Scientists say they've - rather belatedly - identified a completely new type of large, horned dinosaur after re-examining fossils originally collected in 1958.
Around 20 feet long and weighing more than two tons, the plant-eating dinosaur Xenoceratops foremostensis represents the oldest known large-bodied horned dinosaur from Canada.
"Starting 80 million years ago, the large-bodied horned dinosaurs in North America underwent an evolutionary explosion," says Dr Michael Ryan, curator of vertebrate paleontology at The Cleveland Museum of Natural History.
"Xenoceratops shows us that even the geologically oldest ceratopsids had massive spikes on their head shields, and that their cranial ornamentation would only become more elaborate as new species evolved."
Xenoceratops had a parrot-like beak, with two long brow horns above its eyes. A large frill protruded from the back of its skull, featuring two massive spikes.
"Xenoceratops provides new information on the early evolution of ceratopsids, the group of large-bodied horned dinosaurs that includes Triceratops," says Dr David Evans of the Royal Ontario Museum and University of Toronto.
"The early fossil record of ceratopsids remains scant, and this discovery highlights just how much more there is to learn about the origin of this diverse group."
The new dinosaur was identified from skull fragments from at least three individuals, currently housed in the Canadian Museum of Nature in Ottawa. Ryan and Evans stumbled upon the bones more than a decade ago and recognized them as a new type of horned dinosaur.
Evans later discovered a 50-year-old plaster field jacket at the Canadian Museum of Nature containing more skull bones from the same fossil locality and had them prepared in his lab.
"This discovery of a previously unknown species... drives home the importance of having access to scientific collections," says Kieran Shepherd, curator of paleobiology for the Canadian Museum of Nature. "The collections are an untapped source of new material for study, and offer the potential for many new discoveries."