Prehistoric fish used lungs to hear underwater, fossils reveal

A prehistoric fish used its lungs to hear underwater, according to a new study. Researchers uncovered this unusual ability by examining 240-million-year-old fossils. The findings reveal how ancient coelacanths relied on a unique sensory system to detect sound.

The study, led by Lionel Cavin of the University of Geneva, focused on two coelacanth species from the Triassic period. Fossil analysis showed that sound waves entered the fish's lung organ before travelling through a specialised passage to the inner ear. This adaptation allowed the creature to hear in its underwater environment.

Today's descendants of these fish live in the deep sea and breathe only through gills. Unlike their ancestors, modern species have developed other survival traits. These include bioluminescence for navigation, pressure-resistant bodies, and the ability to withstand freezing temperatures and high salinity. Some related deep-sea organisms, like amphipods, can endure pressures exceeding 1,100 atmospheres. The research was published in the journal *Communications Biology*.

The discovery highlights an early evolutionary adaptation in coelacanths. While their modern relatives have lost this lung-based hearing system, they have gained other specialised features. These changes reflect millions of years of evolution in extreme deep-sea conditions.