Fishes are at the base of the vertebrate Tree of Life and fishes do not have four limbs! However, earlier tetrapods are sister groups of fishes. What fish species are sister to or considered an earlier tetrapod? Solution The evolution of Tetrapods occur 0.4 billion years ago. It occur in Devonian period. The ancestors for tetrapods are Lobe-finned fishes or Sarcoptyrigaens. The living sarcoptygians are Coelacanths and lung fishes.