text: Anchiornis fossils have been found in the Tiaojishan Formation of Liaoning , China , dating somewhat uncertainly to the mid-late Jurassic period ( Callovian or Oxfordian stage ) , 160 to 155 million years ago .
simplified: Anchiornis fossils have been found in Liaoning , China , dating to the mid-late Jurassic period , 160 to 155 million years ago .