Editing Living fossil (section)

{{Short description|Organism resembling a form long shown in the fossil records}}
{{Redirect|Living Fossil|the story by L. Sprague de Camp|Living Fossil (short story)}}
{{use dmy dates|cs1-dates=ly|date=November 2024}}{{EngvarB|date=January 2019}}
[[File:Coelacanth CAS 1.JPG|thumb|upright=1.35|The [[coelacanth]]s were thought to have gone extinct {{Ma|66}}, until a living specimen belonging to the [[order (biology)|order]] was discovered in 1938.]]

A ''' living fossil ''' is a [[Deprecation|deprecated]] term for an [[extant taxon]] that [[phenotypically]] resembles related [[species]] known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant [[clade]]. Living fossils commonly are of species-poor lineages, but they need not be. While the [[body plan]] of a living fossil remains superficially similar, it is never the same species as the remote relatives it resembles, because [[genetic drift]] would inevitably change its chromosomal structure.

Living fossils exhibit [[punctuated equilibrium|stasis]] (also called "bradytely") over geologically long time scales. Popular literature may wrongly claim that a "living fossil" has undergone no significant evolution since fossil times, with practically no [[molecular evolution]] or [[Morphology (biology)|morphological]] changes. Scientific investigations have repeatedly discredited such claims.<ref name="Casane">{{Cite journal|title = Why coelacanths are not 'living fossils'|journal = BioEssays|date = 2013-04-01|issn = 1521-1878|pages = 332–338|volume = 35|issue = 4|doi = 10.1002/bies.201200145|language = en|first1 = Didier|last1 = Casane|first2 = Patrick|last2 = Laurenti|pmid=23382020|s2cid = 2751255|doi-access = free}}</ref><ref>{{Cite journal|title = Multiple global radiations in tadpole shrimps challenge the concept of 'living fossils'|journal = PeerJ|pmc = 3628881|pmid = 23638400|volume = 1|doi = 10.7717/peerj.62|first1 = Thomas C.|last1 = Mathers|first2 = Robert L.|last2 = Hammond|first3 = Ronald A.|last3 = Jenner|first4 = Bernd|last4 = Hänfling|first5 = Africa|last5 = Gómez|pages=e62|year = 2013 | doi-access=free }}</ref><ref>{{Cite journal|title = Relict species: a relict concept?|journal = Trends in Ecology & Evolution|date = 2014-01-12|issn = 0169-5347|pmid = 25454211|pages = 655–663|volume = 29|issue = 12|doi = 10.1016/j.tree.2014.10.002|language = en|first1 = Philippe|last1 = Grandcolas|first2 = Romain|last2 = Nattier|first3 = Steve|last3 = Trewick| bibcode=2014TEcoE..29..655G }}</ref>

The minimal superficial changes to living fossils are mistakenly declared as an absence of evolution, but they are examples of [[stabilizing selection]], which is an [[evolutionary process]]—and perhaps the dominant process of [[morphological evolution]].<ref>{{cite journal|last1=Lynch|first1=M|title=The rate of evolution in mammals from the standpoint of the neutral expectation|journal=The American Naturalist|date=1990|volume=136|issue=6|pages=727–741|doi=10.1086/285128|s2cid=11055926}}</ref>

The term is currently deprecated among paleontologists and evolutionary biologists.