Fig. 4.

Fundamental rigid frameworks of faces of (A) Australopithecus africanus, (B) Paranthropous robustus, and (C) Paranthropus boisei hypothesized by Rak (1983). Skull drawings are from Rak (1983: with permission). Rigid frames are constructed from interpretation of the text and from Figs 37 and 44 in Rak (1983). Rak states that the upper facial parts of the frames of A. africanus and P. robustus resemble the generalized condition, and that these taxa resemble P. boisei in having a zygomaticoalveolar member extending from the lower end of the inferior zygomaticofrontal member to the alveolar member. In (C) converging arrows represent compression of the zygomaticoalveolar member and diverging arrows represent tension of the single zygomaticofrontal member.