Pegasus
the smartest mare in Equestria tests her most recent invention.

Pegasi are winged ponies, able to fly, whose affinity for weather allows them to control it. Though native to Equestria, can be found almost anywhere. However, unlike the other pony races, the pegasi have several cloud cities and settlements that non-fliers are unable to reach without the aid of magic or flight. they are more inclined to eat meat than unicorns or pegasi.

Pegasi have an affinity to the weather, giving them the ability to control wind and weather, as well as permit them to walk on and move clouds, and in some cases, control lightning.

Hippalektryon

More nomadic and herbivorous than pegasi, hippalektryons (rooster ponies, chicken ponies, pheasant ponies) can fly, but prefer not to. they are native to the Stirropean country of Arion.

Noctral

Noctrals (thestrals, bat ponies, or negasi) are a race of pony with bat-like wings and ears, and cat-like eyes, hailing from the dark mountainous regions of Equestria. Their fangs are used like a changeling's... for tearing into fruit they grow in their orchards. they have excellent night vision and echolocation, and are stronger and faster than normal pegasi, but cannot manipulate weather as well as their pegasi cousins.

Noctrals live in large townships called Colonies, which are matriarchal and located in caves. it is not uncommon for them to crowd together when sleeping.

Dragon Pony
a dragon pony and a Pegasus stand guard while a unicorn works a spell.

Descendants of a cursed pegasus bloodline (according to legend), dragon ponies (Longma, Dovahkhin, Dracosi) appear normal from a distance, though closer inspection reveals the head, right foreleg, upper body, mane, and cutie mark of a pony, and the spines, hind legs, tail, and left foreleg of a dragon.

Found throughout the northern countries, mostly Northrim, they are fierce, and have quick tempers, as well as fiery breath. they are herbivorous, but capable of eating gems.

VALKYRIE

Valkyries are a secretive race in the skies of Sleetspire. Unlike many pegasi, they have three sets of wings, fairly thin bodies and even their ears take on an almost wing-like shape. In fact, their wings could seem to be quite cumbersome on the ground, as apparently these pegasi never land any lower than the lowest cloud. Some even don't seem to realize the ground exists at all, believing all the world is nothing more than the dark thick clouds forever above Sleetspire. In the air they are very graceful, swift fliers, and legends abound about them being able to fly all the way to heaven itself. Indeed many a Fluffy pony regard them as 'angels' almost.

MEENI

a race of flightless, six-inch tall pegasi found on an island discovered by Lyra Heartstrings. the one shown here is a stallion, as is shown by his blue-and-red banded wings.

The Meeni have many unique cultural quirks, the least of which is how a mare decides who her suitor will be. the prospective stallions will attach long, colorful streamers to their tails, and participate in what can only be described as a jumping contest, where they will jump over a large log several times their height. Somehow, this allows the mare to decide who her future husband will be.

Colts and fillies receive separate schooling, colts starting at the age of ten, and fillies starting at five. The colts learn to be blacksmiths, masons, builders, and soldiers, while the fillies learn the trades of scholars, archivists, diplomats, and farmers. Though the mares are capable of holding titles of prestige, it is only the stallions that can own property and hold the position of Drakik. The Drakik also is the only stallion allowed more than one wife, and can pick and choose mares as he pleases.

They bury their dead with their heads pointing downwards, believing if they should ever rise again, they would wake up and begin digging the wrong way.

They write in a counter-clockwise spiral, circling out from the center. Their books opened from the top, making the covers more like lids in a way. The letters of their written language are similar to a mix of Neighponese kanji, Saddle Arabian calligraphy, and ancient Helotian hieroglyphics, and their alphabet consists of 34 letters. Thankfully, the spoken language is actually made up of the same sounds that made up the Equestrian spoken language, but certain words are capable of conveying quite a few meanings depending on the tone and method of pronunciation. For example, “Drakik,” when pronounced with emphasis on the “Dra” and the last “k” almost sounding like a click (DRAH-ki-CK), meant “Ruler of the Island,” whereas “Drakik” pronounced with a drawn-out “aaaaaa” and emphasis on the first “k” (draaah-Kik) referred to a type of flowering plant, and “Drakik” with a rolled “r” and long “eeee” sound (drrrra-KEEEEEK) meant “Highest of mountains.”

Their farming is superficially similar to that of a normal Equestrian earth pony, tilling the soil with a plow, and using regular watering schedules. However, they irrigated their crops by means of a complex system of above-ground pipes.

1890255
As usual, great expansion of the Equestrian Pegasi and their "variants".
The Dragon Pony is a particularly interesting addition, one which, quite frankly, I did not see coming.

Good job on providing your headcanon for further expanding the Equestrian universe, Reggie (if I may call you that)

1890636 thank you.

1890255
Kudos on giving the smartest mare in Equestria the recognition she is due.

Now for my wingpony headcanon:

Pegasi are fascinating, both biologically and magically. Incorporating avian aspects and an entire additional limb girdle into the basic equinoid body plan, they demonstrate more than any other tribe that pony genetics make no sense whatsoever.

Pegasi cannot fly without the use of magic; their wings simply don't generate enough lift, though they do allow gliding. Evolution has developed a number of biological adaptations to ease the burden on pegasus magic, making them as flight-compatible as a horse can be. These include highly porous bones, incredibly powerful wing muscles, large lungs, and the most efficient metabolism among the tribes.

This metabolism makes most pegasi big eaters; flying takes a lot of energy. As such, winged ponies are those most likely to practice carnivory, and their digestive systems are primed for it. Pegasi can eat more meat more frequently without any ill effects than the other tribes, though they still work best on a primarily herbivorous diet. This was the main impetus for raiding during the Three Kingdoms era; clouds don't offer much vegetation.

All applications of pegasus magic are derived from the pegasus's aura, an ambient field of magical energy that extends an inch or two from her body. On its own, this field is imperceptible and harmless. It can be thought of as a lens, focusing the pegasus's magic and will into tangible results. Flight, for example, uses the aura propulsively, magnifying physical thrust well above the threshold needed for takeoff. The product of muscle and magic can be anemometerically measured as wingpower. However, such measurements cannot distinguish a physically powerful, magically weak flier from the opposite.

Pegasus magic does more than simply allow them to fly. Cloudwalking is a well-documented aspect of this magic where the aura interfaces with the condensed water vapor of clouds as a much stronger focus, allowing a pegasus to defy gravity with a pittance of magical energy. Theoretically, a pegasus could refine this ability to allow her to stand on thin air, but doing so would require a much higher magical expenditure and would quickly exhaust even the most powerful flier. And, of course, most pegasi would rather just hover.

Weather manipulation, or meteoromancy, is an extension of this discipline. Rather than having the interfaced cloud passively hold a pegasus, the pegasus actively holds and moves the cloud. Rain is made by suddenly focusing more magic into the cloud through suddenly forcing the aura into the cloud (i.e. kicking it.) The sudden magical influx causes water particles to condense into droplets heavy enough to fall. Lightning has the same somatic focus, but requires different magical techniques, manipulating the charge distribution of the cloud through sheer force of will and aura mastery. Thunderbucking takes minutes to learn and years to master. Aiming is especially difficult; the Royal Guard's elite Storm Corps, famed for their coordinated precision lightning strikes, won't accept anypony with less than a decade of weather management experience.

The aura offers protection from weather as well as mastery over it. It exhibits a "Maxwell's demon" effect, acting as a semipermeable membrane for heat and keeping the air immediately around the pegasus at a comfortable temperature. This has led many ponies to believe that pegasi don't notice heat or cold, but this is far from the truth. The effect has its limits, and can only do so much in extreme environments like the Crystal Mountains and the depths of the San Palomino Desert. Few pegasi are even aware of this aspect of their magic, and without this awareness, they cannot feed more power into it. The aura also acts as an electrical insulator, using a primitive form of abjuration magic to reduce the severity of shocks, allowing pegasi to take lightning with little more than singed hair.

Pegasus magic also protects against sudden impact. When the space of the aura suddenly becomes occupied by a solid, the aura compresses, forming a cushioning barrier that absorbs a considerable amount of momentum, be it that of a falling pegasus or a speeding projectile. Pegasus bone structure also plays a part; while their bones are porous, what matrix there is forms nearly unbreakable honeycomb-like layers of tessellating triangles. Force sufficient to break a pegasus's bones would be enough to kill a non-pegasus pony at least twice over.

One final application of pegasus aura is pterodactylism, also known as "wing fingers." This uses the aura as a muscle, flexing the primaries in ways that the wing's actual muscles cannot. This form of pegasus magic is fairly uncommon, as frequent use of the primaries in this way can damage them in slight ways that can curtail top flight speed. Still, it gives a pegasus some of the dexterity enjoyed by unicorns, and some consider the tradeoff acceptable.

One final note is that pegasi face some perils most ponies do not. A creature as taxonomically confused as a pegasus needs magic to function properly. If a pegasus spends long enough in a dead magic zone, she will molt completely. Even more time will see her coat cover the bare wings, at which point the condition is nigh-irreversible.

This magical dependency also puts pegasi at risk for a terrible disease known as schismatism. This illness can only affect chimeric creatures, and has also been documented in griffins, manticores, and cockatrices. A schismatic pegasus's body essentially realizes that it's not supposed to have both feathers and fur, and rejects its own wings. If left uncured, the wings atrophy and necrotize, putting the pegasus's life at risk. Note that this is actually one of the least severe cases of schismatism; in more evenly mixed species like griffins, the disease is almost immediately fatal, as each half of the body attempts to destroy the other.

1925205 and what of the bat ponies?

Funny you should say that. I broke this up so I present two walls of text and not a single impenetrable monolith of verbosity.

Chiroptera

In order to discuss the chiroptera (ki-RAWP-terr-ah, singular chiropteron, more commonly known as "bat ponies,") one must first discuss what they are not. They are not pegasi twisted and mutated by black magic, though they do have an affinity for darkness and that which dwells within it. They are not illusions created by the uniform of the Night Guard, though they are the most insular pony tribe, keeping to themselves as much as possible. They are not all black, though one will find many more dark-coated individuals than not. They are not all vampires, and while there is the occasional exception to that statement, vampirism can appear in any of the tribes. They have existed as long as any of the other tribes, but their isolationism and frightful appearance inspire many dreadful legends.

The chiroptera share a few magical and morphological properties with pegasi, the most obvious being wings, flight, and cloudwalking. Chiroptera can manipulate weather, but it is rather more dangerous for them, as they lack the heat and electrical insulation of the pegasus aura. Similarly, without the aura's kinetic dampening, they are theoretically more vulnerable to crashes. In practice, their bones are slightly thicker and even tougher than pegasus ones, and they generally fly at lower altitudes.

Chiropteron metabolisms are just as quick as those of pegasi, and they're adapted even more in favor of carnivory, including sharp canines, several digestive enzymes other tribes don't produce, and a slightly shorter intestinal tract. Chiroptera are near-obligate omnivores; while able to subsist on a vegetarian diet, they prefer a small, regular amount of animal protein, usually from insects, shellfish, or other arthropods.

Chiroptera are generally nocturnal, though they can adjust to a diurnal activity cycle much as other ponies can do the opposite. Their senses are much more acute than other tribes'. Their eyes and ears are excellent examples of convergent evolution, to those of cats and bats respectively, giving them incredible night vision and an enormous range of hearing. This pairing of sophisticated senses make chiroptera almost impossible to surprise; even in total darkness, they can magically emulate a bat's echolocation.

As a side note, the combination of incredible senses and customary isolationism has led to some fascinating cultural developments that are still, in many senses, coming to light. Ebonist expressionism is an art style that uses a color palette that cannot be properly appreciated in lighting brighter than a full moon. Critics have both derided and praised the style as "shades of black." Chiroptera have also invented several musical instruments that can only play in ranges inaudible to most ponies, including the sopranissimo saxophone, the triple bass, and the resonant cabochon, a crystal that is "played" by directing ultrasonic frequencies at it. Among the musical elite, "nocturne" is quickly becoming code for "you will only hear half of this."

Sonar is a good example of what chiropteron magic can do, as many of their abilities focus on the manipulation of light and sound. They can magically augment their already sharp senses by enhancing the input itself. They can also augment outgoing light and sound. This was developed as a way to intimidate predators, either by brightening the reflections off of their tapeta lucida or by delivering a screech on par with the Traditional Royal Canterlot Voice. Alternately, they can muffle and dim their surroundings when stealth is needed. This dampening effect also happens reflexively when chiroptera are suddenly presented by bright lights or loud noises, protecting them from sensory overload. Nowadays, many use it while sleeping as a cheap substitute for an eye mask and earplugs.

Chiroptera have something of a checkered past with the rest of equinity. Over the years, they have been seen as ill omens, incompetent changelings, untrustworthy scoundrels, evidence of infidelity, heralds of the Nightmare, and more besides. As is often the case, the superstitions were self-fulfilling. Nopony trusted the chiroptera, so the chiroptera had to turn to untrustworthy means of support. At the end of the Three Kingdoms era and the beginning of Fumblewinter, they were the first scapegoat all three tribes turned to. The bat-winged ponies saw the writing on the wall and fled south before their fellows could do anything beyond blame.

Even after the Hearth's Warming, the newly unified Equestrians hesitated to welcome their dark kin. The founders found themselves split. Clover the Clever knew chiroptera were unfairly persecuted from her studies, but Platinum Unicornis couldn't overcome her deep prejudice against what her father had always called "flying filth." Smart Cookie could see naught but good coming of welcoming them into the fold, but Pansy Prudentwing could imagine only misfortune. Tapioca Puddinghead saw only unmade friends, but Iona Hurricane remembered lifelong enemies.

In the end, no choice was made, which was itself a choice: live and let live. The chiroptera accepted this, and sought remote places in forests and peaks to call their own. By the time the princesses appeared, the bat ponies were little more than a persistent rumor, an actual sighting momentous enough to tell one's grandchildren. Luna knew they were out there, but respected their obvious desire for privacy. Roughly two hundred years before her banishment, she wrote in her journal that "Ye Nighte bee ye Konseelur, obskuuring what ye Daye wuld lay bare."

After the Battle of Day and Night, the chiroptera stared at the newly wrought Mare in the Moon in awe. Few had ever travelled to Castle Everfree or Castle Canterlot. Never until now had they understood the sheer power of the princesses. But now that they did, they swore that they would not forget. Within a year, Full Gloaming became the first chiropteron to swear the Guard's Oath. Within ten, the Night Guard was officially a part of Equestria's military. In other matters, the chiroptera stayed a tribe apart, but each time the Guard was called upon to protect princess and country, they stood with the others.

When Nightmare Moon returned, she was not alone. With Celestia banished and Luna driven mad, with the promise of night eternal seemingly fulfilled, many dark and foul things emerged from the shadows, hungering for the light and life of the ponies. They drank in unicorn spells, supped on pegasus aura, feasted upon earth pony strength. Every attempt ponies made to defend themselves left them withered husks, and their attackers that much stronger.

Then came the Night Guard. Here were ponies who could dim their light and wield the darkness as skillfully as those who called it home. Once faced with prey that could fight back, the horrors fled to their holes. Even chiroptera not in the Guard could face them, the humble ponies driven by instincts they never knew they had. When the sun rose, its light restoring those who fell prey to the hungry darkness, it did so on the Night Guard's finest hour.

Today, Luna and the chiroptera have both been rejoining Equestrian society slowly but steadily, each supporting the other. Every bat-winged dot in the night sky lightens the princess's heart, and every sign of greater strength she shows gives the chiroptera new joy. The integration is gradual and ha been a long time coming, but it doesn't show signs of stopping anytime soon.

When you think about it, the Greek Mythological Hippalektryon is like the reverse of a Hippogriff, or maybe it's the other way around?

Get This, in Portugal Mythology they have Two Bat-Winged Horses that breath fire & control storms, one is called "Cavalo do Pensamento" - a Good Guy who is said to appear before those who think about it very hard & gives them a ride, the other is called "Cavalum" - a Bad Guy said to be imprisoned within a Real World system of caves named after him (Furnas do Cavalum, located in Machico, Madeira), so perhaps the Bat-Ponies could be named Cavalum(used in both the Singular & the Plural), while Cavalo do Pensamento could have at one time been a legendary hero/leader to the Cavalum race.

Nice of you to acknowledge the Chinese Mythological "Longma" as a Dragon-Horse Hybrid, however there are Longmas in the video game "Them's Fightin' Herds", the spiritual successor of the Fan-Game "My Little Pony: Fighting is Magic", and both the Story & Character Designs were made by Lauren Faust - who as you may already know is also responsible for MLP-Friendship is Magic, and I feel that the Longmas in TFH may be closer to what they would be like in MLP:FiM.

I get that you want to bring the Valkyries to MLP, but I don't think that Six Winged Pegasi is the right way to do so, even though the Valkyries were said to ride on Winged Horses, but there are apparently several other magic horses in Norse Mythology, maybe you should try setting up some Equine Hierarchy for the Norse Gods' Horses, like with these lists HERE and HERE, and like if Sleipnir(8-Legs, Flies without Wings) is the Horse of Odin, he could be the Alpha-Horse or whatever.

The closest thing to match that Meeni in MLP is the "Breezie", which is more like a Pixie/Fairy/Sprite version of Ponies.

Frankly I'm surprised you didn't mention the Flutterponies, a race of Ponies similar to Pegusi, except they have slimmer body frames, and have Butterfly-like Wings, I mean they've only been a part of MLP since G1 back in the 80's, and the temporary Magic Wings that Rarity used back in Season 1 were based off of the wings of the Flutterponies, right down to being made of Gossamer, so it's possible that the Flutterponies exist in Equestria, they've just never been explored in the series before.

Also just so you know, in Greek Mythology there is also a race of Winged-Centaurs called Pterocentaurs, and since Tirek proves that Centaurs exist in Equestria, they could be several different races of Centaurs as well, and perhaps some with Wings.