Orbital Shape

Orbital shape will be affected by numerous processes, including cranial base angulation (Shea, 1985, 1988), facial height and breadth considerations (Rak, 1983), and capsular requirements (Enlow & Hans, 1996). This feature is thus rather complex and considered to be of developmental, functional, and phylogenetic interest. Three character states are recognized. Orbits, higher than broad (= 0) are observed in Dryopithecus (Begun, 1994a; Kordos & Begun, 1997) and Pongo. Circular-rhomboid shaped orbits (= 1) are observed in Sahelanthropus (as observed from Brunet et al., 2002, Figure 1, even though distorted), Pan, and all hominins preserving this feature (see Tobias, 1991; Wood, 1991; M.G. Leakey et al., 2001). Finally, rectangular orbits, broader than high, are observed in Graecopithecus, taking into account damage and some post-depositional distortion (de Bonis et al., 1990; de Bonis & Koufos, 1993), and Gorilla.

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