As in other sthenurines, many bony elements of the foot and heel in Procoptodon were wider than in other kangaroos, in order to stabilize the single-toed foot. Flexion of the ankle joint was restricted to fore and aft movement. Correlated with this reduction was simplification of the digital tendons. Procoptodon had a functionally monodactyl hind foot: the lateral metatarsals II, III and V were so reduced that their distal ends and phalanges, or toe bones, were lost, the well developed digit IV forming a 'single' toe. The middle two fingers were elongated with long, recurved claws (forming a 'grappling hook' to grasp leafy branches). The forelimbs were unusually long and mobile in Procoptodon. Tim Flannery has compared them to the molars of the huge australopithecine Australopithecus boisei. The ape-like molar teeth of Procoptodon were brachyodont (low-crowned) and tended to develop additional longitudinal enamel folds. The last premolar in Procoptodon was complex and late-erupting. Both upper and lower incisors were small, and would have been used to nip vegetation. The lower jaws (dentaries) were massive and fused or ankylosed, and a 'chin' was developed. It had a very short, deep 'brachycephalic' skull and lower jaw, and eyes that were partly forward-facing (giving it a primate-like appearance). The heavily built Procoptodon goliah was the most extreme of the sthenurines, or short-faced kangaroos. Each hand had two long, clawed fingers that would have been used to bring leafy branches within reach.
It had an unusually short, flat face and forwardly-directed eyes, with a single large toe on each foot (reduced from the more normal count of four). The Pleistocene kangaroo Procoptodon goliah, the most extreme of the short-faced kangaroos, was the largest and most heavily built kangaroo known.
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