order of reptiles (fossil)

Ornithischia is an order of beaked, herbivorous dinosaurs. They are known as the 'bird-hipped' dinosaurs because of their hip structure. However, birds actually descended from the 'lizard-hipped' dinosaurs, the Saurischia. The name "Ornithischia" means "bird-hipped," and birds also have pelvises in which the pubis points backwards.

Temporal range: Upper TriassicUpper Cretaceous, 228–66 mya
Ornithischian pelvic structure (left side)
Scientific classification

Seeley, 1888
Edmontosaurus pelvis (showing ornithischian structure – left side, tail to the right) Oxford University Museum of Natural History

An alternative name for the order is the Predentata, because all of them are beaked herbivorous dinosaurs. The beak is in front of the jaw-bone, the dentary, so it is a 'predentary'. The upper half of the beak is the 'premaxilla' on the end of the upper jaw. The beak is a key adaptation for cropping plants for their food.

Their original (basal) form of locomotion was bipedal. However, from early in their evolutionary history, they were capable of both bipedal and quadrupedal locomotion.[1] Several groups became entirely quadrupedal.[2]

The ornithischia has two sub-orders:


Their vegetarian diet included:

This group of dinosaurs would not be able to reach the taller conifers. The other main group of vegetarian dinosaurs, the sauropodomorphs, were specialists able to reach vegetation on the tall trees.

Related pagesEdit


  1. Wilson J.A; Marsicano C.A. & Smith R.M.H. 2009. Dynamic locomotor capabilities revealed by early dinosaur trackmakers from southern Africa. PLoS ONE 4(10) [1]
  2. Fastovsky, David E. & Weishampel, David B. 2012. Dinosaurs: a concise natural history. Cambridge: Cambridge University Press. ISBN 978-1107276468