Answer:
The flapping of wings create forces which are caused by usage of two muscles pectoralis and supracoracoideus.
Step-by-step explanation:
An ornithoper is a bird which fly by the movement of its wings. These creature fly by using their muscles. They may differ in flying method from one another but their way of flapping and flying is same. Pterosaur are the close cousins of dinosaurs who used to flap their wing to fly. They are not birds instead they are a form of reptiles who fly.