New theropod dinosaur from the Upper Cretaceous of Patagonia sheds light on the paravian radiation in Gondwana

MOTTA, MATÍAS J.; AGNOLÍN, FEDERICO L.; BRISSÓN EGLI, FEDERICO; NOVAS, FERNANDO E.

NATURWISSENSCHAFTEN

SPRINGER

Año: 2020 vol. 107

0028-1042

The fossil record of basal paravians in Gondwana is still poorly known, being limited to the Cretaceous unenlagiids from SouthAmerica and the problematic Rahonavis from Madagascar. Here we report on a new paravian from the Cenomanian-Turonian(Late Cretaceous) of Río Negro province, NW Patagonia, Argentina. The new taxon exhibits a derived bird-like morphology ofthe forelimbs (e.g., robust ulna with prominent, anteriorly oriented, and proximally saddle-shaped radial cotyle and wide medialflange on metacarpal I) and a plesiomorphic foot with a raptorial pedal digit II. Phylogenetic analysis recovers the new taxon in amonophyletic clade with Rahonavis, being the sister group of the remaining Avialae and more derived than other non-aviandinosaurs. Both exhibit derived forelimb traits in opposition with their plesiomorphic hind limbs. The position of the new taxonand Rahonavis as stem avialans indicates that Gondwanan basal paravians are represented by two different clades, at least. Thenew taxon probably constitutes a previously unknown grade in the avian-line theropods in which some flight-related adaptationsof the forelimbs are present in cursorial taxa. The present discovery sheds light on the acquisition of flight-related traits in nonaviandinosaurs and on the still poorly known paravian radiation in Gondwana.