YUTYRANNUS

Palaeontologists have known for decades that some dinosaurs were "feathered". But they've mostly belonged to a group of theropods called Maniraptora, which includes therizinosaurs, oviraptorosaurs, alvarezsaurids and deinonychosaurs. And they've all been fairly small, with Beipiaosaurus being the largest at a little over two meters long. However, that all changed at Easter time 2012 with the discovery of Yutyrannus—the feathered tyrant—funnily enough, in the same area as Beipiaosaurus, which dramatically increased the size range of dinosaurs for which we have definite evidence of feathers.

Not only is Yutyrannus a tyrannosauroid and a primitive, three-fingered pre-cursor to the colossal two-fingered tyrant lizards that bossed the latest Late Cretaceous and were scaley, but it's also nine meters long and a good ton and a half in weight. Its feathers are nothing like the feathers of modern flying birds, though. They were simple filaments that gave a coating more like the fuzzy down of a baby chick than the stiff plumes of an adult bird and were probably there for insulation during a much-cooler-than-previously-thought Middle Cretaceous period.