High Oxygen

["Richard Hengst" <rhengst@163.245.1.5>]

A recent posting about elevated oxygen during the mesozoic vs the large size of 
dinosaurs probably refers to a mix of papers.  There have been reports of 
atmospheric gases released from amber bubbles which has generated a lot of 
controversy.  However, oxygen appears to constitute over 30% of the total in 
Cretaceous and very limited Jurassic samplings.  This percentage drops as 
samples get more recent with present (21%) value being reached in tertiary 
samplings. A point is reached in the amber formation process where amber ain't 
amber and vapors will gunk up the analysis equipment.

  I got into this while trying to analyze oxygen delivery in dinosaurs.  My own 
work with living animals tends to confirm the likelihood of elevated mesozoic 
oxygen.  It does not prove it, but high oxygen gives a better explanation of 
some complex physiological phenomena than any alternatives I have considered 
(and tested) so far.  This past summer, Carl Gans and others published a 
theoretical analysis of the consequences of elevated oxygen in the Permian.  
>From time to time, I have seen some suggestions (possibly the "theory" 
>mentioned
in the earlier posting) that elevated oxygen as a cause of dinosaur size 
increase. I suspect that Farlow is correct in saying the cause is more likely to
be ecological (food, energetics, and the like).  Elevated O2 as the primary 
reason leading to, and permiting, size INCREASE does not fit well with what 
would be expected from this cause alone.  In fact, elevated oxygen probably 
benefits small animals more than large ones if the literature is correct.

Anyway, it is an interesting question and certainly unresolved at this point.  I
would point out that much of the arguments regarding an elevated oxygen 
atmosphere do not so much argue about its occurance, as they do about what 
mechanism could explain the O2.  

Cheers,

Rich Hengst
Mesozoic Physiologist