Is it possible for a vertebrate creature to have a ribcage/chest mouth?

Question

In fantasy and science fiction cool monsters and creature desgins constantly appear, this feature specifically (a mouth that exists in and occupies a good portion of the ribcage area) doesn't seem to stick to what is biologically or physically possible, but sometimes their body shapes could work or at the least look similar in the real life. So in this case I have the doubt about if its possible that some creture could have an open rib cage as it's mouth or something that could look similiar, this also can be interpreted as a second belly or chest mouth.

These are some examples I found to illustrate better what I mean:

Lastely I saw questions about the possibility of the existance of fantasy like creatures and for me this chest mouth is a very interesting concept i'd like to use, but I dont know about the great changes to the anatomy and organs to make it possible.

Summing up: Is it possible for a vertebrate animal, given our understanding of biology, to have a mouth located in it's chest in a ribcage-like fashon? If so, what changes to it's overall anatomy would be needed in order for this trait to exist?

(I tried to think how this could affect it and I'm almost sure that a thing like this is not currently possible for the earth animals as we know them, maybe alterating the evolutionary story changing the developing of the notocord, so probably bilaterial current creatures are discarded, but maybe some arthropod with retarded mandibules and a lobuled head, but this is very different from the initial idea. So my best current guess is a radial organism like an equinoderm with a centered body mouth but are not vertebrate like creatures).

Answer 1

Reality Check: PASS!
The physiological arrangement you're asking about is within the range of the possible, though, at least for strictly Earth creatures, not within the realm of the probable.

We will have to consider some changes to the basic Earth mammal body plan for this to work. Here's what a human looks like inside without her arms, shoulders, and associated musculature:

The whitish blob in the middle is the heart all tucked inside its pericardium. Off to either side, our happy medical students are retracting the pleura, the whitish sacs that contain the lungs. You can see the great vessels on top of the heart, and the bronchus that joins the lungs to the outside world. Lurking behind all that is the shy and retiring esophagus.

Now, for the purposes of your creature, you don't really want all these bits cascading onto the sidewalk every time it opens its toothy maw to slaver all over its next victim, right, so all these organs will have to go somewhere else. As per that snaky creature in the illustration in your query, the heart and lungs can happily reside down below.

Lungs being what they are, the creature will have to have some alternate means of respiration: perhaps a muscular sac that can, bellowswise, squeeze out stale air and replenish with fresh.

But back to the chest!

So, here's what a human looks like with the ribs and breastbone in place:

Kind of inconvenient for your creature, that pesky breastbone!

So what we'll do is split it down the middle, and use the bone to secure some nasty, big, pointy teeth. Like the girlbeast you referenced, we can also have an outer array of teeth attached to individual bones whose musculature allows some freedom of movement. The main action of the maw will be accomplished by powerful muscles that attach to the ribs along the spine: these will open and close the mouth very nicely. Lastly, the ribs will be entirely of bone, without any appreciable cartilage.

There are not a lot of good anatomical studies of such creatures. Here's a reasonable one:

Pretty much building up on the ribs and halved sternum we'll have some standard oral mucosa (lips, gum tissues, with optional tongue). Pretty much the entire thoracic cavity will be now be one gigantic maw, all pink and slobbery. The illustration shows a standard uvula at the back of the oral cavity -- but I don't think that makes much anatomical sense. Basically, the entire inner surface will be gum tissue surrounding bony plates with structures a lot like the palatine rugae:

While the terrifying fangs look horrible as they're rending flesh, it's going to be the job of the inner bits to crunch and crush to a frothy pulp. Possibly the inner teeth will be like the oral plates of a ray.

Basically, if you're lucky enough to get past the outer layers of fangs, once you're crushed a bit, it'll just be a short trip through the gullet and down into the stomach!

Answer 2

Crabs don't have necks... depending on the species, when they stand up, the mouth seems to be in the middle of the "chest".

Crabs have evolved from creatures similar to lobsters, but somewhere along the way they lost their tail. In the same process their abdomen took its current shape. An alien creature that undergoes the same process and then becomes more humanoid (including developing vertebrae, to sustain a humanoid stance and gait) might have a mouth where the chest is.

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I also like to believe that vertebrates ultimately come from roundworms. AFAIK all roundworms have mouths at the front end of their bodies. Some flat worms, however, have their mouth right at the middle of the body - should vertebrates have evolved from them, they might have mouths at the "chest".

Answer 3

What is the point of a big mouth, if you have no place to put the food? There is a reason why animal mouths are all in proportion to their bodies.If you want a really big mouth, you have to create a really huge body, that can contain a digestive system proportionate to the mouth.

Your next problem, is how to get food to the mouth. Mammals have the mouth on their head for a reason, because they can move the head around to where the food is. As an alternative to moving the mouth, you would need prehensile mechanisms that are able to bring the food to the mouth. A mouth on the chest does not offer much mobility. In which case, a mouth with sharp gasping teeth would have no benefit. The prehensile mechanisms have already captured and grasped the food.

Now, you need to consider the pre-digestive function of the esophagus. The stomach is where it is for a reason - the food goes through a pre-processing stage as it goes down the esophsgus. It also acts as a valve, preventing the contents of the stomach from regurgitating. Even snakes have a lengthy esophagus. So your creature would need a way to keep the food in the stomach, a clear division and buffer between the mouth and the stomach.

So where are we? A large animal with enough limbs to have at least a pair free for food aquisition, and considerable room between the mouth and the stomach. Something with a very stretched torso, perhaps, or a horse-like creature with two extra limbs, a centaur, with the mouth in the lower chest between the shoulders, still allowing for an esophagus, and perhaps allowing the creature to kneel down on its front legs and eat from something on the ground.

Answer 4

Mimetics and Extreme Body Mods:

I think it's unlikely for a giant mouth in the chest to naturally develop in a mammal. That being said, I can think of a couple of ways the APPEARANCE of a human with a giant mouth in the chest could evolve.

First, why a giant mouth in the chest? Mechanically, it doesn't make a lot of sense. The best logic I can think of is that the species doesn't chew food so much as "swallow" big food items and carry them around until they can conveniently digest them (possibly externally). A big mouth parallel to the stomach doesn't provide a good digestive system. Maybe they start the digestion this way, then regurgitate the food in a sort-of composter, applying additional enzymes as needed. So now we need to consider why and how of this.

I would suggest this organism is an ambush predator amidst hostile humanoids. The body looks human, because the prey is human. A "thin" predator murders someone, hastily stuffing the body (or at least the organs, the best part) into their stomach to carry away in secret. Then the "Fat" predator removes itself from the murder scene with the food (not even chewed, just gulped).

The appearance of being human is camouflage. They mimic humans to close to killing range. They could easily be intelligent, if desired, but regardless would need to be clever. Children, being small, would be ideal prey (thus the appearance of an innocent girl, but a seductive/maternal female would also be a good choice of shape for foolish males).

Any number of species could evolve closely with humans and mimic their shape to prey on us. The head might not be a head; it could be a modified limb used for grabbing (that may thus hinge open way further than a natural mouth would. I imagine a large claw/pincer resembling a head). A lizard might have an enormous head taking up most of it's "body," with the "head" being a decorative part or a grasping limb. Several of you images look like arthropods, which have an extremely diverse set of body shapes. In a previous question, I suggested an octopus could mimic skeletons, and the visuals on some of your images are very octupoid. The "mouth" could actually be a ring of tentacles resembling a mouth, but the actual mouth might be tiny in comparison. The teeth might even be tiny arms or tentacles to grasp food or guide it to the actual (small) mouth.

Another possibility is this organism is like a slime mold, able to readily change its shape. The "mouth" would really be the organism shaping around someone, since it doesn't really have its own distinct shape. It would kill someone, then engulf them, then (if it can somehow move this way) "walk" the engulfed body off to somewhere the whole thing can hide and gradually digest its prey. For a ghoulish variant on this, some wasps are able to pith cockroaches and make them follow mechanical commands. Imagine doing this to a person who then could be forced to walk to their doom, possibly even dig their own grave, then climb in and bury themselves.

• As one additional possibility, I would suggest this could be a form of very extreme body modification. People have suffered injuries where their stomach is open to the outside, and even lived that way for years. A person into extreme body mods could have their stomach altered to be open, and their skin modded to look like a huge open maw. Implants would resemble teeth. This wouldn't be functional, but people are crazy/sick/experimental and such an appearance could be possible with enough medical science.