For over a century, the enigmatic coelacanth has captivated the curiosity of evolutionary biologists and paleontologists alike, a living fossil that bridges the aquatic and terrestrial worlds. Recent groundbreaking research spearheaded by an international collaboration between the Natural History Museum of Geneva (MHNG) and the University of Geneva (UNIGE) has revealed astonishing new insights into how these ancient creatures, dating back some 240 million years, perceived their underwater environment. Utilizing cutting-edge synchrotron imaging techniques, researchers have unearthed compelling evidence that certain Triassic coelacanths did not simply breathe air with their lungs but also employed this organ as an auditory apparatus, a dual function that rewrites our understanding of vertebrate sensory evolution.
Coelacanths are among the most primitive lobe-finned fishes, uniquely positioned on the evolutionary tree closer to terrestrial vertebrates than to modern bony fish. Today’s extant coelacanths, mostly of the genus Latimeria, inhabit deep marine environments, relying exclusively on gill respiration. However, the fossil record tells a much more diversified story. Triassic coelacanth species possessed a robust, ossified lung enveloped by overlapping bony plates, a structural adaptation historically interpreted purely through the lens of air breathing. This traditional view, while compelling, fell short of fully explaining the complex morphology observable in these ancient specimens.
At the core of this research lies advanced synchrotron X-ray imaging performed at the European Synchrotron Radiation Facility in Grenoble, an approach allowing unparalleled micrometric resolution of fossil internal anatomy. Lionel Cavin, curator at the MHNG, and his team meticulously scanned Triassic coelacanth fossils excavated in Lorraine, France. This non-destructive imaging revealed a hitherto unknown association between the ossified lung and auditory structures of the skull, specifically bony wing-like projections at the lung’s distal ends, intimately linked with the inner ear housed within the prootic bone. Such morphological nuances are not discernible through conventional paleontological methods, underscoring the transformative potential of synchrotron technology.
In parallel, developmental studies of extant coelacanth embryos unveiled a specialized canal anatomy connecting the inner ear with the lung structure. This anatomical conduit hints at an integrated sensory system capable of detecting underwater sound waves using the lung as a resonating medium, channeling vibrational information directly to the vestibular apparatus. These findings elegantly mirror the Weberian apparatus found in certain modern teleost fishes such as carp and catfish, where a chain of bones transmits pressure fluctuations from the swim bladder to auditory sensors, enabling acute underwater hearing.
The physiological principle behind this ancient auditory system hinges on the presence of air or gas within the lung, acting as a compressible medium that converts acoustic signals into mechanical vibrations. These vibrations propagate through ossified structures – the bony wings – toward the inner ear, where sensory hair cells transduce them into neural signals for sound perception. Unlike modern coelacanths which have forfeited this lung-mediated auditory capability amidst evolutionary adaptation to deep-sea environs, their Triassic ancestors possessed a sophisticated system blending respiration and acoustic sensing.
This revelation fundamentally challenges prior assumptions that the coelacanth lung served merely as a vestigial organ or solely for aerial respiration. Instead, it highlights a multifunctional role, expanding the organ’s evolutionary significance. The gradual reduction of the ossified lung observed in later coelacanth lineages correlated with a diminishing reliance on this auditory function, likely reflecting ecological transitions from shallow, acoustically rich habitats to the resource-scarce, deep marine layers they occupy today.
Beyond enriching our knowledge of coelacanth biology, these results have profound implications for vertebrate sensory system evolution. They suggest that auditory systems in early lobe-finned fish might have employed diverse anatomical substrates for sound detection prior to the refinement of more modern mechanisms. This ancestral dual-function lung system could also shed light on the evolutionary origins of auditory adaptations seen in tetrapods, bridging the gap between aquatic and terrestrial modalities of hearing.
Moreover, the preservation of associated inner ear structures, albeit as vestigial remnants in modern coelacanths, offers a tantalizing glimpse into the sensory capabilities of our biomechanical predecessors. Continued investigation into these evolutionary leftovers may inform broader concepts of how environmental pressures moulded sensory organ morphology and function across geological timescales.
The interdisciplinary approach merging paleontological fossils with embryological and anatomical investigations exemplifies a new paradigm in evolutionary biology. It underscores the necessity of integrating cutting-edge imaging modalities with comparative anatomy to unravel the mysteries enshrined within the fossil record, bolstering our comprehension of life’s complex evolutionary tapestry.
As our understanding deepens, the coelacanth’s dual respiratory and auditory lung unfolds as a remarkable evolutionary innovation, emblematic of nature’s intricate solutions to environmental challenges. Future research will undoubtedly probe the extent of this sensory adaptation across other ancient fish lineages and explore its potential analogs, fostering a richer appreciation of vertebrate auditory evolution.
In essence, these findings elevate the coelacanth from a mere evolutionary curiosity to a profound model of multifunctional organ design, epitomizing the interplay between structure, function, and evolutionary history that continues to define the natural world.
Subject of Research: Not applicable
Article Title: A dual respiratory and auditory function for the coelacanth lung
News Publication Date: 19-Mar-2026
Web References:
10.1038/s42003-026-09708-6
Image Credits: © L. Manuelli–MHNG
Keywords: coelacanth, sensory evolution, synchtrotron imaging, Triassic fishes, auditory system, ossified lung, vertebrate evolution, inner ear, Weberian apparatus, paleontology, lobe-finned fish, aquatic respiration, fossil imaging
