Interactive 3D PDF model of <i>Latimeria chalumnae</i> oesophagus and vestigial lung. Three-dimensional reconstruction of the lung and oesophagus of the adult specimen CCC 28. Yellow, oesophagus; red, vestigial lung. from Lung anatomy and histology of the extant coelacanth shed light on the loss of air-breathing during deep-water adaptation in actinistians

Lungs are specialized organs that originated from the posterior pharyngeal cavity and considered as plesiomorphic for osteichthyans, as they are found in extant basal actinopterygians (i.e. <i>Polypterus</i>) and in all major groups of extant sarcopterygians. The presence of a vestigial lung in adult stages of the extant coelacanth <i>Latimeria chalumnae</i> is the result of allometric growth during ontogeny, in relation with deep times adaptation to deep water. Here, we present the first detailed histological and anatomical description of the lung of <i>Latimeria chalumnae</i>, providing new insights into its arrested differentiation in an air-breathing complex, mainly represented by the absence of pneumocytes and of compartmentalization in the latest ontogenetic stages.