Une nouvelle espèce de Steneosaurus (Thalattosuchia, Teleosauridae) dans le Callovien du Poitou (France) et la systématique des Steneosaurus longirostres du Jurassique moyen d'Europe Occidentale.

Patrick Vignaud

The study of all the available skulls allows us to review the systematic relationships of the longirostrine Steneosaurus from the Middle Jurassic of western Europe. Up to now, Aalenian and Bajocian deposits have not yielded any significant Steneosaurus remain. In the Bathonian, the only valid longirostrine species, S. megistorhynchus, is known in the Britain-Normandy Basin, the Poitou and the Lorraine. In the Callovian, most of the longirostrine Steneosaurus remains can be attributed to the species S. leedsi. Nevertheless, some remains from the Middle Callovian of Poitou (France) show important differences with S. leedsi. A new Steneosaurus species, only known in Poitou, is created and named S. pictaviensis. The specific characters are carried by the skull (preorbital pit well marked, orbit and ptetygoid fossae shapes), by the mandible (symphysis shape) and by the teeth (ornamentation). S. megistorhynchus is probably situated near the stem of the Callovian species but remains from the Bathonian and Lower Callovian are very scarce and it is very difficult to precise the phylogenetic relationships between the longirostrine species of the Middle Jurassic.