The Sauropterygian genera Chinchenia, Kwangsisaurus, and Sanchiaosaurus from the Lower and Middle Triassic of China

The incomplete remains of three monotypic genera of Sauropterygia from the Lower(?) and Middle Triassic of China are re-described in detail, and their phylogenetic interrelationships are assessed on the basis of parsimony. The taxa are Chinchenia sungi Young, 1965, from the upper Middle Triassic, Kwangsisaurus orientalis Young, 1959, from the upper Lower or lower Middle Triassic, and Sanchiaosaurus dengi Young, 1965, from the lower Middle Triassic. Chinchenia and Kwangsisaurus are basal representatives of the pistosauroidean clade, and fall into an unresolved trichotomy with Corosaurus from the western United States. Sanchiaosaurus is the sister-taxon of all other Nothosauroidea, known from China, Europe and the Middle East. Collectively, the Sauropterygia from the western Pacific faunal province show dual paleobiogeographic affinities: representatives of the nothosauroidean clade share western Tethyan affinities, whereas representatives of the pistosauroidean clade share eastern Pacific affinities.