A new species of Shantungosuchus from the Lower Cretaceous of Inner Mongolia (China), with comments on S. chuhsienensis Young, 1961 and the phylogenetic position of the genus

ABSTRACT

Shantungosuchus hangjinensis, sp. nov. is described on the basis of a partial skull and lower jaws from the Lower Cretaceous Luohandong Formation, Zhidan Group of Hangjin Qi, Inner Mongolia (China). S. chuhsienensis, from the ?Upper Jurassic deposits of Shandong province, eastern China, is re-examined. Shantungosuchus is primarily distinguished from all other crocodyliforms by a short premaxilla/maxillary portion of the skull, a transversely broad shelf of the jugal ventral to the orbit, a pair of posterolaterally divergent ridges on the pterygoid, a pair of large basisphenoid depressions, the exclusion of the angular from posterolateral surface of the mandible, and the superficially asymmetrical appearance of the two dentaries in the symphysial region. Shantungosuchus is probably also unique in possessing a quadratojugal fossa, a leaf-shaped palatine separated from the suborbital fenestra, a pronounced coronoid projection of the surangular, and a tibia longer than the femur. A phylogenetic analysis of the early crocodyliforms represented by better preserved material tentatively indicates that the Protosuchia is monophyletic and strongly suggests that Shantungosuchus is closely related to the Protosuchidae rather than to the Atoposauridae of the “Mesosuchia.”