A superorder of freshwater bony fishes of the subclass shovelnose. Known since the Middle Devonian, flourished until the Triassic. 

Length 30-200 cm, body laterally compressed or eel-shaped. The upper jaw is fused with the skull, the teeth are usually massive plates, the chorda is preserved throughout life, unpaired fins have a peculiar pinnate structure. 

The pectoral and pelvic fins are flagellated or have a segmental axis with rays separated on two sides. In addition to gill breathing, there is pulmonary breathing (hence the name). 

The function of the lungs is performed by a large cellular swim bladder; in pulmonary respiration, air passes to it through specialised channels - the internal nostrils or choans. 

Heart with an arterial cone, the atrium partially divided into right and left parts. 

The spiral valve of the intestine opens into the cloaca. 

2 modern order. The order Ceratodontiformes contains 1 family, Ceratodontidae, with 1 genus and 1 species of Neoceratodus forsteri. The order Lepidosireniformes is represented by 2 families: Lepidosirenidae with a single species - Lepidosiren paradoxa, and Protopteridae with a genus - Protopteridae (4 species). 

They are found in the waters of South America, tropical Africa and Australia.

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Tags: dipnoi