In my fictional universe, there lived a unique creature resembles today tortoises but with spherical shell. My question is what evolutionary advantage(s) does this shape have? How would said creature move on the ground and probably in water? This question is inspired by a bowling ball.

  • $\begingroup$ May the creature "stick out" a head and appendages like a turtle? $\endgroup$ – Mikey Jul 21 '15 at 5:49
  • $\begingroup$ @Mikey yes definitely $\endgroup$ – user6760 Jul 21 '15 at 6:22

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The problem would come if the creature cannot be loose inside the shell. Propulsion could be achieved by changing the centre of gravity - perhaps by moving water around in a special vesicle.


Spherical shells would be terrible on water. We've all seen those plastic balls with people inside going absolutely nowhere. If they are underwater however then there are definite possibilities.

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puffer fish

  • $\begingroup$ I was tempted to accept your answer because that look on the fish shows its in agony now you may go ahead and deflate it. $\endgroup$ – user6760 Jul 21 '15 at 15:22
  • $\begingroup$ With small ridges or "fins" on the outside of the shell (or plastic ball), you could get some traction and movement on the water. $\endgroup$ – Michael Richardson Oct 5 '16 at 13:32

The creature could be the perfect size to be a meatsnack for other creatures. Tortoise shells provide a great deal of protection from the crushing jaws of predators, but a really good spherical shell would be much stronger. It would be like a natural bear canister!

Unrelated, it would be really nifty if it had many holes to stick its head out of, and spun around inside the shell as needed. Why worry about getting flipped over on your back, if you can just turn around inside your shell and keep on trucking!

  • $\begingroup$ Why do the animals of earth have legs instead of wheels? There are evolutionary limitations that would prevent such a creature from existing. The closest thing we have to such a creature is an armadillo, but notice that they can unwrap and walk. A creature with a spherical shell would also have to be able to move around in it. $\endgroup$ – Neil Jul 21 '15 at 6:23
  • $\begingroup$ Great idea! mole will definitely love to stay in it. $\endgroup$ – user6760 Jul 21 '15 at 6:26
  • $\begingroup$ A what canister? $\endgroup$ – Kreiri Jul 21 '15 at 11:29
  • 1
    $\begingroup$ @Kreiri A bear canister is a plastic container (usually a cylinder) you put food in when you are hiking in the wilderness to protect them from bears. They're designed to be terribly hard for the bears to get their teeth around. In Yosemite, where they are mandatory for all backpacker, bears have been known to get so frustrated with them that they just knock them into the river, but now they know better and simply ignore the containers entirely. $\endgroup$ – Cort Ammon Jul 21 '15 at 15:00

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