The whole arm?? There's still fingers, toes, and probably teeth. Though, considering they got 'teeth' as a separate body part last time, it might be safer to take a digit. And that way they can each have one whole finger bone. Or heck, they could split one bone among each other. But I guess the manga isn't concerned much about the logic and anatomy, since it wants to focus on the drama and how quickly people turn against each other when their life - or the life of someone they love - is on the line.
