Imagine a tyrannosaur weighing one and a half tons, completely covered in soft, downy plumage. Even its tail is fluffy with feathers. Though we've known for a while that many dinosaurs were covered in feathers, a group of Chinese researchers have now provided direct evidence that gigantic, deadly tyrannosaurs might have looked a bit like wuffly birds. Three nearly complete, well-preserved fossils give us a glimpse of tyrannosaurs the way we've never seen them before.
The fossils were found in the Liaoning Province in China, in the "Yixian formation," a package of rocks that is known to date to the early Cretaceous period. Described today in Nature magazine, the creatures are in the subgroup Tyrannosauroidea, which is part of the Therapod family that includes both the iconic T. Rex as well as winged dinosaurs who eventually evolved into today's birds. The animals that paleontologist Xing Xu and colleagues dubbed Yutyrannus huali would have been quite large for tyrannosaurs (the largest, an adult, likely weighed almost 1.5 tons) and were probably the apex predators of their region.
The researchers write:
Most significantly, Y. huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.
In these fossils, you can see the long, downy tail feathers that would have trailed out behind these huge beasts. Their quills make a distinctive pattern of lines around the tailbone.
And here's one of the tyrannosaur skulls, also with distinctive impressions of feather quills on the crest of its head. The question that Xu and his team ask is why these large dinosaurs would have needed feathers. Usually feathers and fur are used for insulation, but creatures with large bodies often lose their hair because they generate enough body heat that insulation is unnecessary. Y. huali is by far the largest dinosaur known to have had feathers, and there is plenty of fossil evidence that other large tyrannosaurs had scaly skin.
The researchers speculate that these tyrannosaurs may have been adapted to extremely cold environments, while other tyrannosaurs lived in more tropical regions. Another possibility is that Y. huali didn't have feathers all over its body — it might have had some areas of bright plumage for display, but scales elsewhere.
Read the whole scientific article in Nature