Monoclonius. Wikimedia Commons


Monoclonius (Greek for "single sprout"); pronounced MAH-no-CLONE-ee-us


Woodlands of North America

Historical Period:

Late Cretaceous (75 million years ago)

Size and Weight:

About 15 feet long and one ton



Distinguishing Characteristics:

Moderate size; large, frilled skull with single horn

About Monoclonius

If Monoclonius hadn't been named by the famous paleontologist Edward Drinker Cope in 1876, after a fossil specimen discovered in Montana, it might long ago have receded into the mists of dinosaur history. Today, many paleontologists believe that the "type fossil" of this ceratopsian should properly be assigned to Centrosaurus, which had a strikingly similar, massively ornamented frill and one big horn jutting out of the end of its snout. Complicating matters further is the fact that most Monoclonius specimens appear to be of juveniles or sub-adults, which has made it more difficult to compare these two horned, frilled dinosaurs on a conclusive adult-to-adult basis.

One common misconception about Monoclonius is that it was named after the single horn on its snout (its name is often mistranslated from the Greek as "single horn"). In fact, the Greek root "clonius" means "sprout," and Cope was referring to the structure of this ceratopsian's teeth, not its skull. In the same paper in which he created the genus Monoclonius, Cope also erected "Diclonius," about which we know next to nothing other than that it was a type of hadrosaur (duck-billed dinosaur) roughly contemporary with Monoclonius. (We won't even mention two other obscure ceratopsians that Cope named before Monoclonius, Agathaumas and Polyonax.)

Although it is now considered to be a nomen dubium--that is, a "doubtful name"--Monoclonius gained a lot of traction in the paleontology community in the decades after its discovery. Before Monoclonius was eventually "synonymized" with Centrosaurus, researchers managed to name no fewer than sixteen separate species, many of which have since been promoted to their own genera. For example, Monoclonius albertensis is now a species of Styracosaurus; M. montanensis is now a species of Brachyceratops; and M. belli is now a species of Chasmosaurus.

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Your Citation
Strauss, Bob. "Monoclonius." ThoughtCo, Aug. 25, 2020, Strauss, Bob. (2020, August 25). Monoclonius. Retrieved from Strauss, Bob. "Monoclonius." ThoughtCo. (accessed March 29, 2023).