A rare, mummified specimen of a duck-billed dinosaur in Canada shows their heads carried a fleshy comb similar to the roosters' red crest, paleontologists say. Duck-billed dinosaurs, gentle giants about 40 feet long, were the most common dinosaurs in North America between 75 million and 65 million years ago, but no one had suspected that they -- or any other dinosaurs -- had fleshy structures on the tops of their heads, they said. "Until now, there has been no evidence for bizarre soft-tissue display structures among dinosaurs; these findings dramatically alter our perception of the appearance and behavior of this well-known dinosaur and allow us to comment on the evolution of head crests in this group," Phil Bell from Australia's University of New England said. "It also raises the thought-provoking possibility of similar crests among other dinosaurs." The evidence comes from a dinosaur specimen, Edmontosauraus regalis, found in deposits west of the city of Grande Prairie in west-central Alberta, Canada, showing skin impressions on parts of the mummified body. "An elephant's trunk or a rooster's crest might never fossilize because there's no bone in them," Bell explained. "This is equivalent to discovering for the first time that elephants had trunks. We have lots of skulls of Edmontosaurus, but there are no clues on them that suggest they might have had a big fleshy crest." The exact purpose of such a crest is unknown, but may have been involved in mating, he said. "We might imagine a pair of male Edmontosaurus sizing each other up, bellowing, and showing off their head gear to see who was the dominant male and who is in charge of the herd," Bell said.