Pteranodons and Quetzalcoatlus are prehistoric flying reptiles that lived during the Mesozoic Era, and they are not alive today. However, I can still address your question hypothetically.
The idea of a human riding on top of a flying Pteranodon or Quetzalcoatlus is based on speculation and imagination rather than any factual evidence. We do not have any direct evidence or fossils that suggest humans interacted with these creatures in such a way.
Pteranodons and Quetzalcoatlus were large animals, and they would have been powerful fliers capable of carrying significant weight, similar to large birds. However, several factors make the idea of a human riding on top of one unlikely:
Anatomy: Pteranodons and Quetzalcoatlus had long, slender necks and beaks, which would make it challenging for a human to hold on or have any stable grip during flight.
Behavior: We have no evidence of these creatures being domesticated or displaying any behaviors that would suggest they could be ridden.
Size: While these flying reptiles were large compared to many other animals, they were not on the scale of modern aircraft. Their size and strength may not have been sufficient to carry the weight of a human without severely compromising their flight capabilities.
Safety: Riding wild animals, especially those with no historical interaction with humans, would be incredibly dangerous for both the rider and the animal.
In summary, while the concept of riding a Pteranodon or Quetzalcoatlus might be an exciting idea in fiction or fantasy settings, it is not supported by any scientific evidence or realistic considerations.