The world was very different at the time of the dinosaurs; however the dinosaurs were around for such a long time that the world changed considerably over this period.
1. Triassic period
The Triassic Period was the first period of the Mesozoic Era, and ran from 248 to 200 million years ago. A lot happened to Earth and its life-forms during the Triassic but the most celebrated event was the evolution of dinosaurs. These remarkable creatures emerged around 230 MYA and dominated the planet throughout the Mesozoic Era.
Planet Earth looked very different at the beginning of the Triassic Period. There was just one landmass, a huge continent known as Pangaea. It stretched from pole to pole and included a vast desert at its centre. There was no grass, although ferns and mosses provided ground-cover in less arid areas. Pangaea began to break up in the mid-Triassic.
2. Jurassic period
The Triassic period was followed by the Jurassic period, when dinosaurs evolved to greater sizes and became the dominant animals on Earth. During this time, the Pangaea continent began to break up, eventually forming the continents we have today. This separated different species of dinosaurs so they could evolve independently.
The Jurassic period ended with a minor mass extinction, and many dinosaur species were wiped out, including Stegosaurus and many sauropod species, like Diplodocus. Sauropods were the largest known dinosaurs and the largest known animals to have ever lived on land.
Sauropods may have evolved to such large sizes in order to aid with digestion. They could survive on food that was less nutritious than that eaten by smaller animals because they spent more time digesting it.
The largest sauropods were so tall that a person could walk underneath their stomachs. Sauroposeidon, for example, were about 18 meters (59 feet) tall. This is around the height of a five-story building, and almost four times the height of Paraceratherium, the largest mammal to ever live on land.
Sauroposeidon were also about 34 meters (112 feet) long, which is about 10 meters (33 feet) longer than blue whales. They lived about 110 million years ago in the early Cretaceous period.
3. Cretaceous period
The Jurassic period was followed by the Cretaceous period, which began about 145 million years ago. During this time, plants began to flower and bees evolved.
Grass evolved about 70 million years ago and dinosaurs like Tyrannosaurus Rex and Triceratops evolved about 68 million years ago.
The Cretaceous period ended about 66 million years ago after the fifth mass extinction, the Cretaceous event, wiped out 76% of species on Earth.
How do we know?
The remains of preserved dead life forms, or signs of life forms life faeces or footprints, are said to be fossilized. This can happen if a body, plant, or sign of life is trapped in tar or amber, frozen, or mummified. It can also happen if one of these things is covered in water and a wet substance like mud falls onto it. If more and more layers of mud – sediments – cover it, the pressure causes the lower layers to harden, and the body is eventually replaced by rock
There’s evidence that fossilized dinosaur bones have been discovered for thousands of years. In China, dinosaur bones were first thought to be dragon bones, and in Europe, they were thought to belong to giants and other life forms found in the bible
Fossils were usually found in layers of sediments, known as strata, and in the 1790s, British geologist William Smith suggested that the bottom layers of strata are older than the top layers. This meant that fossils in the same layer were probably the same age.
Dinosaurs were discussed scientifically in the 1800s, after remains were found in England in the 1820s and 1830s. British biologist and paleontologist Richard Owen used the term Dinosaurian to describe them in 1842. This meant ‘terrible lizard’, although we now know that dinosaurs are not lizards, and they are not descended from them.
American paleontologist William Parker Foulke identified the first American dinosaur fossil in New Jersey in 1858. Unlike previous dinosaur fossils, and unlike modern lizards, this dinosaur clearly walked on two feet.
Shortly after this, American paleontologists Edward Drinker Cope and Othniel Charles Marsh began a race to discover new American dinosaurs. This became known as the ‘Bone Wars’, and did not end until Cope died in 1897. Cope and Marsh discovered over 140 new dinosaur species between them, although their methods were extreme and sometimes destroyed sites .
At least thousands of dinosaur fossils have been found since then, appearing on all continents on Earth, and scientists have used this as a starting point in order to understand how non-avian dinosaurs looked and behaved.
Scientists can gain knowledge from fossilized bones, tracks, eggs, and faeces, as well as soft tissues, internal organs, skins, and feathers, although these are rarer. Theories are then developed from this information using the laws of physics, and our current knowledge of the physical and mental behaviors of animals.
We may never gain a complete picture, however, because the vast majority of animals are not fossilized. On top of this, some fossils are difficult to find and the majority of fossils are probably still far below the ground.
It may also be impossible to know if the images we create of extinct species are correct because most fossils do not contain complete skeletons or softer parts, like organs, fat, hair, fur, feathers, or external objects like spider’s webs. Many animals look vastly different to what we would expect from their skeletons.