New enantiornithine bird from the Late Cretaceous of NW Argentina

FERNANDO EMILIO NOVAS; FEDERICO LISANDRO AGNOLIN; CARLOS AGUSTÍN SCANFERLA

Trelew

Jornada; Jornadas Argentinas de Paleontología de Vertebrados; 2007

Enantiornithes was a diverse group of birds that inhabited inland, marine and literal environments during the Cretaceous, becoming extinct at the Cretaceous-Tertiary boundary. Geographically, they were distributed worldwide with the exception of Antarctica. In South America, the fossil record of Enantiornithes is mainly restricted to Argentina, which yielded five different taxa (i.e., Neuquenornis volans Chiappe and Calvo, Enantiornis leali Walker. Soroavisaurus australis Chiappe., Lectavis breticola Chiappe, and Yuingavolucris brevipedalis Chiappe), We add to this list a new enantiomithine the size of a sparrow, found in beds of Upper Cretaceous Las Curtiembres Formation (Campanian), NW Argentina. These beds yielded hundred of specimens of the small pipid frog Saltenia ibanezi Baez, but recent field explorations resulted in the discovery of a more complete fauna also integrated by teleostean fishes, podocnemidid pleurodirans, mesoeucrocodylian crocodiles, and fragmentary bones of theropod and sauropod dinosaurs. The new enantiomithine is represented by a partial hindlimb (MAS-IV2 I: Museo de Antropologia. Salta) showing adaptations for a perching mode of life (e g., curved claws, digit I fully opposable and bearing an enlarged ungual, penultimate pedal phalanges enlarged). In particular, digit I of the new enantiorniihine is proportionally more strongly built than in other members of this avian group. The new taxon is referred to the enantiomithine family Avisauridae based on the presence of a cranially convex metatarsal III. The new taxon represents the smallest Enantiornithes yet discovered in South America.