Dipnoi, commonly known as lungfish, are a group of freshwater fish found primarily in Africa, South America, and Australia. They are unique among fish because they possess both gills and lungs, allowing them to breathe air when oxygen levels in the water are low. This adaptation enables them to survive in environments that may dry up seasonally. Lungfish are characterized by their elongated bodies and lobed fins, which resemble the limbs of tetrapods. They are considered important in the study of evolution, as they provide insights into the transition of life from water to land, linking them to early tetrapods and the evolution of amphibians.