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Re: [Re: [Re: Non-serpentine lacertids (was RE:WHAT'S GOING ON?)]]



chris brochu <cbrochu@fmnh.org> wrote:

> I think I can sum up the differences between my stance (and the stance >
held by many of my colleagues, some of whom are on this list) and the > >
stance held by those taking a contrary view, with an exposition on this >
statement, made by Jura:
> 
> 
> >
> >1) If it meets the basic criteria to be a dinosaur, it should be called >
>a dinosaur
> >
> >2) If it meets the basic criteria to be a bird, it should be called a >
>bird.
> >
> >3) If it meets the basic criteria to become a dinosaur and meets a > >large
part of the criteria to be a bird then call it a non-avian ----
> >
> >Now 2 of course will mesh with 1 for obvious reasons. But I think 2    >
>should take priority if it meets the younger taxa's criteria. Kinda > >like
the reverse of the ICZN double names rule. It allows for > >categorizations
without the worry
> >of accidentally kicking something out.
> >
> >As for what the basic criteria for each group is; well that is > >something
that needs looking into.
> >
> >++++++++++++++++++++++++++++++++++++++++
> >
> 
> 
> There is a difference, I think, between my concept of "taxon" and > Jura's.
(If I misinterpret, I apologize.)  To me, a taxon is > > philosophically an
individual - in other words, a coherent entity united > for historical
reasons.  The historical reason a taxon exists is common > ancestry.  To Jura,
a taxon appears to be a philosophical class - a     > simple assemblage of
objects that share some sort of fixed defining >   > property.  (I am using
the word "class" here as a philosophical term and > not as a Linnean rank.)
> 
> I am an individual.  I have a historical reason for being (conception and
birth).  I could change any and all physical or cultural characteristics
apparent to me - radical haircut, new piercings, convert to some new religion,
start speaking a different language, different clothes, whatever - but I would
still be the same individual.  The historical reasons for my existence do not
change.
> 
> "Paleontologist," though, is a class - one fulfills certain criteria to
> become one (training, experience, research, and so on).  One can become a
paleontologist during a lifetime, and even stop being one - all you have to do
is adopt or drop the defining criteria, as circumstances demand.  But you
never stop being what you are as an individual.
> 
> 
> In the Linnean system as applied first in the 18th century, taxa were
> classes.  And there was no reason to make them anything else - animals and
> plants were created as fixed entities as discussed in Genesis, and there
> was no historical connection between any of them.  The categories Linneaus
> and his contemporaries used were artificial, and operated on the assumption
> that organisms were themselves fixed and immutable.  But we humans are
> natural pattern recognizers, so that the natural hierarchy generated by
> evolution was staring us in the face, and systematists couldn't help but
> reconstruct it, even if evolution was not the driving force behind it.  So
> when Darwin came around, the natural hierarchy implicit in taxonomy became
> evidence for evolution and was retrointerpreted as the product of descent
> with modification.  This is why taxonomy still operates typologically - an
> old system was reinterpreted, when a new system was actually called for.
> 
> If we regard taxa as individuals (which is more in keeping with
> evolutionary thinking), the "basic criteria" for each group is descent from
> a member.  Birds are members of a monophyletic Dinosauria because they
> fulfill that basic criterion in being descended from derived theropods.  In
> this case, the "criterion" is historical and not material, as it would be
> if Dinosauria were a class.
> 
> But the minute we start pulling supraspecific groups away from their
> ancestors, we cease looking at them as individuals; we are now applying
> some sort of typological criterion for class membership.  Birds may be
> descended from dinosaurs, but they have some key feature (feathers, ability
> to chirp, whatever) that we regard as essentially "nondinosaurian."
> Dinosauria is thus no longer an individual, because its membership is
> limited by fixed nonhistorical criteria.  (This is also why there is a
> difference between species and supraspecific taxa in this regard.  There is
> a historical, nontypological basis for drawing an upper bound on a species
> - the cladogenetic event itself.  The same is not true for supraspecific
> taxa, unless we want to regard each and every internode on a cladogram as a
> valid supraspecific taxon completely redundant with its sole component
> species.  And yes, this does regard anagenesis as a process within species
> and not one generating new species - another discussion for another time.)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Well I'd say we're getting closer to common ground at least.

I am not trying to bring back the Linnean system, but I am trying to splice it
with the cladistic one. Or at least, I think I am.

Sorry for being confusing here, but the main thrust of my argument in the
first place was in calling all modern birds, or anything that falls under
Avialae, dinosaurs in a context that doesn't warrant it. That, along with
calling all dinosaurs that came and/or branched before Avialae, "non-avian
dinosaurs" in an out of context situation. 

So I did propose using the Linnean class/order system when it comes to what
name the animals should be called. Since in order to become a class, there
must be a very large amount of differences between one group and all the
others, this seemed like a worthy criteria to base it off of. After all in
order to reach such a divergence there has to be a fair amount of diversity
involved. With most creatures avialae accomplishes this and with the exception
of a select few theropods, it works here too.

Now I am *not* suggesting that we pull Aves out of Dinosauria and place it
somewhere else. I am merely suggesting that we call all the creatures that
descended from and branched off of Aves, avian or at least birds.

It's really nothing more than using the same logic that decides when you call
a bunch of derived ornithodirans, dinosaurs.

For most creatures in taxonomy (cladistic or not) these rules seem to apply.
It's just that in dinosaurs the rules seem to change and now instead of
avialans and dinosaurs we get dinosaurs and non-avian dinosaurs. Now in the
proper context I can understand this use (just like n the proper context,
calling dinosaurs derived ornithodirans makes sense), but for the most part it
is not proper context, it's becoming common usage, almost like a replacement
for the old names. To me it appears that due to the influx of dino-bird
fossils, the gaps between dinosauria and aves seem to have been bridged enough
that aves has been thrown out. Does this mean that when/if there are enough
fossils to bridge
the gaps between dinosauria and the other ornithodirans, that we will forgoe
the common usage of dinosaur in favour of ornithodira?

The haphazard use of dinosaur and "non-avian dinosaur" is what was annoying
me. Nothing about bringing back the Linnean revolution.

Jura

Jurassosaurus's Reptipage: A page devoted to the study of the reptilia:

http://reptilis.webjump.com

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