Could a bird respiratory system still work without the same bone structure as a bird?

Question

I have a creature that has a humanoid torso and abdomen except for it being larger to accommodate air sacs. The structure of the posterior air sacs is that it wraps around the organs; this means a portion of it is in the front of the abdomen. If it wraps around the organs, would it squish them too much when it inflates/deflates? It has a flexible spine; not rigid like birds. The pelvic bones are like a human's(except for it being longer front to back to accommodate larger torso/abdomen), not a bird's. Human pelvic takes up more space in the abdomen.

Even with this differing structure, could it properly breathe with a bird respiratory system? More specifically, since the humanoid pelvis takes up more space, can I have the air sacs wrapped around the other organs in the midsection without that causing issue?

Answer 1

Yes, in fact it did. Also your mostly worried about nothing.

The bird respiratory system evolved before pneumatic bones, in fact it is what allowed pneumatic bones to evolve. you can't migrate air sacs into bone until the air sacs exist. We know air sacs evolve outside the bone and only later evolve into them.

Air sacs don't squish the organs any more than having a diaphragm moving up and down does, if anything they compress them less because they don't all need to inflate at the same time to work like mammalian lungs do.

Also getting knocked back and forth gently like you describe does not bother organs, it can even benefit them by imparting mechanical energy that can be used to move material. Consider how much bending over, or running in quadrupedal mammals squish or throw the organs around. Or even better consider a bounding kangaroo.

As for the pelvis taking up more space, have you seen early dinosaur pelvic girdles, they take up a LOT of space, its a non-issue. Also I would debate that human pelvises take up more space. The flight muscles of birds take up a lot of space but the actual internal organs space volume of the torso is not any larger.

Answer 2

i know part of your answer; i do not know if your creature will work but i found this video https://www.youtube.com/watch?v=kWMmyVu1ueY and this web site https://projectbeak.org/adaptations/skeletal_fused.htm

if you gave a human a bird lung system you would need more room to fit it and there might be more problems I do not see

Answer 3

Would human organs get squished, given an avian lung system? If the creature you describe is a species in its own right, everything will fit and work as it should, as evolutionary presssures will already have taken out non-viable individuals. Your only problem here will be to imagine what such a creature will look like. There are many sizes and shapes of birds, a large almost upright penguin might be a better model than an albatross.

Butif your creature is to be a chimera ... bred in a lab using DNA from both an avian species and a human species ... expect a lot of problems. I researched chimeras in detail for my present WIP, that features human-dolphin chimeras who also feature in a short story "Scrim's Story" published in Worldbuilding Magazine

I imagine both human and avian organs getting squashed. An avian lung system that lacks some of its airsacks causes flightlessness through the creature not getting enough air in. The human heart getting squished causing death a short time after birth due to breathing beginning. Kidneys displaced and or malformed, your creature on dialysis for life. Liver troubles. If any of these chimera live beyond infancy, they will need IV and womb-tanks to propagate.

Then there is the question of bones. With human bones and/or skeleton there won't be any flight, though you might already have factored that in by picking a Ratite ancestor (emus, ostriches, cassowaries) Ostriches can make good the loss of flight. Ostriches can run twice the speed of humans, and complete a marathon in 40 minutes