Phylogeny of gnathostomous Vertebrata

Significant evolutionary events include (1) development of hinged, opposable jaw elements in Ganthostomata,  (2) development of a teleostomic jaw in the Osteichthyes, and (3) modification of the primitive lung as a swim bladder in ray-finned fish (Actionopterygii), (4) modification of flehsy pentadactyl appendages in the lobe-fin fishes as limbs in Tetrapoda, (including modern Lissamphibia) and (5) development of an amniotic membrane in the eggs of Amniota.