Short-faced kangaroos such as Procoptodon are possibly some of the weirdest macropodids, as they didn’t do that most kangaroo-ish of activities: hopping. Instead, biomechanical studies and fossilised footprints both suggest that they walked on their toes. Further features of Procoptodon include its forward-facing eyes and freakishly long arms, which were apparently used to grab branches while browsing. The short face of these kangaroos is an adaption for chewing on tough leaves; a similar box-shaped head is also seen in koalas.