Re: Ostrom Symposium - Part I

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 10:02 PM 2/16/99 -0500, Ron "Okay, I guess I'll let someone else ask a
question, back make sure you bring the mike back to me :-)" Orenstein wrote:

>Well, I'm back from the Ostrom symposium and although I suspect that Tom
>Holtz will post a much more accurate and detailed report than I can hope to
>do,

We'll see: one of the things I managed to bring back with me is the flu, so
I've just been coming in to work to teach class the last couple of days.
(Wed. is my long day: historical geo lecture at 9, lab from 2 to 5, so I'll
see about posting mid-day).  I'll add some brief comments here.

Oh, and nice to meet Ron and others in person; good to see the old gang
again, too (a number of old ostromids showed up).

>Anyway, on to the symposium itself.  After an opening speech by John
>Ostrom, the festivities began with a talk by Jacques Gauthier entitled
>"What is a bird?".  This was a semantic discussion of whether we should be
>calling just the modern crown clade of birds "birds", and everything else
>by another name, or whether we should follow the pattern of almost any
>ornithologist who's thought about the matter and consider everything from
>Archaeopteryx on up to be a bird.

One aspect of this debate, too, is whether "bird" = Aves or "bird" =
Avialae.  Ah, nomenclature.

>He was  followed by Hans Dieter Sues, who had the rather peculiar task of
>describing alternatives to a theropod ancestry for birds -- peculiar, of
>course, because Sues favours the theropod ancestry theory.  He did so by
>running through a series of proposed alternatives and explaining why he
>didn't think they fit the bill.  These ran from the megalancosaurids,
>represented in the slides by Proterosaurus, which he dismissed as having no
>features whatever resembling Aves.

Actually, it was _Protorosaurus_, not _Proterosaurus_ (a different reptile).
In his recent restudy of the Protosauridae, it turns out that
_Megalancosaurus_ (and, I presume, _Drepanosaurus_, although I forgot to ask
him) are deeply nested within this clade.  Interesting.

>He also pointed out that the  fossil
>had seeds and ovules in its gut indicating that it was a plant eater, a
>perhaps unlikely scenario for a bird ancestor.  He moved on to Longisquama,
>which he also dismissed.  He pointed out that there was no clear evidence
>in Longisquama of an anterorbital fenestra,

Sues also pointed out how slight depressions on some of these forms were
indicated on some drawings as dashes, which later become solid lines in
later drawings, which later became unambiguously labeled as antorbital
fenestrae.  Once again, there is nothing as important in paleo as first hand
observation.

Will deal with the three non-avian theropod systematics talks (Sereno's,
myself, and Norell's) later today.  A lot of interest.  A LOT of agreement,
though, between these three authors and Phil Currie on an important aspect:

_Caudipteryx_ is most likely a basal oviraptorosaur, or very close to it;
Dromaeosaurids and (possibly) troodontids are closer to birds than to
oviraptorosaurs, and therizinosauroids are (in my own, Norell's, Sues', etc.
analyses) as close to birds as are oviraptorosaurs;
Therefore, the most recent common ancestor of dromaeosaurids,
oviraptorosaurs (and possibly troodontids and therizinosauroids) had arm and
tail feathers.

so, get used to the idea of feathered dromaeosaurids: the weight of
phylogenetic evidence clearly supports it, Jurassic Park notwithstanding...

Some highlights to look forward to in later posts: _Ichthyornis_ a
neornithine bird?!?, the pubic boot debate; and applause over Greg Paul's
cry of "What more could we possibly want?"...

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