The pachycephalosaurids were close relatives of the ceratopsids and other ceratopsians within the Marginocephalia. They are famous for their thick, domed skulls, which may have been used for flank-pushing competitions (and not the popularly-portrayed head-smashing contests). Some scientists consider this group to include the same creatures as the larger Pachycephalosauria, claiming that the flat-headed members of this group (sometimes separated) represent juveniles of the pachycephalosaurids. The teeth of Stegoceras are almost identical to those of Troodon, suggesting it and the pachycephalosaurs had similar diets, though whether the pachycephalosaurs or Troodon was the omnivore isn't know with certainty (though the latter is a good possibility). The most complete fossil jaw shows that Pachycephalosaurus that it had serrated-blade-like front teeth, reminiscent to those of carnivorous theropods.
The only members of this group that appear in Dinosaur King are either Secret or Normal Move Card Dinosaurs, so they don't appear to have a "native" element; however, a defunct Dino Holder game website featured them as Lightning Dinosaurs, presumably because they are related to ceratopsians and, like Achelousaurus, can use Lightning Moves without horns.
A[]
C[]
- Colepiocephale lambei (formerly species of Stegoceras)
D[]
- Dracorex hogwartsia (possible juvenile Stygimoloch and/or Pachycephalosaurus)
G[]
- Goyocephale lattimorei
- Gravithulos albertae (may be same as Stegoceras)
H[]
- Hanssuesia sternbergi (formerly species of Stegoceras)
- Homocephale calathocercos
P[]
S[]
- Sinocephale bexelli
- Sphaerotholus/S. goodwini/S. buchholtzae
- Stegoceras/S. validum/S. novomexicanum
- Stygimoloch spinifer (possible juvenile Pachycephalosaurus)