as well as Pongo and Gorilla. The selection of the Miocene genera is

based on their hominid status, as well as their proposed "African-like" hominid morphology (Cameron, in press [a]). Extant Pongo and Gorilla are included in the outgroup because their evolutionary emergence predates the appearance of the late Miocene and Pliocene fossil hominids/ hominins. The fossils that are believed to be part of the Ponginae — i.e., Sivapithecus, Ankarapithecus, and Lufengpithecus — have been excluded, given their derived morphological condition relative to the more "conservative" African ape condition, though extant Pongo is included. Because the emergence of the Pan lineage occurs within the time frame of the ingroup — i.e., perhaps after the emergence of Sahelanthropus — it is included as part of the ingroup.

Wood (1991), Skelton and McHenry (1992), Strait et al. (1997), and Strait and Grine (2001) have published the most recent interpretations of hominin phylogeny, which also provide detailed definitions and discussions of the characters used. This study tends to focus on the characters used by Strait et al. (1997) with modifications provided in Strait and Grine (2001). Data provided by Wood (1991) have been used to construct and define a number of characters. While Strait et al. (1997) is used as the starting point for this study, this is not to say that we agree with all of the character assignments provided by them. In some cases a different interpretation is provided, not only of the character state, but also of its condition within the taxa concerned; for example, it is considered here that anterior pillars (character 62) are variable within P. robustus, given the description of the recently published specimen from Drimolen (Keyser, 2000). Also, unlike previous studies, middle and late Miocene hominids are used to define the outgroup, and the new taxa, Sahelanthropus and Kenyanthropus, are considered for the first time. In some cases, the inclusion of these additional taxa has necessitated a review of some character states. A number of original characters, such as character 7 (temporal fossa size [as an index]), is also included. A total of 92 cranial, facial, dental, and mandibular characters was finally chosen for parsimony analysis distributed through 20 taxa (see Appendices). Characters that are known to be highly sexually dimorphic, such as canines, are defined by the male condition only. A number of metric characters were also defined. While in some cases, absolute linear measurements are used by Strait et al. (1997) to define character states, wherever possible, these have been converted into indices (see Appendices).

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