Dinosaurs lived on Earth 65.5 million years ago. The first dinosaur was named Megalosaurus. Paleontologists study Dinosaurs. Some dinosaurs were smaller than chickens, and there were dinosaurs of all different colors. 

Allosaurus had very weak jaws however, they had long and mobile necks and they could open their jaws over 90 degrees! They were carnivores which means they eat meat. This dinosaur was about 16.5 feet tall, 28 feet long, and weighed about 3,800 pounds. 

Brachiosaurus were the largest dinosaurs ever. They were herbivores which means they eat plants. This dinosaur was 42 feet tall, 59-72 feet long, and weighed 99,000 pounds which is as much as 20 African elephants! 

Chilesaurus is the same group of dinosaurs as Tyrannosaurus Rex, but they only ate plants with a beak and leaf-shaped teeth. This dinosaur was 10.5 feet tall, 10 feet long, and weighed about 200-300 pounds. 

Diplodocus are the longest dinosaurs ever. They were herbivores which means they only eat plants. This dinosaur was 15 feet tall, 90 feet long, and weighed 67,200 pounds. 

Eoraptor is the oldest known dinosaur. They were omnivores which means they eat plants and meat. This dinosaur was 30 centimeters tall, 3 feet long, and weighed 22 pounds. 

Falcarius were hunted by Utahraptors and Velociraptors. They were herbivores which means they eat plants. This dinosaur was 3.9 feet tall, 12-13 feet long, and weighed 220 pounds. 

Gigantosaurus could run 31 miles per hour. They were carnivores which means they eat meat. This dinosaur was about 23 feet tall, 40-43 feet long, and weighed 15,400–17,600 pounds.

Hylaeosaurus were the first dinosaurs that were discovered with hard, armored skin. They were herbivores which means they eat plants. This dinosaur was 6 feet tall, 9.8-25 feet long, and weighed 4,928 pounds. 

Iguanodon have large thumb spikes they used to protect themselves from predators. They are herbivores which means they eat plants. This dinosaur was 8.9 feet tall, 33 feet long, and weighed 8,000-11,000 pounds.