John Zancanella, coordinator of the U.S. Bureau of Land Management's paleontology program in Prineville, discovered the ancient teeth on an eroded, rolling stretch of BLM land.

Beavers don't get tooth decay thanks to this iron, which renders the teeth harder and more resistant to acid attack, and the fact that noshing on wood helps keep their choppers clean.

"A beaver's teeth are chemically different from our teeth, not structurally different," said Derk Joester. By Brooks Hays A North American beaver taking down a tree.