Dragons are actually horses
Commonly thought to be reptiles, dragons are actually descended from a genetic mix of horse and eagle.
Most terrestrial creatures in the world are tetrapods, evolved from a four-limbed fish that made its way onto land. Humans, horses, birds, and lizards all came from this ancestor. Thus, you could only expect terrestrial and airborne vertebrates to have four, not six limbs. But dragons have four legs and two wings. Now you might say “wait a second, what about the legends of wing-arm dragons?”
You’re thinking of wyverns, the extinct reptile-descended predators.
True dragons, the ones we have today, actually get their start as herbivores.
The first pegasus were a flock of horses enchanted with eagle wings by forces not yet understood.
These early pegasus were not able to fly, as they weighed far too much for their small wings. However, the wings did provide some manner of lift when climbing steep mountains, so the herd thrived and propagated into a pegasus similar to modern species.
Discarding their ruminant digestive system in favor of something more lightweight, these pegasus ate seeds, nuts and fruits. They’re much more aerodynamic than their predecessors, but must remain small as their diet does not provide enough calories to power a large body.
Though they were largely herbivorous, some groups experimented with omnivore diets. And one, finding that to be lacking, went full carnivore.
Called Xanthus by paleontologists, these carnivorous pegasus reverted many of their genes to pre-horse ancestors, splitting their hooves, sharpening their teeth, and turning much of their plumage into primitive quills. A truly terrifying creature, the xanthus was driven to extinction by its own apatite, and the descendants that out-competed it.
True dragons have reworked their hooves back into claws, and shed their flight feathers in favor of a membrane similar mythical pterosaurs. While the free finger of their bird wing was able to revert to a claw, the rest of their wing bones were too far removed from walking limbs to spread out into fingers, hence the dragons’ unique silhouette when compared to wyverns.
The similarities between modern dragons (left) and ancient wyverns (right) are an example of convergent evolution, much like flying fish and butterfly wings are closely related shapes with completely different evolutionary paths.
Speaking of evolutionary paths, there are many new entries of creatures descended from dragons.
The basilisk is one of a few hexapods to return to terrestrial life. Their wings descended into forelimbs that they use to grasp prey while running or climbing through tunnels.
Stay tuned for the second major branch off the pegasus line!