Réserve naturelle Pehuen-Có - Monte Hermoso, Natural reserve in southern Buenos Aires Province, Argentina.

Reserva natural Pehuen-Có - Monte Hermoso covers 2,000 hectares of active coastal dunes backed by vegetated dunes, interdune hollows and temporary pools, from Pehuen-Có to Monte Hermoso. Its beaches expose stratified clay and sand layers twice a day with the tides, and the marine water here is among the warmest of the Argentine Sea for its latitude.

The reserve was created on 9 November 2005 by provincial law 13394, and in August 2014 the Chamber of Deputies' culture committee declared it a National Historic Place. Its cliffs at Farola Monte Hermoso expose vertebrate fossils three to five million years old, studied by Charles Darwin in 1832-1833, then by Bravard in 1857 and Florentino Ameghino in 1887. In 1978 Dr. Acuña found a trackway attributed to Scelidotherium, named Acuñaichnus dorregoensis by Rodolfo Casamiquela in 1983.

At "El pisadero", about 6 km from Monte Hermoso, hundreds of human footprints roughly 7,000 years old are recorded in the sediment. "La Olla I", found in 1983 by Vicente Di Martino, and "La Olla II", exposed by shifting sand in 1995, yielded sea lion, guanaco and deer bones, shells, rhea egg fragments, plant remains and stone, bone and decorated wooden tools.

The fossil track sites lie on the beach and are exposed only around low tide, twice a day, so time your visit to the tidal cycle. Playa del Barco is about 1 km from Pehuen-Có and the paleoichnite site about 1 km east of it; Farola Monte Hermoso is 15 km away. The sand and cracked mud are soft and uneven underfoot.

At "El pisadero", about 6 km from Monte Hermoso, hundreds of human footprints were left some 7,000 years ago. Nearby, La Olla I, found in 1983 by Vicente Di Martino, and La Olla II, uncovered by shifting sand in 1995, yielded sea lion, guanaco and deer bones, shells, rhea egg fragments and a decorated wooden object.