Varanodon agilis (Olsen 1965) Late Permian ~265 mya, 17.5 cm skull length, was notable for having a possible antorbital fenestra, but no other related taxa have that, so it is probably an artifact of preservation. Derived from a sister to Protorothyris, Varanops phylogenetically preceded Heleosaurus at the base of the protodiapsida. Varanodon was a sister taxon and they left no known descendants. The skull of Varanodon was compared to the skull of Proterosuchus a basal euarchosauriform (Reig 1970), but the two are not closely related.
Distinct from Protorothyris the skull of Varanodon is extended posteriorly at the jawline. Thus the squamosal leans strongly anteriorly and the mandible is longer than the skull. A large lateral temporal fenestra is present, largely due to the excavation of the squamosal which retains a point of contact with the jugal. The canine tooth is difficult to see as most of the teeth are caniniform in appearance.
The cervicals decrease in length but increae in height posteriorly, the opposite of Protorothyris.
The radius and ulna were strongly bowed. The carpus was well ossified. Metacarpal IV was the broadest.
The femur was hourglass-shaped. The tibia and fibula were both robust. Metatarsal IV was by far the largest of the metatarsals. The toes were extraordinarily different in their lengths culminating in digit IV. |
