File:Pachycephalosauria jmallon.jpg

Summary
Sketch of a pachycephalosaur of uncertain systematical position and still (2003) not formally described. Its remains were found in the "Sandy Quarry" of the Hell Creek Formation, near Buffalo, South Dakota (USA). Initially reconstructed as Pachycephalosaurus wyomingensis by Michael Triebold later many attendees of an international symposium referred the remains to Stygimoloch spinifer because of the prominent spikes on the back of the skull.