Wikipedia
Stygimoloch is a controversial genus of pachycephalosaurid dinosaur from the end of the Cretaceous period, roughly 66 million years ago. It is currently known from the Hell Creek Formation, Ferris Formation, and Lance Formation of the Western Interior ( United States), where it lived alongside Tyrannosaurus and Triceratops. The type species, S. spinifer, was described by British vertebrate paleontologist Peter Galton and German paleontologist Hans-Dieter Sues of the National Museum of Natural History in 1983. Stygimoloch is characterized by clusters of spikes on the back of the skull, in which a long central horn is surrounded by 2-3 smaller hornlets, and a tall, narrow dome. Dracorex has similar but shorter hornlets and lacks a dome, and has been interpreted as either a distinct species, or a juvenile or female of Pachycephalosaurus or Stygimoloch. It has also been proposed that Stygimoloch represents partially grown individuals of Pachycephalosaurus.
The name Stygimoloch comes from the river Styx, which is said to run through the underworld in Greek Mythology, in reference to the Hell Creek Formation, and from Moloch, the name of a Canaanite god, chosen in reference to the bizarre appearance of the animal.