Alligator Snappers vs. Common Snappers! These two turtles are wildly different. Alligator snapping turtles look straight out of the prehistoric past—with spiky, ridged shells, giant blocky heads, and the title of largest freshwater turtle in the world. They’re also now listed as threatened in Illinois. Common snapping turtles are the ones most of us see in Illinois—smoother shells, smaller heads, and much smaller bodies overall. Their populations are generally stable across North America. Don't