Book four in Robert Irwin's exciting book series. Discover a world of prehistoric adventure and dinosaurs. While spending time with the cassowaries at Australia Zoo, Robert mentions to Riley that many dinosaurs were also feathered. Riley thinks he's joking until the two friends zip back to prehistoric Asia, where feathered dinosaurs such as the oviraptor and Yutyrannus huali roamed the land. When they find an abandoned egg, the hunt is on to return it to its rightful owner. Featured Dinosaur: Yutyrannus This large bipedal predator grew to 9m long and 3m high and was covered in long feathers, which may have helped to keep it warm in an area with an average temperature of 10 degrees Celsius.