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Ornithischia

Ornithischia (/ɔːrnᵻˈθɪskiə/ or-ni-thiss-kee-ə) is an extinct clade of herbivorous dinosaurs characterized by a pelvic structure similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek ornitheos (ορνιθειος) meaning "of a bird" and ischion (ισχιον) meaning "'hip joint". Birds are members of the saurischian, or "lizard-hipped", dinosaurs.

Ornithischia is an extremely well supported clade and is one of the two major groups in Dinosauria. Many characters define the group though most are thought to be linked to herbivory.

Ornithischians with well known anatomical adaptations include the ceratopsians or "horn-faced" dinosaurs (e.g. Triceratops), armored dinosaurs ( Thyreophera) such as stegosaurs and ankylosaurs, pachycephalosaurids and the ornithopods. There is strong evidence that certain groups of ornithischians lived in herds and there is some evidence to suggest certain species may have cared for their young. Additionally, there is much debate over whether filamentous integumentary structures displayed in specimens of the genus Tianyulong and bristle-like integumentary structures displayed in specimens of the genus Psittacosaurus may have been precursors to feathers and, if so, whether later ornithischians may have been feathered.

Usage examples of "ornithischia".

In the Saurischia, this indentation is large and carries at least one fenestra, whereas in the Ornithischia the fossa as well as its fenestra are significantly reduced or missing.

Now we know that they fall into two long-separated orders: the Saurischia and the Ornithischia, no more closely related than, say, we are to bats.

Today, this view has been modified radically, and almost all researchers believe that both groups, Ornithischia and Saurischia, are closely related and that all dinosaurs form a socalled monophyletic group, originating from a common ancestor.

This tooth structure provides a clear proof that all members of the Ornithischia were herbivorous.

In the course of evolution, these defining features of the Saurischia and the Ornithischia underwent many modifications, and the state of these changes together with appearance of other, new anatomic features characterize different subgroups of the two main dinosaurian lines.

Much debate, however, dealt with mutual relationships among smaller groups within the Ornithischia, and especially the role played by the Ornithopoda in the development of the bird-hipped dinosaurs.

The basic differences between fabrosaurids and all other members of the Ornithischia is that the cheeks are missing, though they are present in all other reptiles, recent reptiles included.

Turning to the terrestrial realm, reptiles found largely in this group of habitats ate the squamates and the two groups of dinosaurs, the Ornithischia and Saurischia.