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The distinctive mark of Hominini is generally taken to be upright land locomotion on two legs (terrestrial bipedalism).
The does not indicate with certainty if this species was at all terrestrial, although the fairly forward position of its foramen magnum (the hole through which the spinal cord exits the braincase) may suggest a habitually upright posture.
Some paleoanthropologists extend the span of this species far back into time to include many anatomically distinctive fossils that others prefer to allocate to several different extinct species.
In contrast, a majority of paleoanthropologists, wishing to bring the study of hominins into line with that of other mammals, prefer to assign to molecular clocks to calculate how long species had been separated from a common ancestor.
The design of her pelvis and feet are suggestive of bipedal locomotion.
However, other skeletal elements indicate that she spent much of her time clambering through the branches of trees.
Ardi’s skeleton, which is more than 50 percent complete, dates to about 4.4 mya.These fossils, along with the slightly older trails of footprints found at Laetoli, Tanzania, prove that early hominins were upright bipeds when on the ground.However, they also retained many reminders of their tree-dwelling ancestry, especially their rather long arms, short legs, narrow shoulders, and long grasping extremities.The most remarkable aspect of this skull is the broadness and flatness of its face—something previously associated with much more recent hominins—in conjunction with a smaller, ape-sized braincase.
This specimen also has small canine teeth compared with those of apes, thus aligning it with the hominins in an important functional regard.Since then the molecular data and a steady trickle of new hominin fossil finds have pushed the earliest putative hominin ancestry back in time somewhat, to perhaps 8–6 mya., based on a cranium from of Chad in north-central Africa.