Evolution of craniofacial shape in relation to sexual dimorphism in Theropithecus and Papio

Ángeles Ossorio¹Ambra Figueroa-Torrejón²Rodrigo Buston¹Matteo Caldon³Jacinto Adriano Mathe^4,5Giuliano Doria⁶Spartaco Gippoliti^7,8Antonella Volta⁹Maria Joana Ferreira Da Silva^10,11,12René Bobe^13,4,5Susana Carvalho^13,4,5Cristian Capelli³Felipe I Martinez^14*

• ¹Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Santiago Metropolitan Region (RM), Chile
• ²Physical Anthropology Unit, Department of Biodiversity, Ecology and Evolution, Faculty of Biological Sciences, Universidad Complutense de Madrid, Madrid, Spain
• ³Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parma, Italy
• ⁴Department of Science, Gorongosa National Park, Sofala, Mozambique
• ⁵Institute of Human Sciences, School of Anthropology and Museum Ethnography, Social Sciences Division, University of Oxford, Oxford, England, United Kingdom
• ⁶Museo Civico di Storia Naturale "Giacomo Doria", Genoa, Italy
• ⁷IUCN/SSC Primate Specialist Group, Rome, Italy
• ⁸Società Italiana per la Storia della Fauna 'G. Altobello', Rome, Sicily, Italy
• ⁹Department of Veterinary Science, University of Parma, Parma, Italy
• ¹⁰CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, InBIO Laboratório Associado, Campus de Vairão, Universidade do Porto, Vairão, Portugal
• ¹¹BIOPOLIS Program in Genomics, Biodiversity and Land Planning, CIBIO, Campus de Vairão, Vairão, Portugal
• ¹²Organisms and Environment Division, School of Biosciences, Cardiff University, Cardiff, United Kingdom
• ¹³Interdisciplinary Center for Archaeology and Evolution of Human Behaviour (ICArEHB), University of Algarve, Faro, Portugal
• ¹⁴Escuela de Antropología, Facultad de Ciencias Sociales, Pontificia Universidad Católica de Chile, Santiago, Chile

Sexual dimorphism in cranial morphology is a significant aspect of primate evolution, providing insights into evolutionary pressures and mating systems in different species. This study focuses on cranial sexual dimorphism in Papio and Theropithecus, two closely related genera within the tribe Papionini. Using geometric morphometric techniques, we analyzed 570 cranial specimens from both genera, with data sourced from various studies and repositories. Thirty craniofacial landmarks were defined and analyzed through Geometric Morphometrics tools to evaluate shape variation. Our findings reveal distinct morphological clusters for each genus and sex, with Papio and Theropithecus exhibiting significant sexual dimorphism. The results distinguish genera and sex-based groups, indicating differential impacts of size on shape across groups. The findings suggest that while sexual dimorphism is stable in magnitude within each genus, the specific morphological manifestations differ. This research advances our understanding of the evolutionary mechanisms driving sexual dimorphism and emphasizes the need for further studies to explore the genetic and environmental factors influencing these differences. The innovative approach and comprehensive dataset provide a robust framework for future investigations into primate cranial morphology and its evolutionary implications.