An odd question occured to me. Would the vestigial arm discovery count as a free hand for the purposes of the crane style feats?
If so what about the races with prehensile tails?
Arm, definitely.
Tail, probably not. I'n not going to be so strict as to claim, "hand" and write it off. But the appendage in question should at least have the functionalities of a hand. Tail's too limited in what it can do to count.
Arm is total RAW. Tail is my opinion.