Note: This image is outdated. The first tetrapods were solely aquatic.
Chasing smaller fishes.
Comparison between fins of Tiktaalik, Panderichthys and Eusthenopteron, compared to the legs of 2 tetrapods ( Acanthostega and Ichthyostega ).
Comparison betwwen fins and legs of several Sarcopterygii'n fishes and some tetrapods.