(Cervus canadensis) (Alces alces) and the Reindeer (Rangifer tarandus)
Though the reindeer (or caribou) was long known to be a distinct species of holarctic deer, the elk (or wapiti) was thought to be a subspecies of the European red deer until quite recently. To confuse things even more, the early European explorers thought that the elk was a subspecies of moose, leading to the word “elk” meaning moose in much of Europe. If that’s not enough, elk (Cervus canadensis) exist throughout Siberia and in Manchuria and Mongolia, but are known as “maral” in most regions, because of confusion with the East European red deer (Cervus elaphus maral), and the Mongolian subspecies of elk is known as the Alatai maral, even though it’s since been re-classified as Cervus canadensis sibericus.
Ok, so I apparently did not triple-check this and I put in an “elk” that was really a moose, but I’m gonna go ahead and blame this one on nomenclature.
Well…at least we know what a reindeer is. For their body size, the more southerly subspecies of bull reindeer have the largest antlers of any deer, even outclassing the largest bull moose (though not in overall size). The more northerly reindeer have smaller and more spindly antlers, with fewer prongs. Unlike many deer, the reindeer antlers always grow in two specific directions, and have a very delineated anterior and posterior branch.
The Handy Natural History. Ernest Protheroe, 1910.