# Osteichthyes - Member of the [[Gnathostomata]] in the [[Vertebrata]] - True bone - Had swim bladders - [[fresh-water|Fresh water]] has a lower buoyant density than [[sea-water|sea water]] - Needed some way to offset the weight of the bone structures ## Taxonomy - [[Osteichthyes]] - [[Actinopterygii]] - [[Sarcopterygii]] - [[Tetrapodomorpha]]