What is "didelphinae"

The Didelphinae are a subfamily of opossums consisting of 15 genera and 98 species, one of them extinct. Specimens have been collected throughout the Americas, but are predominant in South and Central America.

Some sources call this subfamily the "American opossums", while others use that term for the whole family of opossums, Didelphidae. The term is redundant, though, since all opossums are native to the Americas, while their taxonomic relatives, the possums, are native to Australia.