Macrauchenia ("long llama", based on the now-invalid llama genus, "Auchenia", from Greek "big neck") was a large, long-necked and long-limbed, three-toed native South American mammal in the order Litopterna. The genus gives its name to its family, the Macraucheniidae or "robust litopterns". Like other litopterns, it is most closely related to the odd-toed ungulates (Perissodactyla), from which litopterns diverged approximately 66 million years ago. The oldest fossils in the genus date to the late Miocene, around seven million years ago, and "M. patachonica" disappears from the fossil record during the late Pleistocene, around 20,000-10,000 years ago. "M. patachonica" is one of the last and best known member of the family and is known primarily from the Luján Formation in Argentina, but is known from localities across southern South America. Another genus of macraucheniid "Xenorhinotherium" was present in northeast Brazil and Venezuela during the Late Pleistocene. The type specimen was discovered by Charles Darwin during the voyage of the "Beagle". In life, "Macrauchenia" may have resembled a humpless camel, though the two taxa are not closely related. It fed on plants in a variety of environments across what is now South America. Among the species described, "M. patachonica" and "M. ullomensis" are considered valid; "M. boliviensis" is considered a nomen dubium; and "M. antiqua" (or "M. antiquus") has been moved to the genus "Promacrauchenia".