Reevaluation of the axial skeleton referred to Neuquensaurus robustus (Huene, 1929) and its taxonomic separation from Neuquensaurus australis (Lydekker, 1983)

VIRGINIA ZURRIAGUZ; ALEJANDRO OTERO

Anillaco

Jornada; 28º Jornadas Argentinas de Paleontología de Vertebrados; 2013

CRILAR

The genus Neuquensaurus, from the Late Cretaceous of Argentina, comprises two species: Neuquensaurus australis (Lydekker, 1893) and Neuquensaurus robustus (Huene, 1929), both taxonomically separated by Huene based on proportions of the limb bones. Currently, N. robustus is regarded as nomen dubium because of the lack of solid diagnostic features that separate it from N. australis. We compared both species of Neuquensaurus, analyzing the holotype and referred specimens of N. australis with equivalent structures of referred specimens of N. robustus in order to establish if differences are deemed of taxonomic importance. For instance, in the first caudal vertebra the plane that contains the transverse process in N. australis is almost vertical, whereas the same structure is oblique in N. robustus; in the latter taxon the interprezygapophyseal lamina continues posteriorly forming a roof over the neural canal, which is absent in N. australis. In cervical vertebrae the spinoprezygapophyseal laminae are closer in N. australis than in N. robustus, and in the latter taxon there are two accessory laminae which run almost parallel to each other and are placed inside the prespinal fossa. This feature is not present in N. australis. Finally, dorsal centra are proportionally longer in N. robustus, among others. This study demonstrates that the differences between N. australis and N. robustus are not solely based on the appendicular robustness, as previously stated, but also by many axial characters that distinguish them as separate taxonomic units. Some elements referred to N. robustus, however, may belong to N. australis, and others to a different taxa.