The unusual preservation and evolutionary significance of the avian and non-avian dinosaur fossils from western Liaoning Province in China exemplifies rare conservation deposits. Described as the Jehol Biota, the fauna includes such remarkable discoveries such as feathers and wings associated with dinosaurs as well as many new species of fossil birds preserved in abundance. Volcanic activity during the Mesozoic was crucial to the preservation of the Early Cretaceous Jehol Biota by acting as a mechanism that killed organisms en masse from volatile emissions and voluminous ash falls. One of the crucial specimens documented in the Liaoning deposits is Microraptor gui, a four-winged glider. Described as a feathered, non-avian dinosaur, the evolution of such an animal in a group closely related to birds necessitates revision of the origin of flight paradigm.