Unless otherwise noted, the opponent can be up to one size category smaller than the swallowing creature.
T-Rexs in Pathfinder are Gargantuan (a change from 3.5 which I agree with). This means, that by the rules, a T-Rex can swallow a huge creature whole.
Lets pick a huge creature we can relate to. The Elephant.
Now lets picture a T-Rex swallowing an Elephant whole.
......
Yeah, I don't think so either.
With the exception of creatures like a Vurgen's Eel, or maybe some of the more ambitious storks out in the marshes, I can't think of many creatures that can actually swallow whole a creature just one size below them. And I wouldn't count snakes either, as their "swallow whole" is a more out of combat ability. At least, they usually don't begin to swallow the prey until it is dead or at least no longer struggling.
I could see a T-Rex theoretically swallowing a horse whole. Humans, no problem. But the idea of an elephant, a killer whale, an animated wagon, or a 12 ton Storm Giant (which also outweighs the Rex by 5 tons, and would put it past it's heavy load of 8 tons) going down it's gullet is just ridiculous. And since we are dealing with a real (if extinct) creature, "it's magic" or "a wizard did it" doesn't really fly.
Most creatures that are one size category below a swallower will generally fall into at least the medium if not the heavy load, or beyond, of the swallower, barring "supernatural" grade strength or being a quadruped.
I would propose amending the Swallow Whole Text to read: Unless otherwise noted, the opponent can be up to two size categories smaller than the swallowing creature.
Or the Swallow Whole text could be left alone and the T-Rex (and perhaps other monsters) could get some of that "Otherwise Noted" love.
Regardless, the modification is going in for my own game, I just wanted to bring the logistics issue up for others to be aware of.
Nice post! Considering it's mostly been "little" things like people and demi-people being swallowed, I guess I've never really needed to think about this. It does seem fairly (well, EXTRORDINARILY, actually) silly. It's a good thing you picked up on this before I discovered it in-game. You've saved me and my table a serious fit of the giggles. Consider it houseruled.
... now what can we do about that "muscle action closes the wound" thing??? (I realize there is game balance involved - but we play pretty fast n loose at my table, and usually when you come slicing out of some critter's stomach, that critter usually dies horribly.)
Actually, I have found most of the time that RL physics and the game mesh startlingly well. Getting hit full force with a warhammer may indeed knock you down, if you are a level 1 commoner or warrior with somewhere from 2-6 HP. Odds are good you will be at 0 or in the negatives afterwards. Falling damage works fine as well.
To me, its just a matter of perspective on how the rules display themselves in the game world. Of course, I am of the camp that level 5 is the "cap" for most "normal" people. 10 is where you start breaching into the realm of "superhuman" even if you don't cast spells, and 15+ is "powerful to the degree that normal people can't even relate anymore".
Its just a matter of remembering that PC classes, and the people who take them, are not normal at all. They are, by their very nature, the exceptions to the normal rules. The 10th level fighter can fall 200 feet and walk away from it because he is superhuman, same with the 10th level rogue being able to sneak up on something like a bengal tiger and kill it before it even notes his presence.
A small thing I like to use is the "Rule of 15". 15 being the average number of HP a level 1 human might be able to take before that human is truly dead. Or in other words, dead on impact. Beyond the capability of modern medicine and science to save. 15 points from one attack is equivalent to car crashes, industrial machinery accidents, and so on. Utterly and instantly fatal, like torso crushing, decapitation, or being torn apart or split in half. 15 points of damage.
PCs start taking that kind of abuse at level 3. Fighting an Ogre with a greatclub is like bullfighting a truck. But PCs do it. Gotta love those crazy PCs; for without them, how booring our stories would be.
... now what can we do about that "muscle action closes the wound" thing??? (I realize there is game balance involved - but we play pretty fast n loose at my table, and usually when you come slicing out of some critter's stomach, that critter usually dies horribly.)
Actually, since the Pathfinder treatment amended swallow whole to state that a swallowing creature that has had prey escape by cutting through can NOT swallow any more creatures until the wound heals.
Cutting your way out of a stomach would technically leave a fairly small hole, since the stomach stretches to accomodate you, it will naturally contract when you leave it. Damage to the muscle beyond it would be more conerning.
Ultimately, the real world effects of such an exit are blood loss and infection, with infection being both the real killer and the least existing in the game system.
That, and there is a big difference between slicing your way out of a stomach and pulling yourself free (picture the Ace Ventura Rhino Birth scene) and intentionally causing as much damage as you can on the way out (Aliens chestburster style).