Fossil Friday!

This week's Fossil Friday was a bit of a shocker to me. Looking at the enormous jaw and terrifying teeth, I thought for sure this was some sort of gnarly reptile that would tear you limb from limb, given half a chance.

But no! Upon further investigation, this is the jaw of a mammal dating back to the Eocene. Though common in what is now California, this specimen was found in Oregon.

Any ideas as to what genus this lower jaw came from?