Wikipedia
Macraucheniidae is a family in the Litopterna order of extinct South American ungulates, an animal with similarities to the camel and rhinoceros. The reduced nasal bones of their skulls suggest that they may have had a small proboscis, or trunk. Their hooves were similar to those of rhinoceroses today, with a simple ankle joint and three digits on each foot. Thus, they may have been capable of rapid directional change when running away from predators, such as large Phorusrhacid terror birds, sparassodont marsupials, and Smilodon saber-toothed cats. Macraucheniids probably lived in large herds to gain protection against these predators, as well as to facilitate finding mates for reproduction.
The family Macraucheniidae includes genera such as Theosodon, Xenorhinotherium, and Macrauchenia. Macrauchenia is the best-known and most recent macraucheniid. It became extinct during the Pleistocene Epoch. It was one of the few litopterns to survive the ecological pressures of the Great American Interchange between North and South America, which took place after the Isthmus of Panama rose above sea level some 3 million years ago. It may instead have died out in the aftermath of the invasion of the Americas by human hunters. When Macrauchenia died out, so too did the Macraucheniidae and the entire litoptern order.