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Conchostracans and fish remains front the type locality of the Rio Mendoza formation Middle Triassic, Mendoza province, Argentina Conchostracos y restos de peces de la localidad tipo de la Formacion Rio Mendoza Triasico Medio, provincia de Mendoza, Argentina

Gallego, O.F.; Zavattieri, A.M.; Lopez-Arbarello, A.

Ameghiniana 41: 289-301

2004


ISSN/ISBN: 0002-7014
Accession: 038094138

The present paper includes the first records and descriptions of conchostracans (Euestheria martinsnetoi sp. nov.) and actinopterygian fish remains in Triassic sediments of the Rio Mendoza Formation. All previously known Triassic conchostracans of the Cuyo Basin come from the Cerro de las Cabras, Potrerillos and Cacheuta Formations, or their equivalents. Similarly, fish remains were only known from the Potrerillos, Cacheuta and Santa Clara Abajo Formations. The fossils, also including plant remains, were found in red massive clays in the middle section of the type sequence of the Rio Mendoza Formation, above the initial facies of alluvial fans on the northern slope of cerro Bayo (Potrerillos area, northwestern of Mendoza province). This fauna and flora developed in semipermanent extense water bodies, localized small lakes and/or ponds produced by the overflowing of channels or mudflows in a strongly seasonal fluvial environment in the lowermost parts of the system. The continental red sediments of the basal unit of the Uspallata Group are nowadays considered to be late Middle Triassic in age (equivalent to the "Ladinian" stage of the marine sequences), instead of Early Triassic as was previously thought. According to recent reinterpretations, the stages following the Choiyoi volcanic cycle, which underlies the Rio Mendoza Formation discordantly, would reach to the early Middle Triassic in the Cuyo Basin. Thus, these are the oldest conchostracan and fish records in the Triassic of Argentina.

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