How big were Dinosaurs?

The biggest dinosaurs were the Sauropods that lived during the late Jurassic and Cretaceous periods. These animals had massive bodies, very long necks and tails. They used their long necks to reach out and up to masses of vegetation, of which they needed to eat lots of to survive. Many were over 30m long and weighed in excess of 75 tonnes. The Sauropods are the biggest land animals ever discovered.
The smallest dinosaurs were about the size of birds. Compsognathus was about 60cm long and weighed about 3kg.
The fastest dinosaurs would have been the bird-like bipedal Theropods, such as Gallimimus and Ornithomimus, that looked like modern day Ostriches.
The slowest dinosaur would probably have been Stegosaurus, with a very small brain and cumbersome body.
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