First record of a Valanginian (Early Cretaceous) dinosaur association from South America. Journal of Vertebrate Paleontology 75 (A)

RODOLFO A. CORIA; PHILLIP J. CURRIE; EVA KOPPELHUS; ANDREAS BRAUN; IGNACIO A. CERDA

Pittsburg, Pensilvania, Estado Unidos

Jornada; 70th meeting of the Society of Vertebrate Paleontology; 2010

A new and varied dinosaur association, represented by ornithopod, theropod and sauropod remains, has been discovered in the coarse, terrestrial sandstones of the Mulichinco Formation (Upper Valanginian, Early Cretaceous) exposed in Neuquén Province, Patagonia, Argentina. All skeletal remains come from a single stratum with sedimentologic characteristics that suggest it represents a catastrophic alluvial event. Two semi-articulated skeletons already have alreadyhave been collected, and several more have been located for future collection. Some of the fossils have been heavily weathered by dissolution action of plant roots. However, in certain areas, the fossil remains are well preserved in hard, cemented, concretionary sandstones. Associated fossil plants include conifers and ferns. This new locality brings information about a key moment of the evolution of the Cretaceous dinosaur faunas of Patagonia. Despite information from the terminal levels of the Jurassic and the rich dinosaur associations identified in different levels of the post-Hauterivian Cretaceous, the diversity of Valanginian dinosaurs was completely unknown in South America, and is scarce worldwide. Certain anatomical features of the collected specimens suggest abelisaur affinities in the theropods, advanced hadrosauroid conditions in the ornithopods, and basal titanosauromorph characters for the sauropods. So far, none of the identified specimens is particularly large, in comparison with the giant theropods and sauropods that subsequently dominated this region. Although preliminary taxonomic identification of both theropods and sauropods matches with what could be expected, the presence of an hadrosauroid ornithopod more advanced than those recorded in younger levels, encourage revisiting the phylogeny of this clade as well as reviewing current hypothesis about their paleogeography.