Foramen Magnum Shape

Unlike Strait et al. (1997), only two character states are recognized: oval/round (= 0) and heart shaped (= 1). Strait et al. (1997) and Strait and Grine (2001) recognize a "variable" state, as described for H. ergaster, because the sub-adult specimen KNM-WT 15000 is said to have a heart-shaped foramen (Walker et al., 1986), while adult specimens of this same species, KNM-ER 3733 and KNM-ER 3883, have an oval foramen.

Because of the specimens sub-adult status, the condition observed in KNM-WT 15000 is not considered.

An oval-round foramen is observed in Pongo, Gorilla, Pan, Sahelanthropus, Praeanthropus, K. platyops, Australopithecus, P. robustus, and all species of Homo (see Tobias, 1991; McHenry & Skelton, 1992; Strait et al., 1997; Strait & Grine, 2001; M.G. Leakey et al., 2001; Strait, 2001). Only P walkeri and P boisei are recognized as having a heart-shaped foramen magnum (see Tobias, 1967; Walker et al., 1986; Brown etal., 1993).

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