The family Elephantidae developed from the order Proboscidea. The Asian elephant, both species of African elephant and the Mammoth sit within this family. Previous to these species however were other closely related ancestors:
This species lived about 26 million years ago, characterised by having four tusks. Two tusks curved upward out of the upper jaw and two tusks curved downward out of the lower jaw.
This creature had two downward curving tusks that were probably used in a shovel-like manner to scoop vegetation out of the watery swamps where it lived. It existed approximately 25 million years ago. They had no tusks in their upper jaw, making them somewhat unusual.
This creature also had two lower flattened tusks, again probably used for digging and scooping vegetation.
More correctly classified as part of the family Mammutidae, the remains of the first Mammutidae (descended from the paleomastodon) were found in the 25 million-year-old Oligocene strata in Africa and Eurasia. These animals were about the size of today's elephants, but more solidly built with a hairy body.