Michael J. Ryan is shown here with the holotype skull of the recently discovered horned dinosaur, Albertaceratops nesmoi, named for Cecil Nesmo, an Alberta rancher who helped the fossil hunters. ((Cleveland Museum of Natural History, Chad Kerychuk/Digital Dream Machine/Associated Press))

A recently discovered species of dinosaur has been named in honour of an Alberta rancher in recognition of his efforts to help fossil hunters.

News of the discovery, Albertaceratops nesmoi, was published in this month's Journal of Paleontology by Michael Ryan, curator of vertebrate paleontology for the Cleveland Museum of Natural History.

Ryan was a graduate student at the University of Calgary and was camping on Cecil Nesmo's property when he dug up the fossil six years ago.

"It's quite an honour for me," said Nesmo, 62, who's lived for 58 years on a ranch near Manyberries, a small town about 290 kilometres southeast of Calgary.

Ryan said the large, plant-eating reptile roamed the earth some 78 million years ago. It was as heavy as a half-tonne pickup, he said, with horns as thick as a human arm.

"If you thought of the largest bull you could think of …that's probably the size range this animal was like," said Ryan.

University of Pennsylvania paleontologist Peter Dodd said the discovery provides an important evolutionary link in the dinosaur family known as centrosaurs, which had horns and large bony frills covering their necks.

"It was sort of the grandfather or great-uncle of the really diverse horned dinosaurs that came after it,"Dodd said.

The oldest known horned dinosaur in North America is called Zuniceratops. It lived 12 million years beforeRyan's find and had large horns.

That makes Albertaceratops nesmoi an intermediate between older forms with large horns, and the small-horned relatives that followed, said Utah paleontologist Jim Kirkland, who, with Douglas Wolfe, identified Zuniceratops in New Mexico in 1998.

Nesmo said his ranch has been known for decades as a rich area for fossils, noting that he can remember researchers visiting it when he was just four years old.

"When we find good specimens, we always direct the right people to it," Nesmo said.