Chinese Academy of Sciences/Dr Brian Choo

The discovery of a giant dinosaur with a shaggy coat of chick-like feathers has proven to palaeontologists that fuzzy down was not exclusive to the smaller dinosaurs.

Palaeontologists have known for more than a decade that some dinosaurs sported feathers, mainly thanks to near-perfectly preserved fossils from northeastern China. Species like Protarchaeopteryx and Beipiaosaurus had primitive feathers, used for insulation rather than flight.

But those have always been smaller, bird-like dinosaurs. The new species, found in a Cretaceous-era quarry in Liaoning Province, is estimated to be 40 times the weight of the largest previously known feathered dinosaur.

Yutyrannus huali, which means "beautiful feathered tyrant" in a combination of Latin and Mandarin, would have been about nine metres long and weighed about 1,400 kg. Its feathers were simple filaments, "more like the fuzzy down of a modern baby chick than the stiff plumes of an adult bird," says lead author, Xu Xing.

Yutyrannus is a close relative of the infamous Tyrannosaurus rex. So could T. rex also have been a feathery tyrant, prowling the land with a shaggy coat of down?

Yutyrannus lived during the middle part of the Early Cretaceous, when temperatures are thought to have been somewhat cooler. T. rex, however, lived in the warmer conditions of the Late Cretaceous. Plus, large-bodied animals (the tyrant lizard was a whopping 12 metres long, and weighed 6,800kg) retain heat easily, and feathers could lead to overheating.

Also, isolated patches of preserved skin from the dinosaur's closest relatives show scales, not feathers. So, it's not likely that Jurassic Park will need to be remade with a fuzzy Rex any time soon, but the possibility that the meat-eater was partly feathered cannot be completely ruled out.

"Yutyrannus dramatically increases the size range of dinosaurs for which we have definite evidence of feathers," Xu says. "It's possible that feathers were much more widespread, at least among the meat-eating dinosaurs, than most scientists would have guessed even a few years ago."


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