Trap, in 1987 I shot a four point in northcentral PA with an unusual overbite. It seemed like the lower jaw stopped developing as a fawn. I shot him as he trailed a doe and her fawn. He certainly looked stange. My friend's dad was my high school biology teacher and a deputy game warden. As I recall, he was not all that surprised by it and indicated it was a genetic trait much like piebalds and albinos. I have some pictures of it, but they're the ones that we took after butchering. I don't think they're appropriate for the internet.