Reptiles from lithographic limestones of the Los Catutos Member (Middle-Upper Tithonian), Neuquén Province, Argentina: An essay on its taxonomic composition and preservation in an environmental and geographic context

Abstract

The lithographic limestones of Los Catutos Member (Vaca Muerta Formation, Neuquén province, Argentina) (late middle-early upper Tithonian) bear a great diversity of marine reptiles. These lithographic limestones are significant because they are the unique in the Southern Hemisphere since the record of lithographic limestones from Upper Jurassic is restricted to the Northern Hemisphere, particularly Western Europe. Some European basins are the most closely in age (upper Kimmeridgian-lower Tithonian) but they do not reach the upper?middle Tithonian. Also, in the European basins the marine reptiles are mixed with continental biota whereas in Los Catutos Member the biota is exclusively marine, being the only exception the pterosaurs. The strictly marine biota is composed by ichthyosaurus, two different clades of turtles, one crocodyliform and one plesiosaur. This taxonomic composition presents closest taxonomic affinities with that found in Cerro Lotena (middle Tithonian) of the same formation. These localities share the same turtle species and one metriorhynchid genus; ichthyosaurs only coincide in the family Ophthalmosauridae. The knowledge resulting from the studies of marine reptiles of the Los Catutos Member, as well as those found in other localities of the Neuquén Basin, contributed to reduce the gap of information on the evolution of the clades. On this regard, they are the only ones known from Gondwana and are particularly significant because they are completing the Jurassic/Cretaceous transition, scarcely represented in the world record.