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Shaggy T. Rex Cousin Was Heftiest Feathered Dino

A 3,086-pound shaggy tyrannosaur was the world's largest known feathered animal -- living or extinct -- according to a paper in the latest issue of Nature.
/ Source: Discovery Channel

A 3,086-pound shaggy tyrannosaur was the world's largest known feathered animal -- living or extinct -- according to a paper in the latest issue of Nature.

The newly unearthed tyrannosaur, named Yutyrannus huali or "beautiful feathered tyrant," lived about 125 million years ago in northeastern China. The over 29-foot-long non-avian dinosaur, represented by three specimens, is considerably smaller than its infamous relative T. rex, but some 40 times the weight of the largest previously known feathered dinosaur, Beipiaosaurus.

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"The largest specimen preserves feathers on the tail, and two smaller specimens preserve feathers over the neck, on the forelimbs, near the pelvis, and even feet," lead author Xing Xu, a professor at Beijing's Institute of Vertebrate Paleontology and Paleoanthropology, told Discovery News.

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Xu and his colleagues analyzed the remains of the three dinosaurs and discovered that patches of filamentous structures were near the bones on the slabs containing the specimens. The researchers believe that when the dinosaurs were alive, these simple structures would have been more like the fuzzy down of a modern baby chick than the stiff plumes of an adult bird.

The feathers likely served two functions: insulation and decoration.

"The size, structure and extent of the feathers suggests that they would have formed a shaggy body covering that would have had at least some insulating function," co-author Corwin Sullivan told Discovery News. Sullivan is a Canadian paleontologist now based at the Beijing institute.

Large animals, like elephants, are usually not feathery or furry. That is because these beasts have a tendency to overheat. The new dinosaur, however, lived during the middle part of the Early Cretaceous, when temperatures are thought to have been relatively cool.

Previously it was thought that only certain smaller dinosaurs were feathered. The scientists still think that feathers first emerged in a smaller dinosaur, and that larger feathered dinos only came along later.

"However, that doesn't mean that small feathered dinosaurs disappeared," Sullivan said. "New small species continued to appear as well."

Some of these smaller species eventually evolved into today's modern birds.

A group of Yutyrannus and two individuals of the smaller Beipiaosaurus. Credit: Brian Choo

This meat-loving non-avian dinosaur, however, was no tiny songbird. Like T. rex, it appears to have been a fearless hunter.

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Xu thinks that the feathered dinosaur hunted in a pack.

"We have evidence that the three individuals we reported in the journal paper were hunting a large sauropod dinosaur when they died from unknown reasons," he said, adding that a volcano eruption could have done in the dinos.

Their feathers suggest that extensive, insulating plumage was more widespread than previously realized. The most primitive feathers did not have aerodynamic surfaces capable of generating lift for flying, but they could have functioned as decoration.

"Depending on their coloration and patterning, they might have been useful in display," Sullivan explained. "Note that this doesn't necessarily mean a performance, like a courtship dance."

He added, "If the feathers were strikingly patterned, for example, they could have simply been attractive to potential mates, and that could be considered a display function."

Prior research, along with this new study, suggest that non-avian dinosaurs were either scaled or feathered. No dino was furry, since fur evolved on the mammalian branch of the vertebrate evolutionary tree, whereas feathers evolved on the reptilian branch.