Another possibility, go with me here, are the “original” Remans. That is, the aliens on Remus (Romulus, too?) that were enslaved when the Romulans arrived at the twin planets and then mated with to create the ghastly-looking Remans we know today. After all, natural evolution would not create such profound differences in only a couple of thousand years.
You could say it was radiation or something, but why do they look like bats and not sickly mutants, like those poor irradiated bastards in Total Recall?
Maybe the original Remans were giant bat-looking creatures native to the caves of Remus — with or without wings. I guess it wouldn’t be as easy as a bored Romulan miner lifting up one of their skirts one night but would require purposeful genetic intervention by the Romulan scientists. Or who knows, maybe it was love at first, but tragically the Romulans would have none of that and cursed the descendants of Romulan Adam and Reman Eve to an eternity of servitude.
(I really really don’t like the Remans, but I’m trying to think of a reason for the blasted space Nosferatu to exist.)
