A set of dinosaur bones unearthed in Alberta in 1916 and left unexamined on a shelf in Britain's Natural History Museum for more than 90 years has yielded an unexpected and significant discovery: a new species of horned dinosaur that is forcing scientists to rethink the dividing line between two huge, plant-eating beasts related to the well-known triceratops.

The 75-million-year-old skull fragments from several individuals of the newly identified species were found during a First World War-era dig in a dinosaur bonebed southeast of Calgary, within or just outside of today's Dinosaur Provincial Park. new dinosaur species museum,

The specimens were collected by the renowned American fossil hunter Charles H. Sternberg and his son Levi.

The family, which later was instrumental in the creation of Dinosaur Provincial Park, produced several pioneering paleontologists who went on to distinguished careers in Canadian science, including Levi with the Royal Ontario Museum and his brothers George at the University of Alberta and Charles M. Sternberg of the future Canadian Museum of Nature. horned dinosaurs,

The Alberta bones delivered to Britain 95 years ago were promptly dismissed as indecipherable "rubbish" by the London museum's geology curator. In 2000, after seeing pictures of the fossils that suggested they could, in fact, represent a new species, Canadian paleontologist Michael Ryan — now curator of vertebrate paleontology at the Cleveland Museum of Natural History — visited the British museum only to discover that the bone fragments had been misplaced.

More recently, American dinosaur expert Andrew Farke contacted Ryan to say that he'd found the Sternberg specimens and agreed that they marked an important but long-overlooked insight into the evolution of horned dinosaurs.

"The Sternbergs were really smart," said Ryan, an Ottawa-born scientist who is still affiliated with the Canadian Museum of Nature and Carleton University.

The family "would not have sent a bunch of garbage over to Britain," he told Postmedia News on Monday.

After a careful re-examination of the objects nearly a century in the making, Ryan, Farke and five other scientists from the U.S., Britain and Canada — including Darren Tanke and Dennis Braman of the Royal Tyrrell Museum of Palaeontology in Drumheller, Alta. — have concluded the bones belonged to a previously unknown dinosaur: Spinops sternbergorum.

Significantly, the new species appears to fill a "morphological gap" between two other horned dinosaurs — Styracosaurus and Centrosaurus — with the distinctive spines and hooks on the bony frill around the new animal's head offering "tantalizing" evidence of evolution from one of the previously documented species to the other, said Ryan.

The name of the new species honours the Sternberg discoverers of the fossils and also refers in Latin —"spine face" — to the spiky features extending from the animal's frill.

"I knew right away that these fossils were something unusual, and it was very exciting to learn about their convoluted history," Farke, the curator of a California paleontology museum, said in a statement announcing the discovery. "Here we have not just one, but multiple individuals of the same species, so we're confident that it's not just an odd example of a previously known species."

The team's findings have been published in the latest edition of the journal Acta Palaetontologica Polonica.

"This discovery demonstrates that new dinosaurs are found in museum collections and laboratories almost as frequently as in the field," study co-author Paul Barrett, a paleontologist at the Natural History Museum, said in a statement announcing the Canadian find. "It shows the scientific value of our historical collections and how they continue to allow new discoveries to be made."

Ryan has been involved in several dinosaur discoveries in the past few years. Last December, he co-authored the study of a new species in South Korea that filled in a 20-million-year gap in the evolutionary record of triceratops cousins.

In May 2010, he led a research team that named another new species of horned dinosaur -— Medusaceratops lokii — after the snake-haired Greek monster Medusa and the comic-book villain Loki, inspired by the Norse god of mischief.

A month later, Ryan was part of a team that documented the world's earliest-known mammal bite marks, found on 75-million-year-old dinosaur bones and other fossilized remains dug up in southern Alberta.

"This (latest) discovery is significant because it adds to our knowledge of horned dinosaur diversity in the latest Cretaceous," Ryan said in a statement. "Natural selection appears to have acted exclusively on the ornamentation on the head in these dinosaurs such that new species are appearing at a very high rate in this group."

He noted that the frills on such animals — which weighed about one tonne and measured close to five metres in length — not only protected them from carnivorous dinosaurs but also served as a decorative element for attracting mates.