STL Science Center

STL Science Center

21 September 2012

A Little Naming Deception

A dinosaur known only from its skull, Arrhinoceratops brachyops is a Chasmosaurine dinosaur that is closely related to Torosaurus. It has only been found in Canada and the initial find, a distorted, due to crushing pressure, skull, lacks its lower jaw and has absolutely no postcranial skeleton attached to it. The lack of skeleton is disturbing because its close relation to Torosaurus could lead some to believe that Arrhinoceratops is another form of Torosaurus and not its own genus. Thankfully, however, it possesses enough differences to be considered both an adult and distinctly different from Torosaurus, and Triceratops, and so will not be mashed into the other genus as has happened in the recent past (the mass opinion is still far from consensus last I heard a debate about those findings). Regardless, one of the things that sets Arrhinoceratops so far out on its own is the nasal horn that it possesses which is little more than a forward facing nub of bone sheathed in keratin. The name Arrhinoceratops means "No nose-horn face" and the name was coined because the initial description mistook the small nub of bone as a part of the distortion caused by the skull's crushing during fossilization. The brow horns are very ceratopsian in nature, curving first up then forward and outward. The frill is typical also; sweeping backward and up to cover the neck with multiple fenestrations to lighten the weight of the parietal and squamosal bones. Any anatomy aft of the neck frill is a guess based on the anatomy of other ceratopsians, as is the lower jaw, which was not found with the original skull either. The general Chasmosaurine structure of the tail, which was rather short compared to other ceratopsians, would have made Arrhinoceratops appear like a giant pig with an unwieldy head; a dangerous unwieldy head. The legs would have been of a moderate size, lifting Arrhinoceratops well clear of the ground, and would have been thick with muscle, allowing bursts of speed in defensive or rival-bashing behaviors. It would have been a heavyweight wrestler in its day, basically.

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