Eritherium
Eritherium is the oldest known representative of the Proboscideans. It has not been assigned to any family in the order. Eritherium is the sister clade to Phosphatherium, Numidotherium and Moeritherium. This is one of the most complete evolutionary sequences of early mammalian radiations after the K/T extinction event. Thus, the elephants are one of the oldest "modern" mammal orders to have survived.