Dinosaurs under water

[dinoguy]

Sorry if this isn't scuba diving exactly, but I've tried searching the internet and really can't find any good sources of information, and it does have to do with the physics of being underwater.

I'm taking a class on Dinsosuars and there was a bit of discussion about whether the really long necked dinosaurs could have spent at least a small amount of time underwater and used their long necks as snorkels.

One thought was that a dinosaur with a 30+ foot neck is going to have his lungs at at least 40 feet underwater and that he won't be able to fill his lungs (not to mention the length of it's neck) under that much pressure. The counter argument was that if a human can dive to 90+ feet and fill his lungs then a dinosaur shouldn't have a problem doing it at 40 feet under.
I was under the impression that this was due to the fact that the air a diver is breathing is also presurized. If a human was trying to breath 1 atmosphere are in 2 atmospheres of pressure (about 33 feet) would a human have trouble filling his/her lungs?
I guess I don't know enough about breating unperssuized air at depth. Would a 35 foot snorkel be possible if you already had lungs that were capable of moving 35 feet of dead air?

I guess I'm not really looking for an answer on the dinosaur aspect, because there really isn't much way of knowing for sure and there is other evidence to support that fact that they probably didn't spend much time in the water. But I am interested in just knowing more about how the physics of a long necked dinosaur breathing underwater would work.

 

[H2Andy]

one of the early experiments with diving was to have a hose from the surface through
which a diver could breathe while submerged. other than for shallow depths,
this did not work because the water pressure constricted the hose and did not allow
the air to pass through.

however, if you have enough pressure on the hose from the inside out, like when you
shoot compressed air throug it, then it workds (that's how hard-hat NAVY divers
use to dive in the old days).

so wouldn't the question be, "can the air in the dinosaur's airway excert enough pressure from the inside out to counter the water pressure and thus not be "choked"?

i don't know the answer. just thinking outloud.

 

[dinoguy]

Well, thats the kind of information i'm looking for, thanks.

I'd say dinos breating low pressure air is a pretty safe assumption.
So (and this is totally hypothetical for the sake of curiosity) what if they had some kind of strong rigid neck and chest that didn't collapse under pressure. How much harder is it (perhaps in terms of muscle required) to fill your lungs at 40 feet than at the surface?

 

[DA Aquamaster]

A person can breathe through a snorkel only about 18 inches long before the suction required becomes too much for any kind of sustained breathing effort. Sucking air at a negative pressure of 40 inches of water is possible but not for long periods. 40 feet would be out of the question.

A large dinosaur would require either truly epic diaphragm muscles or a very strong and largely pressure resistant chest to be able to breathe while it's lungs were 40 feet underwater.

My thoughts on large sauropods was that they walked on land and used their long necks to reach the tops of tall trees. I suspect wading in shallow water would have also been possible as long as their body was not too far under water. But I don't really see a practical reason for it and it seems to me that the risk of a 30 ton dinosaur getting bogged down in a soft bottom would outweigh any evolutionary advantage of grazing on aquatic plants on a regular basis unless other sources of food were scarce.

 

[MarkH]

From what I understand, you (or a dinosaur) would need pretty strong lung muscles (diaphragm ?) to breath through a tube to the surface at 40 feet depth. I don't think it is practical (or possible?) for humans, but I suppose the dinosaur could have specially adapted "super muscles" to counteract the pressure of 40 feet of water and breath atmospheric-pressure air from the surface. I may be way off, not being an expert or anything. I'm actually only semi-literate so don't quote me if you're writing a thesis.

 

[dinoguy]

A person can breathe through a snorkel only about 18 inches long before the suction required becomes too much for any kind of sustained breathing effort. Sucking air at a negative pressure of 40 inches of water is possible but not for long periods. 40 feet would be out of the question.

I always thought that the problems of a long snorkel were due to having to move much more dead air than your lungs can normally handle, not the pressure. A long necked dinosaur wouldn't have been truly snorkeling because he normally moves that much dead air whether breathing on land or in the water.


However I agree. I find it very unlikely the sauropods would go in deep water. But that doesn't mean that supposedly smart scientists haven't proposed it in the past, and some people still believe it today. I'm just trying to find some facts to back up the pressure argument.

 

[DA Aquamaster]

From what I understand, you (or a dinosaur) would need pretty strong lung muscles (diaphragm ?) to breath through a tube to the surface at 40 feet depth. I don't think it is practical (or possible?) for humans, but I suppose the dinosaur could have specially adapted "super muscles" to counteract the pressure of 40 feet of water and breath atmospheric-pressure air from the surface. I may be way off, not being an expert or anything. I'm actually only semi-literate so don't quote me if you're writing a thesis.

40 feet of water exerts a pressure of about 18 psi. and consequently 18 lbs of force would be required for each square inch of chest area to draw a breath. That 18 lbs per square inch adds up fast to become 2,592 lbs per square foot and 27,715 lbs per square meter and a chest area of 3.6 square meters would require 100,000 lbs of force to inhale.

So we would be talking truly awesome super muscles that would have had to have been anchored to some very strong and rigid bones. Bones like that do seem to be consistent with what has been found in the fossil record.

 

[dinoguy]

40 feet of water exerts a pressure of about 18 psi. and consequently 18 lbs of force would be required for each square inch of chest area to draw a breath. That 18 lbs per square inch adds up fast to become 2,592 lbs per square foot and 27,715 lbs per square meter and a chest area of 3.6 square meters would require 100,000 lbs of force to inhale.

So we would be talking truly awesome super muscles that would have had to have been anchored to some very strong and rigid bones. Bones like that do seem to be consistent with what has been found in the fossil record.

Interesting. This is exactly the kind of thing i'm looking for. Thanks.

 

[DA Aquamaster]

A long necked dinosaur wouldn't have been truly snorkeling because he normally moves that much dead air whether breathing on land or in the water.

Birds are generally considered to be decendents of dinosaurs and they have zero dead air space in their lungs as they use a flow through system to move air through their lungs. For birds it makes snese as they have to generate large amounts of power for their weight and have to be highly efficient with strong hearts capable of moving a lot of well oxygenated blood.

But I have also thought that this same design would have been advantageous for a dinosaur like Diplodocus with a 46 ft long neck. They already required very strong hearts and muscular blood vessels to handle the very high blood pressures required to get blood up to their heads so why not more efficient lungs as well.

But that still does not resolve the pressure problems that would go hand in hand with snorkeling while walking on the bottom in 40 feet of water.

 

[dinoguy]

Birds are generally considered to be decendents of dinosaurs and they have zero dead air space in their lungs as they use a flow through system to move air through their lungs. For birds it makes snese as they have to generate large amounts of power for their weight and have to be highly efficient with strong hearts capable of moving a lot of well oxygenated blood.

But I have also thought that this same design would have been advantageous for a dinosaur like Diplodocus with a 46 ft long neck. They already required very strong hearts and muscular blood vessels to handle the very high blood pressures required to get blood up to their heads so why not more efficient lungs as well.

But that still does not resolve the pressure problems that would go hand in hand with snorkeling while walking on the bottom in 40 feet of water.

Well, in the unlikely event that any of them went underwater, most definitely diplodocus did not, his body is built so that his neck and head didn't rise much above horizontal. But the ones like Brachiosaurus had nearly vertical necks.

I could ask some dino experts about the 0 dead airspace idea. But the birds evolved from the theropods (meat eaters) not the sauropods so I'd be skeptical of similarities unless there was strong evidence. Theropods and thus birds have very different skeletal structure from sauropods.