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While the Paranthropus lineage was evolving its unique set of morphological features, the basal hominin to Australopithecus, Kenyanthropus, and Homo was also evolving its own set of unique anatomical features, distinct not only from the Paranthropus lineage, but also the earlier Miocene and Plio/Pleistocene hominids. At this point, we can see the emergence of a weaker supraorbital torus with no sagittal crests or compound temporal crests. The supraglenoid gutter is reduced in width. Mastoids have a reduction in lateral inflation. The anterior palate is now deeper and the diagonal malar length has continued to reduce in length. Finally, the face is reduced in depth.

Emerging from this ancestral population is Australopithecus, which has a number of apomorphies — mostly homoplasies with related taxa, though there remains a possibility that the branch positions of Australopithecus and Paranthropus have been switched. The petrous is intermediate in orientation, corresponding with intermediate cranial base breadth. Eustachian process is developed and the longus capitis is long and oval. Foramen magnum is positioned posteriorly. Frontal sinus is reduced. Mid-facial breadth has increased. Nasal bones are projected and tapered, with a developed nasal keel, and anterior nasal pillars are developed. Molar lingual cingulum is developed. Symphyseal recession has increased and is robust in construction.

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