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 Eras are subdivided into Periods, and the Mesozoic Era is divided into three Periods. The table below is an overview of dinosaurs by Period with an emphasis on the dinosaurs found in GSENM.
Mesozoic Era |
Triassic Period |
Began 251 mya (the start of the Mesozoic era)
Ended about 200 mya,
Lasted 51 million years |
- In the late Triassic, about 230 mya, dinosaurs began to develop. During this Period there were huge amphibians and reptiles.
- GSENM does not have dinosaur fossils in its rock strata from this age, so the early years of dinosaur evolution are not represented in the Monument.
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Jurassic Period |
Started about 200 mya
Ended about 144 mya,
Lasted 62 million years. |
- In GSENM there is fossil evidence of stegosaurs and huge sauropods from the Jurassic. These are mostly isolated bones and footprints, not complete skeletons.
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Cretaceous Period |
Followed the Jurassic’s end at 144 mya
Continued through the great extinction of 65 mya.
Lasted 79 million years |
- During these 79 million years an amazing diversity of dinosaurs roamed the area that would later become Grand Staircase-Escalante National Monument.
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