Nicolás Foix

TAFONOMÍA DEL DINOSAURIO TERÓPODO ANIKSOSAURUS DARWINI, FORMACIÓN BAJO BARREAL, CRETÁCICO TARDÍO DE PATAGONIA (ARGENTINA)

Abstract. TAPHONOMY OF THE THEROPOD DINOSAUR ANIKSOSAURUS DARWINI, BAJO BARREAL FORMATION, LATE CRETACEOUS OF PATAGONIA (ARGENTINA). Aniksosaurus darwini is a coelurosaurian theropod from the Bajo Barreal Formation (Upper Cretaceous), south of Chubut Province, Patagonia, Argentina. The fossils include postcranial remains of 5 individuals and they were preserved in a overbank mantle deposit associated to a low-sinuosity fluvial system. A detailed analysis on the biostratinomic, fossildiagenetic, and paleoenvironmental aspects of the site of occurrence of Aniksosaurus allows us to recognize two meteorization stages and their possible association with the origin of accumulation of the skeletons. Moreover, tooth marks in one of the femora are preliminarily assigned to a small crocodyliform. The taphonomic study adds new anatomic evidence related to soft tissues. The holotype, MDT-Pv 1/48, is represented by an articulated right hindlimb including, femur, tibia, metatarsals and phalanges. The subaerial weathering and abrasion of the femur due to transport strongly contrast with the preservation of the rest of the hindlimb bones, suggesting the presence of a protecting soft tissue resembling the podoteca seen in extant birds. The presence of this soft tissue in Aniksosaurus, could support the early occurrence of this feature in basal coelurosaurians.

First Report of a Maastrichtian Palynoflora from the Golfo San Jorge Basin, Central Patagonia, Argentina

Abstract. This paper reports on the biostratigraphic, paleobiogeographic and paleoecologic aspects of palynoflora recovered from sedimentary rocks preliminarily assigned to the Lago Colhué Huapi Formation, in the Golfo San Jorge Basin. The present palynological assemblage includes Maastrichtian marker species of the austral Proteacidites/Nothofagidites Province such as Quadraplanus brossus and Tubulifloridites lilliei. Typical species of the Maastrichtian paleotropical Palmae Province, Buttinia andreevi and Gabonisporis vigourouxii, are also recognized in the palynoflora. These facts indicate the mixed character of the paleoflora and the prevalence of transitional climatic conditions at the paleolatitude of the Chubut Province in the uppermost Cretaceous. The palynoflora composition suggests the local existence of a warm and low energy freshwater body.