Description and Classification

Regaliceratops peterhewsi was a large, plant-eating dinosaur that walked on four legs. Scientists estimate it was about 5 meters (16 feet) long and weighed around 1.5 tonnes (1.7 short tons), similar in size to a modern white rhinoceros. Its most striking feature was its skull, which, like other ceratopsians, had horns and a large bony frill extending from the back.

The skull of Regaliceratops featured a tall horn on its nose and two relatively small horns above its eyes. The frill was distinctively short and wide for its group, adorned with a row of large, triangular, and shield-shaped bony plates called epiossifications around its upper edge, giving it a crown-like appearance. The frill itself had very small openings, or fenestrae, compared to its relatives.

Regaliceratops belongs to the Ceratopsidae family, specifically within the Chasmosaurinae subfamily. Chasmosaurines, such as the famous Triceratops and Chasmosaurus, are generally known for having long brow horns and long, broad frills. Interestingly, while Regaliceratops is classified as a chasmosaurine due to its underlying skull structure, its short frill and prominent nasal horn bear a striking resemblance to another group of horned dinosaurs called Centrosaurinae, like Centrosaurus. By the time Regaliceratops lived, most centrosaurines had already gone extinct.

Distinguishing Features

Regaliceratops had several unique characteristics that set it apart from other horned dinosaurs:

• A large, shield-like frill at the back of its skull that is wider and shorter than many of its relatives, decorated with seven large, triangular or spade-shaped bony growths (epiossifications) along its edge.
• A prominent, tall horn on its nose, situated above the nostrils.
• Two relatively small horns above its eyes, which is unusual for its specific group of horned dinosaurs (chasmosaurines) that typically had long brow horns.
• A unique mix of features: a body and snout similar to chasmosaurine dinosaurs, but a frill display more closely resembling centrosaurine dinosaurs.
• The central bone bar of the frill, separating the two small openings, is unusually wide.
• The openings (fenestrae) in its frill are much smaller than those seen in most of its close chasmosaurine relatives.

Paleoenvironment and Diet

Regaliceratops lived during the Maastrichtian age of the Late Cretaceous period. Its fossils were found in the St. Mary River Formation in southwestern Alberta, Canada. This region was part of the western landmass of North America called Laramidia. The environment was likely a mix of coastal plains, river valleys, and foothills, with a relatively cool and seasonal climate compared to other dinosaur habitats further south. It supported a variety of plant life, including ferns, conifers, and flowering plants.

As a herbivore, Regaliceratops would have used its powerful beak to snip off tough vegetation. It had rows of teeth arranged in dental batteries, which were constantly replaced, allowing it to efficiently grind up fibrous plant material. It probably fed on low-growing plants.

Regaliceratops shared its environment with other dinosaurs. These included hadrosaurs (duck-billed dinosaurs) like Edmontosaurus and Hypacrosaurus, armored ankylosaurs such as Anodontosaurus, and predatory theropods, likely including tyrannosaurids related to Albertosaurus or even early forms of Tyrannosaurus rex that were appearing around that time.

Significance and Ongoing Research

The discovery of Regaliceratops is significant because it shows an interesting case of convergent evolution. This means that Regaliceratops, a chasmosaurine, independently evolved frill features (like a shorter frill with large ornaments) that are very similar to those seen in the earlier, and mostly extinct, centrosaurine lineage. This suggests that similar environmental or social pressures might have led to similar physical traits developing in different groups.

The elaborate frill and horns of Regaliceratops were likely used for display, perhaps to attract mates, intimidate rivals, or help members of the same species recognize each other. While the horns could have offered some protection, their primary role was probably for visual signaling. The “Hellboy” nickname, referring to the comic book character with sawn-off horns, also brought public attention to this unique dinosaur, highlighting the difficulty scientists faced in excavating its incredibly hard rock matrix.

Ongoing research on Regaliceratops focuses on understanding its exact position within the chasmosaurine family tree and exploring the evolutionary pressures that led to its unique combination of features. As one of the last known horned dinosaurs before the mass extinction event that wiped out the non-avian dinosaurs, studying Regaliceratops helps paleontologists understand dinosaur diversity and evolution in the final stages of the Cretaceous period.