It isn't hard to imagine the world full of dinosaurs, even though these extinct animals haven't walked the earth for millions of years. Learn all about dinosaurs, including early dinosaur discoveries, dinosaur fossils, and dinosaur extinction.
  • About Dinosaurs
  • Early Triassic & Jurassic Dinosaurs
  • Middle & Late Jurassic Dinosaurs
  • Early Cretaceous Dinosaurs
  • Late Cretaceous Dinosaurs


Acrocanthosaurus was a sauropod of spectacular proportions. In some ways it looked like many other meat-eating dinosaurs, but it had a sail along its back. See pictures and learn more about this dinosaur.

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Gallimimus ("chicken mimic") was the largest of the ornithomimids (the "ostrich dinosaurs") known. It has been found only in the Late Cretaceous Nemegt Formation of Mongolia. Learn more about the Gallimimus and other Late Cretaceous dinosaurs.


Segnosaurus galbinensis, or "slow lizard from Galbin" (a region of the Gobi Desert), was first described by Mongolian paleontologist Altangerel Perle in 1979. It was an unusual saurischian that he classified in its own family, the Segnosauridae.

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