Two kinds of guesses:
One is that these arboreal dinosaurs jumped and landed among trees, gradually gained gliding ability, and finally were able to fly autonomously.
The other is that some scientists believe that flight does not begin with the process of arboreal life. They speculated that a feathered dinosaur that lived on the ground learned to fly while running.
The ancestors of dinosaurs:
Judging from the oldest dinosaur fossils found so far, dinosaurs only appeared in the middle and late Triassic, so the ancestors of dinosaurs should be some kind of reptile in the early Triassic.
In the early Triassic, there were many reptiles on the earth. Judging from fossils, the ancestors of dinosaurs were some kind of serrated reptiles. Compared with many reptile fossils at that time, it can be found that the fake E Long had the closest relationship with dinosaurs, so many orthopedic surgeons thought that the ancestors of dinosaurs were probably fake E Long.
Fake E Long is also called fake crocodile. Its body is thick and long, and its body length is generally between 1~2 meters. There are obvious ridges on its back, indicating that it is likely to live in water often, but its limbs are already very strong and developed, indicating that it can also walk on land with four feet. Its hind legs are very long, its forelimbs are very short, and it is likely that it can walk alone with its hind legs. Its head is very short, its eyes are very big, its nose tip is upturned (easy to float and breathe in water), and its teeth are long in alveoli, which has already possessed some characteristics of late dinosaurs.
Judging from the unearthed fossils, the fake E Long can be divided into two orders. One is sauropod: herbivorous sauropod and carnivorous theropod; 2. Hips of birds: It can be divided into four categories: Ankylosaurus, Ankylosaurus, Stegosaurus and Ceratosaurus, which are similar to the classification of dinosaurs.