Pachecatosaurus lived 67 million years ago, with a body length of about 5 meters and a swollen head, which seemed to have a huge tumor. It walked on two stout hind legs, and it was a bird-footed dinosaur. Spines or tumors with horny or bony processes on the face and mouth; The back of the skull is covered with a prominent structure, and the top of the skull is surprisingly thick and swollen, up to 25 cm thick. Because the skull is swollen and thick, some holes in it are closed. Pach Cartron mainly lives in the desert of inland plains and mountains. Pachecatosaurus, which means "lizard with thick head" in Greek, belongs to Pachecatosauridae and lives in Maastricht, North America in the late Cretaceous. Fossils have been found in Montana, South Dakota and Wyoming. Pachycephalosaurus was a herbivorous or omnivorous dinosaur. At present, only one skull and several skull parts have been found.

There is only one species of pachycephalosaurus in Wyoming. Tylosteus is also found in western North America and is considered as a synonym for pachycephalosaurus. Small bone tumors are covered around the head and nose tip. Some individuals have big and sharp thorns behind their heads, and their teeth are small but sharp. Its skull is covered with a bone plate with a thickness of 23 cm, and the back of the skull is covered with a prominent structure. Some spikes are as long as 13 cm and about 4.5 meters long. There is a prominent bone shed at the back of the thick-headed faucet bone, which is about 25 cm thick and looks like a bowling ball. Pachycephalosaurus had a short and thick neck, short forelimbs and long hind limbs, and its body was not too big. The bony tail is fixed by tendons and may be heavy. Paleontologists' research proves that dinosaurs evolved from a relatively advanced reptile in the late Triassic period more than 200 million years ago, and experienced about 65.438+500 million years of evolution, and all of them were extinct at the end of Cretaceous period 65 million years ago. Dinosaurs were widely distributed almost throughout the Mesozoic era. They are found on all continents except Antarctica. There are many kinds of terrestrial animals in Mesozoic, which ruled the kingdom of terrestrial animals in Mesozoic for a long time. So some people call Mesozoic the dinosaur age.