Eusaurosphargis dalsassoi (Nosotti and Rieppel 2003; BES SC 390; Middle Triassic, ~240 mya, ~20 cm snout to vent length) was considered more closely related to Helveticosaurus than to placodonts. Here both Eusaurosphargis and Helveticosaurus nest within the Thalattosauriformes close to Vancleavea. Here Eusaurosphargis does not nest close to Sinosaurophargis. The skeleton BES SC 390 of Eusaurosphargis appears to be complete, but is completely disarticulated. That makes reconstruction particularly difficult. Thus the order of the traced vertebrae in dorsal view above is largely guesswork. Likewise, the skull includes some guesswork.
Overall much smaller than and distinct from Helveticosaurus, the skull of Eusaurosphargis was shorter overall and wider posteriorly. It had an upturned premaxilla and thus had procumbent premaxillary teeth. The long axis of the nasal was angled vertically, (as in Vancleavea). The postorbital was not as deep as in Helveticosaurus.
The vertebrae were far fewer in number and individually longer. The transverse processes were elongated and robust. The dorsal ribs were shorter. The torso was wider and flatter overall.
The scapula and coracoid was not as tall. The humerus was relatively longer with a narrow central portion. The radius and ulna were relatively shorter.
The pelvis was relatively larger. The ilium was shorter anteriorly and longer posteriorly. Like the humerus, the femur was relatively longer and waisted at mid length.
As in Vancleavea, osteoderms protected parts of the body. They are likewise scattered on the fossil.
A family tree of the Enaliosauria is here. A more complete tree of the Reptilia is here. The wide variety displayed by thalattosauriforms hints at a wider variety and several missing links yet to be discovered. |
