Researchers from the Royal Tyrrell Museum of Palaeontology, and the University of Calgary made the discovery in the 75-million-year-old rocks in the badlands of southern Alberta.

The ostrich-like dinosaurs, known as ornithomimids, were thought to be hairless, fleet-footed birds and were depicted as such in the Hollywood movie Jurassic Park.

But the researchers found evidence of feathers with a juvenile and two adult skeletons of ornithomimus, a species within the ornithomimid group.

"The discovery, the first to establish the existence of feathers in ornithomimids, suggests that all ostrich-like dinosaurs had feathers," according to a statement from the Alberta museum.

It said the specimens also revealed that the dinosaurs boasted a base of down-like feathers throughout their lifetime while older ones developed feathers on their arms, approximating wings.

But the dinosaurs would have been too large to fly, so the plumage might have been employed to attract a mate or in the protection of eggs during hatching.

The findings by the paleontologists Francois Therrien, curator at the Royal Tyrrell Museum, and Darla Zelenitsky, assistant professor at the University of Calgary, will be published on Friday in Science, a leading journal.

The fossils were discovered in sandstone and were the first feathered dinosaur specimens found in North America, according to the museum statement. Previously feathered dinosaur skeletons have been recovered almost exclusively from fine-grained rocks in China and Germany.

(Reporting By Russ Blinch; editing by Todd Eastham)

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