Sapeornis chaoyangensis (Zhou and Zhang, 2002, abstract) is another of the many bird ancestors that have been found in China. Again from the early Cretaceous Liaoning area, Sapeornis stands out from the other discoveries in that it is the largest early cretaceous bird species yet found, being larger than Archaeopteryx and almost twice as large as Microraptor. The long arms suggest it had a large wing area, but the shoulder girdle does not seem to be adapted for flapping so Sapeornis was most likely a glider. Gastroliths – stones swallowed to help crush seeds and other plant material – indicate that this bird was a plant eater.
(Photo by Adrian Thysse, Hong Kong Science Museum)