Macrauchenia was a large, long-necked hoofed mammal of South America, shaped something like a camel but related to neither camels nor llamas. It lived across the south of the continent from about 400 000 to about 12 000 years ago, and it was one of the last litopterns, an order with no living members. Darwin dug up the first bones, and its true place among mammals was settled only in the last decade or so, with the help of ancient proteins and DNA.
A Mastodon that was not
Darwin found the first bones in January 1834 at Port St Julian in southern Patagonia, while the Beagle was surveying the coast. Writing to Henslow that March, he called them “some large animal, I fancy a Mastodon”. Back in England, Owen saw in the leg bones and vertebrae a giant resembling a llama or camel, and in 1838 named it Macrauchenia patachonica, roughly “long llama”.
One old error lasted far longer. In 2023 Püschel and Martinelli described the real atlas, the first neck vertebra, for the first time. The bone published under that label 159 years earlier by Burmeister probably came from a bovid, and later researchers had simply not gone back to it, although most mounted skeletons carry a correct atlas taken from a more complete specimen found by Roth around 1904.
The nose question
The strangest thing about the skull is where the nose opens: on top, between the eye sockets, with a sunken area behind it covered in pits and ridges for nasal muscles. This was long taken as a sign of a trunk like a tapir’s, and a 1913 restoration by Horsfall went further and gave it one like an elephant’s. That is now seen as out of date. Recent authors doubt even the tapir-like trunk. They suggest a grasping lip like a moose’s, a nose like a saiga antelope’s for filtering dust in its dry, open habitat, or something that did both. The skull shows that muscles worked a fleshy nose, but not what shape it took.
Cousins of horses, by a long road
A firm answer on its relationships came in 2015, when Welker and colleagues read collagen proteins from Macrauchenia and Toxodon, another South American hoofed mammal. The two formed one group, whose closest living relatives are horses, tapirs and rhinoceroses. In 2017 Westbury and colleagues recovered mitochondrial DNA from a foot bone found in Baño Nuevo-1 Cave in Chile. It supported the link and put the split at about 66 million years ago, with an uncertainty of 56.64 to 77.83 million.
A tonne, more or less, built to swerve
Weight estimates differ with the method. Fariña and colleagues used 1 100 kg in 2005, Blanco and colleagues gave about 1 tonne in 2021, and in 2026 Lobo, Gelfo and de Azevedo ran 162 estimates from ten specimens and reached a median of 734 kg. They also found that the family grew steadily heavier over 30 million years, from an ancestor of about 43 kg.
Footprints suggest it walked up on its toes, and its build was that of a fast runner. Fariña’s team noticed that its thigh bone was much stronger from side to side than from front to back, a pattern seen in living animals that escape by dodging, and proposed that it survived attacks by Smilodon by swerving. Isotope studies suggest Smilodon populator ate it regularly. Modelling of the neck joints in 2023 found that an upright neck fitted best when standing or feeding, and an almost horizontal one at speed. At least three individuals preserved together at Kamac Mayu in Chile hint that it lived in herds.
Few traces of the hunters
Macrauchenia disappeared about 12 000 years ago, some time after people reached South America, which they had done at least 14 500 years ago. Direct evidence of contact is thin. A lower jaw collected in the Pampas in the 19th century, now in Paris, may carry butchery marks. At Arroyo Seco 2 its bones lie among human artefacts but show no cut marks, and at Paso Otero 5 they were burned beside Fishtail spear points, probably as fuel. Hunting and climate change remain the two main explanations for its end.
