Taphonomic analysis of Thanatosdrakon amaru (Pterodactyloidea: Azhdarchoidea) and paleoenvironmental reconstruction of the Plottier Formation (Upper Cretaceous, Neuquén Basin), Mendoza, Argentina

Abstract

The fossil remains of Thanatosdrakon from the Plottier Formation (PS-3 quarry, Mendoza, Argentina) offer a unique opportunity to investigate the preservation of pterosaurs in fluvial environments. The objective of this study is to reconstruct the taphonomic history of the holotype (UNCUYO-LD 307) and paratype (UNCUYO-LD 350). Detailed stratigraphic analysis together with taphonomic attributes allowed defining that the specimens were preserved with a variable drainage floodplain taphonomic mode (VDF-BA). Distinct taphonomic submodes were defined for each specimen, reflecting differences in biostratinomic and fosildiagenetic processes. The holotype, which was discovered in reddish pelites interpreted as floodplain deposits, exhibits associated skeletal elements suggesting rapid burial. In contrast, the paratype, composed of only one humerus, exhibits evidence of prolonged subaerial exposure, which is evidence that it was exposed to different paleoenvironmental conditions. These findings underscore the variable preservation pathways within the same depositional setting and highlight the influence of both rapid burial and prolonged exposure on the fragile skeletons of large pterosaurs. The taphonomic submodes that have been defined contribute valuable insights into the taphonomic biases that have shaped the pterosaur fossil record in the Cretaceous Patagonian basins.