290-mln-yr old Frog-amander fossil might be missing link in amphibian family tree

May 22nd, 2008 - 12:18 pm ICT by admin  

Washington, May 22 (ANI): A 290 million year old fossil, dubbed as Frog-amander, has been described by scientists as possibly being an evolutionary missing link in the amphibian family tree.

First discovered in Texas, US, by a paleontologist with the Smithsonian Institution in the mid-1990s, it was rediscovered in the collections of the National Museum of Natural History in Washington, D.C., in 2004.

The examination and detailed description of the fossil, Gerobatrachus hottoni (meaning Hottons elder frog), proves the previously disputed fact that some modern amphibians, frogs and salamanders evolved from one ancient amphibian group called temnospondyls.

The dispute arose because of a lack of transitional forms. This fossil seals the gap, said Jason Anderson, assistant professor, University of Calgary Faculty of Veterinary Medicine and lead scientist in the study.

The Gerobatrachus fossil provides a much fuller understanding of the origin and evolution of modern amphibians.

The skull, backbone and teeth of Gerobatrachus have a mixture of frog and salamander features, thus the name frog-amander given to the species by scientists.

The fossil has two fused bones in the ankle, which is normally only seen in salamanders, and a very large tympanic ear (ear drum).

It also has a lightly built and wide skull similar to that of a frog. Its backbone is exactly intermediate in number between the modern frogs and salamanders and more primitive amphibians.

The new fossil also addresses a controversy over molecular clock estimates, or the general time salamanders and frogs evolved into two distinct groups.

With this new data our best estimate indicates that frogs and salamanders separated from each other sometime between 240 and 275 million years ago, much more recently than previous molecular data had suggested, said Robert Reisz, professor, University of Toronto Mississauga and second author on the paper. (ANI)

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