Monoclonius

Monoclonius (meaning "single sprout") is an extinct dubious genus of herbivorous ceratopsian dinosaur found in the Late Cretaceous layers of the Judith River Formation in Montana, United States, and the uppermost rock layers of the Dinosaur Park Formation in Alberta, Canada dated to between 75 and 74.6 million years ago.

Monoclonius was first named by Edward Drinker Cope in 1876. Later, much taxonomic confusion was caused by the discovery of Centrosaurus, a very similar genus of ceratopsian that is known from much better remains. Today, typical Monoclonius specimens are usually believed to be juvenile Centrosaurus or subadults, in many cases of other genera such as Centrosaurus. Those specimens that remain under the name Monoclonius are mostly too incomplete or immature to be confidently matched with adult specimens from the same time and place. This is especially true of the type species, Monoclonius crassus. Therefore, Monoclonius is often considered a nomen dubium now, pending further study.

History

Cope's initial discoveries

Monoclonius was Edward Drinker Cope's third named ceratopsian, after Agathaumas and Polyonax. Several fossils were found by Cope, assisted by a young Charles Hazelius Sternberg, in the summer of 1876 near the Judith River in Chouteau County, Montana, only about a hundred miles (some 150 km) from the site of the Battle of the Little Bighorn, fought that June. The finds did not represent a single, let alone articulated, skeleton, but came from different locations.