Stygimoloch

Stygimoloch ("devil from hell," from Styx, Greek mythological underworld river, and moloch, Hebrew for an evil-connoted angel, such as the Angel of Death) is a genus of pachycephalosaurid dinosaur from the end of the Cretaceous period, roughly 66 million years ago. Its taxonomical status is in dispute, as the failure to discover adult specimens strongly implies that collected holotypes merely represent juvenile pachycephalosaurs. This hypothesis has been supported by numerous modern studies, the most recent of which agrees that Stygimoloch is synonymous with Pachycephalosaurus. The genus was discovered in the Hell Creek Formation, Ferris Formation, and Lance Formation of the Western Interior (United States), where it lived alongside such genera as Tyrannosaurus, Triceratops, and Edmontosaurus.