Several of my mutant salamander creatures, drawn to the following jaunty tune-

http://www.youtube.com/watch?v=WdVT0EWBtW8&NR=1&feature=fvwp

Here we see two intriguing and often hidden smiles in the front row; To the left, the Pillmander can either manifest an eye on it's head(which is its normal choice) or a mouth instead- there's really no logical explanation as to how this works, much like the nature of Doctor Ai that it got the genes from. To the right, Sal(Bighornmander) almost never smiles wide like that because it makes her look much closer to how dangerous she is. She has 8 flat teeth up front, 4 oversized piercing teeth next, and behind that 4 bony plates(no individual teeth) which are merely serviceable at shredding/grinding- Their main purpose is to lock together and protect her individual teeth during an impact, and with her unique skull she can strike some surprisingly hard surfaces without losing the damage trade, Sufficed to say, anything with a normal skull(even something with a much bigger head) would lose miserably in a head to head collision.