Which group of mammals is the closest living relative of elephants?

The closest living relatives of elephants are manatees and dugongs, the aquatic mammals of the order Sirenia. Together, elephants and sirenians belong to the larger African mammal group Paenungulata.

This relationship can seem surprising because manatees and dugongs live in water while elephants are large terrestrial animals. Molecular studies, anatomical comparisons, and fossil evidence nevertheless place them on closely related branches of the mammalian family tree. Their shared ancestry is deep in geological time, so modern sirenians are relatives, not descendants, of elephants.

Hyraxes are a common alternative answer because they share several anatomical features with elephants, including certain details of their skulls, teeth, and reproductive anatomy. They are indeed close relatives, but current classifications generally place sirenians closer to elephants than hyraxes. The three groups are all part of Paenungulata.

Dugongs live mainly in coastal Indo-Pacific waters, while manatees inhabit coastal and freshwater environments in the Atlantic basin and parts of the Americas and West Africa. Hippopotamuses are more closely related to whales, and rhinoceroses belong to the perissodactyls, so neither is the best answer.