Beyond Gorilla and Pongo: Alternative Models for Evaluating Variation and Sexual Dimorphism in Fossil Hominoid Samples

Sexual size dimorphism in the postca- nine dentition of the late Miocene hominoid Lufengpithe- cus lufengensis exceeds that in Pongo pygmaeus, demon- strating that the maximum degree of molar size dimor- phism in apes is not represented among the extant Hominoidea. It has not been established, however, that the molars of Pongo are more dimorphic than those of any other living primate. In this study, we used resam- pling-based methods to compare molar dimorphism in Gorilla, Pongo ,a ndLufengpithecus to that in the papio- nin Mandrillus leucophaeus to test two hypotheses: (1) Pongo possesses the most size-dimorphic molars among living primates and (2) molar size dimorphism in Lufengpithecus is greater than that in the most dimorphic living primates. Our results show that M. leucophaeus exceeds great apes in its overall level of dimorphism and that L. lufengensis is more dimorphic than the extant spe- cies. Using these samples, we also evaluated molar dimor- phism and taxonomic composition in two other Miocene ape samples—Ouranopithecus macedoniensis from Greece, specimens of which can be sexed based on associ- ated canines and P3s, and the Sivapithecus sample from Haritalyangar, India. Ouranopithecus is more dimorphic than the extant taxa but is similar to Lufengpithecus, demonstrating that the level of molar dimorphism required for the Greek fossil sample under the single-spe- cies taxonomy is not unprecedented when the compara- tive framework is expanded to include extinct primates. In contrast, the Haritalyangar Sivapithecus sample, if it represents a single species, exhibits substantially greater molar dimorphism than does Lufengpithecus. Given these results, the taxonomic status of this sample remains equivocal. Am J Phys Anthropol 140:253-264,