Late Early Eocene, Lost Cabin Age. Green River Formation. Southwestern Wyoming, USA. The armor-plated garfish is a classic living fossil – a creatur alive today that has changed little from the time of the tyrannosaurs, 90 million years ago. The alligator gar has diamond-shaped, armor-plated scales – each one made from a double layer of bone. The outer layer is super-dense and so hard that even big bull alligators have a hard time biting through it. The inner layer is spongier and attached to sheet of connective tissue that works like a shock absorber. All the scales are knit together with a tongue-in-groove joints, allowing the fish to twist and flex. Gars seem to be bulletproof from extinction, too. Mass die-offs struck dinosaurs 65 million years ago and then struck giant mammals several times. But each catastrophe left the gars unscathed.