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How an eerily preserved fossil changed everything we used to think about dinosaur body armor

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Aug 4, 2017

For anyone who grew up ogling an articulated T-rex or triceratops skeleton that was forever frozen into its final stomp or roar in a museum, your mind will now be blown by this mummified dinosaur—and what it has to tell us about its body armor.

Sometime around 110 million years ago, a 20-foot reptile thought to be a type of nodosaur gasped its dying breath on a beach in what is now Alberta. The waves took its corpse out to sea, where it would sink into layers of mineral-rich mud on the ocean floor and become petrified (some say mummified) into what is arguably the most impeccably preserved fossil ever.

Borealopelta markmitchelli was first discovered in May, when it was accidentally unearthed by a mining operator. To see its ghostly remains is like looking through a portal back in time, especially for the scientists who recently completed an extensive analysis of the specimen. Most movie dinosaurs that roam thrillers like Jurassic Park seem to come in an array of browns and greens that hatched from the imaginations of special effects designers, but this one’s pigmentation pattern was inferred by chemically analyzing the organic residues that still remained in its scales because the original skin never decomposed.

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What mummified dinosaur B. markmitchelli was thought to look like in the flesh. 

Led by Royal Tyrrell Museum paleontologist Caleb Brown, the research team, whose study was just published in Current Biology, unearthed something unexpected about this holotype. Its alternate form of defense, besides built-in armor that shielded a 2,800-pound frame, was a form of camo. A creature wearing this kind of camouflage, called countershading, is darker on its back than its underside for an effect known as self-shadow concealment.

“Imagine the 3D form of an animal in sunlight from above, the back of the animal will be well lit, while the belly will be in shadow,” Brown said. “With countershading, the pigment of the skin is opposite to this pattern of light, such that the two will cancel out, and the 3D form of the animal will be less obvious.”

While this kind of insta-camo is just as useful at hiding predators as they creep up on prey as it is hiding the prey they hunt, B. markmitchelli was an herbivore. Meaning, even a giant lizard with its own suit of armor needed to make itself invisible to things with dagger teeth.

So what would risk cracking its jaw to eat this thing? Probably monster carnivores like Carchadontosaurus (translation: “shark-toothed lizard”), a beast that dwarfed even the T. rex. Prey species like rhinos and elephants evolved out of countershading once their size made predators pretty much a nonissue. This had scientists convinced that larger dinosaurs—especially those covered in bony plate armor—had no need to hide from anything. At least until B. markmitchelli surfaced.

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So well-preserved it's spooky.

Now everyone go to Canada and start digging for dinosaur mummies.

(via Gizmodo)