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Prehistoric

What Is a Prehistoric Animal?

Prehistoric animals are all organisms that walked—or swam, crawled, slithered, or flew—on Earth more than 5,500 years ago, before humans started recording history. The earliest known remains date to the Cambrian era, about 600 million years ago, although simple-celled organisms have been around much longer. Crustaceans, flying reptiles, dinosaurs, woolly mammoths, and saber-toothed tigers are just a few of the hundreds of millions of prehistoric animals that once lived on Earth. Paleontologists know about these animals by studying fossils, animal remains that have been preserved in rock.

Prehistoric Animal Features

Image: A bacculite

Photo Gallery: Sea Monsters

Download desktop wallpapers of prehistoric sea monsters and get a glimpse of what these animals looked like millions of years ago.

Image: T. rex dinosaur

Tyrannosaurus Rex

Everything about this predator—from its sharp claws to its serrated teeth—was designed for maximum bone-tearing action.

Image: Troodon formosus dinosaur

Troodon Formosus

Scientists say this animal was likely one of the smartest dinosaurs to ever walk the Earth—and it may be a critical link in prehistoric evolution.

Image: Dinosaur concept

What’s Wrong With This Picture?

See past National Geographic dinosaur illustrations and listen to Thomas Holtz, a University of Maryland paleontologist, discuss what we’ve learned since our 20th-century dinosaur coverage.

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