Einiosaurus, meaning “forward-curved horn”, was a medium-sized centrosaurine dinosaur from the Upper Cretaceous Period. It was discovered in the Two Medicine Formation of northwestern Montana. Roughly 15 individuals were discovered by Jack Horner in 1985 and excavated between 1985 – 1989 by field crews. The remains are held at the Museum of the Rockies in Bozeman, Montana.
The genus was formally described by Scott D. Sampson and was given the species name E. procurvicornis. Einiosaurus is portrayed with a low, forward-curving nasal horn, although this may occur only in some adults. Small horns are located over the eyes and are sometimes non-present. A pair of large spikes project backwards from the small frill. Einiosaurus was a herbivore and grew to 18 to 20 feet in length. Like other ceratopsian dinosaurs, it had a strong jaw capable of eating tough plant matter.
Studies of the bone beds may indicate that the herds that died in mass numbers may have been subject to a catastrophic event, such as a flood or a drought. It is believed that Einiosaurus was gregarious and traveled in herds. It lived in a climate that was seasonal, warm, and semi-arid. Studies of other freshwater bivalve and gastropod fossils found in the bone beds, indicate that the bones were deposited in a shallow body of water.