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Crossopterigian and Coelacanth

In 1938 what was called a living fossil fish was discovered.

Crossopterigian are lobe-finned fish that lived during the Devonian, something like 360 million years ago or more. Crossopterigian were a fresh water fish which had well developed pectoral fins. For more information see http://www.abc.net.au/dinosaurs/fact_files/default.htm.

Coelacanth is a modern descendent. It has been observed in the Indian ocean off of East Africa and Indonesia. Here is a Web site which even has a virtual Coelacanth, http://www.dinofish.com/.

Crossopterigian was an amphibian which is now extinct. When the Coelacanth was discovered off the West coast of Madagascar in 1938 and for quite some time afterwards, it was considered that the long extinct Crossopterigian had been discovered as still alive and had not gone extinct after all. However, that has now been disclaimed and the Coelacanth is a fish descendant of the earlier Crossopterigian amphibian, not its survivors.

Coelacanths were fresh water carnivorous fish that weighed about 22 lbs (50 kg) and were up to 4 foot (1.5 meters) long, which evolved during the late Devonian period (360 to 408 MYBP). Coelacanths had a thick fleshy tail. However the interesting thing about Coelacanths was their two pairs of muscular fins that looked very much like four legs.

Coelacanths continued to exist for a very long period of time and were numerous during the Triassic period (208-245 MYBP). eventually Coelacanths were found in both marine and fresh water environments. When most dinosaurs became extinct, at the end of the Cretaceous period, about 65 MYBP, it was believed that Coelacanths also became extinct. However, a living specimen was found off the East coast of Africa, West of Madagascar in 1938. Since then a number of other Coelacanths have since been caught in the waters off of Indonesian and East Africa, proving that this hardy group still lives today in the depths of the Indian Ocean. Coelacanths have been called "fossil fish" and are extremely similar to its ancient ancestors from the Devonian level of material.

The following information comes from the American Museum of Natural History
Visit their website: http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Treasures/Coelacanth/coelacan.html?aa

Coelacanths are an ancient lineage of fish-like vertebrates that first appeared some 350 million years ago, about the time the first creatures emerged from sea to land. The fossil on view at the Museum, from the Santana Formation, in Brazil, is more than 100 million years old.
In terms of evolution, these ancient "fishes" are more closely related to land animals than to fish. Note the specimen's paired fins. They are lobe-like and actually have jointed bones, like arms and legs.

These creatures present a fascinating story of the ways in which our knowledge of the world is sometimes increased by happenstance. Until 1938 all coelacanths were considered to be extinct; we thought the last Coelacanth lived approximately 70 million years ago. In December of 1938, however, fishermen off the eastern coast of South Africa caught a living Coelacanth, like the one pictured here. It was so similar to its ancient relatives that it was called a "living fossil." For years after this serendipitous discovery, scientists searched for another living Coelacanth. Finally, off the Comoro Islands, north of Madagascar, they met with success. Since then, more than 200 specimens have been found, all in the same region.

In 1975 a scientist in the Museum's Department of Ichthyology helped dissect a Coelacanth. Inside were five fully formed babies, showing us that Coelacanth eggs hatch internally. Because of this method of reproduction, the Coelacanth cannot produce many eggs, and is able to brood only a few young. It is therefore extremely rare and vulnerable to overfishing. Conservation measures are now in place so that the Coelacanth can remain a living link to the ancient past.

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