Diprotodontids were the largest marsupials to exist and an integral part of Australian terrestrial ecosystems until the last members of the group became extinct approximately 40 000 years ago. Despite the frequency with which diprotodontid remains are encountered, key aspects of their morphology, systematics, ecology and evolutionary history remain poorly understood. Here we describe new skeletal remains of the Pliocene taxonZygomaturus keaneifrom northern South Australia. This is only the third partial skeleton of a late Cenozoic diprotodontid described in the last century, and the first displaying soft tissue structures associated with footpad impressions. Whereas it is difficult to distinguishZ. keaneiand the type species of the genus,Z. trilobus, on dental grounds, the marked cranial and postcranial differences suggest thatZ. keaneiwarrants genus-level distinction. Accordingly, we place it in the monotypicAmbulatorgen. nov. We, also recognize the late MioceneZ. gillias anomen dubium. Features of the forelimb, manus and pes reveal thatAmbulator keaneiwas more graviportal with greater adaptation to quadrupedal walking than earlier diprotodontids. These adaptations may have been driven by a need to travel longer distances to obtain resources as open habitats expanded in the late Pliocene of inland Australia.