Turtles the size of a car once roamed the Earth. Scientists just found their fossils.

By Reis Thebault In the swamps of northern South America some 10 million years ago, quotidian life-or-death battles unfolded at epic scale. Giant caimans, in the same family as alligators, stalked the wetlands of modern-day Venezuela and Colombia, slinking along at 30-feet, snout to tail. Among their most formidable prey: the Stupendemys geographicus, a colossal …