An isolated skull from Las Hoyas (Early Cretaceous, Spain) informs the early evolution towards elongated rostra in enantiornithine birds (Aves, Ornithothoraces)

The fossil record of Early Cretaceous enantiornithine birds from the Iberian Peninsula is the most significant in the world outside of China. Despite its historical relevance, taxonomic diversity, and relative abundance, adult cranial remains had not been reported before. In this study, we describe a new enantiornithine species, Gorgonavis alcyone gen. et sp. nov. based on a disarticulated skull from the Early Cretaceous locality of Las Hoyas (129–126 Myr; Cuenca, Spain), the first adult cranial remains of a bird from this fossil site. Digital imaging of the µCT-scanned fossil remains shows that Gorgonavis is characterized by a slender and elongated rostrum in which teeth are restricted to the premaxillary corpus, a thin, edentulous maxilla, and a jugal bone with an elongated and strongly angled postorbital process. Despite the fragmentary nature of the holotype, comparative anatomy and phylogenetic analyses suggest the identification of the new species as a longipterygid, a distinct clade of Enantiornithes characterised by an elongated rostrum, a cranial configuration consistent with the new fossil. Gorgonavis represents the oldest occurrence of an enantiornithine with relative rostral elongation outside of the Jehol Biota. The new discovery suggests that some specialised early enantiornithine lineages had a broader geographical, and more ecologically diverse distribution than previously thought.