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I am raising dragons for my world. So far they had 4 limbs (2 legs that are also used as wings and 2 legs used for walking and grabbing things). But I started wanting to embrace the fantasy even more and now I've decided that they will have 6 limbs, 4 used for walking and 2 used for flying. But a problem arises: the anatomical conflict between the wing muscles and the leg muscles. I went researching and found this art and found it interesting, but I still don't know if it's biologically realistic:

enter image description here
Artist: Todd Lockwood

Would the musculature shown in the image work on a real dragon if there was one, or would it need to be altered? The point is, none of the legs can be stunted like a kangaroo arm and the wings have to be functional rather than ornamental. Flight is pure physics, the dragon will live in a world different from Earth with the right conditions for it to fly, so you don't have to limit it to the physics of our planet. The flight doesn't make use of magic. My dragon is horse sized. If necessary, you can tell if the wings need to be behind or in front of the front legs.

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  • $\begingroup$ this depends a lot on the underlying skeleton but the wing muscles look way to small. of course this also depends on the size of the animal and how much magic you are willing to tolerate. $\endgroup$
    – John
    Dec 14, 2021 at 22:00
  • $\begingroup$ Minus one for linking to Pinterest without warning. Lots of people have a rather negative opinion about such predatory antisocial media companies. $\endgroup$
    – AlexP
    Dec 14, 2021 at 22:16
  • $\begingroup$ But I'm not able to insert the image in the post, there is always a problem with insufficient memory on the cell phone. $\endgroup$ Dec 14, 2021 at 22:27
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    $\begingroup$ A "nitpick" is metaphorical a tiny movement/comment addressing a single minor irritation. A "nit" is a small parasite, which is unpleasant if not removed. (In my local dialect, "nit" refers to the egg of a head louse, bane of parents around young children.) Here, Lemming is using it to make it clear that the complaint is a minor one, and to convey a caring tone rather than a hostile one. (For my approach, wyverns can be considered a subset of dragons - enough worlds have interchanged the two. Others like to draw a distinction, which is presumably useful for them somewhere, so I'll respect it.) $\endgroup$
    – Anon
    Dec 21, 2021 at 2:13
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    $\begingroup$ You have forgotten to say, do you allow the magic to influence the flight, or it is pure physics. $\endgroup$
    – Gangnus
    Jan 28 at 0:31

4 Answers 4

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Given the OP's statement that the dragons are horse-sized on a planet on which they can fly, a number of points regarding the illustration come to mind:

  1. The placement of the muscles for a creature with a roughly vertebrate skeletal structure appears suitable.

  2. The wings would likely need to articulate from joints in bones rigidly connected to the spine, more like the pelvis than the scapulae.

  3. The bones of the wings look a little thin to support the whole creature's weight in the air if it is horse-sized.

  4. The size of the muscles seems a little odd. Either this creature spends most of its time on the ground, and hunts large, robust prey, and flies only occasionally, requiring that it has a physique that is muscular overall, or else its non-flight muscles are slightly too large and its flight muscles are too small. Being able to fly means that it should be supremely capable of 'kinetic kills', diving to attack prey and killing by sheer impact forces, and so it should not need such bulky muscles elsewhere. Additionally, smaller non-flight muscles are lighter, and easier to lift, and for a creature that flies a lot, would have an evolutionary pressure selecting for that trait.

  5. Horns would appear to be counterproductive. They would likely serve no purpose other than as a sexual attractant. I would expect the horns to be present only on males, and I would also expect them to be very light and used for display only, not for combat. They would likely be easily broken, or they may be shed and regrow in time for the breeding season, in which case, they could afford to be a bit more robust.

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  • $\begingroup$ As you say, but also horns are defensive and mating features for prey animals, not predators. Perhaps these dragons are herbivores. $\endgroup$
    – Separatrix
    Jan 28 at 8:03
  • $\begingroup$ @Separatrix, just because predatory species familiar to us don't have horns doesn't mean that a new one couldn't have them. Sure, they're impractical, but they're saying, 'I can lug these useless things around and still be healthy, so I'd be a good mate,' and because they're a mating attractant, they're selected for. $\endgroup$
    – Monty Wild
    Jan 28 at 9:19
  • $\begingroup$ Again, I can't think of a predator that does that either, they tend to be more practical. I stand by these being herbivorous dragons! Given the bulk of the body over the wings, they're ground dwelling with flight available like chickens, just about fluttering to a higher level, maybe for reaching higher branches on trees for better fruit picking. $\endgroup$
    – Separatrix
    Jan 28 at 9:30
  • $\begingroup$ @Separatrix The Lion's mane is the best example I can think of. There must be a nonzero biological cost of having a big fluffly mane! $\endgroup$
    – Daron
    Jan 28 at 21:36
  • $\begingroup$ plenty of predatory dinosaurs have horns, crest, and other weird strictures on the head, that goes double for pterosaurs, so horns and such are fine. $\endgroup$
    – John
    Jan 30 at 3:29
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How large is your dragon?

Very interesting question, but there's a caveat here:

I still don't know if it's biologically realistic.

Functional flight is heavily restricted by the square-cube law: Wing-area and muscle-area scale up (pun intended) slower than mass. So a finch-sized dragon can afford to be stringy and use far more tendon than muscle, while a house-sized dragon will need huge wings and exotic muscle materials to get off the ground at all.

For a non-expert answer assuming that size is large enough for it to matter: I'd consider mounting wings just aft of the ribcage, and providing a hip-like structure of buttressed bone plates for them to attach to. This will probably mean dividing the abdominal cavity. Alternatively, you could run tendons around the ribcage, which will require a secondary lung (as some birds have).

Overall, large flying dragons have handwaved/magical biology anyway, and you can lay muscles out based on aesthetics and string tendons to wherever you need the force.

(NB: This answer will become obsolete with clarification about size, but may provide a useful spark for better thoughts.)

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  • $\begingroup$ "House sized" might be beyond reach, but nature has built some pretty big "birds" in the past. The Quetzalcoatlus , a late cretacious period pterosaur, had a wingspan well in excess of 30 feet, and stood about 10 feet tall. Though I suspect a lot of the assumptions of what makes a dragon a dragon might not translate. The Quetz was all wing, giant beak and stomach and not much else. Weight estimates put the big fellas at about 200kg. Earlier estimates where as low as 70kg, but recent research suggests the much larger figure. $\endgroup$
    – Shayne
    Jan 28 at 4:15
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the world it lives on needs a denser atmosphere and lower gravity, its wing muscles are way too small for earth. On large fliers the wing muscles start to make up a larger and larger portion of the body mass, square cube law is unforgiving. the largest animal to ever fly is larger than your dragon but also almost all wing muscle. on the upside the overall size of the wings seems good.

Ask yourself how does my dragon fly, is it a glider or strong maneuverable flier, this will tell you how much muscle it needs.

here is all the muscles on the wing of pterosaur not counting the flight muscles.

enter image description here

Your dragon has very cat like but has no reason to be. Its limbs are shot but powerful, yet completely useless for hunting, they are built like cat limbs, but if they try to roll around with prey like a cat they will destroy their wings, and they are far to short and angled wrong to be used in fight.

Its body is way too long and flexible for a flier keep in mind everything is essentially hanging from the wing shoulder in flight, fliers want to be compact and need a fairly rigid body, mammals are fairly weird in having a lumbar region most animals just have ribs all the way down. This makes the body stiffer but can also support more wing muscle. look at a birds, bats, and pterosaurs, shot compact bodies. long thin bodies make for good swimmers or climbers not good fliers.

Birds are probably your best model since unique to birds many birds still retain good ground locomotion, but bird wing muscles may not be a good model since they have both sets of flight muscles on the ventral side which is unique to birds.

If it is horse sized the neck is too long and weak for its head, a predator with a big head wants a necks that is shorter to support strong muscles for it, or it can have a small head and a flexible neck. lower gravity may help but you still have many competing hunting styles in the anatomy.

Ask yourself how does your dragon hunt. Does it attack from the air or ground, does it kill with claws or teeth. Remember a big animal with wings cannot rolling around with its prey, so don't use cats or crocodiles as a model.

On the other hand horns and crests are fine, both birds and pterosaurs did this grow large ornamentations on the head, but keep in mind they should probably be hollow.

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Flying or Walking

A dragon is not like a flying horse. Most of the time, it will be flying. It will walk (slowly) only when is on the ground and reaching things nearby. It will never run or gallop like a horse because when it needs to move fast, it will fly instead of running.

Therefor its legs need not be as long as a horse. To capture heavy animals, it will need claws. Hooves will almost be useless.

Wing Size

A golden eagle has average:

  • Weight = 10 to 15 pounds
  • Body Length = 33 and 38 inches (84cm-96.5 cm)
  • Wingspan = 6 to 7.5 feet(182cm-229cm)
  • Wing width = 1.8 ft. (54 cm)

Flight muscles make up between 35 to 60 percent of the eagle's body weight.

An Arabian horse has average:

  • Weight = 800 to 1,000 lb (360 to 450 kg)
  • Body Length = 8 feet (2.4 m) (nose to tail)

A dragon of the size of a horse will need a wingspan of approximately 25 feet with wing width of about 4 feet.

Wing muscles may be similar to an eagle as shown here.

enter image description here

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