"Acanthostega" is part of widespread evolutionary adaptive radiation in the late Devonian period. It started with purely aquatic finned tetrapodomorphs. Their successors did more air-breathing, had adaptions to the jaws and gills. They had a more muscular neck allowing freer movement of the head than fish have, and used their fins to raise the body of the fish. These features are seeen in the earlier "Tiktaalik", which like the "Ichthyostega" and "Acanthostega" is thought to have been primarily aquatic. 