PALEOFLORA FROM THE LOS RASTROS FORMATION (MIDDLE TRIASSIC), SAN JUAN PROVINCE, ARGENTINA. TAXONOMIC AND TAPHONOMIC CONSIDERATIONS. The taxonomy and taphonomy of the paleoflora from the Los Rastros Formation (Middle Triassic) San Juan Province, Argentina, is described. The taphofloristic analysis is made considering five fosiliferous levels of sections from Quebrada Agua de la Peña and Quebrada del León. The described taxa belong to the Orders Equisetales, Osmundales, Corystospermales, Peltaspermales, Ginkgoales, Coniferales, and to the Pteridophylla group (incertae sedis leaves). Thirty one taxa are described, 19 of them recorded for the first time for the formation. Generic and specific diversity as well as taphonomic attributes were observed at the different beds studied thus allowing to characterize the depositional environment and the paleofloristic composition. The Los Rastros Formation is composed of several successive cycles of black shales, mudstones and sandstones, corresponding to a lacustrine-deltaic environment, with autochtonous and allochtonous plant remains originated in marginal and upstream areas of this fluvial system.