| Whorl-toothed chondrichthyans (Eugeneodontiformes: Edestoidea) were among the
largest marine predators of the Pennsylvanian and Permian periods. Distinguished by a spiral of
teeth supported in the middle of both upper and lower jaws, the holotype of Sarcoprion edax
from the Upper Permian of Greenland is re-described using computed tomography.
The holotype preserves the anterior parts of the upper and lower jaws. The long upper
jaw is ventrally concave, includes left and right palatoquadrates, and encloses cartilages of the
braincase. Seven upper series teeth were likely supported in the concave ventral space at the
anteriormost part of the upper jaw. The lower jaw is Y-shaped, converging anteriorly to form a
symphyseal disc that supports 14 teeth of the lower whorl. Tooth crowns diminish in size and are
increasingly worn anteriorly. The orientation of tooth wear suggests a new reconstruction of the
jaw that places the upper tooth series anterior to the lower whorl. This new jaw model provides
greater lateral constriction between the concave upper jaw and lower whorl giving an enclosure
for efficient cutting, while supporting the prey anteriorly with the peg-like teeth of the upper
series.
Sarcoprion shares tooth features and ontogeny with both Helicoprion and
Karpinskiprion. The encapsulating cartilage in Helicoprion is analogous with the symphyseal
disc, and the Meckel's cartilages in Helicoprion are analogous with the unfused portions of the
lower jaw in Sarcoprion. These relationships can be used to construct a hypothetical jaw
morphology for the open spiral eugeneodontiform with tooth retention, Karpinskiprion.
Keywords: Sarcoprion, Chondrichthyes, Holocephali, Computed Tomography Scanning, 3-D
Modeling, Permian |