We’re all familiar with those awesome armored giants of the Jurassic and Cretaceous periods – Stegosaurus and Ankylosaurus – and their amazing, weaponized tails. But why aren’t similar weaponized tails found in animals living today? In a study covering 300 million years of evolutionary history, researchers from North Carolina State University and the North Carolina Museum of Natural Sciences found four necessary components to tail weapon development: size, armor, herbivory and thoracic stiffness.