Of the larger kangaroos, which attain a weight of 200 lb and more, eight species are named, only one of which is found in Western Australia.
Fossil bones of extinct kangaroo species are met with; these kangaroos must have been of enormous size, twice or thrice that of any species now living.
Huxley in 1880 briefly suggested the arboreal origin, or primordial treehabitat of all the marsupials, a suggestion abundantly confirmed by the detailed studies of Dollo and of Bensley, according to which we may imagine the marsupials to have passed through (r) a former terrestrial phase, followed by (2) a primary arboreal phase - illustrated in the tree phalangers - followed by (3) a secondary terrestrial phase - illustrated in the kangaroos and wallabies - followed by (4) a secondary arboreal phase - illustrated in the tree kangaroos.
The larger wallabies, or brush-kangaroos, such as the red-necked wallaby (M.
- The third and last sub-order of marsupials is the Diprotodontia, which is exclusively Australasian and includes the wombats, koala, cuscuses, kangaroos and their relatives.