Common names can always be a problem as can he lumpers and splitters thing, but I believe the black version of the leopard as is found in Africa and India is simply a melanistic version of the ordinary leopard, the scientific name of which is Panthera Pardus. The name panther is a misnomer taken from the scientific name and used more commonly in India than Africa.

Im not sure what the story is with the south American version but from what pictures I've seen, they appear to be more heavily built that the African and Indian version. - I don't even know if the same one spreads into north America or not.