Computed tomography, anatomical description and three‐dimensional reconstruction of the lower jaw of E usthenopteron foordi W hiteaves, 1881 from the U pper D evonian of C anada

The cranial anatomy of the iconic early tetrapod E usthenopteron foordi is probably the best understood of all fossil fishes. In contrast, the anatomy of the lower jaw – crucial for both phylogenetics and biomechanical analyses – has been only superficially described. Computed tomography data of three E usthenopteron skulls were segmented using visualization software to digitally separate bone from matrix and individual bones from each other. Here, we present a new description of the lower jaw of E usthenopteron based on microcomputed tomography data, including the following: detailed description of sutural morphology and the mandibular symphysis; confirmed occurrence of pre‐ and intercoronoid fossae on the dorsal aspect of the lower jaw; and the arrangement of the submandibular bones. Furthermore, we identify a novel dermal ossification, the postsymphysial, present on the anteromedial aspect of the lower jaw in E usthenopteron and describe its distribution in other stem tetrapod taxa. Sutural morphology is used to infer load regimes and, along with overall skull and lower jaw morphology, suggests that E usthenopteron may have used biting along with suction feeding to capture and consume large prey. Finally, visualization software was used to repair and reconstruct the lower jaw, resulting in a three‐dimensional digital reconstruction.