New insights into the postcranial anatomy of Paludidraco multidentatus (Sauropterygia, Simosauridae), from the Late Triassic of Spain

Sauropterygia is a diverse clade of aquatic reptiles spanning from the Lower Triassic (Olenekian) to the uppermost Cretaceous (Maastrichtian). Complete or almost complete skeletons are known for placodonts, pachypleurosaurs, nothosaurs and pistosauroids (including plesiosaurs). Conversely, the postcranial skeleton of the Triassic clade Simosauridae is mostly represented by fragmentary and / or isolated material of limited taxonomically informative nature.

Simosauridae is represented by two valid species: Simosaurus gaillardoti, from the Ladinian (Middle Triassic) of France and Germany; and Paludidraco multidentatus, from the Carnian (Late Triassic) of Central Spain. Relatively complete skeletons of Simosauridae are limited to two individuals of S. gaillardoti and to the holotype of P. multidentatus. However, the latter three simosaurid individuals lack most of the cervical and caudal regions.

The P. multidentatus holotype also lacks fore-limb and hind-limb zeugopodial and autopodial elements. Therefore, the current knowledge on the simosaurid postcranial anatomy is very limited relative to that of other Triassic sauropterygians. In addition to its holotype, P. multidentatus was described based on a relatively complete skull, i. e. the paratype.

We describe here the second articulated and relatively complete postcranial skeleton of P. multidentatus, corresponding to that of the paratype, which remained unpublished until now. This individual is larger than the holotype, allowing us to provide a discussion on the intraspecific variability of P. multidentatus for the first time. Moreover, the paratype provides valuable anatomical information of both unknown (i. e. zeugopodial elements) and poorly known (i. e. pectoral and pelvic girdle regions, caudal vertebrae and ribs and gastralia) postcranial elements for this taxon.