Paleocastor is the a beaver from around 35 million years ago. It was about the size of a muskrat and is believed to have lived in family groups. They were a member of the once very large “Castorid” family of which now only two survive (canadensis and fiber). Like many of their relatives they started as a burrowing terrestrial mammal – instead of a water based one. In fact it was these burrows that lead to their fame.

The Daimonhelix, confused researchers for years until it was understood that it was dug by the incisors of this early beaver making a burrow for its family, which like today’s beavers was based on a K-structure rather than an R-structure. (Meaning rather than have as many off spring as possible in the hopes that some survived, paleocastor had a few youngsters and spent time making sure they knew how to dig their own burrows, find food etc before sending them off in the world.)

Well in honor of our national parks 100 birthday, a paleocastor fossil is coming home.

A fossil returns home

A unique fossil came home to Agate Fossil Beds National Monument Saturday as part of the 100th anniversary celebrations of the National Park Service. The return of the Palaeocastor fossil, which was excavated in 2015, brought a close to a unique chapter in the history of palaeocastor fossils and Daemonelix burrows at Agate.

Palaeocastor homes and Daemonelix burrows were some part of what drew paleontologists to the area in the late 1800s. Fossilized mammals from the Miocene Epoch, 23 million to 5.3 million years ago led to the creation of Agate in 1965.

A cranium and part of the lower jaw of the palaeocastor was first documented in 2003. When erosion had destroyed part of the cranium, paleontologists knew the rest needed to be saved. However, this palaeocastor was different. Other burrows have bones in the lodge, Welsh said.
I’m glad it’s someone one else’s job to recognize that pile of scraps as paleocastor because I never would! Some readers might remember back an era ago when we discussed the confusion of these burrows with the little corkscrew horn in the iceage animation. What’s funny to me is to think how different these beavers were in so many ways, and then to realize that just like their modern flat tail cousins, it was their work products that got them noticed.