A new enantiornithine bird from the Late Cretaceous of the Gobi Desert

We report on a new species of enantiornithine bird from the Late Cretaceous of the Mongolian Gobi Desert,which adds to the meager record of birds from the latest part of the Mesozoic in this region. The exceptional, three-dimensional bones of the new fossil increase the known anatomical diversity of enantiornithine birds, providing information about previously unreported morphologies such as a pneumatised furcula. Several synapomorphies nest the new bird within an enantiornithine clade of proficient fliers, but the anatomy and proportions of its flight apparatus imply significant aerodynamic restrictions. The combination of phylogeny and our functional interpretation suggests that this new fossil bird is a representative of a flightless lineage. This discovery thus provides the first evidence of a trend towards more limited flying capabilities among Enantiornithes, a group of Cretaceous birds otherwise believed to be represented by competent fliers.