Dinosaurs were not the first living things. Life began billions of years before them with the simplest living thing – the single cell. Gradually animals with many cells, such as reptiles and mammals, evolved.
First Life: 3,000 Million Years Ago
The first living things on Earth were very simple, single-celled forms of life. There were bacteria and a type of algae called blue-greens. Fossils of blue-greens and bacteria have been found in rocks 3,000 million years old. These hot springs in Yellowstone Park, North America, contain bacteria and simple algae.
Life In The Sea: 600 – 530 Million Years Ago
Before fish, the seas were home to other creatures. Many of them were like sea animals that live today. There were jellyfish, shellfish called brachiopods and many sorts of sea worm. One type of of animal that hasn’t survived is the trilobite. Trilobites were sea creatures with hard bodies like armour, which were jointed so they could move. They had legs like those of shrimps. To protect themselves some could curl up into a ball, like woodlouse.
Leafless Plants and Insects: 410 – 380 Million Years Ago
The first plants were leafless and flowerless and no more than 4 or 5cm tall. They lived on boggy ground. Through this miniature jungle, scorpions hunted millipedes that fed on the plants.
Fish Teem In The Sea: 390 Million Years Ago
The first animals with backbones were fish. It is thought that sometime during this period Eusthenopteron, a fish that used its front fins to help it “walk”, crawled out of the water to live on land. It was the ancestor of land animals.
Amphibians Rule: 370 – 280 Million Years Ago
Amphibians live on land and in water, where they lay their eggs. Amphibians evolved from fish. At this time in history amphibians were very successful. Some amphibians were quite big. Ichihyosiega was about 1m long. It looked a bit like a fish and had scales and a fin, but it had legs and could walk on land, although it spent most of its time in water.
Reptiles Rule: 310 Million Years Ago
There were more reptiles on land than amphibians. Scientists think that one group of reptiles were the ancestors of mammals. Dimetrodon belonged to this group.
Flying Insects, Towering Forrests: 300 Million Years Ago
Through huge forests flew the first flying insects such as dragonflies. Some of these had vast wing spans up to 70cm across. They were the largest flying insects ever to exist.
Dinosaur Ancestor: 245 Million Years Ago
Archosaur reptiles, some of which were rather like modern crocodiles, were among the animals on Earth. Some, such as Euparkeria, may have been the ancestors of the dinosaurs.
The Age of The Dinosaurs Begins: 220 Million Years Ago
The first true dinosaurs appeared and began to spread across the planet. They walked on two legs, had sharp teeth, and were built for speed. Small meat-eaters like Eoraptor hunted in packs, marking the start of the mighty dinosaur age.