What is a dinosaur?

My little Amaree gets awfully frustrated when people call animals "dinosaurs" when in fact they are not. A dinosaur is described as a reptile that walked on 2 or 4 legs that stood directly under their bodies and walked on land. Lizards have their legs bent and out to the side of their bodies.
So anything that lived with the dinosaurs that flew or swam were in fact NOT dinosaurs. They were flying reptiles or Pterosaurs and swimming reptiles.
If you forget, don't worry, my 4 year old will in fact correct you (I get corrected regularly).

Also just learned that the Pterodactyl is not its true name. It's Pterodactylus. Sometimes Amaree is given these facts and decides, "Nah that's not true. When I'm a paleontologist I will prove them wrong."

Here are some Pterosaurs that are her favorites:

Quetzalcoatlus was the largest flying reptile. With a wingspan of over 36 ft long and weight of 300 lbs, it would be like a grizzly bear taking off of the ground!

Here is Tiny the Pteranodon. She is from the show Dinosaur Train. Pteranodons ate fish and had a wingspannof 25-33 ft long! They stood at about 6 ft tall as well.