Compsognathus, a carnivore from the late Jurassic period (131 million years ago), was about the size of a chicken and measured, at most, 35 inches (89 centimeters) from the tip of its snout to the tip of its tail. The average weight was about 6 pounds 8 ounces (3 kilograms), but they could be as much as 15 pounds (6.8 kilograms).

The largest species for which a whole skeleton is known is Brachiosaurus. A specimen in the Humboldt Museum in Berlin measures 72.75 feet (22.2 meters) long and 46 feet (14 meters) high. It weighed an estimated 34.7 tons (31,480 kilograms). Brachiosaurus was a four-footed, plant-eating dinosaur with a long neck and a long tail and lived from about 121 to 155 million years ago.