Tetrapod association and paleoenvironment of Los Colorados Formation (Argentina): a significant sample from western Gondwana at the end of the Triassic.

ARCUCCI, A. B., MARSICANO, C. A. Y CASELLI, A. T.

GEOBIOS

ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER

Lugar: Paris; Año: 2004 p. 557 - 568

0016-6995

- Los Colorados Formation constitutes a continuous continental sucession deposited in Western Argentina during the Late Triassic, a time period that is crucial to the record of the faunistic turnover at the Triassic-Jurassic boundary. Many authors have pointed out that its rich tetrapod fauna represents a unique transitional assemblage with elements typical of both Late Triassic and Early Jurassic. However, the possibility that the fauna represented a mixure of Triassic and Jurassic horizons was also proposed. Recently, stratigraphic control of the fossiliferous levels in order to correlate the different localities of the extense Los Colorados outcrops was developed, and a revision of the taxonomic status of most tetrapods recovered is currently undergoing. Preliminary results confirms previous assumptions about the transitional nature of the assemblage where typical Triassic taxa are in association with dinosaur groups known from Early Jurassic levels in other gondwanan areas. The fossiliferous levels of the upper third of the sequence includes several basal archosaurs (aetosaurs, sphenosuchians, proterosuchians), derived dinosaurs (sauropodomorphs, tetanuran teropods) and primitive chelonians.