The anatomy of a specimen of Lariosaurus xingyiensis (IVPP V 11866) from the Middle Triassic of southern China is described in detail. The specimen ranks among the best preserved of its genus. Specimen IVPP V 11866 is the first unequivocal record of the occurrence of Lariosaurus in the Triassic of southern China, indeed the first record of this genus outside the western Tethyan province. A cladistic analysis using parsimony found IVPP V 11866 to represent the sister taxon of Lariosaurus calcagnii from the Middle Triassic of the southern Alps. This result reinforces the signal for western Tethyan paleobiogeographic relationships of the Triassic marine reptiles from southern China.