The premaxilla of "Paranthodon" is incomplete, but the anterior process is sinuous and curves ventrally. This is similar to in "Miragaia", "Huayangosaurus", the ankylosaur "Silvisaurus", and "Heterodontosaurus", but unlike in "Chungkingosaurus", "Stegosaurus", "Edmontonia" and "Lesothosaurus". The premaxilla also lacks any teeth, like in every stegosaur except "Huayangosaurus" where the premaxilla is preserved. Like in "Huayangosaurus" but not "Stegosaurus" or "Hesperosaurus", the nasal fenestra faces anterolaterally, being visible from the front and sides. The naris is longer than wide like in other stegosaurs, and also has a smooth internal surface, so it was most likely a simple passage. The maxilla is roughly triangular, as in most other thyreophorans. The tooth row is horizontal in lateral view, and in ventral view it is sinuous. "Stegosaurus" and "Huayangosaurus" possess a straight tooth row in ventral view, although "Scelidosaurus" and "Jiangjunosaurus" do not. The maxilla of "Paranthodon" preserves the tooth row, and shows that there is little to no overhang. This differs from ankylosaurians, where there is a large overhang of the maxilla. As with "Stegosaurus" and "Silvisaurus", there is a diastema (gap in the tooth row) on the maxilla in front of the tooth row. The posterior maxilla is incomplete so no information is known about the jugal or lacrimal contact. "Paranthodon" has an elongate, dorsally convex nasal, like in most other stegosaurs. There are thickened ridges along the sides of the nasals. The preserved portion of the nasal does not contact the premaxilla or maxilla.