At the end of the Cretaceous, between 100 and 66 million years ago, present-day North America was divided into two continents, separated by a shallow sea that ran between the Arctic Ocean and the Gulf of Mexico. In general, the dinosaurs that lived in the western land mass, a large island called Laramidia, had morphological characteristics similar to those that inhabited what is now Asia . However, hardly any remains of those who inhabited the eastern island, Appalachia, have been discovered.
The fauna that thrived in it remained isolated for a long time and developed differently from what could be found in the west. For example, while the Tyrannosaurus rex , 12 meters long and 7 tons in weight, hovered in Laramidia , its equivalent in Appalachia was the driptosaurus, another carnivorous theropod, but much smaller, of a ton and a half and barely 7 meters in height. long.
During the Pleistocene glaciations, which occurred between 2.59 million years ago and 10,000 years ago, much of the fossil deposits of what was once Appalachia were destroyed. In addition, the region is densely covered by vegetation , which makes it difficult to study those that have been found.
Now, the paleontologist Nick Longrich, from the Department of Biology and Biochemistry at the University of Bath, in the United Kingdom, has identified the remains of a small ceratopsid, a horned dinosaur the size of a dog, that lived precisely in that area.
The bone, a fragment of the jaw, was in the collection of the Peabody Museum of Natural History at Yale University, and, according to this expert in the journal Cretaceous Research , it is the first fossil of this type of dinosaur found in eastern North America. According to Longrich, the discovery will provide clues about the different evolutionary course that animals on both continents followed.
It must have been herbivorous, like its great Laramidia relative, the triceratops, which was 8 meters long, although it had a thinner jaw. From the few remains available – in fact, it is not even possible to attribute them to a specific species – it has been possible to know that it curved in such a way that it gave the nose the appearance of a large beak. Longrich suspects this is because he was on a different diet than other ceratopsids.
“In this case we find something similar to what happens in Australia. There you can find animals and plants very different from those found in other parts of the world. In the same way, it seems that at the end of the Cretaceous, the fauna of the Eastern North America, which remained disconnected from that of the West by the sea, followed a completely different evolutionary path. The same phenomenon took place in other areas of the world, in what is now Europe, India, Africa or South America “, indicates Longrich .
Image: Nick Longrich
