Palaeoenvironments of the latest Cretaceous (Maastrichtian) dinosaurs of Romania: insights from fluvial deposits and paleosols of the Transylvanian and Haţeg basins

Comparison of the studied formations to the famous contemporaneous Sânpetru Formation of the HaÅ£eg Basin confirms similarity of palaeoclimatic conditions. However, palaeoenvironmental and taphonomic conditions differ. Whereas the Sânpetru Formation comprises a mosaic of wetlands and moderately-drained floodplains in which areas of impeded drainage were predominant, the Red Continental Strata, Densuş-Ciula Formation, and Pui beds represent moderately- to well-drained floodplain settings. Although the Pui beds have long been assumed to pertain to the Sânpetru Formation on the basis of palaeontological and superficial lithological similarities (i.e., red colour), comparison of the results of the detailed palaeoenvironmental studies suggests that the Pui beds are distinct from the Sânpetru Formation and may warrant their own formational recognition (Bărbat Formation). Finally, fossil preservation conditions in the Sânpetru Formation indicate concentration of remains by hydraulic processes on wet floodplains (lenticular bonebeds or “fossiliferous pockets”) while those of the other three formations suggest attritional mortality assemblages preserved in dry paleosol profiles. Such taphonomic differences must be considered carefully in palaeoecological studies of the Maastrichtian dinosaurian fauna of Romania.