Stygimoloch (name meaing "River Styx") is a genus of pachycephalosaurid dinosaur that originated from Late Cretaceous North America.
In the Series 2 finale "Death of a Dynasty II: The Return of the King", a herd of Stygimoloch (consisting seven adults and five juveniles) were brought to Prehistoric Arena in the park from Late Cretaceous Montana, 65 million years ago.