Ornithischia, better known simply as the "ornithosaur", is one of the three common orders of dinosaurs (along with Ornithischia and Ornithopteryx). The other two are the Ceratopsidae and the Stegosaurus. Ornithischia was the first order of dinosaurs to survive the Cretaceous geological period, which lasted from the end of the Triassic period to the beginning of the Jurassic period in the Early Jurassic. This is also the place where many modern birds got their name.
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Downvoted due to @hakeemshah96's insincere copy-paste spam compliments.
Downvoted due to @hakeemshah96's insincere copy-paste spam compliments.