Ornithischia

Ornithischia is a major clade of dinosaurs that includes a range of species with bird-like features. These dinosaurs had beaked mouths, sat on their hind legs, and had well-developed hip joints. They also had a distinct pelvic structure with a predentary bone and a process of air sacs connected to the lungs, similar to that of modern birds. Ornithischian dinosaurs lived during the Mesozoic era and helped shape the ecological landscape of the time. They are seen as a successful branch of dinosaur evolution and are represented in the fossil record by a wide variety of species. Ornithischians were herbivorous and played an important role in controlling the vegetation of the Mesozoic era and were part of the large food web that included large herbivores and carnivores. Some species achieved great size and were among the largest land animals of their time. Ornithischian dinosaurs are a significant part of paleontology and their fossils continue to enlighten us about the biology, behavior, and evolution of dinosaurs.