Within the genus Mustela, ferrets belong to the subgenus Putorius, from which there are only three extant species: M. putorius, the European polecat; M. eversmanni, the Siberian, or steppe polecat; and M. nigripes, the black-footed ferret.f the 16 extant species currently classified in the genus Mustela, ten have weasel in their common name. Among those that do not are the stoat or ermine, the two species of mink, and the polecats or ferrets. depends what you mean by weasels--they are in the weasel genus Mustela.