The number of extant penguin species is debated. Depending on which authority is followed, penguin biodiversity varies between 17 and 20 living species, all in the subfamily Spheniscinae. Some sources consider the white-flippered penguin a separate Eudyptula species, while others treat it as a subspecies of the little penguin the actual situation seems to be more complicated. Similarly, it is still unclear whether the royal penguin is merely a color morph of the macaroni penguin. The status of the rockhopper penguin is also unclear.