Please excuse the long post and multiple images, but I observed this industrious beetle over the course of two hours around sunset in the Mojave desert and was fascinated by the behavior. It was digging into some hard-packed sand along a steep wash embankment. I assume that it was an adult creating a breeding burrow - possibly a teneb?? Any help with ID would be greatly appreciated.

Briefly, the beetle went through a repetitive series of movements - first digging into the sand with front legs (and ? mouthparts), then expelling the accumulated sand behind it with the hind legs, and then occasionally turning around and "bulldozing" the sand away from the burrow entrance with it's head. It repeated this series of digging movements for at least two hours, creating a tunnel that was several times it's length, apparently without a break. I had to turn in before I could see the tunnel completed, but I took a photo of the now-plugged tunnel entrance the next morning. I've tried to demonstrate these behaviors with this series of photos. Thanks in advance for any help with the ID or comments on the behavior. Although I didn't witness any egg-laying, I'm wondering if this was an adult female laying eggs in damp sand?