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Paleontologists Uncover Fossils Of Prehistoric Rodents In Central Oregon


Beavers in Oregon today typically weight 30 to 40 pounds. Josh Samuels estimates Microtheriomys brevirhinus, the new species discovered in Central Oregon weighed only 1 to 2 pounds.

Beavers in Oregon today typically weight 30 to 40 pounds. Josh Samuels estimates Microtheriomys brevirhinus, the new species discovered in Central Oregon weighed only 1 to 2 pounds.

Courtesy Dr. Joshua Samuels

Imagine a tiny beaver that could fit into both of your hands. Twenty-eight million years ago, such a species lived in Oregon. Paleontologists have unearthed fossils of 10 newly-discovered species in Central Oregon.

“I could recognize that it was a beaver based on the structures of the teeth, but it’s much smaller any other beavers we have here,” says Dr. Joshua Samuels, museum curator at John Day Fossil Beds. He discovered the beaver skull along with a colleague. “I really immediately knew that it was something different.”

Samuels says that the beaver and other fossils provide important indicators about the nature and climate of the prehistoric Pacific Northwest.

The prehistoric beaver skull found near the John Day Fossil Beds in Central Oregon.

The prehistoric beaver skull found near the John Day Fossil Beds in Central Oregon.

Courtesy Dr. Joshua Samuels

“They give us a better picture of what Oregon’s past was like,” says Samuels. “They help to fill in information for what was living here and what environmental conditions were like.

During the Oligocene Period, 33.9 to 23 million years ago, Oregon was a deciduous forest.

“Like you would see on the East Coast today — maple, oak, birch, and some conifers,” says Samuels.

The rodent fossils provide clues to how Oregon’s environment came to include more open space and prairies.

Samuels’ team also unearthed fossils similar to the modern pocket mouse, one of the most abundant mammals in the western United States today.

“The new species we describe is one of the earliest of these species,” says Samuels. “This is a species that is 23 million years old. But it really looks very much like a pocket mouse today.”

Many of the unearthed fossil species are likely relatives of existing animals. Samuels says that’s probably the case for Microtheriomys brevirhinus — the tiny, prehistoric beaver.

Fossils of ancient relative of modern mice.

Fossils of ancient relative of modern mice.

Courtesy Dr. Joshua Samuels

The 10 new species were reported in a study authored by Samuels and Dr. William Korth, and published in the “Annals of Carnegie Museum.”

“There’s a lot of excitement when we can take it and compare it to other things and say this really is something new, something we’ve never seen before,” says Samuels.

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