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Re: Steadman's review of Mesozoic Birds






From: "Mickey Mortimer" <Mickey_Mortimer111@msn.com>
Reply-To: Mickey_Mortimer111@msn.com
To: <dinosaur@usc.edu>
Subject: Re: Steadman's review of Mesozoic Birds
Date: Thu, 29 Jan 2004 20:05:53 -0800

John Pourtless wrote-

> I have watched and participated in this fracas for about a decade now.
And
> in that time I have abandoned the thecodont hypothesis to which I
previously
> held, but I remain deeply troubled by the tone of the debate amongst
> professionals and spectators such as myself.  The latest issues of The
Auk,
> long a journal near to my heart, have been riddled with childish vitriol
and
> accusation and counter-accusation of ineptitude, pseudo-science, and so
> forth.  Steadman in the entitled review refers to the debate in terms of
> blood spilled.  This is a pitiful state of affairs, and I blame both
parties
> for it.  It seems  that for every excess of the thecodont camp there is
some
> equal but opposite excess on the theropod/bird side, in some perverse
> mimicry of Newton's laws of motion.

I, of course, also see (and have participated in) this vitriol and
accusations of ineptitude and pseudoscience.  Yet to me it seems the
accusations are much more rightfully given by BADist than ABSRDists.  I
really can't see it any other way, even when trying to be objective.

> Yet what troubles me most deeply, is the way in which the paleontological
> community has taken to viewing and describing their paleornithological and
> ornithologist counterparts.


This is mostly why I replied, to make sure my statement "However, his review
also shows a lack of knowledge in Mesozoic taxa and cladistics (which might
be partially expected in a Cenozoic paleornithologist)" was not
misunderstood. It was not meant to belittle paleornithologists in any way.
I merely meant that Mesozoic Birds is on a topic outside Steadman's area of
expertise, so this could be seen as a reason for some of his
misunderstandings and probably inaccurate opinions.


> And moreover there is this idea that all
> debate should be ended on the origin of birds. Yet why should this be?
So
> long as data can be presented that reaches a different conclusion, we
should
> consider it and take it in stride. I would argue this is largely the very
> heart of science--the endless testing of even those concepts which seem
> beyond error. Falsification, as Prum noted in his 2003 rebuttal to
> Feduccia, is a central tenet of science, and that includes the ceasless
> attempt to falsify any given postulate, to uphold its validity or displays
> its flaws. It is for this reason that I feel the debate should and indeed
> must continue, no matter how certain the theropod origin of birds seems.
It
> will only benefit our understanding of avian evolution.


Yes, but the data that supposedly indicates a non-dinosaurian origin for
birds almost always does no such thing. The one exception I can think of is
the digit homology issue. Debate doesn't continue on the origins of
mammals, or tetrapods, or other taxa that are securely placed. Besides,
it's rather hard for ABSRDists to continue debating points that their new
MANIAC hypothesis contradicts. Dromaeosaurs aren't birdlike because... oh
wait, they are bird relatives, um... yeah. Note the three MANIAC-supporting
papers (Feduccia, 2002; Czerkas and Yuan, 2002; Czerkas et al., 2002) have
given no scientific reasons their hypothesis is better than bad, have been
contradictory, and have basically been unsure about any part of MANIAC
except for (1) birds aren't dinosaurs and (2) feathered taxa are birds. BAD
arguments have gone from "your data and conclusions are wrong" to "your
methodologies are wrong" to "you're not doing science anymore", and I can't
see any MANIAC causing anything other than the latter to continue.


> In a similar vein, though I very much agree with cladistic methodology and
> its principles, some researchers seem to categorically reject any
> ornithological and paleornithological work which contradicts some of the
> popular cladistic hypotheses about birds, both extinct and extant. Yet we
> have seen time and again that such skepticism is warranted. E.g.,
Cracraft
> has long defended the holophyly of the paleognathous assemblage, and yet
> there is little if any evidence to suggest as much. For this stance I
shall
> doubtless invoke the wrath of the mailing list, as my position will be
> misinterpreted as anti-cladism. It is nothing of the sort. I merley wish
> to indicate that cladistics, much like molecular systematics, is not the
> universal panacea for ornithological systematics.


I'm not going to call you an anti-cladist, I'm just confused what references
you're using for there being little evidence for non-monophyletic
paleognaths. It was my impression both morphological (eg. Livesay and Zusi,
2001) and molecular (eg. Garcia-Moreno et al., 2003) data have confirmed a
monophyletic Paleognathae for the last decade.


Mickey Mortimer

I agree that the vast majority of work by adherents of various thecodont hypotheses is rather poor, but I feel it poor from lack of factuality, not from some inherent flaw in the methodology or philosophy behind it.


As for the paleognaths...the neotenic nature of the paleognathous palate has been known since de Beer's 1956 work, and the case for the polyphyly of the paleognaths was considerably bolstered by Houde's 1988 work on Lithornithiformes. The molecular data, is at best problematic. While molecular systematics has some utility in ornithology, it appears to primarily reside at the subordinal level, as indicated by some glaring defecsts in commonly accepted molecular phylogenies (e.g., Sibley & Ahlquist's "tapestry"). The morphological data suggesting that Paleognathae is holophyletic, is equally dubious. Time and again we see characters advanced as synapomorphies of this assemblage to be plesiomorphic or neotenic. For instance, Cracraft & Clarke's (2000, IIRC) six "unambiguous synapomorphies" of Paleognathae, present just this sort of problem. There just seems to be irreconcilable problems with the view that Paleognathae represents a clade. The cautious route might be to draw an agnostic conclusion, but I feel the data supports the modernist consensus reached by Wetmore and his colleagues in the latter half of the 20th Century, that Paleognathae is a) polyphyletic, and b) secondarily derived from within Neognathae.

JGK

PS, Sorry Mickey for mailing this directly to you, forgot to change the address so it would go out to the mailing list!

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