About 110 million years ago in what’s now Alberta, Canada, a dinosaur resembling a 2,800-pound pineapple ended up dead in a river.
Today, that dinosaur is one of the best fossils of its kind ever found—and now, it has a name: Borealopelta markmitchelli, a plant-eating, armored dinosaur called a nodosaur that lived during the Cretaceous period. After death, its carcass ended up back-first on the muddy floor of an ancient seaway, where its front half was preserved in 3-D with extraordinary detail.
Unearthed by accident in 2011 and unveiled at Alberta’s Royal Tyrrell Museum in May, the fossil immediately offered the world an unprecedented glimpse into the anatomy and life of armored dinosaurs.
“It’s a beautiful specimen,” says Victoria Arbour, a postdoctoral researcher at the Royal Ontario Museum who is studying another well-preserved armored dinosaur called Zuul crurivastator. “It’s great to have specimens like this one and Zuul that give us an idea of what these dinosaurs looked like when they were alive.”
In addition to announcing its name, the first scientific description of the nodosaur, published today in the journal Current Biology, is revealing even more of its secrets.
“We knew six years ago that this was going to be special,” says Don Henderson, the Royal Tyrrell Museum’s curator of dinosaurs. “I don’t think we realized how special it was.”
Leaving a Mark on Science
It’s been a long road for Borealopelta. The creature’s subterranean isolation came to an end on March 21, 2011, when heavy-equipment operator Shawn Funk stumbled on the fossil in an oil sands mine in northern Alberta operated by energy company Suncor.
The fossil then traveled to the Royal Tyrrell Museum’s preparation lab, where technician Mark Mitchell painstakingly chipped away the surrounding rock—a feat that took him more than 7,000 hours over nearly six years. The skull alone took some eight months to extricate.
“Were it not for his commitment, [Borealopelta] probably would have never come to light,” says Caleb Brown, a postdoctoral researcher at the Royal Tyrrell Museum and the new study’s lead author. “It’s an extreme amount of effort. The preparators are often the unsung heroes.”
All that work has been matched with an extraordinary honor. The new study confirms that the dinosaur represents a newfound genus and species, and its formal name translates to “Mark Mitchell’s northern shield”—a nod to the fossil’s liberator, its impeccably preserved armor, and the location where it had been entombed.
“I was very excited [when I found out its name]," says Mitchell. "I put my hands up in the air and cheered."
A Means of Disguise
The study’s most provocative claim involves the nodosaur’s potential coloration, which the study authors say is preserved in a blackish coating that covers much of the dinosaur’s exterior.
Within these films—thought to be remnants of the dinosaur’s skin—study coauthor and University of Bristol paleobiologist Jakob Vinther says that he has found chemical hints of the red-brown pigment pheomelanin.
Importantly, Vinther and his colleagues didn’t find signs of the pigment everywhere on the animal. After sampling along cross-sections of the fossil, Vinther says that its underbelly appears to have lacked pheomelanin, which would have made that part of the animal lighter in color.
While some animals have dark backs and light bellies to help regulate body temperature, others have the patterning as a form of camouflage called countershading. This two-tone look flattens an animal’s appearance from afar and makes it harder for predators to spot.
In modern ecosystems, land mammals with body masses more than about a ton, such as rhinoceroses, don’t need this kind of visual defense strategy to keep predators at bay. By contrast, if the hefty and well-armored Borealopelta needed countershading, its predators must have been terrifyingly effective.
“The short story is, the Cretaceous is bloody scary,” says Vinther. “We have evidence for the fact that these theropods were eating Borealopelta [and other] large, heavily armored herbivores, taking them down and gulping them up.”
For some experts, though, the new study doesn’t present the necessary evidence for countershading.
“The specimen is certainly amazing. It’s an absolutely awesome paleontological discovery,” says Alison Moyer, a postdoctoral researcher at Drexel University who has studied fossilized soft tissues. But, she says, “the study relating to the pigmentation and coloration—and, therefore, conclusions about predator-prey relationships—is kind of flooded with issues.”
Vinther’s evidence, acquired in tests funded by the National Geographic Society, is indirect. Despite the nodosaur’s astounding preservation, he could find only traces of chemicals thought to be left behind when this particular pigment breaks down.
For Moyer, the study doesn’t fully address how the fossil’s chemistry may have changed over time, or whether the blackish film is really fossilized skin or the remains of a bacterial film that grew over the decaying dinosaur. She also notes that the preserved skin doesn't extend to Borealopelta’s underbelly, so she’s not convinced that this region lacked the pigmentation.
What’s more, multiple studies have documented the same breakdown product identified in the paper as a natural component of marine sediments, precisely where Borealopelta fossilized.
“There are endless possibilities that aren’t considered that would be more parsimonious than jumping to this countershading,” she says.
Paleontologist Mary Schweitzer of North Carolina State University, a leading expert on soft-tissue preservation in dinosaurs, agrees point for point with Moyer. “The data do not support their conclusions, in my opinion,” she wrote in an email.
Vinther counters that he didn’t find any of the compound in the sediments surrounding the fossil—only in Borealopelta’s putative skin, and at high concentrations.
Even so, says Lund University paleontologist Johan Lindgren, it’s possible that the compounds associated with pheomelanin actually come from other substances in or on the dinosaur that broke down during fossilization. “It highlights once again just how little we know about how soft tissues are preserved in animals,” he says.
The researchers studying Borealopelta emphasize that their study represents the first words on the dinosaur’s coloration, but certainly not the last.
Henderson adds that he looks forward to the years of healthy debate that the nodosaur is sure to provoke. The specimen is housed in a museum, where it will be available for other researchers to study using all sorts of techniques.
Borealopelta, he says, “is in a safe place for something truly exceptional—not hidden away in someone’s living room.”