotarsi#Evolution|crurotarsans]], dominated the world in the late [[Triassic]], until the [[Triassic–Jurassic extinction event]] allowed dinosaurs to overtake them. They remained diverse during the later [[Mesozoic]], when [[Crocodyliformes|crocodyliforms]] such as ''[[Deinosuchus]]'' and ''[[Sarcosuchus]]'' reached lengths of 12 m. Similarly large crocodilians, such as ''[[Mourasuchus]]'' and ''[[Purussaurus]]'', were present as recently as the [[Miocene]] in South America.
**order [[Saurischia]]
***Saurischian [[dinosaur]]s of the [[Jurassic]] and [[Cretaceous]] include [[Sauropoda|sauropod]]s, the longest (at up to {{convert|40|m|ft|-1|abbr=on|disp=or}}) and most massive terrestrial animals known (''[[Argentinosaurus]]'' reached 80–100&nbsp;[[metric ton]]nes, or 90–110&nbsp;[[short ton|ton]]s), as well as [[Theropoda|theropod]]s, the largest terrestrial carnivores (''[[Spinosaurus]]'' grew to 7–9 tonnes).
**order [[Squamata]]
***While the largest extant [[lizard]], the [[Komodo dragon]] (''Varanus komodoensis''), another island giant, can reach {{convert|3|m|ft|0|abbr=on}} in length, its extinct Australian relative ''[[Megalania]]'' may have reached more than twice that size. These [[monitor lizard]]s' marine relatives, the [[mosasaur]]s, were [[apex predator]]s in late Cretaceous seas.
***The heaviest extant [[snake]] is considered to be the [[Eunectes murinus|green anaconda]] (''Eunectes murinus''), while the [[Python reticulatus|reticulated python]] (''Python reticulatus''), at up to 8.7 m or more, is considered the longest. An extinct Australian [[Pliocene]] species of ''[[Liasis]]'', the [[Bluff Downs Giant Python|Bluff Downs giant python]], reached 10 m, while the [[Paleocene]] ''[[Titanoboa]]'' of South America reached lengths of 12–15 m and an estimated weight of about 1135 kilograms (2500&nbsp;lb).
**order [[Testudines]]
***The largest turtle is the [[critically endangered]] marine [[leatherback turtle]] (''Dermochelys coriacea''), weighing up to {{convert|900|kg|lb|-2|abbr=on}}. It is distinguished from other [[sea turtle]]s by its lack of a [[bone|bony]] [[exoskeleton|shell]]. The most massive terrestrial chelonians are the [[giant tortoise]]s of the [[Galápagos Islands]] (''[[Chelonoidis nigra]]'') and [[Aldabra|Aldabra Atoll]] (''[[Aldabrachelys gigantea]]''), at up to {{convert|300|kg|lb|-1|abbr=on}}. These tortoises are the biggest survivors of an assortment of giant tortoise species that were widely present on continental landmasses<ref name = "Hansen">{{Cite journal
| last = Hansen | first = D. M. | authorlink =
| coauthors = Donlan, C. J.; Griffiths, C. J.; Campbell, K. J.
| title = Ecological history and latent conservation potential: large and giant tortoises as a model for taxon substitutions
| journal = [[Ecography (journal)|Ecography]] | volume = 33 | issue = 2 | pages = 272–284
| publisher = [[John Wiley & Sons|Wiley]] | date = April 2010
| url = http://www.advancedconservation.org/library/hansen_etal_2010.pdf| doi = 10.1111/j.1600-0587.2010.06305.x | accessdate = 2011-02-26}}</ref><ref name = "Cione">{{Cite journal
| last = Cione | first = A. L. | authorlink =
| coauthors = Tonni, E. P.; Soibelzon, L.
| title = The Broken Zig-Zag: Late Cenozoic large mammal and tortoise extinction in South America
| journal = Rev. Mus. Argentino Cienc. Nat., n.s. | volume = 5 | issue = 1 | pages = 1–19
| publisher = | year = 2003
| url = http://www.ege.fcen.uba.ar/materias/general/Broken_ZigZagMACN_5_1_19_.pdf
| issn = 1514-5158 | doi = | accessdate = 2011-02-06}}</ref> and additional islands<ref name = "Hansen"/> during the Pleistocene.
*class [[Amphibia]]
**order [[Temnospondyli]]
***The [[Permian]] temnospondyl ''[[Prionosuchus]]'', the largest amphibian known, reached 9 m in length and was an aquatic predator resembling a crocodilian. After the appearance of real crocodilians, temnospondyls such as ''[[Koolasuchus]]'' (5 m long) had retreated to the Antarctic region by the Cretaceous, before going extinct.
*class [[Actinopterygii]]
**order [[Tetraodontiformes]]
***The largest extant [[bony fish]] is the [[ocean sunfish]] (''Mola mola''), whose average adult weight is {{convert|1000|kg|lb|-2|abbr=on}}. While phylogenetically a "bony fish", its skeleton is primarily [[cartilage]] (which is lighter than [[bone]]). It has a disk-shaped body, and propels itself with its long, thin [[dorsal fin|dorsal]] and [[anal fin]]s; it feeds primarily on [[jellyfish]]. In these three respects (as well as in its size and diving habits), it resembles a leatherback turtle.
**order [[Acipenseriformes]]
***The [[critically endangered species|critically endangered]] [[Beluga (sturgeon)|beluga]] (European sturgeon, ''Huso huso'') at up to 1476&nbsp;kg (3250&nbsp;lb) is the largest [[sturgeon]] (which are also mostly cartilaginous) and is considered the largest [[anadromous]] fish.
**order [[Siluriformes]]
***The [[critically endangered species|critically endangered]] [[Mekong giant catfish]] (''Pangasianodon gigas''), at up to 293&nbsp;kg (646&nbsp;lb), is often viewed as the largest [[freshwater fish]].
*class [[Chondrichthyes]]
**order [[Lamniformes]]
***The largest living predatory fish, the [[great white shark]] (''Carcharodon carcharias''), reaches weights up to {{convert|2240|kg|lb|-1|abbr=on}}. Its extinct relative ''[[megalodon|C. megalodon]]'' (the disputed genus being either ''Carcharodon'' or ''Carcharocles'') was more than an [[order of magnitude]] larger, and is the largest predatory shark or fish of all time; it preyed on whales and other [[marine mammal]]s.
**order [[Orectolobiformes]]
***The largest extant [[shark]], [[Chondrichthyes|cartilaginous fish]], and [[fish]] overall is the [[whale shark]] (''Rhincodon typus''), which reaches weights in excess of 21.5 tonnes (47,000&nbsp;lb). Like baleen whales, it is a [[filter feeder]] and primarily consumes [[plankton]].
**order [[Rajiformes]]
***The [[manta ray]] (''Manta birostris'') is another filter feeder and the largest [[Batoidea|ray]], growing to up to 2300&nbsp;kg.
*class [[Cephalopoda]]
**order [[Teuthida]]
***A number of deep ocean creatures exhibit [[Deep-sea gigantism|abyssal gigantism]]. These include the [[giant squid]] (''Architeuthis'') and [[colossal squid]] (''Mesonychoteuthis hamiltoni''); both (although rarely seen) are believed to attain lengths of {{convert|12|m|ft|0|abbr=on}} or more. The latter is the world's largest [[invertebrate]], and has the largest [[eye]]s of any animal. Both are preyed upon by sperm whales.

==Gallery==
===Extinct ===
<gallery>
Image:Giantscorpion cp 185155.jpg | ''[[Jaekelopterus rhenaniae|Jaekelopterus]]'', a [[Devonian]] "[[Eurypterid|sea scorpion]]", was 2.5 m long, not including its [[raptorial]] [[chelicerae]].
Image:Dunkleosteus BW.jpg | ''[[Dunkleosteus]]'' was a {{convert|10|m|ft|0|abbr=on}} long toothless [[Armour (anatomy)|armored]] predatory Devonian [[Placodermi|placoderm]] [[prehistoric fish|fish]].
Image:Dimetr eryopsDB.jpg | Sail-backed [[pelycosaur]] ''[[Dimetrodon]]'' and [[Temnospondyli|temnospondyl]] ''[[Eryops]]'' from [[North America]]'s [[Permian]].
Image:Leedsi&Liopl DB.jpg | [[Pliosaur]] ''[[Liopleurodon]]'' (right) harassing the [[filter feeder]] fish ''[[Leedsichthys]]'' during the [[Jurassic]].
Image:Tyrannosaurus BW.jpg | ''[[Tyrannosaurus]]'' was a 12 m (40 ft) long [[theropod]] dinosaur, an [[apex predator]] of [[Laramidia|west North America]].
Image:Macronaria scrubbed enh.jpg | [[Macronaria]]n [[sauropoda|sauropods]]; from left, ''[[Camarasaurus]]'', ''[[Brachiosaurus]]'', ''[[Giraffatitan]]'', ''[[Euhelopus]]''.
Image:Paraceratherium bugtiense skull.jpg| [[Indricotheriinae|Indricotheres]], the land mammals closest to sauropods in size and lifestyle, were rhinos.
Image:Argentavis magnificens.JPG | The [[Late Miocene]] [[Teratornithidae|teratorn]] ''[[Argentavis]]'' of [[South America]] had an {{convert|8|m|ft|0|abbr=on}} wingspan.
Image:Megalodon scale1.png | ''[[Megalodon|C. megalodon]]'' with a [[whale shark]], [[great white shark]] and a human for scale.
Image:Deinotherium12.jpg | ''[[Deinotherium]]'' had downward-curving tusks and ranged widely over [[Afro-Eurasia]].
Image:Titanis07DB.jpg | ''[[Titanis|Titanis walleri]]'', the only [[Phorusrhacidae|terror bird]] known to have [[Great American Interchange|invaded]] North America, was 2.5 m (8 ft 2 in) tall.
Image:Diprotodon11122.jpg| Hippo-sized ''[[Diprotodon]]'' of [[Australia]], the largest [[marsupial]] of all time, went extinct 40,000 years ago.
Image:Varanus priscus Melbourne Museum.jpg|''[[Megalania]]'', a giant carnivorous [[goanna]] of Australia, might have grown to 7 metres long.
Image:Megatherum DB.jpg | Elephant-sized ''[[Megatherium]]'', from South America's [[Pleistocene]], was the largest [[ground sloth|sloth]].
Image:Toxodon skeleton in BA.JPG| ''[[Toxodon]]'', one of South America's largest and last [[Notoungulata|notoungulate]]s. It had a [[Mixotoxodon|relative]] in [[Mexico]].
Image:Panthera leo atrox Sergiodlarosa.jpg | [[American Lion|American lion]]s exceeded [[extant taxon|extant]] [[lion]]s in size and ranged over two continents until 10,000 [[Before Present|BP]].
Image:Woolly mammoth (Mammuthus primigenius) - Mauricio Antón.jpg| [[Woolly mammoth]]s vanished after humans invaded their habitat in [[Eurasia]] and N. America.<ref name = "Stuart"/>
Image:Giant Haasts eagle attacking New Zealand moa.jpg| [[Haast's Eagle]], the largest eagle known, attacking [[moa]] (which included the [[Dinornis|tallest bird]] known).
</gallery>

===Living===
<gallery>
Image:Bristol.zoo.western.lowland.gorilla.arp.jpg| The [[gorilla]] is the largest and one of the most [[IUCN Red List critically endangered species (Animalia)#Hominidae|endangered primates]] on the planet.
Image:Tiger in the snow at the Detroit Zoo March 2008 pic 2.jpg | [[Siberian tiger]]s are the biggest living [[Felidae|cat]]s, exemplifying [[Bergmann's rule]].
Image:Polar Bear 2004-11-15.jpg| [[Polar bear]]s, the largest [[bear]]s and [[semiaquatic]] carnivores, are [[Polar bear#Climate change|vulnerable]] to [[global warming]].
Image:Ostafrikanisches Spitzmaulnashorn.JPG| The [[critically endangered]] [[Black Rhinoceros|black rhinoceros]], up to {{convert|14|ft|m}} long, is [[Black Rhinoceros#Distribution|threatened]] by [[poaching]].
Image:Temee.jpg| Wild [[Bactrian Camel|Bactrian camel]]s are critically endangered. Their ancestors [[Camelid#Evolution|originated in North America]].
Image:Ovibos moschatus qtl3.jpg| Unlike woolly [[woolly rhinoceros|rhinos]] and [[woolly mammoth|mammoths]], [[muskox]]en narrowly survived the [[Quaternary extinction event|Quaternary extinctions]].<ref name = "Stuart"/>
Image:Nijlpaard.jpg | [[Hippopotamus|Hippo]]s, the heaviest and most aquatic [[even-toed ungulate]]s, are [[cetacea|whales]]' [[Cetartiodactyla#Kin to hippos|closest living relatives]].
Image:Image-Blue Whale and Hector Dolphine Colored.jpg|A [[filter feeder]] up to {{Convert|33|m|ft|abbr=on}} long, the [[blue whale]] is the [[largest organism|largest animal]] of all time.
Image:Killerwhales jumping.jpg| The [[killer whale|orca]], the largest [[dolphin]] and [[Pack hunter|pack predator]], is [[Killer whale#Intelligence|highly intelligent]] and lives in [[Killer whale#Social structure|complex societies]].
Image:Strauss m Tanzania.jpg| The [[Ostrich]] is the largest [[ratite]], the heaviest living [[bird]], and, at 70 km/h, the fastest running bird.
Image:SaltwaterCrocodile('Maximo').jpg| The [[Saltwater Crocodile|saltwater crocodile]] is the largest living [[reptile]] and a dangerous [[Crocodile attack|predator of humans]].
Image:Komodo dragon Varanus komodoensis Ragunan Zoo 2.JPG| The [[Komodo dragon]], an [[Island gigantism|insular giant]], is the largest [[lizard]] and has [[Komodo dragon#Saliva|infectious and venomous saliva]].
Image:Eunectes murinus2.jpg | The [[Eunectes murinus|green anaconda]], an aquatic [[Constriction|constrictor]], is the heaviest [[snake]], weighing up to {{convert|97.5|kg|lb|abbr=on}}.
Image:Mola-mola-Lisboa-20051020.jpg | The [[ocean sunfish#Range and behavior|deep-diving]] [[ocean sunfish]] is the largest [[Osteichthyes|bony fish]], but its skeleton is mostly [[Cartilage|cartilaginous]].
Image:Lates niloticus 2.jpg| The [[Nile perch]], one of the largest freshwater fish, as well as a damaging [[invasive species]].
Image:Male whale shark at Georgia Aquarium crop.jpg| The [[whale shark]] is the largest extant shark or fish species, growing up to {{Convert|12.6|m|ft|abbr=on}} in length.
Image:Manta birostris-Thailand.jpg| The [[manta ray|manta]], a filter feeder, is the largest [[Batoidea|ray]] at up to 7.6 m across, yet can [[Whale surfacing behaviour#Breaching, lunging, and porpoising|breach]] clear of the water.
Image:Giant squid Ranheim2.jpg|Examination of a 9 m [[giant squid]], an [[Deep-sea gigantism|abyssal giant]] and the second largest [[cephalopod]].
</gallery>

==See also==
{{div col|cols=2}}
*[[Australian megafauna]]
*[[Bergmann's rule]]
*[[Charismatic megafauna]]
*[[Cope's rule]]
*[[Deep-sea gigantism]]
*[[Fauna]]
*[[Giant animal (disambiguation)|Giant animal]]s in fiction and mythology
*[[Island dwarfism]]
*[[Island gigantism]]
*[[Largest organisms]]
*[[Largest prehistoric organisms]]
*[[List of megafauna discovered in modern times]]
*[[:Category:Megafauna|Megafauna (categories)]]
**[[:Category:Megafauna of Africa|Africa]]
**[[:Category:Megafauna of Australia|Australia]]
**[[:Category:Megafauna of Eurasia|Eurasia]]
**[[:Category:Megafauna of North America|North America]]
**[[:Category:Megafauna of South America|South America]]
*[[New World Pleistocene extinctions]]
*[[Pleistocene megafauna]]
*[[Quaternary extinction event]]
{{div col end}}
-->


==Causas de su surgimiento==
==Causas de su surgimiento==
Línea 61: Línea 513:
* [[Cambio climático|Cambios climáticos]]
* [[Cambio climático|Cambios climáticos]]


==Bibliografía==
==Referencias==

{{reflist|colwidth=30em}}

*Jared Diamond, 2006. ''Armas, gérmenes y acero''. Debate Editorial. ISBN 84-8306-667-X
*Jared Diamond, 2006. ''Armas, gérmenes y acero''. Debate Editorial. ISBN 84-8306-667-X
*[http://www.megafauna.com.ar Fósiles de Megafauna del Noroeste de la provincia de Buenos Aires]
*[http://www.megafauna.com.ar Fósiles de Megafauna del Noroeste de la provincia de Buenos Aires]

==Enlaces externos==
* [http://www.megafauna.com Megafauna – "First Victims of the Human-Caused Extinction"]{{en}}


[[Categoría:Fósiles del Cenozoico]]
[[Categoría:Fósiles del Cenozoico]]

Revisión del 09:09 25 abr 2012

El elefante africano, el animal terrestre vivo más grande

En zoología terrestre, el término megafauna (del griego antiguo megas "grande" + el latín fauna "animal") se refiere a animales "gigantes", "muy grandes" o "grandes". El umbral más comúnmente usado es 44 kilogramos[1]​[2]​ o 100 kilogramos.[2]​[3]​ Por lo tanto esto incluye a muchas especies que no son popurlarmente consideradas como especialmente grandes, como el ciervo de cola blanca y el canguro rojo, y con el límite menor, incluso a los humanos.

En la práctica el uso más común encontrado en los escritos académicos y de divulgación describe a animales terrestres que son mayores que un ser humano los cuales no están (solamente) domesticados. El término es especialmente asociado con la megafauna del Pleistoceno — los animales grandes o gigantescos que se consideran arquetípicos de la última era de hielo como los mamutes.[4]​ Es también usado comúnmente para los mayores animales salvajes existentes, especialmente elefantes, jirafas, hipopótamos, rinocerontes, alces, cóndores, etc. La megafauna puede ser subcategorizada por su posición trófica en megaherbívoros (por ej. ciervos), megacarnívoros (leones), y más raramente, megaomnívoros (osos).

Otros usos comunes son para especies gigantes acuáticas, especialmente ballenas, cualquier animal terrestre salvaje o domesticado como los mayores antílopes y los toros, y los dinosaurios y otros reptiles gigantes extintos.

El término es a veces aplicado a animales (usualmente extintos) de gran tamaño parientes de u tipo de animal más común o sobreviviente, por ejemplo las libélulas de 1 metro de envergadura del período Carbonífero.


Causas de su surgimiento

La extinción masiva del Cretácico-Terciario fue un periodo de extinciones masivas de especies ocurrido hace aproximadamente 65 millones de años, correspondiente al final del periodo Cretácico y el principio del periodo Terciario. Los doctores Luis Álvarez, geofísico, y su hijo Walter Álvarez, profesor de Geología de la Universidad de Berkeley, propusieron una teoría según la cual esta extinción masiva hace 65 millones de años pudo ser causada por la caída de un meteorito gigante. La liberación de energía en el impacto pudo crear una capa de polvo en la atmósfera superior, que ocasionó el bloqueo de la energía solar, generando una edad de hielo. Como evidencia de la caída de un meteorito, en la península de Yucatán, México, se han localizado cantidades anormalmente altas de iridio en estratos geológicos correspondientes a una profundidad localizada en esa era geológica.

En este periodo, la Tierra tomó su forma actual con la distribución de los continentes tal como hoy se conocen, tras la separación del supercontinente Pangea. Cerca del 50% de los géneros biológicos desaparecieron, entre ellos, la familia completa de los tres órdenes de los dinosaurios. Esta desaparición dejo vacío un nicho ecológico que fue llenado por otra megafauna, tras una recuperación de la biodiversidad del planeta durante millones de años.[cita requerida]

Animales que componían la megafauna

La lista de grandes animales extintos en esta época es inmensa, siendo los siguientes los más conocidos.

Causas de la extinción

Referencias

  1. ↑ Stuart, A. J. (1991-11). «Mammalian extinctions in the Late Pleistocene of northern Eurasia and North America». Biological Reviews (Wiley) 66 (4): 453-562. doi:10.1111/j.1469-185X.1991.tb01149.x. 
  2. ↑ a b Johnson, C. N. (23 de septiembre de 2002). «Determinants of Loss of Mammal Species during the Late Quaternary 'Megafauna' Extinctions: Life History and Ecology, but Not Body Size». Proceedings of the Royal Society of London B (The Royal Society) 269 (1506): 2221-2227 (see p. 2225). JSTOR 3558643. doi:10.1098/rspb.2002.2130. 
  3. ↑ Martin, P. S.; Steadman, D. W. (30 de junio de 1999). «Prehistoric extinctions on islands and continents». En MacPhee, R. D. E, ed. Extinctions in near time: causes, contexts and consequences. Advances in Vertebrate Paleontology 2. New York: Kluwer/Plenum. pp. 17-56. ISBN 978-0-306-46092-0. OCLC 41368299. Consultado el 23 de agosto de 2011. 
  4. ↑ Ice Age Animals. Illinois State Museum

Enlaces externos

Enlaces externos

Obtenido de «https://es.wikipedia.org/w/index.php?title=Megafauna&oldid=55661890»