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

Re: PDF-request: Original description of Lagosuchus and/or Marasuchus

David Peters wrote:

>No one is demanding anything, Bill. It's called enthusiastic encouragement. 
>(Come on >team!) The more workers creating answers the better. And yes, my hat 
>has been in the >ring and is in the ring at present.

Based on past messages you have sent to this list I did not get that
impression although I could be mistaken.

>To your point, if simply coding from the literature won't work this time it 
>means the literature >is not only wrong, it's >so< wrong that topology 
>tumbles. And now is a good time to remind >ourselves that the literature was 
>written from >first hand observation<.

It does not necessarily mean that the literature is wrong, just that
by your own first-hand observation you are directly testing the
hypothesis.  Remember not only is the literature written from >first
hand observation< (and this itself is a major assumption), but also
from the authors personal interpretation of that observation.  This
interpretation can and has often been influenced by factors such as
poor preservation, bias based on preconceived ideas, subjective
judgement of homology, misidentification, and sadly in some cases
deliberate deception. How often have people found that when they
examine a specimen specific details are constructed in plaster or some
other medium and the original author described it as real?

>So, what is your logic leaving us with? If first hand observation won't work 
>(see above), >plane tickets would be a waste of money. Right? Yes, it's a 
>vicious unwinnable Catch-22 >you are creating here.

No.  First hand observation is crucial.  For example regarding the
skull I am personally examining right now (and taking a break to write
this) I found pieces that have been missed by all previous workers and
fit directly on to the skull providing new information (and changing
my data matrix accordingly). This example is not unique.  Furthermore,
in this specific case the original author mentions the presence of a
fragmentary premaxilla but did not figure it; however, I cannot find
the element to verify the character states he proposed for this
element, do I include it if I cannot replicate the data?

There is absolutely no alternative for seeing the actual specimen. The
literature is a statement of hypothesis, nothing more, and is not
meant to be a replacement for the actual objects.  Mike Habib
explained this pretty well.

>I put my money on testing and taxon inclusion. Most systematic problems 
>written by recent >Triassic workers have arisen from a priori taxon gamut 
>assumptions that have never been >fully tested, as determined from testing 
>with a much larger unpublished gamut. Differing >observations of character 
>traits are only the final "sanding" of a structure that has (typically, >but 
>not always) already been built.

I find this statement somewhat snarky.  My (differing) interpretation
is that we have seen an overall expansion of taxa and characters being
added to these analyses (archosaur relationships) based on other
independent methods of relationship.  It is not as simple as putting
in every possible taxon and every conceivable character into PAUP* and
then taking the result as a robust hypothesis.  Sure the algorithm can
handle the large dataset and spits out a tree, but phylogentic
analysis is much more involved than data entry based on simple
observation.  The literature is full of discussion regarding aspects
of character construction, character set congruence, use of composite
vs. reductive codings, etc...  Characters are in constant need of
revision.  I agree that taxon sampling is of major importance (and
this has been supported in the literature), but adding taxa is also
something that needs to be done carefully given problems with 'missing
data', utilizing species vs. supra-specific terminals, etc.. As time
goes on we will see more expansion of datasets but this has to be very
carefully constructed so as to not avoid numerous potentially
misleading pitfalls surrounding the method.

>Let's just see what happens when the competing analyses come out (if they are 
>permitted >to come out).

What are you implying here? Rejection of manuscripts should never be
based on results but rather on flaws in methodology.  If your
methodology is sound and repeatable then it should be published no
matter if the results are unorthodox.

>After all, all cladograms are hypotheses.

No. A cladogram is something generated by an algorithmic program based
on what is entered.  A randomly typed binary code matrix will create a
tree when analyzed.  The hypothesis is the intepretation based on the
results that hopefully can be further supported using other
independent methods and/or other well-developed datasets and resultant

>Critics and fans alike will someday have their day.


>As a scientist, I'm happy when someone points out errors in my observations 
>and in my >matrices. That usually repairs a problem. I hope you feel the same 

I do, but I am also my own harshest critic.

I'll be honest here....I've interpreted the tone of some of your
messages as implying that you already know all of the answers, you are
just waiting for the rest of us to catch up.  This last message was no
exception and again, if you are the one who is questioning all
previous results, then you need to develop the alternative hypothesis
based on sound technique and repeatability.  You may be right, but
currently your criticisms and stated results are not testable thus not

On Sat, Apr 10, 2010 at 12:11 PM, Jaime Headden <qi_leong@hotmail.com> wrote:
>   >   So what I got from both Mike's and Bill's replies to your arguments 
> vis-à-vis >*Trialestes* was that 1) literature is not sufficient for some of 
> the information one might >want to question phylogenies, 2) much less 
> construct them, and that 3) simply having other >people do the work for you 
> is going to result in a lot of waiting time, meaning 4) it's often >better to 
> do the work that you need to have done yourself.