# A dual respiratory and auditory function for the coelacanth lung

## TL;DR

Fossil and living coelacanth studies show that ancient coelacanth lungs had both breathing and hearing roles, using a system to transmit sound to the inner ear.

## Contribution

The discovery of a dual respiratory and auditory function in the coelacanth lung using synchrotron imaging and 3D reconstructions.

## Key findings

- Extinct coelacanth lungs transmitted sound pressure to the inner ear via a perilymphatic system.
- Synchrotron scans and 3D reconstructions revealed the lung's dual function in both respiration and hearing.
- The ossified lung structure in fossil coelacanths supports both breathing and auditory roles.

## Abstract

Since the discovery of Latimeria chalumnae, coelacanths have provided a critical comparative framework for reconstructing ancestral sarcopterygian anatomy. However, the function of several anatomical features in both extant and fossil coelacanths remains unresolved. Among these, the presence of large ossified chambers in the body cavity of fossil coelacanths has remained enigmatic, with different studies proposing respiratory or auditory functions. Here, we examine lung and inner ear anatomy based on new observations from synchrotron phase-contrast microCT scans of two 240-million-year-old latimerioid coelacanths, alongside multiple developmental stages of the extant L. chalumnae. These data, combined with archival histological sections of L. chalumnae and 3D reconstructions of a Devonian coelacanth, suggest that extinct coelacanths possessed an ossified lung capable of transmitting sound pressure to auditory sensory epithelia in the inner ear via a perilymphatic system. We propose that the lung of extinct coelacanths supported both respiratory and auditory functions.

Synchrotron imaging of fossil and extant coelacanths reveals that the lung of extinct species likely served both respiratory and auditory functions, transmitting sound pressure to the inner ear via a specialized perilymphatic system