A rare, recently-discovered jawbone fragment belonging to a dog-sized horned dinosaur is the first fossil of its kind from the Late Cretaceous period in eastern North America, claims research published in the January edition of the journal Cretaceous Research.

The jawbone, which was identified by Dr. Nick Longrich from the Milner Centre for Evolution at the University of Bath, belonged to a kind of plant-eating horned dinosaur called ceratopsians. This specific fossil belonged to a smaller cousin of the Triceratops known as the leptoceratopsids, but was too incomplete to determine the exact species, the university said in a statement.

The fossil analyzed by Dr. Longrich was kept at the Peabody Museum at Yale University, and it showed that the creature’s jaw had an unusual shape that caused its teeth to curve downward and outwards like a beak. It was also more slender than the jaws of ceratopsians found in the western part of North America, highlighting a fossil divide on the continent.

During the Late Cretaceous, the researcher explained, the land mass that represents modern-day North America was split in half by the Western Interior Seaway. Dinosaurs living in the western continent of Laramidia were similar to those from Asia. On the other hand, dense vegetation has made it difficult to find many specimens from the eastern continent of Appalachia.

Eastern, western North American dinosaurs had distinct evolutions

The jaw fragment, which originally came from the Campanian Tar Heel Formation (Black Creek Group) of North Carolina, represents the first ceratopsian from the Late Cretaceous period found in what was once Appalachia, and the creature evolved along a distinct evolutionary path.

“Just as many animals and plants found in Australia today are quite different to those found in other parts of the world,” Dr. Longrich said, “it seems that animals in the eastern part of North America in the Late Cretaceous period evolved in a completely different way to those found in the western part of what is now North America due to a long period of isolation.”

This discovery “adds to the theory that these two land masses were separated by a stretch of water, stopping animals from moving between them, causing the animals in Appalachia to evolve in a completely different direction, resulting in some pretty weird looking dinosaurs,” he continued.

In fact, many land masses, including Europe, Africa, South America, India, and Australia, were isolated due to water, Dr. Longrich added. “Each of these island continents would have evolved its own unique dinosaurs,” he said, “so there are probably many more species out there to find.”

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Feature Image: University of Bath

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