Ornithischia is a major group of dinosaurs characterized by their bird-like hips. This group includes a variety of herbivorous dinosaurs, such as Stegosaurus, Triceratops, and Ankylosaurus. Ornithischians were primarily plant-eaters and had unique adaptations for grazing and browsing. These dinosaurs lived during the Mesozoic Era, thriving in diverse environments. Ornithischians are known for their distinctive features, such as armor plating and elaborate crests. They played a significant role in prehistoric ecosystems and are an important part of the evolutionary history of dinosaurs.