A four-winged dinosaur stalked ancient birds in China

For years, the Changma Basin in northwest China presented a grisly puzzle to paleontologists. The site is a graveyard of the Early Cretaceous, containing more than 100 partial skeletons of ancient birds. Many of these fossils were found in fragmented clusters that looked suspiciously like pellets, the undigested balls of bone and fur that modern owls and hawks cough up after a meal. While the victims were everywhere, the predator responsible for eating them remained a ghost in the fossil record.