Litopterna

The Litopterns form an order of herbivorous South American mammals that were formerly associated with a number of other South American orders under the Meridiungulata. Recent DNA analysis showed however that the Litopterns were true ungulates and more specifically a sister group to the odd-toed ungulates (Perissodactyla), whereas the others meridiungulates were shown to be more closely related to elephants, sea cows and hyraxes. Litopterns were one of the victims of the Great American Interchange, when North and South America became connected, out-competed by the North American ungulates. The Litopterns were divided into a number of families, the most important being the Macraucheniidae (Macrauchenia, Theosodon) and the Proterotheriidae (Thoatherium, Diadiaphorus).