CONICET | Buscador de Institutos y Recursos Humanos

Macrauchenia patachonica is a native South American ungulate, now extinct, belonging to the Order Litopterna. It is the last species representative of the order, with records from the Early Pliocene (Ensenadan) to the Early Holocene (Lujanian). Its geographic distribution is extensive and includes Argentina, Chile, Uruguay, Bolivia, Paraguay, Perú and part of Brazil. General morphology and dentition place it as a cursorial herbivore, with a estimated body mass of 1,100 kg. Previous studies of the appendicular skeleton have proposed that M. patachonica could run and swerved to elude predators. In the present work, morphology, function, and bone resistance of the radio-ulna of M. patachonica are analyzed to test and to interpret different locomotor hypotheses. The methodology includes tomographic analysis to interpret bone morphology of the radio-ulna, and 3D finite element analysis study to test hypotheses of bone resistance to body mass support, both in standing posture and demanding locomotors postures. Additionally, a 3D digital model of M. patachonica was made to calculate its body mass and centre of mass. General preliminary results show that the radio-ulna had an internal bone configuration that increases resistance to tension and compression in the cortical region to the medial diaphysis in transverse and anteroposterior directions. Additionally, the general structure of the radio-ulna resulted in more transverse resistance to forces that act on the third distal part of the diaphysis. These results suggest that the anterior limb could resist high tensions in all directions with a grater transversal resistance capacity during body mass support and locomotion. Future research will use finite elements analysis to test whether the distal transverse resistance is tolerated by the radio-ulna during all locomotor demands or if it is associated with specific muscular action on this bone region.