This node represents the last common ancestor of P boisei and P robustus. With its emergence, pneumatization of the temporal squama is reduced and the parietals are defined by extensive overlap. External auditory meatus is large, and the anterior tympanic edge is either aligned or lateral to porion. The external cranial base is more flexed and the basioccipital is shorter. There is a continued reduction in the postglenoid process, which is fused to the tympanic. The vaginal process of the tympanic is large. There is increased anterior migration of the foramen magnum beyond the bi-tympanic line. There is an increase in the frequency of the occipitomar-ginal sinus, and the cerebellar is more tucked. The upper face has increased in overall breadth, including the interorbital. Finally, male upper canines are reduced in size and appearance. From this hypothetical ancestor, both later species of Paranthropus emerge.

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