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Re: Fixing dinosaurian carnivour question



First off, to correct a misconception:  my comment was not directed at the
poster who asked about what was the smallest carnivorous dinosaur.  My
comment was in response to the insulting reply by the individual below, who
referred to various posters discussing birds as being "paleo-politically
correct".

Folks, this is 1999.  Science marches on.  Like it or not, the dinosaurian
nature of birds is by huge leaps and bounds the best hypothesis in town
these days: to ignore the dinosaurian nature of birds is to ignore a major,
well-supported scientific discovery.

To have answered the original posters question with "_Compsognathus_" or
"_Scipionyx_" or such without qualification would have been inaccurate.  By
the same token, if someone asked the question "What is the country with the
largest population?" and we answered "The U.S.", this would have been
inaccurate.  Sure, if we were to restrict the question to nations in North
America, it would be true, but it is not the complete answer.

Okay, for perhaps a better analogy, we could have answered "Imperial Rome".
That might have been true at one time (have forgotten most of my early
Chinese history, but I think during at least some of the early centuries AD
China was divided into several smaller nation states, so I think the
Imperium may have been larger) but we shouldn't ignore the rest of history
unless specifically requested.

Now, on to some specifics.
At 08:18 PM 5/26/99 -0700, Frank Galef wrote:
>Since when was there any question that dino-groupies couldn't be included?

If you note, my comment was "...if all you are interested in is a chat room
for "dino-groupies"".  I never said that amateur dinosaur enthusiasts
weren't welcome!  I DID suggest that this isn't just a chat room: it is a
list serve specifically built for the discussion of dinosaur science.  Of
course people other the dinosaur scientists are welcome, and do most of the
postings.  However, the postings should try to be scientifically accurate.
Furthermore, if others try and correct scientific mistakes (as T. Mike
Keesey and others did to the original poster, and I saw nothing
mean-spirited about their comments), you should take that in good spirits as
part of the self-correcting nature of science.

>Who is this List for anyhow?  Big hint:  those of us who don't have
subscriptions to
>all the journals where the original papers come out, along with those who do.

Agreed.  However, it is for the discussion of dinosaur science, so we should
try as much as possible to keep it scientifically accurate.

>I agree that
>I haven't seen too many refer to dinosaurs as "extinct avians", but those
who do
>are rather strident,

Okay, here's a time to be scientific.  I posted the two authors (Olshevsky
and Patterson) who have expanded Aves to include taxa outside the_
Archaeopteryx_-neornithine clade.  Can you name another, and can you show
that this individual or individuals have been rather strident about it?  (I
can think of a third: he has posted on this list, but has never been
particularly strident about such usage).

There is a big difference in calling _Megalosaurus_ or _Iguanodon_ "extinct
avians" (something very few would do) and in calling them "non-avian
dinosaurs" (something a lot more common).

>while even ignoring all of the dinosaurs that had nothing to
>do with the lineage that led to birds.

I admit that bird origins has deflected interest in what I think are more
fascinating subjects.  I admit (hell, I had a paper at the Ostrom Symposium
on the subject!) that some people are more interested in tracing the origin
of avian characters rather than the distributions of all the shared derived
characters within coelurosaurs (note that these are two different issues,
and if you dealing with a taxon with a lot of homoplasy... oh, well, read
the paper when it comes out... :-).

>On the other hand, those who "love" to
>call our prehistoric faves "non-avian dinosaurs" do include some prominent
names
>in the field.  I can't get through any publication from the American
Museum, much
>less their fourth floor, without getting beaten over the head repeatedly
with that
>appellation.

Yeah.  Maybe there's a reason to it.  Maybe the AMNH is trying to do part of
its charter and educate.  Maybe they are trying to expand the public's
knowledge and understanding of the tree of life.

>Considering the diversity  of extant mammals, should we be *precise* by calling
>ourselves non-rodent, non-chiropteran placentals?

Yes, it would.  However, it would emphasize how unnatural such an assemblage
is: why arbitrarily exclude the two most diverse clades of placentals?

By the same token, the use of the phrase "non-avian dinosaurs" emphasizes
the unnatural-ness of the traditional view of Dinosauria.  By excluding the
feathered fliers arbitrarily we are missing a huge chunk of dinosaurian
diversity.  It would be equally unnatural to concentrate on "non-plateosaur
dinosaurs" or "non-pachycephalosaur dinosaurs".

>Scientific precision can get a
>bit long-winded.  I do realize that there is a spectrum of changes that
leads from
>what we might unequivocally call a dinosaur to what can be called a bird.

Indeed.

>Where
>in this sequence does the tail disappear get traded for a pygostyle,

Above _Archaeopteryx_, below Confuciusornithidae.

>and when does
>the semilunate fuse to the metacarpals?

Old story: above Confuciusornithidae, below alvarezsaurids (if birds) and
ornithothoracines.  This will change soon.

>Did maniraptor dinosaurs have a hinged maxilla (do all modern birds?)

Depending on the type of kinesis you are talking about, present in
alvarezsaurids, not certain in other birds outside of ornithothoracines.

>Are there enough distinctly bird features that
>modern Avians can be called dinosaur descendants  rather than dinosaurs?

Not any more than we can be called primate descendants rather than primates.

>I don't
>mind being told that the answer is no, but then how is criteria determined to
>separate these Classes?

Arbitrarily.  We've gone over that one topic a huge number of times on this
list.

In short form, though, although modern birds are clearly separated from all
other living animals by a huge number of specializations, the fossil record
reveals that these do not appear all at once.  Instead, they were acquired
sequentially at different stages in bird origins: some are broadly
distributed among various groups of theropods, others restricted to birds
and their immediate outgroups, still others do not appear until well after
the bird lineage had split off from their closest relatives and had been
diversifying themselves.

(And I'm not even going to TOUCH the "Classes" comment...).

>Frank, the Dino-groupie
>{I certainly do not want to denigrate the importance of pre-KT birds, and wish
>there was a lot more information available about them, but how popular
would this
>list be without the big scaley beasts?)

Well, despite the above, I AM more interested in groups of theropods other
than swell-headed, stump-tailed flying mutants.  However, as others have
already indicated, a cursory survey of the subject headings on the Archives
of the DML will reveal that a LOT of discussion on the list has been on
birds.  Sure, it would be great to get a good prosauropod or
heterodontosaurid or protoceratopsid discussion going, but that doesn't seem
to interest as many people here.  Wish it did, though...

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661