Litopterns (IMAGE) Aarhus University Caption Litopterns, like this <em>Macrauchenia patachonica </em>discovered by Charles Darwin, were a strange looking group of prehistoric South American mammals that were not closely related to any species alive today-they diverged evolutionarily from other mammals over 65 million years ago. When they went extinct at the end of the Ice Age, the mammal Tree of Life lost one of its deepest branches. Credit Robert Bruce Horsfall [Public domain], via Wikimedia Commons Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.