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A New Living Fossil!

by TFH Magazine on August 19, 2011 at 12:23 pm

by David E. Boruchowitz

More than 70 years ago, the discovery of a living coelacanth stunned the scientific world. Thought to have gone extinct in the late Cretaceous, the living fish was known only to local fishermen. More recently a second species of coelacanth was identified. Coelacanths, however, were well known from the fossil record, as was their relationship to lobefin fishes and tetrapods (amphibians, reptiles, birds, and mammals).

Yesterday (May 18) scientists announced an astounding coelacanth-like discovery. The animal in question is a marine cave-dwelling eel that is being called a living fossil, although its line is not represented in the known fossil record. Described as Protoanguilla palau, the fish has many primitive features, but this fish also has gill rakers, a trait of bony fishes previously unknown in any fossil or living eel species. DNA analysis confirmed that this species is an eel, in the order Anguilliformes, but it is so different that it has been given a family of its own, Protoanguillidae.

This animal’s characteristics may be more significant than its not being extinct. What I’m saying is that finding an evolutionary line parallel to that of all other fossil and living eel species is incredible, and just finding fossils of this lineage would have been a great boon. Having an extant species is icing on an already very sweet cake.

As just one example, the absence of gill rakers in all other eels, both fossil and living, suggests that they evolved after the split of Anguilliformes from other bony fish lineages. This new eel suggests that ancient proto-eels may have shared this feature with other lineages but that at some point close after the Protoanguillidae split off, they lost them. Whatever turns out to be the case, this fish, dating back to a time when dinosaurs were just starting their reign, has stayed hidden for a very long time!

Eels, especially moray eels, have great appeal to many aquarists. Their morphological, behavioral, and reproductive traits are unusual and intriguing. In fact, the breeding saga of the common eel is nothing short of amazing. All American and European eels, after many years in freshwater habitats on the two continents, journey to the Sargasso Sea, where they spawn and die. The juveniles slowly make their way north, heading either to North America or to Europe, where they reside until they are ready to spawn.

It’s wonderful to have a fascinating new piece to the great puzzle of life that biologists are slowly putting together. There are many online sites you can enjoy if you’d like to read more about this eel try:

Posted in Aquatic News and David E. Boruchowitz by TFH Magazine on August 19th, 2011 at 12:23 pm.

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