Which one is the alligator and which one is the crocodile? Hint: nearly all of the crocodile's teeth stay on the outside of the mouth when it is closed. The upper and lower teeth showing makes them look like they are smiling. The alligator, on the other hand, has a slight overbite with the bottom teeth fitting inside the top teeth.
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Take a look at mammal mandibles and see if you can determine which mammal belongs to which mandible.