The Criollo (in Spanish), or Crioulo (in Portuguese), is the native horse of Uruguay (1910), Argentina (1918), Brazil (1932) and Paraguay. It may have the best endurance of any horse breed in the world next to the Arabian. In fact, due to the criollo's low basal metabolism, it may be a better long-distance horse than the Arabian in prolonged races over a week in duration with no supplemental feed. The breed, known for its hardiness and stamina, is most popular in its home countries. (source)