The tetrapodomorph fish Spodichthys buetleri from the Upper Devonian of East Greenland is redescribed from computed tomography scans of material originally studied by Erik Jarvik. A wealth of new anatomical data was revealed by scanning the nearly perfectly three-dimensional specimens, including detailed information on the shape of the brain cavity and the internal structure of the lower jaws. Spodichthys displays an interesting mix of generalized “osteolepidid,” or primitive tetrapodomorph, and tristichopterid features. Derived characters shared by Spodichthys, tristichopterids and (Panderichthys Tetrapoda) include the loss of cosmine, a small kite-shaped parasymphysial plate, and a long commissural lamina of the entopterygoid. The presence of an extratemporal lateral to the tabular and a single fang position on the posterior coronoid and ectopterygoid are examples of basal tetrapodomorph characters retained in Spodichthys. Spodichthys is unique in having coronoid fangs positioned lateral to the corresponding replacement pit rather than having an anterior-posterior alternation between developed fang and replacement pit, which is the normal tetrapodomorph condition. Jarvik's original conclusion that Spodichthys is closely related to the tristichopterids is confirmed by a phylogenetic analysis, which places Spodichthys as the sister taxon of the Tristichopteridae.
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Vol. 28 • No. 3