(SPENCER G. LUCAS ~ New Mexico Museum of Natural History and Science)
Researchers found the imprints in sandstone rocks collected in eastern Pennsylvania decades ago and stored in the museum in Reading, Pa. The body impressions of the salamanderlike creatures are estimated to be 330 million years old, or about 100 million years before the first dinosaurs appeared.
Many ancient footprints have been found, but a full-body animal impression is unusual. The three impressions show the foot-long temnospondyls had webbed feet and smooth skin similar to modern-day amphibians, rather than armored bodies.
"The most remarkable thing about these is they exist at all. This is a very rare preservation," said John Bolt, curator of fossil amphibians and reptiles at The Field Museum in Chicago.
Details were being presented Tuesday in Denver at the annual meeting of the Geological Society of America.
"They're really some of the oldest body imprints of land-living amphibians," said Spencer G. Lucas of the New Mexico Museum of Natural History and Science, who was making the presentation.
"They show you what the shape of the body was, they show you what the texture of the skin was like," Lucas said. "These are things we don't know from bones. They're giving us new information about the anatomy of these long-extinct amphibians."
The fossil could indicate social behavior or even courtship, Lucas speculated, or the impressions also could have been made at different times.
"The real question is why do you have three close together on a rock," he said.
David Fillmore, who was doing postgraduate work with Kutztown University geology professor Edward Simpson, found the impressions two years ago when the two were studying Mauch Chunk Formation footprints in a fossil collection at Pennsylvania's Reading Public Museum.
"We looked at each other and were speechless. It's way beyond anything we could imagine finding," Fillmore said.