The most distinctive feature was a prominent horn situated on the skull midline behind the bony nostrils, which was formed from fused protuberances of the left and right nasal bones. Only the bony horn core is known from fossils—in the living animal, this core would have supported a keratinous sheath. While the base of the horn core was smooth, its upper two-thirds were wrinkled and lined with groves that would have contained blood vessels when alive. In the holotype, the horn core is long and wide at its base, but quickly narrows to only further up; it is in height. It is longer and lower in the skull of MWC 1. In the living animal, the horn would likely have been more elongated due to its keratinous sheath. Behind the nasal horn, the nasal bones formed an oval groove; both this groove and the nasal horn serve as features to distinguish "Ceratosaurus" from related genera. In addition to the large nasal horn, "Ceratosaurus" possessed smaller, semicircular, bony ridges in front of each eye, similar to those of "Allosaurus". These ridges were formed by the lacrimal bones. In juveniles, all three horns were smaller than in adults, and the two halves of the nasal horn core were not yet fused.