RE: More on "Arbitrary" Paleontology

[WJT Mitchell <wjtm@midway.uchicago.edu>]

-----Original Message-----
From:   Thomas R. Holtz, Jr. [SMTP:th81@umail.umd.edu]
Sent:   Monday, June 07, 1999 6:06 AM
To:     wjtm@midway.uchicago.edu
Cc:     dinosaur@usc.edu
Subject:        RE: More on "Arbitrary" Paleontology

At 10:31 PM 6/6/99 -0400, Tom Mitchell wrote:

>Tom Mitchell:
>I can't wait.  So I hope you won't mind if I pose a naive question about
>monophyly.  What do you make of the period in the history of paleontology 
in
>which dinosaurs were not regarded as a single, coherent animal group, but
>two separate groups that are distantly related? (I've run across this in
>Ostrom and Wilford.  Also, "The Dinosauria" suggests that "the term 
dinosaur
>has a significant arbitrary component"). I gather that everyone 
(everyone?)
>now believes that this problem has been left behind, and that dinosaurs 
had
>a common ancestor.

Or, to be more precise, that all dinosaurs had a common ancestor which was
also a dinosaur.  (Man, it has been years since I used that formulaic
phrase: too long have I been writing and speaking in PT... :-)

>How firm is this consensus?

Extraordinarily.  (Of course, with Phylogenetic Taxonomy, the ancestor of
_Triceratops_ and Neornithes is by definition a dinosaur, so it is
essentially a moot point.  Nevertheless, it would take some amazingly
bizarre and spectacular specimens to demonstrate that (for example)
Crocodylia or Parasuchia or Pterosauria or such were closer to Ornithischia
(for example) than to Saurischia.)

>What is at stake in it?

Not too much, actually.  The folks who revived the idea of dinosaurian
monophyly in the 1970s (Galton, Bakker, Bonaparte) have sufficient enough
other contributions to the field so that their careers are not bound up in
its validity, if that is the sort of question you are asking.

No, the career issue wasn't what I had in mind.  I have just been puzzled 
by how completely and quickly the consensus was achieved, when there are 
still these authoritative figures around talking as if the "dinosuar 
duality" hypothesis was the consensus for a rather long time. (Wilford and 
Ostrom still seem to believe in polyphyly).  It sounds as if dinosaur 
taxonomy went from polyphyly to monophyly very decisively in a relatively 
short time, without much fanfare.  Was this an issue that surfaced in the 
public circulation of paleontological "news," or pretty much an insider's 
affair?   So when I asked "what is at stake?" I meant: 1) What difference 
does it make to the practice of research whether monophyly or polyphyly is 
the prevailing consensus?  and 2) Does it make any difference at any other 
level--say, the public perception of dinosaur research?  Gregory Paul, for 
one, talks about the era of polyphyly as if it were the "dark ages" of 
dinosaurology.

Tom Mitchell