Since this dinosaur is known only from its skull, scientists have few data about its overall anatomy.
The skull, as restored, features a broad, square, neck frill with two oval shaped openings.
The frill is deeply veined on both the top and the underside by arterial grooves.
The sides of the frill are adorned by about nine osteoderms.
The rear edge of the frill is lightly scalloped.
The left squamosal in the frill side of the holotype shows a pathological opening, perhaps the result of a wound.
Its brow horns were moderately long, but its nose horn was shorter and blunter than most ceratopids.
The snout is short and high.
Its body is assumed to be typical of the Ceratopsidae.
Based on the skull some popular-science books estimate the body length to be 6 m (20 ft) long when fully grown.
In 2010, Gregory S. Paul estimated its length at 4.5 metres (15 ft), its weight at 1.3 tonnes (2,900 lb).

Already Richard Swann Lull had in 1933 been politely critical of Parks' original description, and Tyson discovered that Parks, an entomologist, had made many mistakes.
The most notable of these was that the very trait the genus was named after, the lack of a separate ossification or os epinasale for the nose-horn, is in fact normal for the ceratopids, in which group this horn is an outgrowth of the nasal bone, not a distinct element.
Other incorrect observations by Parks included the conclusion that the os rostrale, the bone core of the upper beak, directly touched the nasals instead of being separated from them by the premaxillae; a presumed anterior process of the jugal touching the premaxilla; and thinking that the interparietal bar of the frill presented a separate skeletal element, an os interparietale.
Since this dinosaur is known only from its skull, scientists have few data about its overall anatomy. The skull, as restored, features a broad, square, neck frill with two oval shaped openings. The frill is deeply veined on both the top and the underside by arterial grooves. The sides of the frill are adorned by about nine osteoderms. The rear edge of the frill is lightly scalloped. The left squamosal in the frill side of the holotype shows a pathological opening, perhaps the result of a wound. Its brow horns were moderately long, but its nose horn was shorter and blunter than most ceratopids. The snout is short and high. Its body is assumed to be typical of the Ceratopsidae. Based on the skull some popular-science books estimate the body length to be 6 m (20 ft) long when fully grown. In 2010, Gregory S. Paul estimated its length at 4.5 metres (15 ft), its weight at 1.3 tonnes (2,900 lb).
Already Richard Swann Lull had in 1933 been politely critical of Parks' original description, and Tyson discovered that Parks, an entomologist, had made many mistakes. The most notable of these was that the very trait the genus was named after, the lack of a separate ossification or os epinasale for the nose-horn, is in fact normal for the ceratopids, in which group this horn is an outgrowth of the nasal bone, not a distinct element. Other incorrect observations by Parks included the conclusion that the os rostrale, the bone core of the upper beak, directly touched the nasals instead of being separated from them by the premaxillae; a presumed anterior process of the jugal touching the premaxilla; and thinking that the interparietal bar of the frill presented a separate skeletal element, an os interparietale.
Arrhinoceratops