First evidence of air-breathing in a fossil polypterid

Abstract This study presents the first evidence of air-breathing in a fossil polypterid, † Polypterus faraou , from the Miocene of Chad, using CT-scan 3D imaging. The † P. faraou specimen preserves open spiracles with associated bones functioning as air valves. It also retains features of the buccal pump mechanism, including a combination of a broad palate region, an elongated parasphenoid, and a mobile hyoid arch, all indicative of air-breathing capability. The arrangement of overlapping peg-and-socket scales suggests the potential for scale-mediated aspiration, akin to that of modern polypterids. These findings strongly support the hypothesis that † P. faraou employed both buccal pumping and recoil aspiration for lung ventilation. We recognize that the characters analysed here not only support the buccal pump mechanism but also contribute to prey capture. This study provides the first evidence of air-breathing in fossil polypterids, as well as in fossil actinopterygians, highlighting the relevance of polypterids for investigating the evolution of aerial respiration in vertebrates.