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{{Short description|Class of lobe-finned fishes}} | {{Short description|Class of lobe-finned fishes}} | ||
{{About|the class of fish|the living species of coelacanths|Latimeria}} | {{More citations needed|date=September 2025}} | ||
{{About|the class of fish|information on the two living species of coelacanths|Latimeria}} | |||
{{Use dmy dates|date=February 2025}} | {{Use dmy dates|date=February 2025}} | ||
{{Automatic taxobox | {{Automatic taxobox | ||
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| fossil_range = [[Early Devonian]] – [[Recent]],<ref name="ref4" /> {{fossil range|409|0}} | | fossil_range = [[Early Devonian]] – [[Recent]],<ref name="ref4" /> {{fossil range|409|0}} | ||
| image = Coelacanth off Pumula on the KwaZulu-Natal South Coast, South Africa, on 22 November 2019.png | | image = Coelacanth off Pumula on the KwaZulu-Natal South Coast, South Africa, on 22 November 2019.png | ||
| image_caption = [[West Indian Ocean coelacanth|Live coelacanth]] off [[Umzumbe|Pumula]] on the [[KwaZulu-Natal South Coast]], South Africa | | image_caption = [[West Indian Ocean coelacanth|Live coelacanth]] ([[Latimeriidae]]) off [[Umzumbe|Pumula]] on the [[KwaZulu-Natal South Coast]], South Africa | ||
| image_upright = 1.15 | | image_upright = 1.15 | ||
| image2 = Axelrodichthys araripensis - Naturmuseum Senckenberg - DSC02202.JPG | | image2 = Axelrodichthys araripensis - Naturmuseum Senckenberg - DSC02202.JPG | ||
| image2_caption = Specimen of ''[[Axelrodichthys]] araripensis'' | | image2_caption = Specimen of ''[[Axelrodichthys]] araripensis'' ([[Mawsoniidae]]) from the Early Cretaceous of Brazil | ||
| display_parents = 2 | | display_parents = 2 | ||
| taxon = Actinistia | | taxon = Actinistia | ||
| Line 34: | Line 35: | ||
}} | }} | ||
'''Coelacanths''' ({{IPAc-en|audio=En-us-coelacanth.ogg|ˈ|s|iː|l|ə|k|æ|n|θ}} {{respell|SEE|lə-kanth}}) are an ancient group of [[Sarcopterygii|lobe-finned fish]] (Sarcopterygii) in the [[Class (biology)|class]] '''Actinistia'''.<ref>{{Cite book |last=Nelson |first=Joseph S. | '''Coelacanths''' ({{IPAc-en|audio=En-us-coelacanth.ogg|ˈ|s|iː|l|ə|k|æ|n|θ}} {{respell|SEE|lə-kanth}}) are an ancient group of [[Sarcopterygii|lobe-finned fish]] (Sarcopterygii) in the [[Class (biology)|class]] '''Actinistia'''.<ref>{{Cite book |last=Nelson |first=Joseph S. |title=Fishes of the World |date=16 March 2016 |publisher=John Wiley & Sons |isbn=978-1-119-22081-7 |oclc=951128215|pages=103–105}}</ref><ref>{{Cite web |title=Order Summary for Coelacanthiformes |url=https://www.fishbase.se/summary/OrdersSummary.php?order=Coelacanthiformes |access-date=2023-03-13 |website=fishbase.se}}</ref> As sarcopterygians, they are more closely related to [[lungfish]] and [[tetrapods]] (the terrestrial vertebrates including living [[amphibian]]s, [[reptile]]s, [[bird]]s and [[mammal]]s) than to [[Actinopterygii|ray-finned fish]]. | ||
The name '''coelacanth''' originates from the [[Permian]] genus ''[[Coelacanthus]]'', which was the first [[scientifically named]] genus of coelacanths (in 1839), becoming the [[type genus]] of '''Coelacanthiformes''' as other species were discovered and named.<ref>{{cite book|last=Agassiz|first=L.|author-link=Louis Agassiz|date=1839|title= Recherches sur les poissons fossiles II|url=https://www.biodiversitylibrary.org/bibliography/4275|publisher=Petitpierre|location=Neuchâtel|doi=10.5962/bhl.title.4275|pages=xxxvi-xxxviii|access-date=12 May 2025}}</ref><ref>{{cite web|url=https://www.nhm.ac.uk/discover/coelacanths-the-fish-that-outdid-the-loch-ness-monster.html|title=Coelacanths: the fish that 'outdid' the Loch Ness Monster |last=Osterloff|first=Emily|publisher=Natural History Museum, London|access-date=12 May 2025}}</ref> Well-represented in freshwater and marine [[Geological formation|deposits]] from as early as the [[Devonian]] period (more than 410{{nbsp}}[[million years ago]]), they were thought to have become extinct in the [[Late Cretaceous]], around [[Cretaceous–Paleogene extinction event|66{{nbsp}}million years ago]]. | The name '''coelacanth''' originates from the [[Permian]] genus ''[[Coelacanthus]]'', which was the first [[scientifically named]] genus of coelacanths (in 1839), becoming the [[type genus]] of '''Coelacanthiformes''' as other species were discovered and named.<ref>{{cite book|last=Agassiz|first=L.|author-link=Louis Agassiz|date=1839|title= Recherches sur les poissons fossiles II|url=https://www.biodiversitylibrary.org/bibliography/4275|publisher=Petitpierre|location=Neuchâtel|doi=10.5962/bhl.title.4275|pages=xxxvi-xxxviii|access-date=12 May 2025}}</ref><ref>{{cite web|url=https://www.nhm.ac.uk/discover/coelacanths-the-fish-that-outdid-the-loch-ness-monster.html|title=Coelacanths: the fish that 'outdid' the Loch Ness Monster |last=Osterloff|first=Emily|publisher=Natural History Museum, London|access-date=12 May 2025}}</ref> Well-represented in freshwater and marine [[Geological formation|deposits]] from as early as the [[Devonian]] period (more than 410{{nbsp}}[[million years ago]]), they were thought to have become extinct in the [[Late Cretaceous]], around [[Cretaceous–Paleogene extinction event|66{{nbsp}}million years ago]]. | ||
The first living species, ''[[Latimeria chalumnae]]'', the West [[Indian Ocean]] coelacanth, was [[Species description|described]] from specimens [[Fishing|fished]] off the coast of [[South Africa]] from 1938 onward;<ref name=Smith>{{cite book|last=Smith|first=J. L. B.|title=Old Fourlegs: the Story of the Coelacanth|publisher=Longmans Green |year=1956 |page=24}}</ref><ref name="ref2">{{cite journal |bibcode=1975Sci...190.1105L |title=Latimeria, the Living Coelacanth, is Ovoviviparous |last1=Lavett Smith |first1=C. |last2=Rand |first2=Charles S. |last3=Schaeffer |first3=Bobb |last4=Atz |first4=James W. |volume=190 |year=1975 |pages=1105–6 |journal=Science |doi=10.1126/science.190.4219.1105 |issue=4219|s2cid=83943031 }}</ref> they are now also known to inhabit the seas around the [[Comoro Islands]] off the [[East Africa|east coast of Africa]]. The second species, ''[[Latimeria menadoensis]]'', the Indonesian coelacanth, was discovered in the late | The first living species, ''[[Latimeria chalumnae]]'', the West [[Indian Ocean]] coelacanth, was [[Species description|described]] from specimens [[Fishing|fished]] off the coast of [[South Africa]] from 1938 onward;<ref name=Smith>{{cite book|last=Smith|first=J. L. B.|title=Old Fourlegs: the Story of the Coelacanth|publisher=Longmans Green |year=1956 |page=24}}</ref><ref name="ref2">{{cite journal |bibcode=1975Sci...190.1105L |title=Latimeria, the Living Coelacanth, is Ovoviviparous |last1=Lavett Smith |first1=C. |last2=Rand |first2=Charles S. |last3=Schaeffer |first3=Bobb |last4=Atz |first4=James W. |volume=190 |year=1975 |pages=1105–6 |journal=Science |doi=10.1126/science.190.4219.1105 |issue=4219|s2cid=83943031 }}</ref> they are now also known to inhabit the seas around the [[Comoro Islands]] off the [[East Africa|east coast of Africa]]. The second species, ''[[Latimeria menadoensis]]'', the Indonesian coelacanth, was discovered in the late 1990s, which inhabits the seas of [[Eastern Indonesia]], from [[Manado]] to [[Western New Guinea|Papua]].<ref>{{Cite journal|title = Adaptive evolution of color vision of the Comoran coelacanth (Latimeria chalumnae)|journal = Proceedings of the National Academy of Sciences|volume = 96|issue = 11|pages = 6279–84|last1 = Yokoyama|first1 = Shozo|last2 = Zhang|first2 = Huan|last3 = Radlwimmer|first3 = F. Bernhard|last4 = Blow|first4 = Nathan S.|year = 1999|doi = 10.1073/pnas.96.11.6279|pmid = 10339578|pmc = 26872|bibcode = 1999PNAS...96.6279Y|doi-access = free}}</ref> | ||
The coelacanth (more accurately, the extant genus ''[[Latimeria]]'') is often considered an example of a "[[living fossil]]" in [[popular science]] because it was considered the sole remaining member of a [[taxon]] otherwise known only from fossils (a [[Relict (biology)|biological relict]]),<ref>{{cite web |last1=Latham |first1=Katherine |title=The deep ocean photographer that captured a 'living fossil' |url=https://www.bbc.com/future/article/20240507-the-deep-ocean-photographer-that-captured-a-living-fossil |website=bbc.com |publisher=British Broadcasting Corporation |access-date=13 June 2025}}</ref><ref name="ref1">{{cite book |last1=Forey |first1=Peter L |title=History of the Coelacanth Fishes |publisher=Chapman & Hall |year=1998 |isbn=978-0-412-78480-4 |location=London|pages=1, 3, 6, 13–16, 19, 27, 32, 35–40}}</ref>{{rp|1}} evolving a [[Body plan|bodyplan]] similar to its current form approximately 400{{nbsp}}million years ago.<ref name="ref4">{{cite journal |doi=10.1098/rsbl.2006.0470 |title=Oldest coelacanth, from the Early Devonian of Australia |year=2006 |last1=Johanson |first1=Z. |last2=Long |first2=J. A |last3=Talent |first3=J. A |last4=Janvier |first4=P. |last5=Warren |first5=J. W |journal=Biology Letters |volume=2 |issue=3 |pages=443–6 |pmid=17148426 |pmc=1686207}}</ref> However, studies of fossil coelacanths have shown that coelacanth body shapes (and their [[Ecological niche|niches]]) were much more diverse than what was previously thought, and often differed significantly from ''Latimeria''.<ref name="Friedman2007">{{cite journal |doi=10.1111/j.1525-142X.2007.00169.x |title=First discovery of a primitive coelacanth fin fills a major gap in the evolution of lobed fins and limbs |year=2007 |last1=Friedman |first1=Matt |last2=Coates |first2=Michael I. |last3=Anderson |first3=Philip |journal=Evolution & Development |volume=9 |issue=4 |pages=329–37 |pmid=17651357|s2cid=23069133 }}</ref><ref name="Friedman2006">{{cite journal |doi=10.1098/rspb.2005.3316 |title=A newly recognized fossil coelacanth highlights the early morphological diversification of the clade |year=2006 |last1=Friedman |first1=Matt |last2=Coates |first2=Michael I. |journal=Proceedings of the Royal Society B: Biological Sciences |volume=273 |issue=1583 |pages=245–50 |jstor=25223279 |pmid=16555794 |pmc=1560029}}</ref><ref name=Rebellatrix>{{cite journal |doi=10.1080/02724634.2012.657317 |title=A fork-tailed coelacanth, Rebellatrix divaricerca, gen. Et sp. Nov. (Actinistia, Rebellatricidae, fam. Nov.), from the Lower Triassic of Western Canada |year=2012 |last1=Wendruff |first1=Andrew J. |last2=Wilson |first2=Mark V. H. |journal=Journal of Vertebrate Paleontology |volume=32 |issue=3 |pages=499–511|bibcode=2012JVPal..32..499W |s2cid=85826893 }}</ref><!--Could Latimeria's body plan be called [[plesiomorphic]] then?--> | The coelacanth (more accurately, the extant genus ''[[Latimeria]]'') is often considered an example of a "[[living fossil]]" in [[popular science]] because it was considered the sole remaining member of a [[taxon]] otherwise known only from fossils (a [[Relict (biology)|biological relict]]),<ref>{{cite web |last1=Latham |first1=Katherine |title=The deep ocean photographer that captured a 'living fossil' |url=https://www.bbc.com/future/article/20240507-the-deep-ocean-photographer-that-captured-a-living-fossil |website=bbc.com |date=8 May 2024 |publisher=British Broadcasting Corporation |access-date=13 June 2025}}</ref><ref name="ref1">{{cite book |last1=Forey |first1=Peter L |title=History of the Coelacanth Fishes |publisher=Chapman & Hall |year=1998 |isbn=978-0-412-78480-4 |location=London|pages=1, 3, 6, 13–16, 19, 27, 32, 35–40}}</ref>{{rp|1}} evolving a [[Body plan|bodyplan]] similar to its current form approximately 400{{nbsp}}million years ago.<ref name="ref4">{{cite journal |doi=10.1098/rsbl.2006.0470 |title=Oldest coelacanth, from the Early Devonian of Australia |year=2006 |last1=Johanson |first1=Z. |last2=Long |first2=J. A |last3=Talent |first3=J. A |last4=Janvier |first4=P. |last5=Warren |first5=J. W |journal=Biology Letters |volume=2 |issue=3 |pages=443–6 |pmid=17148426 |pmc=1686207}}</ref> However, studies of fossil coelacanths have shown that coelacanth body shapes (and their [[Ecological niche|niches]]) were much more diverse than what was previously thought, and often differed significantly from ''Latimeria''.<ref name="Friedman2007">{{cite journal |doi=10.1111/j.1525-142X.2007.00169.x |title=First discovery of a primitive coelacanth fin fills a major gap in the evolution of lobed fins and limbs |year=2007 |last1=Friedman |first1=Matt |last2=Coates |first2=Michael I. |last3=Anderson |first3=Philip |journal=Evolution & Development |volume=9 |issue=4 |pages=329–37 |pmid=17651357|s2cid=23069133 }}</ref><ref name="Friedman2006">{{cite journal |doi=10.1098/rspb.2005.3316 |title=A newly recognized fossil coelacanth highlights the early morphological diversification of the clade |year=2006 |last1=Friedman |first1=Matt |last2=Coates |first2=Michael I. |journal=Proceedings of the Royal Society B: Biological Sciences |volume=273 |issue=1583 |pages=245–50 |jstor=25223279 |pmid=16555794 |pmc=1560029}}</ref><ref name=Rebellatrix>{{cite journal |doi=10.1080/02724634.2012.657317 |title=A fork-tailed coelacanth, Rebellatrix divaricerca, gen. Et sp. Nov. (Actinistia, Rebellatricidae, fam. Nov.), from the Lower Triassic of Western Canada |year=2012 |last1=Wendruff |first1=Andrew J. |last2=Wilson |first2=Mark V. H. |journal=Journal of Vertebrate Paleontology |volume=32 |issue=3 |pages=499–511|bibcode=2012JVPal..32..499W |s2cid=85826893 }}</ref><!--Could Latimeria's body plan be called [[plesiomorphic]] then?--> | ||
== Etymology == | == Etymology == | ||
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== Discovery == | == Discovery == | ||
[[File:Coelacanthus granulatus.JPG|left|thumb|Fossil of ''[[Coelacanthus|Coelacanthus granulatus]],'' the first described coelacanth, named by [[Louis Agassiz]] in 1839]] | [[File:Coelacanthus granulatus.JPG|left|thumb|Fossil of ''[[Coelacanthus|Coelacanthus granulatus]],'' the first described coelacanth, named by [[Louis Agassiz]] in 1839]] | ||
The earliest fossils of coelacanths were discovered in the 19th century. Coelacanths | The earliest fossils of coelacanths were discovered in the 19th century. Coelacanths were believed to have become [[extinction|extinct]] at the end of the [[Cretaceous]] period.<ref>{{cite web|title = Coelacanth – Deep Sea Creatures on Sea and Sky|url = http://www.seasky.org/deep-sea/coelacanth.html|website = seasky.org|access-date = 2015-10-27}}</ref> More closely related to tetrapods than to the [[ray-finned fish]], coelacanths were considered a [[transitional form]] between fish and tetrapods.<ref>{{Cite journal |last=Meyer |first=Axel |title=Molecular evidence on the origin of tetrapods and the relationships of the coelacanth |journal=Trends in Ecology & Evolution |volume=10 |issue=3 |pages=111–116 |doi=10.1016/s0169-5347(00)89004-7 |pmid=21236972 |year=1995 |bibcode=1995TEcoE..10..111M |url=http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-36291 |type=Submitted manuscript}}</ref> | ||
Its discovery | On 22 December 1938, the first ''[[Latimeria]]'' specimen was found off the east coast of South Africa, off the [[Chalumna River]] (now Tyolomnqa).<ref name=Smith /><ref>{{Cite web |title=Marjorie Courtenay-Latimer |url=https://www.lindahall.org/about/news/scientist-of-the-day/marjorie-courtenay-latimer/ |date=24 February 2020|access-date=2024-12-20 |website=The Linda Hall Library |language=en-US}}</ref><ref>{{Cite journal |last=Smith |first=J. L. B. |date=March 1939 |title=A Living Fish of Mesozoic Type |url=https://www.nature.com/articles/143455a0 |journal=Nature |language=en |volume=143 |issue=3620 |pages=455–456 |doi=10.1038/143455a0 |bibcode=1939Natur.143..455S |issn=0028-0836}}</ref> Museum curator [[Marjorie Courtenay-Latimer]] discovered the fish among the catch of a local fisherman.<ref name=Smith /> Courtenay-Latimer contacted a Rhodes University ichthyologist, [[J. L. B. Smith]], sending him drawings of the fish, and he confirmed the fish's importance with a famous cable: "Most Important Preserve Skeleton and Gills = Fish Described."<ref name=Smith /> Its discovery over 60 million years after its supposed extinction makes the coelacanth the best-known example of a [[Lazarus taxon]], a taxon or an evolutionary line that seems to have disappeared from the fossil record only to reappear much later. Since 1938, [[West Indian Ocean coelacanth]] have been found in the [[Comoros]], [[Kenya]], [[Tanzania]], [[Mozambique]], [[Madagascar]], in [[iSimangaliso Wetland Park]], and off the South Coast of [[Kwazulu-Natal]] in South Africa.<ref name=venter>{{cite journal|last1=Venter|first1=P.|last2=Timm|first2=P.|last3=Gunn|first3=G.|last4=le Roux|first4=E.|last5=Serfontein|first5=C.|year=2000|title=Discovery of a viable population of coelacanths (''Latimeria chalumnae'' Smith, 1939) at Sodwana Bay, South Africa|journal=South African Journal of Science|volume=96|issue=11/12|pages=567–568}}</ref><ref name="Fraser et al 2020" >{{cite journal|url=https://www.sajs.co.za/article/view/7806/9870 |title=Live coelacanth discovered off the KwaZulu-Natal South Coast, South Africa |journal=South African Journal of Science |volume=116 |issue=3/4 March/April 2020 |first1=Michael D. |last1=Fraser |first2=Bruce A.S. |last2=Henderson |first3=Pieter B. |last3=Carstens |first4=Alan D. |last4=Fraser |first5=Benjamin S. |last5=Henderson |first6=Marc D. |last6=Dukes |first7=Michael N. |last7=Bruton |doi=10.17159/sajs.2020/7806 |date=26 March 2020 |doi-access=free }}</ref> | ||
The [[Comoro Islands]] specimen was discovered in December 1952.<ref>{{Cite news|url=https://www.newspapers.com/clip/11755015/prehistoric_fish_offers_rare_glimpse_of/|title=Prehistoric fish offers rare glimpse of hidden sea life – Coelacanth (1953)|date=1953-02-23|work=Abilene Reporter-News|access-date=2017-06-18|page=25}}</ref> Between 1938 and 1975, 84 specimens were caught and recorded.<ref>{{Cite news|url=https://www.newspapers.com/clip/11755368/70millionyearold_fish_dissected/|title=70-million-year-old fish dissected – Coaelacanth (1975)|date=1975-05-28|work=Redlands Daily Facts|access-date=2017-06-18|page=6}}</ref> | The [[Comoro Islands]] specimen was discovered in December 1952.<ref>{{Cite news|url=https://www.newspapers.com/clip/11755015/prehistoric_fish_offers_rare_glimpse_of/|title=Prehistoric fish offers rare glimpse of hidden sea life – Coelacanth (1953)|date=1953-02-23|work=Abilene Reporter-News|access-date=2017-06-18|page=25}}</ref> Between 1938 and 1975, 84 specimens were caught and recorded.<ref>{{Cite news|url=https://www.newspapers.com/clip/11755368/70millionyearold_fish_dissected/|title=70-million-year-old fish dissected – Coaelacanth (1975)|date=1975-05-28|work=Redlands Daily Facts|access-date=2017-06-18|page=6}}</ref> | ||
The second [[ | The second [[extant species]], the [[Indonesian coelacanth]], was first recognized in [[Manado]], North Sulawesi, Indonesia, by Mark V. Erdmann and his wife Arnaz Mehta at a local [[fish market]] in September 1997, but were only able to take a few photographs of the first specimen of this species before it was sold. After confirming that it was a unique discovery, Erdmann returned to Sulawesi in November 1997 to interview fishermen and look for further examples. A second specimen was caught by a fisherman in July 1998 and was then handed to Erdmann.<ref>{{cite journal |title=Coelacanth discovery in Indonesia |first=Henry |last=Gee |date= 1 October 1998 | journal=Nature | doi=10.1038/news981001-1 }}</ref><ref>{{cite web |url=http://www.ucmp.berkeley.edu/vertebrates/coelacanth/coelacanth1.html |title=The Discovery |publisher=University of California Museum of Paleontology }}</ref> The species was [[Species description|described]] in 1999 by Pouyaud et al.<ref name=Pouyaud>{{cite journal |doi=10.1016/S0764-4469(99)80061-4 |title=Une nouvelle espèce de cœlacanthe. Preuves génétiques et morphologiques |trans-title=A new species of coelacanth. Genetic and morphologic proof |language=fr |year=1999 |last1=Pouyaud |first1=Laurent |last2=Wirjoatmodjo |first2=Soetikno |last3=Rachmatika |first3=Ike |last4=Tjakrawidjaja |first4=Agus |last5=Hadiaty |first5=Renny |last6=Hadie |first6=Wartono |journal=Comptes Rendus de l'Académie des Sciences |volume=322 |issue=4 |pages=261–7 |bibcode=1999CRASG.322..261P |pmid=10216801}}</ref> based on Erdmann's 1998 specimen <ref name=Erdmann>{{cite journal |doi=10.1038/26376 |year=1998 |last1=Erdmann |first1=Mark V. |last2=Caldwell |first2=Roy L. |last3=Moosa |first3=M. Kasim |journal=Nature |volume=395 |issue=6700 |page=335 |bibcode=1998Natur.395..335E |title=Indonesian 'king of the sea' discovered|s2cid=204997216 |doi-access=free }}</ref> and deposited at a facility of the [[Indonesian Institute of Sciences]] (LIPI).<ref>{{cite journal |url=https://www.science.org/content/article/dispute-over-legendary-fish |title= Dispute Over a Legendary Fish|first= Constance |last=Holden|date=30 March 1999 |journal=Science |volume= 284|issue= 5411|pages= 22–3|doi= 10.1126/science.284.5411.22b|pmid= 10215525|s2cid= 5441807|url-access= subscription}}</ref> | ||
== | === Distribution === | ||
{{Missing information|section|the countries and continents that fossil coelacanths were found in|date=September 2025}} | |||
[[File:Latimeria | {{See also|Latimeria#Discoveries}} | ||
[[File:Latimeria distribution RUS.png|thumb|upright=1.3|Geographical distribution of coelacanth]] | |||
[[Prehistory|Prehistorically]], Actinistians ranged throughout the world, being found in [[geological formation]]s of Europe,<ref name="Cavin&al.2020"/><ref name="Cavin&al.2016"/> the Americas,<ref name="Maisey1986">{{cite journal|last1=Maisey|first1=J.G.|title=Coelacanths from the Lower Cretaceous of Brazil|journal=American Museum Novitates|date=1986|issue=2866|pages=1–30|hdl=2246/5188|url=http://hdl.handle.net/2246/5188}}</ref><ref name="Espinosa-Arrubarrena&al.1996">{{cite journal|last1=Espinosa-Arrubarrena|first1=L.|author2=Applegate, S.P.|author3=González-Rodríguez, K.|title=The first Mexican record of a coelacanth (Osteichthyes: Sarcopterygii) from the Tlayua quarries near Tepexi de Rodríguez, Puebla, with a discussion on the importance of this fossil: Sixth North American Paleontological Convention, Abstracts of Papers|journal=Paleontological Society Special Publication|date=1996|volume=116|page=116|doi=10.1017/S2475262200001180|doi-access=free}}</ref><ref name="González-Rodríguez&al.2016">{{cite journal|last1=González-Rodríguez|first1=K.A.|author2=Fielitz, Ch.|author3=Bravo-Cuevas, V.M.|author4=Baños-Rodríguez, R.E.|title=Cretaceous osteichthyan fish assemblages from Mexico|journal=New Mexico Museum of Natural History and Science Bulletin|date=2016|volume=71|pages=107–119}}</ref><ref>{{cite journal |last=Brownstein |first=Chase D. |year=2023 |title=A large coelacanth, †''Whiteia giganteus'' sp. nov., from the Triassic of Texas, USA, establishes a Pangean radiation of early Mesozoic actinistians |journal=Palaeontologia Electronica |volume=26 |issue=1 |pages=a9 |url=https://palaeo-electronica.org/content/pdfs/1254.pdf}}</ref> Australia,<ref name=":3">{{Cite journal |last1=Clement |first1=Alice M. |last2=Cloutier |first2=Richard |last3=Lee |first3=Michael S. Y. |last4=King |first4=Benedict |last5=Vanhaesebroucke |first5=Olivia |last6=Bradshaw |first6=Corey J. A. |last7=Dutel |first7=Hugo |last8=Trinajstic |first8=Kate |last9=Long |first9=John A. |date=2024-09-12 |title=A Late Devonian coelacanth reconfigures actinistian phylogeny, disparity, and evolutionary dynamics |journal=Nature Communications |language=en |volume=15 |issue=1 |page=7529 |doi=10.1038/s41467-024-51238-4 |pmid=39266502 |issn=2041-1723|pmc=11392942 |bibcode=2024NatCo..15.7529C }}</ref> and Greenland.<ref>{{cite journal |first=E. |last=Stensiö |year=1932 |title=Triassic Fishes from East Greenland collected by the Danish expeditions in 1929-1931 |journal=Meddelelser om Grønland |volume=83 |issue=3 |pages=1–305}}</ref><ref>{{Cite book |last=Stensiö |first=Erik |author-link=Erik Stensiö |title=Triassic fishes from Spitzbergen |year=1921 |publisher=Adolf Holzhausen |location=Vienna |pages=xxviii + 307 |doi=10.5962/bhl.title.159141|s2cid=83338211 |doi-access=free }}</ref><ref>{{cite book |last=Forey |first=Peter L. |year=1998 |title=History of the coelacanth fishes |publisher=Chapman & Hall |location=London |page=434 |isbn=978-0-412-78480-4}}.</ref> | |||
Some species of Actinistians, especially the [[Mawsoniidae|Mawsoniids]], were found in deposits corresponding to [[Brackish water|brackish]] and even [[Freshwater ecosystem|freshwater environments]], suggesting an [[anadromous]] ability.<ref name="Cavin&al.2016"/><ref name="Cavin&al.2020"/> | |||
The | The two extant ''Latimeria'' species, the West Indian Ocean coelacanth and the Indonesian coelacanth, are restricted to a few locales within the [[Indo-Pacific]] and are named base on their range.<ref name="ref10" /> | ||
== Description == | |||
{{See also|Latimeria#Description}} | |||
[[File:Pectoral fin Latimeria chalumnae.jpg|thumb|[[Pectoral fin]] of a West Indian Ocean coelacanth]] | [[File:Pectoral fin Latimeria chalumnae.jpg|thumb|[[Pectoral fin]] of a West Indian Ocean coelacanth]] | ||
Coelacanths are a part of [[Sarcopterygii]] or the lobe-finned fishes, the same [[clade]] as the lungfish and [[tetrapod]]s, and they all possess lobed fins as opposed to rayed fins. Externally, several [[Autapomorphy|characteristics distinguish]] coelacanths from other lobe-finned fish: coelacanths have eight [[Fish fin|fins]] – two dorsal fins, two pectoral fins, two pelvic fins, one anal fin and one caudal fin. The tail is very nearly equally proportioned and is split by a terminal tuft of fin rays that make up its caudal lobe; this is alternatively termed a trilobate fin (three-lobed) or a diphycercal tail. A secondary tail extending past the primary tail separates the upper and lower halves of the coelacanth.{{Clarify|date=September 2025}} Ctenoid elasmoid scales act as thick armor to protect the coelacanth's exterior. Several internal traits also aid in differentiating coelacanths from other lobe-finned fish. At the back of the skull, the coelacanth possesses a hinge, the [[intracranial]] joint, which allows it to open its mouth extremely wide. Coelacanths also retain an oil-filled [[notochord]], a hollow, pressurized tube which is replaced by a [[vertebral column]] early in embryonic development in most other vertebrates.<ref>{{Cite web|url=http://www.scienceinafrica.co.za/2002/february/coela.htm|archive-url=https://web.archive.org/web/20130921055458/http://www.scienceinafrica.co.za/2002/february/coela.htm|title=What do we know about the coelacanths – Science in Africa|archive-date=21 September 2013}}</ref>{{Better source needed|date=September 2025}} The body is covered in [[Fish scale#Leptoid scales|ctenoid]] [[Fish scale#Elasmoid scales|elasmoid scales]] that act as armor.<ref name="Sherman 2016">{{Cite journal |last=Sherman |first=Vincent R. |title=A comparative study of piscine defense: The scales of ''Arapaima gigas'', ''Latimeria chalumnae'' and ''Atractosteus spatula'' |journal=Journal of the Mechanical Behavior of Biomedical Materials |volume=73 |pages=1–16 |year=2016 |doi=10.1016/j.jmbbm.2016.10.001 |pmid=27816416 }}</ref> | |||
The soft tissue of coelacanths is mostly known from ''Latimeria'', the [[relictual]] extant genus. | |||
== Evolution and taxonomy == | == Evolution and taxonomy == | ||
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[[File:Mawsonia scaling.png|thumb|320x320px|Estimated size of the largest known individual of the Jurassic-Cretaceous freshwater coelacanth ''[[Mawsonia (fish)|Mawsonia]]'' compared to a human]] | [[File:Mawsonia scaling.png|thumb|320x320px|Estimated size of the largest known individual of the Jurassic-Cretaceous freshwater coelacanth ''[[Mawsonia (fish)|Mawsonia]]'' compared to a human]] | ||
[[File:Allenypterus montanus (Restoration).jpg|thumb|Life restoration of the basal coelacanth ''[[Allenypterus]]'' from the Carboniferous of North America]] | [[File:Allenypterus montanus (Restoration).jpg|thumb|Life restoration of the basal coelacanth ''[[Allenypterus]]'' from the Carboniferous of North America]] | ||
Coelacanths are members of the class Actinistia, with many researchers considering the term "coelacanth" to cover all members of Actinistia.<ref name=":0">{{Cite journal |last1=Toriño |first1=Pablo |last2=Soto |first2=Matías |last3=Perea |first3=Daniel |date=2021-02-25 |title=A comprehensive phylogenetic analysis of coelacanth fishes (Sarcopterygii, Actinistia) with comments on the composition of the Mawsoniidae and Latimeriidae: evaluating old and new methodological challenges and constraints |url=https://www.researchgate.net/publication/349631865 |journal=Historical Biology |volume=33 |issue=12 |pages=3423–3443 |bibcode=2021HBio...33.3423T |doi=10.1080/08912963.2020.1867982 |issn=0891-2963 |s2cid=233942585}}</ref><ref name=":1" /> The order Coelacanthiformes has been used for a subgroup of actinistians, containing the modern coelacanths, | Coelacanths are members of the class Actinistia, with many researchers considering the term "coelacanth" to cover all members of Actinistia.<ref name=":0">{{Cite journal |last1=Toriño |first1=Pablo |last2=Soto |first2=Matías |last3=Perea |first3=Daniel |date=2021-02-25 |title=A comprehensive phylogenetic analysis of coelacanth fishes (Sarcopterygii, Actinistia) with comments on the composition of the Mawsoniidae and Latimeriidae: evaluating old and new methodological challenges and constraints |url=https://www.researchgate.net/publication/349631865 |journal=Historical Biology |volume=33 |issue=12 |pages=3423–3443 |bibcode=2021HBio...33.3423T |doi=10.1080/08912963.2020.1867982 |issn=0891-2963 |s2cid=233942585}}</ref><ref name=":1" /> The order Coelacanthiformes has been used for a subgroup of actinistians, containing the modern coelacanths, as well as other extinct closely related actinistians spanning from the [[Permian]] onwards.<ref>{{Cite journal |last1=Arratia |first1=Gloria |last2=Schultze |first2=Hans-Peter |date=2015-09-03 |title=A new fossil actinistian from the Early Jurassic of Chile and its bearing on the phylogeny of Actinistia |url=http://www.tandfonline.com/doi/full/10.1080/02724634.2015.983524 |journal=Journal of Vertebrate Paleontology |language=en |volume=35 |issue=5 |article-number=e983524 |doi=10.1080/02724634.2015.983524 |bibcode=2015JVPal..35E3524A |issn=0272-4634|url-access=subscription }}</ref><ref name=":2">{{Cite journal |last1=Ferrante |first1=Christophe |last2=Cavin |first2=Lionel |date=2025-06-06 |editor-last=Carnevale |editor-first=Giorgio |title=A deep dive into the coelacanth phylogeny |journal=PLOS ONE |language=en |volume=20 |issue=6 |article-number=e0320214 |doi=10.1371/journal.pone.0320214 |doi-access=free |pmid=40478838 |pmc=12143573 |bibcode=2025PLoSO..2020214F |issn=1932-6203}}</ref> According to the fossil record, the divergence of coelacanths, [[lungfish]], and [[tetrapods]] is thought to have occurred during the [[Silurian]].<ref>{{Cite journal|last1=Lu|first1=Jing|last2=Giles|first2=Sam|last3=Friedman|first3=Matt|last4=Zhu|first4=Min|date=2017-12-05|title=A new stem sarcopterygian illuminates patterns of character evolution in early bony fishes|journal=Nature Communications|language=en|volume=8|issue=1|page=1932|doi=10.1038/s41467-017-01801-z|pmid=29203766|issn=2041-1723|pmc=5715141|bibcode=2017NatCo...8.1932L}}</ref> Over 100 fossil species of coelacanth have been described.<ref name=":0" /> The oldest identified coelacanth fossils are around 420–410 million years old, dating to the [[Pragian]] stage of the early [[Devonian]]. These include ''[[Eoactinistia]]'' from Australia, known only from a fragmentary jaw, as well as ''[[Euporosteus|Euporosteus yunnanensis]]'' from China, known from a partial skull that indicates it to be the earliest anatomically modern coelacanth.<ref name="ref4" /><ref name=":1">{{Cite journal |last1=Zhu |first1=Min |last2=Yu |first2=Xiaobo |last3=Lu |first3=Jing |last4=Qiao |first4=Tuo |last5=Zhao |first5=Wenjin |last6=Jia |first6=Liantao |date=2012-04-10 |title=Earliest known coelacanth skull extends the range of anatomically modern coelacanths to the Early Devonian |url=https://www.nature.com/articles/ncomms1764 |journal=Nature Communications |language=en |volume=3 |issue=1 |page=772 |doi=10.1038/ncomms1764 |pmid=22491320 |bibcode=2012NatCo...3..772Z |issn=2041-1723}}</ref> Some authors have also suggested that the slightly older [[Onychodontiformes|onychodont]] ''[[Styloichthys]]'' may also be an early coelacanth.<ref>{{cite journal|last=Friedman|first=Matt|date=10 August 2007|title=Styloichthys as the oldest coelacanth: implications for early osteichthyan interrelationships |url=https://www.tandfonline.com/doi/abs/10.1017/S1477201907002052 |journal=Journal of Systematic Palaeontology|volume=5|issue=3|pages=289–343|doi=10.1017/S1477201907002052|bibcode=2007JSPal...5..289F |s2cid=83712134|access-date=2007-12-28|url-access=subscription}}</ref> | ||
Coelacanths were never a diverse group in comparison to other groups of fish, and reached a peak diversity during the [[Early Triassic]] (252–247 million years ago),<ref name="Cavin&al.2020" /> coinciding with a burst of diversification between the Late Permian and Middle Triassic.<ref name=":0" /> Most [[Mesozoic]] coelacanths belong to the suborder Latimerioidei, which contains two major subdivisions, the marine [[Latimeriidae]], which contains modern coelacanths, as well as the extinct [[Mawsoniidae]], which were native to [[Brackish water|brackish]], freshwater as well as marine environments.<ref>{{Cite journal|last1=Cavin|first1=Lionel|last2=Cupello|first2=Camila|last3=Yabumoto|first3=Yoshitaka|last4=Léo|first4=Fragoso|last5=Deersi|first5=Uthumporn|last6=Brito|first6=Paul M.|date=2019|title=Phylogeny and evolutionary history of mawsoniid coelacanths|url=http://www.kmnh.jp/wp-content/uploads/2019/05/A17-3-Cavin.pdf|journal=Bulletin of the Kitakyushu Museum of Natural History and Human History, Series A|volume=17|pages=3–13}}</ref> | Coelacanths were never a [[Biodiversity|diverse group]] in comparison to other groups of fish, and reached a peak diversity during the [[Early Triassic]] (252–247 million years ago),<ref name="Cavin&al.2020" /> coinciding with a burst of diversification between the Late Permian and Middle Triassic.<ref name=":0" /> Most [[Mesozoic]] coelacanths belong to the suborder Latimerioidei, which contains two major subdivisions, the marine [[Latimeriidae]], which contains modern coelacanths, as well as the extinct [[Mawsoniidae]], which were native to [[Brackish water|brackish]], freshwater as well as marine environments.<ref>{{Cite journal|last1=Cavin|first1=Lionel|last2=Cupello|first2=Camila|last3=Yabumoto|first3=Yoshitaka|last4=Léo|first4=Fragoso|last5=Deersi|first5=Uthumporn|last6=Brito|first6=Paul M.|date=2019|title=Phylogeny and evolutionary history of mawsoniid coelacanths|url=http://www.kmnh.jp/wp-content/uploads/2019/05/A17-3-Cavin.pdf|journal=Bulletin of the Kitakyushu Museum of Natural History and Human History, Series A|volume=17|pages=3–13}}</ref> | ||
Paleozoic coelacanths are generally small (~{{Cvt|30–40|cm|disp=or}} in length), while Mesozoic forms were larger.<ref name=":0" /> Several specimens belonging to the Jurassic and Cretaceous mawsoniid coelacanth genera ''[[Trachymetopon]]'' and ''[[Mawsonia (fish)|Mawsonia]]'' likely reached or exceeded {{Convert|5|m|ft|abbr=off}} in length, making them amongst the largest known fishes of the Mesozoic, and amongst the largest bony fishes of all time.<ref>{{Cite journal|last1=Cavin|first1=Lionel|last2=Piuz|first2=André|last3=Ferrante|first3=Christophe|last4=Guinot|first4=Guillaume|date=2021-06-03|title=Giant Mesozoic coelacanths (Osteichthyes, Actinistia) reveal high body size disparity decoupled from taxic diversity|journal=Scientific Reports|language=en|volume=11|issue=1| | Paleozoic coelacanths are generally small (~{{Cvt|30–40|cm|disp=or}} in length), while Mesozoic forms were larger.<ref name=":0" /> Several specimens belonging to the Jurassic and Cretaceous mawsoniid coelacanth genera ''[[Trachymetopon]]'' and ''[[Mawsonia (fish)|Mawsonia]]'' likely reached or exceeded {{Convert|5|m|ft|abbr=off}} in length, making them amongst the largest known fishes of the Mesozoic, and amongst the [[List of largest fish|largest bony fishes]] of all time.<ref>{{Cite journal|last1=Cavin|first1=Lionel|last2=Piuz|first2=André|last3=Ferrante|first3=Christophe|last4=Guinot|first4=Guillaume|date=2021-06-03|title=Giant Mesozoic coelacanths (Osteichthyes, Actinistia) reveal high body size disparity decoupled from taxic diversity|journal=Scientific Reports|language=en|volume=11|issue=1|page=11812|doi=10.1038/s41598-021-90962-5|pmid=34083600|issn=2045-2322|pmc=8175595|bibcode=2021NatSR..1111812C}}</ref> | ||
The most recent fossil latimeriid is ''[[ | The most recent fossil latimeriid is ''[[Megalocoelacanthus dobiei]]'', whose disarticulated remains are found in late [[Santonian]] to middle [[Campanian]], and possibly earliest [[Maastrichtian]]-aged marine strata of the Eastern and Central United States,<ref name="Schwimmer&al.1994">{{cite journal|last1=Schwimmer|first1=D.R.|author2=Stewart, J.D.|author3=Williams, G.D.|title=Giant fossil coelacanths of the Late Cretaceous in the eastern United States|journal=Geology|date=1994|volume=2|issue=6|pages=503–506|doi=10.1130/0091-7613(1994)022<0503:GFCOTL>2.3.CO;2|bibcode=1994Geo....22..503S}}</ref><ref name="gottfried">{{cite journal|author1=Gottfried, Michael D. |author2=Rogers, Raymond R. |author3=Rogers, K. Curry |title=First record of Late Cretaceous coelacanths from Madagascar|url=https://www.researchgate.net/publication/265667981|journal= Recent Advances in the Origin and Early Radiation of Vertebrates |year=2004|pages= 687–691}}</ref><ref name="Dutel&al.2012">{{cite journal|last1=Dutel|first1=H.|author2=Maisey, J.P.|author3=Schwimmer, D.R.|author4=Janvier, P.|author5=Herbin, M.|author6=Clément, G.|title= The Giant Cretaceous Coelacanth (Actinistia, Sarcopterygii) Megalocoelacanthus dobiei Schwimmer, Stewart & Williams, 1994, and Its Bearing on Latimerioidei Interrelationships|journal=PLOS ONE|year=2012|volume= 7|issue= 11|article-number= e49911|doi=10.1371/journal.pone.0049911|pmid= 23209614|pmc= 3507921|bibcode=2012PLoSO...749911D|doi-access=free}}</ref> the most recent mawsoniids are ''[[Axelrodichthys|Axelrodichthys megadromos]]'' from early Campanian to early Maastrichtian freshwater continental deposits of France,<ref name="Cavin&al.2005">{{cite journal|last1=Cavin|first1=L.|author2=Forey, P.L.|author3=Tong, H.|author4=Buffetaut, E.|title=Latest European coelacanth shows Gondwanan affinities|journal=Biology Letters|date=2005|volume=1|issue=2|pages=176–177|doi=10.1098/rsbl.2004.0287|pmid=17148159|pmc=1626220}}</ref><ref name="Cavin&al.2016">{{cite journal|last1=Cavin|first1=L.|author2=Valentin, X.|author3=Garcia, G.|title=A new mawsoniid coelacanth (Actinistia) from the Upper Cretaceous of Southern France|journal=Cretaceous Research|date=2016|volume=62|pages=65–73|doi=10.1016/j.cretres.2016.02.002|bibcode=2016CrRes..62...65C }}</ref><ref name="Cavin&al.2020">{{cite journal|last1=Cavin|first1=L.|author2=Buffetaut, E.|author3=Dutour, Y.|author4=Garcia, G.|author5=Le Loeuff, J.|author6=Méchin, A.|author7=Méchin, P.|author8=Tong, H.|author9=Tortosa, T.|author10=Turini, E.|author11=Valentin, X.|title=The last known freshwater coelacanths: New Late Cretaceous mawsoniids remains (Osteichthyes: Actinistia) from Southern France|journal=PLOS ONE|date=2020|volume=15|issue=6|article-number=e0234183|doi=10.1371/journal.pone.0234183|pmc=7274394|pmid=32502171|bibcode=2020PLoSO..1534183C|doi-access=free}}</ref> as well as an indeterminate marine mawsoniid from Morocco, dating to the late Maastrichtian<ref name="Brito&al.2021">{{cite journal|last1=Brito|first1=P.M.|author2=Martill, D.M.|author3=Eaves, I.|author4=Smith, R.E.|author5=Cooper, S.L.A.|year=2021|title=A marine Late Cretaceous (Maastrichtian) coelacanth from North Africa|journal=Cretaceous Research|volume=122|article-number=104768|doi=10.1016/j.cretres.2021.104768|bibcode=2021CrRes.12204768B |s2cid=233551515|url=https://researchportal.port.ac.uk/portal/en/publications/a-marine-late-cretaceous-maastrichtian-coelacanth-from-north-africa(c8521ebb-5597-4a15-9320-961113ee06d9).html |url-access=subscription}}</ref> A small bone fragment from the [[Europe]]an [[Paleocene]] has been considered the only plausible post-Cretaceous record, but this identification is based on comparative bone histology methods of doubtful reliability.<ref name="Schwimmer&al.1994" /><ref>{{cite journal |last1=Ørvig |first1=Tor |title=A vertebrate bone from the Swedish Paleocene |journal=Geologiska Föreningen i Stockholm Förhandlingar |date=1 June 1986 |volume=108 |issue=2 |pages=139–141 |doi=10.1080/11035898609452636 |issn=0016-786X}}</ref> | ||
Living coelacanths have been considered "living | Living coelacanths have been considered "[[living fossil]]s" based on their supposedly conservative [[morphology (biology)|morphology]] relative to fossil species;<ref name="ref10">{{cite journal |last=Butler |first=Carolyn |title=Living Fossil Fish |journal=National Geographic |date=March 2011 |pages=86–93}}</ref><ref name="ref1" />{{rp|1}} however, recent studies have expressed the view that coelacanth morphologic conservatism is a belief not based on data.<ref name="Friedman2007" /><ref name="Friedman2006" /><ref name="Rebellatrix" /><ref name="Casane">{{cite journal |doi=10.1002/bies.201200145 |title=Why coelacanths are not 'living fossils' |year=2013 |last1=Casane |first1=Didier |last2=Laurenti |first2=Patrick |journal=BioEssays |volume=35 |issue=4 |pages=332–8 |pmid=23382020|s2cid=2751255 |doi-access=free }}</ref> Fossils suggest that coelacanths were most morphologically diverse during the Devonian and Carboniferous, while Mesozoic species are generally morphologically similar to each other.<ref name=":0" /> | ||
[[Cladogram]] showing the relationships of coelacanth genera after Torino, Soto and Perea, 2021.<ref name=":0" /> | [[Cladogram]] showing the relationships of coelacanth genera after Torino, Soto and Perea, 2021.<ref name=":0" /> | ||
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=== Timeline of genera === | === Timeline of genera === | ||
After Ferrante and Cavin (2025):<ref name=":2" />[[File:Coelacanth phylogeny.png|center|frameless|750x750px]] | After Ferrante and Cavin (2025):<ref name=":2" />[[File:Coelacanth phylogeny.png|center|frameless|750x750px]] | ||
<gallery widths="200px" heights="145px"> | <gallery widths="200px" heights="145px"> | ||
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File:Coelacanth in Kuwait by Prof Dr Norman Ali Khalaf July 2019.jpg|Coelacanth at Abdallah Al Salem Cultural Center in Kuwait | File:Coelacanth in Kuwait by Prof Dr Norman Ali Khalaf July 2019.jpg|Coelacanth at Abdallah Al Salem Cultural Center in Kuwait | ||
</gallery> | </gallery> | ||
== References == | == References == | ||
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* {{cite book|last=Bruton|first=Mike|title=When I Was a Fish: Tales of an Ichthyologist|publisher=Jacana Media(Pty)Ltd|year=2015}} | * {{cite book|last=Bruton|first=Mike|title=When I Was a Fish: Tales of an Ichthyologist|publisher=Jacana Media(Pty)Ltd|year=2015}} | ||
* {{cite magazine|title=Coelacanths – The Fish That Time Forgot|first=Hans|last=Fricke|magazine=[[National Geographic (magazine)|National Geographic]]|pages=824–838|volume=173|issue=6|date=June 1988|issn=0027-9358|oclc=643483454}} | * {{cite magazine|title=Coelacanths – The Fish That Time Forgot|first=Hans|last=Fricke|magazine=[[National Geographic (magazine)|National Geographic]]|pages=824–838|volume=173|issue=6|date=June 1988|issn=0027-9358|oclc=643483454}} | ||
* {{cite journal|last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera |journal=Bulletins of American Paleontology |volume=364 |page=560 |year=2002 |url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |access-date=2011-05-17 | * {{cite journal|last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera |journal=Bulletins of American Paleontology |volume=364 |page=560 |year=2002 |url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |access-date=2011-05-17 |archive-url=https://web.archive.org/web/20090220223520/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |archive-date=20 February 2009 }} | ||
* {{cite book|last=Thomson|first=Keith S.|title=Living Fossil: the Story of the Coelacanth|publisher=W. W. Norton|year=1991}} | * {{cite book|last=Thomson|first=Keith S.|title=Living Fossil: the Story of the Coelacanth|publisher=W. W. Norton|year=1991}} | ||
* {{cite news|last=Wade|first=Nicholas|url=https://www.nytimes.com/2013/04/18/science/coelacanth-dna-may-tell-how-fish-learned-to-walk.html|title=Fish's DNA May Explain How Fins Turned to Feet|newspaper=The New York Times|date=18 April 2013|pages=A3}} | * {{cite news|last=Wade|first=Nicholas|url=https://www.nytimes.com/2013/04/18/science/coelacanth-dna-may-tell-how-fish-learned-to-walk.html|title=Fish's DNA May Explain How Fins Turned to Feet|newspaper=The New York Times|date=18 April 2013|pages=A3}} | ||
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* [https://www.pbs.org/wgbh/nova/fish/anatomy.html Anatomy of the coelacanth] by PBS ([[Adobe Flash]] required) | * [https://www.pbs.org/wgbh/nova/fish/anatomy.html Anatomy of the coelacanth] by PBS ([[Adobe Flash]] required) | ||
* [http://www.dinofish.com/ Dinofish.com] (requires a [[Frame (World Wide Web)|frame-capable browser]]) | * [http://www.dinofish.com/ Dinofish.com] (requires a [[Frame (World Wide Web)|frame-capable browser]]) | ||
* {{cite web |first=Carolyn |last=Butler |title=Der Quastenflosser: Ein Fossil taucht auf |trans-title=The Coelacanth: A fossil turns up |language=de |url=http://www.nationalgeographic.de/reportagen/der-quastenflosser-ein-fossil-taucht-auf |work=National Geographic Deutschland |date=August 2012 |access-date=19 April 2013 |archive-date=3 February 2017 |archive-url=https://web.archive.org/web/20170203124532/http://www.nationalgeographic.de/reportagen/der-quastenflosser-ein-fossil-taucht-auf | * {{cite web |first=Carolyn |last=Butler |title=Der Quastenflosser: Ein Fossil taucht auf |trans-title=The Coelacanth: A fossil turns up |language=de |url=http://www.nationalgeographic.de/reportagen/der-quastenflosser-ein-fossil-taucht-auf |work=National Geographic Deutschland |date=August 2012 |access-date=19 April 2013 |archive-date=3 February 2017 |archive-url=https://web.archive.org/web/20170203124532/http://www.nationalgeographic.de/reportagen/der-quastenflosser-ein-fossil-taucht-auf }} | ||
* [https://www.bbc.co.uk/news/science-environment-22184556 'Living fossil' coelacanth genome sequenced] BBC News Science & Environment; 17 April 2013 | * [https://www.bbc.co.uk/news/science-environment-22184556 'Living fossil' coelacanth genome sequenced] BBC News Science & Environment; 17 April 2013 | ||
Latest revision as of 13:23, 29 September 2025
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Coelacanths (Template:IPAc-en Template:Respell) are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia.[1][2] As sarcopterygians, they are more closely related to lungfish and tetrapods (the terrestrial vertebrates including living amphibians, reptiles, birds and mammals) than to ray-finned fish.
The name coelacanth originates from the Permian genus Coelacanthus, which was the first scientifically named genus of coelacanths (in 1839), becoming the type genus of Coelacanthiformes as other species were discovered and named.[3][4] Well-represented in freshwater and marine deposits from as early as the Devonian period (more than 410Template:Nbspmillion years ago), they were thought to have become extinct in the Late Cretaceous, around [[Cretaceous–Paleogene extinction event|66Template:Nbspmillion years ago]].
The first living species, Latimeria chalumnae, the West Indian Ocean coelacanth, was described from specimens fished off the coast of South Africa from 1938 onward;[5][6] they are now also known to inhabit the seas around the Comoro Islands off the east coast of Africa. The second species, Latimeria menadoensis, the Indonesian coelacanth, was discovered in the late 1990s, which inhabits the seas of Eastern Indonesia, from Manado to Papua.[7]
The coelacanth (more accurately, the extant genus Latimeria) is often considered an example of a "living fossil" in popular science because it was considered the sole remaining member of a taxon otherwise known only from fossils (a biological relict),[8][9]Template:Rp evolving a bodyplan similar to its current form approximately 400Template:Nbspmillion years ago.[10] However, studies of fossil coelacanths have shown that coelacanth body shapes (and their niches) were much more diverse than what was previously thought, and often differed significantly from Latimeria.[11][12][13]
Etymology
The word Coelacanth is an adaptation of the Modern Latin Script error: No such module "Lang". ('hollow spine'), from the Ancient Greek Script error: No such module "Lang". (Template:Transliteration, 'hollow') and Script error: No such module "Lang". (Template:Transliteration, 'spine'),[14] referring to the hollow caudal fin rays of the first fossil specimen described and named by Louis Agassiz in 1839, belonging to the genus Coelacanthus.[9]Template:Rp The genus name Latimeria commemorates Marjorie Courtenay-Latimer, who discovered the first specimen.[15]
Discovery
The earliest fossils of coelacanths were discovered in the 19th century. Coelacanths were believed to have become extinct at the end of the Cretaceous period.[16] More closely related to tetrapods than to the ray-finned fish, coelacanths were considered a transitional form between fish and tetrapods.[17]
On 22 December 1938, the first Latimeria specimen was found off the east coast of South Africa, off the Chalumna River (now Tyolomnqa).[5][18][19] Museum curator Marjorie Courtenay-Latimer discovered the fish among the catch of a local fisherman.[5] Courtenay-Latimer contacted a Rhodes University ichthyologist, J. L. B. Smith, sending him drawings of the fish, and he confirmed the fish's importance with a famous cable: "Most Important Preserve Skeleton and Gills = Fish Described."[5] Its discovery over 60 million years after its supposed extinction makes the coelacanth the best-known example of a Lazarus taxon, a taxon or an evolutionary line that seems to have disappeared from the fossil record only to reappear much later. Since 1938, West Indian Ocean coelacanth have been found in the Comoros, Kenya, Tanzania, Mozambique, Madagascar, in iSimangaliso Wetland Park, and off the South Coast of Kwazulu-Natal in South Africa.[20][21]
The Comoro Islands specimen was discovered in December 1952.[22] Between 1938 and 1975, 84 specimens were caught and recorded.[23]
The second extant species, the Indonesian coelacanth, was first recognized in Manado, North Sulawesi, Indonesia, by Mark V. Erdmann and his wife Arnaz Mehta at a local fish market in September 1997, but were only able to take a few photographs of the first specimen of this species before it was sold. After confirming that it was a unique discovery, Erdmann returned to Sulawesi in November 1997 to interview fishermen and look for further examples. A second specimen was caught by a fisherman in July 1998 and was then handed to Erdmann.[24][25] The species was described in 1999 by Pouyaud et al.[26] based on Erdmann's 1998 specimen [27] and deposited at a facility of the Indonesian Institute of Sciences (LIPI).[28]
Distribution
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Prehistorically, Actinistians ranged throughout the world, being found in geological formations of Europe,[29][30] the Americas,[31][32][33][34] Australia,[35] and Greenland.[36][37][38]
Some species of Actinistians, especially the Mawsoniids, were found in deposits corresponding to brackish and even freshwater environments, suggesting an anadromous ability.[30][29]
The two extant Latimeria species, the West Indian Ocean coelacanth and the Indonesian coelacanth, are restricted to a few locales within the Indo-Pacific and are named base on their range.[39]
Description
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Coelacanths are a part of Sarcopterygii or the lobe-finned fishes, the same clade as the lungfish and tetrapods, and they all possess lobed fins as opposed to rayed fins. Externally, several characteristics distinguish coelacanths from other lobe-finned fish: coelacanths have eight fins – two dorsal fins, two pectoral fins, two pelvic fins, one anal fin and one caudal fin. The tail is very nearly equally proportioned and is split by a terminal tuft of fin rays that make up its caudal lobe; this is alternatively termed a trilobate fin (three-lobed) or a diphycercal tail. A secondary tail extending past the primary tail separates the upper and lower halves of the coelacanth.Template:Clarify Ctenoid elasmoid scales act as thick armor to protect the coelacanth's exterior. Several internal traits also aid in differentiating coelacanths from other lobe-finned fish. At the back of the skull, the coelacanth possesses a hinge, the intracranial joint, which allows it to open its mouth extremely wide. Coelacanths also retain an oil-filled notochord, a hollow, pressurized tube which is replaced by a vertebral column early in embryonic development in most other vertebrates.[40]Template:Better source needed The body is covered in ctenoid elasmoid scales that act as armor.[41]
The soft tissue of coelacanths is mostly known from Latimeria, the relictual extant genus.
Evolution and taxonomy
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Coelacanths are members of the class Actinistia, with many researchers considering the term "coelacanth" to cover all members of Actinistia.[42][43] The order Coelacanthiformes has been used for a subgroup of actinistians, containing the modern coelacanths, as well as other extinct closely related actinistians spanning from the Permian onwards.[44][45] According to the fossil record, the divergence of coelacanths, lungfish, and tetrapods is thought to have occurred during the Silurian.[46] Over 100 fossil species of coelacanth have been described.[42] The oldest identified coelacanth fossils are around 420–410 million years old, dating to the Pragian stage of the early Devonian. These include Eoactinistia from Australia, known only from a fragmentary jaw, as well as Euporosteus yunnanensis from China, known from a partial skull that indicates it to be the earliest anatomically modern coelacanth.[10][43] Some authors have also suggested that the slightly older onychodont Styloichthys may also be an early coelacanth.[47]
Coelacanths were never a diverse group in comparison to other groups of fish, and reached a peak diversity during the Early Triassic (252–247 million years ago),[29] coinciding with a burst of diversification between the Late Permian and Middle Triassic.[42] Most Mesozoic coelacanths belong to the suborder Latimerioidei, which contains two major subdivisions, the marine Latimeriidae, which contains modern coelacanths, as well as the extinct Mawsoniidae, which were native to brackish, freshwater as well as marine environments.[48]
Paleozoic coelacanths are generally small (~Template:Cvt in length), while Mesozoic forms were larger.[42] Several specimens belonging to the Jurassic and Cretaceous mawsoniid coelacanth genera Trachymetopon and Mawsonia likely reached or exceeded Template:Convert in length, making them amongst the largest known fishes of the Mesozoic, and amongst the largest bony fishes of all time.[49]
The most recent fossil latimeriid is Megalocoelacanthus dobiei, whose disarticulated remains are found in late Santonian to middle Campanian, and possibly earliest Maastrichtian-aged marine strata of the Eastern and Central United States,[50][51][52] the most recent mawsoniids are Axelrodichthys megadromos from early Campanian to early Maastrichtian freshwater continental deposits of France,[53][30][29] as well as an indeterminate marine mawsoniid from Morocco, dating to the late Maastrichtian[54] A small bone fragment from the European Paleocene has been considered the only plausible post-Cretaceous record, but this identification is based on comparative bone histology methods of doubtful reliability.[50][55]
Living coelacanths have been considered "living fossils" based on their supposedly conservative morphology relative to fossil species;[39][9]Template:Rp however, recent studies have expressed the view that coelacanth morphologic conservatism is a belief not based on data.[11][12][13][56] Fossils suggest that coelacanths were most morphologically diverse during the Devonian and Carboniferous, while Mesozoic species are generally morphologically similar to each other.[42]
Cladogram showing the relationships of coelacanth genera after Torino, Soto and Perea, 2021.[42]
Template:CladeAfter Ferrante and Cavin (2025):[45]Template:Clade
Timeline of genera
After Ferrante and Cavin (2025):[45]
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Coelacanth
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Coelacanth at Abdallah Al Salem Cultural Center in Kuwait
References
Further reading
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External links
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- Anatomy of the coelacanth by PBS (Adobe Flash required)
- Dinofish.com (requires a frame-capable browser)
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- 'Living fossil' coelacanth genome sequenced BBC News Science & Environment; 17 April 2013
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