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'''Ornithischia''' (also called: '''Predentata''') is an order of [[Dinosaur|Dinosaurs]].
'''Ornithischia''' or '''Predentata''' is one of two major orders of [[Dinosaur|dinosaurs]], and includes both bipedal and quadrupedal herbivorous animals, all of which share a pelvic structure similar to that of birds.
==Description==
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<ref>http://users.tamuk.edu/kfjab02/dinos/VPORNITHO.htm</ref>. All ornithischians also bear a beak due to the rostral tip of premaxilla being toothless.
==Taxonomy==
==Taxonomy==
:::Family Heterodontosauridae
:::Family Heterodontosauridae
::Infraorder Ornithopoda - duck-billed dinosaurs
::Infraorder Ornithopoda - duck-billed dinosaurs
:::Family Camptosauridae
:::Family Dryosauridae
:::Family Dryosauridae
:::Family Camptosauridae
:::Family Hadrosauridae
:::Family Hypsilophodontidae
:::Family Hypsilophodontidae
:::Family Iguanodontidae
:::Family Iguanodontidae
::Infraorder Hypsilophodontia - small ornithopod dinosaurs
::Infraorder Hypsilophodontia - small ornithopod dinosaurs
:::Family Protoceratopsidae
:::Family Protoceratopsidae
:::Family Psittacosauridae
:::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.
==References==
<small><references/></small>
[[Category:Dinosaurs]]
[[Category:Dinosaurs]]