Page 59 - The Dinosaur Book and Other Wonders of the Prehistoric World (DK-Smithsonian)

The first dinosaurs evolved during the Triassic Period, but and teeth and were capable of overpowering and eating
they were not the giant, ruling reptiles that we are familiar any animal they might encounter. Arizonasaurus belonged
with. The Triassic world was ruled by reptiles of a different to a group of archosaurs that had tall “sails” on their backs,
type—animals like Arizonasaurus. They were archosaurs, as supported by bones extending up from the spine. The function
were the dinosaurs, but had evolved along different lines to of the sail is uncertain, but it may have been important during
resemble high-walking crocodiles. Many had massive jaws displays to rival animals of the same species.

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