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de Valais S.,National University of Rio Negro | Apesteguia S.,Maimonides University | Garrido A.C.,Museo Provincial de Ciencias Naturales Prof. Dr. Juan A. Olsacher
PLoS ONE | Year: 2012

Ecological relationships among fossil vertebrate groups are interpreted based on evidence of modification features and paleopathologies on fossil bones. Here we describe an ichnological assemblage composed of trace fossils on reptile bones, mainly sphenodontids, crocodyliforms and maniraptoran theropods. They all come from La Buitrera, an early Late Cretaceous locality in the Candeleros Formation of northwestern Patagonia, Argentina. This locality is significant because of the abundance of small to medium-sized vertebrates. The abundant ichnological record includes traces on bones, most of them attributable to tetrapods. These latter traces include tooth marks that provde evidence of feeding activities made during the sub-aerial exposure of tetrapod carcasses. Other traces are attributable to arthropods or roots. The totality of evidence provides an uncommon insight into paleoecological aspects of a Late Cretaceous southern ecosystem. © 2012 de Valais et al.

Gasparini Z.,National University of La Plata | Gasparini Z.,CONICET | Fernandez M.S.,National University of La Plata | Fernandez M.S.,CONICET | And 7 more authors.
Ameghiniana | Year: 2015

The lithographic limestones of the Los Catutos Member (Vaca Muerta Formation, Neuquén Province, Argentina) (late middle-early late Tithonian) bear a great diversity of marine reptiles. These deposits are unique in the Southern Hemisphere as the record of lithographic limestones from the Upper Jurassic is restricted to the Northern Hemisphere, particularly to Western Europe. Some European basins are very close in age (late Kimmeridgian-early Tithonian) but they do not reach the middle-late Tithonian. Additionally, in the European basins the marine reptiles are mixed with continental biota whereas in Los Catutos Member the biota is exclusively marine, with the pterosaurs being the only exception. The strictly marine biota is composed by ichthyosaurs, two different species of turtles, one crocodyliform, and one plesiosaur. The taxonomic composition of Los Catutos Member is very similar to that found in Cerro Lotena (Portada Covunco Member, middle Tithonian) (Vaca Muerta Formation). These members share the same turtle species and one metriorhynchid genus, while ichthyosaurs only coincide at a family level. The study of marine reptiles from the Los Catutos Member, along with studies from other localities of the Neuquén Basin, have made an important contribution in filling the gaps in the evolutionary history of each of the represented clades. In this regard, they represent the only known marine reptiles from Gondwana throughout the Jurassic/Cretaceous transition, which is poorly represented in other regions of the world.

Codorniu L.,National University of San Luis | Garrido A.,Museo Provincial de Ciencias Naturales Prof. Dr. Juan A. Olsacher
Journal of South American Earth Sciences | Year: 2013

Discoveries of Jurassic pterosaurs in the Southern Hemisphere are extremely unusual. In Argentina, pterosaurs from the Upper Jurassic (Tithonian) have only been found in the Northwest of Patagonia (Neuquén Basin). These come from marine deposits and three specimens have been discovered up to the present. In this paper, we report a new finding from the Neuquén Basin. This material is identified as a tibiotarsus, which probably belonged to an osteologically adult individual and represents a new species of a pterodactyloid pterosaur of medium size. This discovery provides new evidence that at least two different species of pterodactyloid pterosaurs may have coexisted in Los Catutos Member, Vaca Muerta Formation, from the shallow marine deposits of the Neuquén Basin. © 2013 Elsevier Ltd.

The Neuquén Group conform a succession of non-marine deposits of fluvial, aeolian and shallow lacustrine origin, developed in the Neuquén Basin between the Lower Cenomanian and the Middle Campanian (Upper Cretaceous). This succession reaches 1,200 m of maximum thick, being bounded at the base and the top by the Patagonidican and Huantraiquican unconformities respectively. In this paper two new formations are proposed (Los Bastos and Sierra Barrosa Formations, nom. nov.), and the subgroups were reconfigurated. Consequently, the Neuquén Group is composed lithostratigraphically by three subgroups and nine formations. The Río Limay Subgroup comprehend the Candeleros and Huincul Formations, representing low sinuosity channel deposits developed under tectonic and climatic subordinated control. The Río Neuquén Subgroup comprehend to the Cerro Lisandro, Portezuelo, Los Bastos, Sierra Barrosa and Plottier Formations, conforming a psamitic and pelitic interstratified succession of fluvial origin, mainly developed under climatic control. Finally, the Río Colorado Subgroup integrated by the Bajo de la Carpa and Anacleto Formations, comprehend fluvial deposits developed under a new dominant tectonic control. At the start of the deposition of the Neuquén Group, the Dorsal de Huincul worked as a structural high, generating toward the south of the Neuquén Basin one a small endorreic depocentre corresponding to the Picún Leufú Sub-basin, scheme that would have been keep up to ends of the deposit of the Candeleros Formation. During the rest of the deposit of this sequence, the drainage would have been kept without major modifications towards the pacific slope across a central collector flowing in sense N-NW. Towards the end of the deposit of the Neuquén Group takes place the inversion of the regional slope of the basin, making possible the ingression of the Atlantic Ocean and the beginning of the deposition of the Malargüe Group.

Garrido A.C.,Museo Provincial de Ciencias Naturales Prof. Dr. Juan A. Olsacher
Ameghiniana | Year: 2010

Outcrops of Anacleto Formation at Auca Mahuevo nesting site (Neuquén Province, Argentina) can be divided into two main sections. The lower section(51 m), exhibits a succession of point bar, levee, crevasse channel and crevasse splay deposits, typifing a fine-grained, mixed load meandering fluvial system. Twenty five km toward south (Los Barreales locality) these diposits become progressively to distal floodplain facies. Egg-layers are exposed along this 25 km, however a higher concentration of egg-clutches occur into paleosols and abanndoned channnel deposits developed at ancient levee and meander belt areas. Lithofacial evidences allow attributing for this lower section semiarid climatic condition, with marked alternations of wet and dry seasons. Exceptional muddy sheet-floods burying the eggs annd nests with a thick bed of mud, facilitating their preservation. The upper section (17 m), is composed by finer sediments of sloughs and lacustrine deposits developed over a poorly draiined floodplain, under conditions of major aridity. South toward Los Barreales, evaporitic deposits was formed in saline-lakes. The tectonnic and volcannic processes that affected the basin from the middle to uper Campanian were responsible for the variations in the environmental conditions during the latest phase of the Anacleto Formation deposition. Possibly, these changes provoked the abandonment of this area as nesting-ground. © Asociación Paleontológica Argentina.

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