Sierra de las Quijadas

The red sandstone amphitheatre of Sierra de las Quijadas was a Cretaceous lakebed a hundred million years ago, and the creatures of its shores are still in the rock — most famously Pterodaustro, a filter-feeding pterosaur whose flamingo-like life was reconstructed from the fossils this formation keeps yielding. Erosion has opened the old lakebed into canyons, arches and badlands above a plain of cardón and quebracho.

The park protects over 70,000 hectares of the Lagarcito Formation in northwestern San Luis — a pterosaur ground nearly unmatched in South America, with Pterodaustro specimens recovered by the hundred and fossils still embedded in the sandstone where rangers can point them out. The central bowl at Potrero de la Aguada spreads kilometres of red rock that turns purple as the afternoon leans, reachable by a self-guided rim walk from the entrance side, while the fossil grounds themselves open only on ranger-guided walks booked at the station. Flash floods built this landscape and still own it — dry riverbeds pass in the rainless months and seal off when storms come. Pumas, guanacos and Chacoan armadillos work the dry monte in visitor densities low enough that wildlife encounters are probability, not luck.