Coelacanth

The Coelacanths (derived from Coelacanthiformes, and named after the Carboniferous genus Coelacanthus) are today represented by a single genus, Latimeria, living in deep water off the coasts of Madagascar, a few parts of east Africa and Sulawesi, Indonesia. They are known for being completely inedible due to a variety of chemicals they contain, with the few people stupid enough to try invariably coming down with vicious vomiting and diarrhea, which probably goes a long way towards explaining their longevity as a species.

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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.[2] Coelacanths are fish and thus are related to the ancestors of tetrapods (amphibians, reptiles, mammals, and birds), though they evolved differently from the rhipidistian fishes (including lungfish). It was once thought that coelacanths were the closest fish ancestors to tetrapods, but DNA evidence has shown that lungfish are the closest ancestors.[3][4]

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 coealacanths 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 L. chalumnae (from the west Indian Ocean) and L. menadoensis (from Indonesia).

  • Latimeria chalumnae specimen with a diver in Indonesia.

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.
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References
  1. Tom Weller, Science Made Stupid
  2. 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.
  3. The African coelacanth genome provides insights into tetrapod evolution by Amemiya, Chris T. et al. (18 April 2013)Nature 496 (7445): 311–6.
  4. DNA Sequencing Reveals that Coelacanths Weren’t the Missing Link Between Sea and Land by Joseph Stromberg (April 17, 2013) Smithosnian.
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