User blog:StaraptorEmpoleon/What is a dinosaur?

What is a dinosaur?
Dinosaurs are "upright limbed, open hip socketed and grasping handed ornithodirans (dinosaurs, pterosaurs and their closest relatives), and is composed of the most recent common ancestor of Iguanadon and Megalosaurus and all of its descendants ."



Dinosaur ancestors
Dinosaurs evolved from Dromomeron and Lagerpeton and eventually evolved into animals such as Marasuchus and then, dinosaurs.



What are some examples of dinosaurs?
There are two main branches of dinosaurs:
 * The Ornithischians ("bird-hipped dinosaurs"), which became extinct;
 * The Saurischians ("lizard-hipped dinosaurs"), which are survived by birds



What isn't a dinosaur?
Many people think pterosaurs, ichthyosaurs, plesiosaurs, mosasaurs and Dimetrodon are dinosaurs; however, they are not. They don't have the upright structure of dinosaurs.


 * Pterosaurs are flying reptiles, with skin stretched between their arms, like bats.


 * Ichthyosaurs are swimming reptiles.


 * Plesiosaurs are swimming reptiles as well.


 * Mosasaurs are swimming reptiles that are closely related to Komodo dragons!


 * Dimetrodon is in a whole different clade of reptiles, the ancestor of mammals. They became extinct before dinosaurs even appeared (280–265 million years ago; dinosaurs appeared 231.4–0 million years ago).