Asymmetric gait in locomotion of Hypsiprymnodon moschatus, the most primitive extant macropodoid marsupial

The evolutionary history of kangaroos and their relatives cannot be understood without considering the origins of their diverse locomotor behaviours, especially hopping. As the most primitive extant macropodoid, the musky rat-kangaroo, Hypsiprymnodon moschatus, can offer insight into evolution within the group, including the origin of bipedal hopping locomotion. Adult H. moschatus individuals were filmed in the wild to study their locomotor behaviour. Quantitative analysis of temporal footfall patterns showed that H. moschatus uses exclusively asymmetric gaits across slow and fast speeds of locomotion, predominantly employing a bounding gait. In addition, observations confirmed that it is restricted to quadrupedal gaits even at very fast speeds; there remains no evidence of hopping in this species. These results support the hypothesis that a shift to an asymmetric-gait-dominant locomotor repertoire was a functional prerequisite in the evolution of bipedal hopping in macropodoids.