A new large <i>Nothosaurus</i> (Reptilia: Eosauropterygia) from the Middle Triassic of South China and the phylogeny of Eosauropterygia

Abstract Recent discoveries of many new marine reptiles from the Triassic of South China played an important role in understanding the shallow marine ecosystem recovery after the Permo-Triassic mass extinction. Here we report a new large nothosaurian marine reptile, Nothosaurus fortihumeralis sp. nov., represented by three specimens from the Upper Member of the Guanling Formation (middle Anisian, Middle Triassic) of Luxi, South China. Bone histology indicates that the largest individual was adult and close to skeletal maturation. Nothosaurus fortihumeralis is recognized through a combination of apomorphies including: massive humerus with a robust proximal region; distinctly constricted humeral mid-shaft that is half the width of the distal end; distinctly elongated scapular dorsal process tapering to a relatively sharp tip; iliac blade reduced but projecting slightly beyond the posterior margin of the acetabulum. The phylogenetic analysis recovered a monophyletic Nothosaurus with N. fortihumeralis as the sister taxon to Nothosaurus jagisteus. The monophyly of Eusauropterygia is collapsed, with Pachypleurosauria and Nothosauroidea forming a monophyletic Nothosauriformes. Hanosaurus and Majiashanosaurus comprise the consecutive sister groups of Nothosauriformes; together they form a monophyletic Nothosauromorpha. The discovery of N. fortihumeralis adds to the existing evidence of highly diversified large predators in the shallow seas of the eastern Tethys during the Anisian.