An integral species in a large worldbuilding project I'm working on right now is based around the concept of extreme agility.

The species shall be a megafauna (Is that grammatically correct - "a megafauna"?), about as large as a human or larger. It lives in an extremely complex three-dimensional jungle where flora and terrain form all kinds of shapes and structures. Other than that, I haven't set anything in stone for the creature. It can be a predator, a herbivore, a scavenger. It can be quadrupedal, bipedal or both like a hadrosaur. Nocturnal, diurnal, crepuscular, it doesn't matter. All that does is that it is wired for agility.

This is just the basic premise - anatomy, physiology, ecology and ethology have not yet been worked out and will be based around that basic premise. In this question, I'm going to be focusing on the first criterion, anatomy.

So, this species must be able to do the following with ease and efficiency:

  • Jump far and high
  • Climb adeptly
  • Sprint short distances
  • Vault over obstacles
  • Swing
  • Roll without hurting itself
  • Run up near-vertical surfaces
  • Pull itself onto a surface when hanging from the edge of it

Those are the basic requirements, but if you'd like further clarification I'll go into more detail here.

Jumping: The species must be able to jump far, ideally 5 times its length/height (Whichever way its body is oriented) or more. I would like it to jump high as well, 2-3 times higher than its length/height (See above for which one to use). But, more than that, it must be able to jump with precision at specifically tailored lengths. Also, it would be great if it could jump and land feet-first on a vertical surface, while catching the horizontal top with its hands/forefeet.

Climbing: By this, I mean both climbing in a complex environment, like a monkey,and ascending vertical surfaces. In the latter one, it would run at the vertical surface, jump at it, and push up with a foot to reach the top. It also should have "wrists" that can rotate between 0 and 180 degrees, and some form of gripping mechanism.

Running: It won't have to run any marathons, but I'd like it to be able to outrun most human athletes on flat ground, for distances between 100 and 500 metres.

Vaulting: Vaulting is slightly different to jumping in that the practitioner uses their hands (It might be forefeet in this animal's case), to push their body over an obstacle. It would probably need moderately powerful forelimbs to do this.

Swinging: The species needs to be able to hang from horizontal bar-like objects and move itself forward. It may need to do this to clear vast chasms if there is a convenient bar.

Rolling: I would like my creature to be able to quickly move from running to rolling under obstacles it couldn't pass under at full height. Also, it should be capable of using rolling movements to absorb shock after landing from a large jump.

Vertical running: I don't mean running up 90 degree surfaces, but rather something more like 60-80 degrees, although if you can make it even higher then I'd be delighted. I was thinking that the creature could use something similar to WAIR (Wing-Assisted Incline Running) to do this, but obviously the wings, or wing-like structures must not interfere with the species doing any of the other skills.

Pulling itself up: This one's a bit hard to understand in the concise bullet-point, so I'll explain more now. If the creature jumps onto a cliff-like structure (Vertical side, horizontal top) and catches the horizontal surface but has its legs hanging down from the size, it must use its forelimbs to pull itself up onto the flat top.

I know this has been a long question, but most of it is just elaboration, clarification and specification on the main list of points. I wouldn't call this a broad question, because the essential question is very simple; "What would a species that can do x, y and z look like?"

This may seem implausible or too superpower-y, but technically, humans can do all or most of these things. The only difference is that we can do it because we have the consciousness to develop physical and athletic ability for our entertainment (I doubt there were many Stone Age traceurs), but these animals are wired for it.

A final word: If it so happens that some other kind of motion would be better for moving in a complex environment, then I don't really care. The question is asking what is the best an animal could be at these skills, not whether or not these skills are the optimal way to move.

  • $\begingroup$ I think you should add more details about the environment you want this creature to be in. Are you talking about, like, a rain-forest where most of the livable environment is above the ground or terrain that's rocky as all hell? Just a comparison to playground equipment would be useful. Cause I'm imagining an endless tree/root-system in space. $\endgroup$ – Pinion Minion May 17 '18 at 18:01
  • $\begingroup$ @PinionMinion It's a jungle - lots of life above ground as well as on it, but with far more massive flora. I amended the question to specify this. Thanks for the suggestion! $\endgroup$ – SealBoi May 17 '18 at 18:14
  • $\begingroup$ Hardly a comprehensive answer, but if you want sheer speed and agility through a jungle environment look at gibbons. Running might be hard, but if you just want sprinting it might be easier to get a knuckle-walker faster. $\endgroup$ – Ynneadwraith May 17 '18 at 20:46
  • $\begingroup$ With the exception of the swinging from tree you basically described a Lynx $\endgroup$ – Blade Wraith May 18 '18 at 11:17
  • $\begingroup$ While technically anything human sized or larger is "megafauna" in practice it's often used to refer to things larger than humans. $\endgroup$ – Tim B May 18 '18 at 13:35

You just described most arboreal primates, there is a reason parkour often looks to monkeys for inspiration. To see the truly amazing feats monkeys are capable of I recommend watching the BBC planet earth 2 episode on urban langur in Jodhpur India. I cant link the whole video but here is a rooftop running teaser.

Now what kind of anatomy do primates have for maximum acrobatics.

  1. flexible limbs of near equal length, the primate should allows foe a very wide range of motion, which is why we can brachiate (swing arm over arm). Having all your limbs the same length allows for a more even motion and allows them to switch from quadrupedal to bipedal easily and smoothly. Near equal length is important for ground speed, the primates that are awkward on the ground are the ones with disproportionate limbs, like chimps or us.

  2. long prehensile tails, extra limbs are always useful but the tails also serves as a cantilever for vertical climbing and a ballance pole for balance and jumping. They also serve as counterbalances for changing direction quickly, even cheetah use large tails for this. Ideally the tail should be the same length as the limbs if not longer.

  3. binocular vision, Primates evolved binocular vision so they can judge distance easily which is vital for a jumping from branch to branch, get your distance wrong and no amount of agility will save you.

  4. The smaller the better, the bigger you make your animal the less agile it will be, this is just due to the laws of inertia and the feedback loops of muscle size and strength, an animal twice as big needs far, far more than twice as much muscle to move at the same speed, which of course adds even more weight which means you need even more muscle. Notice gorilla are nowhere near as agile as a spider monkey or lemur this is simply due to mass. There is also the fall risk the bigger you are the shorter a fall needs to be to do serious injury.

  5. large semicircular canals, this is internal anatomy but a major feature of agile climber and flyers is their inner ears are huge, these are the organs responsible for our sense of balance and the larger they are the more sensitive they are.

  6. Larger brain this sounds weird but coordinated movement requires brain power which means a large cerebellum, Your animals are going to be changing their gait constantly so they need plenty of brain power to coordinate that.

  7. large strong flexible hands and feet, the larger the variety of grips your hands and feet can form the larger variety of objects it can grab, they also need to be strong to gain purchase from even partial contact.

The only performance you will not get is vertical running, large animals simply can't do it without a lot of specialization, specialization that will make them very bad climbers. Of course if they are decent climbers and jumpers they don't need it anyway, birds use WAIR because their limbs lack the flexibility to be fast climbers.

  • $\begingroup$ Well, I've seen human traceurs run up 60 or 70 degree slopes, so it might work for a really fit primate. $\endgroup$ – SealBoi May 19 '18 at 18:36
  • $\begingroup$ Its all about getting enough traction, which you can do on a slope, but WAIR works on a perfectly vertical or even an overhang, that is because the wings are supplying thrust in place of gravity, because ever push of the leg pushes out away from the surface you need a counter force to keep you in contact. During WAIR birds are basically flying horizontally while running vertically. $\endgroup$ – John May 19 '18 at 19:30

A creature which moves in a very complex environment is an octopus, and I suggest that the cephalopod is a good place to start.

enter image description here

starting point

The long, sinuous tentacles provide a means of reaching branches and other surfaces required for getting around in the jungle. Their bodies are extremely muscular, providing resilience to damage when dropping from the trees to the ground or if they accidentally swing into a hard object. If they retain the suckers, they have more gripping ability, and if you require the ability to manipulate very fine objects or develop sapience, there is no real reason the ends of the tentacles could not develop sub tentacles of their own, analogous to our fingers.

Jumping and running would require some changes to the cephalopod body plan, mostly in building some sort of skeleton or exoskeleton like structure to attach the musculature to. This could be an evolutionary leftover from the shell (cephalopods are closely related to molluscs like clams and snails) which provides the sorts of anchor points vertebrate animals use for their muscles.

Evolutionarily, the cephalopods can start to adapt to jungle life through living in the analogue of mangrove swamps. They may learn to climb out of the water to get over the roots, and discover new sources of food above the water surface. Eventually, there should be evolutionary adaptations to spend more time out of the water, including a toughened skin, trading gills for lungs and so on. In a TV series called "The Future is Wild" they speculate on just this sort of adaptation in a future Earth 200 million years from now.

enter image description here

Squibbon, a speculative tree dwelling cephalopod from "The Future is Wild"

One thing which does seem counter intuitive is your requirement for high speed running. While an aboral cephalopod may be able to run, I'm not clear that the evolutionary adaptations needed for running (outside of a short sprint to a safe tree) will develop in a dense jungle environment.

  • $\begingroup$ only down side of this is tentacles make for slow climbing they can't disengage quickly. $\endgroup$ – John May 19 '18 at 12:29

It lives in an extremely complex three-dimensional environment where flora and terrain form all kinds of shapes and structures.

This, along with the other requirements you have, suggests that an ape or a monkey would be the ideal candidate.

Notice that it doesn't have to be an ape or monkey from our world. Start with a chimpanzee for a template, for example, but remember that your creature will have evolved in your world - thus probably having a distinct shape, and being more fit for the challenges present in it.

Apes and monkeys take advantage of strong, agile arms to move between trees and other features of their environment in a locomotion mode called brachiation. In a lush forest, this would allow a creature to reach pretty much anywhere with ease as long as there is something to grip.

Asides the muscular and bone structure that allow for great agility, simians would also have another advantage: their relative big brain when compared to most other species means that they are good learners. This has to do with muscular memory and spatial mapping also, so a simian would be even better suited to navigate in the world you propose.

  • $\begingroup$ Do you think a simian would be able to perform the 3rd skill easily, though: running? Humans can easily outrun a knuckle-dragging chimpanzee on open ground, and as said I'd like this creature to be able to outrun most human athletes. I'm not trying to cast your answer into oblivion (I hate when people do that), I'm just asking what morphological adaptations you think they would have to achieve the more "leggy" feats. $\endgroup$ – SealBoi May 17 '18 at 18:24
  • $\begingroup$ @SealBoi what makes us better runners than chimpanzees is mostly our difference in shape. A simian from your world does not need to be shaped exactly like a chimpanzee - the chimp is just a starter template that you can modify until you achieve your goal. If your simian has a shape that is intermediary between human and chimpanzee, it may be a better runner than a chimpanzee. If it has legs longer than a human's, it may outrun humans in a short race. Food for thought :) $\endgroup$ – Renan May 17 '18 at 18:55
  • 3
    $\begingroup$ Google finds chimp top speed is 25 mph. That is freaking fast. Usain Bolt runs at 27 mph so he is safe from the chimps. Not me. $\endgroup$ – Willk May 17 '18 at 22:48

Giant Squirrel power!

Sure our normal earth squirrels are nowhere big enough to outrun a human, so you'll need to scale them up to some degree, but otherwise I think they fit the bill quite nicely.

  • Jump far and high

    Absolutely, jumping far is obvious and they can also easily jump upwards up to or more than 5 times their body height.

  • Climb adeptly


  • Sprint short distances

    Squirrels don't really "run" on the ground, they have more of a long jumps thing going on, but if you make a larger version of it, I think it should be able to reach human speeds.

  • Vault over obstacles

    Mmh, I'm not very sure about the literal meaning of this. Squirrels have much more power in their hind legs, but they're able to pull their bodies upwards once they latch onto somewhere.

  • Swing

    I think if you want true 'rope swinging' is tricky for anything that isn't monkey-like. As an alternative use a flying squirrel - they can easily cross chasms, even without ropes!

  • Roll without hurting itself

    Squirrels can generally land without problems even after long jumps. They can also squeeze through pretty small holes - basically anything that fits their head (the rest of the bodies only looks big if the sit somewhere)

  • Run up near-vertical surfaces

    Squirrels can even 'run' down vertical surfaces

  • Pull itself onto a surface when hanging from the edge of it

    I think this is almost the same as vaulting, at least for squirrels^^

  • $\begingroup$ I more meant swinging as in hanging from a horizontal bar/branch and moving forward. $\endgroup$ – SealBoi May 18 '18 at 16:02

I'm not sure if this is 100% plausible, but I've been thinking about this for a while now and am confident I can answer my own question.

Jumping: For this, I assume the creature would need powerful, muscular legs. I was thinking about this some more, and I had an idea:

Biological pogo sticks on the hind legs? My theory was that the creature pushes a weight down on some form of naturally-occurring spring, then releases. The energy released would, hypothetically, launch the creature further than it would with standard hind legs. The forelegs would have normal feet, though.

Climbing: On its forelimbs, the creature has sharp claws which dig into the "bark" of the alien tree analogues. Obviously, the hind legs are pogo stick stumps, so they would have an opposable "flap" with adhesive mucus on its underside, which would be used as a normal "foot". This would grip the tree-trunk, or the ground when running. The mucus wouldn't be too sticky, as too much grip could be a problem for speed and agility.

Running: A lot of people seemed to think this was the odd one out. I disagree, as there are loads of arboreal/agile creatures today that can run fast. The powerful leg muscles required for jumping far would also be useful for short dashes and sprints. Also, if you've seen how a cheetah runs, you'll find it's a rather similar movement to vaulting, indicating similar skill-sets required.

enter image description here enter image description here

I should also let you know that, in a short-distance run, humans are one of the slowest mammals, so outrunning a human athlete isn't that hard for a quadruped.

Vaulting: Like climbing, all you really need here is strong forelimbs. I don't think that this creature could perform all the vaults that humans can (especially those where the vaulter swings his/her legs to the side), but it could definitely perform a simple "kong vault" without difficulty.

Swinging: Once again, strong forelimbs and some form of manipulator is all that's required. The creature would jump, grab the bar with its forefeet-hand-things, and bring its body forward to cross the gap.

Rolling: A flexible spine and good shock absorption should do the trick. For absorbing shock, the animal's "scapula" or alien equivalent could move like a pendulum, as it does in cheetahs. This would also increase stride length.

Vertical running: Good grip is really all the creature would need to do this. This would come in the form of the already mentioned claws and adhesion on the feet.

Pulling itself up: Strong forelimbs once again. That's pretty much all I need to say on this subject.

Conclusion: The creature will have a body plan similar to that of an ape, but run like a cheetah on the ground. Muscular hind- and forelegs help with running, climbing, jumping and swinging, while mechanisms in the hind legs similar to pogo sticks launch the creature forwards and upwards when jumping. On the pogo sticks, there are opposable flaps that function as feet when climbing and running. On its forelegs, the creature has claws for grip and defense. This is a rough drawing of what I think it would look like, how the hindlegs work and how it climbs:

enter image description here

It would rarely be seen in the stance shown, as it is almost constantly moving when awake. The common name will probably be changed later, I just put it down for now.

If you have any critique for this design (I am particularly interested to know if the pogo stick idea would work), please let me know.

  • $\begingroup$ You should check out Kangaroos, Grasshoppers and Fleas, they have something similar to the pogo stick (as drawn I don't think that would work but the idea of storing mechanical effort in legs is used in several marsupial and insect species). $\endgroup$ – Tim B May 19 '18 at 18:49

For the locomotor skills you required, I'd say the human body plan is enough, albeit with slightly longer arms and three-jointed legs for quadrupedal motion, a prehensile tail for high-speed maneuvers, an opposable toe for each foot, and a highly flexible membrane connecting the forearms, hips, and forelegs for gliding and rolling.

The creature would like a cross between a monkey, a flying squirrel, and a cat. Momo from Avatar:TLA would be the closest creature, minus the oversized ears.



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