Tafonomía del Dinosaurio Terópodo aniksosaurusdarwini, Formación Bajo barreal, Cretácico Tardío de Patagonia (Argentina)

Abstract

Aniksosaurus darwini is a coelurosaurian theropod from the Bajo Barreal Formation (Upper Cretaceous), south of Chubut Province, Paragonia, Argentina. The fossils include postcraniaI 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.