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Re: Cladistics and extinction
Jonathan Wagner wrote:
> In the case you were discussing, your tendancy to think
> non-phylogenetically has you emphasizing the wrong point. You want to know
> why the non-avain dinosaurs went extinct. You seem to think it is
> unreasonable that these animals, which obviously had some flaw that led to
> their extinction, should not be their own seperate group.
Regardless of if I'm thinking "flaw" or "bad luck", there there
must have been reasons. My point is that paraphyletic concepts are
useful in discussions of evolution, even if you don't want to include
them in the formal taxonomy. If you are trying to figure out why one
group went extinct and another closely related group survived, or why
one group had a big adaptive radiation toward particular kinds of
niches while a closely related group did not, morphological differences
(indicators of lifestyle) are probably at least as important as common
Homologies mat be useful in determining common descent, but
morphology dictates lifestyle (or rather vice-versa), and THESE are the
clues to an organisms sucess or failure (at a certain time under certain
For another example, how could you discuss the evolution of
endothermy in birds and mammals without the concept of "reptile?" What
if the LOSS of a certain trait ultimately results in a groups demise?
Lets pretend for a moment that birds and mammals evolved endothermy to
exploit a small niche which then dried up, causing them to go extinct.
What if the loss of more primitve reptilian characteristics ultimately
caused the EXTINCTION of birds and mammals? Wouldn't the concept of
"reptile" be useful then? Not amniote- REPTILE.
> If one looks for "fatal flaws" in each extinct group, one will never
> get as far as fast as if one looks at derived characters in the
> clades that survived.
You are assuming that it is always the DERIVED characters that will
always be the key to survival. If the underived condition ultimately
turns out to be more advantageous, then the surviving group would be