Finite element analysis of kangaroo astragali: A new angle on the ankle

Using finite element analysis on the astragali of five macropodine kangaroos (extant and extinct hoppers) and three sthenurine kangaroos (extinct proposed bipedal striders) we investigate how the stresses experienced by the ankle in similarly sized kangaroos of different hypothesized/known locomotor strategy compare under different simulation scenarios, intended to represent the moment of midstance at different gaits. These tests showed a clear difference between the performance of sthenurines and macropodines with the former group experiencing lower stress in simulated bipedal strides in all species compared with hopping simulations, supporting the hypothesis that sthenurines may have utilized this gait. The Pleistocene macropodine Protemnodon also performed differently from all other species studied, showing high stresses in all simulations except for bounding. This may support the hypothesis of Protemnodon being a quadrupedal bounder. Using finite element analysis on the astragali of macropodine and sthenurine kangaroos we investigate how stresses experienced by kangaroos of different hypothesized/known locomotion compare under different scenarios. We show a difference in performance between both groups with sthenurines experiencing lower stress in simulated bipedal strides compared with hopping, supporting the hypothesis that sthenurines may have utilized this gait. The Pleistocene macropodine Protemnodon also performed differently from all other species, its results possibly supporting the hypothesis Protemnodon is a quadrupedal bounder.