A subclass or order of bony fishes that contains the lungfishes, which have lungs and breathe air. They are found in Africa, Australia, and South America, where they live in freshwater lakes and marshes that tend to become stagnant or even dry up in summer. They survive in these conditions by burrowing into the mud, leaving a small hole for breathing air, and entering a state of aestivation, in which they can remain for six months or more. The Dipnoi date from the Devonian era (416–360 million years ago) and share many features with the modern Amphibia.
Subjects: Earth Sciences and Geography — Biological Sciences.