The overlooked 'nose' of an African fish has forced scientists to look at the fossil record with new eyes.

Often regarded as a living fossil, the polypterus fish has provided researchers with evidence that four-legged land animals first developed the ability to breathe air as ancient fish in water.

Flinders University paleontologist John Long. Credit:AFP

Outlined in the journal Nature Communications on Thursday, the discovery is significant as it not only sheds light on the evolution of breathing air in the first amphibians but also the origin of hearing – all the way up the evolutionary tree to humans.

Being water-based creatures, the 'noses' of polypterus fish are located on the top of their heads. Physiologists based at the US Scripps Research Institute spent more than 360 hours observing how the primitive freshwater fish breathe. They found the north African fish, which has four limbs but no digits, was the only fish to still breathe through two valved channels on the top of the head.