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Re: Back to the dino-bird thang



At 02:31 PM 12/3/96 -0500, Rob Meyerson wrote:

>I think the point Norm was trying to make was that if you put an
>undoctored pidgeon next to an undoctored Archy, a child will say they
>are different animals.  Similarly, if you put a "head-butting
>therapsid" next to _Dimetrodon_, the child will say they are different
>animals.

   The comparison was not whether the child could tell they are different
*animals*, but that they could tell they were different "types" of animals.
The picture I had in mind when writing my second example doesn't fit with
what came out in words, but I do think George's little example was too
extreme (does a child KNOW what "deep hemal arches" or a "pygostyle" are?).
I'm just going to drop that bit of it.

>The point being that there has been a great deal of
>evolution between the two forms, so they can be seen as belonging to
>different groups.  Granted, by doctoring the forms we can see the
>phylogeny of the group, but there is a point where one form becomes so
>derived, that it can be seen as belonging to a different group
>altogether.

   Yes, another group of THEROPOD.  _Triceratops_ and _Velociraptor_ have
approx. 155 My separating them, about the same amount of time between
_Archaeopteryx_ and _Corvus_.  To use a recent phrase, no child would
mistake a _Triceratops_ for a _Velociraptor_.  Does this mean the trike (or
the 'raptor) is not a dinosaur?

>To anticipate the flames, while I acknowledge that birds evolved from
>dinosaurs, I question whether they should be classed within Dinosauria
>(the Linnean taxonomist in me).  I also acknowledge the fact that the
>line between the two groups (as it is with all fossil groups), is
>rather hazy and fuzzy, as Archy and Sinosauropteryx demonstrate.
>However, in the ~150ma since the evolution of the true flying
>dinosaurs, there has been so much refinement that today we are far
>beyond that hazy line.  So, IMNSHO, birds are separate from dinosaurs.

   It confuses the heck out of me where one makes the dileneation between
where an animal is one thing then becomes something else.  Even after
millions of years of evolution, humans are still primates, they're still
mammals, they're still amniotes, they're still tetrapods, they're still
vertebrates, they're still chordates.  Birds, too, are still amniotes, still
tetrapods, still vertebrates and still chordates.  It doesn't make any sense
to me to cut something out in the middle, especially when the modern form is
not 100% completely different in every way, shape or form from the ancient one.

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