Fossilized bones found in Alaska are those of a new species of dinosaur previously unknown to science, say researchers of the find in 69-million-year-old rocks.
The species, Ugrunaaluk kuukpikensis, was a type of hadrosaur, a group of duck-billed plant-eating dinosaurs that generally lived in herds, they say.
Northern Alaska, where the fossils were found, was once much warmer than it is today and covered with forests, paleontologists explain, but despite the warmer climate, the creatures would have still spent months in Arctic darkness and probably would have seen snow.
The species, so abundant the researchers have uncovered 10,000 bones of the animals, had, for decades, been confused with another species, Edmontosaurus, fossils of which are common in both the U.S. and Canada.
However, a formal study of the fossils uncovered differences in skull features and mouth configuration that proved it was a separate species, explains Pat Druckenmiller, earth sciences curator at the University of Alaska Museum in Fairbanks.
Those differences had been hard to spot initially because almost all of the fossils unearthed were of juveniles, difficult to tell from Edmontosaurus fossils.
The thousands of bones recovered from the Prince Creek Formation more than 300 miles northwest of Fairbanks were from juvenile specimens less than nine feet long. Adults of the species were probably close to 25 feet long, the researchers say.
"It appears that a herd of young animals was killed suddenly, wiping out mostly one similar-aged population to create this deposit," Druckenmiller said of the fossil find.
Although debate about dinosaur metabolism — were they cold-blooded or warm-blooded? — has been intense, most people think of dinosaurs as essentially tropical creatures, living in warmer climates.
"It wasn't so long ago that the idea of dinosaurs living up in the polar world was kind of, you know, really? Are you kidding?" Druckenmiller says.
The name Ugrunaaluk kuukpikensis means "ancient grazer," and scientists chose it with help from speakers of Inupiaq, the language of Alaska Inupiat Eskimos.
Sixty-nine million years ago, the average temperature in the north of what is now Alaska would have hovered around the low 40s, the researchers point out.
"By reptilian standards, that's pretty chilly," Druckenmiller says, suggesting the species must have evolved special adaptations to deal with the cold.
"These were dinosaurs living at the very edge of what we think dinosaurs were physiologically capable of," he says.
In addition to the chilly temperatures, the region would have been in total darkness for three to five months of the year, researchers point out, making the new species even more interesting.
"It's intriguing for us to ponder how they survived those months of darkness," says Greg Erickson of Florida State University. "We're just finding this whole new world of dinosaurs we didn't know existed."
