Abstract

The Patagonian huemul (Hippocamelus bisulcus), a critically endangered South American cervid, has undergone a severe population decline, and extant populations exhibit a high prevalence of skeletal disorders associated with chronic mineral deficiencies. Despite the biomechanical, postural, and clinical relevance of the axial skeleton, detailed information on its external morphology, internal architecture, morphometry, and elemental composition remains scarce for this species. Here, we address this gap by providing an integrative, multiscale characterisation of the postcranial axial skeleton of the Patagonian huemul. We hypothesised that the axial skeleton exhibits consistent regional patterns in external morphology, internal microarchitecture, and elemental composition identifiable using non-destructive analytical approaches. Three complete axial skeletons were examined using macroscopic anatomical analysis and linear morphometry, helical computed tomography with three-dimensional reconstruction, and semiquantitative energy-dispersive X-ray spectroscopy. Cervical, thoracic, lumbar, and sacral vertebrae, as well as ribs and sternum, were analysed following standardised veterinary anatomical terminology. CT imaging revealed regionally organised distributions of cortical and trabecular bone, including consistent basivertebral foramina and elongated internal cavities, together with segment-specific variations in internal density. Elemental analysis of compact bone demonstrated variable proportions of principal constituents among axial regions, with lumbar vertebrae showing the highest relative mineral content. These findings establish a comprehensive anatomical reference framework for the axial skeleton of the Patagonian huemul, complementing previous descriptions of the appendicular skeleton and cranial structures.