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Scientific classification
Kingdom Information
Domain Eukaryota
Kingdom Animalia
Subkingdom Bilateria
Branch Deuterostomia
Phylum Information
Phylum Chordata
Sub-phylum Vertebrata
Infraphylum Gnathostomata
Class Information
Superclass Tetrapoda
Class Reptilia
Infra-class Archosauromorpha
Order Information
Superorder Dinosauria
Order Ornithischia
Population statistics
Conservation status Extinct

Ornithischia or Predentata is one of two major orders of dinosaurs, and includes both bipedal and quadrupedal herbivorous animals, all of which share a pelvic structure similar to that of birds.


The primary characteristic is the pelvic girdle, comprised of ilium, the ischium, and the pubis. The process of the pubis points to the rear - as in birds - to allow for a long digestive tract. A further shared characteristic is the presence of a predentary bone at the tip of the lower jaw, hence the other name for the order.[1] All ornithischians also bear a beak due to the rostral tip of premaxilla being toothless.


  • Order Ornithischia
Family Pisanosauridae
Family Fabrosauridae
    • Suborder Thyreophora
Infraorder Ankylosauria - armored dinosaurs
Family Ankylosauridae
Family Nodosauridae
Infraorder Scelidosauria - scute-armored dinosaurs
Family Scutellosauridae
Family Scutellosauridae
Infraorder Stegosauria - plate-armored dinosaurs
Family Huayangosauridae
Family Stegosauridae
    • Suborder Cerapoda
Family Heterodontosauridae
Infraorder Ornithopoda - duck-billed dinosaurs
Family Camptosauridae
Family Dryosauridae
Family Hadrosauridae
Family Hypsilophodontidae
Family Iguanodontidae
Infraorder Hypsilophodontia - small ornithopod dinosaurs
Family Hypsilophodontidae
Family Tenontosauridae
Family Thescelosauridae
Infraorder Pachycephalosauria - bone-headed dinosaurs
Family Pachycephalosauridae
Infraorder Ceratopsia - horned dinosaurs
Family Bagaceratopidae
Family Ceratopsidae
Family Chaoyangsauridae
Family Protoceratopsidae
Family Psittacosauridae

Due to head displays, some authorities accept the placement of the ceratopsid and pachycephalosaurid dinosaurs into the recently created suborder Marginocephalia.

Evolutionary claims

Birds are claimed by evolution to be descended from theropod dinosaurs of the other major order Saurischia, due to similar structures in the wrist; despite being different, the "lizard-hipped" pelvic girdle of saurischians is never mentioned as a factor in the ancestry of birds.