Known for their great size, dinosaurs appeared in the Triassic period, about 230 million years ago. They have evolved over time to become what they are today. There are several species of dinosaurs, but they are grouped into two main families. For more information, this content offers you details answering the problem.
The large family of saurischians or sauripelvians
This large family of dinosaurs includes the lizard-hipped species. They have an appearance with reptiles of the crocodile species and lizards. The saurischian dinosaur has a pubis that is directed downwards and forwards. There were some among this species of saurischians that were carnivores. The large family of saurischians includes, the sauropods which are very often with long giant you (Diplodocus, Brachiosaurus) they ate plants and are most often in herds; we also have the theropods which are species with animal feet like Compsognathus.
The large family of ornithischians or avipelvians
This species has two groups within it. These are the ceratopods and the thyreophores all having a bird's hip. The ceratopod group has horns with a resemblance to triceratops with a large skull and a large bony collar on the neck with three horns. This group also includes duck-billed dinosaurs and is called the hadrosaurids, much like the parasaurolophus. It has a very large crest, almost 2 metres high. The group of thyreophores is a little more primitive, they were quadrupedal and ate plants. They often had armour with bone plates or spikes. Some of them have a bony breastplate, while others have a bristly back with a large bony plate.