ABSTRACT
The transition from fish to limbed vertebrates (tetrapods) coincided with a radical restructuring of parts of the braincase, while at the same time other parts remained essentially conservative. The braincases of the tetrapod-like fishes Panderichthys and Eusthenopteron are structurally very similar, while that of the stem tetrapod Acanthostega was characteristically tetrapod-like in construction of the otic region and hyomandibula. In contrast to this, the occipital region is conservative and Eusthenopteron-like in Acanthostega, with no occipital condyle. Eusthenopteron, Panderichthys, Acanthostega and the stem tetrapod Greererpeton are successively more crownward plesions used to represent the fish-tetrapod transition.
