Regaliceratops (meaning "Royal horned face") is a monospecific genus of chasmosaurine ceratopsid dinosaur from Alberta, Canada that lived during the Late Cretaceous (middle Maastrichtian stage, 68.5 to 67.5 Ma) in what is now the St. Mary River Formation. The type and only species, Regaliceratops peterhewsi, is known only from an adult individual with a nearly complete skull lacking the lower jaw, which was nicknamed "Hellboy". Regaliceratops was named in 2015 by Caleb M. Brown and Donald M. Henderson. Regaliceratops has an estimated length of 5 metres (16 feet) and weight of 1.5 tonnes (3,306 lbs). The skull of Regaliceratops displays features more similar to centrosaurines, which suggests convergent evolution in display morphology in ceratopsids.[1]
In 2005, a skull of a ceratopsid was discovered by geologist Peter Hews from the St. Mary River Formation, along the Oldman River in southwestern Alberta. The skull was located in well cemented siltstone and with the tip of the snout sticking out of a cliff. The skull was excavated in 2006 and 2008 by a team of the Royal Tyrrell Museum and was removed in blocks. The excavation was described as being complicated as the specimen was in close proximity to protected spawning habitat of bull trout in the river. The specimen was nicknamed "Hellboy" due to difficultly and time consuming excavation, in addition to the hard matrix, and the presence of small postorbital horncores with resorption pits. The specimen was subsequently named and described in 2015 by Caleb M. Brown and Donald M. Henderson.[1]
The holotype specimen, TMP 2005.055.0001, consists of a nearly complete skull that is missing only the rostrum. The skull was deformed by compression and its rear and underside are obscured by the matrix. The specimen represents an adult individual as the cranial elements are fused together and the bone surface texture is rugose, unlike that of juvenile and subadult ceratopsids.[1]
The generic name, Regaliceratops, is derived from the Latin word "regalis" (royal) and the Greek words "keras", (horn), and "ops", (face). The generic name is in reference to the crown-shaped parietosquamosal frill and the Royal Tyrrell Museum. The specific name, peterhewsi, honours the geologist Peter Hews, who discovered the type specimen.[1]
Regaliceratops has an estimated length of 5 metres (16 feet) and weight of 1.5 tonnes (3,306 lbs).[2]
Brown & Henderson (2015) diagnosed Regaliceratops based on the presence of a single, midline epiparietal ossification that is offset from the plane of the frill and other epiparietals towards the rostrum with parietals projecting towards the posterior end that have a roughly triangular transverse cross-section; a prominent midline ridge on that parietal that merges with the median epiparietal; paired epiparietal ossifications that are long, flat, and roughly pentagonal shaped; a prominent postorbital ridge that runs diagonally from the supraorbital horncore to the base of the squamosal; parietal fenestrae that are small in size to orbit as in Kosmoceratops; and nasal horncores that are larger than the postorbital horncores as in Chasmosaurus bellis and Vagaceratops.[1]