It’s a well known fact that Tyrannosaurus rex dinosaurs inhabited the western part of North America millions of years ago, but a new study has revealed that it had a cousin that roamed around the eastern part of the continent.
Yale undergraduate Chase Doran Brownstein studied specimens that were unearthed back in the 1970s at the Merchantville Formation in what is now New Jersey and Delaware (the bones are currently being held at Yale’s Peabody Museum of Natural History) in order to find out more about dinosaurs during the Late Cretaceous Period – specifically, comparing those that lived in the eastern part of the continent to the ones in the west. In his new study, he found that two dinosaurs – an herbivorous duck-billed hadrosaur and a carnivorous tyrannosaur – lived in Appalachia (an area in eastern United States that consists of several states) approximately 85 million years ago.
To understand this better, millions of years ago, North America was divided into two different landmasses – Laramidia to the west and Appalachia to the east – with the Western Interior Seaway in between them. It is already known that Tyrannosaurus rex lived in Laramidia but very little was known about the dinosaurs that lived in Appalachia. But now, Brownstein has provided new information regarding that mystery.
He explained his research in further detail, “These specimens illuminate certain mysteries in the fossil record of eastern North America and help us better understand how geographic isolation— large water bodies separated Appalachia from other landmasses — affected the evolution of dinosaurs,” adding, “They’re also a good reminder that while the western United States has long been the source of exciting fossil discoveries, the eastern part of the country contains its share of treasures.”
Brownstein’s analysis of a partial therapod skull revealed that it was more than likely a tyrannosaur. While its hind legs were similar to a Dryptosaurus, its hands and feet (including the large forelimb claws) were different than those on a Tyrannosaurus rex. This indicates that it was part of a specific family of dinosaurs that evolved only in Appalachia. “Many people believe that all tyrannosaurs must have evolved a specific set of features to become apex predators,” Brownstein noted, “Our fossil suggests they evolved into giant predators in a variety of ways as it lacks key foot or hand features that one would associate with western North American or Asian tyrannosaurs.”
As for the duck-billed hadrosaur, it revealed valuable information regarding the shoulder girdle evolution in that species, as well as being one of the best specimens found east of the Mississippi and some of the very few young dinosaur fossils unearthed in the area. (A picture of two of the bones can be seen here.)
Brownstein’s study was published in the journal Royal Society Open Science where it can be read in full.