Ornithopods were a group of herbivorous dinosaurs that lived during the Late Jurassic to the Late Cretaceous periods. They are characterized by their beak-like mouths, which helped them efficiently chew plants. Some well-known ornithopods include Iguanodon and Hadrosaurus, often referred to as "duck-billed dinosaurs" due to their flat, duck-like snouts. These dinosaurs varied in size and shape, ranging from small, bipedal species to larger, quadrupedal forms. Ornithopods were known for their agility and social behavior, often traveling in herds. Their adaptations allowed them to thrive in diverse environments, making them one of the most successful dinosaur groups.