Unveiling a Gargantuan Marine Lizard – New Mosasaur Species Sheds Light on Evolutionary and Geological Contexts

by Manuel Costa
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New Mosasaur Discovery

The recent identification of a new species of mosasaur, Jörmungandr walhallaensis, provides pivotal perspectives into the evolutionary development of these prehistoric sea lizards as well as the geological narrative of late Cretaceous North America. Located near Walhalla, North Dakota, this intermediate species bridges the evolutionary space between rudimentary and more sophisticated mosasaurs, providing fresh insights into their marine adaptability and genealogy. Illustrations of two Jormungandr walhallaensis mosasaurs in combat have been credited to Henry Sharpe.

At an astonishing length of 24 feet, Jormungandr existed approximately 80 million years ago and serves as a linking species between two well-established mosasaurs.

The species has recently been documented in a scholarly article in the Bulletin of the American Museum of Natural History. The creature’s name draws inspiration from a sea serpent in Norse folklore, Jormungandr, and also pays homage to the small North Dakota city, Walhalla, where the fossil evidence was unearthed.

Comparative Characteristics and Historical Framework

Amelia Zietlow, the principal author of the study and a doctoral student in comparative biology at the American Museum of Natural History’s Richard Gilder Graduate School, likened the creature to a gigantic Komodo dragon with flippers. Mosasaurs were first discovered over two centuries ago, predating even the term “dinosaur.” However, numerous queries concerning these creatures persist. Among the unanswered questions are the number of instances these lizards evolved flippers to become fully aquatic—estimated to be at least three to potentially four or more—and their closest relatives, whether monitor lizards or snakes. This new research contributes an additional layer to the existing body of knowledge regarding mosasaur relationships.

Details of the Fossil Discovery

The fossil that serves as the basis for this study was excavated in 2015 in northeastern North Dakota. The find was remarkable, comprising a nearly intact skull, jaw, cervical spine, and multiple vertebrae.

Upon thorough examination and surface scanning of the fossil, Zietlow and her research team discerned that this creature represents a new species exhibiting a combination of traits seen in two iconic mosasaurs: Clidastes, a less evolved, smaller species, and Mosasaurus, a significantly larger species that existed contemporaneously with Tyrannosaurus rex. The animal is estimated to be around 24 feet in length and would have possessed flippers, a shark-like tail, a bony ridge on its skull that would create the appearance of “angry eyebrows,” and a tail somewhat shorter than its body.

Evolutionary Implications and Geological Importance

Zietlow noted that these sea-dwelling lizards continually evolved into increasingly larger forms. The findings hint that Jormungandr could be a predecessor to Mosasaurus and likely existed around 80 million years ago.

Clint Boyd, a co-author from the North Dakota Geological Survey, stated that the fossil comes from a geological era in the United States that is not yet fully understood. Filling gaps in both the geographical and chronological contexts enables a more comprehensive understanding of these ancient creatures.

Nathan Van Vranken, another co-author from Eastern West Virginia Community and Technical College, remarked that the story of Jormungandr contributes significantly to our comprehension of the most northern expanses of the ancient seaway, particularly concerning mosasaurs. Discoveries of this nature serve to stimulate scientific inquiry.

Reference

The study “Jormungandr walhallaensis: A New Mosasaurine (Squamata: Mosasauroidea) from the Pierre Shale Formation (Pembina Member: Middle Campanian) of North Dakota” was authored by Amelia R. Zietlow, Clint A. Boyd, and Nathan E. Van Vranken, and was published on October 30, 2023, in the Bulletin of the American Museum of Natural History.
DOI: 10.5531/sd.sp.60

Frequently Asked Questions (FAQs) about New Mosasaur Discovery

What is the significance of the new mosasaur species, Jörmungandr walhallaensis?

The identification of Jörmungandr walhallaensis provides crucial insights into the evolutionary development of mosasaurs, ancient marine lizards. Additionally, it adds to our understanding of the geological landscape of late Cretaceous North America.

Where was the fossil of this new mosasaur species found?

The fossil was discovered near Walhalla, North Dakota, in the northeastern part of the state.

How does this new species contribute to our understanding of mosasaur evolution?

Jörmungandr walhallaensis serves as a transitional species, bridging the gap between more primitive and advanced mosasaurs. It offers new details about their aquatic adaptations and lineage, contributing to ongoing research on their evolutionary history.

What are some key physical features of Jörmungandr walhallaensis?

The specimen is estimated to be around 24 feet long. It likely had flippers, a shark-like tail, a bony ridge on its skull creating “angry eyebrows,” and a somewhat stumpy tail that was shorter than its body.

How does the discovery contribute to geological understanding?

The fossil evidence hails from a geological period in the United States that is not yet fully understood. Therefore, the discovery helps to fill in gaps in both geographical and chronological contexts, aiding in a more complete understanding of late Cretaceous geology.

What were the collaborative institutions or individuals involved in this study?

The study was authored by Amelia R. Zietlow from the American Museum of Natural History’s Richard Gilder Graduate School, Clint A. Boyd from the North Dakota Geological Survey, and Nathan E. Van Vranken from Eastern West Virginia Community and Technical College.

When was the fossil discovered?

The fossil that serves as the basis for this study was excavated in the year 2015.

Where was the study published?

The study was published in the Bulletin of the American Museum of Natural History on October 30, 2023.

How do mosasaurs relate to present-day animals?

While the exact lineage is still under study, researchers are investigating whether mosasaurs are more closely related to monitor lizards or to snakes.

What is the source of the species’ name, Jörmungandr walhallaensis?

The name draws inspiration from Jormungandr, a sea serpent in Norse mythology, and Walhalla, the small North Dakota city near where the fossil was discovered.

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