Pieces of skulls from the recently named Xenoceratops were originally dug up from rocky sediments in southern Alberta sediments in 1958.
However, a pair of paleontologists rediscovered the bones a decade ago and gradually pieced together the sweeping neck plate of the four-footed, horn-headed giants.
Their work has been published in the October issue of the Canadian Journal of Earth Sciences.
The 3,000-kilogram creatures used their beak-like mouths to munch on plants and had a fearsome appearance due to a sweeping neck shield topped by two protruding spikes.
Canadian paleontologists Michael Ryan and David Evans say in their paper that the fossils were first discovered at a dig near Foremost, Alta., by American paleontologist Jann Langston Jr., who was working in Canada at the time.
They said Langston, now a professor emeritus at the University of Texas at Austin, left the bone fragments wrapped up and shelved in the Canadian Museum of Nature in Ottawa.
Evans said he and Ryan started to wonder in 2003 about two pieces of the neck shield — known as the frill — stored loosely in metal cabinets at the Ottawa museum. One was a spike and the other was an unusually large socket, he recalled.
He said the pieces aroused his curiosity in part because they came from rock formations that contained some of the oldest dinosaur fossils in Alberta.
That led them to investigate further in 2009, when they found Langston's bone fragments from at least three animals, wrapped in a plaster and burlap casing. They were helped by Kieran Shepherd, curator of paleobiology for the Canadian Museum of Nature.
"Sure enough there was much more material and that was the key to identifying the new species," Evans said in an interview.
The paleontologists took the fragments to the Royal Ontario Museum in Toronto, where they pieced together the metre-long piece of neck bone and then returned it to Ottawa.
They named the animal with the Greek words meaning "alien-horned face," due in part to its unusual appearance.
Ryan, curator of vertebrate paleontology at the Cleveland Museum of Natural History, said he gradually learned that they had come upon the oldest known big-horned dinosaurs known as ceratopsids.
The herbivores are part of a family that later diversified, featuring a remarkable array of varying horn and frill configurations, said Ryan.
Orphaned bones like the ones they came across sometimes only make sense decades after they're found, he added.
"The early fossil record of ceratopsids remains scant," said Ryan. "This discovery highlights just how much more there is to learn about the origin of this diverse group."
The scientists also suggest the size of the horns may have played a role in reproductive success — the bigger the horn, the more attractive they were to their female counterparts.
"We feel they were actually used for mate recognition. ... We think the male dinosaurs with the biggest horns were the most reproductively successful," said Ryan, though he added that this theory is a source of debate.
"It was that ornamental arms race on their skulls that drove the evolution."
This dinosaur is just the latest in a series of new finds made by Ryan and Evans as part of their Southern Alberta Dinosaur Project, designed to improve knowledge of late Cretaceous dinosaurs and their evolution.
The project focuses on the paleontology of some of the oldest dinosaur-bearing rocks in Alberta, which is not as well studied as that of the famous badlands of Dinosaur Provincial Park and Drumheller.
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