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RE: Mesozoic roots of parrots and passerine birds



  I used bootstrapping to attempt to assess the robusticity of the nodes to the 
matrix, but that was back then. I also attempted to actually attempt a PP using 
Bayesian inferences, but this was more limited; most of my work involved trying 
to get a functionally useful matrix (high sampling), and then bootstrapping it 
to determine matrix fitness. I no longer have the files in which I plugged the 
specimen in, including my own personal analysis.

  The jaw, to my recollection, never came out as a parrot, but that has more to 
do with the lack of affirmable parrot apomorphies, I think; as Dyke and Mayr 
said, much of the similarity is on the basic form of the jaw, resembling 
lories, but not in the particular constraints required of a basal psittaciform 
that has developed a lory-shaped jaw but is itself not a lory. I THINK Clarke 
put the specimen in a morph cladistic analysis, and this may be true of others, 
as well, and recall discussing the issue with both Clarke and Dyke (limitedly).

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


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> Date: Sat, 27 Aug 2011 17:56:39 -0300
> Subject: Re: Mesozoic roots of parrots and passerine birds
> From: augustoharo@gmail.com
> To: qi_leong@hotmail.com
> CC: dinosaur@usc.edu
>
> 2011/8/27 Jaime Headden <qi_leong@hotmail.com>:
> >
> >   There are, as was said earlier, cladistic analyses that may be tested to 
> > consider the jaw fragment. I've added the jaw in at one point to one large 
> > analysis WAY back when, but forgot the results; I've asked Mickey to plug 
> > the specimen in to some analyses, and I think Andrea Cau has plugged the 
> > specimen in to his mega-matrix. My understanding is that it comes out as a 
> > bird in virtually all results, and constraining it to a caenagnathid does 
> > increase the quality of the analysis otherwise, or at least pushes 
> > parsimony around by increasing the steps and decreasing posterior 
> > probability.
>
> Thanks for the data. Did it result to be a parrot in these analyses,
> or where there not enough number of birds? You speak of posterior
> probabilities, that makes me think you used some kind of Bayesian
> analysis instead of parsimony... Or do bootstrap/jackknife
> probabilities used in parsimony analysis represent posterior
> probabilities? I know little of Bayesian probabilities.
>
> >   As a biomechanically-inclined individual, however, phylogenetics is not 
> > the way I'd prefer to interpret the fossil initially, but rather by seeing 
> > whether extreme small size (the resulting animal would be smaller than 
> > *Caenagnathasia martinsoni*) will result in different jaw morphology in a 
> > related animal. If it is a super-dwarf caenagnathid, we may be seeing 
> > features that are related merely to that dwarfism. It may also be 
> > convergent on the conditions of caenagnathids and some particular avians, 
> > but be neither. It wouldn't even matter if it came from younger than the 
> > Lance and was somehow reworked into the Mesozoic as this should not 
> > influence its morphology or phylogeny.
> >
> Looks like a reasonable approach, but I think it may imply some ad hoc
> hypotheses, in the form of "ifs" (as "what if they are dwarf
> oviraptorids?"), and thus probably punished by parsimony in comparison
> with other hypotheses. Another good approach would be an ontogenetic
> one (admitting we have good representation of ontogenetic
> transformations in the case of toothless neotheropods with fused
> dentaries, and that the fossil is not juvenile).
>
> Besides, congrats for your prediction that the North Slope
> Pachyrrhinosaurus may have been another species!