Giants Among Dwarfs: The Arrival Of A New Clade Of Southern Dinosaurs In The Latest Cretaceous Of Europe

Abstract

The origin of the last sauropod dinosaur communities in Europe and their evolution in the last 15 million years of the Cretaceous has become a complex phylogenetic and paleobiogeographic puzzle portrayed by the controversy on the alleged coexistence of immigrant Gondwana-related taxa alongside relictual and insular clades. In this context, here we describe a new titanosaurian sauropod dinosaur, Abditosaurus kuhnei gen. et sp. nov., from the Upper Cretaceous (Maastrichtian) Tremp Group of Catalonia (Spain). Phylogenetic analyses recover Abditosaurus separately from the rest of European titanosaurs, within a clade of South American and African saltasaurines. The affinity of the new taxon with southern landmasses is reinforced by the spatiotemporal co-occurrence with Gondwanan titanosaur oospecies in southern Europe. The large size and the lack of osteohistological features related to insular dwarfism support the idea that Abditosaurus belongs to an immigrant lineage, unequivocally distinct from the island dwarfs of the European archipelago. The arrival of Abditosaurus lineage to the Ibero-Armorican island is hypothesized to have occurred at the earliest Maastrichtian (72 Ma), probably as a result of a global and regional sea-level drop that reactivated the ancient dispersal routes between NW Africa and SW Europe. The arrival of large-bodied titanosaurs to the European archipelago produced dramatic changes in the insular ecosystems and important evolutionary changes in the dinosaur faunas, especially with respect to the ‘island rule’ effect.