Abstract The holotype is the single most important specimen in zoological taxonomy, and to avoid confusion, it must be the remains of a single individual. Re–evaluation of data presented to infer that three specimens collected between 1954 and 1998 are additional material of the holotype of Elasmosaurus platyurus, indicate there is no evidence these two sets of remains belong to the same individual, or the genus Elasmosaurus. Historical documents indicate the missing skeletal elements of the Elasmosaurus holotype (including dorsal vertebrae and gastralia) can be explained by factors such as weathering and collection failure. The relative absence of gastroliths, if originally associated with the animal, can be explained by the collecting methods employed, or the absence in 1867–1868 of a theoretical framework to explain their presence in a plesiosaur.

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