Now you have really complicated my family tree! I thought Irish, English, German, Cherokee, and Choctaw was mixed up enough but I have the bump on the back of my skull and a pronounced ridge on the back of my four front teeth.
LOL. Sounds to me like the fault lies with some amorous Melungeon in your family's past. Seriously, though, the shovel teeth could come from your Cherokee or Choctaw side, as it's also an Asian/Indian trait. Not sure about the lump.