The Fluidity of Dinosaurs

Dinosaurs are a diverse group of animals of the clade Dinosauria. They first appeared during the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the start of the Jurassic until the end of the Cretaceous, when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups ending the Mesozoic Era. The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic Period and, consequently, they are considered to be modern feathered dinosaurs. Some birds survived the extinction event that occurred 66 million years ago, and their descendants continue the dinosaur lineage to the present day. are the most diverse group of vertebrates besides perciform fish.and heights of
General description
Using one of the above definitions, dinosaurs can be generally described as archosaurs with hind limbs held erect beneath the body. This posture is due to the development of a laterally facing recess in the pelvis and a corresponding inwardly facing distinct head on the femur. Paleontologists think that Eoraptor resembles the common ancestor of all dinosaurs;
When dinosaurs appeared, they were not the dominant terrestrial animals. The terrestrial habitats were occupied by various types of archosauromorphs and therapsids, like cynodonts and rhynchosaurs. Their main competitors were the pseudosuchia, such as aetosaurs, ornithosuchids and rauisuchians, which were more successful than the dinosaurs. Most of these other animals became extinct in the Triassic, in one of two events. First, at about 215 million years ago, variety of basal archosauromorphs, including the protorosaurs, became extinct. This was followed by the Triassic–Jurassic extinction event, that saw the end of most of the other groups of early archosaurs, like aetosaurs, ornithosuchids, phytosaurs, and