Reconstructing fossil sharks is a difficult task. These fish have skeletons of cartilage rather than bone, and extinct species typically left only teeth and the occasional vertebra in the fossil record. The largest of these predatory fish swam the seas between about 28 and 1.5 million years ago: Carcharocles megalodon, a distant cousin of the great white shark. Calculations based on the seven-inch teeth of this giant yield maximum lengths of about 50 to 55 feet, and the prehistoric predator may have had one of the most powerful bites of all time. Estimates made in 2008 suggested that Carcharocles megalodon could bite prey with a force of more than 11 tons, several times the estimated bite force of Tyrannosaurus rex.