Marine reptiles from the Jurassic/Cretaceous transition at the High Andes, Mendoza, Argentina

Abstract

Upper Jurassic and Lower Cretaceous deposits of the Vaca Muerta Formation (Neuquén Basin, central-west Argentina) have yielded abundant marine reptile remains. Most of them correspond to faunal assemblages recovered from outcrops in the Neuquén Province (Argentina). Herein we report two new marine reptile-bearing localities documenting the Tithonian–Berriasian transition at the High Andes (Mendoza Province, Argentina). Marine reptiles have been mapped and/or collected in connection with an accurate ammonoid-based biostratigraphic control. All the skeletons have been found preserved in, or associated with, calcareous nodules. At both localities they are frequent in beds assigned to the upper Tithonian Corongoceras alternans ammonite Zone (Microcanthum to “Durangites” Standard Zones), and are rare to common in beds assigned to the upper Tithonian–lower Berriasian Substeueroceras koeneni Zone (“Durangites” to Jacobi Standard Zones). Newly discovered assemblages depict a similar pattern characterized by the lack of plesiosaurs (plesiosauroids and pliosaurids), and by the abundance of mesoconsumers represented by ophthalmosaurids and metriorhynchine metriorhynchids. Macropredator geosaurines, apex metriorhynchids predators, and thalassochelydian turtles are rare components of these assemblages.