Lungfish

Australian lungfish

lungfish, (subclass Dipnoi), any member of a group of six species of living air-breathing fishes and several extinct relatives belonging to the class Sarcopterygii and characterized by the possession of either one or two lungs. The Dipnoi first appeared in the Early Devonian Epoch (about 419.2 million to 393.3 million years ago), and the extant species occur in rivers and lakes in Africa, South America, and Australia. These animals are especially interesting because of their characteristic body forms, generally large size, disjunct distribution over Earth’s tropical regions, and peculiar mode of life.