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

RE: Problems with paedomorphic bird skull paper



Er... what he means by the consensus is the consensus of all examined taxa.  So 
he's saying the wireframes aren't supposed to be the real shape of the skull, 
but rather show how the skull is different from the average of all skulls 
examined.  I admit I've always thought the wireframes were supposed to 
represent the actual arrangement of landmarks so that you could overlay a photo 
and get a match.  Then the grid behind the wireframe would be equal sized 
squares for the consensus, and any warping shows how each skull's proportions 
changed.  But even if I'm wrong about that, there's still no way juvenile 
Alligator and Confuciusornis would differ from the consensus in such similar 
ways, and Confuciusornis's snout would differ from the consensus in the ways I 
outlined while LP-4450-IEI's would differ less, so my point still stands.

Mickey Mortimer

----------------------------------------
> Date: Mon, 23 Jul 2012 12:19:17 +0200
> From: david.marjanovic@gmx.at
> To: dinosaur@usc.edu
> Subject: Re: Problems with paedomorphic bird skull paper
>
> > Concerning the consensus, some quotations.
> >
> > Like other methods that uses superimposition, Thin-Plate Splines
> > (TPS) "uses" the consensus configuration for comparison and
> > quantification of shape changes purposes:
> >
> > "Consensus configuration - A single set of landmarks intended to
> > represent the central tendency of an observed sample for the
> > production of superimpositions, of a weight matrix, or some other
> > morphometric purpose. Often a consensus configuration is computed to
> > optimize some measure of fit to the full sample: in particular, the
> > Procrustes mean shape is computed to minimize the sum of squared
> > Procrustes distances from the the consensus landmarks to those of the
> > sample." http://life.bio.sunysb.edu/morph/glossary/gloss1.html
> > <http://life.bio.sunysb.edu/morph/glossary/gloss2.html>
>
> Yeah, exactly -- the sample size is 1 in both cases (GMV-2132 and
> LP-4450-IEI).
>
> (The sample size of alligators is probably greater; but Mickey isn't
> saying the alligator wireframe is wrong.)
>
> > Again, I've not deeply analyzed Mickey's post, just take a brief look
> > at the images but, in my humble opinion
>
> You don't have enough information to _form_ an opinion yet. Read the
> post -- it isn't long.