A newly identified species of bone-headed dinosaur that roamed what is now Alberta, Canada is being considered the oldest bonehead dinosaur known in North America, and possibly the world. (Photo : YouTube Screenshot / Cleveland Museum of Natural History )

A newly identified species of bone-headed dinosaur that roamed what is now Alberta, Canada is being considered the oldest bonehead dinosaur known in North America, and possibly the world.

The new dinosaur is named Acrotholus audeti, after Alberta rancher Roy Audet, on whose land the best specimen was discovered in 2008. The newest find was compared with a specimen found in the 1960s and conclusively labeled a new species.

"Acrotholus provides a wealth of new information on the evolution of bone-headed dinosaurs [pachycephalosaurs]. Although it is one of the earliest known members this group, its thickened skull dome is surprisingly well-developed for its geological age," said lead author Dr. David Evans of the Royal Ontario Museum and University of Toronto, in a statement. "More importantly, the unique fossil record of these animals suggests that we are only beginning to understand the diversity of small-bodied plant-eating dinosaurs."

The 85-million-year-old dinosaur had a dense, two-inch layer of bone covering its skull that may have been used in head-butting contests, as well as for shows of display amongst its peers. It walked on two legs, but was relatively small for a dinosaur, spanning about six feet from nose to tail and weighing about 40kg.

The find is an important piece of an incomplete fossil record for the period which the Acrotholus lived.

We actually don't have a very good record of dinosaurs from North America, or even the world, as a whole through this interval . . . around 85 million years ago," Evans said in a telephone interview with the Canadian Press. "So we went to the areas that exposed the sediments trying to find the fossils that would help fill in that gap in our knowledge."

The massively constructed skull domes of pachycephalosaurs are resistant to destruction, and are much more common than their relatively delicate skeletons, which often do not end up as good fossil specimens the smaller animals were more susceptible to carnivores and the weathering process, which tends to destroy the bones before they enter the fossilization process.

"We can predict that many new small dinosaur species like Acrotholus are waiting to be discovered by researchers willing to sort through the many small bones that they pick up in the field," said co-author Dr. Michael Ryan of The Cleveland Museum of Natural History. "This fully domed and mature individual suggests that there is an undiscovered, hidden diversity of small-bodied dinosaurs. So when we look back, we need to reimagine the paleoenvironment. There is an evolutionary history that we just don't know because the fossil record is incomplete. This discovery also highlights the importance of landowners, like Roy Audet, who grant access to their land and allow scientifically important finds to be made."

Evans and Ryan co-authored research describing the new species, which was published May 7, 2013 in the journal Nature Communications.