Supraorbital Sulcus Development

The frontal bone is defined by one of the following: sulcus is absent (0); mid sulcus (1); intermediate development of sulcus (2); or developed and deep sulcus (3). While it might be thought that the development of supraorbital sulcus may be correlated with supraorbital development (reflecting the same feature), this need not always be the case. For example, while Praeanthropus specimen A.L. 444-2 has the primitive hominid development in its supraorbital development (e.g., Gorilla and Pan), its supraorbital sulcus is described as being reduced, relative at least to Pan (Kimbel et al., 1994; D.E. Lieberman et al., 1996). Also, while Sahelanthropus has a strong supraorbital torus, it has a weak to non-existent frontal sulcus.

Dryopithecus (Begun, 1994; Kordos & Begun, 1997; Begun & Kordos, 1997) and Pongo (Andrews, 1992; Andrews et al., 1996), Sahelanthropus (Brunet et al., 2002), and H. sapiens do not have a supraorbital sulcus (= 0). Graecopithecus (de Bonis et al., 1990; de Bonis & Koufos, 1993) is defined by a mid supraorbital sulcus, enclosed by the temporal lines (= 1). The hominins Praeanthropus, Australopithecus, the "garhi group," species within Paranthropus and Kenyanthropus, are defined by intermediate development of a supraorbital sulcus (= 2) (see Strait et al., 1997; Asfaw et al., 1999; M.G. Leakey et al., 2002; Strait & Grine, 2001). Pan, H. habilis, and H. ergaster cannot easily be assigned to either condition observed in the other hominins as their sulcus is relatively deeper, though not to the degree observed in Gorilla (Strait et al., 1997; Strait & Grine, 2001). Thus, they are assigned to their own character state (= 3), which is between the condition observed in the other hominids and Gorilla. Finally, Gorilla is defined by a strong supraorbital sulcus (= 4) (Cameron, 1997a).

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  • Miikka
    What is supraorbital sulcus?
    8 years ago

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