This character refers to the overall development of the posterosuperior and superior parts of the squamosal suture (Rak, 1978, 1983; Kimbel & Rak, 1985; Strait et al., 1997). For the same reason just outlined for parietal overlap (character 9), this feature is retained as an informative character. While Rak and Kimbel (1991, 1993) consider P. walkeri (KNM-WT 17000) to have an extensive overlap, Walker et al. (1993) examined this region in detail and concluded that it was not extensive and was within most hominin ranges of variability. Unlike Strait and Grine (2001), P. walkeri is considered not be distinctive in this feature. Thus, the only species characterized by this feature is P. boisei because its sutures are extensively developed to the degree that it is tapered with a bevel edge (= 1) (see Kimbel & Rak, 1985). Whether this condition is also present in the South African species is currently unknown due to poor preservation.
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