"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.