The northeastern Chinese Yanliao Biota (sometimes called the Daohugou Biota) comprises numerous, frequently spectacular fossils of non-marine organisms, occurring in Middle-Upper Jurassic strata in western Liaoning, northern Hebei, and southeastern Inner Mongolia. The biota lasted for about 10 million years, divided into two phases: the Bathonian-Callovian Daohugou phase (about 168-164 million years ago) and the Oxfordian Linglongta phase (164-159 million years ago). The Yanliao fossils are often taphonomically exceptional (many vertebrate skeletons, for example, are complete and accompanied by preserved integumentary features), and not only are taxonomically diverse but also include the oldest known representatives of many groups of plants, invertebrates, and vertebrates. These fossils have provided significant new information regarding the origins and early evolution of such clades as fleas, birds, and mammals, in addition to the evolution of some major biological structures such as feathers, and have demonstrated the existence of a complex terrestrial ecosystem in northeast China around the time of the Middle-Late Jurassic boundary.