Abstract
The postorbital bar and septum are circumorbital structures that are important to adaptive hypotheses for the origins of primates and haplorhines, respectively. All primates possess complete postorbital bars, bony arches formed by processes of the frontal and zygomatic bones that encompass the lateral aspect of the eye. Postorbital septa, bony walls formed by the frontal, zygomatic and alisphenoid bones, walling off the orbit from the anterior temporal fossa, are limited to tarsiers and anthropoids. Numerous functional hypotheses have been advanced for postorbital bars and septa. Many of these hypotheses can easily be rejected (Cartmill, 1970, 1972, 1980; Ravosa, 1991a,b; Ravosa et al., 2000a,b; Ross, 1994, 1995a,b, 1996, 2000, 2001; Ross and Hylander, 1996; see Heesy, 2003). Cartmill (1970, 1972, 1980; see also Collins, 1921) suggested that in therian mammals with large eyes, relatively small temporal fossae, and derived orbit
Published Version
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