The duck-billed dinosaur doesn't appear to have used its massive crest for sniffing out scents, as thought, says a Canadian scientist who studied a cast of the dino's brain.

Lambeosaurs, the duck-billed dinosaurs that once roamed Alberta's badlands, have large nasal passages on the top of their skulls that resemble the fleshy crests on a rooster.

For years, scientists suspected the plant-eating dinosaurs used the hollow crests for their sense of smell. Other ideas included a snorkel to feed underwater, and brain coolers.

Lambeosaurus (Courtesy: Royal Tyrrell Museum of Palaeontology)

David Evans, a doctoral student in zoology at the University of Toronto at Mississauga, has ruled out that the crests evolved to boost the animal's sense of smell.

Evans used fossilized bone fragments from a duck-billed dinosaur to reconstruct its brain cavity, which he combined with neurological data.

Based on his study of the brain case, there's no signs of nerves curling upward as expected if used for the sense of smell, Evans reports in the January issue of the journal Paleobiology.

Rather, the model suggests lambeosaur's main smelling system is found in front of the eyes – the same place as in most four-legged animals. The duck-billed version is more compact than in other dinosaurs.

Crests appear differently, from fan-shaped to tubular, among various species of lambeosaurs.

These shape differences point to a behavioural role for the crests, such as calling out to members of the same species to attract mates or warn of predators, Evans said.

A showy display for mating, like the feather crests sported by some birds, also remains a possibility. Crest evolution likely involved more than one function, he wrote.

The research was funded by the Natural Sciences and Engineering Research Council of Canada.