Two Alberta fishermen have hooked the catch of a lifetime: a never-before-seen, mostly intact dinosaur fossil believed to be more than 80 million years old.

Researchers at the Royal Tyrrell Museum of Paleontology say the ancient remains appear to be from a new species of hadrosaur, a duck-billed, plant-eating class of dinosaur characterized by an abnormally-shaped, elongated skull.

They say the fossil, which includes parts of the dinosaur's neck, chest and skull, likely broke loose from the riverbank and washed into the Castle River during the 2013 summer floods in Alberta.

The fishermen were on the Castle River in Southern Alberta when they spotted the dinosaur fossil embedded in a metre-long river boulder. They immediately contacted the Royal Tyrrell Museum of Paleontology in Drumheller when they recognized what it was. Museum staff airlifted the rock-encased fossil to their facility in October.

Museum researchers have collected and catalogued a number of fossils believed to have been unearthed in the 2013 flood, but this latest discovery is already being billed as one of their more significant finds.

They say the fossil is rare in that the dinosaur skull appears to be intact and in its original shape. Most skulls are found either flattened or crushed, they said.

The museum posted a video of the find on YouTube Wednesday.

"This specimen is coming from a place where we haven't had dinosaurs before," Donald Henderson, the museum's curator of dinosaurs, says in the video. "This will be a significant specimen. We're going to learn a lot from it."

Henderson says the boulder weighs more than a metric tonne and is composed of an extremely hard form of rock that allowed it to survive erosion in the river.

"It's the hardness of the rock which preserved the specimen roughly intact, while being beaten around in the river. But that hardness is going to make it difficult to prepare," he says.

Parts of the dinosaur's spine, jaw and teeth are visible in the rock.

Scientists at the museum will examine the fossil in more detail next year, when they hope to fully determine whether it does indeed belong to a new species.

Museum employees have collected a number of fossil specimens from the Oldman River, Highwood River, Bow River and Sheep River systems in the last year. Many of them were dislodged by the torrent of water that swept through parts of Alberta in late June and early July of 2013.