Wyverns

Wyverns are wild, winged beasts with scale-hides. They have striking similarities with, and are sometimes mistaken for Wyrms. Wyverns are relatively small in comparison to their draconic counterparts, and do not possess any intellectual or cognitive ability beyond that of a horse or other large animal.

Comparatively, in terms of mental age; for an average adult, it would have a mental of a 4 year old Human. This is common for many animals, including horses. Like some beasts, some have taken to taming wyverns and riding them. They are a rather volatile species and are prone to aggression, so taming such a beast can be fatal if you aren't careful.