Paleontologists have named a new species of "bone-headed" dinosaur from Canada, so called for a domed skull above its eyes that was almost 2 inches thick.

Two fossil specimens of the diminutive dinosaur dubbed Acrotholus audeti, from a class of dinosaurs called pachycephalosaur for their distinctive skulls, have been found in Alberta, the scientists said.

At just 6 feet long, including a long tail, and weighing only about 90 pounds, the newly identified plant-eating dinosaur represents the oldest bone-headed dinosaur in North America, and possibly the world, they said.

The first fossil specimen was discovered almost 50 years ago but a much better example was found in 2008 during a field expedition organized by the Royal Ontario Museum and University of Toronto, and the Cleveland Museum of Natural History.

Research describing the new species was published Tuesday in the journal Nature Communications.

"Acrotholus provides a wealth of new information on the evolution of bone-headed dinosaurs," Royal Ontario Museum paleontologist David Evans said. "Although it is one of the earliest known members this group, its thickened skull dome is surprisingly well-developed for its geological age."

Acrotholus lived about 85 million years ago.

"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," Evans said.