Mustela eversmanii beringiae
Mustela eversmanii beringiae is a fossil subspecies of the steppe polecat. It was the largest subspecies of steppe polecat and was larger than the largest extant subspecies, the Baikal steppe polecat. This polecat subspecies inhabited the unglaciated steppes of Beringia, and may have migrated southwards to give rise to the black-footed ferret. It became extinct during the Late Pleistocene megafaunal extinctions.