why are pterosaurs and aquatic marine animals in the past not considered dinosaurs?

Question

why are pterosaurs and aquatic marine animals in the past not considered dinosaurs?

In: 4

Answer 1

Because we define dinosaurs to be a specific kind of animal, not just “animals that are old.”

Dinosaurs are animals of the clade *Dinosauria.* This is a much more specific classification of animals that generally applies to land-based reptiles with the same body structure. The Wikipedia page on dinosaurs does a pretty good job of describing that structure, so I won’t go into detail here.

Pterosaurs are part of a distinct lineage of animals.