A Dinosaur So Well Preserved, It Looks Like a Statue
Borealopelta, discovered accidentally by Canadian miners, is one of the most spectacular fossil finds of all time.
In March 2011, a construction worker named Shawn Funk visited an impressive dinosaur collection at the Royal Tyrrell Museum in Alberta. As he walked through halls full of ancient bones, he had no idea that a week later, he’d add to their ranks by finding one of the most spectacular dinosaur fossils of all time. It’s an animal so well preserved that its skeleton can’t be seen for the skin and soft tissues that still cover it.
When we look at dinosaurs in museums, it takes imagination to plaster flesh and skin on top of the bones. But for the dinosaur that Funk unearthed—a 110-million-year-old creature named Borealopelta—imagination isn’t necessary. It looks like a sculpture. And based on pigments that still lurk within the skin, scientists think they know what colors the animal had. “If someone wants to come face to face with a dinosaur, and see what it actually looked like, this is the one for that,” says Caleb Brown from the Royal Tyrrell Museum, who has studied the animal.
Borealopelta was one of the ankylosaurs—a group of heavy-set, low-slung, tank-like dinosaurs. It lacked the shin-thwacking tail clubs that some of its relatives wielded, but its back was covered in heavy, armored scales, and a pair of 20-inch-long spikes jutted from its shoulders. It weighed 1.5 tons and was 20 feet from foot to tail. And it probably couldn’t swim very well.
Somehow, this particular individual ended up at sea. Perhaps it got careless on a shoreline. Perhaps it drowned in a flood and was washed out to sea. Either way, gases started building up in its body, causing it to float belly-up. As those gases released, the dead dinosaur sank, and hit the ocean floor hard enough to leave a small crater. Before sharks had a chance to nibble it, or worms had a chance to burrow into its bones, it was quickly smothered by fine sediment and sealed off from the outside world. There it remained for millions of years, until March 11, 2011, when an excavator bit into it.
By then, the ocean floor that had swallowed the dinosaur had become the Millennium Mine—a huge oil sand quarry in northern Alberta. Funk, a heavy-equipment operator, was digging in the mine when he noticed a change in the texture and color of the underlying rock. Alberta is rich in fossils, and construction crews know that any dig could potentially yield fresh bones. Funk called his supervisor, and they alerted the Royal Tyrrell Museum.
Two days later, Donald Henderson and Darren Tanke flew over, expecting to find the bones of a marine reptile—a long-necked plesiosaur, perhaps, or a dolphin-like ichthyosaur, fossils of which are commonly found in Alberta. But on arrival, they realized that the miners had actually uncovered something special—a dinosaur. Excavators had already smashed through the animal’s tail and rear end, which were permanently lost. But most of the creature was still there, and even then, it was clear that it had rare features like fossilized skin. “I don’t think anyone realized how magnificent the specimen was going to be,” Brown says.
After three days of intense safety training, the team began to liberate the dinosaur—a process that took two weeks of laborious 12-hour shifts. “All the mine staff from every level and department were tripping over themselves offering to help,” Henderson later wrote in The Guardian. They eventually isolated a single 15,000-pound block that contained the animal, and that was jacketed in burlap and plaster. But as they lifted the block, the jacket split and the block collapsed—a horrifying moment, immortalized on video.
Fortunately, everything broke cleanly and in big pieces, all of which were shipped to the museum. One might think that a large team would process the fossil, but the museum’s team of a dozen technicians is already stretched thin. Every year, Alberta discovers more dinosaur specimens than the Royal Tyrrell can possibly collect, so many are just left in the ground. Of those that are recovered, many linger in warehouses. The ankylosaur clearly deserved special attention, but because of its delicate state, it was assigned to a single pair of steady hands.
Those hands belonged to technician Mark Mitchell, who compares the process of separating dinosaur from rock to chipping concrete chunks from a surface as soft as compressed talcum powder. It took him 7,000 hours over 5.5 years, during which he did little else. For that reason, the dinosaur carries his name—Borealopelta markmitchelli. (The first half comes from the Latin for “northern shield.”)
The finished specimen, now on display to the public, is both breathtaking and reassuring. It’s hard to reconstruct what animals look like based on bones alone—an elephant’s skeleton bears no obvious trace of its trunk, and a bird’s skeleton offers few clues about the thick overlying plumage. So paleontologists have debated whether giant dinosaurs had trunks, or whether all species were covered in some form of feathers. But for Borealopelta, “what we thought this animal looked like based on the skeleton is what is actually looked like,” Brown says. “And it probably mostly had scaly skin.”
It’s a good time to be interested in ankylosaurs. Another new and well-preserved species was unveiled last month—Zuul crurivastator, named after the monster from Ghostbusters and the Latin for “destroyer of shins.” “It's so wonderful to have two amazing new ankylosaur skeletons with the armor in place,” says Victoria Arbour from the Royal Ontario Museum in Toronto, who named and described Zuul. “It really helps us visualize what these weird dinosaurs would have looked like while alive.”
The shape of Borealopelta’s face and body are plain to see, but its remains have long lost their natural color and are now tar-black with ochre spots. Still, they contain chemical clues about their original hues. To interpret those clues, the Royal Tyrrell team turned to Jakob Vinther from the University of Bristol.
In 2007, Vinther started studying tiny pigmented structures called melanosomes, found in fossilized dinosaur feathers. These come in two types—spherical ones that are reddish-brown, and sausage-shaped ones that are black or gray. By looking at the spread of melanosomes over a dinosaur’s body, Vinther could reconstruct the palettes of these extinct animals. He worked out that the small hunter Anchiornis had a black-and-gray body with a red crest, while the four-winged Microraptor shared the glossy black plumage of a modern starling, and that the parrot-faced Psittacosaurus had a dark back and light belly.
Vinther couldn’t find any melanosomes in Borealopelta’s skin. But he did find traces of chemicals called benzothiazoles, which are part of reddish-brown pigments. Based on the distribution of these chemicals, the team thinks that their ankylosaur had the same pattern as Psittacosaurus—a rust-colored head and back, and a light-colored belly.
This pattern—dark on top and light below—is called countershading, and is one of most common forms of camouflage in nature. If an animal was evenly colored all over, its own shadow would render its bottom half darker than its top half, making it easy to spot. Countershading, by lightening the bottom and darkening the top, cancels out the effect of the shadow and makes animals look flat and inconspicuous.
On land, countershading is a common trick among animals that need to hide from predators, like deer, antelope, and wild horses. But once prey animals get big enough, their bulk provides them with enough defense—that’s why rhinos and elephants are just uniformly gray. Borealopelta bucks that trend. It’s rhino-sized, and much bigger than any countershaded land animal around today. “The fact that this massive armored dinosaur with these huge spines still had countershading tells us that it was a common meal for the predators of the time,” Brown says. Such predators might have included Acrocanthosaurus, as long as Tyrannosaurus but more lightly built.
It might seem obvious that plant-eaters like Borealopelta were hunted by large predators. But “some people believed that an animal like this was predator-proof,” Brown says. “To get into the animal, you would have had to flip it onto its belly—and it’s huge.” Clearly, though, enough predators were doing that to drive the evolution of a camouflaged color scheme.
But Alison Moyer from Drexel University, who studies ancient molecules, isn’t convinced for several reasons. For example, she notes that benzothiazoles are naturally found in the sea, and it’s not clear if the traces found in the Borealopelta specimen came from the dinosaur itself. It’s also unclear how the animal’s pigments would have changed as it floated belly-up on the ocean surface. “We know a lot about what happens to human skin in a bloat-and-float, and there’s drastic changes between the side exposed to the water and the side exposed to the air,” Moyer says. For a dinosaur, “we don’t know anything about how their soft tissues degrade.”
“There’s still a lot of healthy scientific skepticism around the interpretation of ancient biomolecules like pigments,” Arbour says. “It’s just really hard to collect enough data to let us reconstruct color patterns on extinct dinosaurs. But for now, I am just excited about the exceptional preservation of this specimen and what we’ll be able to glean from it in the long run. It’s just so beautiful!”
The team members are now trying to analyze the ankylosaur’s gut contents, to see if they can identify its last meal. They’re also trying to analyze its bones. That’s usually the easy bit when it comes to studying dinosaurs, but with Borealopelta, the skeleton is obscured by skin. “We’ve tried to use CT scanners but so far that hasn’t been successful. The rock is too dense, but we hope future technology will let us look inside. Ironically, it’s too well preserved!”