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Description
Marginocephalia is a clade of ornithischians including the horned, ceratopsians dinosaurs and the dome-headed, pachycephalosaurian dinosaurs. Skulls are limited to the preorbital region, and are aligned so that the maxilla is level; they are not to scale, and are shown with the illustrations at largely the same length.
A, Heterodontosaurus tucki, member of a group that may be part of Marginocephalia, or close to the morphology from which marginocephalians arose.
B, Goyocephale lattimorei, considered to be the most basal member of Pachycephalosauria, and significant in its retention of three large premaxillary teeth, including a large third fang-like tooth; not shown, but like Heterodontosaurus tucki the dentary also had a large fang.
C, Abrictosaurus consors, a heterodontosaurid without distinct fangs.
D, Tianyulong confuciusi, an ambiguous form, possessing a heterodontosaurid-like snout but very short forelimbs and a short, nearly-straight ischium much like Pachycephalosauria.
E, Chaoyangsaurus youngi, a basal ceratopsian with unusually large orbits, despite not seeming to be too young of an animal.
F, Liaoceratops yanzigouensis, a basal neoceratopsian.
G, Yinlong downsi, a basal ceratopsian with exceptionally large premaxillary teeth having large serrations; like pachycephalosaurians, the cheeks are covered in little ridges and tubercles.
H, Auroraceratops rugosus, a robustly-built ceratopsian reminiscent of some psittacosaurids but with small premaxillary dentition.
I, Archaeoceratops oshimai, a basal ceratopsian with tiny premaxillary dentition.

Description
Marginocephalia is a clade of ornithischians including the horned, ceratopsians dinosaurs and the dome-headed, pachycephalosaurian dinosaurs. Skulls are limited to the preorbital region, and are aligned so that the maxilla is level; they are not to scale, and are shown with the illustrations at largely the same length.
A, Heterodontosaurus tucki, member of a group that may be part of Marginocephalia, or close to the morphology from which marginocephalians arose.
B, Goyocephale lattimorei, considered to be the most basal member of Pachycephalosauria, and significant in its retention of three large premaxillary teeth, including a large third fang-like tooth; not shown, but like Heterodontosaurus tucki the dentary also had a large fang.
C, Abrictosaurus consors, a heterodontosaurid without distinct fangs.
D, Tianyulong confuciusi, an ambiguous form, possessing a heterodontosaurid-like snout but very short forelimbs and a short, nearly-straight ischium much like Pachycephalosauria.
E, Chaoyangsaurus youngi, a basal ceratopsian with unusually large orbits, despite not seeming to be too young of an animal.
F, Liaoceratops yanzigouensis, a basal neoceratopsian.
G, Yinlong downsi, a basal ceratopsian with exceptionally large premaxillary teeth having large serrations; like pachycephalosaurians, the cheeks are covered in little ridges and tubercles.
H, Auroraceratops rugosus, a robustly-built ceratopsian reminiscent of some psittacosaurids but with small premaxillary dentition.
I, Archaeoceratops oshimai, a basal ceratopsian with tiny premaxillary dentition.