A rare partial postcranium and isolated humeri of Nothosaurus from the Lower Muschelkalk of Winterswijk, The Netherlands are described. The partial skeleton consists of a vertebral column with ribs, pectoral girdleelements, and incomplete forelimbs. Because current species-level taxonomy of Nothosaurus is based only on features of the skull, we examined the postcranial morphology in detail in order to assign the skeleton to a valid species. We focused on the humerus because this bone generally shows a complex morphology in Lower Muschelkalk Nothosaurus. Three different humerus morphotypes were recognized in the Winterswijk material, which were also seen among humeri from other Lower and lowermost Middle Muschelkalk localities such as Rüdersdorf and Oberdorla (both in Germany), and Gogolin (Poland). Morphotype I is characterized by a slender appearance with a bulky proximal end. The preaxial and postaxial edges of the shaft are very distinct, and the distal end is fan-shaped. Morphotype II is rather small and gracile with the distal end being only slightly fan-shaped. Morphotype III is rather large with an especially massive proximal end, and the distal end is thick and shovel-like. Ontogenetic variation could also be recognized within the morphotypes. Onesmall humerus from Oberdorla belongs to a juvenile and cannot be assigned to a specific morphotype. Type II humeri belong to the N. winterswijkensis-N. marchicus clade. Type III may represent a sexual morph of type II humeri and typeI a new species of Nothosaurus, or both may pertain to the nothosaurian Germanosaurus and/or the eosauropterygian Cymatosaurus.