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Abstract Taxonomic classification is important for understanding the natural world, yet current methods for species assessment often focus on craniodental morphology rather than the entire skeleton. Moreover, it is currently unknown how much variation could, or should, exist intragenerically. Here, we tested whether taxonomy can be accurately predicted based on patterns of morphological variation in macaques (H₁) and whether postcranial bones reflect subgeneric macaque taxonomy similarly, or better, than the cranium (H₂). Data included 3D scans of cranial and postcranial bones for eight macaque species (Macaca arctoides,Macaca fascicularis,Macaca fuscata,Macaca mulatta,Macaca nemestrina,Macaca nigra,Macaca radiata, andMacaca sylvanus). Fixed anatomical and semilandmarks were applied to scans of eight skeletal elements (crania = 45; mandible = 31; scapula = 66; humerus = 38; radius = 33; os coxa = 28; femur = 40; tibia = 40). For each skeletal element, regression analyses were performed to minimize the effects of sexual dimorphism. Between‐groups principal components analysis was used to visualize the major patterns of among‐species morphological variation, while the strength of correct taxon classification was measured with discriminant function analysis. Results suggested accepting the alternate hypothesis that different macaque species can be distinguished morphologically. Both cranial and many postcranial elements appeared to possess a taxonomic signal, and the limb bones—especially the upper limb—are reported to be more useful for taxonomic assessment than previously realized. Theoretically, certain behaviors and/or ecogeographical factors, as well as phylogeny, influenced skeletal morphology in macaques, likely contributing to taxonomic distinctions among different species. 

Taxonomic classification is fundamental for understanding the natural world, yet current methods for unknown species assessment are based on qualitative methods and focused on craniodental morphology. It is currently unknown how much variation could, or should, exist within a particular genus. Here, we tested whether taxonomy can be accurately predicted from patterns of morphological variation in a geographically widespread taxa, the macaques (H1) and whether postcranial bones reflect subgeneric taxonomy similarly, or better, than the cranium (H2). Data included 3D scans from nine species (M. arctoides, M. fascicularis, M. fuscata, M. mulatta, M. nemestrina, M. nigra, M. radiata, M. sylvanus, and outgroup Trachypithecus cristatus), for a sample of 297 individuals. Macaque species were chosen for their phylogenetic diversity and their geographic representation. 293 fixed and semilandmarks were applied to eight skeletal elements for each individual (crania=45; mandible=31; scapula=66; humerus=38; radius=33; os coxa=28; femur=40; tibia=40). A regression analysis was performed to minimize the effects of sexual dimorphism, making the primary input variables regression residuals. Patterns of variation were analyzed between- and within-species via Canonical Variates Analysis and 2D Multidimensional Scaling. Classificatory ability was tested using Discriminant Function Analysis. Results suggest that different species of macaque monkeys are taxonomically distinct and that the crania and postcrania possess a taxonomic signal. Some bones, like the limb bones, were more useful taxonomically than previously realized. Results suggest that taxonomic assessment should be updated to reflect newer methodologies and we argue that these results should inform future studies.