Fossil analysis reveals colors of giant armored dinosaur
For the biggest animals, bulk is a great defense. Other creatures need tricks, like the snowy coat of an Arctic hare or a hagfish's choking slime clouds. But elephants and rhinoceroses get by with tough hides and sheer size. They have little to fear from predators and little need for camouflage — hence their dull gray skin.
A new fossil analysis reveals that things were different in the Cretaceous period, 110 million years ago. Even massive dinosaurs with thick skin and long spikes needed to avoid hungry eyes. Under pressure from ferocious predators, these herbivores evolved camouflage, according to a study published Thursday in the journal Current Biology. For the first time, paleontologists detected color in the fossil of a giant armored dinosaur called a nodosaur.
The nodosaur was the sort of creature that wouldn't bother with a disguise if it lived today. It had horns and scale plates for defense. And it was huge — 2,900 pounds or more when fullgrown, bigger than a black rhino. But size and armor were not enough.
The authors discovered chemical traces of pheomelanin, the same pigment that gives redheads their hair color, within the dinosaur's fossilized hide. The nodosaur was darker red and brown on top than on the bottom. This pattern, one seen today with deer and antelope, obscures a creature's silhouette.
"It gives you a sense of how nasty the theropod predators would have been back in the Cretaceous," said Caleb M. Brown, a paleontologist at the Royal Tyrrell Museum of Paleontology in Canada and an author of the new report.
That the scientists could find color at all, let alone a pattern, surprised other experts.
"I never seriously thought that color preservation on this scale would have been possible," said Thomas R. Holtz, a vertebrate paleontologist at the University of Maryland who was not involved with the study. "This skeleton is truly spectacular in terms of the quality of completeness."
The dinosaur died in 3-D, still covered with fossilized skin and with the remnants of its last meal in its stomach. "There's no other dinosaur specimen like it," Brown said. And, rather than the severe contortion of many dinosaur skeletons, this nodosaur looks almost peaceful — as though its last act was a nap on Medusa's porch.
Aman digging in Canadian oil sands in 2011 struck the fossil with his backhoe, as The Washington Post reported in May. A sea once covered that region in northeastern Alberta. People had discovered bones there before, mostly aquatic reptiles like plesiosaurs and ichthyosaurs, but the nodosaur was the first dinosaur discovered in the Alberta mine.