Elpistostegalia

Elpistostegalia is a clade containing Panderichthys and all more derived tetrapodomorph taxa. The earliest elpistostegalians, combining fishlike and tetrapod-like characters, such as Tiktaalik, are sometimes called fishapods. Although historically Elpistostegalia (referred to as Panderichthyida) was considered an order of prehistoric lobe-finned fishes, it was cladistically redefined to include tetrapods.

==Paleobiology== A rise in global oxygen content allowed for the evolution of large, predatory fish that were able to exploit the shallow tidal areas and swamplands as top predators. Several groups evolved to fill these niches; the most successful were the elpistostegalians. In such environments, they would have been challenged periodically by low oxygen levels in the water. In comparable modern aquatic environments like shallow eutrophic lakes and swampland, modern lungfish and some genera of catfish also rely on the more stable, atmospheric source of oxygen.