Einiosaurus procurvicornis                                 Saurornitholestes langstoni
"forward-curving horned Bison lizard"        "Langston's lizard-bird raider"

Described in 1995, Einiosaurus is one of several recently discovered ceratopsians with strange and elaborate head decoration. It had long been thought that the large frills and horns of the ceratopsians served as protection from predators. While this was probably true in some cases (tyrannosaur bones have been found with marks that may have made by ceratopsine horns), it seems likely that the main function of these structures was display. This is especially true of centrosaurines, the group which includes Einiosaurus, Pachyrhinosaurus, and Styracosaurus. Unlike their cousins the ceratopsines (Triceratops, etc), centrosaurs had large openings in their frills that would have been covered in skin, probably bearing brightly colored patterns and markings. Also unlike the ceratopsines, centrosaur horns were often thin or oddly shaped. The bottle-opener shaped horn of Einiosaurus, for example, was very thin laterally and pointed downward- not something that could be used as a weapon. As an interesting note on the evolution of centrosaurines, it appears that Einiosaurus is the beginning of the line leading to Pachyrhinosaurus. The development of Pachyrhinosaurus' distinctive nasal boss can be seen developing from the curved horn of Einiosaurus, with Achelousaurus as a transitional species. Einiosaurus grew to about 6 meters long (20ft), and was found in Montana.

In the drawing, Einiosaurus approaches a sleeping dromaeosaurid- Saurornitholestes. Saurornitholestes is a raptor closely related to Deinonychus and Velociraptor, and bears the trademark sickle claws. It lived in Canada at the same time as Einiosaurus roamed Montana so it's quite likely the two would have met. I added the raptor into the drawing to provide contrast between the two main branches of dinosaurs. Einiosaurus, a highly derived ceratopsian, represents the peak of "advancement" in ornithischians. Saurornitholestes, which like all raptors is probably a flightless bird or at least extremely close relative, is one of the most advanced "classic" saurischians. As the ceratopsian watches the dromaeosaurid sleep, it's almost poignant to realize that here, close to the end of the Mesozoic era, ornithischians will soon be extinct, leaving the Earth to their feathery sister group.