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Rodent population booms in Fossil Beds area

Blue Mountain Eagle

Published on May 28, 2015 12:26PM

KIMBERLY – Paleontologists are celebrating a bonanza of prehistoric rodent finds at the John Day Fossil Beds National Monument and nearby Bureau of Land Management land.

The discovery of 10 new prehistoric species in the area was reported in a study published in the current “Annals of Carnegie Museum.”

The study, by scientists Joshua Samuels of the Fossil Beds and William Korth of the Carnegie Museum of Natural History, looked at 21 species in all – new and previously undocumented.

The new ones include:

• Microtheriomys brevirhinus, an early beaver that may be the distant ancestor of today’s beavers.

• Miosciurus covensis, a dwarf tree squirrel, smaller than any living in North America today.

• Bursagnathus aterosseus, a primitive pocket mouse, possibly an ancestor of today’s desert mice.

• Plesiosminthus fremdi, a birch mouse, named for retired John Day Fossil Beds paleontologist Ted Fremd.

“This study fills some substantial gaps in our knowledge of past faunas, specifically smaller mammals. Some of the new species are really interesting in their own right, and will ultimately help improve our understanding of the evolution of beavers and pocket mice,” said Samuels. “These finds show that despite this area being studied for well over 100 years, new discoveries continue to be made.

“Each new discovery helps to give us a fuller picture of Oregon’s past.”

The John Day Basin contains one of most complete fossil records on Earth, spanning nearly 50 million years of time. The beds reveal the history of ancient ecosystems, climate change and plant and animal evolution during what is known as the Age of Mammals.

Officials say the John Day formation has a diversity of fauna, including more than 100 species – saber-toothed nimravids, early dogs, three-toed horses and giant “hell pigs.”

The new rodents were collected through decades of collaborative work throughout the John Day Basin by paleontologists from the Fossil Beds, BLM. University of California at Berkeley, and University of Washington.

“The National Park Service and BLM have worked together to manage fossil resources in Oregon under an agreement for nearly 30 years,” said Shelley Hall, John Day Fossil Beds National Monument superintendent. “The collaboration between federal agencies has allowed each agency to fulfill their mission of preserving resources for future generations while facilitating important scientific research.”


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