Vallesaurus cenensis (Wild 1990,
Renesto and Binelli 2006) was a basal drepanosaurid from the Late Triassic (Norian) derived from a sister to Hypuronector. Vallesaurus phylogenetically preceded Megalancosaurus and Drepanosaurus.
Distinct from Jesairosaurus, the skull of Vallesaurus was much shorter. The narial opening was tremendously expanded, encompassing the majority of the rostrum. The lacrimal was reduced to a mere strut. The ascending process of the maxilla was likewise strut-like. Together these created a larger antorbital fenestra. The postorbital was raised, decreasing the exposure of the upper temporal fenestra to the occipital plane. The jugal has a quadratojugal process and a quadratojugal emerged from it to cross the relatively short space to the quadrate, which leaned posteriorly.
Distinct from Hypuronector, the post cranial skeleton was likewise shortened and compressed. The caudal chevrons were no deeper than than the caudal neural spines. The tip of the tail curled ventrally creating a hook at the tip suggesting a prehensile capability, as in living chameleons, primates and the oppossum.
The scapula curled anteriorly. The manus was larger relative to the forelimb.
The hind limb was no longer than the fore limb. The fibula was similar in width to the tibia and slightly bowed apart from it. The proximal tarsals were fused. The medial digits were relatively larger. Pedal 1.2 was greatly enlarged and curved. |
