Re: Class-less dinosaurs

[chartiem@ERE.UMontreal.CA (Chartier Michel)]

> 
>   So, why does the archaic (yes, archaic) Class AVES
> still continue to be used in systematics?  It certainly isn't the
> state of science that is maintaining this psuedo-class!  Is it
> politics?  Is it a reflection of the rift between dinosaur 
> paleontologists and ornithologists?  Who will eventually decide
> whether AVES eventually gets thrown in the trash heap of history?
> ICZN is not responsible for such matters.
>  I can't believe that resistence from such people as Larry Martin
> is holding up the final abandonment of the Class AVES.
> It is time that all sources, be they science journals, children's
> books, magazines, bird-watchers guids and Peterson's Guide ALL
> start to use the proper systematics for birdies.
>   Birds are in the Class DINOSAURIA, not AVES.  AVES is dead.  Someone
> get a shovel and let's all go out and bury it.
>  If the ornithologists on this listserve want AVES retained, why not
> knock it's rank down to something below maniraptoran-level (in other words,
> it is going to be REAL low...below the subclass THEROPODA).  But at least
> it will be the first time bird's true systematic rank is accurate in over
> 100 years.  John Ostrom, strangely, believes that AVES should be
> retained.  I can't figure out why he, of all people, would want this.
>  
> 
Philip:

        I don't think that the desire to retain the class Aves has much
to do with what you think is their proper phylogeny (i.e. be they 
descended from dinosaurs, crocodiles or whatever) as much as it has to do
with what kind of systematist you are, i.e. pheneticist (numerical
taxonomist), evolutionary systematist (evolutionary taxonomist), or
cladist (phylogenetic systematist).
        If you're a strict cladist (which I am not), you will want
to include birds with theropod dinosaurs, just like you will want to
include humans and pongids (chimp and gorilla) into a single taxon,
namely hominids. But to do this is to take away what is "special"
about the group concerned. It is clearly evident that humans are much
more derived than either chimps or gorillas are, so why not recognize
their unicity (is that a proper word?) and retain them in hominids, to
the exclusion of chimps and gorillas? 
        You will probably think that I favor an evolutionary systematic
approach in classification, but that is not exactly the case. But I
do think that some aspects of this approach are reasonable, just like
I do think that some aspects of cladistics are. Now an evolutionary
systematist would emphasize the weighting of autapomorphies and
also would consider the importance of major adaptive shifts in his
attempts at classifying. Isn't the evolution of active flight a major
adaptive shift (as compared to terrestriality)? Isn't the evolution
of bipedalism, large brain, articulated speech and confection of
complex tools a major adaptive shift as compared to the quadrupedalism
and social and anatomical aspects of traditional pongids? I know I'm
being simplistic here, but I hope you get my point.
        You don't have to remind me that, yes, evolutionary systematics
are very subjective in nature. But to believe that cladism is totally
objective is being naive. I think that cladists maybe put a bit too
much emphasis on synapomorphies (shared derived characters) and not
enough on autapomorphies (uniquely derived characters), if not at all.
I also think that this rejection of paraphyletic taxa is unreasonable.
Maybe John Ostrom wants to retain Aves as a class because he feels
that they are sufficiently derived, as compared to the other archosaurs,
to warrant their classification as such. (Maybe someone that knows
Dr. Ostrom would care to comment on this.) Now, to use the words (or
ideas) of one of my good friends (he'll know when he reads this),
why be a strict cladist, or a strict evolutionary systematist? Why not
take what's good of both methods instead?
        One last thing. Dinosaurs as a class sounds great (and it also
makes common sense (a la evolutionary systematics style) since the
group as a whole is as diverse in its adaptations and morphology as are
the mammals). But what about archosaurs as a group? If you take out
dinosaurs, what happens to archosaurs, Phil?
        Maybe what I just wrote makes no sense at all, maybe it does.
Anyway, I would like (and I'm sure Philip also, or else he wouldn't
have brought it up) to know how other people feel about this issue,
the professional and the avocational paleontologists alike. (We may
have to wait on Monday for some, but that's no problem.)

Michel Chartier
Departement d'anthropologie
Universite de Montreal

P.S. I really did not want to start a big debate about cladistics,
classification and the like (and I hope it doesn't develop as such),
but I just could not ignore Philip's post.