Avimimus ( meaning `` bird mimic '' ) was a recently-discovered maniraptoran . It was a very fast moving , light-weight , bird-like theropod dinosaur that lived in the late Cretaceous in what is now Mongolia , around 70 million years ago . Avimimus , meaning `` bird mimic '' ( Latin avis = bird + mimus = mimic ) , was a genus of bird-like maniraptoran dinosaur that lived in the late Cretaceous in what is now Mongolia , around 70 million years ago .