While I'm known for claiming that Squeenix is as dumb as a toad in boiling water, I think it's fairly safe to assume that there are other sub-races in off-screen locations (and probably not in Eorzea) for the simple reason that Squee might want to add new clans to the game eventually. Stating that there are no other clans anywhere in the world would be a very silly thing to do, specially since leaving that door open doesn't affect the game world in any form.
With that said, I wouldn't personally try to play a clan that isn't despicted in the game. There's no way to enforce it, neither in-character (because there's no lore supporting it) or mechanically (you can only pick one of the two clans each race gets). The most you can get away with is a half-breed that has the looks of one clan but not the other.
A thing I remember is that the Garleans learnt about the Primal threat after waging war over the beast-tribes of a neighbouring continent. I don't think I ever saw any lore about it besides that fact, so it's hard to say if the Empire ever annexed any non-Eorzean race (since anything called "beastman" was most likely exterminated).
With that said, I wouldn't personally try to play a clan that isn't despicted in the game. There's no way to enforce it, neither in-character (because there's no lore supporting it) or mechanically (you can only pick one of the two clans each race gets). The most you can get away with is a half-breed that has the looks of one clan but not the other.
A thing I remember is that the Garleans learnt about the Primal threat after waging war over the beast-tribes of a neighbouring continent. I don't think I ever saw any lore about it besides that fact, so it's hard to say if the Empire ever annexed any non-Eorzean race (since anything called "beastman" was most likely exterminated).