The so-called Jehol fossils, named after a mythical land of Chinese folklore, date to between 120 million and 130 million years ago and are noteworthy in a number of ways. Besides their remarkable preservation, which even saved traces of delicate structures like air bladders in fish, researchers have often found an unexpected juxtaposition of creatures in the same layer of ancient lake sediment. Small dinosaurs such as Psittacosaurus and birds such as Confuciusornis lie next to fish, for example.