Walhalla's Sea Snake: Welcome Jormungandr!

Believe it or not, I don't spend all of my time in the field (though it still does tend to be A LOT). In the winter and spring I have time to work on some fossils we find during the year, as well as work on projects for other museums. This past spring, Dr. Clint Boyd approached us about restoring a brand new mosasaur that he and a crew were describing from northeastern North Dakota. He called the critter "Eustace", nicknamed after the BEST character from the Cartoon Network classic "Courage the Cowardly Dog".

Eustace is famous for various disagreements

The specimen was found in the Pembina member of the Pierre Shale and an underlying bentonite was dated to 80 million years old. This is pretty similar in age to our "Walker" Mosasaurus specimen that we excavated from Western Kansas in 2015. I suspected we were in for a very fun project, and something that we at TPI are very capable of doing well.

Walker's reconstructed skeleton

The first step was getting the scan files of the specimen sent over and opened up in the computer. The specimen was fairly complete but missing a few bones. Evan Sonnenberg and I teamed up to reassemble the parts, and remove some of the distortion to make the individual elements fit back together like before they were crushed by 80 million years of rock and geologic processes. Some elements were completed using mirror images of bones from the opposite side of the skull in order to keep Eustace as Eustace as possible. 

Eustace's skull (right) and after restoration (left)

Once that part was completed, we used mosasaur specimens from our digital bone bank to come up with plausible shapes for the bones that were completely missing. When working on the parietal/braincase, lead author Amelia Zietlow kept urging us to make it more Clidastes-ey in overall appearance. And indeed, the paper that came out today does make a case for the new mosasaur being very closely related to Clidastes. Amelia and crew decided to name the specimen Jormungander walhallensis, which is a pretty clever name. The species name indicated it came from near Walhalla, ND, while the genus name plays off of the Norse mythology of the place name, with the name shared with the legendary snake that ends the world in the sagas. 

Once all the parts were there, we printed out two copies of the skull at full size so that they could go on display in museums in North Dakota. While not a huge mosasaur like the Bunker Tylosaurus, the skulls still had to be printed in pieces that were later assembled.

Parts for the top of the skull

Top of skull assembled

Easy enough! Lastly the specimens needed to be painted mounted. There's an external steel armature under the skull and each lower jaw on the copies so that the parts can be removed for closer inspection. One Easter egg that we included in the mount was that each base is a silhouette of Eustace's skull as seen from above. BTW the mini skulls were sent to the authors so they could evaluate it while finishing the manuscript.

The two reproductions were sent to North Dakota this June. One is on display at the Walhalla Library, which is nice having it on display so close to where the original specimen was discovered. The second is due to go on display at the Pembina State Museum in the near future.

Infected tails do it better

Sometimes you work on a fossil and just think "oooh, that had to hurt". This tail from a pretty large Clidastes from the upper Niobrara chalk is fairly boring when viewed from afar. Up close though something just doesn't look right.

Yep, pretty boring

Of the 45 bones, 23 are pathological, with 17 of them fused at the centrum in 5 separate masses. All of these bones lack transverse processes, so they come from the lower lobe of Clidastes' bifurcated tail fin: a bit of dangling flesh that might make for a tasty morsel for a predator.

I think this mass used to be 8 separate vertebrae, based on the number of chevrons

The bones, though mostly healed, show bone growth consistent with a long infection. As the tail was the primary means of locomotion/propulsion for mosasaurs, this injury must have been very painful for a very long time for this mosasaur.

3 verts become one

Fused verts, and centra with vertical scars

Fall fieldwork!

There's nothing quite like a nice October day in the Niobrara chalk. Lots of hiking, fresh air, and occasionally a few fossils.

Scrappy Cimolichthys verts in the outcrop

Though the puropse of this past 2 1/2 day trip was primarily for scouting, we did return with a few jackets of specimens, including a nice Ichthyodectes tail from the lower chalk and part of a giant Clidastes from the upper chalk. We'll be returning very soon to recover the rest of the Clidastes, as well as a new Nyctosaurus specimen I discovered on Friday (more on that later), and possibly the Pentanogmius I located, or one of the 3 xiphs I stumbled across. It's good to have so many choices.

Mike evaluating a Xiphactinus skull

Interesting thing about the Clidastes. The tail is chock-full of pathological vertebrae, from what looks to be an old infected bite wound. No clue yet as to whether the bite was from a shark or another mosasaur, however from all the intraspecific damage we see on other specimens, I wouldn't doubt it was the result of Clidastes-on-Clidastes violence.

Ouch! Most certainly a grumpy mosasaur

Meet Tony II!

Well, field season started off with a bang this year. The little mosasaur snout I found in late April turned out to be a nearly complete specimen of Clidastes c.f. moorevillensis, which isn't really supposed to be in the chalk. The critter measures 4.8m long (16 feet), and is so well preserved that it retains cartilage in the ear, sternum, sternal ribs and above the scapulas.
Above, Mike Triebold uses a chainsaw with a special blade to separate the block away from the outcrop prior to jacketing. This chalk was the hardest we've ever encounterred in nearly 3 decades of collecting in the Niobrara.

The site as seen from the top of an adjacent bluff. Luckily we could drive up to the site to dropp off air compressors and generators!

Below is the prepared front half of the animal. 45cm (18 inches) of backbone was lost in the mid dorsal section due to erosion years ago. The tail section was taken out in another large jacket. Come see the specimen, now on display in our marine hall at the RMDRC!