Dinosaurs were a diverse group of reptiles that dominated Earth for over 160 million years, from the Late Triassic period (around 230 million years ago) until the end of the Cretaceous period (about 65 million years ago). They came in various shapes and sizes, from small, agile predators like Velociraptors to massive herbivores like Diplodocus and the iconic Tyrannosaurus rex. These ancient creatures ruled the prehistoric world before a catastrophic event, likely an asteroid impact, led to their mass extinction, paving the way for the rise of mammals and the world as we know it today.