朝阳市
The Jiufotang Formation (Chinese: 九佛堂组, pinyin: "jiǔfótáng zǔ") is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms (see Jehol Biota). It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with estimates ranging from the Late Jurassic to the Early Cretaceous. He et al. (2004) used argon - isotope radiometry to confirm biostratigraphic age estimates. They confirmed an Early Cretaceous, Aptian age for the Jiufotang Formation, 120.3 +/-0.7 million years ago. Fossils of "Microraptor" and "Jeholornis" are from the Jiufotang.