The Rise and Fall of the Dinosaurs: A New History of a Lost World: The Definitive Dinosaur Encyclopedia with Stunning Illustrations, Embark on a Prehistoric Quest!

by Steve Brusatte

These are feathers. Not the quill-pen feathers that make up the wings of today’s birds but simpler ones that look more like strands of hair. These were the ancestral structures that bird feathers evolved from, and it is now known that many (and perhaps all) dinosaurs had them. Yutyrannus and Dilong establish beyond a doubt that tyrannosaurs were among these feathered dinosaurs. Unlike birds, tyrannosaurs certainly were not flying. Instead, they probably used their feathers for display or to keep warm. And because both a large tyrannosaur like Yutyrannus and a small tyrannosaur like Dilong have feathers, this implies that the common ancestor of all tyrannosaurs had feathers, and therefore that the great T. rex itself was most likely feathered, too.