Feasibility of Bipedal Chelonians

Question

I'm creating a creature that possesses an outwardly Chelonian-like appearance. However, the creature is bipedal. Specifically, the creature possesses upright, pillar-like hind limbs, as well as a Kangaroo-type posture.

However, this was when I began to wonder -

Can an otherwise Chelonian-type creature plausibly be bipedal?

Would the presence of not only a shell, but the arched spine and enclosing pelvis found in the tortoise be a detrimental design that may not only hamper bipedalism, but outright stop it?

Preliminary (and very low-quality) sketch -

Any answers would be greatly appreciated.

Answer 1

Armadillos can do it.

https://www.flickr.com/photos/jpmckenna/4382969406

These guys have big shells and can stand on two legs and, according to the internet, even walk around some that way. Pangolins are really impressive as regards bipedalism - their scale-mail shells are less chelonian appearing but they walk all around on their hind legs.

I think the key to walking with a shell is center of mass. A shell centered farther back might actually help tip the front of the body up and facilitate bipedalism - that looks to be what the pangolin has going on (plus a weighty tail). Your bipedal chelonians could have elongated shells or small upper bodies, or exaggerated T-rex / pangolinoid tails.

Answer 2

Based on your comment I'll assume your goal is to have a bipedal alien with a solid turtle shell.

The first thing to become clear about is the grade of protection the shell should offer. If protection is of little concern, you should go with the flexible armadillo-type proposed by Willk. Ninja Turtles also come to mind. Their shell protects only the back, but not the front and extrminies and is actually more of a hindrance than advantage.

If these aliens have to survive physical attacks from predators and should be bipedal, they either need a solid shell in the front as well or lay down on their vulnerable bellies when attacked.

Depending on the wheight of the shell, they might need strong limbs like those of elephants or rhinoceroses. If they cannot draw their legs into the shell for protection, they need extra shells on them (much like a knight in plate armor). If they're supposed to draw them in, you might need a rather big shell that's half empty when all appendages are extended and probably more joints than turtles have to move a pillar-like leg into a solid shell. In any case, short legs seem to be most feasible.

Now to the lifestyle: how would they eat food and drink water? Bending down, reverting to quadrupedal style to drink some water just to stand back up seems rather cumbersome. They could have elephant-like trunks instead or big, nimble hands that can scoop up water. Either kind of appandage would have to be long enough to reach the ground with, which would favor a small, stocky torso rather than the elongated shape of turtles.

Since intelligent creatures tend to have large brains, the head might be rather big. It would be an advantage to keep the brain inside the shell at all times, so the alien might poke just its face out of the shell instead of the whole head. Keeping the problem of eating and drinking in mind, they might have their head-opening at the middle or bottom end of the shell instead of on top.

To sum it up, there are 2 major anatomical variations feasible:

The nimble tool user

• short legs retractible into the shell

• long, slender arms with nimble hands retractible into the shell

• short, stocky shell with enough room for a big brain, internal organs and all appandages

• only eyes and orifice can be extended from the shell, brain stays in the shell

• uses tools to make up for the shortcommings of its slender arms

the primitive forager

• shell with very pronounced dome. Brain and lungs positioned at the top of the dome

• head and heavy organs at the bottom of the shell to keep its balance and reach the food

• short, pillar-like legs with broad feet to keep its balance

• either elephant-like trunk or very short arms

Answer 3

A turtle's forlimbs point forwards, due to how the turtle's shell is arranged. This would make a humanoid turtle look strange, but might not affect their dexterity much.