| In South America, a group known as the Xenarthrans developed, today represented by the anteaters, sloths and armadillos. |
| Elephant-shrews, xenarthrans, hystricognathous rodents, cetaceans, some pinnipeds, and primates depart sharply from this trend, however. |
| Against this backdrop, the ability of South America's xenarthrans to compete effectively against the northerners represents a special case. |
| Xenarthrans are a curious group of mammals that developed morphological adaptations for specialized diets very early in their history. |
| Due in large part to the success of the xenarthrans, one area of South American ecospace the Nearctic invaders were unable to dominate was the niches for megaherbivores. |
| Likewise, some modern therians like afrotheres and xenarthrans have secondarily developed lower body temperatures. |
