ON THE PRESENCE OF A PUTATIVE ORNITHURAE (AVES) IN THE LATE MAASTRICHTIAN VERTEBRATE FAUNAS FROM SOUTHERN PYRENEES (SPAIN)

EDUARDO PUÉRTOLAS-PASCUAL; JOSÉ MANUEL GASCA; PÉREZ-PUEYO, M.; PENÉLOPE CRUZADO CABALLERO; MIGUEL MORENO-AZANZA; JOSÉ IGNACIO CANUDO

Congreso; 79th Annual Meeting SVP; 2019

Remains of Late Cretaceous birds are scarce, especially in the Maastrichtian of Europe. Up to now, just some Enantiornithes (e.g. Martinavis cruzyensis) and Ornithurae remains have been recovered. In this context, one of the most remarkably remains corresponds to the giant bird Gargantuavis philoinos from the early Maastrichtian of France, unfortunately its phylogenetic position within Aves remains unknown. Here we present a cervical vertebra (MPZ 2019/264) belonging to a large-sized bird recovered from the upper Maastrichtian fossil locality ?Dolor 3? (Tremp Fm), near the village of Serraduy within the Tremp Basin in the Pyrenean range (Huesca, Spain). The Tremp Fm deposits from this area have been dated by magnetostratigraphy and biostratigraphy as belonging to the Chron C29r. Therefore MPZ 2019/264 is one of the youngest Mesozoic Aves of Europe, very close to the Cretaceous/Paleogene boundary (K/Pg), and the first report of this clade in the Tremp Basin. MPZ 2019/264 is an almost complete cervical vertebra just lacking the posterior articular face. The morphology of the anterior section of the vertebral centrum, which is concave transversely and convex dorsoventrally, confirms an advanced heterocoelous condition. In addition, a micro-CT analysis showed a very strong vertebral pneumatization with camellate internal structure. MPZ 2019/264 also bears two lateral pneumatic foramina in the neural arch and another one in the centrum. These foramina, along with a low and anteroposteriorly elongated neural spine and the arrow-shaped section of the centrum, differentiate MPZ 2019/264 from the cervical vertebra of Gargantuavis from Montplo-Nord (France). A cladistic analysis using a dataset comprising 23 ornithuromorphs, 29 enantiornithes and 8 basal avians, recovers both Gargantuavis and MPZ 2019/264 as Ornithuromorpha. When Gargantuavis is not included in the analysis, MPZ 2019/264 is recovered as member of Ornithurae. Nevertheless, these results have to be considered with caution, as the fragmentary condition of both Gargantuavis and MPZ 2019/264, and the lack of preserved unambiguous synapomorphies in the later hinders further taxonomic attribution.