Molar Cusp Position

The position of the lingual and buccal cusps is of dietary-functional importance and likely to be of phylogenetic significance, taking into account phylogenetic niche conservatism (see text). Strait and Grine (2001) are used in the definition of the character states and allocations for the hominins. In the case of the Miocene hominoids, because some species have extensive lingual cingulum (character 89), the location of the cusps ignores this feature, because the enamel extension gives a "false" reading of the position of the cusps relative to the occlusal surface.

The primitive condition is observed in Kenyapithecus (Andrews & Walker, 1976), Dryopithecus (Begun, 1994a), Graecopithecus (de Bonis & Koufos, 1993), Pongo, Gorilla, and Pan. The cusps are located close to their respective crown edges; that is, the cusps are not close together (= 0). The next condition observed in Praeanthropus, K. rudolfensis, H. habilis, H. ergaster, and H. sapiens is for the lingual cusps to be located close to the margin of the crown but the buccal cusps have moved medially (= 1). Ardipithecus and members of the "anamensis group" have lingual cusps that are close to the margin and buccal cusps moderately lingual to margin (= 2). Australopithecus has lateral movement of its lingual cusps and increased medial movement of its buccal cusps (= 3). Finally, in P. boisei and P. robustus is found the continued crowding of the occlusal surface with increased medial and lateral movement of the buccal and lingual cusps (= 4).

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