80 million-year-old Walhalla dinosaur fossil, named for the town, is a new species of aquatic predator

Posted 12/01/23 (Fri)

By Delaney Otto

November 15, 2023

WALHALLA, N.D. — Researchers who uncovered a new genus and species of mosasaur — an ancient, carnivorous aquatic lizard — in the Pembina Gorge north of Walhalla are hopeful the discovery will fill gaps in scientists' understanding of the creature's evolution.

This new specimen, currently housed in the state fossil collection in Bismarck, was originally found in 2015, though it took years of repeat excavations and cleaning to uncover all of its pieces: most of its skull with an attached neck. Clint Boyd, a senior paleontologist for the North Dakota Geological Survey’s paleontology program, said it was evident as they examined the bones that this particular animal hadn’t been seen before.

“As we compared it to the different known species, we realized this thing doesn’t look like any of those ones,” he said.

The paper identifying the mosasaur officially named the new dinosaur Jormungandr walhallaensis (pronounced yore-mung-gander walhalla-ehn-sis). Its species name is a clear nod to Walhalla, its place of origin, and its genus name comes from the sea serpent of Norse mythology by the same name, also referred to as the World Serpent.

Jormungandr walhallaensis is a type of mosasaur, which could be found across the globe during the Late Cretaceous period, according to the study written about the new genus and species . This particular type of lizard is considered by Boyd and others involved in the study as an evolutionary stepping stone between the genuses Clidastes and Mosasaurus. Some of its bones resemble the former, others the latter, and some appear to be a mixture between the two.

“Previously we knew that those two belonged to the same larger group, but they were not each other’s closest relatives,” said Amelia Zietlow, a Ph.D. candidate from the Richard Gilder Graduate School at the American Museum of Natural History. “And now we have this weirdo that appears to bridge that gap.”

Zietlow, who was brought onto the study by Boyd, said she didn’t expect to find a new species so soon into her studies.

“It’s really, really cool,” she said. “I’m relatively new in the field, I’m still a grad student. I’ve only really been working on paleo stuff since 2019, so it’s something that I hoped would happen eventually. But the fact that it happened so early in my career is pretty exciting.”

Jormungandr’s story begins in 2015, when an individual was showing their family the spot in the Pembina Gorge where they had previously gone on public fossil digs with North Dakota’s paleontology program. That’s when they spotted a bone on the surface of the ground and alerted a park ranger, who picked up the piece so it wouldn’t be lost.

Boyd and his team arrived at the area a few weeks later for a dig and began working on the area where the first bone had been found. Most of the skull was right below the surface, though it took multiple years to unearth all the bones the team could find, as digs only last for 10 to 12 days each summer. Boyd said the last time he and his team dug in the area was in 2018, when they decided they had found all they could.

The study kicked off in 2021 after all the soft and brittle bones had been thoroughly cleaned. Boyd initially guessed this specimen could be a new species, as the rock it came from dated to around 80 million years ago and wasn’t often worked on by paleontologists.

Each piece of Jormungandr walhallaensis was scanned so Zietlow could view them from New York, though she did travel to North Dakota for a few days to sit with the bones up close, looking through references of other species to note the similarities and differences between the Walhalla specimen and already-documented mosasaurs.

Boyd wasn’t quite surprised by the fossil being a new species, but it was an exciting discovery that it was a whole new genus.

“We went through quite a lot of the research before we figured out it was going to be a new genus as well,” he said. “That was very exciting for us.”

There’s also the mystery of what Boyd hypothesizes to be bite marks on the lower vertebrae, right where the skeleton stops. The bones are going to be CT scanned to see if these are indeed bite marks, whether they happened before or after Jormungandr died, as well as what might have bitten it.

Something that both Boyd and Zietlow emphasized was how important it was that the person who found Jormungandr reported it.

“We ask people to (report) so that piece could be saved,” Boyd said. “Not only does that mean that the piece they found got saved, but as a result we ended up finding an entirely new species that had never been seen before. If somebody had just picked up that loose piece on the surface and taken it home and never said anything, we may have never found the rest of the specimen, or it might have been so weathered out by the time we did it couldn’t be saved. … I think that’s a really great story of not just paleontologists, but everyday North Dakotans working to save our history and to learn more about our past.”