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Re: Function Talks at Ostrom Symposium

George writes:

>>Birds therefore must have developed their present lung system >alongside<
their original diaphragmatic lung system, at first simply to increase
ventilatory efficiency as they became better fliers. Gradually the original
system was lost (or became modified into, say, part or all of their air sac
system--to figure out the details requires examination of extant-bird
entrails) as the newer system took over more of the respiratory function. This
didn't happen overnight, and I look forward to the discovery of possible
flightless, very birdlike theropods with well-preserved innards showing signs
of >both< kinds of respiratory systems--say in Brazil.

This is indeed what the work of David Martill (Southampton University) has
shown me recently and that he will be publishing soon.We are very close to
have full, hard evidence of avian sacs in theropod dinosaurs... and not
only hollow bones. I have seen them and even if they are are not
*completely* clear (to my eyes), they are better evidence than mere traces
or organs that nobody can be sure of what they are.

> augwhite@neosoft.com writes:
><< Ruben's point is that you
> *cannot* go from hepatic pump to avian without a step that is so debilitating
> as to be nonviable. >>
>If this is indeed what Ruben is saying, I think it's wrong. But I wasn't at
>the conference, so this may all just be hearsay.

No, it's not hearsay. The argument that birds and dinosaurs are not
directly related (just distantly and a 'thecodontian' level) is what he
have been defending from the very beginning. Everyone of his recent talks
have been directed to try to demonstrate this, making him closest to
Feduccia's arguments.

Luis Rey

Visit my website on http://www.ndirect.co.uk/~luisrey