Why is there no land animal as big as dinosaur in the present time?

The Mesozoic Era (250 million years ago) lasted about 200 million years through the Triassic and Jurassic periods, ending with the Cretaceous Era 65 million years ago when a meteorite hit the Earth. With this comes the end of the reign of dinosaurs on earth. The continents were not separate as they are now, the whole world was one continent called Pangea.

Then the land destroyed by the meteorite was covered in desert. The climate was hot and dry. Then only reptiles and mammals roamed the earth. The temperature gradually started to drop, but the carbon dioxide levels in the air were still high. Plants grow slowly. Plant species such as ferns tend to be more widespread.

The final phase of the Mesozoic era was the Cretaceous period. At this time, the continents began to separate from each other. As a result, dinosaurs evolved and species experienced extreme diversity. Ecosystems gradually become stable and complex. This led to the development of mammals.

Ecosystems during the Mesozoic Era were not as complex as they are today. Dinosaurs were so large because of the adaptation of their bodies to the climate and ecosystem. At times during the Mesozoic Era, carbon dioxide levels reached 3-5 times normal levels today. Due to this the plants grew in abundance. In other words, there would have been an explosion of plant life on the planet. Along with this, the oxygen level also increased. At that time there was an abundance of food in the world, but the number of its predators was few.

According to this theory, extinct ecosystems and such climates caused dinosaurs to grow so large. Looking at the present, you can see how complex the current ecosystem is. And how damaged the Earth’s climate is. This is mainly the reason why no animal in the present world is as big as dinosaurs. There are many other theories behind the size of dinosaurs but this theory is more convincing.