Mandibular Extramolar Sulcus Width

This feature has been related to a more parabolic shape in the dental arcade, resulting in an M3 placed more medially then the M2, and will result in a large space between the M3 and the ramus, which is said to be essential in accommodating transverse movements of the M3, both of which lie posterior to the ramus (see Aiello & Dean, 1990). The character state definitions and most species allocations as provided by Strait et al. (1997) and Strait and Grine (2001) are followed here, with only one exception (see later).

The primitive state is represented by a broad sulcus (>6.5 mm) (= 0), which is observed in Pongo, Gorilla, P. robustus, and P. boisei. While no metrical data are available for Graecopithecus, they are clearly very broad (de Bonis & Koufos, 1993). Intraspecies variability (= 1) is observed only in Australopithecus. The sulcus is narrow (= 2) in Pan, Praeanthropus, K. rudolfensis, H. habilis, H. ergaster, and H. sapiens. Homo habilis is allocated as having a narrow sulcus, for all East African specimens are narrow. Strait et al. (1997) include the South African specimen SK 15 in their definition of this species, which has a wide sulcus. Thus, unlike DWC, they define H. habilis as variable.

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