Editing Extinction (section)

==Definition==
[[File:LepidodendronOhio.jpg|thumb|right|External mold of the extinct ''[[Lepidodendron]]'' from the [[Upper Carboniferous]] of [[Ohio]]<ref>{{cite book |last1=Kenrick |first1=Paul |last2=Davis |first2=Paul |title=Fossil Plants |date=2004 |publisher=Smithsonian Books |isbn=978-0-565-09176-7}}{{page needed|date=February 2022}}</ref><ref>{{cite book |last1=Moran |first1=Robbin Craig |title=A Natural History of Ferns |date=2004 |publisher=Timber Press |isbn=978-0-88192-667-5}}{{page needed|date=February 2022}}</ref>]]
A species is extinct when the last existing member dies. Extinction therefore becomes a certainty when there are no surviving individuals that can reproduce and create a new generation. A species may become [[functional extinction|functionally extinct]] when only a handful of individuals survive, which cannot reproduce due to poor health, age, sparse distribution over a large range, a lack of individuals of both sexes (in [[sexual reproduction|sexually reproducing]] species), or other reasons.

Pinpointing the extinction (or [[pseudoextinction]]) of a species requires a [[Theory of species|clear definition of that species]]. If it is to be declared extinct, the species in question must be uniquely distinguishable from any ancestor or daughter species, and from any other closely related species. Extinction of a species (or replacement by a daughter species) plays a key role in the [[punctuated equilibrium]] hypothesis of [[Stephen Jay Gould]] and [[Niles Eldredge]].<ref>See: Niles Eldredge, ''Time Frames: Rethinking of Darwinian Evolution and the Theory of Punctuated Equilibria'', 1986, Heinemann {{ISBN|0-434-22610-6}}</ref>

[[File:Various dinosaurs.png|thumb|left|Skeleton of various extinct [[dinosaur]]s; some other dinosaur lineages still flourish in the form of [[birds]]]]
In [[ecology]], ''extinction'' is sometimes used informally to refer to [[local extinction]], in which a species ceases to exist in the chosen area of study, despite still existing elsewhere. Local extinctions may be made good by the reintroduction of individuals of that species taken from other locations; [[wolf reintroduction]] is an example of this. Species that are not globally extinct are termed [[Extant taxon|extant]]. Those species that are extant, yet are threatened with extinction, are referred to as [[threatened]] or [[endangered species]].

[[File:Edwards' Dodo.jpg|thumb|The [[dodo]] of [[Mauritius]], shown here in a 1626 illustration by [[Roelant Savery]], is an often-cited example of [[Holocene extinction|modern extinction]].<ref name="Diamond">{{cite book |last=Diamond |first=Jared |author-link=Jared Diamond |title=Guns, Germs, and Steel |publisher=W.W. Norton |year=1999 |isbn=978-0-393-31755-8 |pages=[https://archive.org/details/gunsgermssteelfa00diam/page/43 43–44] |chapter=Up to the Starting Line |title-link=Guns, Germs, and Steel}}</ref>]]
Currently, an important aspect of extinction is human attempts to preserve critically endangered species. These are reflected by the creation of the [[conservation status]] [[extinct in the wild|"extinct in the wild" (EW)]]. Species listed under this status by the [[International Union for Conservation of Nature]] (IUCN) are not known to have any living specimens in the wild and are maintained only in [[zoo]]s or other artificial environments. Some of these species are functionally extinct, as they are no longer part of their natural habitat and it is unlikely the species will ever be restored to the wild.<ref name="Maas">Maas, Peter. "[http://www.petermaas.nl/extinct/wilduk.htm Extinct in the Wild" ''The Extinction Website''. URL accessed January 26 2007.] {{webarchive |url=https://web.archive.org/web/20070216030551/http://www.petermaas.nl/extinct/wilduk.htm |date=February 16, 2007 }}</ref> When possible, modern [[zoology|zoological]] institutions try to maintain a [[viable population]] for species preservation and possible future [[reintroduction]] to the wild, through use of carefully planned [[breeding program]]s.

The extinction of one species' wild population can have knock-on effects, causing further extinctions. These are also called "chains of extinction".<ref>{{cite journal |last1=Quince |first1=Christopher |last2=Higgs |first2=Paul G. |last3=McKane |first3=Alan J. |title=Deleting species from model food webs |journal=Oikos |date=August 2005 |volume=110 |issue=2 |pages=283–296 |doi=10.1111/j.0030-1299.2005.13493.x |arxiv=q-bio/0401037 |bibcode=2005Oikos.110..283Q |s2cid=16750824}}</ref> This is especially common with extinction of [[keystone species]].

A 2018 study indicated that the [[sixth mass extinction]] started in the [[Late Pleistocene]] could take up to 5 to 7&nbsp;million years to restore mammal diversity to what it was before the human era.<ref name=davis2018/><ref>{{cite news |last1=Mosbergen |first1=Dominique |title=Mammals Will Still Be Recovering From Human Destruction Long After We're Gone |url=https://www.huffpost.com/entry/mammal-diversity-extinction-study_n_5bc59f68e4b055bc94796ecf |work=HuffPost |date=16 October 2018 |access-date=9 February 2022 |archive-date=9 February 2022 |archive-url=https://web.archive.org/web/20220209131519/https://www.huffpost.com/entry/mammal-diversity-extinction-study_n_5bc59f68e4b055bc94796ecf |url-status=live}}</ref>

===Pseudoextinction===
{{Main|Pseudoextinction}}

Extinction of a parent species where daughter species or subspecies are still extant is called pseudoextinction or phyletic extinction. Effectively, the old taxon vanishes, transformed ([[anagenesis]]) into a successor,<ref>{{cite book |last1=King |first1=Michael |last2=Mulligan |first2=Pamela |last3=Stansfield |first3=William |title=A Dictionary of Genetics |chapter=Pseudoextinction |date=2014 |publisher=Oxford University Press |edition=8th |isbn=978-0-19-976644-4 |url=https://www.oxfordreference.com/display/10.1093/acref/9780199766444.001.0001/acref-9780199766444-e-5536?rskey=f8g543&result=5527 |access-date=12 November 2023 |archive-date=21 March 2024 |archive-url=https://web.archive.org/web/20240321194758/https://www.oxfordreference.com/display/10.1093/acref/9780199766444.001.0001/acref-9780199766444-e-5536?rskey=f8g543&result=5527 |url-status=live}}</ref> or split into more than one ([[cladogenesis]]).<ref>{{Cite journal |last=Leighton |first=Lindsey R. |title=Taxon Characteristics That Promote Survivorship Through the Permian-Triassic Interval: Transition from the Paleozoic to the Mesozoic Brachiopod Fauna |journal=Paleobiology |date=2009 |volume=34 |pages=65–79 |doi=10.1666/06082.1 |s2cid=86843206}}</ref>

Pseudoextinction is difficult to demonstrate unless one has a strong chain of evidence linking a living species to members of a pre-existing species. For example, it is sometimes claimed that the extinct ''[[Hyracotherium]]'', which was an early horse that shares a common ancestor with the modern [[horse]], is pseudoextinct, rather than extinct, because there are several extant species of ''[[Equus (genus)|Equus]]'', including [[zebra]] and [[donkey]]; however, as fossil species typically leave no genetic material behind, one cannot say whether ''Hyracotherium'' [[Evolution of the horse|evolved into more modern horse species]] or merely evolved from a common ancestor with modern horses. Pseudoextinction is much easier to demonstrate for larger taxonomic groups.

===Lazarus taxa===
{{Main|Lazarus taxon}}
A Lazarus taxon or Lazarus species refers to instances where a species or taxon was thought to be extinct, but was later rediscovered. It can also refer to instances where large gaps in the fossil record of a taxon result in fossils reappearing much later, although the taxon may have ultimately become extinct at a later point.

The [[coelacanth]], a fish related to [[lungfish]] and [[tetrapod]]s, is an example of a Lazarus taxon that was known only from the fossil record and was considered to have been extinct since the end of the [[Cretaceous Period]]. In 1938, however, a living specimen was found off the [[Chalumna River]] (now Tyolomnqa) on the east coast of South Africa.<ref name="dinofish">{{cite web |url=http://www.dinofish.com/discoa.htm |title="Discovery" of the Coelacanth |access-date=2 March 2013 |archive-date=21 January 2013 |archive-url=https://archive.today/20130121205250/http://www.dinofish.com/discoa.htm |url-status=live}}</ref> ''[[Calliostoma bullatum]]'', a species of deepwater [[sea snail]] originally described from fossils in 1844 proved to be a Lazarus species when extant individuals were described in 2019.<ref>{{Cite journal |last1=Freiwald |first1=André |last2=Lavaleye |first2=Marc |last3=Heugten |first3=Bart Van |last4=Beuck |first4=Lydia |last5=Hoffman |first5=Leon |date=4 June 2019 |title=Last snails standing since the Early Pleistocene, a tale of Calliostomatidae (Gastropoda) living in deep-water coral habitats in the north-eastern Atlantic |journal=Zootaxa |language=en |volume=4613 |issue=1 |pages=93–110 |doi=10.11646/zootaxa.4613.1.4 |pmid=31716426 |issn=1175-5334 |doi-access=free}}</ref>

[[Zaglossus attenboroughi|Attenborough's long-beaked echidna]] (''Zaglossus attenboroughi'') is an example of a Lazarus species from [[Papua New Guinea]] that had last been sighted in 1962 and believed to be possibly extinct, until it was recorded again in November 2023.<ref>{{Cite news |date=2023-11-10 |title=First-ever images prove 'lost echidna' not extinct |language=en-GB |url=https://www.bbc.com/news/science-environment-67363874 |access-date=2023-11-25}}</ref>

Some species thought to be extinct have had ongoing speculation that they may still exist, and in the event of rediscovery would be considered Lazarus species. Examples include the [[thylacine]], or Tasmanian tiger (''Thylacinus cynocephalus''), the last known example of which died in Hobart Zoo in Tasmania in 1936; the [[Honshū wolf|Japanese wolf]] (''Canis lupus hodophilax''), last sighted over 100 years ago; the [[Ivory-billed woodpecker|American ivory-billed woodpecker]] (''Campephilus principalis''), with the last universally accepted sighting in 1944; and the [[slender-billed curlew]] (''Numenius tenuirostris''), not seen since 2007.<ref>{{cite web |last1=Platt |first1=John R. |title=4 Extinct Species That People Still Hope to Rediscover |url=https://blogs.scientificamerican.com/extinction-countdown/4-extinct-species-hope-rediscover/ |work=Scientific American Blog Network |date=21 February 2013 |access-date=9 February 2022 |archive-date=9 February 2022 |archive-url=https://web.archive.org/web/20220209131524/https://blogs.scientificamerican.com/extinction-countdown/4-extinct-species-hope-rediscover/ |url-status=live}}{{self-published inline|date=February 2022}}</ref>