Ardipithecus ramidus

Ardipithecus ramidus is an example of the earliest known hominins. Members include humans and their ancestors that date to approximately 4.4 million years ago.

According to Science magazine, ardipithecus is not the oldest putative hominin, but it is by far the most complete of the earliest specimens. It includes most of the skull and teeth, as well as the pelvis, hands, and feet and reveal an "intermediate" form of upright walking, considered a hallmark of hominins. Paleoanthropologist Andrew Hill of Yale University is quoted as saying, "We thought Lucy was the find of the century but, in retrospect, it isn't."

Further Reading

http://www.archaeologyinfo.com/ardipithecusramidus.htm

http://www.d.umn.edu/cla/faculty/troufs/anth1602/pcardipithecus.html