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Tyrannosaurs overthrown smaller dinosaur species during their growth

 Explore the American scientists team

A team of American scientists concluded that dinosaurs descended from giant carnivorous species such as tyrannosaurs, which were born as small as kittens and grow into giant creatures, were changing their environment by eliminating smaller species.

The study, the results of which was recently published in the journal Science, helps solve an ancient mystery about a period in which dinosaurs dominated for about 150 million years: Why were there so many more large species than small ones, while the opposite is true for terrestrial animals today.

Explore the world of dinosaurs

In the entirety of the Mesozoic era, from 252 million years ago to 66 million years ago, there were relatively no longer any large species of dinosaurs weighing more than a ton compared to those weighing less than 60 kilograms.

According to some scientists, the larger species of dinosaurs that start their lives are also very small in size because they from in eggs before birth, may exploit the resources of the smaller species in ecosystems that were largely dominated by them.

This conclusion is reinforced by the way in which dinosaur diversity has evolved over time. In the Jurassic period 200 years ago to 145 million years ago, the differences between the two groups of animals were smaller in this category, while the Cretaceous period ( between 145 million years and 65 million years) contained very large dinosaurs.

This is due to the fact that the genera of giant dinosaurs in the early stages of development during the Jurassic period were more like adults, and they had a greater variety of herbivores available for hunting.