A new genus and species of mosasaur being named Jormungandr walhallaensis has been discovered by American Museum of Natural History Ph.D. student Amelia Zietlow and colleagues.
Mosasaurs were a group of large, carnivorous aquatic reptiles that inhabited all of the world’s oceans during the Late Cretaceous epoch, between 90 and 66 million years ago.
These creatures went extinct during the end-Cretaceous extinction event which killed non-avian dinosaurs and 75% of life on the planet.
The first mosasaur was discovered more than 200 years ago, and the word ‘mosasaur’ predates the word ‘dinosaur.’
But many questions about these animals remain, including how many times they evolved flippers and became fully aquatic — paleontologists think it was at least three times, and maybe four or more — and whether they are more closely related to monitor lizards or snakes.
“After 200 years of scientific study, new mosasaur species are still being discovered as new localities are explored and specimens collected long ago are reevaluated using modern standards of species delimitation,” Zietlow and co-authors said.
“Even so, the phylogenetic positions of many key taxa are unresolved and therefore our understanding of mosasaur macroevolution is muddled.”
Jormungandr walhallaensis lived in the Cretaceous oceans approximately 80 million years ago.
Its fossilized skull and skeleton (cervical spine and a number of vertebrae) were discovered in 2015 in the Pierre Shale Formation in Cavalier County, North Dakota, the United States.
The species shows a mosaic of features seen in two iconic mosasaurs: Clidastes, a smaller and more primitive form of mosasaur; and Mosasaurus, a larger form that grew to be nearly 15 m (50 feet) long and lived alongside Tyrannosaurus rex.
Jormungandr walhallaensis is estimated to be about 7.3 m (24 feet long), and in addition to flippers and a shark-like tail, it would have had ‘angry eyebrows’ caused by a bony ridge on the skull,…
Read the full article here