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So I thought about how my dragon-like species would get it's wings between the arms and legs and I figured that this would be the evolutionary path for such a creature:

Hexapodal ancestor -> Quadrupedal walk with arms able to grab(so midway between Bipedalism and obligate hexapod) -> Evolve bipedalism for increased speed -> Middle set of limbs becomes vestigial to lessen drag, but the bones are still there -> Previously vestigial limbs start growing into wings when the creature becomes bipedal(all this time that bipedalism has been a trait, the bipedalism only shows when the creature is older, but before it becomes an adult) -> Wings over time get bigger and bigger as they help with locomotion(not necessarily flight, but WAIR(Wing Assisted Incline Running) is definitely plausible) -> Creature as of now

And while this occurs, particularly when Bipedalism evolves, their mass increases as they become the top predator in their ecosystem. This both helps and hinders. It helps because they don't need to move their legs as quickly to acheive the same speed and thus less energy is exerted per muscle cell. But it hinders in that after a certain point, the increase in wingspan won't help with locomotion.

So then I was thinking about what other purposes wings could serve besides the obvious locomotion purpose and then, well, I see wings used for sexual displays all the time in birds(Ostriches and Birds of Paradise are just a few birds that use wings as part of a sexual display), so I figured that even though my species is closer to a Lizard than a bird in terms of integument, the wings could serve a similar purpose. But, I figured that juveniles would still use their wings for WAIR and it would only be at a certain age that the wings would serve a sexual purpose.

Is this plausible though? And what is the most likely thing that would increase the chances of attracting a female? Showing off the colors of the wings? If so, would it be possible for the scaly integument of the wings to change colors due to a response to male hormones, maybe even an increase in blood flow to the wings during mating displays to make the colors even more vibrant?

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These reptiles undergo meristic morphology as they reach sexual maturity, and the vestigial wings grow and become more showy. The Atlantic pink salmon is a good example of meristic morphology in real life. In the sea, they have a very typical fish appearance. But when they swim up the river to spawn, they change color, grow a large hump, and their mouth turns into a long hooked beak. Females get longer tails and anal fins.

For your species, during the season when these reptiles are looking for a mate (or mates, if they are not monogamous), the females exude pheromones which stimulate the males into competitive selection. The males then become aroused, and have to compete in aerial combat for a mate. This combat is intended to find the most agile and proficient mate to ensure a fit offspring. During the combat, the reptiles claw and tear at each-other, becoming badly damaged. Their adrenaline is increased dramatically, and they produce coagulants to prevent them from bleeding to death.

All these hormonal changes and bloodletting makes the courtship process very aromatic. There is the scent of pheromones, and male hormones, and blood.

A defeated male may flee the area to recover, or perhaps they fight to the death.

Courtship wings are glossy metalic colors, and prior to one observed style of attack, instead of flying up to a higher position, on cloudless days they can often be seen tumbling and rolling beneath their opponent in spectacular aerobatics. Their wings flip wide like a kite, then thrust up powerfully once, then tuck into a roll-dive. This repeats in a sort of taunting aerial dance, trying to provoke an attack. The upper male is tricked into thinking they have an advantage. But this is done to reflect sunlight into their opponent's eyes blinding them before a strike. Angered by the brilliant glare, the opponent tries to dive into lower animal, but they can not see. They can only strike at the last known position, so the bottom contender has an advantage in visibility. They easily roll out of the attackers way and rip at their wings as they pass.

After mating, at the next molt, the brightly colored scales are shed and smaller, more camouflaged scales replace the mating wings.

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That's not exactly how I'd see the evolution. If we're going to begin with a hexapod model, I'd see back legs as the power generators (as in most quadrupeds), and front and center legs as the 'steering' legs (used for changing directions when walking or running). There would be an evolutionary pressure to turn the front pair into a 'balance' system — allowing the head to lift higher off the ground, while swinging the foremost pair of legs as torque for rapid turns — then the center pair would evolve towards grasping appendages. If we then assume sexual selection based on apparent size (as in a lot of ground birds, like turkeys and peacocks, where tail-fans increase the male's optical size), the front legs would evolve both to increase apparent (optical) size by assuming a broad wing shape, and to increase the apparent (optical) height by creating lift that allows these proto-dragons to flutter upwards a few feet as a mating display. Follow the evolution onwards from there, and the front (wing) legs will migrate slightly backwards towards a more feasible flight position, while the center legs will migrate in and up for a more effective grasping role.

Bipedalism does not increase speed in any creature. Bipedalism evolves when the front legs adapt to grasp trunks or limbs of trees, usually in comparatively slow creatures that jump upward and cling in order to escape ground-bound predators. If you were being chased by wolves and had any sense, you'd climb a tree; that is a successful evolutionary adaptation. If you had the capacity to jump or flutter your way up, you'd do that instead. The extra pair of limbs your dragonoids have is ripe for exploitation that way: it doesn't have to choose between fluttering up and grasping; it can do both.

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  • $\begingroup$ Isn't it generally the case though that across all terrestrial species, extinct and living, that of a biped and quadruped with the same exact mass, the biped is faster because bipeds have a generally longer stride than quadrupeds? And isn't that more true the higher the mass is? And isn't it also true that the more legs a creature has, the slower its max speed because there is less room between the legs compared to the creature's size? $\endgroup$ – Caters Aug 18 at 2:10
  • $\begingroup$ @Caters: A white-tailed deer weighs around 150 lbs and runs at about 30 mph; Great Danes are about the same weight and run at about the same speed; average sprinting speed for a human is around 15 mph (though the fastest can get to about 28 mph). Cheetah's can get close to 80 mph in the same weight range. Bipeds may have longer strides, but they have to alternate legs, cutting their power production in half; quadrupeds get power from two legs on each stroke. $\endgroup$ – Ted Wrigley Aug 18 at 2:32
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Possibly depending on the atmo. the larger the wings the faster flight and more dominance there for making the larger wings on males more attractive for hunting, and the larger the wings on females more attractive for protecting and hiding the young from predators. Much like early homo sapiens had larger bums for better endurance making them the Tortoise that won the race against the Hair rabbit. I know this might not help the question of the juveniles but it may help protect them by making them much faster and more agile.

P.S. If you want them to burp fire with much pressure and velocity you need to make it so they have a bladder made for holding methane and a possible ignition method being flint and steel on muscles in the mouth on the roof or more realistic methods could be used of which I don't know.

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