Australian Lungfish

Neoceratodus forsteri freshwater fish underwater Mary River Queensland 
 
Australian lungfish represent an ancient lineage dating back to the Devonian epoch around 380 million years ago. These ancient creatures are possibly the closest living thing to the fish that crawled out of the sea to become amphibians, reptiles, and eventually mammals. World-wide there are six species of lungfish today, even within this group the Australian species is unique, being the sole member of its family. A key distinction is that the Australian species possesses only a single lung (as well as gills), whereas all other lungfish possess paired lungs.