Osteoglossiformes
Osteoglossiformes (Gk. "bony tongues") is a relatively primitive order of ray-finned fish that contains two sub-orders, the Osteoglossoidei and the Notopteroidei. All of the living species inhabit freshwater. They are found in South America, Africa, Australia and southern Asia, having first evolved in Gondwana before that continent broke up.The mooneyes (Hiodontidae) are often classified here, but may also be placed in a separate order Hiodontiformes.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). In other respects, osteoglossiform fishes vary considerably in size and form; the smallest is Pollimyrus castelnaui, at just 2 centimetres (0.79 in) long, while the largest, the arapaima (Arapaima gigas), reaches as much as 2.5 metres (8.2 ft).
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