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It is a common sight a lot of speculative terrestrial cephalopods and especially octopuses and not just that also is common see fictional works with creatures or characters with strong tentacles that can carry big objects.

Octopuses have great mobility under water, but all changes on the land as the gravity won't permit that the octopus could support its own weight to rise above the ground and not keep crawling on the ground, tentacles are not strong bones or exoskeletons.

So my principal comparison with the strongest tentacles are the elephant trunks, but even if these both are boneless muscular structures, are very different, for that my doubt is, what kind of adaptation should suffer an octopus to support its own weight with its tentacles? and even more is it possible that these tentacles will be stronger to hold biggest objects?

But now that was the case of the conventional cephalopod tentacles. Letting it aside, maybe a new tentacle-like structure that is not a real octopus tentacle for example a very segmented arm or column that could have the flexibility of a tentacle (something like the Dr. Octopus arms but in a biological way). But what I really I'm searching is something like the next images

So finally my principal requirements are:

  • Capacity to be erect out of water.
  • Enough force for hold at the least the half weight the creature which have this limbs.
  • Flexibility
  • Optional high movement speed.

(I've been searching about and asking in other sites and here are the given proposals: Reddit, Worldbuilding.SE, maybe you have other alternatives.)

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  • $\begingroup$ Closely related worldbuilding.stackexchange.com/q/38996/30492 $\endgroup$
    – L.Dutch ♦
    Nov 20, 2020 at 9:14
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    $\begingroup$ Does this answer your question? Why would a land creature have tentacle-like appendages also see an elephants trunk. $\endgroup$
    – John
    Nov 20, 2020 at 16:39
  • $\begingroup$ I am new here so I dont understand all the rules, I thought my question was enough specific for not be compared with others, even I let similars in which I say that not were enough for me, who's the manager for close questions?, I dont want to be insulting, but, Does he or she read it and saw the links?, Im almost sure that it could clear things up. $\endgroup$
    – Drakio-X
    Nov 21, 2020 at 5:07

2 Answers 2

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This will be limited mostly by your creature's body and limb size. There are several examples in nature of tentacle-like structures capable of supporting their own weight out of the water:

  • Snakes
  • "Soft" worms (without a rigid exoskeleton)
  • Myriapods and/or "hard" worms (with a rigid exoskeleton)
  • Monkeys with prehensile tails

Because of the square-cube law, the bigger/heavier this creature is, the more of these appendages will need to be "hard" (bones, exoskeleton) and the less could be "soft" (muscle, joints). At some point evolution will simply favor rigid arms and legs over flexible tentacles. Under Earth gravity, this will be quite below human size, so you'll need to come up with some explanation of why is this an advantage at all, or just magic/handwave it away.

For example, 10kg spider monkeys are capable of hanging their full weight from their tails. A small humanoid at 40kg with at least four tail-like tentacles instead of legs might believably lift its own weight from the floor, assuming a pelvis-like structure with relatively large muscles at the base.

You probably don't need all of these to be fully prehensile, so maybe there can be two kinds of tentacles: stronger semi-rigid "legs" for bearing the load of its own weight, with thicker bones than a monkey's tail, and weaker flexible "arms" which can be fully prehensile, maybe even boneless as an elephant's trunk. Or maybe you can have a combination of both kinds in the same tentacle, with the base being thicker and more rigid and gradually thinning towards the tip, but in this case your creature would probably "step" on a (probably padded) mid-tentacle section and keep the tips up.

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Tentacles in the air would need some rigid support. This old stiff/slack rope trick can give you an idea:

Classic Stiff Rope Magic trick

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  • $\begingroup$ Elephant trunks do not have any rigid support. $\endgroup$
    – Logan R. Kearsley
    Nov 20, 2020 at 19:23
  • $\begingroup$ @Logan R. Kearsley trunks don't have sufficient strength, compared to elephant own weight. $\endgroup$
    – Alexander
    Nov 20, 2020 at 19:26
  • $\begingroup$ So put an elephant trunk on a creature with an otherwise smaller body. They can lift tree trunks, so I doubt, say, holding a mini horse would be much of an issue. $\endgroup$
    – Logan R. Kearsley
    Nov 20, 2020 at 19:28
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    $\begingroup$ @Logan R. Kearsley when lifting things, elephant leverages its body mass and body muscles. A horse-sized elephant with full-size trunk won't be able to lift a tree trunk. $\endgroup$
    – Alexander
    Nov 20, 2020 at 19:42
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    $\begingroup$ @Logan R. Kearsley Notice that an elephant is lifting using his neck and leg muscles, not trunk muscles. Elephant lifting log Trunk muscles are used just to hold the log. Similarly, when we are lifting a dumbbell, we are using our more massive upper arm muscles, not hand grip muscles. $\endgroup$
    – Alexander
    Nov 20, 2020 at 19:55

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