Borealopelta markmitchelli emerged from darkness in 2017, millions of years after its death. Scientists looked at a remarkably preserved dinosaur fossil with skin, armor coating, side spikes, most of its body and feet, and even its face intact after fossilization. Dr. Donald Henderson, dinosaur curator at Royal Tyrrell Museum, called it a “one-in-a-billion find” – and he meant this literally.

Paleontologists know this fossil serves as a crucial key for understanding Early Cretaceous ecology. Scientists studied its anatomy, armor, and final meal, gaining unexpected insights into an animal that vanished approximately 100 million years ago.

From Mining Machine to Museum Marvel

Borealopelta’s journey back to daylight began in 2011 at Suncor mine in Alberta, Canada. Shovel operator Shawn Funk noticed something unusual after taking a chunk from a cliff. Mining operations halt rarely at this massive facility, which runs continuously, but managers stopped work and contacted Royal Tyrrell Museum.

Dr. Henderson and Darren Tanke arrived expecting to find marine reptile remains. Previous discoveries in similar rock formations yielded plesiosaurs and ichthyosaurs. “Our thinking was biased,” Henderson explained. “Everybody who looked at it here thought, ‘This is a plesiosaur flipper!’ Because what else could it be? When you looked at the bones, it wasn’t making sense as a plesiosaur. It is amazing how your thought process wants you to see something. Eventually you have to admit: It’s not there.”

How a Land Dino Ended Up at Sea

Finding a land-dwelling plant-eater preserved in an ancient seabed initially surprised researchers, though several ankylosaurs have appeared in marine environments. Scientists believe flooding swept its carcass from a river to sea, where it floated upside-down for days before sinking.

“Bloat-and-float” kept it buoyant as postmortem gases built up. Models suggest its heavy armor rolled it onto its back – a position likely preventing ocean predators from scavenging. Once gases expelled, Borealopelta sank beyond 50 meters deep, evidenced by green phosphate mineral formation.

“We can see it went in water deeper than 50 meters because it was preserved with a mineral called glauconite, a green phosphate mineral. And it only forms in cooler temperatures in water deeper than 50 meters,” explained Henderson.

He also told Ars that this environment probably discouraged scavenging, saying, “It was probably a region where [long-necked] plesiosaurs and big fish didn’t like to go. It was too cold and too dark, and [there was] nothing to eat. And there were very few trace fossils in the sediments around it. So there wasn’t much in the way of worms and crustaceans and bivalves and things in there to further digest it. It was just a nice set of conditions in the seabed that had very low biological activity that led to that preservation.”

A thick, hard concretion formed around it, maintaining its 3D shape rather than flattening under pressure like most fossils. This rock encasement prevented bacteria from breaking down skin tissues.

7,000 Hours of Painstaking Work

Excavation took 14 days, with researchers bringing enormous blocks back to Royal Tyrrell Museum. Senior preparation technician Mark Mitchell faced an extraordinary task – separating fossil from stone. Working seven hours daily for five and a half years, Mitchell spent approximately 7,000 hours on this project.

“During preparation,” Mitchell explained, “I would piece together the blocks like a puzzle, and the animal started to really take shape. It got me excited to start on the next block to see the animal come together. Right before Christmas one year, I had pieced together both sides of the neck and the head, and you could really appreciate the impressiveness of the specimen and that this was a living creature with astounding preservation.”

Few people can claim they were first to see an extinct animal’s actual face. Mitchell described that experience as “absolutely amazing. This was the first dinosaur I’ve worked on with skin actually covering the skull, so being able to see what this animal looked like when it was alive was really cool.”

He was also “amazed at the skin impressions on the bottom (pad) of the foot. These matched the patterns seen in footprints left behind by other ankylosaurs preserved in Alberta [and British Columbia].”

Museum officials named the specimen after him – he’s the “Mitchell” in Borealopelta markmitchelli.

Armor, Spikes, and Dino Fashion

Borealopelta belongs to nodosaurs – four-legged ankylosaurs with straight tails rather than tail clubs. Dr. Caleb Brown, curator of dinosaur systematics and evolution at Royal Tyrrell Museum, led studies on this fossil.

Armored dinosaurs like nodosaurs carry bony structures called osteoderms over their skin. Since skin rarely survives fossilization, osteoderms usually scatter around ankylosaur bones. Borealopelta offers a rare opportunity to see every osteoderm’s exact location on most of its body.

Brown meticulously took 605 measurements of 172 different osteoderms. “Data collection and making figures are two of my favorite parts of my job,” he said. “I love when large sample sizes exist for dinosaur fossils because we can collect a large amount of data and test hypotheses. This usually means many specimens of a certain type of animal but in this case was one specimen preserving many different features.”

“I should also point out that the work measuring and drawing the specimen pales in comparison to the amount of work that went into preparing it,” Brown added in a nod to fossil preparator Mark Mitchell.

Understanding osteoderm placement helps paleontologists reconstruct tissues on ankylosaur fossils found without intact structures. As Henderson explained, “For the previous 100–120 years, we’ve known about [ankylosaurs and nodosaurs]. The armor has always been sort of our best guess. And here we had it all in place.”

“Many armored dinosaur skeletons are preserved disarticulated, meaning their bones are all jumbled up,” Brown told Ars. “So while much of the osteoderms are preserved, we do not necessarily know where each of those osteoderms would be placed in life. Having the osteoderms preserved in life position in this specimen, and other specimens, can give us clues as to how to reconstruct those specimens where the position of the armor is less clear.”

Weighing approximately 1,300 kg (almost 3,000 pounds) with a length around 5.5 meters (18 feet), Borealopelta ranked as a large herbivore. Researchers suggest its side spikes may have served for display rather than defense – possibly attracting mates.

Big, Armored, and… Hiding from Predators?

Brown and colleagues discovered that Borealopelta used countershading coloration, with darker upper body fading to lighter underbelly. Many modern species use this strategy to hide from predators, but among living land herbivores, countershading appears only in smaller prey animals – never in creatures similar to ankylosaur size like elephants or hippos.

Fossil footprints and remains from similar-aged rock formations reveal Borealopelta coexisted with apex predators like Allosaurs and Carcharodontosaurs. Despite its size and armor, this dinosaur apparently needed camouflage – a chilling insight into Cretaceous survival needs.

Scientists uncovered stomach contents – a discovery almost as rare as Borealopelta itself. Analysis showed mostly fern leaves, woody stems, and burnt plant fragments. Growth rings in one stem indicated death in late spring or mid-summer. Burnt material points to recent wildfire, where ferns may have grown in a recovering landscape. Research suggests Early Cretaceous forests experienced frequent fires every 20-40 years.

By studying plants from nearby fossil locations, scientists determined Borealopelta may have specifically preferred ferns despite various flora available. However, stomach contents represent only several hours before death – not necessarily its typical diet.

Peeking Inside a Dino Time Capsule

Future research focuses on stomach contents and skin. Henderson wants to study parts typically available in dinosaur fossils – the skeleton. “This isn’t your average dinosaur,” he said. “The skeleton is completely covered up by skin and armor!”

“We took the skull to a place in Vancouver where they did industrial-grade CT scanning,” he added. “They regularly CT scan blocks of iron to look for air bubbles and cracks. This rock is so dense that their high-powered X-rays could not penetrate the skull.” He hopes scanning technology improves soon.

“The specimen is impressive in its own right, even without any of the research,” Brown wrote. “The combination of preserved soft tissues and retained 3D shape results in the animal looking much like it did back in the Cretaceous… I think ongoing and future research, specifically looking at features such as the preserved skin and stomach contents will continue to add to our understanding of this animal.”

Lightning Strikes Once in a Billion

Henderson compares this discovery to lightning striking just once. “They’ve been digging for 11 years [at the Suncor mine], everybody knows what to look for”—and yet nothing. Moreover, he said, “you could roughly squeeze that whole Borealopelta body in just over one and a half cubic meters. If you figure they’ve dug one and a half billion cubic meters, that fossil truly is one in a billion.”

Borealopelta gives us an unprecedented window into prehistory. Its exceptional preservation provided answers to questions scientists previously could only guess at – and raised fascinating new ones about how armored giants navigated dangerous Cretaceous landscapes.