Ornithischia



Ornithischia is one of the two major groups of dinosaurs, the other being Saurischia. Though it is saurischians that are the ancestors of birds, the name "Ornithischia" means "bird-hipped" because of the several similarities in the hip structure of birds and ornithischians. The name was coined in 1888 by Seeley. Ornithischians were a very diverse clade of organisms, with many different genera, including, but not limited to Judiceratops, Prenocephale, Edmontosaurus, Goyocephale, Homalocephale, Wuerhosaurus, Muttaburrasaurus, Atlascopcosaurus, and Anchiceratops.'' These are just a few examples of the many different varieties of ornithischians.

Classification
Ornithischians are classified into three main groups plus several basal species - Thyreophora, Neornithischia and Heterodontosauridae.

Thyreophorans include the so-called armored dinosaur groups Stegosauria and Ankylosauria, along with some basal species like possibly Scutellosaurus.

Neornithischians are by far the most diverse group, subdivided into ornithopods (iguanodonts, hadrosaurs) and marginocephalians (pachycephalosaurians and ceratopsians). Most ornithischians are neornithischians and this group also includes many of the most common dinosaurs during the Cretaceous period. Hadrosaurs, the most succesful and derived of the ornithopods, are among the best-fossilized dinosaur groups known, with countless skin impressions and even a couple hadrosaur "mummies" known.

Heterodontosaurids are a group of small, bipedal ornithischian dinosaurs that lived from the Late Triassic to the Early Cretaceous. There are only a few genera known, but among them is Tianyulong, a partly feathered dinosaur.

Several other dinosaurs are also included within the group Ornithischia but do not fall into any of the three major groups. Some of these are Eocursor, Pisanosaurus, and Fabrosaurus.