Triassic Dinosaurs and mammalian reptiles from Ischigualasto

The continuous succession of Triassic strata exposed in the park was deposited in an open basin 251 million years ago. The continuous sedimentation allowed for a comprehensive record in that environment of the evolution of primitive turtles and the replacement of therapsids by archosaurs during the Early Triassic (Benton, 1993). Moreover, fossils of the oldest and most primitive dinosaurs known to date (Sereno and Novas, 1992) occur in the Upper Triassic along with therapsids, cynodonts and dicynodont types. The latter constitute the category of mammalian reptiles, from which mammals later evolved. The formation of the Andes Mountains uplifted this ancient basin to 1,300 meters above sea level, exposing the rocks to erosion that carved out a particular landscape known as “Valle de la Luna” (Valley of the Moon). The brick red, greenish and ocher sandstones are exposed in cliffs up to 200 meters high where the different strata and their internal structures highlighted by wind abrasion can be distinguished. Gigantic columns, thin obelisks, unusual rock shapes, ravines and gorges complete this spectacular landscape.