Hominoid nasal region polymorphism and its phylogenetic significance

The morphology of the nasal bones and their articulations with the adjoining frontal and maxillary bones have recently been reported in Nature and elsewhere to be diagnostic of hominoid taxa, and cladistic analysis based on these features has been used to assign two immature Plio-Pleistocene hominoids (AL 333-105 and Taung) to different lineages (Paranthropus and Homo, respectively). Because earlier studies had established that hominoid crania are highly variable intraspecifically, it seemed desirable to try to replicate the study reporting a consistently different pattern for each hominoid taxon. My results show extensive polymorphism in the nasal region within every taxon of extant pongids, including several rather clear examples, in extant Pan troglodytes, of that recently hypothesized to be a 'paranthropine' pattern. These findings underscore the substantial risks inherent in cladistic analyses using very restricted character sets to assign individual specimens to particular taxa.