This view was popularized in the 1956 science fiction story "A Gun for Dinosaur" by L. Sprague de Camp.
But paleontologists Richard Butler and Robert Sullivan nonetheless view the species as being Marginocephalia incertae sedis, rejecting the presumed synapomorphies with the Pachycephalosauria as incorrect identifications or lacking cogency because of a possible presence in ceratopsian groups.
Stygimoloch (meaning "demon from the Styx (greek river of death)") is a genus of pachycephalosaurid dinosaur from the end of the Cretaceous period, roughly 66 million years ago.
The inner artwork includes images of other dinosaur skulls steganographically overlapped in a similar manner to the front cover, including a pachycephalosaur and an ankylosaur.