Which group of fish is the most ancient? What structural features confirm this?

The most ancient group of fish is considered to be the cisperoids, the most ancient of which is the coelacanth or coelacanth. It is believed that all existing species of amphibians originated from them, which is confirmed by the similarity of the structure of some of the elements of the fins with the five-toed limbs of vertebrate terrestrial amphibians and their location, the presence of pulmonary respiration. There are also many fossils that confirm that cross-finned fish lived millions of years ago.