Henry Sharpe / AMNH
In 2015, Deborah Shepherd returned to the website the place she and different volunteers had labored on a public fossil dig with members of the family. That’s when she noticed it: a fossil mendacity there, uncovered on the floor. Most folks wouldn’t have acknowledged it for what it was: It wasn’t a cranium, a leg bone, and even a partial jaw. It was simply a chunk of bone.
Shepherd instantly notified a park ranger. That ranger then notified the North Dakota Department of Mineral Resources. Her actions in the end led to the discovery of what scientists say is not solely a new species, however a completely new genus of mosasaur, a big marine predator from Late Cretaceous seas. Bite marks preserved on the fossil additionally recommend that it met its finish at the fingers—or somewhat enamel—of one other mosasaur.
Meet Jorgie the mosasaur
The new mosasaur was described Monday in the Bulletin of the American Museum of Natural History. Jǫrmungandr walhallaensis, or “Jorgie” for brief, is the identify advised by co-author Clint Boyd, and it’s steeped in Norse mythology. Jǫrmungandr is the identify of a sea serpent who circles the world with its physique, clasping its tail in its jaws.
Walhallaensis references Walhalla, North Dakota—a city near the fossil website the place this mosasaur was excavated. Walhalla is a reference to the nice corridor Valhǫll (Valhalla), the place Odin, the Norse god, resurrects lifeless troopers to rise in fight for battles brought on by Jǫrmungandr when it releases its tail (an occasion generally known as Ragnarǫk).
Mosasaurs have been most decidedly non-mythical, nonetheless. They have been monumental and toothy carnivores, some of which might attain lengths of roughly 15 meters (about 50 ft). Although solely aquatic, they wanted to floor to breathe air like in the present day’s whales. The earliest types had legs, indicating an historical migration from land to sea. And whereas a substantial quantity of mosasaurs have been excavated all through the world, we nonetheless have a lot to find out about these animals and their evolution.
What stays of Jorgie is an virtually full cranium, some of its ribs, and a quantity of its vertebrae. Unlike most different mosasaurs, this one preserves the bones inside the cranium that formed the mouth and are not often seen or found in different mosasaur specimens.
Bite marks on the bones point out a violent battle proper earlier than it died, resulting in a doubtlessly grotesque demise. A number of chew marks on the vertebrae present no indicators of therapeutic, which indicators their prevalence near, if not precisely, when Jorgie died roughly 80 million years in the past.
Those marks are outlined sufficient to find out the potential chew maker. The doable perpetrator? Another mosasaur. Worse, that particular set of bites could have led to the dismemberment of Jorgie, detaching one half of its physique from the different. Because Jorgie’s cranium has no chew marks, the group posits that its killer was consuming the decrease half of its physique, a doable motive so little of its physique has been found.
Found on the side of the road
What might need been an intensely dramatic scene hundreds of thousands of years in the past is in stark distinction to the comparatively mundane setting by which the bones have been found. The website of the public fossil dig is in a spot adjoining to a gravel road in a North Dakota state park. Boyd is the senior paleontologist for the North Dakota Geological Survey and curator of the North Dakota State Fossil Collection. He is additionally half of the group that organizes and leads the public digs.
“The rock is really soft there,” Boyd defined in a video interview. “It weathers really quickly. And since it’s right next to a road, it’s cut very steeply and is unstable.” As the rock crumbles, this exposes new fossils. “That’s the whole reason there’s a public fossil dig to begin with: to save the fossils that are otherwise going to be lost to collapsing [rocks].”
But how do you go from discovering a fossil to figuring out that it belongs to a new species and a new genus?
Lead creator Amelia Zietlow, whose dissertation focuses on mosasaurs, is a PhD candidate at the Richard Gilder Graduate School at the American Museum of Natural History in New York. In a video interview, she talked about that she has been requested which is most necessary in the choice to call a new species: its anatomy, or a fossil’s location in the sediment (the stratigraphy), which might point out when the animal existed.
“It has to be anatomy,” Zietlow said. “That is what taxonomy is. You’re describing the animal, and the animal is based on the anatomy. For determining what species something is, it doesn’t really matter when it lives or what the environment was like, although those are certainly important factors for other biological questions.”