Debate has occurred regarding whether the sea mink was its own species, or another subspecies of the American mink. Those who argue that the sea mink was a subspecies often refer to it as "Neovison vison macrodon". A study in 1911 by Frederic Brewster Loomis, an American paleontologist, concluded that the differences between the American mink and the sea mink were too minute to justify the latter's classification as a separate species, and he named it "Lutreola vison antiquus". A study conducted in 2000 by Mead et al. refuted Loomis by claiming that the size range for the largest sea mink specimen was beyond that of the American mink, thereby making it a separate species. But a 2001 study by Graham concluded that this size difference was insufficient evidence to classify the sea mink as its own species and that it should be considered a subspecies. Graham supposed that the size difference was caused by environmental factors. Furthermore, Graham reported that Mead assumed the smaller mink specimens to be the American mink, and the larger mink specimens outside the range of the American mink to be sea minks; this may have been a case of sexual dimorphism wherein all specimens were sea minks, the larger ones being males and the smaller ones being females. A 2007 study compared the dental makeup of the sea mink to the American mink, and concluded that they were distinct enough to be considered two separate species.