Aurornis is an extinct genus of avialan theropod dinosaurs and, perhaps, one of the very first. It contains a single species, Aurornis xui, described based on a fossil found in the Tiaojishan Formation of Liaoning, China, in rocks dated to the late Jurassic period (Oxfordian stage), about 160 million years ago. Scientists in magazine, say a feathered, chicken-sized creature known as Aurornis xui, unearthed recently in northeastern China, challenges the pivotal position of Archaeopteryx — long regarded as the oldest bird.