Giraffe (Giraffa spp.) are among the most unique extant mammals in terms of anatomy, phylogeny, and ecology. However, aspects of their evolution, ontogeny, and taxonomy are unresolved, retaining lingering questions that are pivotal for their conservation. We assembled the largest known dataset of Giraffa skulls (n = 515) to investigate patterns of cranial variability using 3D geometric morphometrics. The results show distinct sexual dimorphism and divergent ontogenetic trajectories of skull shape for the north clade (G. camelopardalis antiquorum, G. c. camelopardalis, G. c. peralta, and G. reticulata) and the south clade (G. giraffa angolensis, G. g. giraffa, G. tippelskirchi tippelskirchi, and G. t. thornicrofti) which was further supported statistically. Discriminant functions found statistically significant cranial shape differences between all four Giraffa species, and in some cases also between subspecies of the same species. Our 3D morphometric analysis shows that the four genetically distinct Giraffa spp. also have distinct cranial morphologies, largely addressable to features of display (ossicones). Our results highlight the importance of focusing future giraffe conservation efforts on each taxon to maintain their unique characteristics and biodiversity in the wild.

CIPb UAM Center for the Integration in Paleobiology Universidad Autónoma de Madrid Madrid Spain

Department of Biological Science University of Cape Town Cape Town South Africa

Department of Biology Unidad de Paleontología Universidad Autónoma de Madrid Madrid Spain

Faculty of Tropical AgriSciences Czech University of Life Sciences Prague Prague Czech Republic

Giraffe Conservation Foundation Windhoek Namibia

Institute of Biochemistry and Biology University of Potsdam Potsdam Germany

Museum für Naturkunde Leibnitz Institute for Evolution and Biodiversity Science Berlin Germany

National Museums of Kenya Nairobi Kenya

Research Institute of Wildlife Ecology University of Veterinary Medicine Vienna Austria

School of Biology and Environmental Science University College Dublin Dublin Ireland

Senckenberg Biodiversity and Climate Research Centre Frankfurt am Main Germany

Wildlife Research and Training Institute Naivasha Kenya

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