Sinosauropteryx
Three specimens have been assigned to "Sinosauropteryx prima": the holotype GMV 2123 (and its counter slab [opposite face], NIGP 127586), NIGP 127587, and D 2141. Another specimen, IVPP V14202, was assigned to the genus but not to the only species by Zhang and colleagues. The assignment of an additional larger specimen to "S. prima", GMV 2124, was later found to be in error. All of the fossils were found in the Jianshangou or Dawangzhangzi Beds of the Yixian Formation in the Beipiao and Lingyuan regions of Liaoning, China. These fossil beds have been dated to 124.6–122 million years ago, during the early Aptian stage of the Early Cretaceous.
Liaoning
Liaoning contains some of the foremost paleontological sites in the world. Known collectively as the Jehol Group, they include the Yixian Formation, Jiufotang Formation and Tiaojishan Formation. The name "Jehol" derives from a now defunct provincial division of that name, which covered an area that is now Western Liaoning, Eastern Hebei, and a small part of Inner Mongolia. Fossils were first found there during the 1920s. During the Japanese occupation of the area through the 1930s and early 1940s, more fossils were found, but records of them were lost after World War II ended. The area remained relatively unexplored until the 1990s. It was in 1996 that Liaoning made the headlines with the announcement of the discovery of "Sinosauropteryx prima", the first example of a filamented "feathered" dinosaur. "Sinosauropteryx prima" was a small feathered meat-eating dinosaur, from the Lower Cretaceous Yixian Formation. This discovery pushed the evolution of feathers back in time and showed that dinosaurs, not only birds, had feathers. It also showed a direct evolutionary link between theropod dinosaurs and modern birds.