The latest Cretaceous was a crucial time for the evolution of terrestrial life ending with one of the most severe mass extinctions of all time. However, the evidence contributing to our understanding of terrestrial ecosystem dynamics in the last few million years before the extinction is limited to a few fossil assemblages, with Europe being particularly poorly sampled. Even such iconic uppermost Cretaceous vertebrate faunas as that of Transylvania (western Romania) are left with fundamental questions to be answered related to taxonomic and ecological diversity. In particular, several recently collected spectacular fossil vertebrate specimens from Transylvania yield novel implications for species-level and ecological diversity and await detailed study. Moreover, palaeoecological analyses are yet to be rigorously applied to this fauna. The overarching goal of the proposed project is two-fold: first, a re-evaluation of taxonomic diversity of the terrestrial latest Cretaceous vertebrates from Transylvania based primarily on this new material and second, a partial aut- and synecological reconstruction of select vertebrate taxa. The new material includes several specimens of dinosaurs, crocodyliforms, turtles and with near-complete preservation that is unprecedented in the Upper Cretaceous of Transylvania for the respective taxa. Preliminary examination of these key specimens indicate that taxonomic diversity of the ornithopod dinosaurs and turtles was higher than previously thought, while the diversity of crocodyliforms has likely been overestimated. Key outcomes of this project include detailed taxonomic analysis through µCT-informed osteological description of these specimens in order to reassess species-level diversity. In addition, δ13C and δ18O stable isotope analysis of fossil teeth and bones together with bioerosional trace fossil analysis of bones will test for potential habitat niche partitioning between different turtle and crocodyliform taxa as well as for habitat and dietary niche partitioning between the different herbivorous dinosaurs in Transylvania. This project will contribute to a better understanding of European terrestrial ecosystems, shortly before the end of the Cretaceous.