The Jehol Biota

The Jehol Biota is a collection of fossils from the Yixian and Jiufotang Formations of Liaoning, Hebei and Inner Mongolia in northeastern China, about 133 to 120 million years old. Volcanoes repeatedly buried lakes and forests in ash, and fine mud preserved skin, feathers, hair, stomach contents and even colors. The best-known beds lie around Beipiao in Liaoning. Few places in the world show a Cretaceous community so fully.¹²

The finds are astonishing. Feathered dinosaurs include Sinosauropteryx, Microraptor and Yutyrannus. Early birds include Confuciusornis, a beaked bird found in 1995, and many more with teeth. Archaefructus, a water plant described in 1998 by Sun Ge and colleagues, is one of the oldest known flowering plants, and Eomaia, from 2002, is an early relative of placental mammals. The mammal Repenomamus, about a meter long, was found with a baby Psittacosaurus in its stomach, showing that some Mesozoic mammals ate young dinosaurs.¹³⁴

Jehol sits at a key moment, after birds had diverged from other dinosaurs and as flowers and flowering-plant insects were spreading. Its rocks span cool and warm shifts, and show how one ecosystem changed through about 13 million years. Chinese paleontologists, including Zhou Zhonghe, Xu Xing and Wang Yuanqing, have worked these beds for decades, and they transformed the view of dinosaur-bird evolution. The same fossil boom produced the 1999 Archaeoraptor forgery, glued together from two different animals, a warning about fossils bought on the market.¹²