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Re: Mesozoic roots of parrots and passerine birds



2011/8/28 Jaime Headden <qi_leong@hotmail.com>:
>
>   It was my interest when it came out to plug this into several large avian 
> morph matrices. Problematically, those matrices do not include the diversity 
> of sampling nonavian dinosaurs that would be required. There simply isn't an 
> analysis that covers both bases, because for the most part, there needn't be 
> at this time. Obviously, a super-sized matrix sampling all of the stem of 
> *Aves* and many members of *Aves* itself would be grand (using the 
> crown=total clade definition for that taxon), and the only reasonable way to 
> test it. Otherwise, I'd use Cau and Mortimer's various matrices for their 
> sampling size when it comes to nonavialaean theropods and avialaeans 
> separately to test one aspect. Combining the two would be a project I do not 
> think any one group could attempt, and would have to be done by greatly 
> expanding and sampling one of these to include the data in the other. I do 
> not have the time or the means to do this, so will choose instead to run the 
> basic analyses.

You are right. I was thinking that a relatively less difficult way to
circumvent the problem may be to include in Cau's megamatrix a few
basal parrots (not necessarily the earliest ones), and some few
non-parrot modern birds (including, say, a basal tinamou, a basal
galloanserine, etc.), adding enough characters to keep the monophyly
of the modern birds (as well as the relationships with the non-crown
group birds most favoured by large matrices), and the characters
uniting parrots, overall those on the lower jaw included by Stidham.
Of course a greater sample of modern birds would be desirable, but I
do not find reasons by which to think that an analysis with the
modifications I proposed would be worst than an analysis of Cau's
megamatrix without parrots at all.
If we fear that greater sampling of parts of the tree increase the
possibility of convergence in these parts of the tree (for convergence
increases with taxon number), thus biasing the analysis in favour of
parrots, we may go the other way and grasp some modern bird megamatrix
and then add a few maniraptorans, including basal avialans and
oviraptorosaurs. If both matrices give a congruent placement (parrot,
basal avialan, or oviraptorosaur), then one may be confident in the
results.

Cheers,
Augusto.