First time posting here but I would like to get some help with an issue I have.

I have a planet that has 30% more gravity than earth. I have terrestrial animals with an exoskeleton, they stand at a height of 1.2 meters. For context, they are bipedal and have a theropod-like body plan. I know I will need a biological material that is stronger than chitin that can provide adequate support while being lightweight. It will have to be able to withstand strong bite forces and flexible enough to absorb the shock of a landing from 10 to possibly 15 meters.

Is a bone exoskeleton a feasible solution here? Perhaps the weight of the exoskeleton would be too great?

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    $\begingroup$ There are many extant animals with bony exoskeletons. They are called turtles. So we positively know that a bony exoskeleton is perfectly possible. $\endgroup$ – AlexP Mar 24 '20 at 23:06
  • $\begingroup$ Well, turtle shells are just a modified portion of the endoskeleton, it's not a true exoskeleton like with insects. The creature I have in mind is much larger than a turtle and more mobile so weight is an issue. $\endgroup$ – Pesterjest Mar 24 '20 at 23:09
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    $\begingroup$ Well, the shell of turtles is (1) made of bone, (2) it is part of the skeleton and (3) it is placed outside the body. That makes it a bony exoskeleton, and a perfect example that bony exoskeletons are possible. With the weight I cannot help; bone is heavy. (The scutes which make up the armor of crocodiles are also made of bone.) $\endgroup$ – AlexP Mar 24 '20 at 23:12
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    $\begingroup$ @Pesterjest Most of a turtle's skeleton would be considered an exoskeleton. The shell isn't just scutes, it's made of modified vertebrae, ribs, and whatever the plastron is made of (its origin is controversial). The limbs and head aren't. The keratin covering is just to keep the bone from getting damaged, not much different from how insect cuticle typically has resistant outer layers. $\endgroup$ – user2352714 Mar 25 '20 at 3:02
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    $\begingroup$ The problem you have is an exoskeleton always weighs drastically more than an endo skeleton. on a high gravity planet there is even more reason large exoskeleton creature won't evolve. the only way around this is to have a material that is just as strong but also drastically lighter, which bone is not. $\endgroup$ – John Apr 3 '20 at 3:42

30% more gravity isn't so much that you need to have radical limitations on biology. Did you ever have to do an egg-drop machine in school? Bone easily works. Most biological materials are strong because of shape. Think seashells, which can be incredibly strong or quite brittle depending on if they are intact. Don't minimize chitin - it's usually very thin in most organisms and is very strong. I would also suggest something like carbon fiber if we are talking genetic engineering and not evolution (think bullet-proof vests and combat helmets). if the shell has to resist attack, adding spikes, barbs, or quills is a common augmentation and would lighten the requirement for a heavy shell. For falls, a thinner light material with aerodynamics or parachute-like properties might work best. Decide based on the biggest evolutionary pressures.


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