While examining previously-misidentified fossils that had been at the Canadian Museum of Nature for 75 years, British paleontologist Dr. Nick Longrich discovered two new species of dinosaurs that roamed western North America 75 million years ago.

The fossils had previously been classified as Anchiceratops and Chasmosaurus (top), which both lived in what is now Canada. But Longrich's research revealed that they more closely resemble known dinosaurs from the area that is now the American Southwest, indicating that they are likely subspecies of those dinosaurs. One is a new species of Pentaceratops, a buffalo-sized vegetarian, now known as Pentaceratops aquilonius. A more complete skeleton is needed to better identify the other species, but it is believed to be a subspecies of Kosmoceratops, a dinosaur with an ornate skull from Utah.

Discovering more dinosaurs is always exciting news, and according to Longrich, this could pave the way for further revelations. "We thought we had discovered most of the species, but it seems there are many undiscovered dinosaurs left," he told the Daily Mail. "We've really only just scratched the surface."

These new species fit into a larger picture of dinosaur biodiversity that is unmatched by animals today.

"The distribution of dinosaur species was very different from the patterns seen in living mammals," Longrich said. "In living mammals, there tend to be relatively few large species, and they have large ranges. With Cretaceous dinosaurs, we see a lot of large species in a single habitat. They also tend to be very regional—as you move from one habitat to another you get a completely different set of species."