Diversity of hadrosauroid dinosaurs from the Late Cretaceous Ibero-Armorican Island (European Archipelago) assessed from dentary morphology

A substantial part of the European record of hadrosauroid ornithopod dinosaurs comes from the Maastrichtian (Upper Cretaceous) strata of the south-central Pyrenees (northern Catalunya and Aragón, northeastern Spain). Yet, our understanding on the taxonomy and phylogenetic systematics of these animals in this region is hindered by the lack of complete specimens, paucity of diagnostic material, and poor preservation of the fossils. The Basturs Poble site (Lleida Province, northern Catalunya) has yielded over 900 bones attributed to a hadrosauroid monodominant population. The dentary is the most common, and one of the better-preserved elements found in this locality. Here, we evaluate the utility of dentary morphology as an indicator of hadrosauroid taxonomic diversity. We do so via principal component analysis, cluster analysis, and mean comparison tests of various morphometric data from the available sample of dentaries collected so far in the Basturs Poble locality and other Maastrichtian sites in northeastern Spain. Three different dentary morphotypes are recognized: two different hadrosauroids, one more derived than the other, and one lambeosaurine type. One of the hadrosauroid morphotypes corresponds to relatively small individuals that may represent insular dwarf species. Concerning Basturs Poble locality, our results suggest the coexistence of hadrosauroid and lambeosaurine dinosaurs during the late Maastrichtian on the Ibero-Armorican Island.