I totally see the difference, now that they’re side by side. Some viewers might not have noticed, but the crocodile was facing right and the alligator is facing left. So, when faced with a medium-largish swamp dinosaur with hungry eyes and a wide open mouth, hold your hands out in front of you with thumb and forefinger extended: if the beast is pointed at the hand forming an L, you’ve got an alligator and you should run but you’re probably going to die; if it’s facing the backward L, that’s a crocodile, and you should definitely run but you’re almost certainly going to die.
Actually, the alligator hides ALL his teeth.
“When their snouts are shut, crocodiles look like they’re flashing a toothy grin, as the fourth tooth on each side of the lower jaw sticks up over the upper lip. For alligators, like this one, the upper jaw is wider than the lower one, so when they close their mouths, all their teeth are hidden.” http://www.livescience.com/15529-alligators-crocodiles-images.html