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Re: Back to the dino-bird thang



Jeff Poling writes;

> If you show a child an ancient bird like _Archaeopteryx_, especially
> if it's standing next to "Sinosauropteryx", will he be able to tell
> the difference?  If you take a modern bird and break off the keeled
> sternum, and stand it next to a similar sized, beaked, non-avian
> dinosaur with its tail snapped off, will he be able to tell the
> difference?

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 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.

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.

Do people who work on therapsids demand that all mammals be called
therapsids?

Rob Meyerson
Orphan Vertebrate Paleontologist

***

"Next time you have a revelation, could you find a way that isn't so
 uncomfortable?"
        -M.C.