Definition
Ardipithecus is a genus of early hominins from the Awash valley of Ethiopia, known from two species: A. kadabba (~5.8–5.2 mya) and A. ramidus (~4.4 mya). The most complete specimen, ARA-VP-6/500 — nicknamed 'Ardi' and described in 2009 after fifteen years of preparation — is a partial skeleton including skull, pelvis, hands, and feet, the most informative early-hominin skeleton between 7 and 4 mya.
Ardi's anatomy is a mosaic that does not fit modern apes or modern humans. The pelvis is short and broad, the foramen magnum is positioned for upright posture, and the lower limb shows adaptations for bipedal walking on the ground. But the foot retains a divergent grasping big toe, and the limbs and hands are suited to climbing in trees.
Why it matters
Where it shows up
A. ramidus is known from many specimens at the Aramis locality in the Middle Awash, deposited in a closed woodland environment alongside diverse small mammals. A. kadabba is older and known only from teeth and a toe bone; the toe shows a bipedal foot strike pattern but is morphologically primitive.
The Ardi skeleton itself was so fragile and embedded in sediment that preparation took over a decade. The painstaking work and the resulting comprehensive 2009 publication in Science set a new standard for early-hominin fossil reconstruction.