The Cretaceous is the last epoch ending the Mesozoic era. He replaced the Jurassic, according to the calculations of geologists, about 145 million years ago and lasted about eighty million years, after which the Tertiary period of a different, Cenozoic, era began - the “era of new life”. This rather long stage of the Earth’s development got its name due to the fact that it left us a legacy of powerful deposits of chalk, marl and sand. Although during these eighty million years on the Earth there were no catastrophes of a planetary scale and, consequently, the extinction of a large number of plant and animal species, the movement of tectonic plates, changes in the sea level and climate change made their corrections to the evolution of living things .
The Cretaceous period is usually divided into subdivisions: lower and upper Cretaceous. To understand how life developed in the seas, on land and in the airspace of that time, it is necessary to briefly characterize the tectonic mountain-forming processes that took place, starting from the Jurassic stage. In the Lower Cretaceous era, Gondwana and Laurasia continued to move away from each other. The exact same process happened with Africa and South America. Thus, the Atlantic Ocean more and more took shape now familiar to us. But in the east of Gondwana connected with Laurasia. Australia was where it is today, but only a third of the present territory towered above the water.
Upper Cretaceous is characterized by the fact that in the Northern Hemisphere the sea level began to rise, and the vast areas of Eastern Europe, Western Siberia, all of Arabia and almost all of modern Canada were under water. However, by the end of the Cretaceous period, the Earth began to resemble a modern globe with its outlines.
In the Cretaceous period, climate also underwent changes. He, of course, was much warmer than modern. The spaces of today's Europe were covered with real tropical jungle. However, in high latitudes, the seasons were already changing, and snow fell in winter. Such climate change gave an impetus to the fact that, along with spore and gymnosperms, closed-seed plants appeared. Trees such as beech, birch, ash and walnut, which appeared in the Chalk era, have survived to this day unchanged. The earth acquired the first flowering plants - first magnolias, then roses. The flowers had the advantage that not only the wind, but also the insects carried their pollen. Fruit plants, hiding the seed in the fruit, spread with the help of animals that ate the fruit. Thus, fruit and flowering plants invaded the entire planet.
Changes in the flora in the Cretaceous caused the emergence of new species of fauna. The first butterflies began to fly in the air and bees flying on the nectar of flowers began to fly. The sea is dominated by foraminifera, dead and crumbling shells of which gave the name to all this geological time. Along with them, other ammonite mollusks arise. Sharks and bony fishes dominate the fish kingdom . The animals of the Mesozoic era - first of all, dinosaurs and the first mammals - safely migrated from the Jurassic to the Cretaceous. But during the Cretaceous, several dead-end branches of bird-like lizards die out, for example, archeopteryx. But then birds appear - the ancestors of modern geese, plovers, ducks and loons.
Judging by the famous film, the Mesozoic era (the Jurassic period in particular) is also known as the era of dinosaurs. In general, the primacy of the ancient dinosaurs is preserved in the Cretaceous. But over the past period, the stegosaurus disappears from the face of the earth, and a tyrannosaurus occupies its niche. The rich plant world contributed to the emergence of new species of herbivorous dinosaurs: triceratops, iguanodons, ankylosaurs and others. We can say that in the Cretaceous era, the species diversity of dinosaurs reached a peak. And at this time, hiding from the giants according to their minks, the future rulers of the Earth, mammals, also inhabited. These rat-like animals rarely reached one meter in length; most of the species were small egg-laying, armored or marsupial animals, up to 500 g in weight. But there was a future for them.