I haven't worked with much other than green and copper. Recently I've tried dragons and their color outcomes are confusing - even current copper result differently compared to their genetics 3 yrs ago.
From what I came up with, I conclude that the super black was produced in the attempt to create black dragons. Thus they mixed melano's with dragons and coppers - which carry some sort of red, metallic, and other genes
I disagree that blacks (whatever kind) need marble genes. In fact I believe the marble ruins the black in general and makes it colorless. IMO the marble and butterfly gene (or pheno or whatever) is used to create a unique color combo. I agree with MrV that super black may be copper based - I get a number of black .... melano like .... from my copper to copper and copper to yellow dragon - which means that they have been regularly crossed. ... also a lot of marbles mainly in the black ones (I don't know what this means).
Given that super blacks aren't true melano's (more of a melano-copper geno), thus the females shouldn't be infertile. So you can trust whoever selling super black females who claims that they're fertile..... but then again I'm not sure. One thing you can be sure of is that if the super black is a new color variation, you won't get too many of them in your fry unless, of course, you use 2 super black parents. You might get more in F2 or F3..... again not sure - waiting to do F2.
I must emphasize the fact that this is only my opinion and thus is NOT necessarily true - still trying to understand the genetic make up in general.