posted 02-05-2002 09:06 PM            

But I have an out – I told you I didn’t do any research LOL! And I still haven’t, although I promise I will look up Brother Hengst’s work, because I’ve always been interested in paleontology.

I know that, even in the past ten years, we’ve learned a whole lot more about saurischian physiology than we ever knew, even finding what we’re pretty sure are fossilized hearts(!) which seem to show three chambers, just like birds. If this is valid (and I don’t know whether it is or not), and assuming the same sort of anatomical structure as birds, then dinosaurs ought to be about as efficient respirators as any other critters, all things being equal.

But of course, all things aren’t equal. A critter that’s twice as tall as another weighs four or six times as much, and the ratio of volume to surface area is much greater. Given a really biggie like some of the sauropods, I can see how they’d have to breathe like mad just to keep the blood oxygenating. And if you have a big critter like a sauropod that’s right on the margin of success/failure, then just the smallest drop of ambient oxygen percentage could kill ‘em off.

What really surprises me, though, is that the oxygen level goes up and down and up and down so dramatically. I made an Excel graph (which I don’t know how to upload) of percentage against time, and the levels seem almost random. It’s obvious, given what you say, that there are a bunch of causative factors (that I don’t have a clue about) which result in some very significant changes in levels.

Even more surprising is the relatively small change on either side of the K-T layer, which coincided with the death of the dinosaurs. I mean, over an 800,000-year period which saw the end of the dinosaurs, there was only a two percent drop in the O2 level. Yet maybe that two-percent drop was the straw that broke the camel’s back – at least for the dinosaurs.

This whole thing juse seems to point out that we don’t know diddly about the atmospheric dynamics, and that any change to our atmosphere could be really serious.

Great post, Amber. Now I have a bunch of reading to do.

Regards,