Dinosaur Profile: Stygimoloch

Dinosaurs Fossils Placed On The Auction Block
Onlookers view a 68 million-year-old Stygimoloch skull outside the Fox studios which will be auctioned along with other dinosaurs fossils and pre-historic creatures by Guernsey's Auction House June 16, 2004 in New York City.

Mario Tama/Getty Images 


Stygimoloch (Greek for "horned demon from the river Styx"); pronounced STIH-jih-MOE-lock


Plains of North America

Historical Period:

Late Cretaceous (70-65 million years ago)

Size and Weight:

About 10 feet long and 200 pounds



Distinguishing Characteristics:

Moderate size; unusually large head with bony protuberances

About Stygimoloch

Stygimoloch (the genus and species name of which, S. spinifer, can be loosely translated as "horned demon from the river of death") wasn't nearly as terrifying as its name implies. A type of pachycephalosaur, or bone-headed dinosaur, this plant-eater was fairly lightweight, about the size of a fully grown human being. The reason for its intimidating name is that its bizarrely ornamented skull evokes the Christian conception of the devil--all horns and scales, with the slightest hint of an evil leer if you look at the fossil specimen just right.

Why did Stygimoloch have such prominent horns? As with other pachycephalosaurs, it's believed that this was a sexual adaptation--males of the species head-butted each other for the right to mate with females, and bigger horns provided a valuable edge during rutting season. (Another, less convincing theory is that Stygimoloch used its gnarly noggin to butt away from the flanks of ravenous theropods). Apart from these displays of dinosaur machismo, though, Stygimoloch was probably fairly harmless, feasting on vegetation and leaving the other dinosaurs of its late Cretaceous habit (and small, cowering mammals) alone.

Within the past few years, there has been an intriguing development on the Stygimoloch front: according to new research, the skulls of juvenile pachycephalosaurs changed drastically as they aged, much more so than paleontologists had previously suspected. Long story short, it turns out that what scientists call Stygimoloch may have been a juvenile Pachycephalosaurus, and the same reasoning may well apply to another famous thick-headed dinosaur, Dracorex hogwartsia, named after the Harry Potter movies. (This growth-stage theory applies to other dinosaurs as well: for example, the ceratopsian we call Torosaurus may simply have been an unusually elderly Triceratops individual.)

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Strauss, Bob. "Dinosaur Profile: Stygimoloch." ThoughtCo, Aug. 28, 2020, thoughtco.com/stygimoloch-1092980. Strauss, Bob. (2020, August 28). Dinosaur Profile: Stygimoloch. Retrieved from https://www.thoughtco.com/stygimoloch-1092980 Strauss, Bob. "Dinosaur Profile: Stygimoloch." ThoughtCo. https://www.thoughtco.com/stygimoloch-1092980 (accessed March 24, 2023).