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Cladistic taxonomy (was Dietary factors)




Mark,
I'm afraid that there is a stalemate between cladists (who say birds ARE dinosaurs) and the rest of us (who say birds are dinosaur descendants). When you remove a group of descendants (e.g. birds) from its ancestral group (e.g. reptiles, and dinosaurs in particular), the removed group is called an exgroup, and the rest of the ancestral group is labelled paraphyletic. Most cladists have been taught to regard "formal" paraphyletic groups as unnatural, to be discarded with the truly unnatural (polyphyletic) groups.
So if you remove an exgroup (like birds), as many non-cladist scientists continue to do, you are breaking a big cladistic rule (Thou shall not commit "formal" paraphyly). So when speaking with cladists, we are expected to use qualifiers (like "non-maniraptoran") to refer to paraphyletic groups: non-maniraptoran dinosaurs. Needless to say, most lay people and non-cladist biologists don't like having such changes shoved down their throats, the stalemate continues, and confusion and ineffective communication is often the result. But cladistic classification is popular among dinosaurologists, so you must learn clado-speak on a list like this if you want to avoid miscommunication. The Catch-22 is that they keep adding more and more formal clades, which we must learn in order to apply their qualifiers, and worse yet, even the cladists don't agree among themselves. Cladists remind me of lawyers.
Thus even some dinosaurologists are very critical of clado-speak. I would recommend Peter Dodson's 2000 paper (American Zoologist, 40:504-512) who says:
"For example, the word dinosaur was not previously problematic--it was universally understood. Within cladistics it has now been redefined to include birds (holophyly), and then a new and cumbersome phrase, non-avian dinosaur, has been substituted. This is not progress; this is semantic obfuscation not enlightened communication."
As I have noted on this list before, the biggest problem is that cladists have unnecessarily appropriated the names of paraphyletic taxa and changed the definitions to ensure holophyly. Dinosauria is clearly one example that is the source of irritation to non-cladists, as are Reptilia, Amphibia, Osteichthyes, and so on. Mike Keesey has recognized this problem and recommended that some of these terms not be formally defined under PhyloCode, and use alternative cladistic terminology, such as Ostei instead of Osteichthyes, and Sauropsida instead of Reptilia. I support such suggestions, but I'm not sure the majority of PhyloCoders will be so accomodating (and will insist that non-cladists just need to learn the "correct" way to classify). If a hard line approach is taken, the reaction to PhyloCode is bound to be even more intensely negative when it is implemented. I wish Mike luck in trying to head off some of these problems.
Put simply, the main difference between purely cladistic classification and eclectic classification is whether or not formal paraphyletic taxa should be allowed. Cladists say no. Everyone else says yes, because the price is too high and we see no end in sight to the upheaval, confusion, and bickering. The cladists want extreme precision of nomenclature, no matter what the cost. And their biggest mistake was appropriating names like Dinosauria instead of giving new names to the precisely defined clades. Personally I think a hybrid cladisto-eclectic system is inevitable, but neither traditional eclecticists nor traditional cladists will accept such an inevitability as long as they each think their side is going to win the "war" and the other side will have to submit. In the meantime, we will all continue to lose in such an obvious lose-lose situation. C'est la vie, but I think it is an incredible waste of time and energy.
------Ken Kinman
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MarkEShelly wrote:
I understand the reason some of us say birds are dinosaurs, meaning Aves belongs to the clade dinosauria, but with the loss of teeth, tail, and hand
claws (relying totally on flight at some point) in birds is where, in my mind, they quit being (classic) dinosaurs and birds, but just birds.
I wish we had a word to seperate the bulk of dinosaurs from the feathered, toothless, tailess, handclaw-less dinosaurs, similar to what the
semi-scientific term dinosaur used to mean! Either that or say dinosauria or dinosaur clade when we want to include birds and dinosaur when we don't. I do not understand why redefining dinosauria means the word dinosaur must also be redefined. (My 35 books with the term dinosaur and even this mailing list all imply (birds not included). If man evolved from bacteria, I would not like to hear the statement (men are bacteria -or fish for that matter) although a similar form (men are scum) is understandable in some cases. The reason we apply scientific names is to seperate and identify items for easy understanding. Changing the meaning of common well known words does not.
Mammal was origionally defined to include bats. As bats and flightless mammals both exist today, it is a great combination. The term dinosaur has the element of extinction to it, meant to classify an extinct group with a common trait.


Mark Shelly
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