Ornithischia

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Ornithischia

[‚ȯr·nə′this·kē·ə]
(paleontology)
An order of extinct terrestrial reptiles, popularly known as dinosaurs; distinguished by a four-pronged pelvis, and a median, toothless predentary bone at the front of the lower jaw.

Ornithischia

 

an order of fossil reptiles of the superorder Dinosauria. The pubic bone of the tetraradiate pelvis had a developed posterior appendage (as in birds). The anterior, toothless part of the jaws was clad in a horny jacket and resembled a bill. The teeth were laterally compressed, with leaflike crowns. The distal phalanges of the digits in late ornithischians were flattened into hooves. The reptiles were herbivorous, with the earliest ones possibly being omnivorous. Many possessed defensive adaptations in the form of cutaneous scutella, spines, or horns. There were six (or four) suborders, including Stegosau-ria, Ankylosauria, and Ceratopsia. Ornithischians lived in the Jurassic and Cretaceous periods.

References in periodicals archive ?
Olsen and Baird (1986) argued on phylogenetic grounds that Atreipus was made by either an ornithischian or a member of the sister-group of Dinosauria, which we would now term a non-dinosaurian dinosauromorph.
In recent years, scientists have found evidence of bristle- and quill-like strands--perhaps early versions of feathers--that speckled the hides of ornithischian dinosaurs.
When they analyzed the tracks, the researchers determined that ornithischians changed their way of walking as surface conditions changed.
Second, this Maastrichtian Marilia Formation fauna, when considered in the light of the Late Cretaceous discoveries, was different by the lack of ornithischian records in Brazil, but which are found in Argentina.
It means that feathers may have evolved, or developed over a long period of time, from structures on an ancestor of both saurichian and ornithischian dinosaurs.
34C; impressions of teeth: YPM VP 008668, VP 008691) closely resemble those of the teeth of the basal ornithischian dinosaur Lesothosaurus diagnosticus from the Upper Elliot Formation of southern Africa (Sereno 1991).
In North America, for instance, sauropodomorphs and ornithischians didn't even show up until after the Triassic was over, Irmis reports in an upcoming issue of Earth and Environmental Science Transactions of the Royal Society of Edinburgh.
Olsen and Baird (1986) argued that either an early ornithischian dinosaur or a non-dinosaurian archosaur converging on ornithischians in the structure of its feet left the distinctive tracks of Atreipus.
Dinosaurs are divided into two main orders: saurischians, which have forward-pointing pubic bones, and ornithischians, which have backward-pointing pubic bones.