The Fallen Skull

This year our Montana expedition could be classified as a grab and dash operation.  Having discovered a what appeared to be a Triceratops prorsus skull in 2016, and explored with a few test pits in 2017, we returned this year with permit in hand to determine just how good the Triceratops site is.  Turns out the skull is every paleontologists dream, it appears to be a complete skull nose to frill with no pre- or post burial damage to speak of and potentially some distortion on one side.

Since only a tiny portion of the total skull had been exposed on the surface when I stumbled upon it two summers ago (just 3” of frill margin exposed, the very edge!) and the rest of the skull was completely buried beneath sediment, the entire specimen was completely undamaged by modern erosion.  Moreover, the skull is entombed in sandstone, which preserves fossils in three dimensions, so there is less distortion than one would find in a fossil preserved in mudstone. Our number one goal this trip is simple, quarry clean and quickly, and get this beauty packaged up for transport via helicopter in just ten days’ time.  Two days of driving and the NC Museum of Natural Sciences will have its first Triceratops skull for exhibition and study.

Triceratops skull in side view after a few days of quarrying.

We started day 1 by opening a quarry, digging through the overburden down to the bone layer–a full day of picking and shoveling. As we dug down through the layers, we noticed a slick-n-side revealing itself, a smooth sloping surface cutting directly through the middle of our quarry near the edge of the skull.  It kept growing, eventually becoming over a meter in height and we then determined it was a fault and that the sediment layers entombing the Triceratops skull had dropped about a meter relative to the bone layers behind.  This was great news as it meant to reach the rest of the bone layer we didn’t have to dig all the way down to the level of the skull, and that if present, the bones at the back of the quarry would be a meter higher up.

A fault reveals itself (smooth surface) behind the skull.  The skull dropped about a meter relative to the rest of the bone layer (to the right of image).

Just as we were trenching around the backside of the skull, we uncovered a gorgeous quadrate (bone from the back of the skull connecting the skull to the lower jaw).  Of course, it was resting directly in our trench (the most common law of quarrying).  Nonetheless, it is a real beauty with perfect undamaged margins of fine, thin bone.  This is truly a gorgeous specimen.

Surprise!  There’s a quadrate in our trench!
Some lovely leaf impressions underneath the skull.