Introducing...the oldest beaver teeth in America
story by Christina Lilienthal
art by Matt Christenson
On a cool, sunny winter day driving to the John Day Fossil Beds, BLM archaeologist John Zancanella made a routine stop near Dayville, Oregon. John was taking a trip to meet Dr. Josh Samuels - new paleontologist for the John Day Fossil Beds National Monument - and had planned a little extra time to check for fossils along the way.
Zancanella has found a number of fossils in this area - to include an extinct but fairly common beaver named Dipoides. But seasonal freezing and thawing of soil in eastern Oregon regularly draws new fossil fragments to surface. So you never know what you might find.
What first struck John was a couple of new teeth lying on the ground. He recognized them as rodent teeth, possibly beaver, but larger than any mountain beaver teeth he'd ever found before. Erosion deteriorates fossils, so John carefully collected and documented these specimens for curation and study. Excited, he got back in his car looking forward to sharing his new discovery with Samuels.
Unbeknownst to Zancanella, Josh Samuels' specialty just happens to be beaver evolution. After brief introductions, they looked at Zancanella's find. Samuels recognized them immediately - the teeth were from a descendant of what is considered to be a "modern" beaver, Castor, found in North America today.
A bombardment of questions ensued.
First, where were the teeth found? Zancanella retrieved them between tuffs of hardened volcanic ash, below the youngest and the oldest tuffs. And the volcanic ash around them is datable.
Right away, Samuels realized the significance of these teeth. Based on the age of the neighboring tuffs, he knew Zancanella had unearthed the oldest-known discovery of this type of beaver in North America by nearly 2 million years. That day the two headed right back to the fossil site where Samuels found another sliver matching one of Zancanella's teeth.
MARCH OF THE BEAVERS
The sequence of dateable volcanic rock layers in the John Day Basin allows for the study of climate and evolutionary change in Oregon. Over time, the climate in this area has become cooler and drier, and the habitat has changed from a warm, wet subtropical forest to the shrub steppe it is today. And thanks to data previously captured from this area, these beaver teeth were found in the Rattlesnake Formation which is known to be from about seven million years ago.
Looking back to the past, the earliest "true" beaver as we think of them today comes from Germany about 10 to 12 million years ago. These beavers then spread across Asia and eventually crossed the Bering Land Bridge to North America. Zancanella's new finding helps resolve when beavers actually arrived in North America and when the two current living species - the North American Castor canadensis and Eurasian Castor fiber - ultimately diverged.
PUTTING FOSSILS TO BED
The National Park Service's John Day Fossil Beds National Monument (JODA) and the Oregon/Washington BLM are parties to a long-standing and ongoing interagency agreement to jointly manage paleontological resources on Federal lands. The Thomas Condon Paleontology Center at JODA serves as the main repository for specimens and records of paleontological resources found on BLM lands that fall within the scope of collections for the Monument. Each specimen found is carefully collected, identified, cataloged, and stored in environmentally-controlled conditions. The JODA collection preserves animal and plant fossils from the Cenozoic Period, including specimens from the last 50 million years of life on earth.
Paleontologists have been studying the John Day Basin for well over 100 years, but there is still much to learn about Oregon's past. John Day Fossil Beds National Monument includes many of the best studied sites, but the vast majority of fossil localities are found on adjacent land administered by the BLM. Collaboration between Federal agencies has allowed all scientists to fulfill their mission by preserving important resources for future generations while conducting important scientific research to better understand changes in plants, animals and the environment.
BEAVERS VS. DUCKS?
Over the course of a year, Dr. Joshua Samuels and John Zancanella have co-authored a peer reviewed paper about this discovery that has been published in the current issue of the Journal of Paleontology. They have provided evidence of the oldest documented beaver in North America. Previously, the oldest known records were from Nebraska, California, and northern Oregon - and they only dated to around five million years of age. The "new" fossil teeth found near Dayville, Oregon, are almost identical to living beaver teeth, showing that the animal has changed very little in the last seven million years.
It is fitting that the earliest known beavers in North America have been found in Oregon. Long considered the state animal, the beaver is also the mascot of Oregon State University. Perhaps this will inspire their rivals, University of Oregon, to help John find evidence of a prehistoric duck…
For more information about the BLM's Cultural and Archaeological Programs, please visit us online.