Wallaby, any of a number of small and medium-sized kangaroos of the genus Macropus and allied genera. The large wallabies, or brush kangaroos, are more brightly colored and are smaller than the typical, gray kangaroo. They live for the most part in the open grasslands, where they feed at night and rest in the day in the dense scrub. The best-known of the medium-sized group are the rock wallaby and nail-tailed kangaroo. The former, living in rocky regions, have as specialized a foot structure as do the large kangaroos. Perhaps the most beautiful kangaroo is the latter, the small, graceful, nail-tailed wallaby, which lives in semi-arid country. It is highly specialized in foot and tooth structure and possesses a horny growth resembling a nail on the end of its tail. The smallest of the wallabies, about the size of rabbits, include the paddymelon and the hare wallaby. The fur, especially of the larger species, is much used.