By Graham Duggan  

Parts of Alberta are libraries of Earth’s history, treasure troves of fossils from animals that lived millions of years ago. But sometimes, an especially rare gem is found.

In Dinosaur Cold Case, a documentary from The Nature of Things, we meet the remarkable dinosaur known as Borealopelta — preserved in eye-popping 3D.

WATCH: After six years of work, Borealopelta's body is finally revealed.

Paleontologists are solving the mystery of what killed it, how it came to rest at the bottom of a prehistoric sea and how it was preserved so perfectly.

The accidental discovery of an incredible dinosaur

In March 2011, Shawn Funk, a shovel operator at Suncor Energy’s Millennium oilsands mine north of Fort McMurray, Alta., was digging away at a large bank when he inadvertently stumbled upon Alberta’s oldest dinosaur fossil and one of the most well-preserved dinosaur fossils ever found.

“Right away, we knew it was going to be something good,” says Don Henderson, curator of dinosaurs at the Royal Tyrrell Museum in Drumheller, Alta. “But we had no idea how good it was going to be.”

After getting the fossil back to the museum, Don and his team set to work solving the 110-million-year-old mystery. 

The life and times of Borealopelta

Six years after it was found, the mysterious dino was declared a new species to science and given a proper name: Borealopelta markmitchelli. “Borealopelta” means “shield of the North,” and its species name is a nod to Mark Mitchell, the Royal Tyrrell Museum technician who spent 7,000 hours fighting for every millimetre while freeing the dinosaur from the rock it was found in.

The approximately five-and-a-half-metre-long specimen was so perfectly preserved that researchers were able to stare into the face of a real dinosaur that lived during a time when North America was a very different place.

Borealopelta was built like a tank and covered in thick armour, especially around its neck, indicating that it needed protection from predators.

At its shoulders, a massive, 51-centimetre-long spike extended out on either side. At first, it was thought these weapons could have been used for fighting other Borealopeltas, but Victoria Arbour, curator of palaeontology at the Royal BC Museum, believes they could have been used for both love and war. “When you see something like a huge spike,” says Arbour, “that could simultaneously be a signal to mates that you’re in good health.” Borealopelta’s massive shoulder spikes could have acted like a bull’s horns or an elephant’s tusks, which are used in defense when necessary but are also an indicator of status and strength.

An illustration of the dinosaur Borealopelta

An artist's impression of Borealopelta markmitchelli.

Many of the fossilized armour plates possessed a keratin sheath (the same material as our fingernails) with a thin film that allowed researchers to guess at Borealopelta’s colour.

“It was found that at least one component of Borealopelta’s colour was this reddish brown,” says Caleb Brown, a curator at the Royal Tyrrell Museum. “The pigment seemed to be concentrated on the back of the animal and not the belly, and this is consistent with this idea of countershading.”

Countershading allows animals to blend with their environment and hide from keen-eyed predators.

Although some researchers question whether the colouration was just an anomaly of fossilization, if Borealopelta, an almost 1,300-kilogram animal, did require camouflage, it must have had some terrifying predators indeed.

The terrifying dinosaur of the day, 110 million years ago, was Acrocanthosaurus, a killing machine that ruled the Cretaceous long before more well-known predators like T. rex arrived on the scene.

Could an attack from an Acrocanthosaurus have been the cause of Borealopelta’s death? In a simulated test, researchers found that Acrocanthosaurus’s bite would have done some serious damage to Borealopelta, and it was likely one of its main predators. But this particular specimen was found in such pristine condition, with no signs of trauma, that it must have died another way...

Dino’s last meal may be the key to its mysterious death

After studying the location the fossil was found, the team determined that Borealopelta likely came to rest, belly up, at the bottom of a prehistoric sea. In an extremely rare find, the stomach contents of Borealopelta were preserved along with its body, providing an important clue as to how it got there.

Paleobotanist David Greenwood examined Borealopelta’s miraculously fossilized last meal and discovered twigs and ferns. Incredibly, the twigs appeared to be in mid-growth, indicating that they were eaten during the wet season, when extreme storms and flash floods would have been a real problem. On the coastal plains where Borealopelta lived, a rapid rise in water level could have caught it off guard — and Borealopelta was not built for swimming.

MORE:
100 million years ago, Alberta was a giant sea, surrounded by tropical forests
"Destroyer of shins" — a newly discovered dinosaur may have used its armour for more than defence
Sexing a fossil that's millions of years old

Borealopelta is preserved in incredible detail

If Borealopelta drowned in a torrent that swept it away, how did it come to rest upside down on the sea floor?

Henderson and Brown went back to the records to see the position in which other armoured dinosaur fossils in Alberta were found, and discovered that about 70 per cent of these dinosaurs were also found on their backs.

“As [Borealopelta] started to rot,” Brown reasons, “gases built up within the body cavity.” In the water, the rest was simple physics. “That bloated body, with the soft belly and dense back, causes it to flip over,” says Henderson. “Its arms and legs [would have been] sticking up in the air.”

With its stiff limbs acting as sails, Borealopelta would have caught the wind and literally sailed out to sea, travelling a long way into open water. Then, says Henderson, “it goes pop … and it goes down like a stone.” Borealopelta would have hit the sea floor with force, burying itself in sediment that was disturbed from the impact — key to the fossil’s incredible preservation.

Through a chemical reaction, this sediment would have formed a natural concrete, preserving the body within its own sarcophagus. Henderson and Brown suspect this is how Borealopelta was protected from immense pressure and decay.

Safe within this natural time capsule, the nodosaur waited 110 million years until one fateful day, when a miner in Alberta came across a miraculous find and Borealopelta’s mysteries were unearthed.

Watch Dinosaur Cold Case on The Nature of Things.

The Wild Canadian Year

Wild Canadian Year


Visit our website to watch the series online, discover extra behind-the-scenes stories and view Canada's nature scenes in 360. Visit Wild Canadian Year

From CBC Kids

The Nature of Thingies