Pistosaurus longaevus (von Huene 1948) Late Anisian, Middle Triassic, ~2-3 m in length, appears to bridge the gap between nothosaurs and plesiosaurs. Prior workers have reconstructed the skull in different fashions, both with various apomorphies or potential problems. For instance the lateral and palatal views of the Rieppel tooth count differ. Derived from a sister to Anningasaura and Simosaurus, Pistosaurus phylogenetically preceded the longer snouted pliosaurs such as Trinacromerum.
Distinct from Simosaurus, the skull of Pistosaurus was relatively smaller with a longer, narrower premaxillary rostrum. The parietal was narrower. The postfrontal and postorbital were more gracile. The prefrontal was larger. The pterygoid had a larger, longer quadrate process. The external and internal nares were tiny with a larger palatal contribution from the maxilla. The premaxillary teeth were larger than the maxillary teeth. In comparison to Augustasaurus, the occiput was likely vertical, but not so tall as Rieppel indicates.
The dorsal series was stiff, like that of Plesiosaurus, with enlarged transverse processes and more robust neural spines. The caudals were smaller overall.
The scapula was smaller. The humerus was straighter with an expanded distal end. The radius and ulna were shorter.
If the ilium is known for Pistosaurus, von Huene may have inverted it as shown above. The hind limb is not well known. |
