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>It just occurred to me why Stefan and I seem to be talking past one
>another. By saying "birds are dinosaurs" I'm making a statement
>about their phylogenetic ancestry whereas I think Stefan is
>objecting to birds being classified as dinosaurs. I see a distinction
>between these two statements. In fact, I don't insist by any means
>that birds be classified as dinosaurs (though I must admit that if I were
>making up a classification I would probably do so). Still I can understand
>and, in many cases, have sympathy for the recognition of non-monophyletic
>groups in certain instances. It is possible to be a cladist without
>advocating the overthrow of the entire nomenclatural system. Nevertheless,
>I think my argument about birds belonging to the dinosaur lineage and that
>lineage having survived to this day (a phylogenetic argument) still stands.
>At least until Stefan's next posting.
>
>Norm MacLeod
Yes, of course! This is the very point I tried to make, and I have little
to disagree with your last statement: I have never argued that birds don't
belong to the dinosaur lineage. What prompted my objection was your earlier
statement that the talk about dinosaurs being extinct is a 'lapse that gets
us into trouble' because birds are still around. This to me is a lapse that
echoes the all-to-commonly heard cladistic credo that only monophyletic
groups in cladograms are real, that any reference to paraphyletic groups is
scientifically unsound ('they don't exist'), and that extinctions that
don't involve all descendants are 'pseudoextinctions' that we shouldn't
really be concerned with.
Roy Plotnick just made a similar point:
>Sure, birds are probably dinosaurs and thus dinosaurs did not go extinct at
>the end of the Mesozoic. Does this mean that nothing important happened?
>By that logic, we could wipe out all humanity except for the population of
>Hawaii and then argue that nothing happened, because H. sapiens did not
>go extinct!
>My bias is that the critical question is not which groups did or did not go
>exinct, but was there a major disruption of ecological systems at the K-T or
>other boundary. The evidence for this disruption could be taxonomic
>extinction,
>but it could also be a major reduction in numbers, etc.
I wholly agree with Roy (except perhaps with his first sentence).
Don't get me wrong: Some of my best friends are cladists, and I wouldn't
mind at all my daughter marrying one. I think that parsimony analysis is an
unsurpassed, though not unsurpassable, method of sorting out phylogenetic
relationships. What I (and perhaps also you?) object to is the central
cladistic principle that phylogenetic branching sequences are the only
acceptable basis for a biological classification and that this leads to
groups that are 'real', as opposed to the hopelessly arbitrary groups of
non-cladistic classification, which are just constructs of the mind and
should be abandoned.
Stefan Bengtson _/ _/ _/_/_/ _/ _/
Department of Palaeozoology _/_/ _/ _/ _/ _/_/ _/_/
Swedish Museum of Natural History _/ _/ _/ _/ _/ _/ _/ _/ _/
Box 50007 _/ _/ _/ _/_/_/ _/ _/ _/
S-104 05 Stockholm _/ _/_/ _/ _/ _/ _/
Sweden _/ _/ _/ _/ _/ _/
tel. +46-8 666 42 20
+46-18 54 99 06 (home)
fax +46-8 666 41 84
e-mail Stefan.Bengtson@nrm.se
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