Meet Borealopelta markmitchelli, ‘Best-Preserved Armored Dinosaur’

An analysis of the fossilized skin of Borealopelta markmitchelli, the most well-preserved of the armored dinosaurs ever unearthed, has revealed that the ancient creature had a reddish-brown coloration and camouflage in the form of countershading, and that despite being the size of a tank, it was still hunted by carnivorous dinosaurs. The results appear today in the journal Current Biology.

A reconstruction of Borealopelta markmitchelli. Image credit: Royal Tyrrell Museum.

Borealopelta markmitchelli is a species of nodosaur, a type of ankylosaur. It roamed the Earth during the Cretaceous period, about 110 million years ago.

Its spectacularly detailed ‘mummy’ was found by accident in March 2011 by excavator operator Shawn Funk at the Suncor Millennium Mine in Alberta, Canada.

The Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta, was notified and sent a group of paleontologists to take a look. The researchers soon realized that the rocks contained an armored dinosaur.

“Finding the remains of an armored dinosaur that was washed far out to sea was huge surprise. The fact that it was so well preserved was an even bigger surprise,” said Dr. Donald Henderson, Curator of Dinosaurs at the Royal Tyrrell Museum.

Borealopelta markmitchelli. Image credit: Royal Tyrrell Museum.

“This nodosaur is truly remarkable in that it is completely covered in preserved scaly skin, yet is also preserved in 3D, retaining the original shape of the animal,” said Dr. Caleb Brown, a paleontologist at the Royal Tyrell Museum.

The specimen is about 5.5 m (18 feet) long and weighs 1,134 kg (2,500 lb), not far off its 1,360-kg (3,000 lb) fighting weight estimated by the researchers.

They think Borealopelta markmitchelli may have been swept away by a flooded river and carried out to sea, where it eventually sank. Over millions of years on the ocean floor, minerals took the place of its armor and skin.

Borealopelta markmitchelli. Image credit: Royal Tyrrell Museum.

“The result is that the animal looks almost the same today as it did back in the Early Cretaceous,” the scientists said.

“The specimen now represents the best-preserved armored dinosaur ever found, and one of the best dinosaur specimens in the world.”

The fossil was analyzed by a team of experts from MIT, Newcastle University, the University of Bristol, and the Royal Tyrrell Museum.

To infer the dinosaur’s pigmentation pattern, the paleontologists analyzed organic compounds in its horns and skin impressions.

They found that the skin of Borealopelta markmitchelli exhibited countershading, a common form of camouflage in which an animal’s underside is lighter than its back.

This suggests that the nodosaur faced predation stress from meat-eating dinosaurs.

The skin and osteoderms from Borealopelta markmitchelli. The dark skin impressions are remains of reddish brown melanin. Image credit: Royal Tyrrell Museum.

“We found a lot of sulfur-bearing organic compounds, which we later could confirm was evidence for reddish brown coloration,” said team member Dr. Jakob Vinther, from the University of Bristol.

“Although countershading is common, the findings come as surprise because Borealopelta markmitchelli’s size far exceeds that of counter shaded animals alive today.”

“It suggests the dinosaur was under enough pressure from predators to select for concealment.”

A reconstruction of Borealopelta markmitchelli indicating the stressful life it must have lived with the constant chance of being eaten. Image credit: Robert Nicholls.

“The Cretaceous period was a really scary time to be around in,” he added.

“Large theropod dinosaurs with excellent color vision would have made life stressful for many dinosaurs, both big and small.”

The team is now examining Borealopelta markmitchelli’s preserved gut contents to find out the nature of its last meal, and working to characterize the body armor in even greater detail.

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Caleb M. Brown et al. An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics. Current Biology, published online August 3, 2017; doi: 10.1016/j.cub.2017.06.071