Jehol Biota
The fossils have been found in several sites of exceptional preservation. The two most famous are the Yixian and Jiufotang Formations. The Yixian and Jiufotang Formations are Lagerstatten, meaning that they have exceptionally good conditions for fossil preservation. The fossils are numerous, but also very well preserved. They often have articulated skeletons (bones connected), soft tissues, colour patterns, stomach contents, and twigs with leaves and flowers still attached.