Tianyulong

Tianyulong is a heterodontosaurid dinosaur of Jurassic China. It is notable to be the first ornithischian found with feathers, further strengthening the relationship between dinosaurs and birds.

Its fossils were found in the Tiaojishan Formation, which dates to approximately 158.5 million years ago. When Tianyulong was first described, however, it was originally thought to have come from the Jehol Biota, an area of time in the Early Cretaceous that yielded many examples of feathered dinosaurs.

Description
Because Tianyulong is a primitive ornithischian, the presence of feathers (or feather-like structures) indicates that the feature first developed in dinosaurian ancestors. This further raises the possibility that most groups of dinosaurs did indeed have feathers.