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Re: Prolacertiformes and Protorosauria



You know, I'm a little bothered that all this discussion of their
results doesn't ever bring up any of their character support one way
or another. I don't have the paper myself, and maybe no one else in
this conversation (with 1-2 exceptions) has read it either, perhaps?

Cheers,
Nick

On Sun, May 17, 2009 at 9:05 AM, David Peters <davidpeters@att.net> wrote:
>
> Yes, there is some intuition that goes into judging results.
> ie. placing mesosaurs with pareiasaurs = bad.
>
> More importantly, there is some experience at work here too. Yes, I've done 
> the larger, more inclusive study, that indicates the breaks are real and 
> taxon exclusion is the culprit.
>
> As for your 'by definition' comment, yes. True. Even so, 'by default' is also 
> at work here. The authors were working from too large a gamut and too small 
> of an inclusion group to make sense. There are better sister taxa out there. 
> The larger study would have revealed this.
>
> David Peters
> davidpeters@att.net
>
>
> --- On Sat, 5/16/09, Mike Habib <habib@jhmi.edu> wrote:
>
>> From: Mike Habib <habib@jhmi.edu>
>> Subject: Re: Prolacertiformes and Protorosauria
>> To: davidpeters@att.net
>> Cc: "dinosaur mailing list" <dinosaur@usc.edu>
>> Date: Saturday, May 16, 2009, 10:44 AM
>> David Peters wrote:
>>
>> > Once again, if sister taxa don't bear a family
>> resemblance, you have to doubt the results.
>>
>> Wait - I'm confused: don't the sister taxa bear
>> "family resemblance" *by definition*?  The tree
>> constructs the best estimate of ancestry, using some kind of
>> estimate of family resemblance.  For morphological character
>> sets, this usually means using a parsimony algorithm, with
>> is optimizing the distribution of characters and using
>> synapomorphies to define clades.  Since you're joining
>> taxa using shared derived character states, they *must* bear
>> resemblance.  The fact that those taxa may have some kind of
>> qualitative or intuitive lack of "resemblance"
>> doesn't mean you screwed up.
>>
>>
>> > I added breaks at nodes that did either had closer
>> excluded sisters or just plain did not make sense. Without
>> an overall understanding of amniote relations, studies such
>> as this one, undertaking such a huge gamut with too few real
>> sisters will bear little real results.
>>
>> How do you determine which groupings make sense - isn't
>> that the point of constructing the tree in the first place?
>> What's a "real sister"?
>>
>> Cheers,
>>
>> --Mike
>>
>>
>>
>> Michael Habib, M.S.
>> PhD. Candidate
>> Center for Functional Anatomy and Evolution
>> Johns Hopkins School of Medicine
>> 1830 E. Monument Street
>> Baltimore, MD 21205
>> (443) 280-0181
>> habib@jhmi.edu
>