Aside from making it hard for surgeons to operate, the rib cage is essential. It’s a calcium battery, frame for our muscles and protects our organs and bone marrow. Ribs by themselves (like in snakes) sacrifice durability for flexibility. A broken rib endangers vital organs, a bit counterproductive considering their purpose.

The creature I have in mind is one with a rib cage made of separate bones (ribs) that are crossed together like hands, allowing them to be opened and closed similar to a bivalve. Fully opened their ribs would look like hair clippers. This would expose the organs, leaving only skin as protection but for the sake of the question we’ll assume that the organs are somewhere else or protected by another bone layer. The overall morphology of the creature is dog-like and it functions as an obligate carnivore in my sci-fi setting. It’s not a mutant or anything it just adapted or mutated to be this way. But why? I’m rather uncertain about the feature so I’m looking for a plausible explanation for it.

What would these ribs be used for? (Besides making a veterinarians job easier.)

  • $\begingroup$ Can you give a citation on that 'ribs = calcium battery' claim? $\endgroup$
    – bukwyrm
    Commented Oct 26, 2021 at 14:55
  • $\begingroup$ Also, could you comment on that hands analogy? If i stiffen my fingers and then interlock my hands together, the fingertips look out to the other side, so that would be quite the poking-risk with ribs. image.shutterstock.com/image-vector/… $\endgroup$
    – bukwyrm
    Commented Oct 26, 2021 at 15:04
  • 1
    $\begingroup$ @bukwyrm Good point. The hair clipper analogy is better, though the crossed hands gives a good thing to look into. Perhaps it's useful as well? Regardless if the ribs being too long poses a problem natural selection will shorten them. Here's the citation you asked for: nationalgeographic.com/science/article/… $\endgroup$ Commented Oct 26, 2021 at 15:11
  • $\begingroup$ Ahhh, not the ribs specifically are the calcium battery, but bones in general. Anyways, was news to me. thanks! $\endgroup$
    – bukwyrm
    Commented Oct 26, 2021 at 15:44
  • $\begingroup$ It houses a wave-motion gun inside the creature's chest. $\endgroup$
    – Faito Dayo
    Commented Oct 26, 2021 at 16:53

1 Answer 1


It swallows large prey whole

Take the example from a snake's lower jaw; it is composed of two bones with soft ligament in between. When a big prey needs to pass through its flexible throat, the boney parts split apart and the ligament stretches.

snek jaw

Snakes do not have a rib cage per se, they have an array of loose ribs that can split open to accommodate a healthy dinner. Dogs do possess a sternum, but you can replace that with ligament option just like the snake jaw.


This anatomy is still compatible with general dog morphology, but it may have a hard time doing zoomies when carrying a big prey in its tummy. Consider a hibernating cycle; the creature could have its dinner in the autumn and digest it over the course of weeks or months while it takes a long nap.

  • 2
    $\begingroup$ the snake has exactly the rib cage requested in the OP. Snakes have no sternum, and (in addition to jaws) expand their rib cages to accommodate big meals exactly as you put forth. And since your answer is all snaky already and you are 95% there I am ashamed to put more snakes in a new answer but hope you will put some snake rib cages in yours. $\endgroup$
    – Willk
    Commented Oct 26, 2021 at 14:46
  • $\begingroup$ @Willk I thought I would mention a sternum option since dogs possess one (the creature was mentioned to be dog-like) but sure, I can improve that phrasing :) $\endgroup$
    – KeizerHarm
    Commented Oct 26, 2021 at 14:50
  • $\begingroup$ @KeizerHarm Shame, I should have mentioned that my creature can't split its jaw open. Regardless a good logical answer. $\endgroup$ Commented Oct 26, 2021 at 16:09

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