"Frog-amander" Fossil May Be Amphibian Missing Link

Anne Casselman
for National Geographic News
May 21, 2008

A new fossil find may be an evolutionary missing link in the amphibian family tree, scientists say.

The 290-million-year-old fossil was first collected in Texas 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.

"It had an overall amphibian gestalt. … You know, kind of a froggy slamander-y sort of look," said Jason Anderson, a comparative biologist at the University of Calgary, Canada, who led a new analysis of the fossil.

"But also I recognized some of the archaic features too, and I thought that this would be a critical piece of evidence in trying to work out the origins of modern amphibians."

Dubbed Gerobatrachus hottoni, the animal looked somewhat like a salamander with a stubby tail and froglike ears.

"So it's kind of a frogamander, if you will," said Anderson.

Filling in Fossil Gap

Gerobatrachus fits into a noted gap in the fossil record of amphibians—between one of the groups hypothesized to be ancestors of modern amphibians, called temnospondyls, and the earliest frogs and salamanders.

(See related photo: "Pre-Dino Amphibian Body Casts Found" [October 30, 2007].)

"It pretty convincingly settles the question [that the] frog and salamander shared origins from the same fossil group," Anderson said.

John Bolt, curator for fossil amphibians and reptiles at The Field Museum in Chicago Illinois, who was not involved in the study, said, "The most astonishing thing to me about this study is that this animal is far more froglike than I would ever have expected from its age."

"Nothing this nonprimitive has ever been described from this age. It's just amazing."

Continued on Next Page >>




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