The lost fossil of the first discovered rebbachisaurid: reassessment of Nopcsaspondylus alarconensis (Diplodocoidea, Sauropoda)

Rebbachisauridae is a group of diplodocoid sauropods mainly record from the Hauterivian to Turonian of Europe, Africa and South America. They were specifically abundant for the Cenomanian-Turonian times of Patagonia, Argentina. At now, at least six species have been recovered from the Huincul Formation, out of the 22 species currently known. However, the fragmentary nature of the bones and the isolated remains may generate an overestimated number of species. Nopcsaspondylus is known by a middle to posterior dorsal vertebra which is currently lost. The reassessment of Nopcsaspondylus does not find any diagnostic character which allows to recognise as a distinct species of rebbachisaurid. In addition, the erection of Nopcsaspondylus did not follow certain recommendations of the International Code of Zoological Nomenclature (ICZN), allowing to determinate that Nopcsaspondylus represents a nomen dubium.