How did the dinosaurs evolve?

How did reptiles evolve and how are they related to dinosaurs?

• Answer:

  http://en.wikipedia.org/wiki/Evolution_of_reptiles Reptiles arose about 310-320 million years ago during the http://en.wikipedia.org/wiki/Carboniferous period. Reptiles, in the traditional sense of the term, are defined as animals that have http://en.wikipedia.org/wiki/Scale_(anatomy) or http://en.wikipedia.org/wiki/Scutes, lay land-based hard-shelled eggs, and possess http://en.wikipedia.org/wiki/Ectotherm metabolisms. So defined, the group is http://en.wikipedia.org/wiki/Paraphyly, excluding http://en.wikipedia.org/wiki/Endotherm animals like birds and mammals that are descended from early reptiles. A definition in accordance with http://en.wikipedia.org/wiki/Phylogenetic_nomenclature, which rejects paraphyletic groups, includes birds while excluding mammals and their http://en.wikipedia.org/wiki/Synapsid ancestors. So defined, Reptilia is identical to http://en.wikipedia.org/wiki/Sauropsida. Though few reptiles today are http://en.wikipedia.org/wiki/Apex_predator, many examples of apex reptiles have existed in the past. Reptiles have an extremely diverse evolutionary history that has led to biological successes such a shttp://en.wikipedia.org/wiki/Dinosaurs, http://en.wikipedia.org/wiki/Pterosaurs, http://en.wikipedia.org/wiki/Plesiosaurs, http://en.wikipedia.org/wiki/Mosasaurs, and http://en.wikipedia.org/wiki/Ichthyosaurs.