Henry Sharp / AMNH
In 2015, Deborah Shepherd returned to the field where she was working with other volunteers. public fossil excavation With the family. That’s when she saw it. It turned out that there were fossils lying on the surface of the earth. Most people wouldn’t know what it was. It wasn’t a skull, a leg bone, or part of a jaw. It was just a chunk of bone.
Shepard immediately alerted park rangers. The ranger then notified the North Dakota Department of Mineral Resources. Her actions ultimately led scientists to discover not only a new species, but an entirely new genus of mosasaurs, giant marine predators that lived in the late Cretaceous oceans. Bite marks preserved in the fossil suggest that it met its end in the hands, or perhaps teeth, of another mosasaur.
Meet Jorgy the Mosasaurus
The new mosasaurid was described Monday in the American Museum of Natural History’s newsletter. Yarmungander valhallaensis, or “Jorgie” for short, is a name suggested by co-author Clint Boyd and is steeped in Norse mythology. Yarmungandr is the name of a sea serpent that orbits the world with its tail in its jaws.
valhallaensis A reference to Walhalla, North Dakota, a town near the fossil site where this mosasaurus was excavated. Walhalla refers to Valhāll, the great hall where the Norse god Odin resurrects his dead soldiers and rises in preparation for the battle (an event known as Ragnarik) caused by Jarmungandr releasing his tail.
But mosasaurs were clearly not mythical beings. They were large, toothed carnivores, some reaching lengths of about 15 meters (about 50 feet). Although they were fully aquatic, they needed to surface to breathe air, like whales today. Early forms had legs, indicating an ancient migration from land to sea. Although a significant number of mosasaurs have been unearthed around the world, there is still much to learn about these animals and their evolution.
What remains of Jogi is a nearly complete skull, some ribs, and numerous vertebrae. Unlike most other mosasaurs, this mosasaur has bone preserved inside its mouth-shaped skull, which is rare and rarely found in other mosasaurid specimens.
Bite marks on the bones indicate a violent struggle just before death, which can lead to a gruesome death. Some of the bite marks on his spine show no signs of healing, indicating that they occurred at a time close to, if not exact, around the time of Jorgy’s death, about 80 million years ago.
Their marks are well defined to identify potential bite victims. What are the possible culprits? Another mosasaurus. To make matters worse, that particular bite may have led to an amputation that separated one part of Jorgie’s body from another. There were no bite marks on Jogi’s skull, leading the team to speculate that the attacker may have eaten the lower half of the body, which could be why so few remains have been recovered.
Found on the roadside
What may have been a very dramatic scene millions of years ago stands in stark contrast to the relatively mundane environment in which the bones were found. The public fossil dig site is located adjacent to a gravel road in North Dakota State Park. Boyd is a senior paleontologist with the North Dakota Geological Survey and curator of the North Dakota Fossil Collection. He is also part of the team that organizes and directs public excavations.
“The rock there is really soft,” Boyd explained in a video interview. “The weather is really fast. It’s right next to the road, so the cut is steep and unstable.” As the rock crumbles, new fossils are exposed. “This is why public fossil excavations are done in the first place: to save fossils that would otherwise collapse and be lost.” [rocks]”
But once you discover a fossil, how do you determine whether it belongs to a new species and genus?
Lead author Amelia Zietlow, whose paper focuses on mosasaurs, is a doctoral candidate at the Richard Gilder Graduate School at the American Museum of Natural History in New York. In her video interview, she said she was asked which was most important when deciding to name a new species. The animal’s anatomy and the location of the fossil in the sediment (stratigraphy), which indicates when the animal existed.
“It has to be anatomy,” Zietlow said. “That’s taxonomy. You’re describing an animal, and that animal is based on its anatomy. When you determine what species something is, you need to know when it lived, its environment, It doesn’t really matter what that looks like, but it’s certainly an important factor for other biological problems.”
