Possuidae

Possuidae is a taxonomic name that has appeared in some classifications to designate a family of marsupials commonly referred to as possums and opossums. The scope and rank of Possuidae have varied across authors, and in modern mammal taxonomy the name is not recognized as a valid, monophyletic family. In several historical treatments, Possuidae encompassed a broad array of marsupials from both the American opossums and their Australasian relatives, leading to an assemblage that does not correspond to a single lineage.

As a consequence, current classifications assign the species once placed in Possuidae to other families within different orders. American opossums are placed in Didelphidae (order Didelphimorphia), while Australasian forms are distributed among families such as Phalangeridae, Petauridae, and others in the order Diprotodontia. The questions around Possuidae reflect changes in marsupial systematics driven by new morphological and molecular data, which indicate multiple, independent evolutionary histories rather than a single unified family.

If used, the historical concept of Possuidae generally referred to small- to medium-sized, nocturnal, arboreal marsupials with varied diets, including fruit, leaves, insects and small prey. Adaptations such as prehensile tails, gliding membranes, and strong nocturnal scent marking appeared in several but not all lineages associated with the name. Today, Possuidae is regarded as a historical or unresolved term rather than a current, valid taxon.