Dinosaurs, often referred to as "dinos," were a diverse group of reptiles that roamed the Earth during the Mesozoic Era, which lasted from about 252 to 66 million years ago. They varied greatly in size, shape, and diet, with some being herbivores, like Brachiosaurus, and others being carnivores, like Tyrannosaurus rex. Dinosaurs are known for their unique adaptations, such as long necks or sharp teeth. The extinction of dinosaurs occurred approximately 66 million years ago, likely due to a combination of volcanic activity and a massive asteroid impact. This event led to significant changes in the Earth's climate and ecosystems. Today, birds are considered the closest living relatives of dinosaurs, sharing many characteristics with their ancient ancestors.