There is debate whether the two extant subspecies of red panda should be considered separate species.
The distribution of the red panda is disjointed, with two extant subspecies, Ailurus fulgens fulgens, the Western red panda, and Ailurus fulgens styani, Styan’s red panda. The Brahmaputra River is often considered the natural division between the two subspecies, where it makes a curve around the eastern end of the Himalayas, although some authors suggest the Western red panda extends farther eastward, into China.
Styan’s red panda is distinguished from the Western red panda by its longer winter coat and greater blackness of the pelage, bigger skull, more strongly curved forehead, and more robust teeth. This description is based on skulls and skins collected in Sichuan, Myitkyina close to the border of Yunnan, and Upper Burma. The Styan’s red panda is also supposedly larger and darker in color than the Western member of the species, but with considerable variation in both subspecies, and some individuals may be brown or yellowish brown rather than red.
There is debate whether Ailurus fulgens fulgens and Ailurus fulgens styani should be considered separate species or subspecies of red panda.