Dinosaurs first appeared between 235 and 65 million years ago in a time known as the mesozoic era. This was long before the first humans. Scientists divide the mesozoic era into three periods: Triassic, Jurassic and Cretaceous. A dinosaur the size of a labrador retriever was on the earth 243 million years ago, suggesting the very first reptiles were born earlier than thought. Scientists who identified the new species called Nyasasaurus believe it may have been the first dinosaur to have ever lived.The biggest dinosaur that will eat you was the Spinosaurus it had a sail on its back and weighed 7,000-21,000 pounds its length is 13-18m it lived 112 million years ago to 93 million years ago. The name spinosaurus meaning “spine lizard” is a dinosaur that lived in what is now known as North Africa. The size isn’t the only thing amazing about the Spinosaurus it had a sail on its back because it is both a land and sea creature it uses its sail to glide across the water to catch fish. There is a spinosaurus called the aegyptiacus and a marocranus which are two different Spinosauruses.The tiniest dinosaur was the Compsognathus meaning “pretty jaw” was 1m (3ft) long and weighed 6.5 pounds, it was slightly larger than a chicken. It lived during the jurassic period and ate small animals including bugs and lizards. They can run 40 mph outrun by 5 mph an ostrich they live in what is now known as Europe. Paleontologists found two well preserved fossils one in Germany and the other in France. The Compsognathus also holds the distinction of being the first dinosaur to be portrayed with feathers.The smartest dinosaur is the Troodon it has a big brain for it’s small size and was among the smartest dinosaurs. It’s brain is bigger than ones found in living reptiles, so it may have been as intelligent as modern birds which have a similar brain size. Troodons name means “wounding tooth” they have curved and serrated teeth also a Troodon could have been an omnivore but is called a carnivore. A Troodon can run 30mph-40mph weighs 110 pounds 7.9 feet in length and height is 3 feet. Fossils have been found in (Alberta and USA (Montana and Wyoming)The first Troodon fossil was found by Ferdinand V.hayden in 1855.Dinosaurs died after a deadly asteroid strike 65 million years ago. An asteroid the size of a mountain was hurtling towards earth at 64,000 km an hour. For a few fleeting moments, a fireball that looks bigger than the sun flies through the sky. An instant later, the asteroid slams into earth with an explosive yield estimated at over 100 trillion tons of TNT, that’s insane. The impact penetrates the earth’s crust reaching several miles into the ground the explosion wipes out every dinosaur except the Birds. The birds still live with us today and are still classified as dinosaurs.