Torosaurus

Torosaurus was a 8m long and 7 tonnes "bird-hipped" cretaceous dinosaur from the group known as the horn-faced dinosaurs or ceratopsians. It was a large sociable herbivore with a strong beak, able to handle the toughest vegetation including small branches. It had powerful legs that were short at the front and longer at the back, which gave it a very stable posture.
Its enormous 2.6 metre crested skull is the largest known from any land animal. It had two brow horns, a short nose horn and a long-frilled crest giving it a fierce appearance. Many theories have been proposed for its use: originally it was thought that it was primarily used for defence or to house massive muscles for eating tough vegetation.
However, the presence of two large holes in its crest have led palaeontologists to believe that it was used for sexual display and to intimidate opponents. The holes would have been covered by stretched skin creating vivid eye-spots when flushed with blood.
Torosaurus was discovered by John B. Hatcher and named in 1891. Evidence for the Torosaurus includes several partial skulls and incomplete skeletons from Alberta and Saskatchewan in Canada and states in the USA, including Montana, Texas, Utah, and Wyoming. In all, 21 skeleton fragments have been identified as Torosaurus, but there is debate amongst paleontologists as to how many species of Torosaurus existed.