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When the fossilized skeleton of Giganotosaurus was discovered in 1995, many people got very excited. It was a huge, meat-eating dinosaur, even larger than Tyrannosaurus rex. Giganotosaurus means "giant southern lizard" because it was found in Argentina, South America. Only 70 percent of the skeleton was found, but it was enough to re-build this giant creature. It was about 45 feet long: that’s about the size of a locomotive. It stood 12 feet tall at the hips. It weighed about 8 tons. It was five feet longer than Tyrannosaurus rex and about two tons heavier. Giganotosaurus wasn’t a very intelligent dinosaur. There wasn’t very much space in its skull, which is how we measure a dinosaur’s intelligence. Its brain was about the size of a banana.

Giganotosaurus walked on two thick, powerful legs and had enormous jaws. Its teeth were 8 inches long and serrated like the edge of a saw. Its skull was six feet long. Giganotosaurus lived about 100 million years ago. Giganotosaurus may have hunted animals much larger than itself, such as the huge sauropod plant-eaters like Brontosaurus and Diplodocus. The skeleton of a 75 foot-long herbivore was found right next to the fossil of a Giganotosaurus. Paleontologists think that Giganotosaurus was hunting a creature more than twice its own size. It had a long, skinny tail which was useful for balance. This means it could turn quickly while running and jumping. Its tail shot straight out behind it and was kept far off the ground.

Several skeletons of Giganotosaurus were found together in the same place. That means that they probably moved around in groups. But Giganotosaurus was probably not a very fast runner. Big bipedal dinosaurs were so heavy that if they fell they could really hurt themselves. Paleontologists studying Giganotosaurus have found many skeletons with broken ribs and cracked shoulder bones. When they looked at the bones closely, they saw that the broken pieces healed very quickly. Giganotosaurus probably fell while it was running, and the heavy weight of its body crushed its own bones.

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