The first duckbill dinosaur (Hadrosauridae: Lambeosaurinae) from Africa and the role of oceanic dispersal in dinosaur biogeography

The Late Cretaceous saw distinctly endemic dinosaur faunas evolve in the northern and southern hemispheres. The Laurasian continents of North America and Asia were dominated by hadrosaurid and ceratopsian ornithischians, with tyrannosaurs as apex predators. In Gondwanan communities, including Africa, South America, India and Madagascar, titanosaurian sauropods dominated as herbivores and abelisaurids as predators. These patterns are thought to be driven by the breakup of Pangaea and formation of seaways limiting dispersal. Here, we report a new lambeosaurine hadrosaurid, Ajnabia odysseus gen. et sp. nov., from the upper Maastrichtian of Morocco, North Africa, the first Gondwanan representative of a clade formerly thought to be restricted to Laurasia. The new animal shows features unique to Hadrosauridae and specifically Lambeosaurinae. Phylogenetic analysis recovers it within Arenysaurini, a clade of lambeosaurines previously known only in Europe. Biogeographic modelling shows that lambeosaurines dispersed from Asia to Europe, then to Africa. Given the existence of large, persistent seaways isolating Africa and Europe from other continents, and the absence of the extensive, bidirectional interchange characterizing land bridges, these patterns suggest dispersals across marine barriers, similar to those seen in Cenozoic mammals, reptiles, and amphibians. Dispersal across marine barriers also occurs in other hadrosaurid lineages and titanosaurian sauropods, suggesting oceanic dispersal played a key role in structuring Mesozoic terrestrial dinosaur faunas.