A new discovery has revealed a previously unknown species of mosasaur, Jormungander walhallaensi, shedding new light on the oceans of the Late Cretaceous period. Named after the legendary Norse sea serpent, this ancient “sea dragon” provides a rare glimpse into the evolution of marine reptiles and the apex predators that dominated prehistoric seas. Unearthed in 2015 in Walhalla, North Dakota, the nearly complete fossil preserved the skull, jaws, and spine, allowing scientists to study its anatomy in remarkable detail. With its unique features bridging smaller mosasaurs like Clidastes and giants like Mosasaurus, Jormungander offers crucial insights into how these reptiles adapted, evolved, and ruled the oceans nearly 80 million years ago.
Fossil discovery in North Dakota reveals a mosasaur frozen in time
According to Mirror, the story of Jormungander walhallaensi begins in 2015 in Walhalla, North Dakota. Paleontologists unearthed a nearly complete fossilised skeleton that stunned the scientific community with its exceptional preservation. The discovery included almost the entire skull, jaws, and spine, along with a significant portion of the vertebrae, allowing for detailed study of its anatomy.After more than eight years of analysis, researchers confirmed that this specimen did not match any known mosasaur species. As the study notes, this fossil comes from a geologic time in North America that has been poorly understood, making it a crucial find for understanding the evolution of marine reptiles.
Transitional mosasaur bridges the gap between small and giant predators
Estimated to have measured around 24 feet in length, Jormungander walhallaensi was a formidable predator. It possessed powerful flippers, a shark-like tail, and distinctive ridges above its eyes that researchers described as “angry eyebrows.” These features highlight its unique place in the mosasaur family tree.The species also exhibits transitional traits connecting two well-known mosasaur groups: the smaller Clidastes and the massive Mosasaurus, which could reach nearly 50 feet in length. This blend of features helps scientists understand how mosasaurs evolved from smaller, agile hunters into the oceanic giants that dominated the seas.
What Jormungander tells us about late cretaceous oceans
Jormungander walhallaensi lived around 80 million years ago, before the rise of its larger relatives. Mosasaurs were among the most dominant marine predators of their era. Despite popular association with dinosaurs, these creatures were more closely related to modern lizards and snakes. They evolved from land-dwelling reptiles into fully aquatic hunters, adapting to life in the prehistoric seas.The discovery helps fill a key gap in the mosasaur timeline, offering a clearer picture of how these apex predators adapted over millions of years. By studying transitional species like Jormungander, scientists can better understand marine evolution and predator-prey dynamics of the Late Cretaceous oceans.
Expanding scientific knowledge of prehistoric marine life
Beyond its evolutionary significance, Jormungander walhallaensi provides insight into the northern regions of the Western Interior Seaway, an ancient inland sea that split North America during the Late Cretaceous. The study published in American Museum of Natural History highlights how such discoveries enrich understanding of marine ecosystems and spark further scientific inquiry.The fossil’s exceptional preservation and unique anatomy make it a critical piece in reconstructing the diversity and adaptations of mosasaurs before the asteroid impact that ended the Cretaceous period.Jormungander walhallaensi is more than just a new species; it is a bridge connecting ancient mosasaurs and a source of insight into the evolutionary history of marine reptiles. With its powerful build, distinctive facial ridges, and transitional traits, this “sea dragon” offers scientists a rare opportunity to explore how marine predators evolved, adapted, and ruled prehistoric oceans.By filling gaps in the fossil record, Jormungander highlights the remarkable diversity of life in the Late Cretaceous and enhances understanding of the evolutionary pathways that shaped modern marine ecosystems.Also Read: ‘It is the largest river delta on Earth’: NASA astronaut captures the stunning view of the Ganga river delta from space
