Almost every time I read about Coelocanth as a living fossil (I know, not the best term) the implication seems to be that this fish type has remained unchanged since its Devonian times. There are many examples of structures and functions being reinvented (calcite eyes in Trilobites and Brittlestars, color vision, and a hundred examples of yours). Has anyone looked into how old this fish type might actually be as a separate entity ? I assume no good fossil record, but there are genetics and biochemisty. Perhaps lobe fins are another reinvention. Perhaps this is a "fish" question, but I pose it here because coelocanth has been discussed, I think, at this site.
Thank you for this site and your help
As you suggest, genetic approaches have shown that the coelocanth really is an ancient lineage. The coelocanth and the lung fish are sister groups that separated from the rest of the tetrapods about 400 million years ago. These data support the original suggestions made from comparisons of well-preserved fossils that living coelacanths were morphologically so similar to their fossil forebears that they were the same animal.
The coelocanth and the lung fish are sister groups that separated from the rest of the tetrapods about 400 million years ago.
Interesting: my textbook (Vertebrate Life, 7th ed. Pough, et al., 2005) has the lungfish as the sister group to tetrapods with coelecanths as the outgroup. Are there more recent data that group the lungfish and coelocanths together? (Note: I am not suggesting that you are wrong; I have been teaching it this way for about two years now, but it is not my area of expertise).
Brent, it's not my field either, but I used to teach it to undergraduates so still browse occasionally! The catchingly titled paper below is the most recent in a line of similar papers which toss the sister group question back and forth, but I'm not qualified to come down one way or another. In relation to 'bede's' question, though, the coelacanth is a living fish which appears to be largely unchanged over a very long time.
Shan & Gras (2011) 43 genes support the lungfish-coelacanth grouping related to the closest living relative of tetrapods with the Bayesian method under the coalescence model. BMC Research Notes 4: 49. doi:10.1186/1756-0500-4-49
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Paolo Viscardi
Reetika Suri
A. Brent Richards
