Australidelphia

Australidelphia is a superorder of marsupials encompassing about three-quarters of all living marsupial species, including all those native to Australasia and one South American species, the monito del monte. Unlike other American marsupials, which belong to the Ameridelphia, Australidelphia’s lineage emerged in South America, with genetic evidence (retrotransposon insertion sites) showing the monito del monte as its most ancient branch.

Within this superorder, the Australian members form a distinct group (clade) named Eomarsupialia, though their internal relationships (branching order) is yet to be determined. Studies suggest Australidelphia originated in South America alongside other major marsupial groups, likely dispersing to Australia via Antarctica in a single event after the monito’s lineage (Microbiotheria) diverged, leaving other South American orders (Didelphimorphia and Paucituberculata) as more basal.