Resumen
The Neuquén Basin in northwestern Patagonia, Argentina, holds the most important record of Cretaceous
dinosaurs in South America.The Neuquén Group (Upper Cretaceous) is the richest dinosaur-bearing unit of the basin. It
comprises the Río Limay, the Río Neuquén and the Río Colorado subgroups. In this study, dinosaur remains from the Río
Neuquén and the Río Colorado subgroups outcropping in Mendoza are examined. In this group, isolated, disarticulated
or partially articulated sauropods and theropods are abundant. However, little is known about the diagenetic history
of fossil assemblages. In southern Mendoza, three fossiliferous sites were found in the areas of Paso de las Bardas
(Quebrada Norte) and Cerro Guillermo (CG1, CG2). This study aims to add to the knowledge of diagenetic processes
involving dinosaur remains from the Neuquén Group, as well as their relation to the depositional environment. Histologic
features and diagenetic processes of dinosaur bones were analyzed through thin sections in order to interpret the degree
of taphonomic alteration. The fossil-diagenetic processes inferred include substitution, fracturing, plastic deformation
and different permineralization events. Combined analyses through X-ray diffractometry (XRD) and petrographic studies
reveal the substitution of hydroxyapatite by francolite. The presence of fluorine -in one of the cases- suggests a link
between the elemental composition and depositional environments: floodplain and fluvial channel. Permineralization
stages include infilling of vascular canals, trabeculae and fractures with iron oxides and iron carbonate minerals during
the burial history. This contribution represents an integral approach to the study of Cretaceous dinosaurs for assessing the
diagenetic changes in the bone microstructure and the differential preservation of fossil remains in fluvial environments.