Sinornithosaurus (derived from Latin and Greek, meaning 'Chinese bird-lizard') was a feathered dinosaur from the Lower Cretaceous, a dromaeosaur. It was found in the Yixian Formation in what is now China.
This new fossil supports the idea that these dinosaurs did not have scaly, reptile-like skin, but had a softer, downy coat. No fossil skin impressions of these dinosaurs had been found previously.