RESEARCH ARTICLE Descriptive Anatomy and Three-Dimensional Reconstruction of the Skull of the Early

The early tetrapod Acanthostega gunnari is an iconic fossil taxon exhibiting skeletal mor-phology reflecting the transition of vertebrates from water onto land. Computed tomography data of two Acanthostega skulls was segmented using visualization software to digitally separate bone from matrix and individual bones of the skull from each other. A revised de-scription of cranial and lower jaw anatomy in this taxon based on CT data includes new de-tails of sutural morphology, the previously undescribed quadrate and articular bones, and the mandibular symphysis. Sutural morphology is used to infer loading regime in the skull during feeding, and suggests Acanthostega used its anterior jaws to initially seize prey while smaller posterior teeth were used to restrain struggling prey during ingestion. Novel methods were used to repair and retrodeform the skull, resulting in a three-dimensional digi-tal reconstruction that features a longer postorbital region and more strongly hooked anteri-or lower jaw than previous attempts while supporting the presence of a midline gap between the nasals and median rostrals