Historically, most indeterminate ornithischian bipeds were lumped in as ornithopods. Jeholosaurus is a genus of ornithischian dinosaur from the Early Cretaceous Period. "Polacanthus" was a quadrupedal ornithischian or "bird-hipped" dinosaur. Sauropodomorphs and ornithischian dinosaurs were herbivores with diverse adaptations for feeding biomechanics. The clavicle was present in saurischian dinosaurs but largely absent in ornithischian dinosaurs. The trackmaker of "Atreipus" prints was a quadrupedal ornithischian. "Sinopeltosaurus" is a dubious genus of extinct scelidosaurid ornithischian dinosaur described by Roman Ulansky. The largest ornithischian dinosaur was probably the hadrosaurid "Shantungosaurus giganteus" which measured . So far no evidence of air sacs has been found in ornithischian dinosaurs. The skull of "Psittacosaurus" is highly modified compared to other ornithischian dinosaurs of its time. Unlike birds, the ornithischian pubis also usually had an additional forward-pointing process. The smallest known ornithischian is "Fruitadens haagarorum". Iguanodont ornithischian remains have reportedly also been found. It was the oldest ornithischian known until the description of "Geranosaurus" in 1911. Indeterminate ornithischian remains located in Arizona, USA.