Zulma Gasparini, Luis Spalletti, Marta Fernandez, and Marcelo de la Fuente
Tithonian marine reptiles form the Neuquen Basin; diversity and paleoenvironments (in Simposio "Jurasico Superior de America del Sur"
Symposium on Upper Jurassic of South America, Parent,)
Revue de Paleobiologie (1999), 18(1):335-345

Abstract:
The Neuquen Basin is the only region in the Eastern Pacific in which Tithonian marine reptiles have been found. This basin is a back-arc depression, with an excellent record of Jurassic and Cretaceous sedimentites. It is a unique natural laboratory to study marine ramp facies generated under diverse paleoenvironmental conditions. The Tithonian marine reptiles come mostly from off-shore facies, characterized by mainly anoxic accumulation conditions. Unlike the coeval records of the European Tethys, one of the most interesting points of the Tithonian marine herpetofauna of the Neuquen Basin is the taxonomic diversity, tand the dominance of pelagic forms. Based on the groups recorded in the Neuquen Basin, and those absent in Western Europe, it has been proposed that towards the end of the Jurassic large extinctions occurred, particularly those of pelagic groups. However, such a diverse herpetofauna in the Neuquen Basin is far from supporting global extinctions. Ichthyosaurs, numericall dominant, are represented by two genera of a single family (Opthalmosaurus and Capullisaurus); Pliosauroidea plesiosaurs, by two genera (Pliosaurus and Liopleurodon); metriorhynchid crocodiles, by three genera (Metriorhynchus, Dakosaurus and Geosaurus); and turtles, by two genera (Notoemys and Neusticemys) of two different infraorders. According to the available information, the taxonomic decrease of the Late Jurassic reptiles of the EUropean Tethys, and the dominance of coastal forms are related to regional shallowing processes. On the contrary, in the Neuquen Basin, the reptiles are mostly pelagic, some of them giant and in the top of the food chain (e.g. Liopleurodon), which is in accordance with a pick of biodiversity of the Tithonian invertebrates, and a relative high sea-level in thses areas.