Lepidosirenidae

Lepidosirenidae is a monotypic family of lungfish, containing only the genus Lepidosiren and the single species Lepidosiren paradoxa, the South American lungfish. This fish is one of the four extant species of lungfish, a group of freshwater fish characterized by the presence of both lungs and gills, allowing them to survive in oxygen-poor water or during drought by breathing atmospheric air.

Lepidosiren paradoxa is found in the Amazon and Paraguay river basins of South America. It is a long, eel-like fish that can grow up to 1.5 meters in length. Its body is covered in small scales, and it has two pectoral fins and two pelvic fins that are elongated and filamentous, resembling legs. These fins are used for locomotion on the substrate. The coloration of the South American lungfish is typically dark brown to black, often with lighter speckles.

During the dry season, when water levels recede and oxygen becomes scarce, Lepidosiren paradoxa can aestivate. It burrows into the mud at the bottom of the water body, forming a mucus cocoon to prevent desiccation. In this state, it relies solely on its lungs for respiration, entering a period of dormancy until the return of the wet season. The diet of the South American lungfish consists mainly of crustaceans, mollusks, and small fish, which it captures using its sharp teeth. Its classification within the Sarcopterygii, or lobe-finned fishes, places it in a lineage that is evolutionarily significant as it shares ancestry with the tetrapods.