The common ancestors of Australian land- and treedwelling kangaroos had prehensile (grasping) tails and long opposable thumbs, attributes that are well-adapted to tree-dwelling but offer kangaroos few advantages on land
It is hardly surprising, ttherefore, that land-dwelling kangaroos eventually lost these attributes; what is puzzling is the fact that all modern tree-dwelling kangaroos now lack them as well
Modern tree-dwelling kangaroos' tails cannot grasp branches, but they are somewhat longer and more flexible than those of modern land-dwelling kangaroos.