Incisive Canal Development

This character is similar to that discussed in Cameron (1997a). This feature is related to the development in length and caliber of the incisive canal. This feature is also of interest in terms of the conditions associated with airorynchy and klinorynchy (Shea, 1985, 1988). It is also of interest in the impacts that its reconfiguration has on the capsular system. It is distinct from the previous character in that a species with a distinct step to the nasal floor can have a moderately developed canal or it may have no canal at all, but, rather, a large incisive foramen. This character does, however, combine incisive foramen size and canal development, which have been treated as distinct characters in the past (e.g., Begun, 1992).

The primitive condition is for a broad "canal," as observed in Dryopithecus (Cameron, 1997a), Graecopithecus (de Bonis & Melentis, 1987), Gorilla, and Pan (McCollum & Ward, 1997). Also, H. habilis (defined by specimens OH24 and OH 62) is said to be similar to the chimpanzee in this feature (Tobias, 1991; see also Kimbel et al., 1997). An intermediate condition (= 1) defines members of the "anamensis group" (C.V. Ward et al., 2001), Praeanthropus specimen A.L. 200-1a (Kimbel etal., 1997), and Australopithecus, which has a developed canal (Rak, 1983) but not to the extant observed in H. sapiens. An extensive canal (= 2) defines Pongo, species of Paranthropus (Rak, 1983; McCollum et al., 1993), H. ergaster (Walker & Leakey, 1993b), and H. sapiens (McCollum & Ward, 1997).

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