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.
They were then arboreal; but they speedily entered upon a rapid, although short-lived, course of evolution, during which leaping terrestrial forms like the kangaroos were developed.
- 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.
By means of the little musk-kangaroo, the cuscuses and phalangers, constituting the family Phalangeridae, are so closely connected with the kangaroos, or Macropodidae, that in the opinion of some naturalists they ought all to be included in a single family, with three sub-families.