Macrauchenia

***Macrauchenia*** is an extinct genus of mammals from South America from the late Miocene to the late Pleistocene. This bizarre-looking animal was a member of a group of extinct animals called litopterns, only known from South America. No one knows how they were related to other mammals - until more fossils are found they are assumed to be distant relatives of our familiar hoofed animals, hypothesized to be closely related to perissodactyls (odd-toed ungulates). *Macrauchenia* was the last of its kind, its extinction saw the end of the litoptern lineage. The first *Macrauchenia* skeleton was discovered by Charles Darwin on a stop-over during his famous journey on board The Beagle. Since then many more remains have been found in the Lujan formation in Argentina. *Macrauchenia* appeared in the fossil record some 7 million years ago in South America (in the Miocene epoch). It is likely that *Macrauchenia* arose from either *Theosodon* or *Promacrauchenia*.

*Notoungulata* and *Litopterna* were two ancient orders of ungulates which only occurred in South America. Many of these species became extinct through competition with invading North American ungulates during the Great American Interchange, after the establishment of the Central American land bridge. A few survivors of this invasion were the litopterns *Macrauchenia* and *Xenorhinotherium* and the large notungulates *Toxodon* and *Mixotoxodon*. These last original South American hoofed animals died out eventually at the time of the arrival of humans at the end of the Pleistocene, along with numerous other large animals on the American continent that outcompeted it (such as mammoths, horses, camels, and tapirs). As this genus was the last of the litopterns, its extinction ended that line of mammals.

## Taxonomy

*Macrauchenia* was first discovered on 9 February 1834 at Port St Julian in Patagonia (Argentina) by Charles Darwin, when HMS *Beagle* was surveying the port during the voyage of the *Beagle*. As a non-expert he tentatively identified the leg bones and fragments of spine he found as "some large animal, I fancy a Mastodon". In 1837, soon after the *Beagle's* return, the anatomist Richard Owen revealed that the bones including vertebrae from the back an neck were actually from a gigantic creature resembling the Llama and the camel, which Owen named *Macrauchenia patachonica*. In naming it, Owen noted the original Greek terms Μακρος (large or long), and αυχην (neck) as used by Illiger as the basis of *Auchenia* as a generic name for the Llama, Vicugna and so on. The find was one of the discoveries leading to the inception of Darwin's theory. Since then, more *Macrauchenia* fossils have been found, mainly in Patagonia, but also in Bolivia, Chile and Venezuela.

*Macrauchenia* was a member of the litopterns, a group of unusual mammals whose genetic relationships to other mammals was mysterious and unknown. However, recent evidence from genetic testing has shown that litopterns (including *Macrauchenia*) are related to perrisodactyls.

## Description

*Macrauchenia* was a member of the order litopterna, which belonged to very specific South American ungulates. Most of the representatives of litopterns went extinct at the end of the Pliocene, after an overland to North America and the emergence of new predators and competition from new prey. *Macrauchenia* were sufficiently attuned to adapt to survive until the end of the Pleistocene. *M.* patachonica died, apparently, only 10 thousand years ago. *Macrauchenia* was a hoofed mammal with three hoof-like toes. It reached a height of 1.4 m at the shoulders, which corresponds to the modern zebra, and weighed around 270 kg. Long and very strong legs ended in three fingers. The neck was very long, and the front of the snout is likely to end with a proboscis, adapted for plucking leaves, although the structure of the teeth are more like that of a grass eater. Remains were found of *Macrauchenia*, primarily in the southeastern Pampas, but the findings are also known in Venezuela.

Their general appearance resembles to camels and tapir, but recent findings suggest that it maybe have more so resembled horses and moose.

*Macrauchenia* had a somewhat camel-like body, with sturdy legs, a long neck and a relatively small head. Its feet, however, more closely resembled those of a modern rhinoceros, and had three hoofs each. It was a relatively large animal, with a body length of around 3 meters (9.8 ft).

One striking characteristic of *Macrauchenia* is that, unlike most other mammals, the openings for nostrils on its skull were atop the head, leading some early scientists to believe that, much like a whale, it used these nostrils as a form of snorkel. Soon after some more recent findings, this theory was rejected. An alternative theory is that the animal possessed a trunk, perhaps to keep dust out of the nostrils.

One insight into *Macrauchenia'*s habits is that its ankle joints and shin bones may indicate that it was adapted to have unusually good mobility, being able to rapidly change direction when it ran at high speed. It is speculated that since *Macrauchenia* lived in an environment much like the savannas of modern-day Africa, it may have had a tawny coat to match the color of dried grass.

*Macrauchenia* is known, like its relative, *Theosodon*, to have had a full set of 44 teeth.

## Paleobiology

### Diet and behavior

*Macrauchenia* was an herbivore, likely living on leaves from trees or grasses. Scientists believe that, because of the forms of its teeth, it ate using its trunk to grasp leaves and other food. It is also believed that it lived in herds like modern-day wildebeest or antelope, the better to escape predators.

### Predators

When *Macrauchenia* first arose, it would have been preyed upon by the largest of native South American predators, terror birds such as *Andalgalornis*, and carnivorous marsupials such as *Thylacosmilus* and *Borhyaena*. During the late Pliocene/Early Pleistocene, the Panama Isthmus formed, allowing predators of North American origin, such as the puma, the jaguar and the saber-toothed cat, *Smilodon populator*, to emigrate into South America and replace the native forms.

It is presumed that *Macrauchenia* dealt with its predators primarily by outrunning them, or, failing that, kicking them with its long, powerful legs, much like modern-day vicuña or camels. Its potential ability to twist and turn at high speed could have enabled it to evade pursuers.

## Distribution

*Macrauchenia* was distributed from Venezuela in the north to Argentina in the south (near Tierra del Fuego), as well as east into Brazil.

## Appearance in other media

### *Jurassic Park*

* *Macrauchenia* appeared in the video game Jurassic Park Builder.

## References

* Barry Cox, Colin Harrison, R.J.G. Savage, and Brian Gardiner. (1999): The Simon & Schuster Encyclopedia of Dinosaurs and Prehistoric Creatures: A Visual Who's Who of Prehistoric Life. Simon & Schuster.
* Jayne Parsons. (2001): Dinosaur Encyclopedia. DK.
* Haines, Tim & Chambers, Paul. (2006): The Complete Guide to Prehistoric Life. Canada: Firefly Books Ltd.

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