What makes bantams claws different from normal LF chickens?

I have hatched some bantam chicks and have noticed they have an extra claw at the back of their leg that other chickens dont tend to have. So what makes them like this?

Also how can you sex bantam or silkie chickens when they dont have the bright red comb and wattles im used to seeing?

Thanks for any advice

I was given the eggs I hatched so dont know much about them but some have come out yellow and some black. The yellow feathered ones have pink or white skin and the black feathered ones have greyish or black skin. Its only the black skinned chicks that have the extra toe on the back of thier leg. The black ones are looking like they'll be difficult to sex. Some are developing a pinkish comb whereas others arent so im wondering if thats a way of telling. They are just over 2 weeks old at the most so its still difficult to tell but my other large fowl chicks I have been sexing at 3-4weeks old then seperating them for 3 weeks more just to be sure before culling.

If you google "sexing your silkies pictures and tips" there is some info on there. You may have to wait until they are a bit older.

Shortened the links for you nuzuki.   

Look like you will have your work cut out even after 8 weeks!   

My smallest of 4 young bantams has just started to crow and show the ladies some affection.     The other 3 are still quiet and more interested in play fighting.