Of all dinosaurs, the lightly built and big-brained dromaeosaurs or 'raptors' such as Sinornithosaurus and Velociraptor are the closest relatives of birds.

Sinornithosaurus had a broad range of feathers including downy, insulating fluff over most of its body and longer display feathers on its arms, tail and head. Some of its long feathers had barbules and hooklets that bound together a feather's barbs and gave the feather greater strength, flexibility and surface area. It is possible that such feathers helped dinosaurs like Sinornithosaurus and Velociraptor to balance, or may even have boosted them when leaping into the air after prey. At least two specimens of Sinornithosaurus have been found at Liaoning.

Velociraptor mongoliensis
Artist: James Reece