An analysis of two 240-million-year-old coelacanth fossils suggests a bizarre sensory adaptation: an ossified lung that transmitted sound to the inner ear, offering new clues to how early vertebrates perceived their environment.
Reconstruction of a Triassic coelacanth schematically showing the otophysic connection linking the ossified lung to the inner ear and enabling underwater hearing. Image credit: A. Beneteau & L. Cavin, MHNG.
“Coelacanths are lobe-finned fishes with a fossil record spanning over 400 million years, representing a key lineage for understanding the evolution of vertebrate anatomy,” said Professor Lionel Cavin, a paleontologist with the Natural History Museum of Geneva and the University of Geneva, and colleagues.
“Once thought extinct, they survive today as the genus Latimeria, with two recognized species.”
“Fossil coelacanths exhibit within the body cavity a series of enigmatic large ossified plates arranged in a tile-like pattern, enclosing an internal cavity inferred to have been gas-filled in life.”
In new research, the paleontologists examined lung and inner ear anatomy of Graulia branchiodonta and Loreleia eucingulata, two species coelacanths from the Middle Triassic of eastern France.
Using a particle accelerator at the European Synchrotron Radiation Facility, they revealed an exceptionally well-preserved ossified lung, featuring wing-like bony structures at its extremity.
At the same time, the study of embryos of modern coelacanths highlighted a canal connecting the organs of hearing and balance located on either side of the skull.
By combining these observations, the researchers suggest that these two structures formed a complete sensory system.
Sound waves captured by the ossified lung would have been transmitted to the inner ears via this canal, enabling the animal to perceive sounds underwater.
“Our hypothesis is based on analogies with modern freshwater fish such as carp or catfish,” said Luigi Manuelli, a doctoral student at the Natural History Museum of Geneva and the University of Geneva.
“In these species, a structure known as the Weberian apparatus connects the swim bladder to the inner ear.”
“This system allows them to detect underwater waves and therefore hear underwater.”
“The air bubble contained in the swim bladder is essential for detecting these waves, which would otherwise pass through the fish’s body undetected.”
“This auditory ability was likely gradually lost as the ancestors of modern coelacanths adapted to deep marine environments. Their lung regressed, making this system unnecessary,” Professor Cavin said.
“Remarkably, some structures associated with the inner ear have nonetheless been preserved.”
“These anatomical remnants now provide valuable insight into the evolutionary history of these fish — and perhaps also into that of our own aquatic ancestors.”
The findings were published February 14, 2026 in the journal Communications Biology.
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L. Manuelli et al. 2026. A dual respiratory and auditory function for the coelacanth lung. Commun Biol 9, 400; doi: 10.1038/s42003-026-09708-6