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An armored dinosaur found in a Spanish open-pit coal mine suggests that North America and Europe were connected for millions of years longer than previously thought.

The 2-ton Europelta carbonensis (or "Europe's shield from the coal) lived between 113 and 110 million years ago, protected by tank-like armor and spines as it munched on short plants.

Until recently, it was thought that Europe and North America already had been separated by the Atlantic more than 120 million years ago. But the presence of nodosaurs on both sides of the pond means that unless they could build rafts, the ancestors of Europelta were either 1) in existence far earlier than fossil records show, or 2) more likely, walking between continents.

That's why when paleontologists in Arino, Spain, excavated the two skeletons in 2011, they called James Kirkland of the Geological Survey of Utah and Mark Loewen, research associate at the Natural History Museum of Utah, and asked them to co-author the study.

"It was quite the gift, there's no doubt about it," said Kirkland, who points out that Utah has an extraordinarily complete record of dinosaurs and the most complete polocanthid skeleton was found in the Beehive State. "That's my job, to basically make sure the world realizes Utah's the lynchpin for all this stuff."

Two hundred million years ago, Europe and North America were still attached. By the time nodosaurs' successors, polacanthids, went extinct about 120 million years ago, a sort-of greenhouse effect on steroids and drastically rising sea levels were flooding much of Europe and leaving many island chains.

During this time, extreme volcanism created almost five times the carbon dioxide that's in the atmosphere today, and the first flowering plants began to appear. Perhaps relatedly, so did the nodosaurids, evolving apart once water divided them.

"The diversification of nodosaurids separately on North American and Europe appears to correlate with rising sea levels flooding most of Europe to form an archipelago, isolating these dinosaurs even though the Atlantic Ocean had not fully opened yet," Kirkland said.

Europelta was about 15 feet long and 3 feet wide, prowling the swampy coast of the Tethys Sea (later the Mediterranean). Other nodosaurs — particularly toward the end of the Cretaceous — have been found in Europe previously, but the quality was "really scrappy," Kirkland said. "It amazes me that they haven't found anything better in 100 years."

The two skeletons of Europelta are well-preserved enough to say that, definitively, they're nodosaurs, and they're also the oldest nodosaur specimens found in Europe.

The study, for which Luis Alcala of Meseo Aragones de Paleontologia was also a co-author, was announced Monday in the journal PLOS ONE.

The region's coal results from the lush vegetation that was drowned by the period's rising seas, and it's emerging as a hotbed for dinosaur finds. Kirkland said he's thankful that the mining company was willing to invite them in and wishes Utah's miners would follow suit.

"Our coal companies look at us [paleontologists] as the enemy," he said. "I have no interest in shutting down a coal mine."

Twitter: @matthew_piper