A titanosaurian sauropod with Gondwanan affinities in the latest Cretaceous of Europe.

The origin of the last sauropod dinosaur communities in Europe and their evolution during the final 15 million years of the Cretaceous have become a complex phylogenetic and palaeobiogeographic puzzle characterized by the controversy on the alleged coexistence of immigrant, Gondwana-related taxa alongside relictual and insular clades. In this context, we describe a new titanosaurian sauropod dinosaur, Abditosaurus kuehnei gen. et sp. nov., from the Late Cretaceous (Maastrichtian) Tremp Group of Catalonia (Spain). Phylogenetic analyses recover Abditosaurus separately from other European titanosaurs, within a clade of otherwise South American and African saltasaurines. The affinity of the new taxon with southern landmasses is reinforced by spatiotemporal co-occurrence with Gondwanan titanosaurian oospecies in southern Europe. The large size and the lack of osteohistological features potentially related to insular dwarfism or size reduction support the idea that Abditosaurus belongs to an immigrant lineage, unequivocally distinct from some of the island dwarfs of the European archipelago. The arrival of the Abditosaurus lineage to the Ibero-Armorican Island is hypothesized to have occurred during the earliest Maastrichtian (70.6 Ma), probably as a result of a global and regional sea-level drop that reactivated ancient dispersal routes between Africa and Europe. The arrival of large-bodied titanosaurs to the European archipelago produced dramatic changes in its insular ecosystems and important evolutionary changes in its dinosaur faunas, especially with respect to the 'island rule' effect.