PHOTO: NICK LONGRICH, UNIVERSITY OF BATHIn the late Cretaceous period, from about 100 million to 60 million years ago, North America was split down the middle by a shallow inland sea that stretched from the Gulf of Mexico to the Arctic. A newly described fossil specimen from the eastern half of the divided continent, called Appalachia, supports the idea that dinosaur evolution happened very differently there than among creatures that roamed the western half, called Laramidia.
The fossil dino, a Labrador-size member of the Leptoceratopsids, was a smaller cousin of Triceratops, and the shape of its jaw suggests a very specialized diet, distinct from that of its larger Laramidian relatives. The research will be published in the January 2016 issue of Cretaceous Research.
“Just as many animals and plants found in Australia today are quite different to those found in other parts of the world, 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,” study author Nicholas Longrich of the University of Bath in the U.K. told The Guardian. “This 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.”
Longrich studied a piece of upper jaw bone from a Leptoceratopsid that roamed eastern North America about 100 million years ago. The fossilized maxilla contained several odd characteristics, including teeth that curved downward and outward to form a beak shape unique to the group. “Studying fossils from this period, when the sea levels were very high and the land masses across the Earth were very fragmented, is like looking at several independent experiments in dinosaur evolution,” Longrich said.