RE: Biomechanics

["Matthew Bonnan" <mbonnan@hotmail.com>]

Hi all:

Thanks to Toby, Ken, Michael, and others for keeping this thread alive and 
interesting.

I think the whole dead space issue is where you have arguments about 
sauropods having a bird lung sac system.  Because birds have a one-way 
airflow system, they can "afford" to have longer necks with greater dead 
space.  Interestingly, according to Knut Schmidt-Nielsen in his excellent 
little book Size, if one were to calculate the trachael volume and dead 
space in the neck of a trumpeter swan, one would come up with a result that 
the animal could not breathe!  Don't have the numbers handy, but the gist 
was that birds get around the dead space issue by having a one-way airflow 
system and extremely efficient oxygen extraction.

Yes, as Toby White points out, extrapolating from an extant vertebrate is 
fraught with problems.  Such extrapolation does provide some interesting 
insights, however, and can be used as ballpark yardstick for judging the 
realism of certain models.

The problem with sauropods is that they don't work too nicely with modern 
analogs or within Witmer's phylogenetic bracket hypothesis.  That is, 
because there is no direct link to sauropods in a living archosaur today, we 
are forced to extract what info we can from gators and birds, neither of 
which is an ideal model for sauropods for obvious reasons.  With the large 
mammals there are more difficulties.

With some of my research, I can circumvent a few of these difficulties by 
looking at the articulations of the real bones, perhaps make some models 
based on these observations and measurements, and go from there.  This is 
not much of an option for understanding breathing capacity in sauropods, 
which is why most of the things you will read or see in this regard are 
extrapolations from extant archosaurs and mammals.  Hengst I know is 
developing more accurate models and ideas on dinosaur breathing as we speak. 
 If he is reading this list, perhaps he could add his two cents?

Matt Bonnan

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