For first time, pa­le­on­tol­o­gists de­tect color in the fos­sil of a gi­ant di­nosaur

The Washington Post Sunday - - POLITICS & THE NATION - BY BEN GUAR­INO ben.guar­ino@wash­post.com

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 fos­sil still shows its skin and the rem­nants of its last meal in its stom­ach. “There’s no other di­nosaur spec­i­men like it,” Brown said. And rather than be­ing pre­served in the con­torted po­si­tion of many di­nosaur skele­tons, this no­dosaur looks al­most peace­ful — as though its last act was a nap on Me­dusa’s porch.

A man dig­ging in Cana­dian oil sands in 2011 struck the fos­sil with his back­hoe. A sea once cov­ered that re­gion in north­east­ern Al­berta. Peo­ple had dis­cov­ered bones there be­fore, mostly aquatic rep­tiles such as ple­siosaurs and ichthyosaurs, but the no­dosaur was the first di­nosaur dis­cov­ered in the Al­berta mine. Re­searchers hy­poth­e­size that the an­i­mal tum­bled into a river and died. Its body floated out to the sea, where it sank. There, lay­ers of sand kept scav­engers at bay as the car­cass set­tled into rock.

“It is an un­usual de­po­si­tional en­vi­ron­ment for a di­nosaur,” Holtz said. But it was a lucky one for pa­le­on­tol­o­gists. Sci­en­tists have found color traces in fos­sils be­fore, but most of those were small an­i­mals dug up from an­cient lakes.

Af­ter the miner found the no­dosaur, a fos­sil pre­parer named Mark Mitchell worked for more than five years to ex­pose the crea­ture within the rock. The an­i­mal’s sci­en­tific name, Bo­re­alopelta mark­mitchelli, hon­ors his 7,000 hours of la­bor.

When Brown and his col­leagues ex­am­ined the fos­silized skin, they found molec­u­lar sig­na­tures left by pheome­lanin pig­ment. What’s more, these analy­ses showed the red­dish-brown was more pro­nounced on top than on the bot­tom, a pat­tern known as counter-shad­ing.

“The fur­ther you went to­ward the belly, the less and less of this stuff there was,” Brown said. “It was darker pig­mented on top and lighter on the bot­tom.” The pat­tern ob­scures an an­i­mal’s out­line, bright­en­ing bel­lies in shadow and dark­en­ing where light falls from above. It’s a com­mon cam­ou­flage, found in chip­munks, gazelle and gi­raffes — but never be­fore in a land an­i­mal the size of a rhino.

Even though this was the first time this pat­tern had been found in a large di­nosaur, the dis­cov­ery was “in­cred­i­bly rea­son­able,” Holtz said.

“The largest liv­ing land preda­tors — big bears and tigers — are dwarfed by the gi­ant di­nosaur preda­tors,” he said. The 20-foot­tall Tyran­nosaurus rex, al­though it lived a bit later than this no­dosaur, could pul­ver­ize bones with a pow­er­ful chomp. “We have plenty of other ev­i­dence of big preda­tory di­nosaurs hav­ing at­tacked liv­ing plant-eaters,” with those other prey fos­sils show­ing par­tially healed bite marks.

This won’t be the last time we hear about this no­dosaur. Thanks to the de­tail of the fos­sil, “you can test some ideas and as­pects of their bi­ol­ogy that weren’t pos­si­ble be­fore,” Brown said. The pa­le­on­tol­o­gists plan to ex­am­ine the pre­served stom­ach con­tents to see what it ate be­fore it died. “There’s go­ing to be a lot more work on this par­tic­u­lar an­i­mal.”

ROYAL TYRRELL MU­SEUM OF PA­LE­ON­TOL­OGY/AGENCE FRANCE-PRESSE/GETTY IMAGES

An illustration of the no­dosaur with darker red-brown color on top. This pat­tern helps ob­scure a crea­ture’s sil­hou­ette from preda­tors.

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