Acrotholus audeti was plant-eating dinosaur that walked on two legs and weighed about 40 kilograms. (Julius Csotonyi)
Scientists have discovered a new species of dinosaur that once lived in what is now southern Alberta and dates back to 85 million years ago.
It's called the Acrotholus audeti or bone-headed dinosaur and is said to be the oldest in North America, and possibly the world.
Apparently, it was about the size of a big dog (like a German shepherd) and had a dome shaped skull made of solid bone more than 10cm (4 inches) thick, which might have been used to head-butt other dinosaurs.
Scientists say it was a plant eater, walked on two legs, weighed about 40 kg (88 pounds) and wasn't very tall - only up to an adult person's knee.
University of Toronto researchers say the new species, revealed in the journal Nature Communications, is a key finding in the evolutionary study of dinosaurs.
They believe more small dinosaurs like this one will be discovered, which would suggest the dinosaur population was more diverse than once thought, and that perhaps it wasn't just giant dinosaurs running around, crushing all the smaller ones.
"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," said the study's lead author David Evans, curator of vertebrate paleontology at the Royal Ontario Museum.
"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," he told CBC News.
Scientists came across this fossil (left photo: Brian Boyle/ROM) on the land of a cattle rancher in 2008, and found it was almost perfectly preserved and intact.
Evans said not that much is known about small dinosaurs, as scientists rarely get the chance to study their skeletons.
That's "because the bones of small (dinosaurs) are more susceptible to carnivores and weathering processes," Evans said. "The bones of small animals tend to get destroyed before they enter the fossil record."
Bone-headed dinosaurs are officially called pachycephalosaurs.
Evans and his team looked at all 600 pachycephalosaur fossils that have been found to date and concluded there were at least 16 varieties of animals with the bone head, including the Acrotholus (which comes from the Greek words for "high dome").
An exhibit featuring the Acrotholus fossils will be featured at the Royal Ontario Museum later this month.
And this Saturday, May 11, David Evans will be on CBC Radio's Quirks & Quarks with Bob McDonald at noon.