Hi Paul,
I have been thinking about this myself and have change my mind a couple of times
but its a shadow. The shadow source could be from the body of Saturn casting a shadow onto it self (idea from Paul Hease, thanks Paul).
But take a look at these two picture as they are very interesting. Shadow 2 the picture attached was taken on the same night but at about 13:29 ut (maybe a moon shadow).
But I think Paul and others where right