Researchers at the University of Oregon (UO) unearthed a fossil apparently belonging to a 28 million year old beaver.
According to the Associated Press, the researchers named the species Microtheriomys brevirhinus. They found the animal's skull and teeth not far from the John Day Fossil Beds National Monument in Kimberly, Ore.
Their study published in the journal Annals of Carnegie Museum, the scientists determined the ancient beaver was about half the size of its modern descendant. Joshua Samuels, a paleontologist at the John Day Monument, told the AP the ancient beaver was an ancestor to the ones that crossed the Bering land bridge from Asia to get to North America.
He said the researchers were able to age the fossil due to the layers of volcanic ash it was embedded in.
"We've got badlands exposures here," Samuels told the AP. "As they get wet, whenever it rains or snows and the temperature heats or cools, the claystone these things are in shrinks and swells. The bones are pushed out. The rock breaks apart. The fossils are exposed. This one just came out of the ground it was preserved in."
Samantha Hopkins, a paleontologist at UO, said she was excited for the chance to analyze the fossil.
"While there is relatively little castorid (beaver species) diversity today, there are hundreds of species (many of which are really important members of their faunal communities) in the fossil record of the Northern Hemisphere," she told the AP, "and a better understanding of their diversity and evolutionary relationships has a lot to tell us about processes driving mammalian evolution over the last 40 million years."
