Your Friendly Neighborhood Dinosaurs: Pachyrhinosaurus

 Photo by Kate Dzikiewicz

Photo by Kate Dzikiewicz

It’d be hard to miss the Bruce Museum’s resident dinosaurs. They stand overlooking our main entrance and have welcomed visitors for the last fifteen years. Today, I’m going to tell you a little about the history of these majestic beasts, both at the museum and 70 million years ago when they still roamed the floodplains of North America.

The Bruce Museum’s dinosaurs are the work of Canadian sculptor Brian Cooley. Brian Cooley is most famous for his life-sized reconstructions of dinosaurs, found at museums across the country. Our Brian Cooley dinosaur family, Pachyrhinosaurus, arrived at the Bruce Museum in 2001. Though they haven’t changed much since their original installation, they were given a fresh coat of paint in 2015.

The first Pachyrhinosaurus bones were collected in the 1940s, unearthed from the clay of the Horseshoe Canyon Formation in Alberta, Canada. The species was officially recognized in 1950, and since then, numerous other Pachyrhinosaurus bones have been collected. Paleontologists even found a mass death site, probably where a small herd of Pachyrhinosaurus perished in an unsuccessful river crossing.

Like all other horned and frilled ceratopsians, Pachyrhinosaurus was an herbivore. It was a good time to be an herbivore, too! Though it lived in the Northern part of the United States, it was a lot warmer in the late Cretaceous than it is now. The climate ranged somewhere between temperate and subtropical with warm and wet weather. Pachyrhinosaurus shared its environment with various other horned ceratopsian relatives, duck-billed hadrosaurs, armored ankylosaurs, and a number of carnivorous theropods. Of those theropods, the tyrannosaur Albertosaurus was probably the biggest threat to Pachyrhinosaurus.


One of the most prominent features of our Pachyrhinosaurus group is the array of horns along the front of their faces. These horns were never found fossilized, but paleontologists thought that the thickened bony snout of Pachyrhinosaurus may have supported rhinoceros-like keratinous horns. Unfortunately, our Pachyrhinosaurus may be in need of a nose job. In 2009, a scientific study uncovered information that points to a different facial structure for the ancient dinosaur.

To find out what sort of facial ornamentation Pachyrhinosaurus may have sported, scientists compared its bone structure with that of other horn-bearing animals. What they found was that the skull of Pachyrhinosaurus  wasn't actually very similar to that of a rhinoceros. Instead, it looked more like a muskoxen skull. Muskoxen have a thickened pad of tissue over their snouts which protects them in their yearly head-butting contests. So rather than having spectacular horns, Pachyrhinosaurus probably had a raised boss more like a muskox. They quite likely butted heads like a muskox too!


 Photo by Kate Dzikiewicz

Photo by Kate Dzikiewicz

Something else you might notice about Pachyrhinosaurus is that its eyes are positioned on the side of its head. Herbivores from all across the tree of life often evolve with this feature. Animals with eyes on the sides of their head have a very wide range of vision. They lose most depth perception, but gain the ability to detect danger across a bigger area. Horses, rabbits, deer, and many other prey species have their eyes positioned this way. Predators are the opposite, tending to have their eyes facing forward, so they can accurately judge distance to their prey.

 


Next time you drop by, feel free to give Pachyrhinosaurus a pet before you leave. When you do, take notice of the pebbled texture of their skin. Brian Cooley didn't just pull this texture out of nowhere. Paleontologists have discovered fossilized skin imprints from dinosaurs related to Pachyrhinosaurus, showing this pebbled texture. Currently, there's not much evidence to suggest feathering for the more advanced ceratopsians, like Pachyrhinosaurus. However, an earlier relative had quill-like protofeathers, so it's not entirely out of the question!

- Kate Dzikiewicz, Paul Griswold Howes Fellow