Einiosaurus is a genus of herbivorous centrosaurine ceratopsian dinosaur from the Upper Cretaceous (Campanian stage) of northwestern Montana. The name means 'buffalo lizard', in a combination of Blackfeet Indian eini and Latinized Ancient Greek sauros; the specific name (procurvicornis) means 'with a forward-curving horn' in Latin. Einiosaurus is medium-sized with an estimated body length at . History of discovery The Landslide Butte expeditions Einiosaurus is an exclusively Montanan dinosaur, and all of its known remains are currently held at the Museum of the Rockies in Bozeman, Montana. At least fifteen individuals of varying ages are represented by three adult skulls and hundreds of other bones from two low-diversity, monospecific (one species) bonebeds, which were discovered by Jack Horner in 1985 and excavated from 1985 to 1989 by Museum of the Rockies field crews. Horner had not been searching for horned dinosaurs. In the spring of 1985 he had been informed by landowner Jim Peebles that he would no longer be allowed access to the Willow Creek "Egg Mountain" site where during six years a nesting colony of Maiasaura had been excavated. This forced Horner to find an alternative site because supplies had already been bought for a new summer season and fourteen volunteers and students expected to be employed by him. He investigated two sites, Devil's Pocket and Red Rocks, that however proved to contain too few fossils. For some years, since 1982, Horner had requested from the Blackfeet Indian Tribal Council access to the Landslide Butte site. The field notes of Charles Whitney Gilmore from the 1920s indicated that dinosaur eggs could be found there. The council had consistently turned down his requests because they feared widespread disturbance of the reservation. However, one of its members, Marvin Weatherwax, had earlier in 1985 observed that an excavation by Horner of a mosasaurid in the Four Horns Lake had caused only limited damage to the landscape. In early July, the council granted Horner access to the entire reservation. Early in August, Horner's associate Bob Makela discovered the Dino Ridge Quarry, containing extensive ceratopsid remains, on the land of farmer Ricky Reagan. Continual rainfall hampered operations that year. On 20 June 1986, a crew of sixteen returned to reopen the quarry. A large and dense concentration of bones, a bonebed, was excavated, with up to forty bones per square metre being present. This was interpreted as representing an entire herd that had