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The Dinosaurs and Prehistoric Animals of Arizona

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Thanks to its location in the southwestern U.S., a fair number of dinosaurs and prehistoric animals have been discovered in the state of Arizona, as listed below. (See an interactive map of dinosaurs and prehistoric animals in the United States.)

1. Ammosaurus

ammosaurus
Heinrich Harder

Although the original fossil of Ammosaurus was discovered in Connecticut (which can use all the help it can get, dinosaur-wise), related fossils have been found in Arizona as well. It may well turn out that this small, slender prosauropod was really a species of Anchisaurus, in which case both Connecticut and Arizona would lose out!

2. Dilophosaurus

dilophosaurus
H. Kyoht Luterman

By far the most famous dinosaur ever to be discovered in Arizona (in 1942), Dilophosaurus was so misrepresented by the first Jurassic Park movie that many people still believe it was poisonous and had an expandable neck frill. Dilophosaurus did, however, possess two prominent head crests, after which this small theropod was named. More about Dilophosaurus

3. Sarahsaurus

sarahsaurus
Matt Colbert and Time Rowe

Named after the Arizona philanthropist Sarah Butler, Sarahsaurus stands out from the dinosaur pack for its unusually strong, muscular hands capped by prominent claws, an odd adaptation for a plant-eating prosauropod. One theory holds that Sarahsaurus was actually omnivorous, and supplemented its vegetable diet with occasional helpings of meat.

4. Segisaurus

segisaurus
Nobu Tamura

The only dinosaur ever to be unearthed in Arizona's Tsegi Canyon, Segisaurus is known from a single, incomplete skeleton--in sharp contrast to its close relative Coelophysis, thousands of specimens of which have been discovered in New Mexico's Ghost Ranch quarry. Still, this meat-eating theropod must have given Coelophysis a run for its Jurassic money!

5. Sonorasaurus

sonorasaurus
Dmitri Bogdanov

What sets Sonorosaurus apart from the sauropod pack is that this dinosaur's remains date from middle Cretaceous North America (about 100 million years ago), a relatively sparse stretch of time for this family of plant-eaters. As you may have guessed, Sonorasaurus' euphonious name derives from Arizona's Sonora Desert, where it was discovered.

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