Pachyrhinosaurus was a large, plant-eating dinosaur characterized by a distinctive bony boss over its nose instead of a prominent horn, along with a frill extending from the back of its skull. This quadrupedal ceratopsian roamed North America during the Late Cretaceous Period, between approximately 74 and 68 million years ago. Its name, meaning “thick-nosed lizard,” directly references this unique facial feature.
North American Homelands
Fossil evidence indicates Pachyrhinosaurus was primarily present in the western parts of North America. Its remains have been predominantly discovered in present-day Canada and the United States.
In Canada, a significant number of Pachyrhinosaurus fossils have been unearthed in Alberta. In the United States, its presence is notable in Alaska. This wide latitudinal distribution across western North America suggests the dinosaur adapted to different regional conditions during the Late Cretaceous.
Reconstructing its Ancient Environment
During the Late Cretaceous Period, the North American landscapes inhabited by Pachyrhinosaurus differed considerably from today. The climate was warmer and more humid, with subtropical conditions prevailing in many areas. This environment featured vast coastal plains, extensive river deltas, and swampy regions.
Paleontologists infer these ancient environments through geological evidence, such as rock formations indicating past water bodies or terrestrial deposits. Plant fossils found alongside Pachyrhinosaurus remains, including ferns and cycads, provide clues about the lush vegetation that formed its diet and habitat. Associated animal fossils, like those of fish, amphibians, and other reptiles, help paint a picture of the complete ecosystem.
Landmarks of Discovery
In Alberta, Canada, the Horseshoe Canyon Formation is an important site where Pachyrhinosaurus canadensis remains have been found. This formation, dating back approximately 73.1 to 68.0 million years ago, provides evidence of a warm, wet deltaic setting transitioning to a seasonally wet-dry coastal plain. The Pipestone Creek Bonebed in Alberta, sometimes called the “River of Death,” is another important Canadian locality, yielding thousands of bones, primarily from Pachyrhinosaurus lakustai.
In Alaska, United States, the Prince Creek Formation on the North Slope has been important for understanding Pachyrhinosaurus perotorum. This formation, dating to about 70-69 million years ago, represents a high-latitude environment that, while warmer than today, experienced periods of cold and darkness. The discovery of juvenile P. perotorum remains in the Kikak-Tegoseak Quarry within the Prince Creek Formation suggests these dinosaurs lived year-round in the Arctic.