Re: Unidirectional gator breathing in Science

[don ohmes <d_ohmes@yahoo.com>]

--- On Thu, 1/14/10, gsp1954@aol.com <gsp1954@aol.com> wrote:

> Jeez, an irrelevant to the idea paper in Science and deep
> snorkeling 
> sauropod drivel. 

Actually, I stated that due to incorrect and tacit assumptions about sauropod 
respiration, the _falsification_ of the "snorkel theory" may be falsifiable. I 
would indeed consider standing at 2 atm (10m depth) and breathing surface to be 
unlikely, but then I consider that a sauropod holding its' neck straight up to 
be a little much as well.

> Because sauropods were so pneumatic they would have
> chronically floated, 
> not sunk to the bottom like nonpneumatic, heavy boned
> aquatic animals.

Perhaps, if Henderson is correct, and did not underestimate the density of the 
lower limbs. However, in previous discussion(s) on the list, claims were made 
that a sauropod merely up to its' shoulders in mud (or watery mud) would have 
difficulty breathing due to pressure. I consider those claims doubtful. 
Further, as mud resists movements of the legs, the 'tipsy punter' scenario 
would not apply in swampy conditions, anyway. 

> None of the examples cited breaths with the body under high
> water pressure 
> (humans can breath through a tube a couple of feet under,

Only for a short period of time; 2' is very difficult, perhaps dangerous, for 
most humans. I have seen claims of 6', but am skeptical. 

> surface swimming 
> snorkeling elephants breath with the lungs a few feet below
> the surface). 

Given that they must move that water w/ their diaphragms, while drawing air 
through the trunk, that is very impressive performance from the elephants, 
don't you think? Given the larger amount of power sauropods possessed, any 
inherent advantage to their respiratory system might well have allowed them to 
breath under more than 1.2 atm abdominal pressure (2m depth). 

As an aside, another point frequently missed in consideration of possible 
sauropod lifestyles is the fact that 'dive time' is proportional to bodysize. 
Given their 'airiness', sauropods could likely have held their breath an 
impressive length of time even in the absence of specific adaptations.

> Water pressure more a couple of meters would have prevented
> inhalation 
> regardless of respiratory design. 

I will accept that statement (or guess?) when I see some data on the abilities 
of birds. As none currently exists (apparently), it might be a while, but will 
come someday, I hope. 

I note that a person can exert _considerably_ more than a mere 1.2 atm pressure 
when holding a chicken or duck. While thoracic compression is used historically 
to "euthanize" birds, it is not recommended on larger birds due to difficulty 
and slowness. I also note that none of the birds that I held when I was growing 
up suffocated, even though I would never have held a dog that tight (and would 
have been bitten immediately had I tried).