[p-ond]

Have fun

Pterohippi are the modern development of my old species Equus avis. There is some more old species info here.
You can do what you want with them and develop them how you like.

This is a sci-fi/ science fantasy species concept, but I realised that the way I had taxonomically classed Equus aves as part of the Equus family is lowkey unrealistic, so here's an updated phylogeny tree for the species and, hence, a new clade name: pterohippus, derived from the greek ptero (wing) + hippus (horse), meaning winged horse, in line with the naming of some of the earlier horse ancestors like eohippus.

PHYLOGENY TREE
(caveat- I might change this as I do more research)
Mammalia
└── Perissodactyla
....└── †Eohippus (extinct last common ancestor)
........├── Equinae
........│ └── Equus
........│ ...├── E. ferus
........│ ...└── E. caballus
........│
........└──†Aerohippus (extinct last common ancestor)
..........└── †Pterohippinae
.............├── Penequus (feathered wings)
.............│ └── P. gracilis
.............└── Pelequus (membranous wings)
............... └── P. noctis
† = extinct

DOMESTICATION
Penequus gracilis is the one pictured above, on account of its feathered wings and slender frame. You are more than welcome to head canon your own pterohippus species if you want other builds or features!
If you want domesticated winged horses with huge variations in phenotype (like modern dogs and horses) you can tack the "docilis" modifier on to the end of the species name, (like the "caballus" in Equus ferus caballus or the "domestica" in Columba livia domestica). This lets you get away with big variations without having to make a whole new species for what you want.

In the lore I've written, pterohippi are extinct, but it's up to each player to decide the lore for their own world. Did science bring them back to life, or have some secluded populations survived in secret?

BREEDING
If you want to play "realism" then individuals in the batwing genus and featherwing genus probably shouldn't be able to interbreed, and breeding for fertile offspring should happen within species (e.g penequus gracilis x penequus gracilis, etc.).
However, if you want to push reality a little bit and allow breeding between pterohippi of different genuses or between pterohippi and regular horses or other fantasy species, then feel free to go ham, and you can make up your own science or magic as to how this happens if you want.

EVOLUTION
How the wings and horselike phenotype developed.
Pterohippi are pseudo-horses. They share a common ancestor with horses, but they are not really horses; they have different behaviours, vocalisations, and digestive physiology. For example, they use mammalian chirping vocalisations and hunt and eat small mammals, birds, and insects. They evolved alongside horses, competing with them for grazing but found additional success in hunting, due to an intestinal adaptation which allowed them to digest insect and animal proteins. Their flight capabilities allowed them to hunt in the forest dwelling stage of their evolution, and later to travel greater distances at lower energy cost, circumventing rugged or difficult terrain to seek out fresh pasture.

The last common ancestor that pterohippi have with modern horses is the eohippus. Aerohippus then emerged, evolving small proto-wings that aided flying-insect and bird hunting through rapid flapping for increased off-ground lift while leaping. At this time, aerohippus was still a forest forager like eohippus.

After this, divergence in wing development started to appear, with some populations evolving membranous wings, and some developing feathered wings. It is thought that membranous wings were advantageous in hot climates due to the surface area available for heat dissipation, and feathered wings in cold due to their insulation properties.

The Penequus is the feathered variant, its name deriving from the latin penna (feather) and equus (horse).
The Pelequus is the membranous variant, its name deriving from the latin pellis (skin) and Equus (horse).

FOLKLORE
"Horse that moves on the upper winds"
I'm still workshopping common names for the species.

Remember, all these species 'rules' and lore are just guidelines that I made up! You are more than welcome to use the species motif (the design of the species) for whatever lore or stories you want to.

Anatomy Diagram for Penequus gracilis

[COOLDOGOOO]

ooh this is so cool, ive never heard of them befroe. MARK!!

[24Beaver01]

OH MY LAWD I DIDNT KNOW I NEEDED THIS UNTIL NOW

[AustrianAce]

mark! <3

[Kruxly]

mark

[finoodle]

AAAA POND THIS BRINGS BACK MEMORIESSS! I remember having an equus avis back in the day thanks for letting us use this!

[Kagome963]

Big oh MARK!!