The new genus and species Borealopelta markmitchelli used camouflage to hide from predators despite being built like a tank, researchers said.
An analysis of the 18-foot-long specimen's exquisitely well-preserved form, complete with fully armoured skin, suggests that the nodosaur had predators, despite weighing more than 1,300 kilogrammes.
The researchers came to that conclusion based on studies of the dinosaur's skin, showing that the Borealopelta exhibited countershading, a common form of camouflage in which an animal's underside is lighter than its back.
The scientists say the discovery suggests that the dinosaur belonging to the nodosaur family faced predation stress from meat-eating dinosaurs.
The specimen was found by accident in 2011, by mining machine operator Shawn Funk at the Suncor Millennium Mine in Alberta.
Over the last five and a half years, museum technician Mark Mitchell spent more than 7,000 hours slowly and gently removing rock from around the specimen to reveal the exceptional, fossilised dinosaur inside.
The specimen now represents the best-preserved armoured dinosaur ever found, and one of the best dinosaur specimens in the world, the researchers said.
"The result is that the animal looks almost the same today as it did back in the Early Cretaceous. You do not need to use much imagination to reconstruct it; if you just squint your eyes a bit, you could almost believe it was sleeping.
"It will go down in science history as one of the most beautiful and best preserved dinosaur specimens - the Mona Lisa of dinosaurs," Mr Brown said.
The condition of the specimen made it possible for researchers to document the pattern and shape of scales and armour across the body.
They also used chemical analysis of organic compounds in the scales to infer the dinosaur's pigmentation pattern. Those studies revealed that the dinosaur had reddish-brown-pigmented skin with countershading across its body, researchers said.
Although countershading is common, the findings come as surprise because Borealopelta's size far exceeds that of countershaded animals alive today.
It suggests the dinosaur was under enough pressure from predators to select for concealment.