A new analysis of 240-million-year-old coelacanth fossils indicates these early fish possessed a remarkable, and unexpected, sensory adaptation: the ability to “hear” underwater using their lungs. The discovery provides fresh insight into how ancient vertebrates experienced their surroundings and sheds light on the evolutionary history of hearing itself.
The Bizarre Anatomy of Ancient Hearing
Coelacanths are a lineage of lobe-finned fish with a fossil record stretching back over 400 million years. They are essential to understanding vertebrate anatomy because they represent a transitional form between fish and early land animals. While thought extinct for decades, two living species of coelacanth (Latimeria ) were rediscovered in the 20th century, sparking renewed scientific interest.
The fossils examined – Graulia branchiodonta and Loreleia eucingulata from Triassic France – reveal an ossified (bony) lung containing wing-like structures. These plates enclosed a gas-filled cavity. Researchers discovered that this lung was connected to the inner ear via a canal, forming what appears to be a complete sensory system.
How It Worked: From Lung to Inner Ear
According to the study, sound waves entering the water would have vibrated the gas within the ossified lung. These vibrations would then travel through the canal directly to the inner ear, enabling the coelacanth to detect underwater sounds.
“Our hypothesis is based on analogies with modern freshwater fish such as carp or catfish,” explains Luigi Manuelli, a doctoral student involved in the research. These fish use a similar system called the Weberian apparatus, which connects the swim bladder to the inner ear, allowing them to perceive underwater vibrations. The air bubble in the swim bladder is critical for detecting these waves, which would otherwise pass through the fish’s body undetected.
The Loss of an Ancient Sense
Researchers speculate that this unique auditory ability was lost as coelacanth ancestors adapted to deeper marine environments. Their lungs regressed, making the system less necessary. However, remnants of the inner ear structures associated with this sensory adaptation remain, providing valuable clues to the fish’s evolutionary past.
“This anatomical remnant now provides valuable insight into the evolutionary history of these fish — and perhaps also into that of our own aquatic ancestors.” – Professor Lionel Cavin
This discovery challenges the traditional understanding of coelacanth sensory biology and suggests that early vertebrates may have utilized a wider range of sensory adaptations than previously thought. The findings, published in Communications Biology on February 14, 2026, underscore the importance of fossil research for unraveling the complex history of life on Earth.
