Dinosaurs may be dead and gone, but can a living reptile now help uncover secrets of the dinosaurs' lost world? Green iguanas, adorned with impressive spikes and claws, were once cast as dinosaurs in B movies. Although they are not directly descended from the dinosaurs, new research reveals that the social lives of these modern lizards may show us how the dinosaurs behaved. David Attenborough takes us deep into the jungles of Central America and reveals a chilling cast of prehistoric-looking reptiles locked into battles every bit as dramatic as those played out by the dinosaurs.