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Re: Air sacs in extant non-avian reptiles?



At 09:33 AM 31/07/00 -0400, ELurio@aol.com wrote:
Have you actually compared a pidgen with a gecko? The differences are
enormous!!!! The small group of physiologists  n fact accounts for
practically all of them working today, not to mention every single
orthinologists. Birds are as much reptiles as they are fish.

Well, speaking as an ornithologist I agree with the last statement! Birds are both reptiles and fish, of course, just as we are both synapsids and fish.


The question of whether or not to recognize Aves as a class strikes me, though, as (a) moot and (b) certainly not to be decided on the basis of similarity. For example, compare (say) a lungfish and a bluefin tuna - as different, I would think, as geckos and pigeons (if not more so) and yet both members of the traditional "class" Osteichthyes.

The point is that in a phylogenetic sense, even if we only consider living animals, a crocodile is more closely related to a pigeon than to a gecko -whatever their level of similarity. Therefore if crocodiles are reptiles along with geckos, birds must be too.

However, ornithologists do generally support class status for Aves - but not, I think, because they think thee is any great inherent truth to the notion. It is a a matter of convenience, because if you are going to reduce Aves to (say) ordinal level you must reduce the ranks below it and this becomes confusing, as most of us are used to thinking of modern birds as comprising twenty or thirty orders, not one.

Of course any heirarchical system like Linnaeus's must be arbitrary when imposed on a continuous evolutionary stream. For that reason I rather like the idea of doing away with the heirarchies altogether. Birds certainly consist of a monophyletic taxon, and whether you call it Aves or something else, or call it a Class, an Order or nothing at all, that fact does not change. Reptiles including birds do too - but reptiles not including birds do not. Neither do bony fishes if tetrapods are omitted. As long as we recognize this, and we all know what we are talking about in any given context, I do not think the rest matters, including whether birds are called a class, or whether geckos are called non-avian reptiles.
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Ronald I. Orenstein Phone: (905) 820-7886
International Wildlife Coalition Fax/Modem: (905) 569-0116
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