Swedish naturalist Carl Linnaeus first described the common merganser in 1758 as Mergus merganser. Subsequent descriptions for the common merganser are Mergus merganser merganser (northern Europe and northern Asiatic Russia), M. m. orientalis, 1845 (M. m. comatus, 1895) (Central Asian mountains), and M. m. americanus, 1852 (North America). Their physical descriptions are mainly limited to bill shape and size, and in the case of the North American species a black bar crosses the white inner wing (visible in flight).