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An idea that I've seen many times and I wanted to use in some concept creatures is the tripedalism suported by two real limbs and the caudal part of the body, for practical terms the tail.

I remember other question about tripedal creatures, but the focus was on make that creatures radially symmetric, but in this case I´m asking about bilateral creatures.

So next a very basic diagram of what I want, the number of tail articulations and position can change. In general is based of the slow motion walking of kangaroo, but the tail is completly adapted to full time motion and weight support.

The problem is related with the convivence of these tripodal creatures in an enviroment with other normal quadrupedal and bipodal creatures. Enviroment in which comptence would exist, so the problem is about limitations that I've read tripods could have, like problems with weight balance, sprint while running, turns in curves, etc.

And the question is, are these limitations as problematic as they seem and reduce the competence capacity of this class of creatures and if so, how could they be solved?

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    $\begingroup$ difficulty turning at speed is normal for 4 limbs as well, there is a trade off between speed and maneuverability no matter how you locomote. we can actually assess the environment animal live in paleontologically based on this, plains animals can focus on speed while forest dwelling animals have to maintain a degree of maneuverability at the cost of speed. $\endgroup$
    – John
    Jul 23, 2021 at 14:18
  • $\begingroup$ @John. Interestign, although a little off the main question, what kind of niches could occupy this kind tripodal creatures? Is there a noticeable differentiation between what they could and couldn't do compared to bipedal and quadruped? $\endgroup$
    – Drakio-X
    Jul 24, 2021 at 2:21
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    $\begingroup$ that all comes down to limb proportions, the difference between a mole and a gazelle comes down to limb proportions. one question you will have to answer, where is the anus? $\endgroup$
    – John
    Jul 24, 2021 at 2:38
  • $\begingroup$ @John Well, the anus is in the ventral region in front of the base of the tail $\endgroup$
    – Drakio-X
    Jul 24, 2021 at 4:44

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If I remember correctly, kangaroos use their tail as a third leg to keep their balance, both when hopping and standing.

They don't seem to have severe disadvantages when it comes to moving, and being able to have the forelimbs free from the supporting task can be an advantage in certain environments, for example because it allows to grab for food.

From a mechanical point of view, 3 points of contact are sufficient to have a stable position on the ground (to paraphrase my university professor, a table with 4 legs has one leg more than needed to be stable). This is an advantage with respect to bipedal creature, which need an active control to keep their balance while standing, when a 3 contact creature can passively stand upright, saving energy.

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  • $\begingroup$ I searched about that, but in the case of the tripods are in a medium term between quadrupedal and bipedal creatures and while they are more stable than bipedal and just as stable as quadrupeds, if a quadruped hurts a limb, they have three left to stand on and most of the bipeds that exist in real life normally fly. Three contacts on the floor still seem troublesome $\endgroup$
    – Drakio-X
    Jul 24, 2021 at 4:50

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