A giant feathered tyrannosaur has been unearthed in China, the largest creature — living or extinct — known to sport a downy coat.
The carnivore, which grew up to nine metres long, likely looked "downright shaggy," says Corwin Sullivan, a Canadian paleontologist on the team that unveiled the creature Wednesday.
Three specimens of the dinosaur, which the scientists have called Yutyrannus huali for "beautiful feathered tyrant," have been uncovered in northeastern China.
One was an adult estimated to have weighed 1.414 tonnes, 40 times bigger than any previously found feathered dinosaur. And two juveniles tipped the scales at about half a tonne.
The ancient bones were found by fossil traders and brought to museums where paleontologists realized their significance, which is detailed in the journal Nature this week.
The discovery "provides solid evidence for the existence of gigantic feathered dinosaurs," reports the team led by Xu Xing, at Beijing's Institute of Vertebrate Paleontology and Paleoanthropology.
The scientists say the creature did not actually fly which would have been impossible given its large size — far bigger than the average cow — and the downy structure of its feathers. But they say the feathers may have had an important function as insulation because the creatures lived about 125 million years ago when global temperatures took a dip.
"The average temperature would have been about 10 degrees C," says Sullivan, an associate professor at the Beijing paleontology institute.
"That is perhaps not too different from northern China today," he says, but was an "unusually cool" period in the age of the dinosaurs.
Tyrannosaurus rex, which was larger and roamed a much warmer world, is not believed to have had any feathers though the researchers don't rule it out.
"It's possible that some dinosaurs that were even bigger had feathers but we can't tell one way or the other because most dinosaurs are known only from bones," Sullivan said in an interview from Beijing.
While the feather preservation on the three specimens "is patchy," the team says the creatures had plenty of long, filamentous feathered plumage.
"They would have looked superficially more like hair than the feathers of modern birds," says Sullivan, who describes the downy creature as quite a carnivore.
"I wouldn't want to meet one in a dark alley," he says.
He says the specimens were collected by fossil traders and then brought to museums, a practice not uncommon in China.
But the trade is not without problems. "Some dealers will yield to the temptation to improve their specimens," says Sullivan, explaining how they have been known to combine parts from different specimens and species.
But with experience and knowledge of both the fossils beds and the traders "who you are dealing with it is possible to largely avoid those problems," he says. "So we are quite sure these specimens are authentic."
Sullivan, who was raised in Ontario and British Columbia, did graduate studies at the University of Toronto and Harvard University before heading to China four years ago where he has been involved in several significant fossils finds.
"China is just so rich in important dinosaurs and other vertebrate fossils that there are a lot of opportunities here," he said when asked if he plans to return to Canada. "So I am not ready to come home just yet, but I think I would like to eventually."