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Re: Archaeopteryx (rant)



Dinogeorge@aol.com wrote:

Just because a system has been used incorrectly doesn't invalidate the system
itself. We can simply learn how to use it correctly. For example, one class
(Reptilia) can give rise to another (Aves); why not? Descent doesn't mean you
>must< include the descendant group within the ancestral group. And as far as
rank goes, it's purely arbitrary, so why not simply assign the groups their
ranks forevermore and be done with it?

What a ghastly idea!

Look, if you want to keep the Linnaean system around for the purpose of classification - Linnaean stamp-collecting, if you will - then go ahead. But please - PLEASE! - don't incorporate it into any evolutionary or phylogenetic discussions. Statements like "one class (Reptilia) can give rise to another (Aves)" are not helpful in communicating ideas about evolution. The term "class" is in itself a statement that a certain group has attained a level of organization superior to that of its ancestral "class". These ranks (and what they imply of the natural process) have no place in evolutionary discourse.

On that note, if you wish to retain unnatural (paraphyletic or polyphyletic) groups like Thecodontia, Condylarthra or Protozoa, simply because they make it easier to classify difficult-to-handle "primitive" taxa, then knock yourself out. All the weird Triassic archosaurs (those that are obviously not dinosaurs, pterosaurs and crocodiles) can be dumped in the Thecodontia, without having to expend time and energy figure out who might be related to who. But these wastebasket groups should be kept separate from any scientific discussion of evolution. To say, "birds evolved from thecodonts" reveals nothing - except for the fact that the author has no idea what the closest relative of birds might be.



Tim

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