This is defined by an index of bijugal/bi-frontomalare temporale, using the same method described for character 2, to construct the character states. This feature is distinct from character 44, because it describes the breadth of the upper face relative to the mid-face, while the previous character measures the relative breadth of the upper face between hominid taxa. This feature is likely to be of developmental and functional interest because it relates to musculature development (e.g., temporalis and mas-seter). All data for the fossil hominins have been taken from B.A. Wood (1991); data for the extant hominids are unpublished data collected by Cameron. The mean index for the extant hominids (n = 121) is 1.09, with one standard deviation of 0.07. Thus, any value less than 1.02 indicates that the upper face and lower face have a similar breadth; any value between 1.02 and 1.16 indicates an intermediate condition; while any value greater than 1.16 indicates that mid-facial breadth is significantly greater than that of the upper face. The extant hominid minimum value is 0.94, and the maximum value is 1.25.
No specimens were defined here by having a similar breadth as defined by the indices generated here. Upper and mid-facial breadth are defined by the intermediate condition (= 0) in Graecopithecus specimen
XIR-1 (original) with an index of 1.02, P. boisei with a mean index of 1.15 (n = 2), P robustus with a mean of 1.09 (n = 2), K. rudolfensis with a mean of 1.07 (n = 2), H. habilis specimen KNM-ER 1813 with an index of 1.02,
H. ergaster with a mean index of 1.05 (n = 2), Pongo has a mean index of
I.15 (n = 21), Gorilla with a mean index of 1.14 (n = 36), Pan with a mean of 1.04 (n = 64), and H. sapiens with a mean index of 1.10 (n = 8). A broad mid-face, relative to upper facial breadth (= 1), is observed in Australopithecus specimen Sts 5 with an index of 1.18. A very broad mid-face (= 2) is observed in P. walkeri specimen KNM-WT 17000 with an index of 1.28, which is beyond the extant hominid range.
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