The fossil was unearthed by paleontologists at the University of Oregon and named the extinct species of beaver Microtheriomys brevirhinus.
The remains of the beaver were found near the John Day Fossil Beds National Monument, in Kimberly, Oregon.
The fossil consists of the animal’s skull and teeth.
The researchers detailed their findings in a paper published in the journal Annals of Carnegie Museum.
In their study, they write that the prehistoric beaver was two times smaller than the modern, living species of beaver, its close relative.
Joshua Samuels, an expert in paleontology at the John Day Monument and one of the lead authors of the study, explained that the recently discovered beaver was direct ancestor to the species of beaver that left Asia and crossed the Bering land bridge on its way to North America.
Samuels said that they were able to determine the fossil’s age by analyzing the layers of volcanic ash in which it was trapped for millions of years.
The paleontologist explained that the area where prehistoric beaver fossils were discovered is covered in badlands.
When these lands get wet because of the rain or snow, or if the temperatures change from cold to hot, the claystone shrinks and swells, pushing the bones out of the ground.
When the rocks break apart, the fossils come out and are left exposed.
Samuels said that the recently discovered fossil came out of the ground in which it had been preserved for millions of years.
Samantha Hopkins, paleontologist at the University of Oregon, stated that it’s very exciting to be part of the team that gets to analyze the beaver fossil.
She said although there isn’t much diversity in beaver species living today, there are hundreds of beaver fossils that belong to many species and are part of the record of the Northern Hemisphere.
Hopkins believes that scientists need to better understand the diversity of the beaver species because it plays an important part in the way mammals have evolved over the past 40 million years.
The recently discovered fossil of prehistoric beaver adds up to almost 100 species of mammals that have been found close to the John Day Fossil Beds National Monument, the researcher said.
Image Source: telegraph