Sauropterygian long bones with planes of section marked (arrows). A, humerus of Nothosaurus sp. indet. [from ]. Note that Nothosaurus humeri are morphologically more differentiated than those of the more advanced taxa. B, femur of Nothosaurus sp. indet. [from ]; C, humerus of Pistosaurus longaevus [from ]; D, femur of Pistosaurus longaevus [from ]; E, humerus of a plesiosaur [from ], figured for better morphological comparison with other sauropterygian long bones; F, femur of a plesiosaur [from ]. Proximal is at the top in all bones. Bones in A and D-F are shown in dorsal view; bones in B and C are shown in ventral view. Not to scale.