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Re: Polytomy question

2005/10/25, T. Michael Keesey <keesey@gmail.com>:
> On 10/25/05, Manuel Parrado <meparrado@yahoo.com> wrote:
> >
> > e.g., the coelacanth.  I assume there are many others
> > that have achieved this level of morphological
> > stability (perhaps turtles?).  I would assume that
> I think that's because there aren't very many (if any) species that
> are truly that conservative. Coelacanths may not have changed as much
> as we have since our last common ancestor, but they have changed
> (notably gaining some adaptations for living in deep seas). And look
> at an alligator snapping turtle, a Galapagos tortoise, a leatherback
> sea turtle, and a diamondback terrapin and tell me that they all look
> alike.

For me this "stability" effect is just because the way that we name
things. If they are all the same or look alike, they are of *same*
order, family or genus, if they are just more diverse, we split them
in several orders, suborders, families and genus.

After that we scratch the top of our head and say: Hey, why are the
sharks so conservative in morphology? Why are the Rodentia so similar
in shape? If we'd called shark what we call Chondrichthyes, if we'd
called Rodentia what we call Mammalia we would appreciated the sharks
and rodents morphological diversity.


Roberto Takata