The skin between the two botton jaw halves is very stretchy so it can open it\'s mouth very wide, although, apparently not wide enough to swallow a human (due to the shoulders) unless it tries it with the shoulders vertically.
That croc one was on a tv documentary. They discovered that because the hide of the croc, actually I think it was an alligator, is tough, the enzymzes take a long time to break it down. In the meantime the corpse is decomposing and getting bloated, which eventually ruptured the snake from the inside.
I don\'t think that dog is a pitbull. I can just about make out that it\'s an English terrier.