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



On 4 Jul 2000 archosaur@usa.net wrote:

> > phylogenetic taxonomy. Mammalia are cynodontian Therapsida.
> 
> Yes, but the point is that noone goes around *saying* that. Not like how they
> do it with birds.  

Only because Dinosauria are more popular then Therapsida. I'm sure there
must be references in the literature somewhere about "non-mammalian
Therapsida" (analogous to "non-avian Dinosauria").
 
> > Ask this, then: What is the utility of a group that includes
> > _Sinornithosaurus_ with _Triceratops_, but not with _Archaeopteryx_? What
> > is so special about _Archaeopteryx_?
> 
> Actually I consider both _Sinornithosaurus_ and _Archaeopteryx_ to both
> qualify for the term "non-avian dinosaurs"  

_Archaeopteryx_ is included in the *definition* of Aves. It and Neornithes
are the only things *required* to be in Aves, by the definition.

> > > Yes, but no one is going around saying that humans are living
> > > therapsids
> > 
> > Actually, yes.
> 
> Who has said that? In what context was it said in?
> 
> Yes, humans are living therapsids, but who goes around saying that when one
> can simply call humans, humans? 

I'm just saying its perfectly permissible. Not many people going around
discussing humans as deuterostomes, either.

> Why? What is the quantifiable, repeatable, objective criterion or criteria
> for meriting "Class" status? How is Insecta equivalent to Aves? How is
> Coleoptera equivalent to Struthioniformes?
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 
> I don't know. Why has it suddenly not become OK to call birds avians,

It's still fine to call birds avians. Aves is a perfectly fine clade under
phylogenetic taxonomy.

> but it's still OK not to call birds reptiles?

Aves is part of Reptilia, under phylogenetic taxonomy.

> If we are going to dump our categories in favour of a purely cladistic
> view then why don't we just call ourselves derived archaea?

I think the name of that clade is "Biota".

In adapting paraphyletic taxa to PT, they are usually either limited to
the major clade of the paraphyletic group, or opened up to include
descendants. If there is already a good name for the paraphyletic group
plus its descendants, usually either the former route is taken (Anapsida)
or the name is simply discarded (Thecodontia).
 
> And since the nine thousands living avialans share more in common with
> each other than with "Mesozoic dinosaurs"

You're forgetting Mesozoic Neornithes. The proper term here should be
"non-neornithean dinosaurs".

> I don't understand why we have to remove the term Aves in favour of
> Dinosauria; which seems to be the case.

Nobody removed the term "Aves". How could there be "non-avian" without
there being "avian"?
 
> Why does calling a robin an avialan and a dinosaur Ok because it reflects
> ancestry, but calling it an avialan and a reptile depends on context?
> 
> Shouldn't they both depend on context?

They're both completely valid -- the question of which to state is a
matter of context.
 
> > Then why say that they merit their own "Class"?
> 
> Because in order to warrant that "status" you must have a large amount of
> differences from other groups

But does _Archaeopteryx_ have a large amount of differences from
_Sinornithosaurus_?

> and basic bird traits, I believe, are large different enough from
> basic dinosaur traits, to warrant that (though one is really just
> built off the other).

Yes, one is built off of the other. This is reflected by one including the
other.

> When I use the term class I am not giving it all the power that
> Linneas et al did. I just mean to use it as a easier way to define a
> group as diverse as birds have become. It's like on your cladograms.
> You have Avialae there; all I'm saying is that every creature after
> that should be called avian in the majority of cases.

Actually, they should be called "avialan". "Avian" refers to Aves, not
Avialae (they are slightly different clades).

> And *that* is what the crux of my argument is. The term "non-avian"
> *should* only be used in the appropriate context, but it is
> increasingly not being done that way. In more and more books,
> periodical, newstories & specials, the term is being used *almost* as
> a replacement for the term dinosaur. And that is what is bugging me so
> much.

I am in full agreement.
 
____________________________________________________________________________
T. Michael Keesey <tmk@dinosauricon.com> | AIM <Ric Blayze> | ICQ <77314901>
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