New rebbachisaurid (Dinosauria, Sauropoda) from the Huincul Formation (upper Cenomanian-Turonian) of Villa El Chocón (Neuquén Province, Argentina)

Abstract

Cienciargentina sanchezi gen. et sp. nov. is a new rebbachisaurid sauropod dinosaur from the Late Cretaceous of Argentina. The new species is erected on the basis of a unique combination of characters that includes many autapomorphies, among them: cervical epipophyses absent, anterior dorsal centra amphicoelous to slightly opisthocoelous, posterior dorsal centrum slightly opisthocoelous, posterior dorsal neural spines anteroposteriorly extended, mid and posterior dorsal vertebrae with intrapostzygapophyseal lamina supporting the postzygapophyses from below, middle and posterior dorsal vertebrae with accesory spinodiapophyseal lamina, lateral laminae in anterior caudal vertebrae formed by the spinoprezygapophyseal lamina and the spinopostzygapophyseal lamina, which fuse at the middle of the neural spine, anterior caudal vertebrae with spinoprezygapophyseal lamina more robust than spinopostzygapophyseal lamina, anterior caudal transverse processes with a full suite of diapophyseal laminae (anterior centrodiapophyseal lamina, posterior centrodiapophyseal lamina, prezygodiapophyseal lamina, postzygodiapophyseal lamina), ratio of length to height of the posterior caudal vertebrae 5 or higher, forked chevrons without anterior and posterior projections, and femoral head dorsally directed, rising well above the level of the greater trochanter. This new species is added to the list of rebbachisaurid sauropods documented in the Huincul Formation (upper Cenomanian-Turonian), which are thought to be the latest diplodocoids at global level. In fact: from the Turonian onwards, sauropod communities are composed exclusively of macronarians, mostly titanosaurs. In Patagonia, particularly in the Huincul Formation, the hypothetical faunal turnover that occurred in the middle of the Cretaceous, which involved not only sauropods but other groups of dinosaurs, is observed, perhaps like nowhere else in South America.