Sierra de las Quijadas National Park is in Argentina. It has a great archaeological, prehistorically and ethnographic value and evidence a close relationship and regional integration with the Ischigualasto and Tamlampaya National Parks. It undoubtedly constitutes a "sanctuary" of the flora and fauna of the Province of San Luis and of the west-central part of Argentina, since its environment constitutes a transition strip or "ecotone" between the biogeographical provinces of Chaco and Monte. Furthermore, this National Park is the only protected area for the preservation of this type of ecosystem. The Chaco province is characterized by thick profuse forests with outstanding high size species such as Prosopis flexuosa and Aspidoderma quebrucho-blanco and the Monte province exhibits sparse and low xerophilous forests, with predominance of the Larrea genus, especially cunefilia. Surrounding this area, there is a strip of land with new shoots of tamarisco (Tamarix gulltcu), an exotic wildened species. The vascular flora is formed by 206 specific and infraspecific taxons, distributed into 45 families, Ptedirophytes and Pinophytes resent only 3 taxons, while liliopsida, with 45 taxons, and Magnoliopsidae, with 158 taxons, are the main families. The best-represented families are Poaceae, Asteraceae, Fabaceae and Soianaceae. The regional endemisms detected are 62 taxons representing 30% of the total, along with 3 species new for science, Sclerophylux dfulvioi, A~iplaquizadensis and Senecio hualfaranensis. Thus, the park can be considered an important genetic reservoir of the west-central flora of Argentina. The fauna of sierra de las Quijadas corresponds to the Neotropical zoogeographical region, Andean-Palagonian subregion, Central Domain. It is mainly of the Brasilic type and Subtropical and Chaco filiation, selected under rigorous ecological conditions, but with a marked Patagonian influence. Reptiles: the presence of 40 species in the National Park, three of which are in seriously endangered, has been reported. Ampihibians: the area corresponds to the Chaco batrachfauna of the Monte or Temperate district. Of the 14 species identified, one is in CITES 11, one is vulnerable and one is endangered. Birds: Some authors have reported approximately 140 species in the area, 80 of which belong to non-passeriforms and the remaining ones to passeriforms. However, 189 species have already been identified the National Park, two of which are endemic and ten are under some degree of endangerment. Mammals: the Sierra de las Quiadas National Park belongs to the mastozoogeographical region of the Neotropical Region, Chilean Subregion, Andean Domain, SubAndean Province. Eighteen species have been reported, with approximately 47 species remaining to be confirmed. Among the confirmed species, 11 exhibit some degree of endangerment.