In an early review of Old World monkeys, Schultz (1970: 41) comments that “In most of their basic morphological characters … Old World monkeys are much more uniform than the other major groups of primates”. On the other hand, cercopithecid subfamilies clearly evince divergent functional specializations of the skull. “Colobines apparently have optimized biteforce magnitudes at the expense of a reduction in jaw gape in order to masticate leaves more efficiently. An increase in jaw gape is … advantageous to more frugivorous and/or terrestrial primates since they eat large food objects, which require extensive incisal preparation, and/or because of canine displays or canine slashing” (Hylander, 1979b:229).
Experimental studies have been instrumental in characterizing dynamic functional determinants of skull form in Old World monkeys and other primates (Luschei and Goodwin, 1974; McNamara, 1974; Hylander, 1979a–c, 1984, 1985; Bouvier and Hylander, 1981; Hylander et al., 1987, 1991a,b, 1992, 1998; Dechow and Carlson, 1990). In turn, morphological studies of cercopithecid subfamilies have greatly enhanced our knowledge of the functional bases of such craniodental variation (Hylander, 1975; Walker and Murray, 1975; Kay, 1978; Kay and Hylander, 1978; Bouvier, 1986a,b; Ravosa, 1988, 1990, 1991a–c, 1996; Lucas and Teaford, 1994).
Some research on the cercopithecid skull emphases the role of phylogeny in channeling morphological variation at the inter-and intra-specific level (Freedman, 1962; Fooden, 1975, 1988, 1990; Cochard, 1985; Cheverud and Richtsmeier, 1986; Leigh and Cheverud, 1991; Ravosa, 1991a,c; Shea, 1992; Richtsmeier et al., 1993; Profant and Shea, 1994; Ravosa and Shea, 1994; Profant, 1995).