And then you've got wallaroos, which are in-between sized. Here's a site with a few pictures.

Possum saren't the only non-Australiam marsupial;s: "Australia has about 120 species of marsupials, New Guinea has 53 species of marsupials, South and Central America have 90 species of marsupials, and North America has only two species of marsupials." - that is from this site.

You learn something new every day on the Mudcat.