Flying Snakes
While there is one entry in the MM, there are three known and distinct species of flying snake. While the snake species may vary a bit, it's the wings that people notice.
In India, the flying snakes of the local jungles have bat wings. Atlantean experts consider this reptile/mammal blend to be the work of some long dead wizard.
On the Dragon Continent, the flying snakes have dragon like wings. To some the difference between a dragon's wings and a bat's wings are mostly a matter of size, but, again, Atlantean experts claim there actually is a noticeable difference. Not that anyone has actually seen both, much less well enough to compare them.
The third species is that of the jungles on the peninsula connects the Western Continent to the Dragon Continent. This is also the jungle of the Couatl, so the experts are of the opinion that these flying snakes with iridescently feathered bird wings were created by the same dead god that the Couatl say created them. Actual explorers that have been on the Dragon Continent, however, mention other feathered reptiles that can been seen there,so that may not be the case.
The really important take away here is: Bat wings, Dragon wings, bird wings: These are the earmarked of the 3 known species. not that mostfolks consider it all that important...except for a few Atlantean Sages.