Taking opossums to have been the ancestors of the group, the author considers that the present writer may be right in his view that marsupials entered Australia from Asia by way of New Guinea.
These ancient opossums have been separated generically from Didelphys (in its widest sense) on account of certain differences in the relative sizes of the lower premolars, but as nearly the whole of the species have been formed .on lower jaws, of which some hundreds have been found, it is impossible to judge how far these differences are correlated with other dental or osteological characters.
From the Oligocene deposits of France and southern England have been obtained numerous remains of opossums referable to the American family Didelphyidae.
Of smaller mammals, raccoons, squirrels and opossums are very common.
I've seen opossums that weren't afraid of me, though.
Squirrels, racoons, woodchucks and skunks are common, and musk-rats, porcupines and opossums are found in some sections.
Arboreal species include the well-known opossums (Phalanger); the extraordinary tree-kangaroo of the Queensland tropics; the flying squirrel, which expands a membrane between the legs and arms, and by its aid makes long sailing jumps from tree to tree; and the native bear (Phascolarctos), an animal with no affinities to the bear, and having a long soft fur and no tail.
As regards function, the tail may be a mere pendent appendage, or may be adapted to grasp boughs in climbing, or even to collect food or materials for a nest or sleeping place, as in the spider-monkeys, opossums and rat-kangaroos.
Wallace, this author is of opinion that marsupials did not effect an entrance into Australia till about the middle of the Tertiary period, their ancestors being probably opossums of the American type.
Squirrels, rabbits, wood-chucks, skunks, muskrats and opossums are common.