A notable member is the arapaima (Arapaima gigas), the largest freshwater fish in South America and one of the largest bony fishes alive.

Other notable members include the bizarre freshwater elephantfishes of family Mormyridae.

Only the somewhat diverse "bone-tongues" (Osteoglossiformes) and two species of mooneyes (Hiodontiformes) remain.

[1][2][3] The ichthyodectiform fishes from the Jurassic and Cretaceous periods were once classified as osteoglossomorphs, but are now generally recognized as stem teleosts.

Phylogeny based on the following works:[5][6][7] Hiodontidae Pantodontidae Osteoglossidae Notopteridae Gymnarchidae Mormyridae