It may have nothing to do with predators:Obviously, but we are playing Darwinians. That means that any just so story qualifies, as long as it "cudda happened".
You've got to come up with a reason why an arm 10% of the way to being a wing was advantageous over a normal arm, and then a reason why an arm 20% of the way to being a wing was advantageous over the arm which was 10%... The whole thing is just ludicrous.