May 22, 2008

Frogamander Missing Link For Amphibian Fossil Record

Researchers have discovered the 290 million-year-old fossil of a so-called "frogamander," which could finally set the record straight in a long-lived debate over amphibian ancestry.

Scientists have been unable to fill in some gaps in the fossil record showing the transformation of modern amphibians such as frogs, salamanders and caecilians.

The University of Calgary researchers said the fossil Gerobatrachus hottoni, or elderly frog, will add solid evidence to the debate.

"It's a missing link that falls right between where the fossil record of the extinct form and the fossil record for the modern form begins," said Jason Anderson of the University of Calgary, who led the study.

"It's a perfect little frogamander," he said.

The fossil was discovered in Texas in 1955 by a group from the Smithsonian Institution.

Just as the name implies, the fossil Gerobatrachus shows a combination of frog and salamander features "“ fused ankle bones usually seen only in salamanders, a wide frog-like skull, and a backbone that appears to come from both.

Writing in the journal Nature, researchers said the fossil suggests that modern amphibians may have come from two groups, with frogs and salamanders related to an ancient amphibian known as a temnospondyl, and worm-like caecilians more closely related to the lepospondyls, another group of ancient amphibians.

"Frogs and salamanders share a common ancestor that is fairly removed from the origin of caecilians," Anderson said.

"The fossil itself is almost perfectly complete," Anderson said.

"It died on its back. Its legs and arms were curled up on its belly and it's that part that weathered away."

While scientific opinion moves slowly, Anderson thinks the find will confirm the prevailing opinion that frogs and salamanders share a more modern ancestor.

"I think they (scientists) will be very happy with this as a resolution," he said.


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