Macrauchenia

Macrauchenia Temporal range: Middle Pleistocene – Late Pleistocene PreꞒ Ꞓ O S D C P T J K Pg N ↓
Skeleton of M. patachonica (larger) and Phenacodus primaevus (smaller) at American Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Litopterna
Family:	†Macraucheniidae
Subfamily:	†Macraucheniinae
Genus:	†Macrauchenia Owen, 1838
Type species
†Macrauchenia patachonica Owen, 1838
Map showing the distribution of Macrauchenia in red, and Xenorhinotherium in yellow, inferred from fossil finds

Macrauchenia ("long llama", based on the now-invalid llama genus, Auchenia, from Greek "big neck") is an extinct genus of large ungulate native to South America from the Pliocene^[1] or Middle Pleistocene to the end of the Late Pleistocene.^[2] It is a member of the extinct order Litopterna, a group of South American native ungulates distinct from the two orders which contain all living ungulates which had been present in South America since the early Cenozoic, over 60 million years ago, prior to the arrival of living ungulates in South America around 2.5 million years ago as part of the Great American Interchange.^[3] The bodyform of Macrauchenia has been described as similar to a camel,^[4] being one of the largest-known litopterns, with an estimated body mass of around 1 tonne.^[3] The genus gives its name to its family, Macraucheniidae, which like Macrauchenia typically had long necks and three-toed feet, as well as a retracted nasal region,^[5] which in Macrauchenia manifests as the nasal opening being on the top of the skull between the eye sockets.^[6] This has historically been argued to correspond to the presence of a tapir-like proboscis, though recent authors suggest a moose-like prehensile lip^[7] or a saiga antelope-like nose to filter dust are more likely.

Only one species is generally considered valid,^[8] M. patachonica, which was described by Richard Owen based on remains discovered by Charles Darwin during the voyage of the Beagle.^[9] M. patachonica is primarily known from localities in the Pampas, but is known from remains found across the Southern Cone extending as far south as southernmost Patagonia, and as far north as Southern Peru. Another genus of macraucheniid Xenorhinotherium was present in northeast Brazil and Venezuela during the Late Pleistocene.^[6]

Macrauchenia is thought to have been a mixed feeder that both consumed woody vegetation and grass that lived in herds and probably engaged in seasonal migrations. Macrauchenia is suggested to have been a swift runner that was capable of moving at considerable speed.

Macrauchenia became extinct as part of the end-Pleistocene extinction event around 12,000 years ago, along with the vast majority of other large mammals native to the Americas.^[3] This followed the arrival of humans to the Americas, and possible evidence of human interactions with Macrauchenia has been found at a number of sites with some authors suggesting human hunting may have played a role in its extinction.