Evolution of Dinosaurs
DAWN OF THE DINOSAURS
When did dinosaurs develop?
The first dinosaurs developed from other reptiles about 230 million years ago. At this, the world looked very different. There were no birds or mammals, and, although there were ferns and trees, there were no grasses or flowering plants. Vast areas were desert. Dinosaurs dominated the world for 150 million years.
Why did dinosaurs get so big?
Scientists are not certain why some dinosaurs got so big. Dinosaurs may have developed into larger, stronger and faster animals in order to complete with each other for food. Sauropods were by far the biggest dinosaurs, with long necks to reach leaves at the tops of tall trees. The carnivores may simply have evolved into larger beasts to be able to catch them.
Did any dinosaurs live in water?
No, dinosaurs only lived on land. Some reptiles did live in the sea, including Plesiosaurus, which was not related to dinosaurs. This large carnivorous animal had a long neck and sharp teeth to catch fish. Other reptiles, such as the pterosaurs, could fly. They had wings made of skin, similar to those of bats.
Scientists may never be sure what colour dinosaurs were or even whether some had hair.
What was the smallest dinosaurs?
The smallest dinosaurs were not much bigger than a chicken. Saltopus, which lived about 220 million years ago, was about 60 centimeters long and scurried along the ground eating insects. Compsognathus, which means 'pretty jaw', lived about 150 million years ago and was only about a meter long.
DINOSAUR RULE
Which dinosaur waddled?
The giant Megalosaurus dinosaur probably waddled like a duck. Its tail would have swung to and fro as it walked along. Megalosaurus lived in the Jurassic period, when dinosaurs dominated the Earth. It had vicious claws and saw-edged teeth for cutting into the flesh of its prey.
Why did Stegosaurus have armoured plates?
The rows of armoured plates along Stegosaurus's back probably helped make the dinosaur look bigger to put off predators. Some scientists think that the plates may have been used to display to other stegosaurus. Another group of dinosaur, the ankylosaurs, also had armoured plates. They even had hard shells on their eyelids.
Argentinosaurus and many other dinosaurs were huge, but the blue whale is bigger than any of them.
How fast could dinosaur run?
Some dinosaurs, such as Gallimimus, may have run up to 60 kilometers an hour. Gallimimus was an ostrich like dinosaur that probably lived in groups. It had a small head with a toothless, beaked mouth and probably ate insects, small animals and eggs. It had long legs tail that helped it to keep its balance when making fast, sharp turns.
Did dinosaurs hunt in packs?
Yes, some dinosaurs might have hunted in packs, working together in order to catch and bring down larger dinosaurs. Giganotosaurus was one of the biggest meat-eating dinosaurs ever. It could hunt alone, but to catch a full grown Argentinosaurus, perhaps the largest dinosaur that ever lived, packs of six or more Giganotosaurus worked together.
THE LAST DINOSAURS
Which dinosaur had the biggest claws?
Therizinosaurus had the biggest claws. This dinosaur had three curved claws on each of its arms, measuring up to a meter long. It was a herbivore, or plant eater, and it may have used its claws to pull down branches from high trees to eat the bark and leaves.
Some of the common later dinosaurs were the hadrosaurs. They had a toothless beak that looked like that of a duck and are called duck-billed dinosaurs.
How many teeth did Tyrannosaurus rex have?
Tyrannosaurus rex had over 60 thick, cone-shaped teeth in its meter-long mouth. Some of the teeth were sharp as knives and used to slice off flesh. Others were shaped for crunching bones, so that the animals could eat the bone marrow inside the bones. Although Tyrannosaurus rex is often seen as a fierce and successful hunter, it may also have been a scavenger; eating animals it found that were already dead.
When did Triceratops use its home?
Triceratops probably used its horns to protect itself. When attacked, it probably stood its ground and used them to injure predators. At about 9 meters long, Triceratops was a large plant eater. It may even have been able to take on the mightily Tyrannosaurus rex. Scientists think that the bony frill around their necks enabled the different Triceratops in a herd to tell each other apart.
Why did dinosaurs die out?
There are several theories about why dinosaurs died out about 65 million years ago. The main one is that a giant asteroid crashed into Earth around this time. The impact would have created dust, fires, tsunamis (giant waves) and volcanic eruptions that caused a huge changes in the planet's climate. It seems likely that the world became freezing cold, and the dinosaurs simply could not survive in the icy conditions.