Kangaroos present another fascinating glimpse into evolutionary adaptation. This marsupial from the Australian continent fills a similar ecological niche as ungulates such as horse and deer on the American, Eurasian, and African continents.
Like ungulates, kangaroo hind limbs have elongated and the number of bones has reduced. Unlike ungulates, kangaroos increase their speed by hopping bipedally in a locomotory style called ricochetal.
Kangaroo forelimbs are disproportionately short which reduces unnecessary weight but which makes quadrupedal locomotion difficult. Their muscular tail is used as a counterbalance and conserves energy when hopping and solves the quadrupedal problem. When not hopping, kangaroos employ pentapedal locomotion using their tail as a fifth limb!