The Last Glory of the Dinosaur World-Cretaceous Period

Cretaceous is the last period when dinosaurs ruled the earth. During this period, the earth has undergone earth-shaking changes, and dinosaurs have evolved into many kinds. It can be said that this is the last "glorious years" of this giant reptile. Different from Jurassic period, it was relatively calm in geology, and the geography of Cretaceous period witnessed a revival of plate tectonic activity. The continental drift during the Cretaceous period led to the continuous separation of the north and south supercontinents, namely Laoya and Gondwana, and separated them into continents with basically the same structure as now.

Great changes in dinosaur habitats

The global climate was soft and warm in the middle and late Jurassic. But this is not to say that there was only one fixed climate during the Jurassic period. Just like now, the Jurassic has deserts, mountains, islands and other areas, all of which have their own unique climate characteristics. Although the poles are warmer than they are now, they are still colder than the equatorial regions.

due to the violent movement of the plate, the height of the horizontal line reached its highest in the middle Cretaceous 1 million years ago, and now about one third of the land is flooded. The acceleration of submarine expansion has enlarged ocean ridges, formed submarine mountains, and caused seawater to rush to areas that used to be land, resulting in a sharp rise in sea level. Such submarine expansion has also stimulated continuous continental division. The green island effect in the middle Cretaceous led to the melting of polar ice caps, which is also the reason for the rise of sea level. By the end of Cretaceous, the structural changes gradually slowed down, reducing the scale of ocean ridges and submarine mountains, forming a deeper submarine basin, and the water covering the mainland gradually opened three times.

Dinosaurs are still flourishing

The initial Cretaceous was the coldest period of this period, the middle Cretaceous was the warmest, and the climate in the late Cretaceous was somewhere in between. Fossils of plants, such as sequoia and magnolia, which can't adapt to the cold temperature, show that they once grew in the green land in the middle Cretaceous, which proves that the weather on the island was warm but northward. At present, traces of dinosaur actions and their fossils are constantly found in the coldest places, including Antarctica, Alaska and northern Asia.

In the Cretaceous, dinosaurs lived freely in the polar regions, which confirmed the rise of the earth's temperature in the early Cretaceous. Sediments and structural fossils also prove the rise of sea level in Cretaceous. The exposure of Cretaceous sedimentary rocks on the earth's surface is widely distributed, and half of the known dinosaurs were found in Cretaceous rocks.

The recipe for angiosperms to become dinosaurs

Before the early Cretaceous, most plants in the world were ferns and gymnosperms. In the early Mesozoic, gymnosperms became the dominant plants. They still exist now, such as more than 6 conifers, such as cycads and ginkgo trees. They have no flowers or fruits. Gymnosperms are very strong and strong. They have woody pulp, thick bark and leaves like branches, needles or ferns, which are very difficult to chew. The Jurassic herbivorous dinosaurs, including sauropods, stegosaurus and Ankylosaurus, all evolved powerful jaws, teeth and digestive systems to digest the nutrients in these plants, such as evergreen trees, cycads and other hard angiosperms. The digestive system of these animals minimizes the need for chewing, and uses a process of fermentation in the stomach to slowly extract nutrients from nutrient-deficient angiosperms.

Angiosperms have successfully survived in Jurassic World's mild and dry climate. They rely on the wind to spread pollen to seeds. The seeds of pollinated gymnosperms grow slowly. When they are fully mature, they will be as tall as conifers or ginkgo trees. Slow growth and height weaken the eating of herbivores. Sauropod dinosaurs ate the crown of angiosperms by getting taller, and also evolved a digestive system that allowed them to eat continuously, thus obtaining enough nutrients from the nutrient-deficient gymnosperms.

due to the rise of flowering plants-angiosperms, the rule of gymnosperms gradually weakened in Cretaceous. The main feature of angiosperms is a new reproduction life cycle, which accelerates their growth, reproduction and spread. Angiosperms use flowers to attract pollinators, such as insects, and they surround the seeds with pulp, which can help the seeds disperse when the fruits fall. Flowers help pollinate, fruits help protect the germ, and angiosperms spread and grow rapidly. The oldest known angiosperms grew in the early Cretaceous, about 145 million years ago. Along with the fossils of early marsupial mammals, feathered dinosaurs and birds, this primitive early flowering plant has paired stamens and seedy fruits, although it may not have flowers.

angiosperms quickly became dinosaurs' favorite food. Angiosperms reproduce much faster than gymnosperms, and angiosperms continue to cover a green space that may be consumed by dinosaurs. By the late Cretaceous, angiosperms were able to grow rapidly and spread widely, which allowed them to diversify into hundreds of species. The importance of angiosperms to the evolution of dinosaurs cannot be underestimated.

During the Cretaceous period, a large number of new branches of ornithoptera broke out, especially the hadrosaurs, Ankylosaurus and Ceratosaurus, which evolved the digestive function of adapting to chewing and digesting more nutrients, including absorbing the nutrients of the newly evolved flowering plants and the original gymnosperms. This period is the last glorious period of dinosaurs, and it is also the final end of dinosaurs. During the Cretaceous period, dinosaurs went from prosperity to extinction.