Litoptern

Scientific name: Macrauchenia patachonia Scientific classification:

Phylum: Chordata

Class: Mammalia

Renata Cunha Art
Litoptern—The litopterns were an unusual group of herbivorous mammals found throughout South America. The species depicted here was the last of their kind. (Renata Cunha)

Order: Litopterna Family: Macraucheniidae When did it become extinct? This species of litoptern became extinct around 10,000 years ago.

Where did it live? The litopterns were found only in South America.

In 1834, the young Charles Darwin discovered the foot bones of an extinct herbivorous mammal in Patagonia. Initially, these bones were thought to have once taken the weight of a giant llamalike animal, but it was later realized that they belonged to a very different creature. Most of the large plant-eating mammals that have wandered the earth for the last few thousand years can be divided into two major groups: the odd-toed ungulates (perrisodactyls)—animals like horses and rhinoceri—and the even-toed ungulates (artio-dactyls), a group that includes deer, cattle, and so on. In the years following Darwin's discovery, more finds came to light, and it slowly became clear that up until about 10,000 years ago, South America had its own large plant-eating mammals, and they were unique—quite different from the odd-toed and even-toed ungulates.

One group of these unique, South American herbivores was the litopterns. The last of the litopterns to become extinct looked like a stocky, humpless camel with thick legs. With a shoulder height of 1.5 m and a body length of 3 m, this litoptern was one of the larger South American mammals. The nasal openings on the skull of this animal are very near the top of the head, which has led paleontologists to believe that they probably had a short trunk. We can't be sure what a stubby trunk was for, but it may have been used to grasp low branches and to pull them within reach of its mouth, in the same way that a giraffe uses its long prehensile tongue to grab vegetation on high branches. The largest of the litopterns had a three-toed, flat-footed stance, but some of the more lightly built species had slim legs that ended in a single toe. At the center of these slim legs were strong bones and flexible joints—the hallmarks of fleet-footed animals that evade their enemies with speed and maneuverability.

These odd plant eaters needed some way of evading danger as prehistoric South America was home to lots of fearsome meat eaters. There were fearsome felines, killer marsupials, and terrifying birds, so the litopterns must have always been on the lookout for danger as any one of these predators was quite an adversary. Even an adult of the biggest of these bizarre herbivores was no match for the most powerful saber tooth cat that has ever lived (Smilodon populator—see the entry "Saber Tooth Cat" earlier in this chapter). The soft underside of the litoptern's long neck was probably a very attractive target for the saber tooth cat, and it is likely that they were commonly killed and eaten by these formidable felines. The larger terror birds must have been quite capable of killing the smaller litopterns as well as juveniles of the larger species.

Speed gave the smaller litopterns some protection from predators, but their most effective defense was probably strength in numbers, and it is very likely that these extinct animals lived in herds in the same way as living herbivorous mammals. It makes sense for any large animal with lots of enemies to live in herds as there will always be several pairs of eyes on the lookout for danger. Almost all predators rely heavily on the element of surprise, and without this, they stand little chance of making a successful kill. The litopterns used their keen senses of sight, smell, and hearing to alert the herd to danger. When a predator did launch an attack against a herd of these animals, it is likely that they singled out the young, old, and sick animals as a healthy adult litoptern must have been very difficult to catch.

With numerous predators all wanting to get their teeth, claws, and beaks into the succulent flesh of litopterns, life on the grasslands of South America must have been very difficult for these herbivores, and about 2.5 million years ago, something happened that made things even more difficult. The Great American Interchange saw all sorts of wildlife stream into South America from the north. Some of these creatures competed with litopterns for food, and others hunted them. All these new challenges were played out within the backdrop of a changing world. Sea levels were falling and the global climate was becoming drier and cooler—bad news for trees, the likely favored food of the litopterns. The times following the Great American Interchange must have been very tough for these odd ungulates. Their habitat was disappearing, strange animals from the north competed with them for the food that was left, and a number of cat species, also immigrants from the north, and deadly in tooth and claw, were well equipped to hunt the remaining litopterns. Long after the Great American Interchange reached its peak, humans spread throughout South America, and they, too, must have hunted the remaining populations of litopterns, which, by that point, must have been reduced to a shadow of their former strength. Squeezed from all sides, these unique, plant-eating mammals eventually became extinct around 10,000 years ago.

♦ Darwin's discovery of the first litoptern fossils was made during his voyage on HMS Beagle. The ship stopped for some time in Patagonia, allowing Darwin to explore these lands, and it was then that he discovered and excavated the bones of several extinct South American mammals.

♦ The name "litoptern" means "simple ankle" and refers to the bone structure of the ankle of these animals as the articulation of the bones is not as complex as in other large herbivorous mammals.

♦ Fossils of Macrauchenia patachonia have been found in Patagonia all the way up to Bolivia, so this was a very widespread species. Many litoptern fossils have been discovered in the Lujan formation, near Buenos Aires in Argentina.

♦ The placental mammalian predators that moved into South America during the Great American Interchange included familiar animals like the jaguar and puma.

Further Reading: MacFadden, B.J. "Extinct Mammalian Biodiversity of the Ancient New World Tropics." Trends in Ecology & Evolution 21 (2006): 157-65; Reguero, M. A., S. A. Marenssi, and S. N. Santillana. "Antarctic Peninsula and South America (Patagonia) Paleogene Terrestrial Faunas and Environments: Biogeographic Relationships." Palaeogeography, Palaeoclimatology, Palaeoecology 179 (2002): 189-210; Tonni, E. P., A. L. Cione, and A.J. Figini. "Predominance of Arid Climates Indicated by Mammals in the Pampas of Argentina during the Late Pleistocene and Holocene." Palaeogeography, Palaeoclimatology, Palaeoecology 147 (1999): 257-81.

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Responses

  • yrj lax
    Are litopterns marsupial?
    5 months ago

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