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This is the third question in a series of such for my worldbuilding project that deals with plausible fantasy creatures. Previously, I have pondered cockatrices and hydras, but now we move on to another popular mythical animal, the griffin. Last two questions: Is petrifying vision plausible in an animal? and Hydras as parasitic-mating, polyandrous amphibians?

The griffin, or gryphon, is a well-known beast of fantasy that was depicted by the Egyptians, Iranians, Minoans, Greeks, Romans and Medieval people. It is said to have the body and forelegs of a lion and the head, wings and hind legs of an eagle. However, the consistent thing in all portrayals of griffins is that they have four legs and two wings.

Yes, flying quadrupeds, Bane of Worldbuilders. Such an anatomy would require the griffins to be hexapods, which isn't realistic evolutionarily. So, hexapodal griffins must be ruled out. When I realized this shortly after considering including griffins in my worldbuilding project, I thought that I'd have to simply leave them out.

But then I remembered a real-life group of giant flying animals, the Azhdarchids. The largest species in this group being the giraffe-sized Quetzalcoatlus northropi, they walked with their wings as their forelimbs.

Could a bird evolve such locomotion? My premise is that these griffins could have evolved from Accipitrids or similar birds, and grown larger and larger until they gained a wing-walking posture to sustain their massive size. Hypothetically, their movement would be very Azhdarchid-esque, and it would be about the size of a horse.

Now to the real question: would massive wing-walking birds a) evolve rather than some other method of sustaining their frame, and b) survive and hunt with such adaptations?

SealBoi
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    If you have already found an animal implementing the kind of feature you have in mind, why are asking the question if it can evolve? – L.Dutch Jun 06 '18 at 10:40
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    One of these days I'm going to start a meta thread about questions that ask "could x evolve?" since they seem to be pretty popular. However, evolution is so complicated it cannot really be simulated or predicted. Maybe this has meaning for most people, I personally have no idea how such a question could be answered other than establishing that such an animal could exist and survive = your question b. The fact that you separated them tells me that I am missing something, could you perhaps explain why you think they are different but answerable questions? – Raditz_35 Jun 06 '18 at 10:46
  • @Raditz_35 Question a) asks if a raptorial bird would be compelled to move like this as a result of growing size, as opposed to some other method of sustaining its massive frame. Also, I was wondering if it would be viable for such a thing to occur in a relatively short evolutionary timeframe (Accipitrids evolved in the late Eocene, but didn't grow large for quite some time after that.). – SealBoi Jun 06 '18 at 10:55
  • I do not get this at all from the question. Perhaps clarify this via edit. Evolution includes such things I guess, but many, many others as well. I think it is perfectly fine to ask if you focus on two aspects of this – Raditz_35 Jun 06 '18 at 11:03
  • @Raditz_35 Gotcha. – SealBoi Jun 06 '18 at 11:04
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    sadly won't have time to answer this question in full, but did want to provide another method to having gryphons in your world, it's actually part of a 'series' asking about justifying mythical creatuers so you may want to check out the other questions in the series as well. You can find a particularly long answer here: https://worldbuilding.stackexchange.com/questions/25281/anatomically-correct-griffins/25387#25387 – dsollen Jun 06 '18 at 13:10
  • @SealBoi Why are hexapods unrealistic? There are creatures on earth with far more than 6 limbs. I'm genuinely curious - this isn't meant as criticism. – Josh Jun 06 '18 at 13:11
  • @Josh hexapods are fine, FLYING hexapods aren't. To fly one needs to be very light, relative to body/wing size, and aerodynamic. The wide body required for more then two legs isn't areodymaic, and more importantly is too heavy. More to the point multi-legs fits a different evoluitonary niche then wings, a species like this would likely adapt to focus on their legs and land travel, or their wings and give up multi legs, but not keep both traits which don't synergize and leave it mediocre, at best, in two niches instead of great in one. – dsollen Jun 06 '18 at 13:14
  • @Josh I meant hexapodal birds, which is implausible. This also applies for hexapodal reptiles (dragons) and ungulates (pegasi). – SealBoi Jun 06 '18 at 13:17
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    @dsollen If the SealBoi was only talking about flying hexapods, I absolutely agree. Many bugs fly in the face of this point, but their size, exoskeleton, and very different sort of wings put them far away from anything like we're talking about here. – Josh Jun 06 '18 at 13:18
  • @SealBoi Thanks for the clarification. I 100% agree with that. (Although it makes me sad, as a lover of dragons) – Josh Jun 06 '18 at 13:19
  • @Josh Yeah, as I said - Bane of Worldbuilders. In fact, this project does include two dragon-like taxa. There are the true dragons (Family Draconidae), which are very large, flightless varanoids. Then there are their close relatives the wyverns, family Wyvernidae, which have two legs and two wings. This was the closest I could get to plausible flying dragons. – SealBoi Jun 06 '18 at 13:23
  • @josh very true about insects. Once you get small enough the square-cube law gets pretty lenient with body structure and allows all kinds of things that wouldn't fly (I'm punny!) with larger animals. – dsollen Jun 06 '18 at 13:24
  • @SealBoi -"Yes, flying quadrupeds, Bane of Worldbuilders. Such an anatomy would require the griffins to be hexapods, which isn't realistic evolutionarily." Hexapods are perfectly realistic evolutionarily. They would have to evolve on a planet where the fish equivalents that became amphibious and then land dwelling walked on six fins isntead of four. And maybe the planet in your story might have been seeded with lifeforms from other world(s) so that hexapods and tetrapods coexist, or possibly both hexapods and tetrapods evolved in different parts of that planet. – M. A. Golding Jun 07 '18 at 02:13
  • @Sealboi hexapoidal birds, reptiles, and ungulates are impossible, because those are classes of earthly tetrapods which are all four limbed. But extraterrestrial analogs of birds, reptiles, and ungulates that are hexapodal are all perfectly possible and plausible in science fiction, let alone mystical hexapodal analogs of birds, reptiles, and ungulates in fantasy. – M. A. Golding Jun 07 '18 at 02:22
  • @dsollen & SealBoi, I'm really struggling to see the issue with 4 legged 2 winged creatures in a worldbuilding sense. (I have read the comments with pretty plausible statements). The Pern Chronicles by Anne MccAffrey have just such dragons being central to her plots. I would think in some respects the whole concept of worldbuilding supports creatures that for some reason haven't "made it" in our world - but could have made it elsewhere. SOOOO, in other words, why not just have a classic Griffen? http://www.fanpop.com/clubs/griffins/images/24266375/title/griffen-photo – kiltannen Jun 07 '18 at 02:24
  • @kiltannen Wings, at least in vertebrates - and definitely griffins - are modified forelimbs. In bats and most renditions of dragons, the fingers support wings, while in birds and griffins, the feathers do that. The point is that to have a bird, mammal or reptile with four legs and wings, you need a terrestrial ancestor with six legs so that the middle pair could evolve into wings, leaving four spare to be legs. But a six limbed bird/reptile/mammal is impossible, because... well, they're tetrapods. – SealBoi Jun 07 '18 at 08:17
  • @SealBoi, Thank you. I suspect there is a restriction you have in your worldbuilding that is not obvious to me. There are 2 major examples of other authors that have created large and very successful franchises, where they have created multiple species that have exactly this configuration. 1] The Dragons of Pern. 2] Harry Potter has Hippogriffs and winged horses(eg Thestrals). The challenge I have with understanding your restriction, is not a problem of misunderstanding evolutionary pressure - you & DSOLLEN have illustrated this well. It is understanding why you have this restriction. – kiltannen Jun 08 '18 at 00:25
  • The Dragons of Pern are a science based franchise, Harry Potter is a magic based franchise. Another example of a hexapod is the Sphinx species in David Weber's Honor Harrington series, but that species has not developed wings. They are feline with 6 legs. They are a species that has evolved on another world in our galaxy. I am wanting to understand your restrictions because this is an interesting question, and I'd like to offer some potential answers, But I just don't know why we must be limited to purely accurate evolutionary pathways of our own planet and world... – kiltannen Jun 08 '18 at 00:29
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    @kiltannen My apologies, I didn't mean that hexapodal animals are implausible universally. I was more talking solely about the evolutionary continuum of Earth, as I want all the creatures in this project to fit phylogenetically into the taxonomy of our world as we know it. Here, I cannot see hexapodal vertebrates evolving any time soon - perhaps ever - but yes, it is possible on other planets. Indeed, it is only by coincidence that the fish who gave rise to tetrapods were four-finned. Had they been six finned, life on earth would have been a very different story. – SealBoi Jun 08 '18 at 09:01

2 Answers2

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This worked out just a little long for a comment,

Simple Answer, yes!

You've already got documented evidence of a creature that moves the way you want it to, and that happened due to evolution, but they're not the only ones... Bats will fly, however if injured and unable to fly they walk along the floor in the manor described.

The Problem

The issue you may have is that creatures way back when were all larger, part of this is back then the density of the atmosphere was lower, therefore lower pressure therefore they can be bigger(oversimplification i know, not getting into that here), if Jurassic park actually existed, a T-Rex would probably be about the size of a family car, rather than a bus. so it depends on the size of the creature you want at the same time as humans, realistically your griffins/gryphon's would probably be about the size of a decent turkey

Possible work arounds

Maybe have them be smaller and be pack animals, weather good or bad is up to you and you can describe them in ways that do so, good animals would be beautiful fur covered creatures that look healthy and then hunt smaller animals intelligently, like a Wolf, whereas evil might be skinnier more leathered skin and very aggressive and act more like hyenas

Or have them be horse size, maybe talk about how they have shrunk since man first saw them, have a debate on wether man was just smaller or they have shrunk, maybe find massive bones belonging to their ancestors, after all giraffes exist and so do elephants, big animals exist all around the world, its how they act compared to smaller aimals is whats important. these animals don't fly but maybe the your gryphons walk more and only fly when needed to save the huge energy required to do so. if you think about the Rhino, Elephant and Girafe they are all slow land based animals but all can move quite quickly when they need to, but never over a great distance

Pneumatized Bones might help but you'd have to offset this against the wieght those bones would have to carry

Blade Wraith
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  • Hmm.. I planned for them to be horse-sized. Would pneumatized bones help? – SealBoi Jun 06 '18 at 11:19
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    while the weight of the bones would be an issue, bones full of holes are usually more brittle, conventional images of gryphon/gryphon like creatures is they are usually strong and potentially dangerous when angry, unless you want them as a mount then maybe make them wolf sizes and have them be pack animals, the whole image you have described is one that if done right could invoke fear on a large scale, maybe on a smaller scale but they're everywhere could be even more effective... just a thought edited my answer for other ideas – Blade Wraith Jun 06 '18 at 12:00
  • Hollow bones with an internal latticework of triangular "scaffolding" would both be light and very strong. This could work. – SealBoi Jun 06 '18 at 12:09
  • It could indeed work, how far into detail do you need for your story? latticework would make them both strong and light, but they tend to evolve in smaller creatures, Bones was often used in Weaponry, if your Gryphons do have this bone structure it might be a nice detail to mention how their bones were sort after for spears for that reasons – Blade Wraith Jun 06 '18 at 12:16
  • All I need is a plausible way for wing-walking, horse-sized birds to evolve and survive. – SealBoi Jun 06 '18 at 12:22
  • Then go with what you have, you know that these animals can exist, you know the bone structure can exist, so from there its how you write it into the story, so long as it can't break down buildings with a single strike or fly half the speed of sound etc then it should be fine... they will probably need to eat quite often though... – Blade Wraith Jun 06 '18 at 12:42
  • From my understanding is hither oxygen presume that allowed for bigger animals, nor lower air pressure. – Pliny Jun 06 '18 at 12:42
  • @GarretGang Yes, I believe that's the case. An example would be the Carboniferous explosion of oxygen levels which produced a host of giant insects. – SealBoi Jun 06 '18 at 12:45
  • Higher Oxygen is one possible cause for animals in dinosaur times to be bigger, lower pressure is another, along with a few other theories, none have been confirmed to my knowledge, most likely a combination of many factors, if i'm wrong then apologies. – Blade Wraith Jun 06 '18 at 12:56
  • I know for sure that higher oxygen 0reasure allowed insects to become larger. – Pliny Jun 07 '18 at 18:40
  • Lower density atmosphere would make it harder to be large, not easier. 2. there is no evidence for a significantly different atmospheric density during the mesozoic. wish I could downvote this twice.
  • – John Jan 28 '19 at 18:41