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Re: where have all the etc.[Pharris]

David Peters (davidrpeters@earthlink.net) wrote:

<If I pick a study and you don't like it, we've both wasted our time.>

  If ones picks a study that receives immediate disagreement, it usually has a
reason. However, to forestall this anti-determinate stance, one can just look
at as many references possible as well as the material itself. The literature
is RICH on the taxa listed below:

<Youngina (four specimens, preferably, but I'll accept fewer)
 At least three genera within Choristodera
 Parasuchia (genera please) 
 Proterochampsidae - including  Proterochampsa, Chanaresuchus, Cerritosaurus,
Teraterpeton, Tropidosuchus and Lagerpeton
 All traditional basal Archosauriformes (genera only), and you can skip taxa
higher than Archosauria.>

  Why not do this yourself? Seriously, Dave is also0 the only one to even IMPLY
*Lagerpeton* is a proterochampsid, and this _a priori_ descision of testing on
taxa inclusion by others based on a topology recovered in one analysis
heretofore unseen and thus untestable by other workers, is merely a symptom of
other such arguments. Search various reference databases such as Google, Google
Scholar, even dinodata.net, on topics far and wide are easily available.
Triassic literature is getting MUCH better attention than Jurassic and non-end
Cretaceous literature, and since most of these taxa are from well-sampled
Triassic and Permian strata, there should be some pretty hefty sets of volumes
one can collect. Benton, Walker, Parrish, Lucas, Heckert and Long, etc. are all
good sources for starting here, but I am sure Dave knew this already.
WWW.palaeos.com is a good place to start, as is the Tree of Life pages, and as
always, Google and your friendly neighborhood university library. Geology-based
collections would be preferable if you have access.

  As for *Doswellia* ... David Dilkes is working on the osteology, and at last
report, was almost complete with it. Aside from Weems' initial (long)
discussion, the peculiar animal is receiving dissertation-level attention, so
there much be some pretty good things to say about it.

<and as an outgroup: Prolacerta + Protorosaurus>

  Instead of _a priori_ selecting an outgroup, one can just plug all taxa in as
equals and be LESS then generous in interpreting data. If one suspects a crack
might be a suture, err on the side of caution and mark "?" and not "special
suture - 1". One can discuss the feature and run the analysis with the feature
as "1" as well, to see if it affects the topology. One can also not run a
constraint in the matrix to get a particular set of taxa nesting in a
particular way. This is ... bad form. One can do it to shorten an analysis and
see if it affects a particular subgroup, or how one's matrix compares to
someone's topology, but on the whole, doing this to your own analysis as a
preference is rather biased. (This is a general rule of thumb and nothing about

<Let me know when you have something. I hope you'll think it is as important as
I do that we compare apples to apples. If you cannot find a comparable study,
then I'll accept the next best/worst one you can offer. Just choose one.>

  Better yet, get back to us when the analysis is done. First, not everyone
includes every taxon, even in well-sampled matrices on crocs, mammals,
dinosaurs, or birds. Matrices involving gene families often leave out what some
call key taxa in extant topologies, and thus there is always room for
expansion. Trying to get people to compare one's inclusions as the key to one's
recovery because maybe no one else did anything else, or didn't have to include
archosaurs in general and thus never worry about these key taxa as being
archosaurs (in other words, Dave's analysis) is usually not done on principle
because it leaves what can be considered very important taxa from a phylogeny.
Say, require that any group MUST include a concise selection of extant and/or
fossil taxa, when available; this condition would appear to exclude Dave's
analysis as it would reject the inclusion of characters supporting a group he
himself does not recognize (to say nothing of the analysis) as per his listed
statements. Is this _ethical_?

  And ... if this is a question of time ... worry not. Tom Holtz has been
adding theropods to matrices since 1992. Jacques Gauthier since 1984. Tom
finally broke over 500 published characters in his last analysis and the
largest dinosaur matrix to date, and that's just focusing on THEROPODS. Imagine
if he had the time, resources, and massage therapist with oculist to study all
dinosaurs. Chris Brochu on crocs since the mid-90's. Paul Sereno spends his
time being more magnanimous in his selections of groups, so must focus on one
or two at a time, yet his 1999 analysis, built on the published 1998 matrix,
had over 1000 characters total (many overlaps due to separate matrices). You
will always have time to "get it right," but these authors for the most part
have been at it and will continue to be so, as long as they can keep their eyes
focused in the work rooms!


Jaime A. Headden

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

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