It's not your father's tyrannosaur: Yutyrannus huali, a newly discovered ancestor of Tyrannosaurus rex, was covered from head to tail in downy feathers.

At 30 feet long and weighing 3,000 pounds, Y. huali wasn't so large as T. rex, which came 60 million years later, but it's the largest feathered tyrannosaur yet found. That such a big creature was feathered suggests its iconic descendant could have been similarly plumed.

The discovery provides "direct evidence for the presence of extensively feathered gigantic dinosaurs," wrote paleontologists led by Xing Xu of the Chinese Academy of Sciences in their description of the new dinosaur, published April 5 in Nature.

With a Latin and Mandarin name translating to "beautiful feathered tyrant," Yutyrannus huali was found in the Yixian Formation, a fossil deposit in northeastern China that over the last two decades has yielded dozens of dinosaur skeletons so finely preserved that it's possible to discern feather-like structures.

Those discoveries have fundamentally changed how dinosaurs appear in our imagination's eye. Contrary to traditional artistic interpretation, many – perhaps most – of the great reptiles were not covered in scales, but rather with feathers.

Whether T. rex was similarly quilled has remained a matter of speculation. While early feathered members of the tyrannosaur family have been found, they were very small. If the primary purpose of feathers was insulation, a possibility suggested by the feathers' down-like shape, then larger tyrannosaurs might not have needed them. Thanks to small surface-to-volume body ratios, large-bodied animals tend to maintain heat easily.

The significance of Y. huali is its body size and the apparent density of feather-like structures, said paleontologist Julia Clarke of the University of Texas at Austin. "We didn't know whether these larger-bodied forms would show as many."

Yutyrannus skull. Image: Zang Hailong

As for the possibility of a plumed T. rex, "We have as much evidence that T. rex was feathered, at least during some stage of its life, as we do that australopithecines like Lucy had hair," said Mark Norell of the American Museum of Natural History.

Norell and Clarke were not involved in the new study, but Norell helped discover the first feathered tyrannosaurs. He and Clarke recently described how a dinosaur called Microraptor likely used feathers not to fly, but as sexual displays to attract prospective mates.

Such findings raise a question: What were tyrannosaur feathers used for? Might the king of dinosaurs have strutted like a peacock?

It's possible, though hard to determine from the current evidence, said study co-author Corwin Sullivan, a paleontologist at the Chinese Academy of Sciences.

In addition to insulation, tyrannosaur feathering "might have also been involved in sexual selection if it were, for example, sufficiently brightly colored or strikingly patterned to attract potential mates," wrote Sullivan in an email. "At this point we don't have any data on the coloration of the plumage."

"It's an exciting time to be a dinosaur paleontologist," said Norell. The feather findings "have rocked the world in terms of how we think of" dinosaurs, he said. "Instead of giant lizards, they were basically weird birds."

Citation: "A gigantic feathered dinosaur from the Lower Cretaceous of China." Xing Xu, Kebai Wang, Ke Zhang, Qingyu Ma, Lida Xing, Corwin Sullivan, Dongyu Hu, Shuqing Cheng & Shuo Wang. Nature, Vol. 484 No. 7392, April 5, 2012.