I just posted a long message and it timed out so this one will have to be a bit shorter.
As far as sexing goes you can usually tell fairly accurately at about a year or 12 inches. Basic lizard sexing applies: males have hemipenal bulges and enlarged femoral pores while this is not true for females. There are some other subtleties but you can't really tell unless you are familiar with the species. Since you have Mali's you can probably get a decent idea of the difference between the sexes.
As far as being "captive bred" they probably are not true captive bred specimens. According to the main Uromastyx breeders (Lindsay Pike, Douglas Dix etc) most young egyptian uro's that come in are "farmed," meaning gravid females are caught and allowed to lay their eggs in captivity. They have to be labeled captive bred to get past import laws so most that come in are falsely labeled.
Growth rate is very slow (well, I guess not all that slow if your used to cyclura). It can take an egyptian 8 years to reach full size and 4 years to reach sexual maturity. They will usually be around 12 inches at around a year. My little one was 7 grams and 5 inches when I bought him the first of december last year and is now 7 inches and 30 grams, and he is a great eater. I have found his growth to be exponential however: he barely grew the first four months and has really shot up lately. Other people have reported much faster growth rates.
Your uro looks extremely black. You can see some pictures of my little one Nebu at the link below. Is the other in the pair that black? Should be a interesting adult. Make sure to post updates on your little guys in the Uromastyx forum.
Peter

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