Evolution
Dinosaur Evolution:
Millions of years ago, the continents were all joined together and was called, Pangaea. As the continent was large, most of the inner part was a long distance from the sea, thus resulting in very dry, arid conditions. In the early Triassic period, around 250 million years ago, the environments were ruled over by the archosaurus. The archosaurus were an ancestor of the dinosaurs and were also the descendants of the earliest mammals. It wasn't until the late Triassic period when the first dinosaurs appeared.
These archosaurus are closely related to the group of dinosaurs known as the Marasuchus.​ By the late Triassic period , some early species of therapods such as the Eoraptor, Coelophysis and Herrevasaurus were some of the first dinosaurs. These dinosaurs were all carnivores.
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Archosaurus
Eoraptor
Here is a sound clip of a few dinosaur noises
The rise of prominence for the dinosaurs took place by the end of the Triassic period. The dinosaurs that were in existence at the time took advantage of the habitats that were left vacant after other extinctions. Many reptiles rather than dinosaurs were affected from the
environmental changes. Through out the remainder of the Mesozoic period, dinosaurs were dominating the land.
During the Triassic period the Saurischian dinosaur such as the Coelophyis, were carnivores. However, through evolution this species became larger and more tougher. They also adapted a lifestyle towards eating plants.
​Coelophyis
About two hundred million years ago during the Jurassic period, Pangaea began breaking up, due to the plate tectonics. This caused narrow seaways to separate the continents. As this was occurring, the mammal-like reptiles were becoming extinct. This allowed the dinosaurs to branch out quickly. The warm climate allowed the large dinosaurs to evolve. Such as the Sauropod. The Sauropod had many changes to the skeletal structure because of it's increase in weight. This dinosaur was the start to a long evolution of the larger dinosaurs.
Sauropod
By the Cretaceous period, the isolation of the different continents were very similar to this present day. This separation of dinosaurs allowed them to evolve from each other. They were unable to breed and exchange genes. The smaller herbivore which evolved at this time, scatted quickly. This dinosaur was called the Ornithopod. This dinosaur replaced the Sauropods because the sauropods found it difficult to adapt to the flowering plants that occurred at this time. Another herbivores dinosaur that evolved at this time was called a Nodosaurs. It developed a sharp beak for grazing on low plants. A carnivorous dinosaur that evolved during this period included the three meter long Deinonychus.
Ornithopod
Nodosaurs
It had evolved to suit it's carnivorous ways of life. This consisted of of a twelve centimeter retractable claw that was used to slash open the flesh of the animals it preyed on.
Deinonychus
During the late Cretaceous period, all the large, land animals had evolved such as the Tyrannosaurus.

The mass extinction of the dinosaurs occurred at the end of the Cretaceous period when a huge meteoroid, hit the Earth.
Tyrannosaurus