They occupied a similar ecological niche to the modern hippopotamus and the related early proboscid Moeritherium, feeding on soft, aquatic plants in marshy environments. The Numidotheriidae are not believed to be direct ancestors of modern elephants, but a collateral branch.
These animals shared an ecological role with modern hippos and their ancient relatives, the proboscideans Moeritherium, by consuming soft aquatic vegetation in marshlands.  The Numidotheriidae are not thought to be direct ancestors of elephants, but rather a separate evolutionary lineage.