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Re: Steadman's review of Mesozoic Birds
John Pourtless wrote-
I see it as a fundamental dichotomy between the morphological data on the
one hand, which strongly indicates that the paleognathous assemblage is
neotenic and reveals alleged synapomorphies to in fact be retained
plesiomorphies, and the molecular evidence which indicates that that group
is holophyletic. Clearly one set of data is incorrect, and given the very
real problems with molecular phylogenies of Neornithes, I think that
time-honored morphological approaches yield a more accurate representation
of paleognath phylogeny. Consider for instance the position of Aramidae
offered by Sibley & Ahlquist in their now famous "tapestry," which
contradicts nearly two centuries of morphological work (both cladistic and
otherwise). I think much the same has happened as regards the
I don't see how it can be such a dichotomy when all the morphological work
I've heard about in the last decade has supported a monophyletic
Paleognathae. Do you have any such references that support a
non-monophyletic Paleognathae? Are there any major problems with cladistic
molecular analyses of neornithines? Sibley and Ahlquist's was phenetic
after all. Still, even it seemed to get a lot of things "right".
At any rate, the difference is in the way in which phylogeny is
reconstructed, and I am quite sorry to say that despite the vast utility of
cladistic analysis, is not the solitary, immutable, flawless method for
phylogenetic reconstruction to the exclusion of all others. Simply because
a methodology is not cladistic, does not render it invalid.
Doesn't it though? I mean, some scientists may not like computerized
unweighted analyses of huge amounts of data, but even Feduccia groups taxa
by synapomorphies, does he not? It's not like anyone thinks phenetics is
As for the viability of the thecodont hypothesis...I do not not think it
viable, that much is obvious, but there is enough data to suggest that
perhaps, in some strange twist, it could be correct,
Is there enough? (I love rhetorical questions ;-) ) There's the manual
digit homology issue, and..... what? Everything else ABSRDists have used
seems to be either a factual error, hypocritical,
mis-understanding/representing BAD, irrelevent, or just plain unscientific.
Prum's 2002 and 2003 articles in The Auk bother for me one principal
reason, they propose (at least the former does) just as outlandish and
absurd a situation as Feduccia's cladistic conspiracy, basically, that
ornithologists are just too ignorant of paleontology to know the difference
between hollow rhetoric and real science.
I don't find it outlandish or absurd. If you're unfamiliar with a topic,
even statements of ABSRDist quality can sound viable. That's why I never
trust data outside my area of expertise (Mesozoic theropods) as much. When
reading papers on the whippomorph debate, I can't say "well, gene X is
notoriously poor at resolving relationships at that depth", or "he's right,
that sequence is misaligned", or "the fool, that clade of artiodactls has
no bearing on cetacean relationships". I just don't have the knowledge, and
I doubt ornithologists working with their hypotarsi, mesethmoids and syrinxs
have the appropriate knowledge of Mesozoic theropods. If what you guess is
true, and more ornithologists are ABSRD than BAD, this all but proves they
don't have the proper knowledge in my mind, because as you write, they
John Bridgman wrote-
I had been unavare that there were acronyms for each side of the
bird/dinosaur debate,(ABSRD,which apparently has become MANIAC,and BAD)It
would seem that I was once a member of ABSRD,but rather than change to
MANIAC,I have sided with BAD.
Yeah, it's great. And they're all negative too. :-)
BADD- Birds Are Dinosaur Descendants (for those BADists who don't like to
think in strictly monophyletic groups).
BAND- Birds Are Not Dinosaurs (a less amusing version of ABSRD, but one that
can be used to call proponents BANDits).
BCF- Birds Came First (Olshevsky's highly unparsimonious theory the BAD
topology is right, but that there was a central lineage of small quadrupedal
arboreal/scansorial taxa from the base of Archosauromorpha to Maniraptora).
And Steadman's boring and unneeded TB (Theropod - Bird) and NTAB
(Non-Theropod Archosaur - Bird).
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