Monoclonius -described by Cope,1876 (Dodson, 1996). Monoclonius, literally meaning "single stem", referring to the single horn on its nose (Dodson, 1996). It has small postorbital horns and an enormously expanded parietal with huge fenestrae. The nasal horn is laterally compressed, divided into left and right halves, and recurved (Dodson, 1996). This is not a small animal, the length of its skull is about 1.65m (Dodson, 1996).