Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile

Abstract In the dusk of the dinosaur era, the advanced duck-billed dinosaurs (Family Hadrosauridae) are thought to have outcompeted other herbivores, making ecosystems less diverse and more vulnerable to the Cretaceous-Paleogene asteroid impact. They were also among the first terrestrial organisms to disperse from North America into South America. Here, we present the first new species of subantarctic duck-billed dinosaur, CPAP 3054, of early Maastrichtian age in Magallanes, Chile. Surprisingly, unlike duckbills further north in Patagonia, CPAP 3054 is not an advanced duckbill, but descends from North American forms that were transitional to Hadrosauridae, diverging shortly before the origin of this family. In North America, these forms were replaced by hadrosaurids in the late Campanian. The survival into the Maastrichtian of a pre-hadrosaurid lineage suggests the ancestors of CPAP 3054 arrived earlier in South America than the hadrosaurids, reaching further south before the Cretaceous-Paleogene mass extinction, where they avoided competition from hadrosaurids. Additional note This work contains a new biological name. New names in preprints are not considered available by the ICZN. To avoid ambiguity, the new biological name is not included in this preprint, and the holotype specimen number CPAP 3054 is used as a placeholder. Paratypes described in this preprint are also used in the diagnosis.