What is "hippopotamidae"

Hippopotamuses are stout, naked-skinned, and amphibious artiodactyl members (and the only living members) of the family Hippopotamidae possessing three-chambered stomachs and walking on four toes on each foot. While they resemble pigs physiologically and are pseudoruminants like camels, their closest living relatives are actually the cetaceans (whales and dolphins).

There are two living species of hippopotamus in two genera; the pygmy hippo, Choeropsis liberiensis of the forests of west Africa, and the common hippo, Hippopotamus amphibius.