[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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 paleognathous assemblage.

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 valid anymore.


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 aren't stupid.


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. :-)
Others include-
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).


Mickey Mortimer

_________________________________________________________________
There are now three new levels of MSN Hotmail Extra Storage! Learn more. http://join.msn.com/?pgmarket=en-us&page=hotmail/es2&ST=1