Notopteridae (featherfin knives)
Osteoglossiformes (Lat. "bony tongues") is a relatively primitive order of ray-finned fish that contains two sub-orders the Osteoglossoidei and the Notopteroidei
Members of the order are notable for having toothed or bony tongues, and for having the forward part of the gastrointestinal tract pass to the left of the oesophagus and stomach (for all other fish it passes to the right).
One species, the arapaima (Arapaima gigas) is the largest freshwater fish known, with specimens reported up to 4.5 m in length.
The mooneyes (Hiodontidae) are often classified here, but may also be placed in a separate order Hiodontiformes.