Male Sagittal Crest Development

The formation of a sagittal crest is clearly associated with masticatory considerations related to temporalis development relative to cranial size. In contrast with Skelton et al. (1986), Skelton and McHenry (1992) suggest phenotypic features associated with function should not automatically be dismissed as phylogenetically informative, given the concept of phylogenetic niche conservatism (see main text). While some may consider character 5 to be correlated with this character, an examination of Appendix Table 1 shows that this is not the case. For example, while there is a consistent correlation between strong anteromedial incursion of the temporal lines and sagittal crest formation, in some genera, moderate incursion may lead to a weak sagittal crest posteriorly (e.g., Praeanthropus [Kimbel et al., 1994]) or to no sagittal crest at all (e.g., Sahelanthropus [Brunet et al., 2002], Australopithecus, and Pan [D.E. Lieberman et al., 1996; Strait & Grine, 2001]).

A well-developed sagittal crest (= 0) is observed in Paranthropus males (Tobias, 1967; Rak, 1983; Skelton et al., 1986; Strait et al., 1997; Strait & Grine, 2001), Pongo, and Gorilla. Males of Praeanthropus and the "garhi group" usually have a weak sagittal crest, which is more posteriorly located (= 1) (Kimbel et al., 1994; Asfaw et al., 1999; Strait & Grine, 2001). Where preserved, males of Sahelanthropus (Brunet et al., 2002), Pan, K. platyops (M.G. Leakey et al., 2001), Australopithecus (Rak, 1983; Skelton et al., 1986; Skelton & McHenry, 1992), H. habilis (Tobias, 1991), K. rudolfensis (Strait et al., 1997; Strait & Grine, 2001), H. ergaster (B.A. Wood, 1991), and H. sapiens usually do not have sagittal crests (= 2). Note that while the "australopithecine" material from Sterkfontein is supposed to display sagittal crests, it is not considered here due to the current taxonomic confusion of this material. See Strait et al. (1997) and Strait & Grine (2001) for a differing interpretation.

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