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|Major Dinosaur Families||Saurischian Dinosaurs
|"Lizard-Hipped" dinosaurs (Saurischians) had a hip structure similar to that of lizards. Oddly enough, these "Lizard-Hipped" dinosaurs were the ancestors of the birds.
Other anatomical features that characterize saurischians include an opening below the nostrils (called the subnarial foramen), an elongation on some neck vertebrae (resulting in long necks), a big thumb, an extra, wedge-shaped ankle bone (the astragalus), and many other distinctive features.
The oldest known dinosaurs are Saurischians from the mid-Triassic period, about 230 million years ago.
Saurischians included both meat and plant eaters.
|"Bird-Hipped" dinosaurs (Ornithischians) had a hip structure that is similar to that of birds (but did not lead to the birds).
They also had beak-like bone in the lower jaw in front of the teeth, called a predentary. Other anatomical differences include a narrow palebral (the bone that crosses the outside of the eye socket), and bony (ossified) tendons above the sacral area of the vertebrae.
The Ornithischian dinosaurs were vegetarians and included plated, armored, and horned dinosaurs.
|Example of "Lizard-Hipped" dinosaurs include:||Example of "Bird-Hipped" dinosaurs include:
|A cladogram of reptilia
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