See also the common snapping turtle skull for comparison.
These are pictures of a fossil alligator snapping turtle skull. The skull, which measures 9 inches across, was found by Michael E. Damron in East Central Arkansas.
This alligator snapping turtle, had it been alive, would have had a total weight of possibly 110-120 pounds. The males are much larger than females. Generally a slow growing species, they can reach over 200 pounds at 50 to 70 years.
(captive animals tend to grow much fatter and become heavier as the result than their wild cousins at the same age. The exact age of a turtle can't be judged only by its weight)