Could a tetrapod Pegasus exist?

Pegasuses in most works of media are often depicted as hexapods with four legs and two wings:

The only problem is (from what I understand) no vertebrates on earth are hexapods, so I've decided to take a sort of wyvern approach and make them tetrapods! Now some characteristics of these "Pegasuses" include:

• appearance like a cross between a Przewalski's and a white Icelandic horse
• 25% smaller than an Icelandic horse and are a bit more slender
• quadrupedal (similar to pterosaurs)
• mostly solitary
• very downy fur
• capable of flight
• herbivorous
• monogamous (similar to kiwis or gibbons)
• capable of being ridden but can't fly while doing so (optional)

Given these characteristics, what species could they have evolved from, and what evolutionary pressures would lead to them?

NOTE: magic does not exist in my story

posted over 4 years ago

icewar1908‭

6 reputation 47 0 1 0