**Title: Jormungandr: Newly Discovered Mosasaur Species Sheds Light on Evolution and Geologic History**
**Subtitle: Fossil findings in North Dakota reveal a transitional species between two well-known marine lizards**
*Date: October 31, 2023*
In a groundbreaking discovery, scientists have identified a new species of mosasaur that provides vital insights into the evolution and geologic history of these ancient marine lizards. Named *Jörmungandr walhallaensis*, this colossal 24-foot-long creature lived approximately 80 million years ago and represents a transitional species between two prominent mosasaur species. The finding, made near Walhalla, North Dakota, offers new details about aquatic adaptations and the lineage of these fascinating reptiles.
Mosasaurs were large, carnivorous aquatic lizards that thrived during the late Cretaceous period. This recent discovery unveils a mosasaur species with distinctive “transitional” traits, placing it between two well-known mosasaurs. Researchers named the new species after Jormungandr, a sea serpent in Norse mythology, and Walhalla, the small city close to where the fossil was unearthed. The findings have been published in the *Bulletin of the American Museum of Natural History*.
Lead author of the study, Amelia Zietlow, a Ph.D. student in comparative biology at the American Museum of Natural History’s Richard Gilder Graduate School, describes *Jǫrmungandr walhallaensis* as a creature that closely resembles a “Komodo dragon with flippers, but significantly larger.” This characterization helps visualize the appearance of this ancient marine lizard.
The mosasaur lineage has fascinated scientists for centuries, but many questions about these creatures remain unanswered. One of the ongoing debates in mosasaur research revolves around the number of times these reptiles evolved flippers and became fully aquatic. Researchers believe this transition occurred at least three times, and possibly more. Moreover, the relationship between mosasaurs and other reptiles, such as monitor lizards or snakes, has yet to be definitively determined.
The recent discovery of *Jǫrmungandr walhallaensis* contributes a significant piece to the puzzle of mosasaur evolution. The fossil, discovered in 2015 during excavations in northeastern North Dakota, contains a nearly complete skull, jaws, cervical spine, and several vertebrae. Through extensive analysis and surface scanning, Zietlow and her collaborators established that this specimen exhibits features indicative of two well-known mosasaurs: *Clidastes*, a smaller and more primitive form, and *Mosasaurus*, a larger species that grew up to 50 feet long and coexisted with the mighty *Tyrannosaurus rex*. This newly discovered mosasaur species measures approximately 24 feet long, featuring flippers, a shark-like tail, a bony ridge on its skull creating “angry eyebrows,” and a slightly stumpy tail shorter than its body.
The findings shed light on the evolutionary process of mosasaurs as they transformed into enormous marine predators. The study suggests that *Jormungandr* served as a precursor to *Mosasaurus*, existing around 80 million years ago. By highlighting this transitional species, researchers gain a better understanding of the relationships between different groups of mosasaurs.
Co-author Clint Boyd from the North Dakota Geological Survey emphasizes the geological significance of the discovery, stating, “This fossil is coming from a geologic time in the United States that we don’t really understand. The more we can fill in the geographic and temporal timeline, the better we can understand these creatures.” Co-author Nathan Van Vranken from Eastern West Virginia Community and Technical College adds that the findings contribute to our understanding of the northernmost regions of the interior seaway and ignite scientific curiosity.
The discovery of *Jörmungandr walhallaensis* showcases the ongoing advancements in paleontological research and our evolving knowledge of prehistoric creatures. As scientists uncover more details about these ancient marine lizards, the puzzle of mosasaur evolution becomes clearer, ultimately deepening our understanding of the Earth’s past.
*Reference:*
“Jormungandr walhallaensis: a new mosasaurine (Squamata: Mosasauroidea) from the Pierre Shale Formation (Pembina Member: Middle Campanian) of North Dakota” by Amelia R. Zietlow, Clint A. Boyd, and Nathan E. Van Vranken, *Bulletin of the American Museum of Natural History*, DOI: 10.5531/sd.sp.60