The diversity of sauropod dinosaurs and their first taxonomic succession from the latest Cretaceous of southwestern Europe: Clues to demise and extinction

Southwestern Europe is a key setting to evaluate the diversity of non-avian dinosaurs before the end of the Cretaceous (below the K–Pg boundary). The ancient Ibero-Armorican Island, encompassing the current regions of North-East Iberia and South France, provides a substantial record of sauropod fossils. The study of multiple sauropod femora from localities where upper Campanian to uppermost Maastrichtian successions are both exposed, together with the integration of the information gathered from previously known localities has allowed the biodiversity of sauropods to be reassessed within a precise and clear chronostratigraphic framework. From the studied sample several titanosaur forms have been distinguished including a gracile and small-sized titanosaur (Lirainosaurus astibiae), a robust medium-sized titanosaur (Ampelosaurus atacis), a gracile medium-sized titanosaur (Atsinganosaurus velauciensis), and five other indeterminate but distinct titanosaurs, which span the late Campanian through the entire Maastrichtian. The youngest of these occurs in the uppermost part of palaeomagnetic chron C30n in the latest Maastrichtian (~ 0.4–1 Ma before the K–Pg boundary), representing the youngest sauropod yet documented in Eurasia. The pattern of diversity on the Ibero-Armorican Island rules out a decline in sauropod diversity at the very end of the Cretaceous. As with other regions during the late Cretaceous, the abundance and quality of the sauropod fossil record is probably influenced by multiple biases (sampling, ecological, and environmental).