Hippopotamids are deeply nested within the family Anthracotheriidae. The oldest known hippopotamid is the genus "Kenyapotamus", which lived in Africa from . "Kenyapotamus" is known only through fragmentary fossils, but was similar in size to "C. liberiensis". The Hippopotamidae are believed to have evolved in Africa, and while at one point the species spread across Asia and Europe, no hippopotami have ever been discovered in the Americas. Starting the "Archaeopotamus", likely ancestors to the genus "Hippopotamus" and "Hexaprotodon", lived in Africa and the Middle East.