Coelacanth

[[File:Coelacanth.png|thumb|right|thumb|165px|"A Ceola- ... A Coleo- ... This Ugly Sucker Here"<ref>Tom Weller, ''Science Made Stupid''</ref>]]{{evolution}}

The '''coelacanths''' (derived from '''Coelacanthiformes''', and named after the [[Carboniferous]] genus ''Coelacanthus'') are the most archaic extant lineage of the [[Sarcopterygii]], the so-called ''lobe-finned fishes'' from within which all [[tetrapod]]s [[Evolution|evolved]]. Never a highly diverse order of fish, today the coelacanths are represented by the single extant genus ''Latimeria'', with just two species living in deep water off the coasts of southern and eastern [[Africa]], Madagascar, and Sulawesi, [[Indonesia]].

Coelacanths shot into the public eye after {{wpl|Marjorie Courtenay-Latimer}} (for whom the genus ''Latimeria'' is named) discovered the modern species ''Latimeria chalumnae'' in [[South Africa]] in 1938, as the entire order of coelacanths had previously been thought to have gone extinct 66 million years ago in the [[K-Pg extinction event]]. Coelacanths are completely inedible (both for [[human]]s and for most other [[animal]]s) due to a variety of noxious [[chemical]]s in their flesh. The few people stupid enough to try eating them invariably come down with vicious vomiting and diarrhea. This probably goes a long way towards explaining their longevity as a species.

==Evolutionary history==
Coelacanths first appear in the mid-[[Devonian]] and diverged into many different types in the late [[Paleozoic]], reaching their peak in the [[Triassic]].<ref>Schaeffer, B. 1952. The Triassic coelacanth fish Diplurus, with observations on the evolution of the Coelacanthini. ''Bulletins of the American Museum of Natural History'' 99: 25-78.</ref> Coelacanths are [[fish]] and thus are related to the ancestors of tetrapods ([[amphibians]], synapsids, and sauropsids), though they evolved differently from the rhipidistian fishes (including [[lungfish]]). It was once thought that coelacanths were the closest evolutionary relatives to tetrapods, but [[DNA]] evidence has shown lungfish to be more closely related.<ref>[http://www.nature.com/nature/journal/v496/n7445/pdf/nature12027.pdf The African coelacanth genome provides insights into tetrapod evolution] by Amemiya, Chris T. et al. (18 April 2013)''Nature'' 496 (7445): 311–6.</ref><ref>[http://www.smithsonianmag.com/science-nature/dna-sequencing-reveals-that-coelacanths-werent-the-missing-link-between-sea-and-land-25025860/?no-ist DNA Sequencing Reveals that Coelacanths Weren’t the Missing Link Between Sea and Land] by Joseph Stromberg (April 17, 2013) ''Smithsonian''.</ref>

==Living fossil==
The coelacanth is an iconic "[[living fossil]]," having been known only from fossils before the first living specimen was discovered. As a group, the coelacanths were very successful from the Devonian until the [[Cretaceous]], with several genera and species described, but the modern genus ''Latimeria'' is not known from the fossil record. The earliest known coelacanths are in fact quite different from ''Latimeria''.  The last known fossil coelacanths are the late Cretaceous genus ''Macropoma'', which is very similar to ''Latimeria''. No fossils are known from the Cretaceous until the present.  The reason for this gap in the fossil record is not known, but suggests that, since the Cretaceous period, coelacanths have either been relatively rare or have inhabited environments not conducive to fossilization.

Only two living species are known—the West Indian Ocean coelacanth (''L. chalumnae''), and the Indonesian coelacanth (''L. menadoensis''). The two are, however, easily distinguished by their colouring; a steely-blue colouration is typical of the West Indian Ocean coelacanth, where the Indonesian coelacanth has a more brownish tint.

<gallery widths=150px heights=150px>
File:Undina penicillata (cast) at Göteborgs Naturhistoriska Museum 8837.jpg|Fossil of ''Undina penicillata'', a prehistoric genus of coelacanth.
File:Undina penicillata.jpg|Jurassic-era coelacanth fossil.
File:Coelacanth diver.jpeg|Live ''Latimeria menadoensis'' specimen with a diver in [[Indonesia]].
File:Latimeria chalumnae embryo.jpg|Preserved ''Latimeria'' embryo.
File:Latimeria Paris.jpg|Preserved ''Latimeria'' specimen.
</gallery>

==Further reading==
*Carroll, R.  1988.  ''Vertebrate Paleontology and Evolution''.  W. H. Freeman & Company, New York.
*Thomson, K. S.  1967.  Mechanisms of intracranial kinetics in fossil rhipidistian fishes (Crossopterygii) and their relatives.  ''Zoological Journal of the Linnean Society'' 46: 223-253.

==References==
{{reflist|2|90%}}

[[Category:Fish]]
[[Category:Transitional fossils]]
[[Category:EvoWiki ports]]

Categories: Fish, Transitional fossils, EvoWiki ports