First record of a giant bird (Ornithuromorpha) from the uppermost Maastrichtian of the Southern Pyrenees, northeast Spain

Throughout the evolutionary history of Avialae, several members of this clade have evolved into giant forms, in different time periods and ecological contexts. In Europe, the first birds that show this condition, the Gargantuaviidae, occur during the Late Cretaceous (late Campanian–early Maastrichtian), but it is during the Paleogene when more groups evolve large forms. However, until now, there was no record of any giant bird during the late Maastrichtian of Europe, close to the K/Pg boundary. Here we describe a cervical vertebra (MPZ 2019/264) from Beranuy (Huesca, NE Spain), which is the first fossil evidence of a giant bird from the late Maastrichtian of Europe, within Chron C29r. The vertebra displays some features, such as a well-marked heterocoelous articulation, lateral pneumatic foramina, ventral carotid processes, and a low neural spine, that support its inclusion within the clade Ornithuromorpha. This phylogenetic assignment is supported by two cladistic analyses. The vertebra is clearly different from the one assigned to <i>Gargantuavis</i>, meaning that it belonged to a distinct taxon. Although the kinship between these two taxa of giant birds is still unclear, this finding demonstrates that large-sized birds were part of the ecological communities of the Ibero-Armorican island from the late Campanian to the Late Maastrichtian, being present during the last hundreds of thousands of years prior to the K/Pg extinction event.