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"Dinosaurs are birds" - In defense of



At 10:03 PM 6/30/95, James Shields wrote:
>>>        But to correct something else you said:  there are no flying
>>>dinosaurs,
>>
>>Oh yeah, what about birds?

And Jerry D. Harris replied:
>        Yeah, yeah, yeah...the ol' "Cladistics Is Best" thing!  8-)  While
>I like the rigorous analytical techniques of cladistics, I don't always
>agree with the results.  Cladists, I've found, very often lose themselves
>looking at the trees, and forget that there's a forest there:  that is, the
>logic is often foregone for the sake of getting some results (even when the
>results don't make all the sense in the world!)

>        Believe me, I understand that, with cladistics, birds _are_
>dinosaurs (and thus flying dinosaurs), but in the same vein dinosaurs are
>just glorified lungfish (which, really, in turn, are merely glorified
>bacteria), but no one calls them that, and no one (not even any cladist of
>whom I'm aware!) thinks of them that way.  Why?  Dinosaurs have so many of
>their own specializations that it just doesn't make semantic sense to call
>them lungfish.  Similarly, I find that birds have enough of their own
>specializations that they warrant being considered their own "type" of
>organism.    Thus, I call birds "birds," and not" flying dinosaurs," the
>same way I  call dinosaurs "dinosaurs," and not "big terrestrial
>air-breathing fish."  8-)

>        Maybe I'm just old-fashioned (I do live in the past, after all!
>8-)  ), and am being too Linnean for my own good in a world rapidly being
>overrun with cladism, but until we start calling crocodilians and dinosaurs
>"thecodonts," and calling mammals "pelycosaurs," I'm a-stayin'.  We
>invented the term bird for good reason; I vote we use it!

With respect to you (and I have a lot), I think you are misunderstanding
the position that cladists and "birds are dinosaurs" proponents take.  In
the first place, "lung-fish" and "pelycosaurs" are NOT clades; "descendants
of lung-fish" and "descendants of pelycosaurs" ARE clades.  In the second
place, in our desire to taxonomically place feathered flyers within the
Dinosauria, we are NOT seeking to abolish the word "bird" from the language
and force people to say things like "Did you see that flock of dinosaurs fly
by?"  We merely want to create a classification scheme that emphasizes the
fact that birds are theropod-descendants that became specialized for flight. 
As John McLoughlin says in his book _Archosauria_:

"...In all, we are forced to conclude that birds are no more or less than
dinosaurs, and that their classification outside class Archosauria [or
Dinosauria] makes no more sense than would classifying bats outside class
Mammalia because they, too, can fly!"

Of course, if you believe that birds did NOT evolve from dinosaurs but 
from Pseudosuchians or someone else, that's an archosaur of a different
color (grin), but assuming birds DID evolve from theropods, I see no reason
to segregate birds from dinosaurs (taxonomically, if not in general everyday
perception) simply because they fly and are endothermic beyond all doubt.

                                   -- Dave