A mummy of a duck-billed dinosaur reveals the 75 million-year-old species had a fleshy "comb" on its head similar to a rooster's crest.

The duck-bills were the most common dinosaur in North America during the height of their reign; they were considered to serve a similar ecological role to a modern day kangaroo or deer, a Cell Press news release reported.

Researchers knew the "gentle giant" was about 40 feet-long and had a duck-like mouth, but until now never suspected they had a fleshy appendage on their head.

"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 mummified dinosaur that revealed the remarkable feature was found near the city of Grande Prairie in west-central Alberta, Canada.

The team noticed "skin impressions" on different areas of the ancient mummified dinosaur. They noticed something even more out of the ordinary when they started to chisel away at the specimen's crest.

"An elephant's trunk or a rooster's crest might never fossilize because there's no bone in them," Bell said. "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. There's no reason that other strange fleshy structures couldn't have been present on a whole range of other dinosaurs, including T. rex or Triceratops."

Researchers have little way of knowing what the "cocks comb's" function was, but roosters use them to attract mates.

"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.